International Journal of Antimicrobial Agents

Published by Elsevier
Print ISSN: 0924-8579
This randomised, double-blind, multicentre trial compared piperacillin/tazobactam (2 g/0.5 g/q8h) and imipenem/cilastatin (0.5 g/0.5 g/q8h) as monotherapy in patients with acute pyelonephritis or complicated urinary tract infections. In total, 237 patients were randomised to receive either piperacillin/tazobactam (n=161) or imipenem/cilastatin (n=166). At the early follow-up (=test-of-cure-visit) 5-9 days after antibiotic therapy, clinical success was noted in 122/147 (83.0%) piperacillin/tazobactam recipients compared with 123/154 (79.9%) imipenem/cilastatin recipients, thus proving that both treatments were equally effective. On a descriptive level, an advantage of piperacillin/tazobactam was demonstrated. Microbiological success at the early follow-up was 78/135 (57.8%) for piperacillin/tazobactam and 70/144 (48.6%) for imipenem/cilastatin. These results were confirmed by equivalent success rates on the last therapy day. Both drugs were generally well tolerated.
LCB01-0062, a novel oxazolidinone, has potent antibacterial activity against clinical isolates of Gram-positive bacteria. The in vitro activity of LCB01-0062 was compared with that of linezolid, oxacillin, erythromycin, ciprofloxacin, vancomycin and quinupristin/dalfopristin. Among the tested agents, LCB01-0062 showed the most potent antibacterial activity against meticillin-resistant Staphylococcus aureus, meticillin-resistant coagulase-negative staphylococci and vancomycin-resistant enterococci. LCB01-0062 was 4-8-fold more active than linezolid, the first oxazolidinone drug, against Gram-positive bacteria. The time-kill curves of LCB01-0062 were analysed at concentrations of 0.5×, 1×, 2×, 4× and 8× the minimum inhibitory concentration against S. aureus strains. LCB01-0062 showed bacteriostatic activity during 24h. LCB01-0062 was also more effective than linezolid against S. aureus in a systemic mouse model of infection.
Herpes simplex virus type 2 (HSV-2) infections produce a recurrent disease state associated with susceptibility to other pathogens, including human immunodeficiency virus (HIV), and cannot be cured by current therapeutic treatments. The HSV-2 epidemic must therefore be addressed by therapeutic strategies that reduce recurrent lesions and ideally lack the possibility for development of drug resistance. To this end, the therapeutic potential of SCV-07 (gamma-D-glutamyl-L-tryptophan), a synthetic dipeptide with potent immunomodulatory and antimicrobial activity, was studied in the guinea pig model of recurrent genital HSV-2. Initial evaluations showed that when delivered orally, but not subcutaneously, SCV-07 significantly reduced recurrent lesions. Oral dose ranging studies indicated that, of the tested amounts, 5microg/kg was optimal when delivered after an overnight fast. Interestingly, fasting induced a significant increase in recurrent lesions in vehicle-treated guinea pigs relative to non-fasted animals. Despite this increase, SCV-07 significantly reduced lesion formation in treated animals but showed no durability following cessation of treatment. In fact, this regimen of SCV-07 treatment produced statistically indistinguishable outcomes compared with those provided by topical aciclovir. These data illustrate that SCV-07 may provide an easily administered alternative or supplemental treatment option for genital HSV-2 recurrent disease.
Antibiotics may cause an excess release of lipopolysaccharide (LPS) from bacteria and thereby promote the production of tumour necrosis factor (TNF). TNF was measured in the serum of Swiss mice challenged with filtered supernatant of Escherichia coli O7:K1 that had been exposed to various antibiotics in vitro. Expressed as a function of a standardized number of cells remaining after 6 h of exposure to gentamicin, ceftazidime, ciprofloxacin or imipenem, TNF leves associated with antibiotic exposure always exceeded those of controls. However, if differences in the remaining number of bacteria were not taken into account, TNF induction by supernatant of control untreated cultures was greater than that elicited by supernatant from any of the antibiotic-treated cultures. With the exception of imipenem, low-dose antibiotic exposure (0.5 x MIC) invariably induced higher TNF levels than did high-dose exposure (10 x MIC). Considerable antibiotic class- and concentration-related differences were noted. LAL equivalent amounts of LPS released by different antibiotics may diverge in their capacity to induce TNF. Our results do not support the notion that the use of rapidly bactericidal and lytic antibiotics should be avoided.
We tested ertapenem (MK-0826), a new carbapenem, and 13 other antimicrobials by microbroth dilution against 102 isolates of Streptococcus pneumoniae, selected to include organisms resistant to a variety of drug classes. Ertapenem MICs ranged from < or =0.008 to 4 mg/l, MIC(50)=0.5 mg/l, and MIC(90)=2 mg/l. Based on MIC(90), ertapenem potency was 4-fold greater than cefuroxime, 2-fold greater than amoxycillin/clavulanate, =penicillin, 2-fold less than meropenem and ceftriaxone, and 4-fold less than imipenem. Other drug classes including macrolides, tetracycline and fluoroquinolones were less potent overall than the carbapenems. Linezolid (MIC(90)=1 mg/l) was the only agent tested for which all isolates were fully susceptible. Activity of ertapenem decreased as MICs to penicillins, cephalosporins, other carbapenems and macrolides increased. Isolates resistant to clindamycin, tetracycline or fluoroquinolones showed no obvious decrease in ertapenem activity when compared with susceptible isolates with the majority of isolates resistant to these drug classes inhibited by ertapenem at concentrations less than 1 mg/l. Ertapenem may prove useful as an alternative to ceftriaxone and other agents in the treatment of community-acquired pneumonia (CAP) due to S. pneumoniae, including infections caused by organisms with reduced susceptibilities to other antimicrobial agents.
Several newer 6-fluoro/nitro-4-oxo-7-(sub)-4H-[1,3]thiazeto[3,2-a]quinoline-3-carboxylic acids (10-11a-q) were synthesised from 3,4-difluoro aniline and 3-fluoro-4-nitro aniline by nine-step synthesis. The compounds were evaluated for in vitro and in vivo antimycobacterial activities against Mycobacterium tuberculosis H37Rv (MTB), multidrug-resistant M. tuberculosis (MDR-TB) and Mycobacterium smegmatis (MC2) as well as being tested for their ability to inhibit the supercoiling activity of DNA gyrase from M. smegmatis. Among the synthesised compounds, 7-(1,4-dioxa-8-azaspiro[4.5]dec-8-yl)-6-nitro-4-oxo-4H-[1,3]thiazeto[3,2-a]quinoline-3-carboxylic acid (11l) was found to be the most active compound in vitro, with minimum inhibitory concentrations (MICs) of 0.09 microM and <0.09 microM against MTB and MTR-TB, respectively. Compound 11l was found to be 4 times and >506 times more potent than isoniazid against MTB and MDR-TB, respectively. In the in vivo animal model, 11l decreased the bacterial load in lung and spleen tissues by 30% and 42%, respectively, at a dose of 50 mg/kg body weight.
Eleven analogues of nifedipine (NP) showed synergistic interactions with ampicillin (Ap) and erythromycin (Er) on Escherichia coli K12LE140/F'lac. The antibacterial effect of Ap was enhanced by most analogues but compound (G9) and (+/-)-verapamil (VP) were antagonistic. Two of the 11 compounds (G7, G8) were synergistic with Er and four were additive. With a sensitive clinical isolate of E. coli Gy-1/Ap(sens)Er(res), compound G1 antagonized the antibacterial effect of Ap and a synergistic effect was found in the combination of Er with G4, G5, G6 or G7. None of the drugs had any effect on a multidrug resistant (MDR) clinical isolate of E. coli Gy-2/Ap(res)Er(res).
This multicentre, open-label, randomised trial compared meropenem (0.5 g/8 h) and imipenem/cilastatin (at the commonly used dosage of 0.5 g/6 h) in monotherapy in patients with moderately severe intra-abdominal infections (IAIs). In total, 161 patients were randomised (82 meropenem, 79 imipenem/cilastatin). The mean APACHE II scores in the two groups were 5.8 and 6.4, respectively. At the end of therapy, 65/71 (91.6%) evaluable meropenem recipients were clinically cured or improved, compared to 60/64 (93.8%) imipenem/cilastatin recipients. This difference and that in an intention-to-treat analysis (82.1 vs 86.1%, respectively), were not statistically significant. Both drugs were generally well tolerated. Thus, meropenem 0.5 g/8 h is as clinically effective and well tolerated as imipenem/cilastatin 0.5 g/6 h in moderately severe IAIs.
Fresh clinical isolates collected from November 1, 1992 through November 1, 1993, were tested by agar dilution against 26 different antimicrobial agents including FK037 and l-ofloxacin. Among the 10 040 organisms tested were Staphylococcus aureus (n = 1222), methicillin-resistant Staphylococcus aureus (MRSA, n = 455), Staphylococcus epidermidis (n = 533), Staphylococcus hominis (n = 90), Staphylococcus hemolyticus (n = 89), Streptococcus pneumoniae (n = 144), Escherichia coli (n = 2326), Klebsiella pneumoniae (n = 745), Enterobacter cloacae (n = 258), Proteus mirabilis (n = 445), Pseudomonas aeruginosa (n = 998), and Stenotrophomonas (Xanthomonas) maltophilia (n = 102). Both l-ofloxacin and FK037 inhibited 98% of S. aureus strains at 4 mug/ml. FK037 was at least 4 times more effective than the third generation cephalosporins against MRSA, inhibiting 79% of the strains at 16 mug/ml. While the potency of these agents looks promising, their clinical utility will depend in part upon the maximal dosage that can be safely administered.
This double-blind, double-dummy, parallel-group study was designed to show that a pharmacokinetically enhanced formulation of oral amoxycillin-clavulanate (16:1, 2000/125 mg), twice daily, is at least as effective clinically and microbiologically as oral amoxycillin-clavulanate 1000/125 mg, three times daily, in the 10 day treatment of community-acquired pneumonia (CAP) in adults. The pharmacokinetically enhanced formulation is designed to provide higher serum concentrations of amoxycillin for a longer period than standard dosing to achieve coverage of Streptococcus pneumoniae isolates with amoxycillin-clavulanic acid minimum inhibitory concentrations (MICs) up to and including 4 mg/l. A total of 344 patients with CAP from 77 centres received amoxycillin-clavulanate 2000/125 mg twice daily for 10 days (169 patients) or amoxycillin-clavulanate 1000/125 mg three times daily for 10 days (175 patients). The most common pathogen isolated was S. pneumoniae (52.3% of patients, amoxycillin-clavulanate 2000/125 mg group; 46.8% of patients, amoxycillin-clavulanate 1000/125 mg group). In the clinical per-protocol (PP) population at test of cure (days 18-39), the clinical success rate in the amoxycillin-clavulanate 2000/125 mg group was at least as good as in the amoxycillin-clavulanate 1000/125 mg group (91.5 and 93.0%, respectively; 95% CI, -8.3, 5.4). The radiological and bacteriological success rates at test of cure for the PP populations were 92.4 and 90.6% in the amoxycillin-clavulanate 2000/125 mg group and 93.9 and 84.4% in the amoxycillin-clavulanate 1000/125 mg group, respectively. The clinical, bacteriological and radiological success rates at the end of therapy (days 11-17) for the PP populations were all over 85%. Both regimens were well tolerated, with no differences in adverse events between the groups. Amoxycillin-clavulanate 2000/125 mg, twice daily, is well tolerated and at least as effective clinically as amoxycillin-clavulanate 1000/125 mg, three times daily, in patients with CAP and may also be appropriate for the treatment of infections due to S. pneumoniae strains with high-level penicillin resistance.
The pharmacokinetics and pharmacodynamics of levofloxacin in patients with respiratory infections such as community-acquired pneumonia (CAP) are poorly documented. This work aimed at assessing the pharmacodynamic target attainment against Streptococcus pneumoniae using levofloxacin 500 mg, 750 mg and 1000 mg administered once daily in plasma (P) and epithelial lining fluid (ELF) of hospitalized patients with community acquired pneumonia. The pharmacokinetics of levofloxacin in elderly (>/=65 years) compared with younger patients (<65 years) hospitalized with CAP were simulated. Susceptibility data with S. pneumoniae from our ongoing national surveillance study (Canadian Respiratory Organism Susceptibility Study-CROSS) were then used to produce pharmacodynamic indices of AUC(0-24)/MIC(all.) Monte Carlo simulations were then used to analyse target attainment of levofloxacin using doses of 500 mg, 750 mg and 1000 mg once daily to achieve free drug AUC(0-24)/MIC(all) >/= 30-100 versus S. pneumoniae in patients with CAP. Pharmacokinetics of levofloxacin simulated after 500 mg, 750 mg and 1000 mg once daily dosing resulted in levofloxacin volume of distribution: elderly patients = younger patients, while levofloxacin clearance was: elderly patients < younger patients. Levofloxacin t(1/2) values were longer in elderly patients (9.8 +/- 2.5h) than younger patients with CAP (7.4 +/- 2.5h). Free levofloxacin AUC(0-24) as well as AUC(0-24)/MIC(all) for S. pneumoniae were higher in elderly patients than younger patients. Monte Carlo simulation using levofloxacin 500 mg yielded probabilities of achieving free-drug AUC(0-24)/MIC(all) of 30 in P and ELF (95.7% and 98.1%) in elderly and younger patients (72.7% and 80.6%) respectively. Levofloxacin 750 mg and 1000 mg once daily had probability of achieving free-drug AUC(0-24)/MIC(all) of 30 in P/ELF of 98.1%/98.6% and 99.2%/99.0%, respectively, in elderly patients compared with 89.9%/94.1% and 95.2%/96.5%, respectively, for younger patients. Probability of achieving of AUC(0-24)/MIC(all) of 100 in P or ELF was very low in both patient populations at different doses except in the case of elderly patients receiving levofloxacin in a dose of 1000 mg once daily P/ELF of 78.5%/87.0%. We conclude that levofloxacin pharmacokinetics in elderly patients with CAP are markedly different from those of younger patients. Levofloxacin 750 mg OD provides high probabilities of achieving free-drug AUC(0-24)/MIC(all) of 30 in both plasma and epithelial lining fluid in patients with CAP including younger patients. Levofloxacin 500 mg OD provides high probabilities of achieving free-drug AUC(0-24)/MIC(all) of 30 in elderly patients with CAP, although we favour the 750 mg dosing in these patients as well. Levofloxacin 750 mg OD results in high probability of pharmacodynamic target attainment and improved bacteriological outcome against S. pneumoniae in patients with CAP.
The new extended-release formulation of ciprofloxacin (ciprofloxacin XR) was designed for once-daily administration in the treatment of urinary tract infection (UTI). The aim of this study was to compare concentrations in plasma, urinary excretion (UE) and pharmacokinetic parameters of ciprofloxacin XR (1000 mg) versus those of levofloxacin (500 mg) in healthy volunteers receiving a single oral dose. In this randomised crossover study, 12 volunteers (6 males, 6 females) received a single oral dose of 1000 mg ciprofloxacin XR or 500 mg levofloxacin to assess the concentrations (by high-pressure liquid chromatography) in plasma up to 32 h and the UE at intervals up to 36 h. The following pharmacokinetic parameters were studied: C(max), t(max), t(1/2), AUC(plasma0-->infinity), AUC(plasma0-->last), Cl(ren), maximal urinary concentration (U(max)), AUC(urine0-->last) and UE. Both fluoroquinolones were well tolerated. The plasma concentrations of levofloxacin were significantly higher than those of ciprofloxacin XR throughout the study period. The urinary concentrations of ciprofloxacin XR were significantly higher than those of levofloxacin in the first collection interval (0-4 h), whereas the concentrations of levofloxacin were significantly higher than those of ciprofloxacin XR in the five last collection intervals (12-36 h). The median proportions of cumulative renal excretion of the administered dose of the parent drug up to 36 h were 43.1% for ciprofloxacin XR (range, 13.7-50.8%; mean +/- standard deviation (S.D.), 40.5 +/- 9.9%) and 79.8% for levofloxacin (range, 74.0-88.2%; mean +/- S.D., 80.4 +/- 5.5%). C(max), AUC(plasma0-->infinity), AUC(plasma0-->last) and UE were statistically significantly higher in the levofloxacin than in the ciprofloxacin XR phase; t(max), Cl(ren) and U(max) were statistically significantly higher in the ciprofloxacin XR phase than in the levofloxacin phase; and AUC(urine0-->last) and t(1/2) were not statistically different. After an oral administration of ciprofloxacin XR 1000 mg and levofloxacin 500 mg, C(max) and AUC(plasma0-->infinity) were significantly higher in the levofloxacin phase. UE of ciprofloxacin XR 1000 mg once daily, however, was equivalent to that of levofloxacin 500 mg, and overall comparable urinary concentrations and AUC(urine) were reached by both drugs. Therefore, it can be assumed that the two doses investigated can be considered equivalent for the treatment of UTI.
Increasing resistance to fluoroquinolones in uropathogens has become a clinical concern. The purpose of this study was to analyse the urinary bactericidal activity (UBA) of levofloxacin against fluoroquinolone-resistant strains of Escherichia coli. Ten healthy adult subjects (aged 23-60 years) received single doses of levofloxacin (250, 500, 750 and 1000 mg) and then blood and urine samples were collected in intervals (0-1.5, 1.5-4, 4-8, 8-12 and 12-24h) over 24h. Both serum and urine concentrations were measured by a validated high-performance liquid chromatography assay. Bactericidal titres in urine were determined against E. coli isolates with minimum inhibitory concentrations of 0.125, 4, 8, 16, 32 and 64microg/mL for levofloxacin. The mean serum pharmacokinetic parameters for these doses of levofloxacin were similar to previously published values. The mean peak urinary concentrations (0-1.5h) were 210, 347, 620 and 536microg/mL for the 250, 500, 750 and 1000 mg dose, respectively. Each dose of levofloxacin exhibited early (0-1.5h time period) bactericidal activity in urine in virtually all subjects against E. coli strains with MICs<or=32microg/mL. Moreover, high-dose (750 mg and 1000 mg) levofloxacin provided prolonged (8-12h time period) bactericidal activity in 9/10 subjects against E. coli isolates with MICs up to 32microg/mL. In summary, this ex vivo investigation found that high-dose levofloxacin can produce early and prolonged UBA against fluoroquinolone-resistant strains of E. coli. Patient outcome studies are needed to determine whether these findings translate into clinical cures.
Streptococcus pyogenes is a common pathogen which may be associated with significant morbidity and mortality. Recent information is not readily available, in Canada, regarding the susceptibility of clinical isolates to penicillin, extended spectrum and/or newer agents. We collected and tested 1003 isolates of S. pyogenes to seven antimicrobial agents and found the following susceptibility rates: azithromycin 97%, ceftriaxone 100%, ciprofloxacin 99.4%, clarithromycin 98.5%, clindamycin 99.9%, erythromycin 96.5% and penicillin 100%. These results indicate that antimicrobial resistance is not yet a problem of S. pyogenes in Canada.
Two hundred and sixteen isolates of Streptococcus pneumoniae recovered between 1994 and 1996 from the middle ears of children with acute otitis media were tested for their susceptibility to penicillin, erythromycin, clindamycin and the oxazolidinones, linezolid (PNU-100766) and eperezolid (PNU-100592). There were 116 isolates from the Children's Hospital of Pittsburgh and 100 isolates from a national collection. Eighty percent of the local strains were susceptible to penicillin (MIC < 0.1 mg/l); 20% of the local strains and all of the national strains had reduced susceptibility to penicillin. All strains of S. pneumoniae tested had an MIC < 2.0 mg/l for both oxazolidinones. A regional difference was noted in the frequency of resistance to erythromycin with local isolates being more susceptible than isolates from the national collection. This difference was most pronounced among the high-level penicillin-resistant strains of S. pneumoniae.
CEM-101 is a novel fluorinated macrolide-ketolide with potent activity against bacterial pathogens that are susceptible or resistant to other macrolide-lincosamide-streptogramin B (MLS(B))-ketolide agents. CEM-101 is being developed for oral and parenteral use in moderate to moderately severe community-acquired bacterial pneumonia. The objective of this study was to assess the activity of CEM-101 and comparators against contemporary respiratory tract infection (RTI) isolates. A worldwide sample of organisms was used, including Streptococcus pneumoniae [n=168; 59.3% erythromycin-resistant and 18 multidrug-resistant (MDR) serogroup 19A strains], Moraxella catarrhalis (n=21; 11 beta-lactamase positive), Haemophilus influenzae (n=100; 48 beta-lactamase positive), Haemophilus parainfluenzae and Haemophilus haemolyticus (n=12), and Legionella pneumophila (n=30). Testing and interpretation were performed using reference Clinical and Laboratory Standards Institute methods. CEM-101 was very potent against S. pneumoniae [minimum inhibitory concentration for 90% of the organisms (MIC90)=0.25 mg/L; highest MIC at 0.5 mg/L] and was 2- and > or =32-fold more active than telithromycin and clindamycin, respectively. CEM-101 also demonstrated potent activity against S. pneumoniae MDR-19A strains (MIC90=0.5 mg/L). CEM-101 was the most potent antimicrobial agent tested against L. pneumophila, with all MIC values at < or = 0.015 mg/L (telithromycin MIC90=0.03 mg/L). CEM-101 was as potent as azithromycin against Haemophilus spp. RTI pathogens (MIC90=2 mg/L), with no variations for beta-lactamase production. CEM-101 MIC values against M. catarrhalis were all at < or =0.5mg/L. Interestingly, CEM-101 potency was ca. 6 log(2) dilutions greater than telithromycin MIC results among 44 beta-haemolytic streptococci having telithromycin MICs > or = 2 mg/L. CEM-101 exhibited the greatest potency and widest spectrum of activity against RTI pathogens among the tested MLS(B)-ketolide agents (azithromycin, clarithromycin, erythromycin, telithromycin, clindamycin and quinupristin/dalfopristin) and was comparable overall with levofloxacin.
Solithromycin (CEM-101) is a novel fluoroketolide with high potency against Gram-positive and Gram-negative bacteria commonly associated with community-acquired respiratory tract infections and skin and skin-structure infections. In this study, solithromycin and comparator antimicrobials were tested against a contemporary collection of Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus faecalis, Enterococcus faecium and other Enterococcus spp. collected in the SENTRY Antimicrobial Surveillance Program. Solithromycin was active against S. aureus [minimum inhibitory concentration for 50% of the organisms (MIC(50))=0.12 μg/mL] and was two-fold more active than telithromycin (MIC(50)=0.25 μg/mL). Solithromycin was more potent against methicillin (oxacillin)-susceptible S. aureus [MIC(50)=0.06 μg/mL and MIC for 90% of the organisms (MIC(90))=0.12 μg/mL) compared with methicillin (oxacillin)-resistant S. aureus (MIC(50)=0.12 μg/mL and MIC(90)>16 μg/mL). Solithromycin activity was reduced amongst heterogeneous vancomycin-intermediate S. aureus and vancomycin-resistant S. aureus (MIC(50)>16 μg/mL). Against strains with defined susceptibilities to erythromycin, clindamycin and telithromycin, solithromycin showed potent inhibition against all combinations (MIC(50)=0.06 μg/mL) except those with non-susceptibility to telithromycin (>2 μg/mL) (MIC(50)>16 μg/mL). The solithromycin MIC(50) for E. faecium (1 μg/mL) was four-fold higher than the MIC(50) for E. faecalis (0.25 μg/mL). In summary, solithromycin demonstrated high potency against many Staphylococcus and Enterococcus spp. isolated from contemporary infections worldwide.
One hundred and one cases of nosocomial meningitis in children from a national survey over 8 years have been analyzed for risk factors and outcome. From 101 cases, 115 organisms were isolated. Seventy six were Gram-positive bacteria, 29 were Gram-negative and there were ten fungal isolates. Major risk factors for acquisition of nosocomial meningitis were neurosurgery (70.2%), ventriculoperitoneal shunt (42.9%), prior therapy with broad spectrum antibiotics (64.1%), central venous catheter (94.5%), premature neonates with very low birth weight (32.8%) and total parenteral nutrition (68.8%). Overall attributable mortality was 14. 9%; in bacterial infection it was 13.2% and in fungal nosocomial meningitis, 30.0%. Higher mortality was significantly related to perinatal pathology with CNS abnormality, prematurity polymicrobial infection with Enterobacteriaceae and concomitant bacteraemia. Prematurity in neonates, very low birth weight and infection with Enterobacteriaceae were significantly associated with a worse outcome.
Twenty-five years after its introduction, ceftazidime remains the most active cephalosporin against Pseudomonas aeruginosa. Nevertheless, resistance arises by upregulation of AmpC beta-lactamase, by efflux or, less often, via acquisition of additional beta-lactamases. Mutational resistance is especially prevalent among cystic fibrosis (CF) isolates. We examined the activity of a novel oxyimino-aminothiazolyl cephalosporin, CXA-101 (FR264205), against P. aeruginosa strains with defined resistance mechanisms as well as against multiresistant clinical CF isolates of P. aeruginosa and Burkholderia cepacia. Minimum inhibitory concentrations (MICs) of CXA-101 were determined by the Clinical and Laboratory Standards Institute agar dilution method and were 0.25-0.5 mg/L for 'typical' P. aeruginosa strains without acquired resistance, compared with 1-2 mg/L for ceftazidime. MICs of CXA-101 were 0.5-2 mg/L and 4 mg/L, respectively, for isolates with upregulated efflux or total AmpC derepression, compared with 2-16 mg/L and 32-128 mg/L for ceftazidime. Full activity was retained against OprD mutants resistant to imipenem. Substantive resistance (MICs > or = 32 mg/L) arose for transconjugants with PER, VEB and OXA extended-spectrum beta-lactamases and for metallo-beta-lactamase producers, with reduced susceptibility (MIC = 8 mg/L) for transconjugants with OXA-2, OXA-3 and NPS-1 enzymes. MICs of CXA-101 were 2- to 16-fold below those of ceftazidime for multiresistant P. aeruginosa from CF patients, but ranged up to > 128 mg/L; values for B. cepacia from CF resembled those for ceftazidime.
The in vitro activity of Men 10700, a new penem, has been compared with that of metronidazole, clindamycin, ciprofloxacin, co-amoxiclav, imipenem and three third generation cephalosporins against 120 strains of anaerobes. The organisms tested comprised Clostridium perfringens, Clostridium difficile, Bacteroides fragilis and speciated members of the genera Fusobacterium, Veillonella and Peptostreptococcus. Men 10700 showed activity similar to that of imipenem, and was more potent than metronidazole against all species except C. difficile and P. anaerobius. The spectrum of activity of Men 10700 suggests this agent may be useful for treating infections caused by anaerobes.
The frequency of occurrence and antimicrobial susceptibility patterns of 3059 non-enteric Gram-negative bacilli (NGB), other than Pseudomonas aeruginosa and Acinetobacter spp., consecutively collected as part of the SENTRY Antimicrobial Surveillance Program (1997-2003) were reviewed. During this period, a total of 221,084 bacterial isolates were collected from several clinical specimens worldwide, including 25,305 (11.5%) NGB. Acinetobacter spp. and P. aeruginosa accounted for 82.7% of the NGB isolates and have been excluded from this analysis. The antimicrobial susceptibility results of 3509 strains from 13 species/genera have been analysed in this review. The isolates were tested by reference broth microdilution methods in three central laboratories using common reagents and procedures. More than 30 antimicrobial agents were tested and the results for the 18 most active compounds are reported here. Stenotrophomonas maltophilia (2076 strains; 59.2%) was the most frequently isolated pathogen in this group, followed by Aeromonas spp. (385 strain; 11.0%), Burkholderia cepacia (269 strains; 7.7%), Pseudomonas fluorescens/putida (253 strains; 7.2%) and Alcaligenes spp. (236 strains; 6.7%). All other species/genera accounted for less than 3% of the isolates analysed. The antimicrobial agents with the most consistent activity against the NGB evaluated in the present study were the newer fluoroquinolones gatifloxacin and levofloxacin with 84.1 and 84.9% susceptibility overall. Trimethoprim/sulphamethoxazole was active against 85.3% of the isolates tested, but showed reduced activity against P. fluorescens/putida (22.1% susceptibility). Antimicrobial susceptibility varied significantly between species/genera and the geographical regions evaluated. Thus, proper identification and quantitative susceptibility testing will be required for the treatment of NGB infections. Extensive worldwide surveillance programmes remain extremely important to guide empirical antimicrobial therapy for rarely isolated pathogens and also for pathogens that are not routinely tested due to the lack of standardised susceptibility testing methods.
A multi-laboratory re-evaluation protocol was initiated in 2001 to address broad-based concerns about the appropriateness of contemporary disk diffusion quality control (QC) guidelines of several antimicrobials in the tables of the M2-A7 standard of the National Committee for Clinical Laboratory Standards (NCCLS). This study that conformed to the NCCLS M23-A2 guideline demonstrates the dynamic processes that result in modification or development of these 11 QC zone diameter ranges. These changes included long-term QC problems for cefazolin (new range, 21-27 mm) and trimethoprim/sulphamethoxazole (new range, 23-29 mm) when tested against Escherichia coli ATCC 25922, and ticarcillin (new range, 21-27 mm) versus Pseudomonas aeruginosa ATCC 27853. All proposed ranges have been approved by the NCCLS for publication in M100-S12 tables in 2002.
The molecular mechanism of high level tetracycline resistance in T serotypes 4 and 11 group A streptococcal (GAS) isolates was examined in 61 tetracycline-resistant isolates in Japan. PCR and sequencing analyses revealed that the T serotype/emm genotype, T4/4 isolates carried tet(O) genes, which were genetically homogenous. The T11/11 and T11/89 isolates carried different subtypes of tet(M) genes, which were present on transposons Tn916 and Tn1545, respectively. In addition, these T11 isolates may have obtained the tet(M) gene after the 1990s, because resistance to tetracycline in T11 isolates was rarely found before then. These results strongly suggested that the T4 and T11 GAS isolates acquired tetracycline-resistance via different molecular mechanisms.
Among the 51 clinical isolates collected from a university hospital in Korea, nine isolates were resistant to cephamycins. Nine isolates were shown to produce CMY-11 and these also included three isolates producing TEM-1. The results from ERIC-PCR revealed that dissemination of CMY-11 was due to outbreaks of resistant species and to the intra-species spread of resistance to cephamycins in Korea. CMY-11 beta-lactamase genes from nine clinical isolates that were responsible for resistance to cephamycins (cefoxitin and cefotetan), amoxicillin, cephalothin and amoxicillin-clavulanic acid, were cloned and characterised. A sequence identical to the common regions in In6, In7 and a novel integron from pSAL-1 was found upstream from bla(CMY-11) gene at nucleotide 1-71. Eighteen nucleotides between position 71 and 72 were inserted into the bla(CMY-11) gene.
The antimicrobial susceptibility to beta-lactam and non-beta-lactam agents of 1100 isolates of Streptococcus pneumoniae recovered in 1997 from 16 centres in Argentina, Brazil, Chile, Mexico, Panama, Venezuela and West Indies was studied using E-test and disk diffusion methods. A total of 23.6% of isolates had raised penicillin MICs (16.7% intermediate and 6.9% resistant). The susceptibility of the other agents tested, from most active to least active, were, amoxycillin/clavulanate (99.5% susceptible); chloramphenicol (93.2%); cefotaxime (91.7%); erythromycin (87.1%); tetracycline (74.6%); trimethoprim/sulphamethoxazole (TMP-SMZ) (55.4%); and cefaclor (52.8%). The highest proportion of strains resistant to penicillin, chloramphenicol, erythromycin, tetracycline and TMP-SMZ was found in strains from Mexico while resistance to these agents was lowest in strains from the West Indies. Prevalence of penicillin resistance (including intermediate and resistant isolates) in each of the countries, from highest to lowest was, Mexico (40.8%); Chile (31.3%); Panama (23.0%); Venezuela (21.9%); Argentina (19.1%); Brazil (12.9%); and West Indies (7.1%). Based on current levels of antimicrobial resistance of S. pneumoniae in Latin American and Caribbean countries, continued surveillance efforts are necessary in order to guide clinical empiric treatment and provide for judicious use of antimicrobial agents.
Fluoroquinolone (FQ) resistance in Pseudomonas aeruginosa has spread. The purpose of this study was to investigate the correlation between representative FQ, i.e. levofloxacin (LVX), resistance and mutations in the gyrA and parC genes of P. aeruginosa clinical isolates from the urine of urinary tract infection patients and their rapid detection by denaturing high-performance liquid chromatography (DHPLC). The susceptibility to LVX of 114 clinical isolates was measured and the quinolone resistance-determining regions (QRDRs) in the gyrA and parC genes of these isolates were sequenced. DHPLC was undertaken to correlate the distinctive chromatograms with their DNA mutation patterns. Among 114 isolates tested, 22 isolates (19.3%) were resistant to LVX. Six amino acid mutations were detected (Thr83Ile, Asp87Tyr and Asp87Asn in gyrA and Ser87Leu, Ser87Trp and Glu91Arg in parC), existing alone or in combination. There were 10 kinds of mutation patterns. The presence of two or more kinds of mutation significantly correlated with LVX resistance compared with the wild-type or a single mutation (P<0.0001). DHPLC data identified the number of amino acid mutations with reproducibility distinguishable by peak number and profile of the DHPLC chromatogram. In conclusion, two or more mutations in gyrA and parC were significantly related to LVX resistance in P. aeruginosa. DHPLC facilitated the detection of resistant alleles, providing a rapid (5min per sample), economical (96 samples per run) and reliable technique for characterising LVX resistance in P. aeruginosa. This rapid detection system could forecast LVX resistance by the DHPLC profile.
Streptococcus pneumoniae isolates (n=1191) were collected during a 1997-1999 European surveillance study. In addition to susceptibility data, a molecular epidemiological survey of their mechanisms of resistance to macrolides, tetracyclines, and quinolones was provided. Of the isolates tested, 72.6% were penicillin-susceptible, 19.9% penicillin-intermediate and 7.5% penicillin-resistant. There was an obvious relationship between resistance to penicillin and resistance to erythromycin (19% of all isolates), clindamycin (14%) and tetracycline (23%). Only one isolate was resistant to levofloxacin. Seventy-three percent of the European S. pneumoniae isolates resistant to erythromycin (n=229) carried the erm(B) gene, while the remaining 27% possessed the mef(A) gene. No mutations were detected in 23S rRNA or in ribosomal proteins L4 and L22. All tetracycline-resistant isolates (n=277) carried the tet(M) gene; none carried the tet(O) gene. Classical mutations in gyrA (Ser 81-Phe or Tyr) and parC (Ser 79-Phe and Asp 83-Asn) and efflux contributed to the decreased quinolone susceptibility. This study of recent European S. pneumoniae isolates can be used to recognize any changes in susceptibility patterns and resistance mechanisms that may occur in the future.
Community-acquired pneumonia (CAP) is a common respiratory illness, frequently caused by Streptococcus pneumoniae. The prevalence of S. pneumoniae resistance to common antimicrobials has increased over recent years. A new pharmacokinetically enhanced formulation of amoxicillin/clavulanate (2000/125 mg) has been developed, designed to combat infections caused by S. pneumoniae, including penicillin-resistant (PRSP, penicillin minimum inhibitory concentrations (MICs) >or=2mg/l) isolates, and those with elevated amoxicillin/clavulanic acid MICs, while maintaining coverage of beta-lactamase-producing pathogens. A pooled efficacy analysis of four randomized (1:1) and one non-comparative clinical trials of amoxicillin/clavulanate, 2000/125 mg, given twice daily, was conducted in adult patients with CAP. Comparator agents were conventional amoxicillin/clavulanate formulations. At follow-up (days 16-39), efficacy (eradication of the initial pathogen or clinical cure in patients for whom no repeat culture was performed) in patients with S. pneumoniae infection was 92.3% (274/297) for amoxicillin/clavulanate, 2000/125 mg and 85.2% (46/54) for comparators (P=0.11). Twenty-four of 25 PRSP-infected patients receiving amoxicillin/clavulanate, 2000/125 mg were treated successfully. Both amoxicillin/clavulanate, 2000/125 mg and comparators were well tolerated, with few patients withdrawing from the studies.
The in vitro effect that the presence of components of non-specific immunity (serum plus polymorphonuclear neutrophils) has on the bactericidal activity of co-amoxiclav was explored against Streptococcus pneumoniae strains exhibiting an amoxicillin MIC > or =4 mg/L. Eight penicillin-resistant clinical isolates non-susceptible to co-amoxiclav with MICs of 4 (two strains), 8 (four strains) and 16 mg/L (two strains) were used. Values of MBC were identical to MIC values in all cases. Time-kill curves were performed with co-amoxiclav concentrations achievable in serum after a single oral dose administration of the new 2000/125 mg sustained-release formulation. Results were expressed as percentage of reduction of initial inocula after 3 h incubation. Control curves showed growth with no reduction of initial inocula. Against strains with MIC of 4 and 8 mg/L, the results obtained with the antibiotic alone or with the presence of factors of non-specific immunity were similar, with a weak combined effect due to the intrinsic activity of co-amoxiclav (reductions of initial inocula ranging from 70 to 99.16%). Against strains with MIC of 16 mg/L, the addition of PMN in the presence of serum increased the reduction of bacterial load provided by the aminopenicillin, even at sub-inhibitory concentrations (25.8% versus 51.1% at 0.5 x MIC concentration--8/0.5 mg/L). This combined activity against strains with an amoxicillin MIC of 16 mg/L which decreased the bacterial load may be important in preventing bacterial proliferation within the host and the transmission of resistant clones to others.
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During 1999-2000, 5015 isolates were collected from 13 countries and tested against levofloxacin. Overall, levofloxacin resistance minimum inhibitory concentration (MIC>or =8 mg/l) was found in 40 isolates (0.8%). The highest resistance rates were in Hong Kong (8.0%), China (3.3%) and Spain (1.6%). Levofloxacin retained an MIC(90) of 1 mg/l in all countries. Pulsed-field gel electrophoresis analysis of resistant isolates demonstrated the presence of clones in countries where levofloxacin resistance exceeded 1%, suggesting that the elevated resistance rates could result from resistant clones within participating hospitals. DNA-sequence analysis of the quinolone-resistance-determining regions of gyrA, gyrB, parC and parE genes showed that the most common mutations were in GyrA (Ser81Phe), ParC (Ser79Phe, Lys137Asn) and ParE (Ile460Val), accounting for 40% of the isolates tested. Levofloxacin-resistant isolates were generally non-susceptible to other fluoroquinolones tested. Future studies to characterise resistant isolates by other molecular methods may ensure that the appropriate counter-measures can be taken to control the spread of resistant isolates.
Ketolides are effective not only against macrolide-sensitive bacteria but also against some macrolide-resistant strains. Here we present data regarding a new ketolide with an alkyl-aryl side chain at C-13 of its lactone ring. It behaves as a strong inhibitor of protein synthesis in a model coupled transcription/translation system, although it does not affect the accuracy of translation. In addition, detailed kinetic analysis shows that it slowly forms a very tight, slowly reversible complex with prokaryotic ribosomes, a property that could be correlated with its superior activity compared with erythromycin against Escherichia coli both in vivo and in vitro.
Effect of different lipid compositions on calcein release from liposome vesicles by apomyoglobin 56–131 peptide. The small unilamellar vesicles (SUVs) were incubated for 5 min with different peptide concentrations and the percent of released calcein was determined spectrofluorimetrically, using SUVs disrupted with Triton X- 100 as a control of complete lysis. The control points (fluorescence adequate for 0 and 100% of lysis) were estimated individually for each composition of liposomes. (A) Leakage of calcein from SUVs formed from PC enriched with different amounts of cholesterol. (B) Leakage of calcein from SUVs formed from pure PC and / or PG. The estimated mean error of measurements was 3%. PC, dipalmitoyl phos- photidylcholine; PG, phosphatidyl glycerol. 
A, this effect is not large, but was significant even in a relatively low maximal amount of cholesterol (up to 33%). The results obtained agreed with another
The horse apomyoglobin 56-131 peptide is a convenient object for studies on the recently discovered antimicrobial activities of haem-binding protein fragments called haemocidins. The purpose of this study was to determine the effect of this peptide on planar lipid bilayer membranes and on liposomes of different lipid compositions. Micromolar concentrations of the apomyoglobin 56-131 fragment disrupt phosphatidylserine/phosphatidylethanolamine planar lipid bilayers without discrete conductance changes. The observed detergent-like action is dependent on peptide concentration; the lower amount of peptide resulted in longer bilayer lifetime. The cholesterol has an inhibitory effect on peptide-induced liposome lysis as shown by calcein release from liposomes. Additionally, there was considerable lytic activity on liposomes formed from anionic lipids of the sort found in bacterial membranes. Circular dichroism (CD) experiments showed that the peptide had a disordered structure in aqueous solutions and folds gradually to form helices in both membrane-mimetic trifluoroethanol solutions as well as in liposome suspensions. The features of the apomyoglobin 56-131 fragment that are similar to the cationic antimicrobial peptides acting in a 'carpet-like' manner are discussed.
The clonal composition of Escherichia coli causing extra-intestinal infections includes ST131 and other common uropathogenic clones. Drivers for the spread of these clones and risks for their acquisition have been difficult to define. In this study, molecular epidemiology was combined with clinical data from 182 patients enrolled in a case-control study of community-onset expanded-spectrum cephalosporin-resistant E. coli (ESC-R-EC) in Australia and New Zealand. Genetic analysis included antimicrobial resistance mechanisms, clonality by DiversiLab (rep-PCR) and multilocus sequence typing (MLST), and subtyping of ST131 by identification of polymorphisms in the fimH gene. The clonal composition of expanded-spectrum cephalosporin-susceptible E. coli and ESC-R-EC isolates differed, with six MLST clusters amongst susceptible isolates (median 7 isolates/cluster) and three clusters amongst resistant isolates, including 40 (45%) ST131 isolates. Population estimates indicate that ST131 comprises 8% of all E. coli within our population; the fluoroquinolone-susceptible H41 subclone comprised 4.5% and the H30 subclone comprised 3.5%. The H30 subclone comprised 39% of all ESC-R-EC and 41% of all fluoroquinolone-resistant E. coli within our population. Patients with ST131 were also more likely than those with non-ST131 isolates to present with an upper than lower urinary tract infection (RR=1.8, 95% CI 1.01-3.1). ST131 and the H30 subclone were predominant amongst ESC-R-EC but were infrequent amongst susceptible isolates where the H41 subclone was more prevalent. Within our population, the proportional contribution of ST131 to fluoroquinolone resistance is comparable with that of other regions. In contrast, the overall burden of ST131 is low by global standards. Copyright © 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.
During a survey of extended-spectrum beta-lactamases (ESBLs) in Bulgaria from 1996 to 2003, a TEM-3-like ESBL was detected in strains of Klebsiella pneumoniae, Escherichia coli, Citrobacter freundii and Klebsiella oxytoca from three centres in three different towns. The nucleotide sequence of the cloned gene was identical to that of TEM-3, except for one substitution (C347A) causing an amino acid exchange at position 49 from leucine to methionine. This TEM-3 variant with both a unique nucleotide and amino acid sequence was designated TEM-139. Transformants producing TEM-3 or TEM-139 expressed identical beta-lactam resistance phenotypes. TEM-139 was the only TEM-type ESBL detected in the surveyed hospitals (seven centres in three towns). TEM-139 is a natural variant of TEM-3 with an amino acid exchange without informational content, detectable only by molecular procedures, e.g. a nucleotide-specific polymerase chain reaction.
A total of 81 clinical isolates of the three clinically important Acinetobacter spp., namely Acinetobacterbaumannii, Acinetobacter genospecies 3 and Acinetobacter genospecies 13TU, were analysed for differences in carbapenem resistance genes. Of the 81 isolates, 40 (49%) were resistant to carbapenems. Most A. baumannii isolates (47/53, 88.7%) contained the ISAba1-bla(OXA-51)-like gene and exhibited a higher minimum inhibitory concentration to imipenem than A. baumannii without the ISAba1 element. All four carbapenem-resistant A. genospecies 3 isolates contained bla(IMP-1) and an ISAba3-bla(OXA-58)-like gene. Three A. genospecies 13TU isolates contained an ISAba3-bla(OXA-58)-like and either a bla(IMP-1) or a bla(VIM-11) gene. The five bla(IMP-1)-containing strains were resistant to imipenem and were positive for metallo-beta-lactamase (MBL) activity by the Etest, and the two bla(VIM-11)-containing strains were susceptible to imipenem and were MBL-negative by Etest. Imipenem hydrolysis tests showed that the bla(IMP-1)-containing strains exhibited much higher imipenem-hydrolysing activity than the two bla(VIM-11)-containing strains. No transcripts of bla(VIM-11) or bla(OXA-58)-like genes were detected. Analysis of outer membrane proteins showed that OprD was absent in the only bla(IMP-1)-containing A. genospecies 13TU strain owing to the presence of a premature stop codon in the oprD gene. In summary, several differences were detected between the carbapenem resistance genes of clinical Acinetobacter spp. in Taiwan, and loss of OprD may be associated with imipenem resistance in A. genospecies 13TU.
Patients with complicated infections may receive daptomycin for extended periods. This retrospective analysis was conducted to describe the safety profile of daptomycin in patients completing >14 days of therapy. In the Cubicin(®) Outcomes Registry and Experience (CORE(®)) 2005-2009, a retrospective, multicentre, observational registry, patients completing >14 days of daptomycin were studied. Investigators assessed adverse events (AEs) using ICH-E2A definitions of seriousness/severity ≤30 days after completing daptomycin. AEs were grouped by onset at ≤14, 15-28 and >28 days after starting daptomycin. In total, 2263 patients received >14 days of daptomycin. The most common indications were complicated skin and skin-structure infection (25.5%) and osteomyelitis (21.7%). Regarding AEs, 205 patients (9.1%) experienced AEs with an onset ≤14 days of therapy, 168 (7.4%) between 15-28 days and 108 (4.8%) >28 days; a total of 389/2263 patients experienced 814 AEs. The most common AE was increased blood creatine phosphokinase (CPK), occurring in 49 patients (2.2%) during ≤14 days of therapy, 32 (1.4%) between 15-28 days and 10 (0.4%) >28 days. In 183/2263 patients (8.1%), 264 AEs were possibly related to daptomycin. Serious AEs occurred in 153/2263 patients (6.8%). Eighty-nine (3.9%) of 2263 patients had daptomycin discontinued due to AEs, with 36 discontinued due to increased CPK. The overall mortality rate was 63/2263 (2.8%); 4 patients died of a possibly related AE. The most common AEs with onset <14 days were similar to those occurring between 15-28 days and >28 days. Daptomycin appears to be safe in patients treated for >14 days.
Although the efficacy of ceftriaxone in typhoid fever is well documented, the precise duration of ceftriaxone therapy in children with typhoid fever is not established and varies from 3 to 14 days in the literature. In a prospective, randomized study ceftriaxone was compared with chloramphenicol for treatment of 72 children who had bacteriologically confirmed typhoid fever. Ceftriaxone was given at a dose of 75 mg/kg per day (maximally 2 g/day) intravenously, in two doses until defervescence and continued 5 days after that time. Chloramphenicol was given at a dose of 75 mg/kg per day (maximally 2 g/day) in four doses for 14 days. Mean defervescence time was in 5.4 days in the ceftriaxone group and 4.2 days in the chloramphenicol group (P=0.04). Clinical cure without complications was achieved in all patients in both groups. No patient relapsed in the ceftriaxone group, and four patients relapsed in the chloramphenicol group (P=0.048). The overall results of this study suggest that a flexible-duration of ceftriaxone therapy given until defervescence time, followed by an additional 5 days of therapy is a reasonable alternative to conventional 14-day chloramphenicol treatment in children with typhoid fever.
The aim of this study was to evaluate the in vitro activities of voriconazole and fluconazole against Candida glabrata and Candida krusei isolated from blood during a 14-year period (1990-2003) at the tertiary care hospital of Cruces (Barakaldo, Spain). The in vitro activities of fluconazole and voriconazole against 28 isolates of C. glabrata and 15 isolates of C. krusei were determined by the Clinical and Laboratory Standards Institute disk diffusion method. Of the 28 C. glabrata isolates tested, 24 (85.7%) were susceptible (S) to fluconazole, 2 (7.1%) were susceptible dose-dependent (S-DD) and 2 (7.1%) were resistant (R). All C. krusei isolates were classified as R to fluconazole. Resistance to voriconazole was observed in one isolate each of C. glabrata (3.6%) and C. krusei (6.7%), and one isolate of each species was S-DD. These results were confirmed by the Sensititre YeastOne and Etest methods, with good comparative results. Voriconazole was very active in vitro against C. glabrata and C. krusei blood isolates and the resistance observed was not related to the introduction of voriconazole in the therapeutic schedule of the hospital. These facts support the usefulness of voriconazole as a therapeutic tool for candidaemia caused by these species.
Top-cited authors
Philippe Colson
  • Aix-Marseille Université
Wen-Chien Ko
  • National Cheng Kung University Hospital
Jean-Christophe Lagier
  • Aix-Marseille Université
Chih-Cheng Lai
  • Chi-Mei Medical Center
Andrew J Lamb
  • Robert Gordon University