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ABSTRACT: The epidemiology and molecular characteristics of vancomycin-resistant enterococci (VRE) from China deserve further investigation. This study reports on the molecular characterization of 101 unique VRE (96 E. faecium and 5 E. faecalis strains) recovered from diverse samples of 12 hospitals in China. MIC results were obtained by reference broth microdilution methods, and vancomycin resistance and virulence genes were screened by polymerase chain reaction. All strains were subjected to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. E. faecalis exhibited vancomycin and teicoplanin MIC results at ≥256 μg/mL and harbored vanA, except for 1 vanB-carrying strain (MIC, 32 and 1 μg/mL, respectively). This strain had a unique PFGE pattern and was associated with ST410 (clonal complex [CC]4). E. faecium displayed vancomycin MIC values of ≥256 μg/mL with variable results for teicoplanin (1-256 μg/mL). One E. faecium had a teicoplanin MIC value of 1 μg/mL and carried a vanB, while the other 2 strains had teicoplanin MIC values of 4 and 8 μg/mL and harbored vanA. E. faecalis strains were susceptible to ampicillin, and all VRE displayed a susceptible phenotype to daptomycin, linezolid, and tigecycline. Four E. faecalis from a particular hospital were grouped within a single PFGE type and were associated with ST470 and ST471 (CC4), which are double- and triple-locus variants of ST410 and ST4, respectively. Overall, E. faecium displayed genetic variability, but clonal dissemination was noted within and among hospitals. All E. faecium belonged to STs associated with CC17, except for 1 strain (ST362; CC362). A total of 77.2% and 29.7% of all strains carried esp and hyl, respectively. In conclusion, these results show that vanA-carrying isolates predominated in strains from China, and E. faecium strains are usually associated with a common and human-adapted lineage (CC17). Unlike the majority of clinical E. faecalis (CC2 and CC9), strains included in this study showed ST profiles similar to ST4 (CC4), which has been associated with human infections in other Asia-Pacific countries.
Diagnostic microbiology and infectious disease 10/2012; · 2.45 Impact Factor
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Chunjiang Zhao, Hongli Sun,
Hui Wang,
Yudong Liu,
Bijie Hu,
Yunsong Yu,
Ziyong Sun,
Yunzhuo Chu,
Bin Cao,
Kang Liao,
Jin'e Lei,
Zhidong Hu,
Liyan Zhang,
Xiaobing Zhang,
Yingchun Xu,
Zhanwei Wang,
Minjun Chen
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ABSTRACT: A total of 5608 clinical isolates of Gram-positive bacteria were collected from 12 teaching hospitals across China from 2005 to 2010. The minimum inhibitory concentrations (MICs) of 19 antimicrobial agents were determined by the agar dilution method at the central laboratory. Overall, the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRSCoN) were 46.8% and 81.5%, respectively. Isolates from inpatients exhibited a higher rate of MRSA than that from outpatients (52.3% versus 26.2%, P < 0.001). The prevalence of MRSA in respiratory infections (67.5%) was higher than in other sources of infections (P < 0.001). A shift in vancomycin MICs from <0.5 to 1.0 μg/mL was observed during the 6-year period. In 2005, 70.5% of S. aureus isolates were inhibited at the vancomycin MIC of 0.5 μg/mL, while in 2010, 89% of the isolates were inhibited at the vancomycin MIC of 1 μg/mL. With the use of penicillin oral breakpoints, penicillin-resistant Streptococcus pneumoniae (PRSP) increased from 28.6% in 2005 to 59.5% in 2010 and varied among different age groups, with an average rate of 70.6% for children under 5 years old. Importantly, an obvious penicillin MIC right shift was observed from 0.032 to 4 μg/mL during the study period. Serotyping for the isolates from 2005 and 2010 indicated that the high rate of PRSP could be due to the increased prevalence of serogroup 19. The prevalence of vancomycin-resistant enterococci (VRE) increased from 0 in 2005 to 4.9% in 2010. Of the 27 VRE isolates, vanA gene was the most prevalent gene. During the study period, 97.9-100% of different species tested were susceptible to teicoplanin. Linezolid and tigecycline showed potent activities, and no resistant isolate was identified. In conclusion, although the prevalence of MRSA and MRSCoN remained stable over the 6 years, a sharp increase in the prevalence of PRSP was identified. In addition, MIC shifts, including the MICs of penicillin against S. pneumoniae and vancomycin against S. aureus, were observed. Continuous surveillance is warranted to evaluate the resistance trend of clinically important Gram-positive organisms in the future.
Diagnostic microbiology and infectious disease 04/2012; 73(2):174-81. · 2.45 Impact Factor
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Qiwen Yang,
Yingchun Xu,
Minjun Chen,
Hui Wang, Hongli Sun,
Yunjian Hu,
Rong Zhang,
Qiong Duan,
Chao Zhuo,
Bin Cao,
Yong Liu,
Yunsong Yu,
Ziyong Sun,
Yunzhuo Chu
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ABSTRACT: The aim of this study was to evaluate the in vitro activity of cefditoren and comparators against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis causing community-acquired respiratory tract infections (CARTIs). A total of 391 Streptococcus pneumoniae, 266 H. influenzae, and 76 M. catarrhalis were isolated from 10 centers located at 6 cities in China from January 2009 to May 2010. The microdilution method was used to determine minimum inhibitory concentrations (MICs). The pneumococci comprised 189 (48.3%) penicillin susceptible, 129 (33.0%) penicillin intermediate, and 73 (18.7%) penicillin resistant. Moxifloxacin and levofloxacin showed the highest activity (99.2% and 97.7%, respectively) against Streptococcus pneumoniae, followed by parenteral penicillin G (95.7%), cefditoren (83.1%) and amoxicillin-clavulanic acid (79.3%). Among the 266 H. influenzae isolates, 26 (9.8%) were ampicillin-resistant β-lactamase-producing strains and 24 (9.0%) were ampicillin-resistant β-lactamase-nonproducing strains (BLNAR). Most of antimicrobial agents demonstrated good activity (>97% susceptibility) against H. influenzae except ampicillin, cefuroxime, and cefaclor, which showed relatively lower activity (81.2%, 88.7%, and 88%, respectively). Cefditoren showed excellent activity with the lowest MIC(50) and MIC(90) (≤0.016/0.064 μg/mL) among all tested drugs, which is independent of β-lactamase production or ampicillin resistance. Cefditoren at a concentration of 0.5 μg/mL inhibited all BLNAR strains. Seventy of 76 isolates of M. catarrhalis produced β-lactamase. Cefditoren also showed excellent activity with MIC(90) of 0.064 μg/mL against β-lactamase-nonproducing strains and 0.5 μg/mL against β-lactamase-producing strains. In conclusion, the excellent intrinsic activity of cefditoren suggests that it may be a good choice for the treatment of CARTIs caused by Streptococcus pneumoniae, H. influenzae, and M. catarrhalis in China, while the activity should be closely monitored.
Diagnostic microbiology and infectious disease 04/2012; 73(2):187-91. · 2.45 Impact Factor
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Hui Wang,
Minjun Chen,
Yingchun Xu, Hongli Sun,
Qiwen Yang,
Yunjian Hu,
Bin Cao,
Yunzhuo Chu,
Yong Liu,
Rong Zhang, [......],
Ziyong Sun,
Chao Zhuo,
Yuxing Ni,
Bijie Hu,
Thean Yen Tan,
Po-Ren Hsueh,
Jen-Hsien Wang,
Wen-Chien Ko,
Yen-Hsu Chen,
Hendro Wahjono
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ABSTRACT: A multicentre resistance surveillance study [Community-Acquired Respiratory Tract Infection Pathogen Surveillance (CARTIPS)] investigating the susceptibilities of 2963 clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae, meticillin-susceptible Staphylococcus aureus (MSSA) and Streptococcus spp. from Asia against 12 antimicrobial agents was undertaken from 2009 to 2010. Based on the breakpoints for oral penicillin V recommended by the Clinical and Laboratory Standards Institute, the prevalence of penicillin-non-susceptible S. pneumoniae (PNSSP) ranged from 46% to 100%. Azithromycin and clarithromycin exhibited variable resistance rates of 0-88% against S. pneumoniae, 0-57% against MSSA and 0-76.5% against Streptococcus spp. isolates. The prevalence of extended-spectrum β-lactamase-producing K. pneumoniae varied from 5.1% to 58.5%. β-Lactamase production rates amongst H. influenzae isolates ranged from 15% to 46.6% and amongst M. catarrhalis isolates from 90% to 100%. Amongst M. catarrhalis isolates, macrolide resistance and cefaclor resistance rates of 5.8% and 1.2%, respectively, were found, mainly in Mainland China. Levofloxacin resistance rates of 0-3.9% with a MIC(90) (minimum inhibitory concentration causing inhibition of 90% of isolates) of 1-2mg/L and moxifloxacin resistance rates of 0-1.7% with a MIC(90) of 0.125-0.5mg/L were found amongst PNSSP isolates. Moxifloxacin was very active against Streptococcus spp., H. influenzae and M. catarrhalis isolates, with MIC(90) values of 0.125-0.25, 0.032-0.5 and 0.064-0.125mg/L, respectively. These results from the CARTIPS study have confirmed some significant regional differences in the antimicrobial susceptibilities of S. pneumoniae, MSSA, K. pneumoniae, H. influenzae and Streptococcus spp. and emphasise the importance of antimicrobial surveillance programmes for guiding empirical therapy and for focusing interventional control of antimicrobial resistance in distinct geographic areas.
International journal of antimicrobial agents 08/2011; 38(5):376-83. · 3.03 Impact Factor
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ABSTRACT: The acute lethal toxicity of the extracted and purified gross alkaloids from Cynanchum komarovii has been demonstrated on the insect pest, Spodoptera litura. The toxic regression equation of the gross alkaloids for S. litura larvae was Y = -2.69701 + 0.78711X and the LC(50) value 2669.88 mg L(-1). The growth disruptions of S. litura caused by the alkaloids from C. komarovii were also evaluated. The rates of growth inhibition, malformation, developmental duration (from third instar to pupation), pupation and emergence inhibition of S. litura caused by the gross alkaloids at dose rates between 50 and 800 mg L(-1) were 30.13-91.71%, 0.00-20.00%, 12-72 h, 16.66-36.66% and 16.66-50.00%, respectively. The alkaloids caused the modification of the cuticular components of S. litura. The relative contents of cuticular lipids, proteins and chitins showed a 3.02-17.11% rise before exposure, followed by 2.29-12.96% and 0.75-4.13% declines 72 h after treatment with gross alkaloids with concentrations between 50 and 800 mg L(-1). Initial studies on the insecticidal properties of C. komarovii gross alkaloids indicate these to be very potent insect growth inhibitors.
Natural product research 07/2011; 26(10):903-12. · 1.01 Impact Factor
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Hui Wang,
Minjun Chen,
Yuxing Ni,
Yudong Liu, Hongli Sun,
Yunsong Yu,
Xiujuan Yu,
Yaning Mei,
Min Liu,
Ziyong Sun,
Yunzhuo Chu,
Zhidong Hu,
Xinhong Huang
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ABSTRACT: The Chinese Meropenem Surveillance Study (CMSS) programme was initiated in 2003 with the aim of monitoring the antimicrobial activity of broad-spectrum agents against nosocomial Gram-negative bacilli in China. From 2003 to 2008, a total of 3892 isolates were collected from 10 teaching hospitals. The minimum inhibitory concentrations (MICs) of 11 antimicrobial agents were determined by the agar dilution method. During the study period, a marked decrease in the susceptibility of Acinetobacter spp. to meropenem and imipenem was noticed, from 94.6% to 60.7% and from 92.5% to 62.1%, respectively. However, for Pseudomonas aeruginosa the susceptibility was relatively stable, with susceptibility rates of 86.2% to 76.0% for meropenem and 74.8% to 70.5% for imipenem. Meropenem and imipenem exhibited the highest activities against enterobacterial organisms, with ranges of MIC(90) values (MIC for 90% of the organisms) from 0.064mg/L to 0.25mg/L and 0.25 to 4mg/L, respectively. Except for Acinetobacter spp., the next most active agent against the majority of isolates was amikacin, with susceptibility ranging from 78.8% to 93.3%, followed by piperacillin/tazobactam (73.7% to 98.2%), cefoperazone/sulbactam (63.9% to 99.1%), cefepime (67.0% to 95.4%) and ceftazidime (54.5% to 93.3%). The percentage of isolates positive for extended-spectrum beta-lactamases among Escherichia coli, Klebsiella spp. and Proteus mirabilis ranged from 50.9% to 66.7%, 25.4% to 42.4% and 8.9% to 24.2%, respectively. These CMSS results have demonstrated increasing resistance of Acinetobacter spp. to carbapenems, resulting from the spread of highly resistant clones. Continued surveillance studies, including CMSS, as well as potent measures for controlling the spread of resistant clones are required.
International journal of antimicrobial agents 03/2010; 35(3):227-34. · 3.03 Impact Factor
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ABSTRACT: The resistance mechanism of 49 Enterobacteriaceae isolates with decreased susceptibility to carbapenems collected from 2004 to 2008 at 16 teaching hospitals in China was investigated. Moderate- to high-level carbapenem resistance in most isolates was more closely associated with loss or decreased expression of both major porins combined with production of AmpC or extended-spectrum beta-lactamase enzymes, while KPC-2, IMP-4, and IMP-8 carbapenemase production may lead to a low to moderate level of carbapenem resistance in Enterobacteriaceae in China.
Antimicrobial Agents and Chemotherapy 10/2009; 54(1):573-7. · 4.84 Impact Factor
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ABSTRACT: We investigated the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in China and determined the susceptibility of S. aureus to 26 antimicrobial agents, including ceftobiprole, linezolid, and tigecycline. A total of 798 isolates were collected and tested by agar dilution. The mean prevalence of MRSA was 50.4%, the highest in Shanghai (80.3%), followed by those in Beijing (55.5%) and Shenyang (50.0%). Only 4.2% to 12.6% of MRSA were susceptible to erythromycin, fluoroquinolones, gentamicin, and tetracycline. All isolates were susceptible to teicoplanin, vancomycin, linezolid, tigecycline, and ceftobiprole.
Diagnostic Microbiology and Infectious Disease 10/2008; 62(2):226-9. · 2.53 Impact Factor
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ABSTRACT: Carbapenem resistance in Acinetobacter spp. is an emerging problem in China. We investigated the molecular epidemiology and carbapenemase genes of 221 nonrepetitive imipenem-resistant clinical isolates of Acinetobacter spp. collected from 1999 to 2005 at 11 teaching hospitals in China. Genotyping by pulsed-field gel electrophoresis (PFGE) found 15 PFGE patterns. Of these, one (clone P) was identified at four hospitals in Beijing and another (clone A) at four geographically disparate cities. Most imipenem-resistant isolates exhibited high-level resistance to all beta-lactams and were only susceptible to colistin. bla(OXA-23)-like genes were found in 97.7% of isolates. Sequencing performed on 60 representative isolates confirmed the presence of the bla(OXA-23) carbapenemase gene. Analysis of the genetic context of bla(OXA-23) showed the presence of ISAba1 upstream of bla(OXA-23). All of the 187 A. baumannii isolates identified by amplified RNA gene restriction analysis carried a bla(OXA-51)-like oxacillinase gene, while this gene was absent from isolates of other species. Sequencing indicated the presence of bla(OXA-66) for 18 representative isolates. Seven isolates of one clone (clone T) carried the plasmid-mediated bla(OXA-58) carbapenemase gene, while one isolate of another clone (clone L) carried the bla(OXA-72) carbapenemase gene. Only 1 isolate of clone Q carried the bla(IMP-8) metallo-beta-lactamase gene, located in a class 1 integron. Of 221 isolates, 77.8% carried bla(PER-1)-like genes. Eleven different structures of class 1 integrons were detected, and most integrons carried genes mediating resistance to aminoglycosides, rifampin, and chloramphenicol. These findings indicated clonal spread of imipenem-resistant Acinetobacter spp. and wide dissemination of the OXA-23 carbapenemase in China.
Antimicrobial Agents and Chemotherapy 12/2007; 51(11):4022-8. · 4.84 Impact Factor
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ABSTRACT: The potential role of endogenous ryanodine receptor (RyR) in modulating Ca2+ handling in HEK293 cells is controversial. Using Fura2/AM, here we provide evidence that caffeine can induce Ca2+ release from inositol 1,4,5-trisphosphate receptor-sensitive stores and Ca2+ entry in early passage numbers of HEK293 cells, but not in late passage ones. Ryanodine blocks caffeine-mediated effect, whereas 4-chloro-m-cresol can mimic these effects. In contrast, an increase in cyclic AMP or activation of voltage-dependent Ca2+ channels does not induce detectable alteration in intracellular Ca2+. Importantly, immunoblotting and staining have revealed that endogenous RyR expression is more abundant in the early than in the late passage cells. Additionally, similar to carbachol, Ca2+ entry in response to caffeine is blocked by capacitative Ca2+ entry inhibitors. These results indicate that the endogenous RyR in HEK293 cells can function as Ca2+ release channels and mediate capacitative Ca2+ entry, but they may be reduced due to cell passage.
European Journal of Pharmacology 03/2005; 509(2-3):109-15. · 2.52 Impact Factor
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ABSTRACT: Arachidonic acid (AA) modulates intracellular Ca2+ signaling via Ca2+ release or/and Ca2+ entry. However, the mechanism underlies either process is unknown; nor is it clear as to whether the two processes are mechanistically linked. By using Fura2/AM, we found that AA induced mobilization of internal Ca2+ store and an increment in Ca2+, Mn2+ and Ba2+ influx in HEK293 cells. The AA-mediated Ca2+ signaling was not due to AA metabolites, and insensitive to capacitative Ca2+ entry inhibitors. Interestingly, isotetrandrine and Gd3+ inhibited both AA-induced Ca2+ release and Ca2+ entry in a concentration-dependent manner without affecting Ca2+ discharge caused by carbachol, caffeine, or thapsigargin. Additionally, similar pattern of inhibition was observed with tetracaine treatment. More importantly, the three compounds exhibited almost equal potent inhibition of AA-initiated Ca2+ release as well as Ca2+ influx. Therefore, this study, for the first time, provides evidence for a direct coupling between AA-mediated Ca2+ release and Ca2+ entry.
Prostaglandins & other lipid mediators 02/2005; 75(1-4):141-51. · 2.70 Impact Factor
