María M. Tavío

Universidad de Las Palmas de Gran Canaria | ULPGC · Faculty of Health Sciences

Acholeplasma (A.) laidlawii is an opportunistic pathogen with the ability to disseminate resistance determinants to antibiotics; however, its resistance to macrolides has been less studied. The aim of the present study was to characterize the mechanisms responsible for the resistance to macrolides, tiamulin and lincomycin found in a strain of A. la...

The ability to form biofilms is a recognized trait of Stenotrophomonas maltophilia, but the extent of its clinical relevance is still unclear. The present multicenter prospective study (ANSELM) aims at investigating the association between biofilm formation and clinical outcomes of S. maltophilia infections. One hundred and nine isolates were colle...

Background: MDR bacterial infections are currently a serious problem for clinicians worldwide. Klebsiella pneumoniae and Enterobacter spp., among Enterobacteriaceae, and Pseudomonas aeruginosa, are part of the group of ESCAPE pathogens or bacteria that 'escape' from common antibacterial treatments. The lack of effectiveness of the first common lin...

Background: Mycoplasma (M.) hyopneumoniae, M. hyorhinis and M. hyosynoviae are significant pathogens for the porcine industry worldwide. The aim of the present study was to determine the antimicrobial susceptibility of six key antimicrobials (tylosin, tilmicosin, tylvalosin, lincomycin, tiamulin and valnemulin) routinely used for treating infectio...

Two moderately halophilic and psychrotolerant new Mycoplasma species were isolated from common cephalopods. Three strains were isolated in pure culture from two individual European flying squid (Todarodes sagittatus), and two individual octopuses (Octopus vulgaris). The strains showed optimal growth at 25 °C and a salinity of 3% (w/v) NaCl. Molecul...

Objectives: The aim of this study was to evaluate the role of residue 238 in CTX-M-15 and CTX-M-15(G238C) mutant with respect to carbapenems and various β-lactamase inhibitors. Methods: A CTX-M-15(G238C) laboratory mutant was generated by site-directed mutagenesis from CTX-M-15 enzyme by replacing glycine 238 with cysteine. Thiol titration and p...

Background Mollicutes detection can be cumbersome due to their slow growth in vitro. For this reason, the use of DNA based on generic molecular tests represents an alternative for rapid, sensitive and specific detection of these microorganism. For this reason, six previously described nucleic acid testing assays were compared to evaluate their abil...

Mycoplasma hyopneumoniae is involved in the porcine enzootic pneumonia and respiratory disease complex; therefore, the search for new treatment options that contribute to the control of this organism is relevant. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations of tylvalosin and 19 other antimicrobial agents agai...

Loop B is important for low-level quinolone resistance conferred by Qnr proteins. The role of individual amino acids within QnrS1 loop B in quinolone resistance and gyrase protection was assessed. qnrS1 and 11 qnrS1 alleles with site-directed Ala mutations in loop B were expressed in Escherichia coli BL21(DE3) and proteins were purified by affinity...

The mechanisms responsible for increase in ceftazidime MIC in two Escherichia coli in vitro selected mutants, Caz/20-1 and Caz/20-2, were studied. OmpF loss and overexpression of acrB, acrD, and acrF that were associated with acrR and marR mutations and sdiA overexpression, together with mutations A233T and I332V in FtSI (PBP3) resulted in ceftazid...

Objectives: The role of sdiA in the acquisition of low-level multidrug resistance (MDR) was analysed and compared with that of marA and soxS in two Escherichia coli clinical isolates and two in vitro-selected mutants. Methods: The mutants were developed by growth in lomefloxacin and ceftazidime. The sdiA, marA, soxS, ftsI, tolC and acrB gene transc...

The aim of the present study was to investigate the mechanism of quinolone and beta-lactam resistance in an isolate of Citrobacter freundii PC2/08 collected from sewage effluent from l'Aquila, Italy. QnrB-9 and bla(TEM-116 )were co-expressed in a large plasmid identified in C. freundi PC2/08 strain. Compared to TEM-1, TEM-116 showed two single muta...

The role of sdiA in the acquisition of low-level multidrug resistance (MDR) was analysed and compared with that of marA and soxS in two Escherichia coli clinical isolates and two in vitro-selected mutants. The mutants were developed by growth in lomefloxacin and ceftazidime. The sdiA, marA, soxS, ftsI, tolC and acrB gene transcript levels were dete...

Elevated levels of fluoroquinolone resistance are frequently found among Escherichia coli clinical isolates. This study investigated the antibiotic resistance mechanisms of strain NorE5, derived in vitro by exposing an E. coli clinical isolate, PS5, to two selection steps with increasing concentrations of norfloxacin. In addition to the amino acid...

In order to determine how widespread antibiotic resistance has become to standard treatments, the in vitro susceptibilities of 28 Mycoplasma agalactiae Spanish field isolates to 16 antimicrobial agents were determined using a broth microdilution method. The most effective antimicrobials based on minimum inhibitory concentration (MIC)(90) values wer...

A complex network of regulatory systems ensures a coordinated and effective response to different types of stress that can act on a bacterium. Bacterial stress response generates changes that influence efflux system and virulence factor expression. Thus, partial or total loss of pathogenicity islands in uropathogenic Escherichia coli can be induced...

MICs were determined for 15 antimicrobial agents against 37 Mycoplasma putrefaciens isolates. The most effective antimicrobial drug classes were the fluoroquinolones, the tetracyclines, the lincosamide lincomycin, and the macrolides. The susceptibility profile of the isolates correlated with the geographic origin. This is the first report of decrea...

The present work was undertaken to study the ability of ceftazidime and ceftibuten to selectin vitro Escherichia coli HB101 harboring bla(TEM-1) beta-lactamase gene. Minimum inhibitory concentrations (MICs) of ceftazidime and ceftibuten were increased by a factor of 32, overcoming in the case of ceftazidime the breakpoint for clinical resistance. O...

In vitro susceptibilities of 16 Mycoplasma mycoides subsp. mycoides large colony type field isolates to 15 antimicrobial agents were determined using a broth microdilution method. The most effective antimicrobials were fluoroquinolones, tetracyclines and macrolides, with MIC values under 2 microg/ml. Resistance to nalidixic acid, gentamicin, strept...

The effect of ciprofloxacin and two mar RAB inducers on the susceptibility to beta-lactam antibiotics in two AmpC beta-lactamase semi-constitutive producer Citrobacter freundii clinical isolates (the DM 1 and DM 2 strains) was studied. Possible changes in outer membrane protein expression, permeability to cephaloridine, active efflux, and hydrolyti...

An efficient over-expression system was developed for CTX-M-3 extended-spectrum-beta-lactamase. The recombinant enzyme was purified from 1 l of culture to yield 22 mg of pure enzyme. The N-terminal amino acid sequence was determined to be NH2-QTADVQ... Determination of kinetic parameters with the purified CTX-M-3 revealed efficient hydrolysis of pe...

The aim of this work was to determine whether diazepam could induce the multiple antibiotic resistance (Mar) phenotype in Klebsiella pneumoniae and Escherichia coli strains. The Mar phenotype is characterized by decreased susceptibility to multiple antibiotics due to the loss of porins and/or increased expression of active efflux systems. The effec...

The effect of salicylate, a marRAB inducer, on the resistance to beta-lactams was characterized in an AmpC beta-lactamase hyperproducer Morganella morganii clinical isolate (the M1 strain). Results were compared with those of the effect of salicylate in a wild-type M. morganii strain. Salicylate induced a decreased susceptibility to nalidixic acid,...

Ceftibuten is an oral third-generation cephalosporin active against a wide range of bacteria and shows an improved stability to hydrolysis by several beta-lactamases because of the carboxyethilidine moiety at position 7 of the ss-acyl side chain. The kinetic interactions between ceftibuten and active-site serine and metallo-ss-lactamases were inves...

Ten quinolone-resistant mutants of Citrobacter freundii, which were selected in vitro with fluoroquinolones from two clinical isolates, were studied. The parent isolates were susceptible to quinolones in spite of showing a single substitution in the GyrB (His-417 → Leu). No change was observed in the outer membrane proteins or in the lipopolysaccha...

Five quinolone-resistant strains were developed from a clinical Morganella morganii isolate (M1 strain) which was susceptible to nalidixic acid and fluoroquinolones. All five in vitro selected mutants showed diminished norfloxacin accumulation and two of them also decreased the expression of the AgO in the outer membrane lipopolysaccharide with res...

The interaction between tazobactam and several chromosome- and plasmid-encoded (TEM, SHV, PSE types) class A and C beta-lactamases was studied by spectrophotometry. Tazobactam behaved as a competitive inhibitor or inactivator able to restore in several cases the efficiency of piperacillin as a partner beta-lactam. A detailed kinetic analysis permit...

The use of 0.5% sodium dodecyl sulfate in polyacrylamide separation gels allowed the resolution in several bands of high-molecular-mass components in smooth lipopolysaccharide of bacterial outer membrane from Escherichia coli, Morganella morganii, Citrobacter freundii and Citrobacter diversus. With or without 0.1% SDS, however, such a result was no...

Eighteen quinolone-resistant isolates of Escherichia coli were selected by exposing ten clinical isolates to increasing concentrations of norfloxacin and lomefloxacin. The mutant isolates showed a multiple-antibiotic-resistance phenotype. All of them contained single mutations in gyrA consisting of the substitution of Ser-83→Leu ( n = 14), V...

The effect of fluoroquinolones in Citrobacter freundii strains that results in a decreased expression of cephalosporin-hydrolysing beta-lactamases was studied. Resistance to broad-spectrum cephalosporins and penicillins in two C. freundii clinical isolates was associated with moderate production of chromosomal AmpC-type-beta-lactamase in addition t...

Eighteen quinolone-resistant isolates of Escherichia coli were selected by exposing ten clinical isolates to increasing concentrations of norfloxacin and lomefloxacin. The mutant isolates showed a multiple-antibiotic-resistance phenotype. All of them contained single mutations in gyrA consisting of the substitution of Ser-83-->Leu (n = 14), Val (n...

The interaction between tazobactam and several chromosome-and plasmid-encoded (TEM, SHV, PSE types) class A and C β-lactamases was studied by spectrophotometry. Tazobactam behaved as a competitive inhibitor or inactivator able to restore in several cases the efficiency of piperacillin as a partner β-lactam. A detailed kinetic analysis permitted mea...

New fluoroquinolones against enterobacterial strains (Nuevas fluorquinolonas frente a cepas de enterobacterias). Revista Española de Microbiología Clínica. 1992; 7 (6): 281- 283 The in vitro activity of two new quinolones, ciprofloxacin and fleroxacin, against 207 enterobacterial clinical isolates was assessed by the determination of MIC in Mueller...