First national survey of antibiotic susceptibility of the Bacteroides fragilis group: emerging resistance to carbapenems in Argentina.
The antibiotic susceptibility rates of 363 clinical Bacteroides fragilis group isolates collected from 17 centers in Argentina during the period from 2006 to 2009 were as follows: piperacillin-tazobactam, 99%; ampicillin-sulbactam, 92%; cefoxitin, 72%; tigecycline, 100%; moxifloxacin, 91%; and clindamycin, 52%. No metronidazole resistance was detected in these isolates during this time period. Resistance to imipenem, doripenem, and ertapenem was observed in 1.1%, 1.6%, and 2.3% of B. fragilis group strains, respectively. B. fragilis species showed a resistance profile of 1.5% to imipenem, 1.9% to doripenem, and 2.4% to ertapenem. This is the first report of carbapenem resistance in Argentina. The cfiA gene was present in 8 out of 23 isolates, all of them belonging to the B. fragilis species and displaying reduced susceptibility or resistance to carbapenems (MICs ≥ 4 μg/ml). Three out of eight cfiA-positive isolates were fully resistant to carbapenems, while 5 out of 8 isolates showed low-level resistance (MICs, 4 to 8 μg/ml). The inhibition by EDTA was a good predictor of the presence of metallo-β-lactamases in the fully resistant B. fragilis strains, but discrepant results were observed for low-level resistant isolates. B. fragilis was more susceptible to antimicrobial agents than other Bacteroides species. Bacteroides vulgatus species was the most resistant to ampicillin-sulbactam and piperacillin-tazobactam, and B. thetaiotaomicron/ovatus strains showed the highest level of resistance to carbapenems, with an unknown resistance mechanism. B. vulgatus and the uncommon non-Bacteroides fragilis species were the most resistant to moxifloxacin, showing an overall resistance rate of 15.1%.
Subcomisión de Bacterias Anaerobias, SADEBAC, Asociación Argentina de Microbiología, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina. lfcanigia@labdl.com.ar
Liliana
L
Fernández-Canigia
Mirta
M
Litterio
María C
MC
Legaria
Liliana
L
Castello
Silvia C
SC
Predari
Ana
A
Di Martino
Adelaida
A
Rossetti
Raquel
R
Rollet
Graciela
G
Carloni
Hebe
H
Bianchini
Daniela
D
Cejas
Marcela
M
Radice
Gabriel
G
Gutkind
D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D001118:Argentina / Q000453:epidemiology; D001426:Bacterial Proteins / Q000235:genetics; D001439:Bacteroides / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification; D001442:Bacteroides Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D001441:Bacteroides fragilis / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification; D001826:Body Fluids / Q000382:microbiology; D015780:Carbapenems / Q000008:administration & dosage*; D003430:Cross-Sectional Studies; D004492:Edetic Acid / Q000494:pharmacology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008826:Microbial Sensitivity Tests; D011159:Population Surveillance; D018440:beta-Lactam Resistance / Q000187:drug effects / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D004492:Edetic Acid; D001618:beta-Lactamases; C063912:carbapenemase