Distribution and phenotypic and genotypic detection of a metallo-β-lactamase, CphA, among bacteraemic Aeromonas isolates.
The objectives of the study were to investigate the distribution of cphA-related genes (cphA) encoding a CphA metallo-β-lactamase (MBL) among 51 consecutive Aeromonas blood isolates and to compare different phenotypic methods for detecting CphA. The presence of cphA was detected by PCR. Four phenotypic methods, the imipenem-EDTA combined disc test, imipenem-EDTA MBL Etest, agar dilution test and modified Hodge test (MHT), were used to detect imipenem susceptibility and MBL production. The results showed that 35 (69%) blood isolates had cphA. All (100%) of 16 Aeromonas aquariorum isolates and 12 Aeromonas veronii isolates, and 4 (80%) of 5 Aeromonas hydrophila isolates, carried cphA, but none of 15 Aeromonas caviae isolates did. With the standard inocula, irrespective of the presence or absence of cphA, all but one (50, 98%) isolates were susceptible to imipenem tested by disc diffusion, Etest and agar dilution (10(4) c.f.u. spot inocula), and did not exhibit MBL production by the imipenem-EDTA combined disc test and MBL Etest. By the agar dilution test using large inocula (10(7) c.f.u.), 34 (97%) of 35 cphA(+) isolates had imipenem MICs of ≥16 µg ml(-1), higher than the susceptible breakpoint (4 µg ml(-1)), and demonstrated positive results for the MHT, while one cphA(+) and all 17 cphA(-) isolates had imipenem MICs of ≤4 µg ml(-1). In conclusion, the distribution of cphA among aeromonads is species-specific, found in A. aquariorum, A. veronii and A. hydrophila, and the MHT may be a phenotypic screening test for CphA production.
Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.|National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Tainan, Taiwan, ROC.|Department of Graduate Institute of Clinical Medicine, National Cheng Kung University Medical College, Tainan, Taiwan, ROC.
Chi-Jung
CJ
Wu
Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.|Department of Graduate Institute of Clinical Medicine, National Cheng Kung University Medical College, Tainan, Taiwan, ROC.
Po-Lin
PL
Chen
Department of Medical Laboratory Science and Biotechnology, National Cheng Kung University, Tainan, Taiwan, ROC.
Jiunn-Jong
JJ
Wu
Department of Pathology, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.
Jing-Jou
JJ
Yan
Center for Infection Control, National Cheng Kung University Hospital, Tainan, Taiwan, ROC.|Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.
Chin-Chi
CC
Lee
Center for Infection Control, National Cheng Kung University Hospital, Tainan, Taiwan, ROC.|Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.
Hsin-Chun
HC
Lee
Center for Infection Control, National Cheng Kung University Hospital, Tainan, Taiwan, ROC.|Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.
Nan-Yao
NY
Lee
Center for Infection Control, National Cheng Kung University Hospital, Tainan, Taiwan, ROC.|Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.
Chia-Ming
CM
Chang
National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Tainan, Taiwan, ROC.
Yu-Tzu
YT
Lin
Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.
Yen-Cheng
YC
Chiu
Center for Infection Control, National Cheng Kung University Hospital, Tainan, Taiwan, ROC.|Department of Internal Medicine, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan, ROC.
Wen-Chien
WC
Ko
D000333:Aeromonas / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000382:microbiology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D047090:beta-Lactams; D001618:beta-Lactamases; C082063:cphA protein, Aeromonas hydrophila