TY - JOUR
T1 - Distribution and phenotypic and genotypic detection of a metallo-β-lactamase, CphA, among bacteraemic Aeromonas isolates
AU - Wu, Chi Jung
AU - Chen, Po Lin
AU - Wu, Jiunn Jong
AU - Yan, Jing Jou
AU - Lee, Chin Chi
AU - Lee, Hsin Chun
AU - Lee, Nan Yao
AU - Chang, Chia Ming
AU - Lin, Yu Tzu
AU - Chiu, Yen Cheng
AU - Ko, Wen Chien
PY - 2012/5
Y1 - 2012/5
N2 - 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 mg 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.
AB - 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 mg 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.
UR - http://www.scopus.com/inward/record.url?scp=84859869541&partnerID=8YFLogxK
U2 - 10.1099/jmm.0.038323-0
DO - 10.1099/jmm.0.038323-0
M3 - Article
C2 - 22322339
AN - SCOPUS:84859869541
SN - 0022-2615
VL - 61
SP - 712
EP - 719
JO - Journal of Medical Microbiology
JF - Journal of Medical Microbiology
IS - 5
ER -