SHV-28, an extended-spectrum beta-lactamase produced by a clinical isolate of Klebsiella pneumoniae in south India.

SHV-28, an extended spectrum beta-lactamase from a clinical isolate of Klebsiella pneumoniae , had an isoelectric point of 7.6 and a substrate profile showing preferential hydrolysis for cefotaxime over ceftazidime. It differed from SHV-1 by one amino acid substitution. The conserved S-T-F-K and K-T-G motifs were identified by SHV-28 protein sequencing.

Molecular characterization of nosocomial CTX-M type beta-lactamase producing Enterobacteriaceae from a tertiary care hospital in south India.

CTX-M group of extended spectrum beta lactamases (ESBLs) represents a rapidly emerging problem in many countries. The prevalence of nosocomial bla CTX-M-1 producing Enterobacteriaceae strains has not been reported earlier in Indian hospitals. This study describes molecular subtyping of nosocomial bla CTX-M producing strains of Enterobacteriaceae . Polymerase chain reaction with primers specific for bla CTX-M-1 coding genes was used to identify 95 Enterobacteriaceae strains producing bla CTX-M positive isolates. Of the 95 bla CTX-M producing isolates, 45 strains were positive for bla CTX-M-1 . bla CTX-M-1 was found to be most prevalent in Klebsiella strains.

Multiplex PCR for bla(CTX-M) & bla(SHV) in the extended spectrum beta lactamase (ESBL) producing gram-negative isolates.

BACKGROUND & OBJECTIVE: Phenotyping is commonly used for detection of extended spectrum beta lactamase (ESBL) production in gram-negative isolates. ESBLs are mainly coded for by three important genes, namely bla(TEM), bla(SHV) and bla(CTX-M). In this study we used a multiplex PCR as a rapid method to identify two common genes (bla(CTX-M) & bla(SHV)) responsible for extended spectrum beta lactamase production in members of Enterobacteriaceae family isolated from different clinical samples from a specialty hospital at Chennai. METHODS: A total of 260 non repetitive clinical isolates from 240 patients (some patients had more than one organism also), was selected for the study. Of these 33 were from sputum, 64 from urine, 46 from blood, 28 from pus aspirates, 58 from endotracheal secretions and 31 from other miscellaneous specimens. Phenotypic identification for ESBL production was confirmed by double disk synergy test (DDST) and phenotypic confirmatory double disk test (PCDDT) according to CLSI guidelines. Multiplex PCR for bla(CTX-M) and bla(SHV) was performed for the ESBL positive isolates. RESULTS: bla(SHV) like genes were found in 6 of 42 E.coli (14%), 7 of 46 Enterobacter species (15%), 28 of 62 Klebsiella species (45%) and bla(SHV) was not detected in any of the 50 isolates of non-fermenting gram-negative isolates. (Pseudomonas and Acinetobacter species) bla(CTX-M) like genes were found in 21 of 42 E. coli (50%), 13 of 46 Enterobacter species (28%), 25 of 62 (40%) Klebsiella species and 1 of 50 nonfermenting gram-negative bacilli (2%). INTERPRETATION & CONCLUSION: Our study demonstrated rapid detection of bla(SHV) and bla(CTX-M) in isolates belonging to Enterobacteriaceae and other non-fermenting clinical isolates using multiplex PCR. This genotypic method provided a rapid and efficient differentiation of ESBLs in the laboratory.