Characteristics of beta-lactamases and their genes (blaA and blaB) in Yersinia intermedia and Y. frederiksenii.
BACKGROUND
The presence of beta-lactamases in Y. enterocolitica has been reported to vary with serovars, biovars and geographical origin of the isolates. An understanding of the beta-lactamases in other related species is important for an overall perception of antibiotic resistance in yersiniae. The objective of this work was to study the characteristics of beta-lactamases and their genes in strains of Y. intermedia and Y. frederiksenii, isolated from clinical and non-clinical sources in India.


RESULTS
The enzymes, Bla-A (a constitutive class A penicillinase) and Bla-B (an inducible class C cephalosporinase) were found to be present in all the clinical and non-clinical strains of Y. intermedia and Y. frederiksenii by double disc diffusion method. The results showed differential expression of Bla-A as indicated by presence/absence of synergy whereas expression of Bla-B was quite consistent. The presence of these enzymes was also reflected in the high minimum inhibitory concentrations, MIC50 (126-1024 mg/L) and MIC90 (256-1024 mg/L) of beta-lactam antibiotics against these species. Restriction fragment length polymorphism (RFLP) revealed heterogeneity in both blaA and blaB genes of Y. intermedia and Y. frederiksenii. The blaA gene of Y. intermedia shared significant sequence identity (87-96%) with blaA of Y. enterocolitica biovars 1A, 1B and 4. The sequence identity of blaA of Y. frederiksenii with these biovars was 77-79%. The sequence identity of blaB gene of Y. intermedia and Y. frederiksenii was more (85%) with that of Y. enterocolitica biovars 1A, 1B and 2 compared to other species viz., Y. bercovieri, Y. aldovae and Y. ruckeri. Isoelectric focusing data further revealed that both Y. intermedia and Y. frederiksenii produced Bla-A (pI 8.7) and "Bla-B like" (pI 5.5-7.1) enzymes.


CONCLUSIONS
Both Y. intermedia and Y. frederiksenii showed presence of blaA and blaB genes and unequivocal expression of the two beta-lactamases. Limited heterogeneity was detected in blaA and blaB genes as judged by PCR-RFLP. Phylogenetic relationships showed that the two species shared a high degree of identity in their bla genes. This is the first study reporting characteristics of beta-lactamases and their genes in strains of Y. intermedia and Y. frederiksenii isolated from Asian region.
Mittal
Shilpi
S
Microbial Pathogenicity Laboratory, Department of Microbiology, University of Delhi South Campus, New Delhi, India. shilpimittal1@rediffmail.com <shilpimittal1@rediffmail.com>
Mallik
Sarita
S
Sharma
Sachin
S
Virdi
Jugsharan S
JS
D000595:Amino Acid Sequence; D002510:Cephalosporinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010405:Penicillinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D015007:Yersinia / Q000201:enzymology / Q000235:genetics*; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D004269:DNA, Bacterial; D002510:Cephalosporinase; D010405:Penicillinase; D001618:beta-Lactamases