Structural Variabilities in β-Lactamase (blaA) of Different Biovars of Yersinia enterocolitica: Implications for β-Lactam Antibiotic and β-Lactamase Inhibitor Susceptibilities.

Neelja Singhal,Jugsharan Singh Virdi,Abhishikha Srivastava,Manish Kumar,Freddie Salsbury , Jr

doi:10.1371/journal.pone.0123564

Abstract

Yersiniosis caused by Yersinia enterocolitica has been reported from all continents. The bacterial species is divided into more than fifty serovars and six biovars viz. 1A, 1B, 2, 3, 4 and 5 which differ in geographical distribution, ecological niches and pathogenicity. Most Y.enterocolitica strains harbor chromosomal genes for two β-lactamases, blaA an Ambler class A penicillinase and blaB an Ambler class C inducible cephalosporinase. In the present study, susceptibility to b-lactam antibiotics and β-lactamase inhibitor was studied for Y. enterocolitica strains of biovars 1A, 1B, 2 and 4. We observed that β-lactamases were expressed differentially among strains of different biovars. To understand the molecular mechanisms underlying such differential expression, the sequences of genes and promoters of blaA were compared. Also, the variants of blaA present in different biovars were modeled and docked with amoxicillin and clavulanic acid. The mRNA secondary structures of blaA variants were also predicted in-silico. Our findings indicated that neither variations in the promoter regions, nor the secondary structures of mRNA contributed to higher/lower expression of blaA in different biovars. Analysis of H-bonding residues of blaA variants with amoxicillin and clavulanic acid revealed that if amino acid residues of a β-lactamase interacting with amoxicillin and the clavulanic acid were similar, clavulanic acid was effective in engaging the enzyme, accounting for a significant reduction in MIC of amoxicillin-clavulanate. This finding might aid in designing better β-lactamase inhibitors with improved efficiencies in future.

Highlights

Yersinia enterocolitica, the causative agent for Yersiniosis has been reported from all continents, but is most common in Europe
Our findings indicated that variations in the promoter regions and secondary structures of mRNA were not responsible for higher/lower expression of blaA in different biovars
The E-test showed that Y.enterocolitica strains, irrespective of the biovar were sensitive to certain cephalosporins such as cefoxitin, cefpodoxime and cefotaxime. These were all resistant to AMX, though the level of resistance differed among strains of different biovars (Table 1)

Summary

Introduction

The causative agent for Yersiniosis has been reported from all continents, but is most common in Europe. It is represented by more than fifty serovars and six biovars viz. 1A, 1B, 2, 3, 4 and 5 which differ in their geographical distribution, ecological niche and pathogenic potential [1]. Most Y.enterocolitica strains harbor chromosomal genes for two β-lactamases—blaA, a constitutively expressed Ambler class A penicillinase and blaB, an PLOS ONE | DOI:10.1371/journal.pone.0123564. Structural Variabilities in β-Lactamases of Y. enterocolitica Biovars and analysis, decision to publish, or preparation of the manuscript Most Y.enterocolitica strains harbor chromosomal genes for two β-lactamases—blaA, a constitutively expressed Ambler class A penicillinase and blaB, an PLOS ONE | DOI:10.1371/journal.pone.0123564 April 28, 2015

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