Mittal Shilpi, Mallik Sarita, Sharma Sachin, Virdi Jugsharan S
Microbial Pathogenicity Laboratory, Department of Microbiology, University of Delhi South Campus, New Delhi, India.
BMC Microbiol. 2007 Apr 3;7:25. doi: 10.1186/1471-2180-7-25.
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.
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.
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.
据报道，小肠结肠炎耶尔森菌中β-内酰胺酶的存在因菌株的血清型、生物型和地理来源而异。了解其他相关物种中的β-内酰胺酶对于全面认识耶尔森菌属的抗生素耐药性很重要。这项工作的目的是研究从印度临床和非临床来源分离的中间型耶尔森菌和费氏耶尔森菌菌株中β-内酰胺酶及其基因的特征。
通过双纸片扩散法发现，在所有中间型耶尔森菌和费氏耶尔森菌的临床和非临床菌株中均存在酶Bla-A（一种组成型A类青霉素酶）和Bla-B（一种诱导型C类头孢菌素酶）。结果显示，Bla-A的表达存在差异，表现为协同作用的有无，而Bla-B的表达相当一致。这些酶的存在也反映在β-内酰胺类抗生素对这些物种的高最低抑菌浓度上，MIC50（126 - 1024mg/L）和MIC90（256 - 1024mg/L）。限制性片段长度多态性（RFLP）揭示了中间型耶尔森菌和费氏耶尔森菌的blaA和blaB基因均存在异质性。中间型耶尔森菌的blaA基因与小肠结肠炎耶尔森菌生物型1A、1B和4的blaA基因具有显著的序列同一性（87 - 96%）。费氏耶尔森菌的blaA基因与这些生物型的序列同一性为77 - 79%。与其他物种，即贝氏耶尔森菌、奥尔登耶尔森菌和鲁氏耶尔森菌相比，中间型耶尔森菌和费氏耶尔森菌的blaB基因与小肠结肠炎耶尔森菌生物型1A、1B和2的序列同一性更高（85%）。等电聚焦数据进一步表明，中间型耶尔森菌和费氏耶尔森菌均产生Bla-A（pI 8.7）和“类Bla-B”（pI 5.5 - 7.1）酶。
中间型耶尔森菌和费氏耶尔森菌均显示存在blaA和blaB基因，且两种β-内酰胺酶表达明确。通过PCR-RFLP判断，blaA和blaB基因存在有限的异质性。系统发育关系表明，这两个物种的bla基因具有高度同一性。这是第一项报道从亚洲地区分离的中间型耶尔森菌和费氏耶尔森菌菌株中β-内酰胺酶及其基因特征的研究。
