[期刊论文][Full-length article]

出版年：2023

Purpose In this study, we aimed to investigate the occurrence of MLS_b resistance in clinical isolates of Staphylococcus aureus with respect to their association with transposons. Methods The present study was performed with clinical isolates of S. aureus . The MLS_b resistant phenotypes in the obtained isolates were determined by D zone test or double disc diffusion test as per CLSI 2020 guidelines. MLS_b resistance encoding genes were detected by PCR. The genes tested were ermA , ermB, ermC , msrA , mphC , vga , vgb and lnuB . The MLS_b resistant Staphylococcal isolates were selected to analyze the association of the genes with mobile genetic elements Tn554, Tn5406, Tn917, Tn6133, Tn551 by PCR based method. Primer pairs were designed using sequences from transposons and the resistance genes, respectively. Results During this study, 268 isolates of S. aureus were obtained of which 233 (86.94%) isolates exhibited different MLS_b resistant phenotypes. The predominant gene among the MLS_b resistant isolates was msrA followed by vgaA and mphC genes. PCR assay was employed to determine whether the genes msrA , mphC and vgaA were carried by Tn554, Tn5406, Tn917, Tn6133, Tn551 transposons. PCR amplification with the designed primer pairs revealed vgaA gene being part of Tn5406. Conclusion The presence of Tn5406 in all the vgaA harboring isolates highlights its potential of spread across isolates. Moreover, the co-existence of different MLS_b resistance encoding genes observed in the study shows that the combination of genes involved in different mechanism mediated the nature of MLS_b resistance. Introduction Macrolide, lincosamide, and streptogramin (MLS_b) antibiotics are although chemically different but have a similar mode of action and act by inhibiting protein synthesis of bacteria. Macrolides have their binding sites on the 23S rRNA of the 50S subunit, overlapping lincosamides and streptogramins, which is the prime reason for cross-resistance [1,2]. The widespread use of MLS_b drugs to treat staphylococcal infections has led to the emergence of resistant strains which subsequently spread in different parts of the world. This resistance is associated with the presence of genes encoding ribosome methylases ( erm ), phosphotransferases ( mphC ) and ATP dependent efflux pumps ( msrA, vga ) [[3], [4], [5]]. Antibiotic resistance genes are often found part of mobile genetic elements or transposons. Transposons are discrete nucleotide sequences that are capable of migrating from one site of the chromosome to the other. These are usually responsible for capture and intra and intercellular mobility of genes within and between chromosomes and plasmids leading to widespread dissemination of resistance across different strain, species, and genus [6,7]. A number of transposons have been identified in Staphylococci over the past few years which have been reported to carry and spread a diverse range of antibiotic resistant genes in different species of Staphylococci. Tn916 is known to encode tetracycline resistance whereas, Tn552 is associated with penicillin resistance [[8], [9], [10]]. MLS_b resistance in clinical isolates of Staphylococcus aureus is an emerging threat and has been dramatically spreading in India over the past decade but there is paucity of data on the analysis of the association of MLS_b resistance genes with transposons. Therefore, in this study, we aimed to investigate the occurrence of MLS_b resistance in clinical isolates of Staphylococcus aureus with respect to their association with transposons which will provide us a better understanding of the underlying mechanism driving the mobilization and dissemination of MLS_b resistance genes in Staphylococcus aureus. Section snippets Identification of isolates The present study was performed with clinical isolates of S. aureus. The isolates were obtained from Silchar Medical College and Hospital, a tertiary referral hospital in Silchar, Assam, India. The isolates were collected over a period of six months from March 2019 to September 2019.268 isolates of S. aureus were identified using conventional microbiological techniques like Gram staining, rapid biochemical tests (catalase and oxidase tests), serological tests (slide cogulase, tube coagulase and Results During this study, 268 isolates of S. aureus were obtained of which 233 (86.94%) isolates exhibited different MLS_b resistant phenotypes. 135 isolates expressed cMLS_b phenotype (58%, n ​= ​135), 53 isolates expressed MS_b phenotype (23%, n ​= ​53) and 45 isolates expressed iMLS_b phenotype (19%, n ​= ​45). Thirty-five (13.05%) isolates showed susceptibility towards MLS_b antibiotics (erythromycin, clindamycin and pristinamycin). The predominant gene among the MLS_b resistant isolates was msrA Discussion In the present study, the occurrence of MLS_b resistance and their association with transposon were studied. The presence of Tn5406 in all the vgaA harboring isolates highlights the dissemination of the resistant gene in the isolates. This transposon was first characterized in a clinical strain of S. aureus and is very similar to Tn554. Tn5406, like other transposons found in Staphylococci integrates into chromosomal radC gene [11]. In the presence of selective pressure with streptogramin Conclusion The presence of Tn5406 in all the vgaA harboring isolates highlights its potential of spread across isolates. This finding is particularly worrying since the vgaA gene confer resistance to lincosamides, streptogramins and pleuromutilins and its presence in a highly mobile transposon is an important factor in the dissemination of resistance, limiting treatment options. Moreover, the co-existence of different genes observed in the study shows that the MLS_b resistance phenotypes displayed by the CRediT author statement Chandrayee Deshamukhya: Investigation, Visualisation, Writing - Original Draft. Amitabha Bhattacharjee: Conceptualization, Methodology, Supervision. Deepshikha Bhowmik: Writing - Review & Editing. Debadatta Dhar (Chanda): Supervision. Chandrayee Deshamukya - M. Phil, Junior Research Fellow, Department of Microbiology, Assam University, Silchar, 788011, [email protected] , Mobile: 8638680374. Deepshikha Bhowmik - M. Phil, Junior Research Fellow, Department of Microbiology, Assam University, Silchar, Conflicts of interest The authors of this paper state that there are no conflicts of interest. Funding The authors received financial support from Science and Engineering Research Board, Department of Science and Technology , Govt. of India vide no (DST No: EMR/2016/0055226 dated September 18, 2018). Data availability All datasets generated or analyzed during this study are included in the manuscript and/or the Supplementary Files. Ethics statement The work was approved by the Institutional Ethical Committee Assam University, Silchar, vide agenda no. 3, Serial no. 2 in the meeting held on April 09, 2018. Acknowledgement The authors would like to thank Biotech Hub, Assam University, Silchar, India for providing the infrastructure and Science and Engineering Research Board (SERB), Department of Science and Technology, Govt. of India for financial support vide no (DST No:EMR/2016/0055226 dated September 18, 2018). References (21) J. Allignet et al. Sequence of a staphylococcal gene, vat, encoding an acetyltransferase inactivating the A-type compounds of virginiamycin-like antibiotics Gene (1993) T. Hauschild et al. Macrolide resistance in Staphylococcus spp. from free-living small mammals Vet Microbiol (2010) C. Lozano et al. 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Prevalence of genotypes that determine resistance of staphylococci to macrolides and lincosamides in Serbia Front Public Health (2017) O. Chesneau et al. Resistance phenotypes conferred by macrolide phosphotransferases FEMS Microbiol Lett (2007) There are more references available in the full text version of this article. Cited by (0) Recommended articles (6) View full text © 2023 Indian Association of Medical Microbiologists. Published by Elsevier B.V. All rights reserved. About ScienceDirect Remote access Shopping cart Advertise Contact and support Terms and conditions Privacy policy We use cookies to help provide and enhance our service and tailor content and ads. By continuing you agree to the use of cookies . Copyright © 2023 Elsevier B.V. or its licensors or contributors. ScienceDirect® is a registered trademark of Elsevier B.V. ScienceDirect® is a registered trademark of Elsevier B.V.

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