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Alexander Kiruthiga ¹, Kesavaram Padmavathy ¹, Praveen Shabana ², Sumathi Gnanadesikan ³, Jeevan Malaiyan ³, T. Shoba ⁴

Affiliations
1 Department of Microbiology, Research Laboratory for Oral and Systemic Health, Sree Balaji Dental College and Hospital, BIHER, Chennai, IN
2 Department of Laboratory Medicine, Meitra Hospital, Calicut, IN
3 Department of Microbiology, Sri Muthukumaran Medical College Hospital and Research Institute, Chennai, IN
4 Department of General Pathology, Sree Balaji Dental College and Hospital, BIHER, Chennai, IN

Abstract

Fosfomycin, a broad spectrumbactericidal agent had been recommended by the Food and Drug Administration for the treatment of uncomplicated urinary tract infections. However, studies on the susceptibility rate of Enterococcus faecalis against fosfomycin are inadequate. Hence, this study was aimed to determine the invitro susceptibility to fosfomycinamong urinary E. faecalis. A total of about 70 non-repetitive isolates of Enterococcus faecalis isolated from the urine samples were included in the study. Susceptibility to fosfomycin, linezolid, teicoplanin, high level gentamicin, high level streptomycin was determined by Kirby Bauer disk diffusion method. Preliminary screening to minimum inhibitory concentration of high level aminoglycosides was assessed by agar dilution method. Vancomycin resistance was detected by agar screening method and further confirmed with e-test and interpreted as per CLSI guidelines. Our results indicate, increased susceptibility to teicoplanin (98.57%) followed by fosfomycin (95.71%) and linezolid (68.57%). Of note, none of the isolates were resistant to vancomycin. Of the 70 E. faecalis isolates screened, 61.43% isolates exhibited HLG^R phenotype) and 37.14% exhibited HLS^R phenotype. HLG^RHLS^R phenotype was observed among 32.9% of the isolates. MIC of gentamicin and streptomycin was found to be ≥512μg/ mL (HLGR isolates) and ≥2000μg/mL (HLSR isolates) respectively. 91.3% of our HLAR isolates (93% HLGR, 92.3% HLSR) were susceptible to fosfomycin. Hence, it could be speculated that fosfomycin can be considered in the treatment of uncomplicated urinary tract infections caused by high level aminoglycoside/ linezolid resistant/glycopeptide resistant E.faecalis.

Keywords

Enterococcus Faecalis, Fosfomycin, HLGR, HLSR.

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Kiruthiga Alexander ¹, Padmavathy Kesavaram ², Shabana Praveen ³, Sumathi Gnanadesikan ⁴, Jeevan Malaiyan ⁵

Affiliations
1 Research Scholar, Department of Microbiology, Research Laboratory for Oral and Systemic Health, Sree Balaji Dental College and Hospital, BIHER, Chennai, IN
2 Associate Professor, Department of Microbiology, Research Laboratory for Oral and Systemic Health, Sree Balaji Dental College and Hospital, BIHER, Chennai, IN
3 4ead, Department of Laboratory Medicine, Meitra Hospital, Calicut, IN
4 Professor & Head, Department of Microbiology, Sri Muthukumaran Medical College Hospital and Research Institute, Chennai, IN
5 Associate Professor, Department of Microbiology, Sri Muthukumaran Medical College Hospital and Research Institute, Chennai, IN

Abstract

Introduction: Enterococci though being intestinal commensal flora have gained significance as a serious nosocomial pathogen owing to their exceptional ability to survive in the harsh environments and increasing high level resistance to antibiotics. The emergence of high level aminoglycoside resistant (HLAR) clinical enterococcal isolates is of serious concern worldwide and thwarts the available therapeutic options.

Materials and Method: A total of 25 non-repetitive isolates of Enterococci (E. faecalis (n = 15), E. faecium (n= 10)) recovered various clinical samples were screened for HLAR among the isolates was performed by disk diffusion method using High Level Gentamicin and High Level Streptomycin disks. The isolates were further confirmed as HLGR and HLSR by agar dilution method. Genes encoding Aminoglycoside Modifying Enzymes (AGMEs) were detected by multiplex PCR. Susceptibility to linezolid was determined by Kirby Bauer disk diffusion method.

Results: All the 25 isolates of enterococci exhibited HLAR phenotype (resistant to HLG and/or HLS). Majority (96%) of the isolates were resistant to HLG and 64% were resistant to HLS. MIC of gentamicin was >500 μg/mL for HLG^R isolates and MIC of streptomycin was MIC > 2000 cg/mL for HLS^R isolates. In our study, 92% of the enterococci harbored aac(6’)-Ie-aph(2’’)-Ia and/or aph(3’)-IIIa. Of note, 15(60%) of the enterococci exhibited dual resistance to gentamicin and streptomycin (HLG^RHLS^R). Nevertheless, 92% of the isolates were found to be susceptible to linezolid.

Conclusion: Prompt detection and characterization of HLAR among clinical strains of Enterococci within our setting is very essential as few of them exhibit co-resistance to glycopeptides and have lost synergism with the cell wall active agents

Keywords

AGMEs, E. faecalis, E. faecium, HLAR, HLG, HLS.

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