Higher Incidence of Pristinamycin Resistance among Enterococcus Faecium with iMLSB/cMLSB Phenotype
Alexander Kiruthiga,1,2 Kesavaram Padmavathy,1* Praveen Shabana3 , Sumathi Gnanadesikan4 and Jeevan Malaiyan 4

1Department of Microbiology, Research Laboratory for Oral and Systemic Health, Sree Balaji Dental College and Hospital, BIHER, Chennai. India.

2Department of Microbiology, Priyadarshini Dental College and Hospital, Pandur, Thiruvallur, India.

3Department of Laboratory Medicine, Meitra Hospital, Calicut, India.

4Department of Microbiology, Sri Muthukumaran Medical College Hospital and Research Institute, Chennai, India

Corresponding Author E-mail : padmabakianath@gmail.com

Abstract: Pristinamycin(quinupristin/dalfopristin) is recommended for the treatment of serious infections caused by Enterococcus faecium. Nevertheless, screening for pristinamycin (Q/D) susceptibility is not routinely performed. Decreased in-vivo bactericidal activity of quinupristin/dalfopristin is reported in E. faecium with iMLSB phenotype. Non-urinary clinical isolates of E.faecalis (n= 16) and E.faecium (n=9) were screened for inducible clindamycin resistance by D test and susceptibility to the standard antimicrobials by disc diffusion assay. High-level resistance to gentamicin and streptomycin (HLGRHLSR) was observed in 56% of the isolates. All the isolates were susceptible to vancomycin, linezolid and teicoplanin. Of the 25 isolates, 64%, 20%, 4% exhibited cMLSB, iMLSB phenotype and M type respectively. Three isolates (12%) belonged to an uncommon erythromycin-intermediately susceptible and clindamycin-resistant phenotype.  All the E. faecium isolates with iMLSB phenotype were resistant to pristinamycin nevertheless, M type and EryISclinR phenotypes were found to be susceptible to pristinamycin. Routine screening for inducible clindamycin resistance among E.faecium, would detect iMLSB/cMLSB  phenotypes thereby, predict the possible decrease  in-vivo activity/clinical inefficacy of pristinamycin.

Keywords: Enterococcus Faecium; HLGR; HLSR; Pristinamycin

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