Indian Journal of Pathology and Microbiology

: 2013  |  Volume : 56  |  Issue : 1  |  Page : 73--74

Detection of quinupristin-dalfopristin resistance in methicillin-resistant Staphylococcus aureus in South India

Arunava Kali, Selvaraj Stephen, Sivaraman Umadevi, Shailesh Kumar 
 Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Pondicherry, India

Correspondence Address:
Selvaraj Stephen
Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Pondicherry - 607 402

How to cite this article:
Kali A, Stephen S, Umadevi S, Kumar S. Detection of quinupristin-dalfopristin resistance in methicillin-resistant Staphylococcus aureus in South India.Indian J Pathol Microbiol 2013;56:73-74

How to cite this URL:
Kali A, Stephen S, Umadevi S, Kumar S. Detection of quinupristin-dalfopristin resistance in methicillin-resistant Staphylococcus aureus in South India. Indian J Pathol Microbiol [serial online] 2013 [cited 2021 Jan 25 ];56:73-74
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Reports of in vitro antibiotic sensitivity of methicillin-resistant Staphylococcus aureus (MRSA) strains to streptogramin group of antibiotics are very few in Indian literatures. This novel anti-MRSA drug is as effective as vancomycin and a better treatment option, where reduced susceptibility, nephrotoxicity, or allergy precludes the use of vancomycin. During the last decade, quinupristin-dalfopristin resistance in Europe, Latin America, and North America was negligible (0-0.3%), whereas in Taiwan, even though this drug was not available for clinical use, a higher prevalence of resistance (31%) was reported. [1],[2] Though quinupristin-dalfopristin is not used in India, a very high rate (87%) of resistance in MRSA was reported from Northern India. [3] However, our observation was quite different.

We tested 102 MRSA strains isolated between 2004 and 2011 from clinical samples: Exudates, aspirates, blood, and urine, in a tertiary care hospital catering to patients from Pondicherry as well as neighboring districts of Tamil Nadu. S. aureus clinical isolates were identified by standard laboratory methods based on gram stain morphology, catalase, coagulase, and DNase test. Cefoxitin and oxacillin disk diffusion tests were performed as per Clinical and Laboratory Standards Institute (CLSI) guidelines to detect MRSA stains. S. aureus ATCC 25923 and S. aureus ATCC 43300 (MRSA) strains were used for quality control of antibiotic susceptibility tests. The viability of 102 test isolates was maintained by periodic subculture in semisolid nutrient agar. Antibiotic susceptibility by disk diffusion method was performed as per CLSI guidelines using oxoid quinupristin-dalfopristin, vancomycin and teicoplanin disks. All 102 isolates were sensitive to both vancomycin and teicoplanin and had sensitive minimum inhibitory concentration (MIC) for vancomycin as determined by HiComb vancomycin strip (HiMedia, Mumbai, India). Thus, we have not encountered any vancomycin intermediate or resistant S. aureus.

Among 102 isolates, 10 isolates (9.8%) showed intermediate sensitivity and remaining 92 isolates showed sensitivity to quinupristin-dalfopristin by disk diffusion method. No resistant strain was detected. These 10 strains were further tested by VITEK-2 system (BioMerieux, France) for confirmation based on MIC using AST-GP67 card. All were sensitive to quinupristin-dalfopristin with MIC ranging between 0.125 and 0.5 mg/l and were also sensitive to vancomycin (MIC, <2 mg/l). Three studies on quinupristin-dalfopristin resistance of MRSA strains in India have been published till date of which two studies reported 87% and 17.64% resistance based on disk diffusion method and API-BioMerieux system, respectively. [3],[4] There are no Indian studies evaluating susceptibility results of broth dilution, disk diffusion, VITEK, and API system for quinupristin-dalfopristin. Kesari et al.[5] reported two cases of quinupristin-dalfopristin resistant MRSA, where disk diffusion results correlated well with Hicomb E-test strips. However, we found disk diffusion susceptibility results need to be confirmed when compared to MIC (VITEK) method. The high prevalence of quinupristin-dalfopristin resistance in studies based on only disk diffusion test may be erroneous since very high prevalence is otherwise unlikely to be attributed only to regional variation of MRSA clones. Furthermore, it is unlikely to develop such high prevalence of resistance for a drug which is not available in India for clinical or veterinary use. However, our study has a potential limitation-due to economical constrains-detection of susceptibility by VITEK-2 system was restricted only to 10 strains showing intermediate sensitivity to quinupristin-dalfopristin by disk diffusion. In our experience, MRSA strains with resistance or intermediate susceptibility to this novel antibiotic detected by disk diffusion method should be confirmed by MIC values, especially in countries where it is sparsely used.


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