Evaluation of various methods for the detection of meticillin-resistant Staphylococcus aureus strains and susceptibility patterns

Abstract

Meticillin-resistant Staphylococcus aureus (MRSA) has been recognized as one of the major pathogens in hospital as well as community settings. In India, the mean isolation rate of MRSA is 20-40 % and many studies have suggested an escalating rate of infections caused by this organism. Despite pharmaceutical and technological advancement, infections caused by MRSA still remain difficult to diagnose. The present study was undertaken to compare five phenotypic methods for the detection of MRSA. This involved examining 200 isolates of S. aureus by oxacillin disc diffusion, cefoxitin disc diffusion, oxacillin screen agar test, the latex agglutination test and growth on CHROMagar. PCR for mecA gene detection was taken as the gold standard. It was found that 35 % of all S. aureus infections were caused by MRSA. The cefoxitin disc diffusion method, as recommended by the Clinical and Laboratory Standards Institute, was found to be a reliable method for MRSA detection but it should be supplemented with some other method like latex agglutination, CHROMagar or oxacillin screen agar testing so that no MRSA is missed. We recommend that along with cefoxitin disc diffusion, another method, preferably latex agglutination, should be routinely used in all hospitals to detect MRSA.

A report on infection dynamics of inducible clindamycin resistance of Staphylococcus aureus isolated from a teaching hospital in India

“…Total 129 (78) 23 (12) 97 (39) 29 (11) Numbers in parenthesis represents D-test positives strains, the total being 140, out of the grand total number of 278 strains. 4 pairs of bivalents as mentioned above (numbers 2, 4, 5 and 6), P-values were statistically significant, signifying there were statistically respectable differences (Table 2).…”

“…Plates were incubated at 37 °C for 18 h and inhibition-zone diameters were measured; a value ≥19 mm was recorded as methicillin resistant and a value, ≤20 mm was considered as methicillin sensitive [11] . For the chromogenic agar media test, pure clinical isolates of S. aureus were streaked onto MRSA-agar, the Hichrome-MeReSa agar (HiMedia, Mumbai), and were incubated for 24 h at 37 °C ; MRSA strains had blue colonies and MSSA strains had white colonies [12] .…”

Ciprofloxacin Sensitivity of <i>Staphylococcus</i> Strains Isolated at the Sylvanus Olympio University Hospital, Togo

“…A disk of each anti-biotic is dispensed with a sterile plier: penicillin (P), kanamycin (K), tobramycin (T), gentamycin (G), lincomycin (L), erythromycin (E), pristinamycin (PT), ofloxacin (OFX), pefloxacin (PEF) or ciprofloxacin (CIP), vancomycin (V), oxacillin (OX) and cefoxitin (FOX). Oxacillin and cefoxitin are used to determine methicillin-resistance [6]. Oxacillin discs are tested on Muller-Hinton media added with 5% NaCl and dropped alone at the middle of the Petri plastic dish measuring 50 mm diameter.…”

Evaluation of different phenotypic methods for the detection of methicillin resistant Staphylococcus aureus and antimicrobial susceptibility pattern of MRSA

“…The zone of inhibition was determined after 16-18 h incubation at 37 0 C. Zone size was interpreted according to CLSI (2016) criteria: susceptible, >22 mm; resistant, <21 mm. 12 …”