Abstract

To compare the culture screening protocols for detection of methicillin-resistantStaphylococcus aureus (MRSA) in the surgical wards, one hundred and forty eight samples (116 nasal swabs from 116 patients and 32 environment items swabs) were examined. 96 (64.8%) of the samples stowed S. aureus, 75 (64.6%) from patients, and 21(65.6%) from hospital environment. The detection of MRSA among the isolates of the S. aureus was carried out using direct culture and subculture from mannitol salt agar on HiCrome MeReSa agar medium compared with FOX, OX and ME DD test. Among the 96S. aureus isolates, 63 (65.6%) were HA-MRSA of which 50 (66.6%) and 13 (61.9%) from the patients and environment, respectively. There is no significant difference in the detection rate of MRSA between HiCrome MeReSa Agar and DD test as each showed 63 isolates (50 from patients and 13 from environment). The prevalence of MRSA in both was 42.5% (63/148) and 22.3% (33/148) of MSSA. Lower detection of 47 and 11 MRSA isolates with prevalence 39.1% (58/148) was obtained after 24 h of incubation by direct culture method on HiCrome Agar, respectively. The report time was fastest (24 h) in direct culture on HiCrome agar and the slowest (48 h) in subculture on HiCrome Me ReSa Agar and OX, FOX, ME disc diffusion test. In the patients screening samples, the sensitivity, specificity, positive predictive value PPV and negative predictive value NPV between direct culture on HiCrome Agar medium and DD test were 94, 100, 100 and 95.6%, respectively, while in the environment samples were 84.6, 100, 100 and 90.4%, respectively. Patient's samples demonstrated higher sensitivity and NPV than environment samples but the same rate in specificity and PPV. In contrast, no observed differences between results from subculture on HiCrome Agar medium and (OX, FOX and ME) DD test, which agreed in their sensitivity, specificity, PPV and NPV. The study also revealed that all MRSA isolates were multidrug resistant (MDR) and they were highly resistant (100%) to Beta-lactam antibiotics: oxacillin, cefoxitin, methicillin, ampicillin and amoxicillin.

Key words: Methicillin resistant Staphylococcus aureus (MRSA), hospital acquired methicillin resistant Staphylococcus aureus (HA-MRSA), Iraq, chromogenic medium, surgical wards.