[01] Kumurya A. S., Department of Medical Laboratory Science, Faculty of Allied Health Sciences, Bayero University, Kano, Nigeria.

Background: Most routine laboratory detection of Staphylococcus aureus isolates is based on rapid agglutination test systems. Failure of agglutination assays to identify methicillin-resistant S. aureus strains (MRSA) has been demonstrated. Objectives: The aim of this study was to evaluate the sensitivity and specificity of MRSA detection by agglutination test system using MastalexTM MRSA kit (Mast diagnostics, UK). The test kits used in this study have been tested for this purpose before. Methods: As determined by Polymerase chain reaction, 100MRSA strains staphylococci were included. Species identification and determination of susceptibility patterns were performed using colony morphology, Gram stain, catalase testing, tube coagulase testing, DNAase testing, mannitol fermentation, susceptibility testing towards oxacillin, and PCR of the mecA gene. Results: Among the 100 methicillin resistant Staphylococcus aureus isolates tested oxacillin disc diffusion and latex agglutination technique, PCR of the mecA gene confirmed the identification of only 5 (0.5%) MRSA strains. Sensitivity of the agglutination tests ranged from 82•7 to 100•0 % for MRSA strains and 92•8 to 100•0 % for MSSA strains, respectively. Specificity of the test systems ranged from 91•3 to 99•1 %. None of the six agglutination assays produced correct reactions for all staphylococci tested. For the other tests kits, sensitivity of MRSA detection was lower than for MSSA isolates. Ninety five (22.5%) and fifty seven (13.5%) of the 423 MRSA isolates did not grow on Oxoid Mannitol Salt Agar (MSA) and Mast MSA media without oxacillin, respectively. All the 423 MRSA isolates grew on oxoid blood agar with or without oxacillin. Conclusion: Depending upon the local MRSA prevalence and the parameter of interest (sensitivity or specificity), these test systems may be useful for routine diagnostic purposes.

Agglutination, MRSA, Sensitivity, Specificity, PCR

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