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Evaluation of various phenotypic methods with genotypic screening for detection of methicillin-resistant Staphylococcus aureus

Archana Loganathan
Archana Loganathan
, 
Prasanth Manohar
Prasanth Manohar
, 
Kandasamy Eniyan
Kandasamy Eniyan
, 
Rama Jayaraj
Rama Jayaraj
 and 
Ramesh Nachimuthu
Ramesh Nachimuthu
   | Jun 25, 2020
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Article Category: Technical report
Published Online: Jun 25, 2020
Page range: 225 - 233
DOI: https://doi.org/10.1515/abm-2019-0065
Keywords
© 2019 Archana Loganathan et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Background

Staphylococcus aureus is one of the common opportunistic gram-positive pathogens which are often associated with nosocomial infections. Detection of methicillin-resistant S. aureus (MRSA) has become complicated due to the complex phenotypic and genomic pattern.

Objective

To evaluate the sensitivity and specificity pattern of various phenotypic methods used in screening mec genes harboring MRSA.

Methods

Clinical isolates of S. aureus were collected from diagnostic centers in Tamil Nadu. Phenotypic identification methods such as Minimal Inhibitory Concentration for oxacillin, oxacillin screen agar (OSA), oxacillin disk diffusion, and cefoxitin disk diffusion (CFD) tests were compared. The clinical isolates were classified into MRSA and methicillin-susceptible S. aureus (MSSA) based on the polymerase chain reaction (PCR) amplification of the mecA gene.

Result

Out of 50 S. aureus, 21 were found to be MRSA based on the presence of the mecA gene. All 21 mecA-positive isolates were found to be resistant through minimum inhibitory concentration (MIC) and CFD test, having a sensitivity of 100% and specificity of 52% and 62%, respectively. OSA and oxacillin disk tests were found to have a sensitivity of 86% and specificity of 48% and 52%, respectively.

Conclusion

The combination of two phenotypic methods, CFD and oxacillin MIC, can be used for the detection of MRSA in clinical laboratories.

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Language:
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Medicine, Assistive Professions, Nursing, Basic Medical Science, other, Clinical Medicine
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