Prevalence of induced clindamycin resistance in methicillin resistant Staphylococcus aureus from hospital population of coastal Andhara pradesh, South india

Clindamycin (Cd) is one of the important alternative antibiotics in the therapy of Staphylococcus aureus, particularly in methicillin resistant Staphylococcus aureus (MRSA). Without the double-disk test, all the Staphylococcus aureus isolates with inducible Cd would have been misclassified as Cd susceptible, resulting in an underestimated Cd resistance rate. We report a Cd clinical failure where resistance developed on therapy in D-test-positive MRSA strains. The D-test identifies inducible resistance that might presage mutational Cd resistance which can be either constitutive or inducible. The present study was aimed to know the prevalence and phenotypic characterization of induced Cd resistance in MRSA isolates from hospital patients ofvarious medical wards, surgical wards, diabetic care centres and intensive care units (ICU) of different corporate hospitals of Coastal Andhra Pradesh, South India. The specimens were collected from various body fluids and swabs of patients;- blood(n=29), urine (n=50), pus(n=45), nasal swabs (n=40), respiratory tract swabs (n=40), eye swabs (n=50), ear swabs (n=89), and skin infection swabs (n=80). These sampleswere tested for the presence of MRSA and screening was done by Oxacillin discs. Out of the 153 coagulase positive Staphylococcus aureus isolates, 82 were MRSA. Erythromycin (Ery) resistance was observed in 23 isolates which expressed Cd inhibitoryactivity and one isolate was resistant to both Cd and Ery. The present study showed high level of multidrug resistance among MRSA and high incidence of Ery induced Cd resistance is also observed. Hence, it is advisable to include inducible Cd resistance testing as a part of routine antibiotic susceptibility as it may be missed in routine antibiotic testing to avoid treatment failure.

Author(s): Lakshmana Swamy Parasa, Srinivasa Rao Tumati, Srinivasa Prasad Chigurupati, Raja Kumar Parabathina, K Santhisree, L. Cyril Arun Kumar, Venkata Subba Rao Atluri, Showkat Ahmed Shah

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