Detection of inducible clindamycin resistance in methicillin-resistant and -susceptible staphylococcus aureus isolated from clinical samples in a tertiary care hospital of Dhaka City

Abstract

A Gram-positive bacterium, Staphylococcus aureus, a microorganism present in the nasal passages of approximately 30% of individuals and on the skin of around 20% is responsible for a diverse range of clinical illnesses. Reputed as the most perilous among the numerous common types of staphylococcus aureus bacteria which often cause skin infections. One of the global public health issues is managing the infections of methicillin-resistant S. aureus (MRSA) is quite challenging for its resistance to many antibiotics. MLSB antibiotics, including macrolides, lincosamides, and streptogramin B, are frequently employed in the treatment of MRSA (Methicillin-resistant Staphylococcus aureus). The resistance to these MLSB antibiotics among MRSA is increasing which can occur through efflux mechanisms or through inducible or constitutive resistance mechanisms. The pathogen is often treated by clindamycin whereas overuse of these antibiotics can increase the likelihood of acquiring inducible clindamycin resistance, leading to therapeutic failure and D-test is a necessity to detect such resistance. The objective of this study was to identify inducible clindamycin-resistant Staphylococcus aureus strains among both Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-sensitive Staphylococcus aureus (MSSA) isolates. Therefore, a total of 200 clinical samples (wound swabs, pus, urine, blood) were collected from October 2022 to July 2023, from a tertiary care hospital in Dhaka city, out of which 48% were MRSA both phenotypically and genotypically. Inducible resistance was found among 64 (32%) isolates, and constitutive resistance in 53 (26.5%). MRSA had higher inducible (50%) and constitutive resistance (31.2%) than MSSA strains (15.3%, and 22.1% respectively). Female patients exhibited a higher prevalence of inducible clindamycin resistance (82.8%), as well as inpatients (87%). All strains showing inducible clindamycin resistance demonstrated 100% sensitivity to vancomycin. The study indicates that implementing the D-test as a standard procedure in routine disc diffusion testing is essential to prevent treatment failures.