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Introduction:The increased frequency of Methicillin-resistant Staphylococcus aureus infections has led to renewed interest in the macrolide-lincosamide streptogramin B (MLS) group of antibiotics. Resistance to these antibiotics may be constitutive or inducible. Isolates resistant to erythromycin may show false in vitro susceptibility to clindamycin, leading to therapeutic failures. This study investigated the utility of the D-Test for detecting inducible clindamycin resistance in methicillin-resistant S. aureus isolates and determining the prevalence of various phenotypes in our region. Methods: For detecting inducible clindamycin resistance, a D-test using erythromycin and clindamycin as per CLSI guidelines was performed, and four different phenotypes were interpreted as methicillin-sensitive (MS) phenotype (D-test negative), inducible MLSB (iMLSB) phenotype (D-test positive), constitutive MLSB phenotype and sensitive to both. Results: Of the 987 isolates tested, 400 (40.53%) were MRSA. The prevalence of iMLSB, cMLSB phenotype, MS phenotype and sensitive phenotype in MRSA isolates was 42.5%, 10.5%, 28% and 19%, respectively. The iMLSB and cMLSB phenotypes were higher in males (24.75%, 6.25%) than females (P-value = 0.137). The majority of MRSA isolates originated from pus (83%). All S. aureus isolates showed 100% sensitivity to vancomycin and linezolid. Conclusion: This study emphasizes the prevalence of inducible clindamycin resistance in MRSA in our setup. Incorporating the D-test into the routine Kirby-Bauer disk diffusion method in clinical microbiology laboratories will help clinicians make judicious use of clindamycin, minimizing treatment failure.

Background & Aims: carbapenem-resistant strains of Acinetobacter baumannii (A. baumannii) have been reported worldwide over the last decade. Detection of the carbapenemases is crucial to determine the severity of the problem. The aim of our study was to detect Carbapenemase and MBL producing strains among Multidrug Resistant (MDR) Acinetobacter species isolated from clinical specimens in this geographical area by Modified Hodge test (MHT) and Imipenem-EDTA double disc synergy test and their evaluation. Materials & Methods:In this descriptive-prospective study, consecutive, non-duplicate, and resistant-to-carbapenems clinical strains of Acinetobacter species isolated from various clinical samples were included. Antimicrobial sensitivity of Acinetobacter isolates was performed on Mueller Hinton agar plates by Kirby-Bauer disk diffusion method. Carbapenemase production was confirmed by MHT.Confirmation of MBL production was done by subjecting all isolates with positive screen test to combined disc test using imipenem, meropenem, and EDTA. Data analysis was done using Epi Info 7.0. Categorical variables were summarized as frequency and percentage and continuous variables as Mean and SD.Results: A total of 312 non-duplicate strains of A. baumannii were isolated, out of which 224 (71.79%) strains were resistant and 88 (28.21%) were sensitive to carbapenem. There was 100% sensitivity to Colistin followed by Tigecycline (79%) whereas high degree of resistance was seen against 2nd and 3rd generation cephalosporins and quinolones (>90%). 82.6% were identified as carbapenemase producers on MHT and on Imipenem-EDTA combined disc test (CDT), 21.4% were found to be positive. Conclusion:Our study showed that tests like MHT are equally efficient to detect carbapenemase production, followed by Imipenem-EDTA combined disc test. These tests are cost-effective and easy to perform and may be used routinely to assess whether carbapenemase producers are present or not.