Inducible and constitutive clindamycin resistance in Staphylococcus aureus in a northeastern Indian tertiary care hospital

Abstract

Introduction: Staphylococcus aureus is one of the most common pyogenic bacteria. They are notorious for developing prompt resistance to newer antimicrobials. With increasing incidence of methicillin-resistant S. aureus (MRSA) isolates, the treatment options are also becoming limited. Clindamycin is an excellent drug for skin and soft tissue infections, but resistance mediated by the inducible phenotype (iMLS B ) leads to in vivo therapeutic failure even though there may be in vitro susceptibility. The double disk approximation test (D-test) can reliably detect the presence of such isolates. This study was aimed to detect and report the prevalence of the iMLS B phenotype in NEIGRIHMS, a tertiary care center in Northeast India. Methodology: A total of 243 consecutive isolates were subjected to routine identification tests followed by antimicrobial sensitivity testing.Erythromycin-resistant isolates were tested for inducible resistance phenotype by the D-test. Results: Among strains tested, 95 (39%) were erythromycin resistant. Twenty-six (10.7%) isolates were D-test positive (iMLS B phenotype), 41 (16.88%) were constitutively resistant (cMLS B phenotype), and 28 isolates (11.52%) were found to be negative by D-test. The incidence of both inducible and constitutive phenotypes was higher in MRSA isolates compared to methicillin-sensitive S. aureus (MSSA) isolates. Conclusions: This study revealed a moderate prevalence of the inducible clindamycin phenotype in the staphylococcal isolates tested. Clinical microbiology laboratories in areas of high MRSA prevalence should consider performing the D-test routinely. This will help prevent prescription of drug(s) whose therapeutic efficacy is doubtful.

Inducible Clindamycin Resistance among Clinical Isolates of Staphylococcus aureus in a Tertiary Care Hospital, Nanded, Maharashtra, India

“…Truly clindamycinsensitive isolates, which exhibit MS phenotype, were present in 14.38% of MSSA and 9.68% of MRSA isolates in our study. This result is similar to Banik et al, (2015) and Phukan et al, (2015 …”

Antimicrobial susceptibility profile & resistance mechanisms of Global Antimicrobial Resistance Surveillance System (GLASS) priority pathogens from India

“…Perumal et al 5 have reported the bi-functional enzyme aac (6′) Ieaph (2’’) (55.4%) as the predominant AME followed by aph (3’) IIIa (32.3%) and ant (4’) Ia gene (9%). The incidence of inducible (iMLS B ) and constitutive (cMLS B ) clindamycin resistance was higher in MRSA (iMLS B ; 19-28%, cMLS B ; 17-41%) than MSSA (iMLS B ; 6-10 per cent, cMLS B ; 5-10%)6789101112. Inducible clindamycin resistance is conferred through erm A (20%) and erm C (52%) genes3.…”

Detection of inducible and constitutive clindamycin resistance among Staphylococcus aureus isolates in a tertiary care hospital, Eastern India

“…In different studies, the inducible clindamycin ranged from 0% to 37.1% [ Table 4 ]. [ 7 12 15 16 17 18 19 20 21 22 23 24 25 26 27 ] It was observed that percentage of inducible clindamycin resistance was higher among MRSA (24.8%) compared to MSSA (7.5%). The difference between MSSA and MRSA isolates were not statistically significant ( P = 0.2340).…”

“…[ 15 ] In different studies, authors have reported the MS phenotype varies between 0.7% and 44.6% [ Table 4 ]. [ 7 12 15 16 17 18 19 20 21 22 23 24 25 26 27 ] This result implies that clindamycin can be safely and effectively instituted as a therapeutic option in this group of patients even in the presence of macrolide resistance.…”

“…An erythromycin disk (15 μg) and clindamycin (2 μg) were placed 15 mm apart edge-to-edge on MHA plate. [ 12 ] Plates were analyzed after 18 h of incubation at 35°C. Interpretation of zone of inhibition is indicated in [ Table 1 ].…”