Detection and prevalence of inducible clindamycin resistance in staphylococci

Abstract

Staphylococcus aureus and coagulase-negative staphylococci (CNS) are recognized as causing nosocomial and community-acquired infections in every region of the world. The resistance to antimicrobial agents among staphylococci is an increasing problem. Clindamycin (CL) is considered to be one of the alternative agents in these infections. This study demonstrates a simple, reliable method (double-disc diffusion test) for detecting inducible resistance to CL in erythromycin-resistance (ER-R) isolates of S. aureus and CNS. A total of 883 (52.3 %) isolates of S. aureus and 804 (47.7 %) isolates of CNS were selected from recent (2003)(2004)(2005) clinical isolates recovered in the laboratory of the authors; duplicate isolates were not included. A total of 214 (12.6 %) S. aureus and 308 (18.3 %) CNS isolates were selected based on ER-R and CL sensitivity using standard National Committee for Clinical Laboratory Standards disc diffusion testing. A total of 1687 staphylococcal isolates were included, consisting of 27.5 % meticillin-resistant S. aureus, 24.8 % meticillin-sensitive S. aureus, 36.1 % meticillin-resistant CNS and 11.6 % meticillin-sensitive CNS isolates: 30.9 % of staphylococcal isolates (214 S. aureus and 308 CNS) that were erythromycin resistant and CL sensitive were tested for inducible resistance using the D-test. A D-shaped zone around the CL was observed for 70.9 % of staphylococcal isolates (81.8 % of S. aureus isolates and 63.3 % of CNS isolates) with an ER-R and a clindamycin-sensitive (CL-S) phenotype. The organism was positive for inducible clindamycin resistance (CL-R). There was a 21.9 % level of inducible macrolide-lincosamide-streptogramin B resistance phenotype among all the staphylococcal isolates. When the S. aureus and CNS strains among all the staphylococcal isolates were compared statistically, inducible CL-R in CNS strains was determined to be 23 % more positive (P=0.028, odds ratio 0.77, 95 % confidence interval 0.61-0.98). When a statistical comparison was performed among ER-R but CL-S staphylococcal isolates inducible CL-R in S. aureus strains was determined to be 2.6 times more positive (P=0.000, odds ratio 2.6, 95 % confidence interval 1.68-4.04). A simple, reliable method of detecting inducible resistance to CL in ER-R isolates of S. aureus and CNS is described. Clinical microbiology laboratories should use the double-disc diffusion test as standard practice with all ER-R staphylococci. CL should not be used in patients with infections caused by inducibly resistant staphylococcal isolates. Therapeutic failures may thus be avoided.

Distribution of erm genes and low prevalence of inducible resistance to clindamycin among staphylococci isolates

“…The presence of more than one erm gene was not detected in S. aureus but it was observed in four SCN isolates. According to Martineau et al,in Canada,20.9% of the S. aureus were positive for the ermA gene and 66% of CNS were positive for the ermC gene, demonstrating that the prevalence of the ermA gene in S. aureus is slightly lower in comparison to other studies. 22 A multicenter study in 24 European university hospitals confi rmed the high prevalence of ermA gene and the low prevalence of ermC and ermB genes among 851 S. aureus.…”

“…14 In Turkey it was demonstrated that the prevalence of the cMLS B phenotype is higher than that of the iMLS B phenotype and the MS B phenotype is low, data similar to our study. 15,[18][19][20] A previous study conducted in our city evaluated 200 CNS and showed that only 2.5% of isolates presented the iMLS B resistance phenotype. 21 Therefore, one could speculate that the prevalence of the inducible phenotype is low in our city.…”

Inducible Clindamycin Resistance in Clinical Isolates of Staphylococci

“…The increasing frequency of staphylococcal infections among patients and changing patterns of antimicrobial resistance have led to renewed interest in the use of clindamycin therapy to treat such infections (13,14) . Clindamycin is frequently used to treat skin and bone infections because of its tolerability, cost, oral form and excellent tissue penetration, and the fact that it accumulates in abscesses and no renal dosing adjustments are needed (14) .…”

Clinical Microbiology Services are Essential for Diagnosis, Treatment and Prevention of MRSA and Other Nosocomial Pathogens in Libyan Healthcare Facilities

“…They studied 110 isolates of Staphylococcus aureus and determined that inducible resistance to clindamycin occurred in two-thirds of MRSAs, but was not seen with methicillin-sensitive S. aureus (MSSA). The ‘D-test’ (which is so called because of the shape of inhibition produced on the plate) was recommended for use in local microbiology laboratories to determine inducible resistance in staphylococci [2, 3]. Most routine laboratories may find it easier to rely simply on the results of erythromycin testing.…”