Erythromycin and Clindamycin Resistance in Staphylococci Isolated from Pediatric Hospital in Egypt

Erythromycin and clindamycin are major alternatives to βlactam antibiotics. Bacterial resistance to macrolide and lincosamide antibiotics is increasing worldwide. Erm genes express either constitutive macrolide, lincosamide streptogramin B resistance phenotype (cMLSB) or inducible phenotype (iMLSB) and msrA gene expresses (MSB) phenotype. The aim of this study was to determine the frequency of MLSB resistance phenotypes and genotypes and correlation between them in erythromycin-resistant staphylococci. In present study, 154 staphylococcal isolates were collected from various clinical specimens from Cairo University Specialized Pediatric Hospital in Cairo, from September 2012February 2014, and investigated for erythromycin resistance phenotypes by D-zone test and genotypes by multiplex PCR. Ninety 90/154 (58.4%) were erythromycin resistant. Erythromycin-resistant S. aureus (ERSA) were 20/69 (28.9%), while coagulase negative staphylococci (ERCoNS) were 70/85 (82.3%). Only 35.8% of methicillin-resistant S. aureus (MRSA) were (ERSA) and 89.3% of MRCoNS were ERCoNS. cMLSB was 80%, 38.5%, in S. aureus and CoNS respectively, it was more common among MRSA (84.2%). By PCR, ER gene was mainly ermC (70% in SA, 37.14% in CoNS). In Conclusion, cMLSB and ermC were the predominant and no complete correlation between phenotypic and genotypic methods was found. Mona Mohiedden Abdelhalim 1 , Sahar Tolba 2 , Doha Mohamed Dawoud 2* , Mohamed Khaled Ibrahim 2 1 Department of Clinical and Chemical Pathology, Faculty of medicine Cairo University 2 Department of Microbiology, Faculty of science -Ainshams University -Cairo, Egypt. Submission: 2 November 2016 Accepted: 7 November 2016 Published: 25 November 2016 www.ijsrm.humanjournals.com Citation: Doha Mohamed Dawoud et al. Ijsrm.Human, 2016; Vol. 5 (1): 112-122. 113 INTRODUCTION Macrolides, lincosamides and streptogramin B (MLSB) are major alternatives to β-lactam antibiotics in the treatment of infections caused by Staphylococcus spp. especially during the increase of methicillin-resistance among staphylococci which is considered as a therapeutic threat. In addition, they are the choice for penicillin-allergic patients (1, 2, 3). However, the widespread use of MLSB antibiotics has led to an increase in the number of staphylococcal resistant strains (4). Macrolide resistance in Staphylococcus aureus (SA) and coagulase-negative staphylococci (CoNS) is suggested to be due to an active efflux mechanism encoded by msrA gene which confers resistance to 14and the 15membered macrolides and type B streptogramins only (MSB phenotype) which are categorized as resistance to erythromycin, inducible resistance to streptogramin B, and susceptibility to clindamycin by efflux (5). Another mechanism of resistance is due to ribosomal target modification by erm genes which encode Erm-type methyltransferases that confer inducible or constitutive resistance to MLSB agents via methylation of the 23S rRNA, thereby reducing binding by MLS agents to the ribosome (6, 7). Expression of MLSB resistance can be constitutive or inducible. In inducible resistance (iMLSB), bacteria produce inactive mRNA that is unable to encode methylase. The mRNA becomes active only in the presence of a macrolide inducer (Erythromycin). On contrast, in constitutive expression (cMLSB), active methylase mRNA is produced in the absence of an inducer (8, 9). The treatment of patients harboring iMLSB staphylococci with clindamycin leads to the development of constitutive resistance, subsequently leading to therapeutic failure (10). The Clinical and Laboratory Standards Institute (CLSI) has recommended the erythromycin–clindamycin disc approximation test (Dzone) to detect inducible clindamycin resistance (11). The aim of present study was to determine the frequency of MLSB resistance phenotypes and genotypes and correlation between them in erythromycin-resistant staphylococci. MATERIALS AND METHODS