Abstract
Macrolide resistance of staphylococci has risen dramatically in recent years generating a real challenge for their treatment as therapeutic options have become very limited. In this study, an antibiogram analysis of one hundred and fifty Staphylococcus sp. isolates collected from various clinical specimens, against erythromycin, azithromycin, spiramycin, and clindamycin was carried out. Out of the 150 collected Staphylococcus sp. isolates, 54 isolates (36%) showed resistance to two or more of the tested macrolides. Inducible macrolide, lincosamides and streptogramin type B resistance phenotype (iMLS) using D-test was identified in 15 of the resistant isolates (27.8%). Molecular detection of major genes coding for macrolide resistance, including erythromycin ribosomal methylase (ermA and ermC), and macrolide-streptogramin resistance gene (msrA) was carried out using PCR. It was found that 51.8, 37.1 and 11.1% of the resistant isolates carried one, two and three types of the resistance genes, respectively. However, ermC was the most frequently occurring gene (81.5%), followed by the msrA gene (42.6%), then the ermA gene (35.2%). In conclusion, the genotypic analysis revealed that the majority of the tested isolates harbored two or more macrolide resistance-coding genes where 36% displayed resistance to at least two of the most common macrolide antibiotics used in the treatment of such important pathogens particularly in patients exhibiting hypersensitivity to penicillins according to several international guidelines. Therefore, it is crucial to carry out more epidemiologic studies to clearly understand the problem of increasing macrolide resistance among Staphylococci and to implement new guidelines for the treatment of such important pathogens, particularly in Egypt.
Highlights
The antimicrobial resistance among bacteria is regarded as a natural phenomenon
It was found that 34 (63%, n= 54) isolates are resistant to the four tested antibiotics; sixteen isolates (30%, n= 54) showed resistance to all macrolides and inducible resistance to lincosamides, which was demonstrated by formation of Dshaped inhibition zone after erythromycinclindamycin disk approximation test (D-test); while only 4 isolates (7%, n= 54) exhibited resistance to macrolides only (MS phenotype)
The percentages of macrolide resistance phenotypes are shown in Fig (1), and the D-test showing inducible resistance is shown in Fig (2)
Summary
The antimicrobial resistance among bacteria is regarded as a natural phenomenon. The terrifying rise in the percentages of the resistance of pathogenic bacteria to different classes of antibiotics is becoming very prominent worldwide [1]. Staphylococci are regarded as a normal commensal of both the skin and mucous surfaces. There are many species of staphylococci, some of them can result in a variety of human diseases, and on the other hand, some are commensal and considered not to be pathogenic [4]. S. aureus and Coagulasenegative Staphylococci are regarded as both a commensal bacteria as well as human pathogens; since they are found as normal flora in about 30% of the total human population. They are the major cause of a wide range of infections as bacteremia, infective endocarditis, skin infections and infections related to medical devices [5,6]
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