Prevalence and Molecular Analysis of Erythromycin and Clindamycin Resistance in Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus Isolates from Basra, Iraq | ||
| Egyptian Journal of Medical Microbiology | ||
| Articles in Press, Accepted Manuscript, Available Online from 04 October 2025 | ||
| Document Type: New and original researches in the field of Microbiology. | ||
| DOI: 10.21608/ejmm.2025.423759.1872 | ||
| Authors | ||
| Hawraa Abdul Mutalib* ; Khairallah A.S. Mohammed | ||
| Department of Medical Lab Technology, College of Health and Medical Technology, Southern Technical University, Basra, Iraq | ||
| Abstract | ||
| Background: Erythromycin resistance and erythromycin-induced clindamycin resistance in Staphylococcus aureus pose significant therapeutic challenges due to the risk of treatment failure in inducible phenotypes. Objectives: This study assessed the prevalence of macrolide–lincosamide–streptogramin B (MLSB) resistance phenotypes and their genetic determinants in clinical isolates from Basra, Iraq. Methodology: A total of 108 S. aureus isolates (41 MRSA, 67 MSSA) were recovered from various infections. Species identification was based on morphological and biochemical examinations, and further confirmed by the VITEK 2 system. Methicillin resistance was determined using oxacillin and cefoxitin disk diffusion and confirmed by mecA PCR. MLSB phenotypes, constitutive (cMLSB), inducible (iMLSB), and MS, were evaluated by erythromycin–clindamycin susceptibility and the D-test. PCR screening targeted ermA/B/C, msrA/B, lnuA/B, and mphC genes. Results: MRSA isolates showed significantly higher resistance to erythromycin (51.2% vs. 24%) and clindamycin (42% vs. 19%) than MSSA. The fully susceptible phenotype was more common in MSSA (77.6%) than MRSA (48.8%). cMLSB predominated in MRSA (34.1% vs. 10.45%), while iMLSB was observed in 17.1% of MRSA and 10.45% of MSSA. The MS phenotype was rare. Among 36 MLSB-resistant isolates, none carried a single determinant; all harbored ≥2 genes, most frequently ermB + ermC + lnuA + mphC (27.8%). Co-carriage of ermB/C exceeded 90%, lnuA was universal, while lnuB was absent. Conclusion: Our findings confirm the central role of erm genes in MLSB resistance among MRSA, in line with global trends, while the unusually high prevalence of ermB and the universal presence of lnuA represent a distinctive regional genetic signature that warrants attention for local surveillance and stewardship strategies. | ||
| Keywords | ||
| Clindamycin resistance; MRSA; ermB gene; lnuA gene; iMLSB | ||
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