Distribution of Genes Encoding Resistance to Macrolides Among Staphylococci Isolated From the Nasal Cavity of Hospital Employees in Khorramabad, Iran

BACKGROUND: Epidemiological data on antibiotic susceptibility of Staphylococcus strains isolated from nasal carriers in each region can be helpful to select appropriate drugs to eradicate carriage states, control nosocomial infections and also treat patients. OBJECTIVES: The current study aimed to investigate the antibiotic resistance profile and the molecular prevalence of the ermA, ermB, ermC and msrA genes among Staphylococcus strains isolated from the anterior nares of hospital employees. PATIENTS AND METHODS: In this cross-sectional study, a total of 100 Staphylococcus isolates, 51 Staphylococcus aureus, 49 coagulase-negative staphylococci (CoNS) were isolated from the anterior nares of hospital employees in Khorramabad, Iran. Susceptibility pattern to macrolide antibiotics were determined using the disk diffusion method. The polymerase chain reaction (PCR) assay was applied to determine the major erythromycin-resistant genes (ermA, ermB, ermC and msrA). RESULTS: Fifty-three (53%) isolates were simultaneously resistant to erythromycin, azithromycin and clarithromycin (cross-resistance); while 8 (8%) isolates had variable macrolide susceptibility pattern. Among the S. aureus isolates, the difference in prevalence of resistance to erythromycin between males and females was significant (P = 0.011). The frequency of ermA, ermB, ermC, and msrA genes were 3%, 5%, 33% and 20%, respectively. It was also found that out of 53 isolates resistant to erythromycin, 44 (83%) isolates (eight S. aureus and thirty-six CoNS strains) carried at least one of the four tested genes. Eight (8%) isolates had intermediate phenotype to erythromycin, in which 4 (50%) isolates carried ermB or ermC genes. In addition, out of 39 erythromycin-susceptible isolates, 3 (7.7%) isolates were positive for ermB or ermC genes. CONCLUSIONS: No entire association was found between genotype and phenotype methods to detect macrolides-resistant isolates. In addition, distribution of genetically erythromycin-resistant isolates is geographically different among staphylococci. It is recommend removing S. aureus from nasal carriers by proved approaches such as local or systemic administration of effective antibiotics or bacterial interference.