Prevalence of resistance phenotypes and genotypes to macrolide, lincosamide and streptogramin antibiotics in Gram-positive cocci isolated in Tunisian Bone Marrow Transplant Center
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Abstract
To investigate the prevalence of resistance to macrolide, lincosamide and streptogramin
(MLS) antibiotics in Gram-positive cocci isolated in a Bone Marrow Transplant Center
of Tunisia, we tested the antibiotic susceptibility of 172 clinical isolates of Staphylococcus
epidermidis, Streptococcus mitis and Enterococcus faecium to macrolide erythromycin
and spiramycin, the lincosamide clindamycin and the streptogramin pristinamycin. These
three groups of organisms were mostly resistant to macrolides and lincosamide, but
were commonly susceptible to pristinamycin. The resistance phenotypes of erythromycin-resistant
isolates were determined by the five-disc test with erythromycin, spiramycin, lincomycin,
clindamycin and pristinamycin, which showed that most exhibited constitutive MLS resistance.
In order to determine the prevalence of the resistance genotypes and the resistance
mechanisms, the prevalence of the erythromycin resistance methylase (erm) (A), erm(B),
erm(C), msr(A) and macrolide efflux (mef) (A) genes in the erythromycin-resistant
isolates was identified by polymerase chain reaction (PCR) analysis. The resistance
was due mainly to the presence of ermB in E. faecium (80%), ermC in S. epidermidis
(53%) and mefA in S. mitis (65%).