RESUMEN
In this prospective study, we determined phenotypic resistance to erythromycin among gram positive bacteria. Bacterial isolates were identified by conventional methods and by the Micro Scan: D-test zone was performed according to the Clinical and Laboratory Standards institutes [CLSI] recommendations to determine inducible resistance to clindamycin on gram positive bacteria isolated from different clinical specimens. Bacterial isolates included: group A streptococci [GAS], group B streptococci [GBS], viridans streptococci, S pneumoniae, Staphylococcus aureus [S.aureus] [both methicillin susceptible [MSSA] and methicillin resistant [MRSA]. A total of 1072 gram positive bacterial isolates were tested. The majority was from swabs collected from outpatient clinics. Erythromycin resistance was 8/23 [35%] for S. pneumoniae, 12/91 [13%] for GAS and 17/300 [5.7%] for GBS. All GAS and viridans streptococci possessed the efflux phenotype only. 8[8.8%] and 1[20%], respectively. For GBS, cMLS[B] phenotype. Seventy five isolates [16.3%] of MSSA were resistant to erythromycin compared to 160[83%] of MRSA. The majority of MSSA, 31/460 [6.7%] had an efflux phenotype while 26/460 [5.6%] were of cMLS[B] and 19/460[4%] iMLS[B] phenotypes. Constitutive MLS[B] was the most predominant resistant phenotype, 152/193 [78.8%] among MRSA. D-test zone should be considered for routine testing to detect inducible clindamycin resistance among significant gram positive bacteria