Phenotypic and molecular characterization of inducible clindamycin resistance among Staphylococcal strains isolated from cancer patients with febrile neutropenia

This work aimed at the phenotypic and molecular characterization of inducible clindamycin resistance among strains of Staphylococcus aureus isolated from cancer patients with febrile neutropenia. Out of 231clinical specimens Staphylococci were isolated from 179 (77.48%) cases. Isolates were identified by conventional microbiological methods. Antimicrobial sensitivity to all isolates was done using disc diffusion methods. For strains that were erythromycin resistant, D-test was performed to screen the presence of inducible clindamycin resistance. Multiplex polymerase chain reaction (multiplex-PCR) was done for strains with constitutive or inducible resistance to detect the distribution of erm (e), and erm (C) genes. Out of 231 clinical specimens, staphylococci were isolated from 179 (77.48%). Staphylococcal isolates were tested for susceptibility to erythromycin; 100 (55.8%) of them were erythromycin resistant. of these 100, erythromycin resistant isolates (8, 4.46%) were resistant to both erythromycin and clindamycin indicating constitutive MLSB Phenotype; 92 isolates were erythromycin resistant, and clindamycin sensitive. Out of these, 45 (25.1%) isolates showed positive D test indicating inducible MLSB phenotype while 47(26.2%) gave negative D test indicating MS phenotype. Molecular study revealed that 8 strains (100%) of staphylococci with constitutive MLSB phenotype and 23 strains (51.1%) of staphylococci with inducible MLSB phenotype had both erm(e) and erm(c) gene, erm (e) gene was present in 33.3% and erm (c) gene present in 15.6% of staphylococcus isolates with inducible MLS B phenotype. Inducible resistance and MS phenotype were found to be higher in MRSA as compared to MSSA (27.6, 24.3 and 1.6 and 4% respectively). Rapid dissemination of inducible clindamycin-resistant S. aureus isolates is worrisome and calls for judicious use of antibiotics. Therefore, the D-test should be added as a routine procedure on each staphylococcal isolates to detect inducible clindamycin resistance to avoid failure of antibiotic therapy.