ABSTRACT
Background: Infections by Gram positive isolates are increasing due to which their antibiotic sensitivity pattern is changing. This has revived interest in Macrolide-Lincosamide Streptogramin Group B (MLSB) antibiotics. Misuse of MLSB antibiotics hasincreased resistance in Gram-positive organisms especially Staphylococcus species to these drugs. Clindamycin is an important drug for treatment of Gram-positive isolates. Hence detection of inducible clindamycin resistance in these clinical isolates is required to prevent therapeutic failure and avoid inadvertent use of this drug. Aim and Objectives: To detect inducible clindamycin resistance among Gram positive isolates obtained from clinical samples. Material and Methods: The study was carried out over a period of one year (Jan-Dec 2018). A total of 461 Gram positive isolates of Staphylococcus species, Streptococcus pneumoniae and Beta-haemolytic Streptococcus were identified from various clinical samples and antibiotic susceptibility done on Vitek2 Compact usi g GP ID, and 628 and ST01 cards respectively. According to CLSI 2017, D-zone test was performed for detection of inducible clindamycin resistance for strains resistant to erythromycin. Results: Staphylococcus aureus (SA) isolates were 59%, Staphylococcus epidermidis (SE) 21%, other Coagulase Negative Staphylococcus (CONS) 16%, Streptococcus pyogenes (Group A-beta haemolytic) 2%, Streptococcus agalactiae (Group B betahaemolytic) 1% and Streptococcus pneumoniae (alpha haemolytic) 1%. Isolates of Methicillin Sensitive Staphylococcus aureus (MSSA) were 58% and Methicillin Resistant Staphylococcus aureus (MRSA) were 42%. Frequencies of MS (clindamycin sensitive) phenotypes, inducible clindamycin resistance (MLSBi) phenotypes and phenotypes showing constitutive resistance (MLSBc) were 44%, 12% and 3% respectively among MSSA and 34%, 39% and 8% respectively among MRSA. Among SE, MS, MLSBc and MLSBi phenotypes were 39%, 24% and 12% respectively and 8%, 44% and 30% respectively among other CONS. One isolate of S. pyogenes was of MLSBi phenotype and none among S. agalactiae and S. pneumoniae. Conclusion: The study emphasizes the significance of conducting D-zone test along with routine antimicrobial susceptibility testing to guide in therapy and avoid treatment failures.
ABSTRACT
Antihistaminics are widely used for various indications during microbial infection. Hence, this paper investigates the antimicrobial activities of 10 antihistaminics belonging to both old and new generations using multiresistant Gram-positive and Gram-negative clinical isolates. The bacteriostatic activity of antihistaminics was investigated by determining their MIC both by broth and agar dilution techniques against 29 bacterial strains. Azelastine, cyproheptadine, mequitazine and promethazine were the most active among the tested drugs. Diphenhydramine and cetirizine possessed weaker activity whereas doxylamine, fexofenadine and loratadine were inactive even at the highest tested concentration (1 mg/ml). The MIC of meclozine could not be determined as it precipitated with the used culture media. The MBC values of antihistaminics were almost identical to the corresponding MIC values. The bactericidal activity of antihistaminics was also studied by the viable count technique in sterile saline solution. Evident killing effects were exerted by mequitazine, meclozine, azelastine and cyproheptadine. Moreover, the dynamics of bactericidal activity of azelastine were studied by the viable count technique in nutrient broth. This activity was found to be concentration-dependant. This effect was reduced on increasing the inoculum size while it was increased on raising the pH. The post-antimicrobial effect of 100 fg/ml azelastine was also determined and reached up to 3.36 h.