Microbial Surveillance and Susceptibility of Gram-Positive Bacteria to Antibiotic Drugs

Abstract

Incidence of antimicrobial resistance among Gram-positive organisms has been increasing steadily to most of the currently available anti bacterials, making it extremely difficult to treat infections. Purpose of this study was to assess the epidemiology of infections caused by multi-drug resistant (MDR) Gram positive isolates in India and to survey response of antimicrobial agents to these strains. This study involved 408 Gram positive isolates including S. aureus (211), Methicillin-resistant Staphylococcus aureus (MRSA) (130), Staphylococcus epidermidis (15), Streptococcus pneumoniae (12), Streptococcus pyogenes (13), Streptococcus bovis (7), Streptococcus agalactiae (9) and Enterococcus faecalis (11) which were collected from different parts of India. Susceptibility study was performed by broth microdilution method as recommended by Clinical and laboratory standard institutes (CLSI). Our study revealed that Vancoplus is the most effective with > 90 % susceptibility to most of the pathogens like S. aureus, MRSA and S. epidermidis with MICs 0.0625-2 µg/ml followed by linezolid with ≤ 85 % susceptibility to the said pathogens with MICs 1-4 µg/ml. The susceptibility of other drugs varied between 19 to 84 %. Among streptococcus, the susceptibility of Vancoplus varied between 91 to 100% with MICs 0.3125 to 1 µg/ml whereas linezolid showed 66 to 84 % susceptibility with MICs 0.5-4 µg/ml. The susceptibility of other drugs ranged between 23 to 71 %. About 90.9 % E. faecalis isolates were susceptible to Vancoplus at 0.0625-4 µg/ml compared to 81.8% to Linezolid, around 72% to vancomycin, daptomycin and teicoplanin and only 27.3% to clindamycin In conclusion, Vancoplus demonstrated potent in vitro activity against Gram-positive staphylococcal, streptococcal and enterococcal isolates. The results of this surveillance study can serve as a benchmark for monitoring the in vitro activity of this new agent.