Microbiological studies on resistance patterns of antimicrobial agents among Gram negative respiratory tract pathogens

Abstract

Respiratory tract infections (RTIs) are the most frequently-occurring infections of all human diseases and have been frequently documented. This study investigated the antimicrobial resistance patterns among Gram negative respiratory tract isolates. A total of 309 non replicate Gram negative respiratory tract isolates were collected and identified. Molecular mechanisms of antimicrobial resistance pattern were characterized by phonotypic and genotypic methods including polymerase chain reaction (PCR) amplification and DNA sequencing of isolated genes. Gram negative isolates were Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Stenotrophomonas maltophilia, Escherichia coli, Enterobacter cloacae, Serratia rubidaea, Haemophilus influenza, Citrobacter koseri, Moraxella catarrhalis, Proteus mirabilis and Salmonella typhimurium with the following frequencies respectively (34.6, 26.6, 13.9, 7.7, 6.4, 5.5, 1.4, 1.3, 1, 1, 0.3 and 0.3%). S. maltophilia isolates were the highest that produced extended spectrum beta lactamase (ES beta L) with percentage of 75% and metallo beta lactamase (M beta L) with percentage of 71%, while P. aeruginosa isolates were the highest that produced class C beta lactamase (AmpC) with percentage of 86% and efflux pump with percentage of 73%. This study revealed two common mechanisms of antimicrobial resistance patterns, beta -lactamases production and efflux pump, among Gram negative respiratory tract pathogens up to molecular level.