Susceptibility and Detection of Extended Spectrum β-Lactamase Enzymes from Otitis Media Pathogens

Otitis media is the bacterial infection of the middle ear usually accompanied with inflammation, effusions and pain. It can present clinically in two major forms: Acute Otitis Media (AOM) and Otitis Media with Effusion (OME) and it is one of the leading cause of hospital visits and antibiotic prescriptions amongst children and even adults. Antibiotic resistance is a global public health problem and Extended Spectrum β-Lactamase (ESBL) enzymes is one of the new mechanisms of resistance in especially Gram negative bacteria including Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. ESBLs are plasmid-mediated β-lactamase enzymes that hydrolyze extended-spectrum oxyimino 3rd generation cephalosporins and monobactams. Organisms producing ESBLs have remained important nosocomial and community-acquired pathogens over the years. Ear swab specimens of children (aged 0-7) with suspected Otitis media infections and who attended a tertiary hospital in Enugu, Nigeria were cultured on growth media. E. coli, K. pneumoniae and P. aeruginosa were isolated and identified by standard microbiological techniques. Antibiogram was conducted on all isolated ear pathogens by Kirby-Bauer disk diffusion method and ESBL production was evaluated by the Double Disk Synergy Test (DDST) method. Imipenem and meropenem were the most active antibiotics against the E. coli, K. pneumoniae and P. aeruginosa ear pathogens. Sulphamethoxazole-trimethoprim was the least active agent against the tested ear pathogens and this was followed by ofloxacin, ciprofloxacin, gentamicin, cefotaxime and ceftazidime. None of the E. coli, K. pneumoniae and P. aeruginosa ear pathogens produced ESBLs by the method used. ESBL production by pathogenic bacteria confers on organisms the ability to be multidrug resistant. Their prompt and accurate detection from clinical specimens, together with reporting them along with hospitals routine antibiogram results is vital as this will help to guide therapy and forestall any treatment failure in the face of an ESBL infection.