Bacterial Etiology of Lower Respiratory Tract Infections and Their Antimicrobial Susceptibility

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Lower respiratory tract infection (LRTI) is one of the common major health problems in Nigeria causing morbidity and mortality. The study was conducted to determine the current trends of bacterial etiology of LRTIs among patients who attended the University of Nigeria Teaching Hospital (UNTH) and their antimicrobial susceptibility profile with special interest on pandrug resistance.

Materials and Methods:

The study was conducted between February 2014 and June 2016 in the bacteriology laboratory of UNTH. Sputum samples of 954 patients with suspected LRTIs were received, after obtaining patients’ informed consent and ethical clearance from the UNTH. The samples were collected and processed according to standard laboratory procedures.


The mean age of the patients was 42.6 ± 16.8 years. Of the total 954 sputum samples, 431 (45.2%) were positive for micro-organisms. A single, unique pathogen was recovered in 415 patients (96.3%), and 16 (3.7%) were polymicrobial. The most predominant single pathogen was Klebsiella pneumoniae, 215 (49.9%), and the most prevalent bacterial combination was Klebsiella spp and Pseudomonas aeruginosa, 6 (1.4%). Antimicrobial susceptibility testing shows that most isolates of K pneumoniae were susceptible to imipenem (94.8%). Among the bacteria, Escherichia coli (13.3%) ranked highest, followed by P aeruginosa (12.5%), and the least was Staphylococcus aureus (2.1%).


Knowledge of the diversity of pathogens responsible for LRTIs and their susceptibility patterns to antibiotics, as well as antibiotic resistance surveillance, are important in the effective management of LRTI with prompt clinical and laboratory diagnosis along with appropriate treatment strategies.

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