“Bacterial aetiology in the lower respiratory tract of TB-negative patients with respiratory symptoms: implications for tuberculosis control in Ghana”

Abstract

Patients with tuberculosis-negative respiratory symptoms may have other bacterial infections that could complicate diagnosis and treatment decisions. However, the microbiological profile and associated clinical factors in this group are not well understood in Ghana. This study aimed to determine the prevalence and characterise bacterial isolates in TB-negative patients in Ghana. We conducted a cross-sectional study involving 114 TB-negative patients. Sputum samples were subjected to mycobacterial culture and bacterial culture on blood agar and MacConkey agar. The bacterial growth patterns were analysed and the isolates were characterised using Gram staining alongside their biochemical profiles (catalase, coagulase, and oxidase) and commercial systems (API 20E/20NE, Streptococcus grouping kit, Vitek 2 Compact systems). Associations between bacterial isolates and patient characteristics were assessed using chi-square to compare proportions. The mycobacterial culture performed confirmed that all recruited study participants were MTB-negative, with two being classified as having suspected non-tuberculous mycobacteria. Bacterial isolates were obtained from 61 patients’ specimen (53.5%). Gram-positive bacteria were predominant (71/86, 82.6%), with Streptococcus pneumoniae being the most common (22/71, 31.0%). Other bacteria isolated included Staphylococcus aureus (9/71, 12.7%), coagulase-negative Staphylococcus species (14/71, 19.7%) and Micrococcus species (11/71, 15.5%). Gram-negative bacteria accounted for 10.5% (9/86) of isolates, mainly Klebsiella pneumoniae subsp. pneumoniae (4/9, 44.4%), Acinetobacter baumannii (2/9, 22.2%), and Pseudomonas aeruginosa (1/9, 11.1%). Polymicrobial growth was observed in 27.9% (17/61) of the positive cultures. This study reveals a diverse bacterial aetiology in the sputum of TB-negative patients, with a predominant presence of Gram-positive organisms. These findings highlight the critical need for comprehensive microbiological evaluation to guide targeted antimicrobial therapy and prevent inappropriate anti-TB medications in settings with high TB burden.