Secondary bacterial infection in active pulmonary tuberculosis

Abstract

Patients with pulmonary tuberculosis commonly have additional pathogens cultured in sputum, i.e. so-called potentially pathogenic bacteria. The significance of these organisms is uncertain. Previously, we demonstrated that the presence of potentially pathogenic bacteria in the sputum of a group of mainly human immunodeficiency virus (HIV)-seronegative tuberculosis patients was relatively uncommon. We wished to determine whether or not this was the same in a group of mainly HIV-seropositive patients. Patients admitted to Charlotte Maxeke Johannesburg Academic Hospital with sputum-positive tuberculosis and sputum for microscopy and culture were recruited between July 2011 and April 2012. Patient demographics, clinical investigations, sputum microbiological results and discharge data were reviewed. Twenty-five patients were recruited, 14 of whom were female. The median age was 30 years (a range of 19-63). Eighteen (72%) patients were HIV-infected, four HIV-uninfected and three of unknown HIV status. The median white cell count was 7.59 x 10⁹/l (a range of 1.79-17.61), the median C-reactive protein was 167 mg/l (a range of 27-292), and the median CD4 81 cells/µl (a range of 14-369). The median albumin in the potentially pathogenic bacteria-positive group was 26 g/l versus 28 g/l in the potentially pathogenic bacteria-negative group (p-value 0.5229). Nine (36%) of the patients had potentially pathogenic bacteria on sputum culture. 38.9% and 28.6% in the HIV-infected, and HIV-uninfected, groups, respectively, grew potentially pathogenic bacteria. Seven patients (77.7%) in the potentially pathogenic bacteria-positive group survived to hospital discharge, compared with 14 (87.5%) of the potentially pathogenic bacteria-negative group (p-value 0.6016). This study showed that a mainly HIV-infected group had a similar rate of potentially pathogenic bacteria in the sputum, when compared with a previous mainly HIV-uninfected group. This study suggests that secondary bacterial infection may be relatively uncommon in both HIV-infected and -uninfected patients with active pulmonary tuberculosis.