Phenotypic Drug Susceptibility Patterns of Mycobacterium tuberculosis Isolates to First-Line Anti-Tuberculosis Drugs in South-Western Nigeria
R. Warrens *
Department of Microbiology, Novena University, Ogume, Delta State, Nigeria.
C. S. O. Otoikhian
Department of Microbiology, Novena University, Ogume, Delta State, Nigeria.
S. C. Akpeji
Department of Microbiology, Novena University, Ogume, Delta State, Nigeria.
B. O. Bosah
Department of Microbiology, Novena University, Ogume, Delta State, Nigeria.
D. S. Elkanah
Department of Public Health Science, Taraba State University, Jalingo, Taraba State, Nigeria.
C. C. Otali
Department of Microbiology, Novena University, Ogume, Delta State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Drug-resistant tuberculosis (TB) undermines global TB control efforts, yet comprehensive phenotypic drug susceptibility data from South-Western Nigeria remain limited. Understanding local resistance patterns is essential for optimising treatment regimens and informing programmatic responses. This study aimed to determine the phenotypic susceptibility patterns of culture-confirmed Mycobacterium tuberculosis isolates to first-line anti-tuberculosis drugs among patients in South-Western Nigeria. Seventy-four GeneXpert MTB/RIF-positive sputum specimens from patients attending health facilities in Osun, Oyo, and Lagos States underwent mycobacterial culture on Löwenstein-Jensen medium. Culture-confirmed M. tuberculosis isolates were subjected to phenotypic drug susceptibility testing against rifampicin, isoniazid, and ethambutol using the proportion method. Of 74 GeneXpert-positive specimens cultured, 51 (68.9%) yielded M. tuberculosis. Among these 51 isolates, 36 (70.6%) demonstrated resistance to at least one first-line drug. Rifampicin resistance was detected in 27 isolates (52.9%), isoniazid resistance in 18 (35.3%), and ethambutol resistance in 13 (25.5%). Fifteen isolates (29.4%) met criteria for multidrug-resistant TB (MDR-TB), defined as combined rifampicin and isoniazid resistance. Analysis of the geographical distribution revealed that 74.1% of rifampicin-resistant, 77.8% of isoniazid-resistant, and 84.6% of ethambutol-resistant isolates originated from Osun State. Substantial resistance to first-line anti-tuberculosis drugs, particularly rifampicin, was detected among culture-confirmed M. tuberculosis isolates in South-Western Nigeria. The high prevalence of drug resistance and MDR-TB highlights the need for routine culture and drug susceptibility testing to guide individualized treatment and prevent treatment failure.
Keywords: Mycobacterium tuberculosis, drug resistance, phenotypic susceptibility testing, first-line drugs, multidrug-resistant tuberculosis