Background. This study aimed to determine the pattern of drug susceptibility to first-line drugs among pulmonary TB patients in two hospitals in Calabar, Nigeria. Methods. This was a descriptive cross-sectional study carried out between February 2011 and April 2012. Sputum samples from consecutive TB patients in Calabar were subjected to culture on Lowenstein-Jensen (LJ) slopes followed by drug susceptibility testing (DST). The DST was performed on LJ medium by the proportion method. Results. Forty-two of the 100 Mycobacterium tuberculosis strains were found to be resistant to at least one drug. Resistance to only one drug (monoresistance) was found in 17 patients. No strains with monoresistance to rifampicin were found. Resistance to two drugs was found in 22 patients, while one patient was resistant to both three and four drugs. MDR TB was seen in 4% (4/100). The independent variables of HIV serology and sex were not significantly associated with resistance ( ). Conclusion. There was a high prevalence of anti-TB drug resistance in Calabar. 1. Introduction Tuberculosis (TB), an ancient infectious disease caused by Mycobacterium tuberculosis, is the leading cause of death due to an infectious agent globally. It is both preventable and treatable [1, 2]. The World Health Organization (WHO) records an average of nine million new TB cases annually and about 5000？TB deaths daily [1]. TB and human immunodeficiency virus (HIV) coinfection and the exponential increase in drug resistance are greatly responsible for the resurgence of TB [3]. Other identified factors include neglect of TB control by governments, poor management of programmes, poverty, population growth, and rapid uncontrolled urbanization [4]. Drug-resistant TB is a case of TB (usually pulmonary) excreting bacilli resistant to one or more anti-TB drugs [5]. Acquired drug resistance results from exposure to a single drug due to irregular drug supply, inappropriate prescription, or poor adherence to treatment. This suppresses the growth of bacilli susceptible to that drug while permitting multiplication of drug-resistant organisms. Primary or initial drug resistance occurs when such drug resistant bacilli are transmitted to other people [5]. Resistance to one anti-TB drugs is known as mono resistance. Poly resistance is resistant to two or more anti-TB drugs, but not to both isonazid & rifampicin. Multidrug-resistant TB (MDR TB) is resistant to at least isoniazid and rifampicin, the two key first-line anti-TB drugs in short course chemotherapy [5]. These forms of TB do not respond to the standard
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