The Use of the PCR-Based Dot-Blot Hybridization Assay to Detect Resistance Markers to Rifampicin and Streptomycin in Mycobacterium tuberculosis Isolates from the SW Region of Cameroon

Drug sensitivity testing to establish resistance to TB drugs takes many months to arrive at. Public health physicians have difficulties with such an approach due to long wait periods and cannot use it to establish community wide prevalence as a way to understand where resistance may be emerging faster and to limit its spread. The objective of this study was to use the dot-blot hybridization technique in the detection of resistance to rifamycin (RIF) and streptomycin (SM) in South- Western Cameroon and to compare the technique with the routine culture and drug susceptibility testing for detecting resistance in a resource poor country, Cameroon. A hospital-based study was conducted at the Regional hospitals of Buea and Limbe and Tiko Central Clinic. Tuberculosis (TB) patients aged 15 to 50 (mean age: 30.50 ± 8.33 standard deviation) were recruited for the study between December 2006 and April 2007. Cultures from 59 patients were tested for rifampicin and streptomycin sensitivity by the modified proportion method and mutational analysis for rpoB codon 516 and rrs codon 513 was performed by the dot-blot hybridization technique. Of the 59 sputum samples collected (36 were males and 23 were females) came from Buea 19 (32.2%), Limbe 20 (33.9%) and Tiko 20 (33.9%) towns respectively. Amplification for the gene showed that there was (59) 100% amplification with primers used for rpoB genes and 43 (72.9%) amplification with primers used for the rrs gene. Mutational analysis demonstrated that resistance to RIF was common in females (52.1%) than males (41.7%) while 6% of the samples were indeterminate. 12 (20.3%) samples showed phenotypic and genotypic resistance to RIF compared to 34 samples (58.1%) for SM. Phenotypic resistance and genotypic susceptibility were found in 5 (8.5%) RIF and 3 (4.7%) SM compared to phenotypic susceptibility and genotypic resistance that were found in 2 (3.5%) RIF and 3(4.7%) SM. Double mutation on rpoB and rrs genes occurred in 8 (13.6%) DNA samples. Resistance to RIF and SM due to mutations on the rpoB and rrs genes respectively in the SW region was found to be high and comparable to the drug susceptibility testing by 92%, (95% CI: 75.7 - 99.1). The Dot-blot technique will be useful in rapidly assessing the effectiveness of national TB control programs in limiting the spread of resistance strains in Cameroon.

Immuno-haematologic and virologic responses and predictors of virologic failure in HIV-1 infected adults on first-line antiretroviral therapy in Cameroon

Background:Contemporary data on the immunologic,haematologic and virologic responses and predictors of virologic failure after initiation of free antiretroviral treatment in Cameroon are needed to evaluate the current treatment-monitoring algorithm and to complement efforts to scale-up and improve on the management of HIV infections.Methods:This was a cross-sectional study conducted between October 2010 and June 2012.A total of 951 participants aged 18-74 years were recruited from selected approved HIV treatment centres of the Northwest and Southwest regions.This comprised 247 males and 704 females.Demographic,self-reported risk behaviours and socioeconomic data were obtained using a structured questionnaire.Full blood and CD4+T-cell counts were done using standard automated techniques.Determination of viral load(VL)was done using Abbott RealTime HIV-1 m2000™system.Data was analysed using SPSS version 17.The statistical significance level was P<0.05.Results:The median duration of antiretroviral therapy(ART)was 24 months.The population mean CD4+T-cell count was 255.3 cells/μL[95%CI,236.8-273.9].Overall,45.9%,43.8%and 10.2%of the participants had CD4+T-cell counts of<200 cells/μL,200-499 cells/μL and>500 cells/μL respectively.Anaemia was present in 26.2%of the participants with 62.3%,25.7%and 12%described as mild,moderate and severe anaemia respectively.Virologic failure occurred in 23.2%of the participants with 12.3%having VL>10,000 RNA copies/mL.Meanwhile 76.8%of patients attained adequate viral suppression with 40.8%having undetectable viral load.The age group 18-29 years(p=0.024),co-infection with tuberculosis(p=0.014),anaemia(p=0.028)and distance from the treatment centre(p=0.011)independently predicted virologic failure.Conclusion:The majority of the participants achieved adequate viral suppression after≥6 months of ART.Despite these favourable immuno-haematologic and virologic outcomes,the National AIDS Control Program should step-up efforts to improve on antiretroviral drug distribution,as well as proper assessment and management of anaemia,foster early diagnosis and treatment of tuberculosis and enhance treatment adherence counselling especially in younger patients.