A cross-sectional epidemiological investigation of nontuberculous mycobacteria of public health importance in slaughter camels in Samburu County, Kenya.

The diagnosis of tuberculosis (TB) in camels at slaughter houses heavily relies on post mortem (PM) meat inspection to detect granulomatous lesions; however, the sensitivity of this technique is not perfect. The objective of this study was to isolate and characterize mycobacteria associated with suspect TB pathological lesions at PM. At PM, 1600 camels were examined in two county slaughterhouses. One hundred and thirty two, 8.25% (132/1600) (Binomial CI 95% 6.95-9.71%), suspect granulomatous lesions were found. Twenty seven, 1.69% (27/1600) (Binomial CI 95% 1.11-2.45%), were confirmed as acid-fast bacilli (AFB) using Ziehl-Neelsen (ZN) staining after culture. Speciation using the GenoType® Mycobacterium assay (Hain Lifesciences, Nehren, Germany) found a majority isolates to be Mycobacterium fortuitum (17), the other species identified included M. szulgai (2), M. scrofulaceum (3), M. marinum (1), M. intracellulare (1), M. gordonae (1), and 2 unidentified mycobacteria species. The types of lesions observed were nodular, caseous masses involving whole organs or cavities, and purulent masses. The highest proportion of suspect lesions were observed in the right, left bronchial lymph nodes, and the mediastinal lymph nodes (59.54%), followed by the retropharyngeal lymph nodes (12.21%), the medial lobe (10.67%), and the left lateral and quadrate lobes of the lungs (17.58%). The 6-7 age category had higher odds (OR = 2.5) of culture positivity. It was concluded that a variety of NTM species of medical importance were associated with TB lesions in the thoracic lymph nodes and lungs. There is need to unravel the public health significance of these mycobacteria.

High prevalence of pulmonary tuberculosis and inadequate case finding in rural western Kenya.

RATIONALE: Limited information exists on the prevalence of tuberculosis and adequacy of case finding in African populations with high rates of HIV. OBJECTIVES: To estimate the prevalence of bacteriologically confirmed pulmonary tuberculosis (PTB) and the fraction attributable to HIV, and to evaluate case detection. METHODS: Residents aged 15 years and older, from 40 randomly sampled clusters, provided two sputum samples for microscopy; those with chest radiograph abnormalities or symptoms suggestive of PTB provided one additional sputum sample for culture. MEASUREMENTS AND MAIN RESULTS: PTB was defined by a culture positive for Mycobacterium tuberculosis or two positive smears. Persons with PTB were offered HIV testing and interviewed on care-seeking behavior. We estimated the population-attributable fraction of HIV on prevalent and notified PTB, the patient diagnostic rate, and case detection rate using provincial TB notification data. Among 20,566 participants, 123 had PTB. TB prevalence was 6.0/1,000 (95% confidence interval, 4.6-7.4) for all PTB and 2.5/1,000 (1.6-3.4) for smear-positive PTB. Of 101 prevalent TB cases tested, 52 (51%) were HIV infected, and 58 (64%) of 91 cases who were not on treatment and were interviewed had not sought care. Forty-eight percent of prevalent and 65% of notified PTB cases were attributable to HIV. For smear-positive and smear-negative PTB combined, the patient diagnostic rate was 1.4 cases detected per person-year among HIV-infected persons having PTB and 0.6 for those who were HIV uninfected, corresponding to case detection rates of 56 and 65%, respectively. CONCLUSIONS: Undiagnosed PTB is common in this community. TB case finding needs improvement, for instance through intensified case finding with mobile smear microscopy services, rigorous HIV testing, and improved diagnosis of smear-negative TB.

Isolation, identification and associated risk factors of non-tuberculous mycobacteria infection in humans and dromedary camels in Samburu County, Kenya.

Non-tuberculous mycobacteria are of public health significance, and zoonotic infection is attributed to the sociocultural practice of consumption of raw milk and the close human-livestock contact in pastoral communities. This study aimed at isolation, identification of mycobacteria from human sputum and camel milk and risk factors assessment in Samburu East, Kenya. Six hundred and twelve camels and 48 people presumed to have tuberculosis (TB) from 86 households in Wamba and Waso regions were screened. Camels were categorized into Somali, Turkana and Rendile breeds. Single intradermal comparative tuberculin test (SICTT) was used as a herd-screening test on lactating camels and a milk sample collected from reactive camels. Sputum samples were collected from eligible members of participating households. A standard questionnaire on possible risk factors for both humans and camels was administered to respective household heads or their representatives. Total camel skin test reactors were 238/612 (38.9%). Milk and sputum samples were analysed at KEMRI/TB research laboratory for microscopy, GeneXpert® , culture and identification. Isolates were identified using 16S rRNA gene sequencing at Inqaba biotec in South Africa. Sixty-four isolates were acid-fast bacilli (AFB) positive of which M. fortuitum (3), M. szulgai (20), M. monacense (5), M. lehmanni (4), M. litorale (4), M. elephantis (3), M. duvalii (3), M. brasiliensis (1), M. arcueilense (1) and M. lentiflavum (1) were from milk; M. fortuitum (1), M. szulgai (2) and M. litorale (1) were from humans. Risk factors included the following: Turkana breed (OR = 3.4; 95% CI: 1.2-9.3), replacements from outside the County (OR = 2.1; 95% CI: 0.3-12.3), presence of other domestic species (small stock; OR = 4.6) and replacement from within the herd (OR = 3.2; 95% CI: 0.7-14.7). Zoonotic risk practices included raw milk consumption, shared housing and handling camels. Monitoring of zoonotic NTM through surveillance and notification systems is required.

Bleach sedimentation: an opportunity to optimize smear microscopy for tuberculosis diagnosis in settings of high prevalence of HIV.

BACKGROUND: The purpose of the study was to evaluate the performance and feasibility of tuberculosis diagnosis by sputum microscopy after bleach sedimentation, compared with by conventional direct smear microscopy, in a setting of high prevalence of HIV. METHODS: In a community-based study in Kenya (a population in which 50% of individuals with tuberculosis are infected with HIV), individuals with suspected pulmonary tuberculosis submitted 3 sputum specimens during 2 consecutive days, which were examined by blind evaluation. Ziehl-Neelsen-stained smears were made of fresh specimens and of specimens that were processed with 3.5% household bleach followed by overnight sedimentation. Two different cutoffs for acid-fast bacilli (AFB) per 100 high-power fields (HPF) were used to define a positive smear: >10 AFB/100 HPF and 1 AFB/100 HPF. Four smear-positive case definitions, based on 1 or 2 positive smears with the 1 AFB or 10 AFB cutoff, were used. RESULTS: Of 1879 specimens from 644 patients, 363 (19.3%) and 460 (24.5%) were positive by bleach sedimentation microscopy, compared with 301 (16.0%) and 374 (19.9%) by direct smear microscopy, with use of the 10 AFB/100 HPF (P < .001) and 1 AFB/100 HPF (P < .001) cutoffs, respectively. Regardless of the case definition used, bleach sedimentation microscopy detected significantly more positive cases than did direct smear microscopy: 26.7% (172 of 644) versus 21.7% (140 of 644), respectively, with the case definition of 1 positive smear and the 1 AFB/100 HPF cutoff (P < .001), and 21.4% (138 of 644) versus 18.6% (120 of 644), respectively, with the case definition of 1 positive smear and the 10 AFB/100 HPF cutoff (P < .001). Inter- and intrareader reproducibility were favorable, with kappa coefficients of 0.83 and 0.91, respectively. Bleach sedimentation was relatively inexpensive and was not time consuming. CONCLUSIONS: Bleach sedimentation microscopy is an effective, simple method to improve the yield of smear microscopy in a setting of high prevalence of HIV. Further evaluation of this method, under operational conditions, is urgently needed to determine its potential as a tool for tuberculosis control.

Building Cross-Country Networks for Laboratory Capacity and Improvement.

Laboratory networks are vital to well-functioning public health systems and disease control efforts. Cross-country laboratory networks play a critical role in supporting epidemiologic surveillance, accelerating disease outbreak response, and tracking drug resistance. The East Africa Public Health Laboratory Network was established to bolster diagnostic and disease surveillance capacity. The network supports the introduction of regional quality standards; facilitates the rollout and evaluation of new diagnostic tools; and serves as a platform for training, research, and knowledge sharing. Participating facilities benefitted from state-of-the art investments, capacity building, and mentorship; conducted multicountry research studies; and contributed to disease outbreak response.

Screening strategies for tuberculosis prevalence surveys: the value of chest radiography and symptoms.

BACKGROUND: We conducted a tuberculosis (TB) prevalence survey and evaluated the screening methods used in our survey, to assess if screening in TB prevalence surveys could be simplified, and to assess the accuracy of screening algorithms that may be applicable for active case finding. METHODS: All participants with a positive screen on either a symptom questionnaire, chest radiography (CXR) and/or sputum smear microscopy submitted sputum for culture. HIV status was obtained from prevalent cases. We estimated the accuracy of modified screening strategies with bacteriologically confirmed TB as the gold standard, and compared these with other survey reports. We also assessed whether sequential rather than parallel application of symptom, CXR and HIV screening would substantially reduce the number of participants requiring CXR and/or sputum culture. RESULTS: Presence of any abnormality on CXR had 94% (95%CI 88-98) sensitivity (92% in HIV-infected and 100% in HIV-uninfected) and 73% (95%CI 68-77) specificity. Symptom screening combinations had significantly lower sensitivity than CXR except for 'any TB symptom' which had 90% (95%CI 84-95) sensitivity (96% in HIV-infected and 82% in HIV-uninfected) and 32% (95%CI 30-34) specificity. Smear microscopy did not yield additional suspects, thus the combined symptom/CXR screen applied in the survey had 100% (95%CI 97-100) sensitivity. Specificity was 65% (95%CI 61-68). Sequential application of first a symptom screen for 'any symptom', followed by CXR-evaluation and different suspect criteria depending on HIV status would result in the largest reduction of the need for CXR and sputum culture, approximately 36%, but would underestimate prevalence by 11%. CONCLUSION: CXR screening alone had higher accuracy compared to symptom screening alone. Combined CXR and symptom screening had the highest sensitivity and remains important for suspect identification in TB prevalence surveys in settings where bacteriological sputum examination of all participants is not feasible.

Evaluation of combined LED-fluorescence microscopy and bleach sedimentation for diagnosis of tuberculosis at peripheral health service level.

BACKGROUND: Sputum microscopy is the only diagnostic for tuberculosis (TB) available at peripheral levels of health service in resource-poor countries. Its sensitivity is reduced in high HIV-prevalence settings. Sodium hypochlorite (NaOCl) specimen sedimentation prior microscopy and light-emitting diode (LED)-fluorescence microscopy (FM) can individually improve performance of microscopy. This study aimed to evaluate the performance of combined LED-FM and NaOCl sputum sedimentation for TB detection at peripheral level of health services. METHODS: A prospective study was conducted in an urban health clinic in Nairobi, Kenya. Three sputum specimens were collected over 2 days from consecutive TB suspects. Smears were prepared and stained with auramine O and Ziehl-Neelsen (ZN) methods. Bleach (3.5%) was added to the remaining specimen before overnight sedimentation at room temperature. Auramine O staining was performed on smears of sediment. A 4(th) specimen was collected for TB culture. Auramine smears were read under the same microscope as used for ZN smears, but equipped with the LED FluoLED™ fluorescence illuminator. RESULTS: 497 patients were included, and 1394 specimens collected. The yield of positive specimen was significantly increased after NaOCl sedimentation (24.9%) compared to direct LED-FM (20.6%) and direct ZN (20.3%). In detecting smear-positive patients, sensitivity was 78.5% for LED-FM after NaOCl sedimentation compared to 73.2% and 72.0% for direct LED-FM (P = 0.06) and direct ZN (P = 0.06), respectively. Specificity was 87.8% for LED-FM after NaOCl sedimentation compared to 96.7% and 95.9% for direct LED-FM (P<0.01) and direct ZN (P<0.01), respectively. Inter-reading agreement (kappa = 0.7) and technicians' acceptability were good. CONCLUSION: NaOCl sedimentation did not improve the performance of LED-FM in the diagnosis of pulmonary TB at peripheral health service level.

Performance of LED-based fluorescence microscopy to diagnose tuberculosis in a peripheral health centre in Nairobi.

BACKGROUND: Sputum microscopy is the only tuberculosis (TB) diagnostic available at peripheral levels of care in resource limited countries. Its sensitivity is low, particularly in high HIV prevalence settings. Fluorescence microscopy (FM) can improve performance of microscopy and with the new light emitting diode (LED) technologies could be appropriate for peripheral settings. The study aimed to compare the performance of LED-FM versus Ziehl-Neelsen (ZN) microscopy and to assess feasibility of LED-FM at a low level of care in a high HIV prevalence country. METHODS: A prospective study was conducted in an urban health clinic in Nairobi, Kenya. Three sputum specimens were collected over 2 days from suspected TB patients. Each sample was processed with Auramine O and ZN methods and a 4(th) specimen was collected for TB culture reference standard. Auramine smears were read using the same microscope, equipped with the FluoLED™ fluorescence illuminator. Inter-reader agreement, reading time and technicians' acceptability assessed feasibility. RESULTS: 497 patients were included and 1394 specimens were collected. The detection yields of LED-FM and ZN microscopy were 20.3% and 20.6% (p = 0.64), respectively. Sensitivity was 73.2% for LED-FM and 72% for ZN microscopy, p = 0.32. It was 96.7% and 95.9% for specificity, p = 0.53. Inter-reader agreement was high (kappa = 0.9). Mean reading time was three times faster than ZN microscopy with very good acceptance by technicians. CONCLUSIONS: Although it did not increase sensitivity, the faster reading time combined with very good acceptance and ease of use supports the introduction of LED-FM at the peripheral laboratory level of high TB and HIV burden countries.

Comparison of PCR with the routine procedure for diagnosis of tuberculosis in a population with high prevalences of tuberculosis and human immunodeficiency virus.

Direct smear examination with Ziehl-Neelsen (ZN) staining for the diagnosis of tuberculosis (TB) as employed in most low-income countries is cheap and easy to use, but its low sensitivity is a major drawback. The low specificity of chest X-rays, used for the diagnosis of smear-negative TB, risks high levels of overdiagnosis. Major advances in molecular techniques, which rapidly identify mycobacterial DNA in sputa, may overcome these obstacles. In this study, the AMPLICOR PCR system was used to diagnose pulmonary TB in a developing country with high prevalences of both TB and human immunodeficiency virus (HIV). The sensitivity and specificity of this technique were compared to those of the usual diagnostic techniques. Sputum specimens were collected from 1,396 TB suspects attending the Rhodes Chest Clinic, Nairobi, Kenya. The specimens were analyzed for the presence of Mycobacterium tuberculosis by PCR; culture on Löwenstein-Jensen medium was used as the "gold standard." All culture-positive samples were genotyped to identify the mycobacterial species. The sensitivity and specificity of PCR were 93 and 84%, respectively. HIV status did not affect the sensitivity of PCR. A total of 99.7% of the true smear-positive and 82.1% of the true smear-negative TB patients were correctly identified by PCR. PCR detected M. tuberculosis in 11.7% of the culture-negative suspects, 60% of which had one or two PCR-positive sputum specimens. Of the 490 positive cultures, 486 were identified as M. tuberculosis. The high sensitivity of Amplicor PCR merits usage in a clinical setting with high TB and HIV burdens. Thus, PCR can be considered as an alternative to ZN staining in combination with chest X-ray for diagnosis of TB; however, cost-effectiveness studies and operational studies are required to support an evidence-based decision of introducing PCR for TB control in high-burden environments.