Browsing by Author "Mgode, G"

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APOPO’s tuberculosis research agenda: achievements, challenges and prospects
(2012-04) Beyene, N; Mahoney, A; Cox, C; Weetjens, B; Making, G; Mgode, G; Durgin, A; Kuipers, D; Jubitana, M; Egwaga, S; Kamala, D; Lwila, F; Mfinanga, S; Kahwa, A; Machangu, R; Kazwala, R; Reither, K; Kaufmann, S; Poling, A
This article describes Anti-Persoonsmijnen Ontmijnende Product Ontwikkeling (APOPO) recent use of specially trained African giant pouched rats as detectors of pulmonary tuberculosis in people living in Tanzania. It summarizes the achievements and challenges encountered over the years and outlines future prospects. Since 2008, second-line screening by the rats has identified more than 2000 tuberculosis-positive patients who were missed by microscopy at Direct Observation of Treatment – Short Course centres in Tanzania. Moreover, data that are reviewed herein have been collected with respect to the rats’ sensitivity and specificity in detecting tuberculosis. Findings strongly suggest that scent-detecting rats offer a quick and practical tool for detecting pulmonary tuberculosis and within the year APOPO’s tuberculosis-detection project will be extended to Mozambique. As part of its local capacity building effort, APOPO hires and trains Tanzanians to play many important roles in its TB detection project and provides research and training opportunities for Tanzanian students.
Determination of Mycobacterium tuberculosis odour compounds detected by Cricetomys gambianus rats for diagnosis of pulmonary tuberculosis in low-income settings
(2013) Mgode, G
Novel methods for rapid diagnosis of tuberculosis (TB) are urgently needed to complement the widely used smear microscopy in low income settings. Trained TB detection rats offer a promising tool for rapid diagnosis of TB in resource limited settings. The Mycobacterium tuberculosis (Mtb) specific volatile compounds detected by trained Cricetomys gambianus rats in sputum of TB patients are unknown. It is also not known whether rats detect odour signals from other mycobacteria and microorganisms related to Mtb, which cause pulmonary infections resembling TB. In this thesis I investigated Mtb-specific volatile compounds detected by trained rats and whether the target compounds are found in other mycobacterial species and related pulmonary pathogens. The ability of rats to discriminate cultures of different microorganisms, clinical sputa with different Mycobacterium spp., Mtb genotypes and other respiratory tract microorganisms was investigated. Finally, the ability of the rats to discriminate Mtb-specific odour compounds from shared compounds found in Mtb and other microorganisms was determined. Results show that Mtb produce specific volatile compounds which are not produced by other mycobacterial species, mycobacteria-related Nocardia spp. and Rhodococcus spp. and other microorganisms. Trained rats use these Mtb-specific compounds to distinguish TB-positive sputa from TB-negative sputa. Volatile compounds shared by Mtb and other mycobacteria and non-mycobacterial species are not detected by trained rats. A blend of Mtb-specific compounds is detected by rats better than individual compounds. Rats can discriminate cultures of Mtb from those of other microorganisms. Detection of Mtb cultures is influenced by growth stage. Rats detect more frequently TB-positive sputa than negative sputa spiked with Mtb or specific volatiles. Clinical sputa containing Mtb are well discriminated by rats from sputa containing other microorganisms. Sputa containing different Mtb genotypes are also detected. It is concluded that trained rats can reliably diagnose TB. Further studies are needed to determine the optimal combinations/ratios of Mtb-specific volatile compounds to yield similarly higher responses of rats as those of detection of typical TB-positive sputa. Future studies should assess detection of sputa with frequent nontuberculous mycobacterial species. Further investigations including recovery of dormant Mtb in sputum may give insights on actual cause of detection of false positive sputa currently judged by microscopy and conventional Mtb culture in which dormant Mtb cannot grow.
Diagnosis of tuberculosis by trained African Giant Pouched Rats and confounding impact of pathogens and microflora of the respiratory tract
(American Society for Microbiology, 2012-11-30) Mgode, G; Weetjens, B; Nawrath, T; Cox, C; Jubitana, M; Machang’u, R; Cohen-Bacrie, S; Bedotto, M; Drancourt, M; Schulz, S; Kaufmanna, S
Trained African giant-pouched rats (Cricetomys gambianus) can detect Mycobacterium tuberculosis and show potential for the diagnosis of tuberculosis (TB). However, rats’ ability to discriminate between clinical sputum containing other Mycobacterium spp. and nonmycobacterial species of the respiratory tract is unknown. It is also unknown whether nonmycobacterial species produce odor similar to M. tuberculosis and thereby cause the detection of smear-negative sputum. Sputum samples from 289 subjects were analyzed by smear microscopy, culture, and rats. Mycobacterium spp. were isolated on Lowenstein-Jensen medium, and nonmycobacterial species were isolated on four different media. The odor from nonmycobacterial species from smear- and M. tuberculosis culture-negative sputa detected by >2 rats (“rat positive”) was analyzed by gas chromatographymass spectrometry and compared to the M. tuberculosis odor. Rats detected 45 of 56 confirmed cases of TB, 4 of 5 suspected cases of TB, and 63 of 228 TB-negative subjects (sensitivity, 80.4%; specificity, 72.4%; accuracy, 73.9%; positive predictive value, 41.7%; negative predictive value, 93.8%). A total of 37 (78.7%) of 47 mycobacterial isolates were M. tuberculosis complex, with 75.7% from rat-positive sputa. Ten isolates were nontuberculous mycobacteria, one was M. intracellulare, one was M. avium subsp. hominissuis, and eight were unidentified. Rat-positive sputa with Moraxella catarrhalis, Streptococcus pneumoniae, Staphylococcus spp., and Enterococcus spp. were associated with TB. Rhodococcus, Nocardia, Streptomyces, Staphylococcus, and Candida spp. from rat-positive sputa did not produce M. tuberculosis-specific volatiles (methyl nicotinate, methyl para-anisate, and ortho-phenylanisole). Prevalence of Mycobacterium-related Nocardia and Rhodococcus in smear-negative sputa did not equal that of smear-negative mycobacteria (44.7%), of which 28.6% were rat positive. These findings and the absence of M. tuberculosis-specific volatiles in nonmycobacterial species indicate that rats can be trained to specifically detect M. tuberculosis.
Seroprevalence of Leptospira infection in bats roosting in human settlements in Morogoro municipality in Tanzania
(2014-01) Mgode, G; Mbugi, H.A; Mhamphi, G.G; Ndanga, D; Nkwama, E
Leptospirosis is a neglected emerging infectious disease with high burden in Africa. Major reservoirs of leptospirosis are rodents and other small mammals. Studies of leptospirosis in bats and the extent to which they contribute to its transmission to humans and domestic animals in Tanzania are lacking. The objective of this study was to determine the prevalence of leptospirosis and local Leptospira serovars in bat colonies found around human settlements in Morogoro, Tanzania. In this study, mist nets were used to capture bats at Sokoine University of Agriculture main campus, whereas bats roosting on trees at Nunge A, Nunge B and Mwere primary school were captured manually. Leptospirosis was determined using the gold standard microscopic agglutination test for determination of Leptospira antibodies. Six live Leptospira serovars including local Leptospira serovar Sokoine, Kenya and Lora reported in rodents and domestic animals in Tanzania, and reference serovars Hebdomadis, Canicola and Pomona were used in the study. Leptospirosis prevalence was high in bats (19.4%) and higher within colonies (27.3%). Leptospira serovar Sokoine was more prevalent (19.4%) compared to serovars Kenya (2.8%) and Lora (2.8%). Serovars Pomona, Canicola and Hebdomadis were not detected in bats. In conclusion, bats are potential reservoir and transmitter of Leptospira serovar Sokoine, hence should be prevented to access houses and roosting in human settlements to avoid public health risks. Routine diagnosis of human leptospirosis is needed in Tanzania as evidence show a high prevalence of Leptospira in reservoir hosts interacting with humans.
Using giant African pouched rats to detect tuberculosis in human sputum samples: 2010 findings
(2011-07-17) Mahoney, A.M; Weetjens, B.J; Cox, C; Beyene, N; Mgode, G; Jubitana, M; Kuiper, D; Kazwala, R; Mfinanga, G.S; Durgin, A; Poling, A
Giant African pouched rats previously have detected tuberculosis (TB) in human sputum samples in which the presence of TB was not initially detected by smear microscopy. Operant conditioning principles were used to train these rats to indicate TB-positive samples. In 2010, rats trained in this way evaluated 26,665 sputum samples from 12,329 patients. Microscopy performed at DOTS centers found 1,671 (13.6%) of these patients to be TB-positive. Detection rats identified 716 additional TB-positive patients, a 42.8% increase in new-case detection. These previously unreported data, which extend to over 20,000 the number of patients evaluated by pouched rats in simulated second-line screening, suggest that the rats can be highly valuable in that capacity.