Studies on evaluation of performance of trained sniffer rats in detection of mycobacteria species from clinical cases of human Tuberculosis

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Sokoine University of Agriculture


The Belgian humanitarian research organisation Anti-Persoonmijnen Ontmjinende Product Ontwikelling (APOPO), in collaboration with the Sokoine University of Agriculture (SUA), has pioneered a project that involves the training of African Giant Pouched rats (Cricetomys gambianus) as a potentially faster tool for the detection of mycobacteria species by sniffing out positive sputum samples. This study has evaluated the performance of these rats in detection of Mycobacteria species from human sputum samples. A total of 910 sputum specimens from patients with suspected pulmonary tuberculosis (PTB) were collected and tested. All specimens were tested by the sniffer rats, microscopy and culture followed by PCR for all culture positive samples. The Culture results were used as the reference for assessment. Out of 910 specimen tested, 161 (17.7%) were culture positive, 90 (9.9%) were positive by microscopy and 120 (13.2%) were positive by trained sniffer rats technique. A total of 481 samples (52.9%) were declared as negative by all three techniques. Sensitivity of trained sniffer rats technique and microscopy was 74% and 56% (P <0. 0076) respectively, whereas specificity of trained sniffer rats and microscopy was 64% and 98% respectively (P< 0.0001). The sniffer rats technique is significantly more sensitive and less specific than microscopy, hence recommended to be used as screening tool for human cases of PTB. The 161 specimens which were culture positive and also confirmed to have acid-fast- bacilli by microscopy were subjected to mycobacterium genus PCR typing. Out of 161 isolates, 127 isolates were identified to belong to the group of Mycobacterium tuberculosis complex. Using RD9 PCR which further characterizes mycobacterium tuberculosis complex into their specific species, it was confirmed that 127 (78.4%) of the isolates belonged to the specific species of the Mycobacterium tuberculosis. Out of 161 culture positive isolates, 108 isolates were also detected by PCR and sniffer rats.


A Dissertation 2012


Performance trained sniffer, Rats detection, Mycobacteria species, Acid-fast bacilli, Human Tuberculosis