Isolation and identification of bovine tuberculosis in a Brazilian herd (São Paulo)

Abstract

Mycobacterium was verified in animals from a Brazilian dairy herd, a total of 42 samples from 30 cows were submitted to culture and the isolated strains were analyzed by two polymerase chain reaction (PCR), the first specific for species belonging to the Mycobacterium complex (MTBC) (Bouvet et al. 1993). From a clinical and epidemiological perspective, a rapid method to differentiate both species is important for timely diagnosis, effective treatment (due to the intrinsic resistance of M. bovis to pirazynamide) and epidemiology of TB (Shah et al. 2002).The bovine population in Brazil consists of about 180 million animals, with prevalence of TB ranging between 0.9 and 2.9% depending on the region and kind of production (Kantor & Ritacco 1994). Between 1989 and 1998, official notification data indicated a national prevalence of 1.3% of infected animals (Brasil 2005). Due to disgonic and very slow growth, the identification of M. bovis by conventional biochemical methods is cumbersome and timeconsuming. Polymerase chain reaction (PCR) is a sensitive and fast diagnostic tool that can be used to detect the agent in clinical samples in 48 h, but the presence of inhibitors in samples can interfere with its performance (Haddad et al. 2004, Singh et al. 2004, Brasil 2005.Among the several PCR systems developed for detection of species composing the M. tuberculosis complex (MTBC) (Wards et al. 1995, Brasil 2005, we focused on two. One was described by Niyaz Ahmed et al.(1999) and based on specific primers (NZ1 and NZ2) for the insertion sequence IS 1081, selectively present in organisms of the MTBC. A multiplex-PCR with primers JB and specific primers for the gene encoding for pyrazinimidase (pncA) was reported by Shah et al. (2002) to differentiate between M. bovis and M. tuberculosis on colonies in culture and this method could detect less than 20 pg of DNA, and this last reaction was the second applied reaction in the present work for differentiation between M. bovis and M. tuberculosis.We here present our work aiming at the detection of M. bovis mainly in retrofaryngeal lymphnode samples of bovines from a herd of Tatuí (São Paulo, Brazil) by microbiological culture, and MTBC and M. bovis specific PCR systems, and comparing the microbiological results with the positive or inconclusive results at single intradermal comparative tuberculin test (SICTT) presented by these animals.Thirty bovines from a Tatuí herd in São Paulo, Southeast Brazil and with positive (> 4 mm) or inconclusive (2 to 3.9 mm) response to SICTT were taken to sanitary slaughter. We collected 42 samples composed of the retrofaryngeal lymphnodes independent of the presence or not of suggestive lesions for TB while this was perfomed for prescapular lylmphnodes, lung, and liver only when presenting characteristic lesions of TB (Table). Samples were maintained in sterile bags at 4ºC for transport to the Laboratory of Tuberculosis of Instituto Biológico, São Paulo, Brazil until futher analysis.For culturing, samples were decontaminated by means of the Pet...

Isolation and identification of Mycobacterium bovis in cattle slaughtered from an abattoir in Garanhuns, Pernambuco

“…The culture used in these studies was the most sensitive test. However, the results obtained in this study were similar to those observed in the study in a dairy herd of Tatuí, Brazil, which showed 60% (18/30) of the positive samples in the culture (NASSAR et al, 2007). Two samples were negative by PCR analysis even with suggestive colonies in the culture were identified.…”

Comparison of the Sensitivities of Different PCR Assays for the Detection of Mycobacterium tuberculosis Complex Isolates from Five Regions of Cameroon

“…In one study using infected human blood samples, the sensitivity of the IS1081 PCR assay was only 43.75% [9]. However, when the latter assay was applied in the identification of M. bovis culture isolates, it identified 27 out of 27 (100%) of the isolates [17]. This indicates that although the assay was not very sensitive in the present study, it could nonetheless be a sensitive assay in the detection of M. bovis.…”

Situation of bovine tuberculosis in Ecuador

“…In Ecuador's dairy areas, 90% of the cattle in the highlands are Holstein Friesian, whereas in the tropical areas, the main breeds used for milk production are Jersey, Brown Swiss, and crossbreeds. The differences in BTB prevalence among cattle breeds and geographic areas present in Ecuador, were also found in the slaughterhouses of Argentina (9), Brazil (53,54), and Mexico (55,56).…”