RESUMO
OBJECTIVE/BACKGROUND: Tuberculosis (the white plague) is regarded as one of the most widespread infectious diseases and continues to be a leading cause of death and the most prominent public health problem worldwide. It is caused by Mycobacterium tuberculosis complex, which refers to a group of seven species; one of them known as Mycobacterium bovis-the cause of bovine-type tuberculosis-has an exceptionally wide host range. It infects cattle, humans, goats, cats, dogs, buffalo, and deer. Many susceptible species, including man, are spillover hosts in which infection is not self-maintaining. The objective of this study is to investigate the role of infected slaughtered cattle in spreading tuberculosis to those who work in abattoirs. METHODS: Three hundred slaughter cattle in some abattoirs of the Baghdad governorate were examined grossly. Tissue samples were taken from lesions that had appeared on lymph nodes, lung, liver, spleen, peritoium, and intestines. A routine examination was performed: (1) smear for Ziehl Neelsen acid-fast stain; (2) cultured: each sample was cultured on Stone-brink with sodium pyrovite and on Lowenstein media which contain glycerol; and (3) incubated at 37°C for 4-10weeks, to observe the characteristic features of bacterial colonies. Biochemical tests, nitrate reduction, urea analysis, tween 80 lysis, and catalase test were employed to isolate and identify the bacteria. Pieces from tissue samples were kept in 10% formalin for histopathological investigation. Tuberculin tests and X-rays were conducted for 186 workers who were in contact with slaughtered cattle in the same abattoirs, with an age range of 15years to 60years. Sputum samples were collected from all workers in clean and sterile containers, and subjected to the same routine examination. The collection of samples was carried out under strict and sterile conditions and the sputum was kept in 50% oxalic acid for 20 min before culture on media to avoid the contamination. RESULTS: Gross examination of cattle carcasses showed tubercle in four of them that was distributed in lymph nodes and different organs especially in lungs, livers, and in one case tubercle appeared on the peritoneum and intestines. A histopathological study revealed different lesions with an accumulation of lymphocytes and macrophages in lymph nodes and organs. Four isolates of M. bovis were diagnosed and identified by routine examination that indicated the percentage of infection in slaughtered cattle was 1.33%. The result of the workers' examinations clarified that only one of the workers had a positive result for the tuberculin test, whereas three of them had positive results in X-ray and routine examination. Three isolates were obtained from workers (1.6%); two of these isolates were diagnosed as M. bovis and the other as M. tuberculosis. CONCLUSION: The main conclusion of this study is that two workers were infected with cattle's strain which confirms the role of slaughtered cattle in the transmission of this dangerous, chronic, and zoonotic disease to man.
RESUMO
INTRODUCTION: Mycobacterium bovis has a broad host range, and it is the principal agent responsible for tuberculosis (TB) in bovine, domestic and wild mammals. M. bovis also infects human, causing zoonotic TB through ingestion, inhalation and, less frequently by contact with mucous membranes and broken skin. Zoonotic TB was formerly an endemic disease, usually transmitted to man by consumption of raw cow's milk. It is indistinguishable clinically or pathologically from TB caused by M. tuberculosis. OBJECTIVE: The aims of this study were, to isolate and identified M. bovis from raw milk samples by different methods, and evaluate the virulence of M. bovis in laboratory animals (Rabbit). MATERIALS AND METHODS: To conduct the study, ninety three cow's milk samples were collected from farms around Baghdad governorate. The decontamination of milk samples was firstly carried out, then samples were subjected to routine tests which include, direct smear for Ziehl Neelsen acid fast stain, culture, each sample was cultured on Lowenstein Jensen media with Sodium pyruvite (All cultures incubated on 37°C for 4-10weeks with continuous observation), and biochemical testes as Nitrate reduction test, Niacin paper strip test and pyrazinamidase test, were employed to diagnose and identified the bacteria. Beside molecular assay was used to confirm the identification of the isolates by Polymerase Chain Reaction (PCR) using specific primers for M. bovis. The virulence of these isolates were investigated through inoculate it in group of laboratory animals consist of 8 rabbit in addition to other group of 4 animals as control (inoculate with Phosphate Buffer Saline). The animals were scarified after 6weeks of inoculation, post- mortem examination was carried out, smears were taken from lesions, and tissue samples were collected from lymph nodes and different organs. RESULTS: The results revealed five isolates of M. bovis in direct smear by acid fast Ziehl-Neelsen stain, while eight isolates observed by culture, the colonies appeared with characteristic feature of cream color, rough, and with irregular edge. The molecular assay using PCR technique confirmed the diagnosis of eight positive isolates in smears and culture. The virulence of these isolates were investigated through the pathological effects appeared in inoculated rabbit which showed lesions scattered mainly in lymph nodes and different organs as lung, liver, spleen and kidney when compared with control group which were naive. Beside the infiltration of mononuclear cells in the internal organs particularly in the lungs. The result of histopathological examination clarified the virulence of M. bovis isolates, and its impact on tissue and organs of the rabbit. CONCLUSION: Our study conclude the presence of M. bovis isolates in milk in high percentage pause important source of tuberculosis infection for human being.
