Guinea pig infected with Mycobacterium tuberculosis via oral consumption

Disseminated Mycobacterium genavense infection in a guinea pig (Cavia porcellus): a case report

Background

Mycobacteria are found in many environmental conditions and infect a variety of species, including rodents and rabbits. Guinea pigs are used experimentally as a model for Mycobacterium tuberculosis, but natural mycobacteriosis in guinea pigs has not been reported.

Case presentation

A 1.5-year-old female guinea pig was found acutely deceased with no premonitory illness. On gross post-mortem examination, multifocal to coalescing, raised, firm, pale tan nodules with discrete, irregular margins were noted over the surfaces of all lung lobes. Histopathology revealed nodules composed of clustered foamy macrophages and multinucleated giant cells containing numerous bacterial rods. Similar bacteria-laden macrophages were noted within sections of the liver, heart, palpebral conjunctiva, duodenum, and cecum. Polymerase chain reaction was performed on tissues collected during post-mortem examination. The 16S rRNA gene product was sequenced and was identical to the Mycobacterium genavense type strain.

Conclusions

To the best of the author’s knowledge, this report details the first documented case of Mycobacterium genvaense infection in a guinea pig and a follow up investigation of close-contact animals. Given their experimental susceptibility and this clinical case report, mycobacteriosis should be considered as a differential in guinea pigs exhibiting weight loss in the absence of other clinical signs. With the potential for zoonotic transmission in immunosuppressed individuals, precautions should be taken to safeguard human health in cases of guinea pigs with suspected M. genavense infection.

The source and fate of Mycobacterium tuberculosis complex in wastewater and possible routes of transmission

BACKGROUND

The Mycobacterium tuberculosis complex (MTBC) consists of causative agents of both human and animal tuberculosis and is responsible for over 10 million annual infections globally. Infections occur mainly through airborne transmission, however, there are possible indirect transmissions through a faecal-oral route which is poorly reported. This faecal-oral transmission could be through the occurrence of the microbe in environments such as wastewater. This manuscript, therefore, reviews the source and fate of MTBC in the wastewater environment, including the current methods in use and the possible risks of infections.

RESULTS

The reviewed literature indicates that about 20% of patients with pulmonary TB may have extra-pulmonary manifestations such as GITB, resulting in shedding in feaces and urine. This could potentially be the reason for the detection of MTBC in wastewater. MTBC concentrations of up to 5.5 × 105 (±3.9 × 105) copies/L of untreated wastewater have been reported. Studies have indicated that wastewater may provide these bacteria with the required nutrients for their growth and could potentially result in environmental transmission. However, 98.6 (± 2.7) %, removal during wastewater treatment, through physical-chemical decantation (primary treatment) and biofiltration (secondary treatment) has been reported. Despite these reports, several studies observed the presence of MTBC in treated wastewater via both culture-dependent and molecular techniques.

CONCLUSION

The detection of viable MTBC cells in either treated or untreated wastewater, highlights the potential risks of infection for wastewater workers and communities close to these wastewater treatment plants. The generation of aerosols during wastewater treatment could be the main route of transmission. Additionally, direct exposure to the wastewater containing MTBC could potentially contribute to indirect transmissions which may lead to pulmonary or extra-pulmonary infections. This calls for the implementation of risk reduction measures aimed at protecting the exposed populations.

Pathogenetic role of tumor necrosis factor (TNF-α) for the development of peritoneal tuberculosis in an experiment

Currently tuberculosis is considered as a group of diseases united by one etiological factor. The pathogenesis of certain localizations of tuberculous inflammation, in particular peritoneum tuberculosis, hasn’t been sufficiently studied. The role of cytokine mechanisms in the development of the disease and the elaboration of non-sterile immunity requires further experimental studies, in particular the creation of a reproducible model on laboratory animals.

The aim: to study the effect of TNF-α on the development of tuberculosis of the serous coat of the abdominal cavity, as well as to evaluate the possibility of modeling tuberculous peritonitis in laboratory animals using infliximab.

Materials and methods. The studies were conducted on 18 male rabbits, which were simulated peritoneal tuberculosis by intra-abdominal administration of a suspension of Mycobacterium tuberculosis. 10 rabbits of the experimental group were intravenously injected with an infliximab solution and an iron (III) hydroxide sucrose complex intraperitoneally a day before infection.

Results. In the control group of animals, tuberculosis either didn’t develop, or in a third of cases it affected only the pulmonary parenchyma, while proliferative processes prevailed. On the contrary, in animals with inactivated TNF-α, in 100 % of observations, tuberculous peritonitis was detected with associated lung damage and the predominance of alterative caseous processes.

Conclusion. The created model of tuberculous peritonitis shows the leading role of TNF-α in the activation of macrophages, as well as in attracting cells to the site of infection. This is the primary signal necessary for the formation and stability of granulomas since the neutralization of this cytokine leads to a loss of control over the infection and the destruction of the granuloma with the development of destructive tuberculosis in the serous coat of the abdominal cavity.