DM2 Pt2-3 Mycobacterial infections Flashcards
What type of bacteria are mycobacteria?
Mycobacteria are intracellular, acid-fast, slow-growing bacilliform bacteria resistant to environmental conditions.
What syndromes can mycobacterial infections cause in cats?
Mycobacteria can cause tuberculosis, atypical or non-tuberculous mycobacteriosis, and leprosy in cats.
How do cats become infected with Mycobacterium microti?
Cats become infected through direct contact with small rodents like voles and mice.
How is Mycobacterium bovis transmitted to cats?
M. bovis is transmitted through ingestion of infected milk or contact with badgers or infected environments.
What is the concern related to zoonotic transmission of Mycobacterium from cats?
A recent case in the South of England proved zoonotic transmission of M. bovis from a cat to humans.
What are the main risks for cats contracting non-tuberculous mycobacteria (NTM)?
The main risk is wound contamination from environmental sources like soil, water, and decaying vegetation.
How do non-tuberculous mycobacterial infections in cats usually present?
Infections are often subcutaneous and dermal, presenting as localized skin lesions.
How do cats become infected with Mycobacterium lepraemurium (feline leprosy)?
Cats become infected through direct contact, rodent bites, or wound contamination from soil or plants.
What is the usual presentation of feline leprosy?
Feline leprosy typically presents as skin nodules.
How is tuberculosis in cats caused by Mycobacterium bovis or M. tuberculosis typically presented?
Tuberculosis in cats is a systemic disease with disseminated internal lesions, but it can also present as cutaneous nodules and ulceration.
What type of disease does Mycobacterium microti cause in cats?
M. microti can cause localized or disseminated cutaneous disease, sometimes with systemic dissemination.
What are some non-specific tests used to assess mycobacterial infection in cats?
Non-specific tests include serum biochemistry, haematology, and radiography for lung, abdominal, or bone involvement.
What radiographic changes may be seen in cats with mycobacterial infection?
Changes can include tracheo-bronchial lymphadenopathy, lung infiltration, localised lung consolidation, pleural effusion, and hepato- or splenomegaly.
Why is hypercalcaemia important in mycobacterial infection?
Hypercalcaemia has been observed in some cases and correlates with a poorer prognosis.
Why is the tuberculin skin test unreliable in cats?
Cats do not react strongly to intradermal tuberculin, making skin testing unreliable for diagnosing tuberculosis.
What is the role of Ziehl-Neelsen (ZN) staining in diagnosing mycobacterial infection?
ZN staining is used on aspirates or biopsy samples to detect acid-fast organisms like mycobacteria.
Why are some ZN-positive samples negative in culture?
ZN-positive organisms often fail to culture positive, and even when they do, culture can take around two months.
What is the best practice for handling biopsy material for suspected mycobacterial infections?
Biopsy samples should be divided into three parts: one for ZN staining, one for histopathology, and one frozen for future culture.
Why should precautions be taken when handling biopsy material suspected of mycobacterial infection?
Until the organism is properly characterised, it should be considered a potential human pathogen, requiring precautions.
What legal obligations exist in the UK regarding suspected Mycobacterium bovis in cats?
Veterinary surgeons must notify the Divisional Veterinary Manager if tuberculosis is suspected in a domestic cat.
What is typically seen on histopathology of tissues infected with mycobacteria?
Granulomatous inflammation with foamy macrophages containing acid-fast bacilli is typically seen.
What key factors should be considered before treating a cat with suspected mycobacterial infection?
Consider zoonotic risk, involvement of household members, the extent of the disease, and long-term treatment requirements.
Why is treatment of feline tuberculosis often contentious?
Treatment is long-term, difficult, costly, and poses a zoonotic risk, especially in cases with generalised disease or respiratory involvement.
What is the prognosis for cats with uncomplicated cutaneous mycobacterial disease?
Cats with uncomplicated cutaneous disease have the most favorable prognosis.
Why is surgical excision of cutaneous lesions not always successful?
Surgical excision of small lesions may help, but larger lesions often result in wound dehiscence or recurrence of infection.
Why is the use of fluoroquinolones alone not recommended for treating mycobacterial infections?
Fluoroquinolone monotherapy can promote drug resistance, making double or triple therapy a better option.
What is a potential consequence of generating drug resistance in mycobacterial infections?
Drug resistance can endanger both the infected cat and human patients by reducing treatment effectiveness.
How long must treatment for mycobacterial infections typically continue?
Treatment typically requires a combination of two or three antibiotics for several months.
Why is owner compliance challenging in treating mycobacterial infections in cats?
Treatment is long, difficult to maintain, and incomplete treatment can lead to failure and antibiotic resistance.
What zoonotic risks should be communicated to owners of cats with mycobacterial infections?
Owners, especially those immunocompromised, should be informed of the zoonotic risk associated with mycobacterial infections in cats.
What can be a reason for euthanising cats with mycobacterial infections?
Due to the length, cost of treatment, and zoonotic risk, some infected cats may be euthanased.
