(From Micro, 26 Oct 2000, by Brian Buschman)
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Brucella is a disease of pigs, cattle and goats. It’s zoonotic and in the US it’s only seen in international travelers and with meat packers. Abattoirs are one group that Dr. A likes to test to see if you will recognize they get Brucella. There is no person to person transmission of Brucella.
Brucella is an intracellular organism and hence causes a PPD reaction. Clinically it presents with “undulating fever” which rises in the morning, peaks late afternoon and declines later on.
Francis the rabbit is one of the nastiest little creatures as it only takes about 10 organisms to cause infection. It’s the cause of Rabbit Fever. It can infect whatever part the organism lands on so depending on the route of entry it can cause:
1) Pneumonic tularemia which is the worst and most deadly of the conditions.
2) Ulceroglandular tularemia has fever, skin legions and looks like the bubonic plaque.
3) Typhoidal tularemia is Francisella in the gut.
4) Oculoglandular tularemia is when it is in the eyes.
Unlike Brucella, Pasteurella is extracellular. It is in the mouth of cats and dogs and infects with animal bites causing cellulitis, abscesses and osteomyelitis.
It can also be inhaled for URT infections but does not cause pneumonia. Systemic spread causes bacteremia and peritonitis.
The best management is to properly clean the site of the animal bite before closing.
Bart was unlucky and got scratched by the wrong cat and now has the shakes. It is extracellular and has a “twitching motility.”
It produces a star-shaped granulomas.
Patients present with a low grade fever that can recur. They also have lymphadenopathy. The fever can relapse but is self limiting. By the time they present (2-3 weeks) the cat scratch has usually healed.
Nocardia and Actinomyces are bacteria that resemble fungi but are like mycobacterium. They grow in rods like hyphae and fragment into bacteria-like pieces.
Actinomyces are normal flora that produce “sulfur granules” and grow in thioglycolate agar.
Actinomyces israelli is the most common. Actinomyces bovis gives cattle a lumpy jaw.
It appears in four forms and causes abscesses with central necrosis surrounded by granulation tissue. The four types are classified according to their areas affected:
1) Cervicofacial
2) Thoracic – This usually includes a subacute myocardial infection.
3) Abdominal
4) Genital – The genital form is usually from IUDs.
Nocardia is an acid-fast organism that is identified by it’s lack of sulfur granules. It has a very colorful look on culture. It is NOT normal flora.
Nocardia is opportunistic and causes lobar pneumonia in immunocompromised patients that is often confused with TB. Both TB and Nocardia cause a diffuse lobar pneumonia but Nocardia does not cause granulomas or caseation.
Nocardia forms abscesses and lacks consolidation (like classic lobar pneumonia). It can also spread to the CNS, kidney, skin or just about anywhere.
Diagnosis is by chromatography, usually GLC or TLC. It is one of the few bacteria to be identified in this way.
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