Pasteurella multocida infection
Edited October 20, 2015
The Pasteurella infection guidelines were first published in the J Feline Med Surg 2013; 15: 570-572 by Albert Lloret.
Pasteurella spp. are part of the normal oral flora of cats. Bites, scratches or even only close contact may transmit Pasteurella to humans. Signs of local infection may appear in 3 to 6 hours. Severe infections, septicaemia and peritonitis may occur in immunocompromised, and less frequently in immunocompetent persons in contact with cats. Disease in humans mainly occurs after a cat bite or scratch, but may also occur through respiratory secretions from cats in close contact with a person. Cat ownership by immunocompromised persons may carry a risk.
Pasteurella is common in subcutaneous abscesses and pyothorax in cats. Diagnosis confirmation is not difficult, as it grows readily in routinely used bacterial culture media. Penicillins and potentiated beta-lactamics are first line antibiotics in both humans and cats.
Pasteurella multocida, a gram-negative, facultative anaerobic, non-spore-forming pleomorphic coccobacillus, is a commensal bacterium and part of the natural flora in the nasopharynx and upper respiratory tract of the cat (Freshwater, 2008; Dolieslager et al., 2011).cvIn one study a 90% carrier state in gingival margins was shown (Freshwater, 2008).
Several subtypes have been associated with human infections, P. multocida subsp. multocida, P. canis, P. multocida subsp. septica, P. stomatis and P. dagmatis (Garniere et al., 1993).
Epidemiology and pathogenesis
Cat bites frequently become infected (20 to 80%), and P. multocida is the most commonly cultured bacterium from infected bite wounds (Freshwater, 2008). Apart from bites, scratches and licks, close contact has also been sufficient for infection. Bacteria usually enter through skin wounds, but inhalation of secretion droplets from the upper respiratory tract is another possible source (Kimura et al., 2004).
Disease in humans
P. multocida infection typically produces cellulitis and/or abscesses at the site of the bite or scratch, usually 3 to 6 hours after inoculation (Westling et al., 2000; Perez Garcia et al., 2009). Occasionally, the local infection can progress to necrotising fascitis, septic arthritis and osteomyelitis (Layton, 1999).
Respiratory infection, pneumonia and bronchopneumonia also are common, mostly in patients with a pre-existing lung disease (Perez Garcia et al., 2009).
Less frequently, a disseminating infection may produce septicaemia, which may lead to septic shock, meningitis, endocarditis, peritonitis, arthritis and other serious consequences (Perez Garcia et al., 2009).
Pasteurella peritonitis through a dialysis catheter after contact with a cat has been reported (Sol et al., 2012; Rondon-Berrios and Trebejo-Nunez, 2010).
Severe infections are usually seen in children, pregnant women, patients on chronic immunosupressive therapy, and immunocompromised persons. Chronic liver disease and cirrhosis entail a special risk of sepsis and peritonitis by Pasteurella (Adler et al., 2011; Hey et al., 2012).
Although severe disease generally appears in immunocompromised persons, about one third of septicaemic patients were previously healthy individuals (Kimura et al., 2004).
Disease in cats
Pasteurella multocida is one of the most frequent pathogens in infected skin wounds and subcutaneous abscesses (Roy et al., 2007). It is also one of the common bacteria producing pythorax in cats (Ottenjann et al., , 2008; Barrs et al., 2005; Walker et al., 2000). Pasteurella may also cause secondary lower respiratory tract infection and has been associated with spinal empyema and meningo-encephalomyelitis (Granger et al., 2007; Messer et al., 2006).
Diagnosis is made on the basis of bacterial culture from infected tissues or secretions. Pasteurella grows readily on chocolate and sheep-blood agar media, but fails to grow on MacConkey agar, the usual medium for Gram-negative bacteria. Strains are usually catalase-, oxidase-, indole- and sucrose-positive.
Treatment and prevention
Penicillins and potentiated beta-lactamics (amoxicillin-clavunalate potassium) are first line antibiotics for the treatment of Pasteurella infections (Freshwater, 2008; Perez-Garcia et al., 2009; Roy et al., 2007). Quinolones, cephalosporins and modern macrolids are also indicated (Feshwater, 2008). In severe cases, the therapeutic decision must be based on antibiotic susceptibility tests.
Pasteurella multocida leads to an important zoonotic infection and disease (Kimura et al., 2004). Local infections are common, also in immunocompetent persons, and the high prevalence of the bacterium is an indication for the use of prophylactic antibiotic therapy (amoxicillin clavulanate) after a cat bite (Freshwater, 2008). Septicaemia and severe, even fatal, disease may occur, especially in immunocompromised patients, in patients with cirrhosis and under dialysis. In these circumstances the risk of keeping a cat must be discussed with the owner, especially because transmission of the bacterium may occur just by close contact – not necessarily after a bite or scratch.
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