Pasteurella

Pasteurella is a genus of Gram-negative, nonmotile, non-spore-forming coccobacilli in the family Pasteurellaceae. It comprises several species that colonize the mucous membranes of many animals, most notably domestic cats and dogs. Pasteurella multocida is the species most commonly associated with human disease.

Humans typically acquire infection through animal bites or scratches, or by close contact with animals. Wound infections often develop within a day or two and present as cellulitis with swelling and redness; purulent discharge may occur. More severe infections can involve deeper structures, including septic arthritis, osteomyelitis, pneumonia, and bacteremia, especially in the elderly or immunocompromised individuals.

Laboratory diagnosis is based on isolation of the organism from wound exudate, blood, or other normally sterile sites. Pasteurella species are small Gram-negative coccobacilli that are oxidase-positive and catalase-positive and grow on routine culture media such as blood agar. Identification is typically confirmed by biochemical testing or modern methods such as MALDI-TOF mass spectrometry.

Treatment for Pasteurella infections is typically straightforward because many strains are susceptible to penicillins. Amoxicillin-clavulanate is a common first-line choice for animal-bite wounds. Alternatives include doxycycline, certain cephalosporins, or other beta-lactam/beta-lactamase inhibitor combinations. Intravenous therapy may be required for severe or deep-seated infections, with agents such as ampicillin-sulbactam or piperacillin-tazobactam. Antibiotic choice should be guided by susceptibility testing when available and the clinical site of infection.

Prevention focuses on prompt wound care after animal bites, appropriate tetanus prophylaxis, and, for high-risk exposures, timely antibiotic prophylaxis and medical evaluation. Reducing animal bites through responsible pet handling also lowers risk.