Microbiology
Summary
Pasteurella multocida is a catalase-positive, oxidase-positive, gram-negative coccobacillus that demonstrates bipolar or safety pin staining under light microscopy. Its virulence is majorly attributed to its capsule.
The bacteria is commonly found in the respiratory tract of small mammals, particularly cats and dogs, and is often transmitted to humans through pet bites. Critical clinical features of this bacteria include soft tissue infections such as cellulitis manifesting within the first 24 hours post bite, with the potential to evolve into necrotizing fasciitis. There's also a risk of the bacteria spreading to the bone, causing osteomyelitis. The treatment of choice for infections caused by this bacteria is penicillin, preferably combined with a beta-lactamase inhibitor like clavulanic acid to prevent resistance.
Lesson Outline
Don't stop here!
Get access to 128 more Microbiology lessons & 13 more medical school learning courses with one subscription!
FAQs
P. multocida is a gram-negative, catalase-positive, oxidase-positive bacterium with a characteristic bipolar staining when viewed on microscopy. It commonly resides in the oral and respiratory tracts of several animals, including dogs and cats. This organism was named after the renowned French biologist, Louis Pasteur, who made many significant contributions to the field of microbiology.
Labradors and other dog breeds, as well as cats, often harbor P. multocida in their oral cavities. When these pets bite humans, the bacteria can be transferred, leading to a localized infection. In fact, P. multocida is one of the most common causes of infection resulting from animal bites.
P. multocida can cause various types of infections in humans, predominantly soft tissue infections. These can manifest in several ways, including cellulitis, necrotizing fasciitis, and osteomyelitis. Additionally, in rare cases, it may also cause respiratory tract infections or systemic infections.
Bipolar staining, also often called safety pin staining, is a unique characteristic of P. multocida under the microscope. The bacterium stains more heavily at the poles, giving it an appearance similar to a safety pin. This helps medical professionals in the quick and accurate identification of the organism.
Penicillin is often the first-line drug of choice for P. multocida infections. However, due to the increasing incidence of resistance and allergy issues, alternatives such as amoxicillin and clavulanic acid may also be used. It's important to note that treatment should be tailored to the individual patient's clinical condition and sensitivity of the organism.
