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Bacterial structure and functions
Bacillus anthracis (Anthrax)
Bacillus cereus (Food poisoning)
Corynebacterium diphtheriae (Diphtheria)
Clostridium botulinum (Botulism)
Clostridium difficile (Pseudomembranous colitis)
Clostridium tetani (Tetanus)
Streptococcus agalactiae (Group B Strep)
Streptococcus pyogenes (Group A Strep)
Bartonella henselae (Cat-scratch disease and Bacillary angiomatosis)
Legionella pneumophila (Legionnaires disease and Pontiac fever)
Salmonella typhi (typhoid fever)
Yersinia pestis (Plague)
Vibrio cholerae (Cholera)
Bordetella pertussis (Whooping cough)
Francisella tularensis (Tularemia)
Haemophilus ducreyi (Chancroid)
Mycobacterium tuberculosis (Tuberculosis)
Mycobacterium avium complex (NORD)
Gardnerella vaginalis (Bacterial vaginosis)
Coxiella burnetii (Q fever)
Ehrlichia and Anaplasma
Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species
Borrelia burgdorferi (Lyme disease)
Borrelia species (Relapsing fever)
Treponema pallidum (Syphilis)
Pasteurella multocida is a gram-negative coccobacillus which is involved in a zoonotic infection.
Most often, it causes soft tissue and respiratory infections.
There are 3 subspecies that cause disease in humans: Pasteurella multocida subspecia multocida, Pasteurella multocida subspecia septica and Pasteurella multocida subspecia gallicida.
All of these subspecies are encapsulated, meaning they have a polysaccharide layer called a capsule.
And depending on the capsular antigens found on the capsule, they can be grouped in 5 different serogroups: A, B, D, E and F.
Each of them is involved in a different type of disease and only serogroups A and D cause disease in humans.
So, serotype A causes respiratory infections and serotype D causes soft tissue infections like cellulitis.
Now, Pasteurella multocida has a thin peptidoglycan layer, so it doesn’t retain the crystal violet dye during gram staining.
Instead, like any other gram-negative bacteria, it stains pink with safranin dye.
But, sometimes, it can have a bipolar staining which means that only the poles of the bacteria stain pink, and the rest of it remains unstained, so the bacteria look like safety pins under the microscope.
Alright, now Pasteurella multocida is non-motile, non-spore forming, and facultative anaerobic which means it can survive in both aerobic and anaerobic environments.
It’s oxidase and catalase positive, which means it can produce both these enzymes, and it’s also nitrate reduction positive which means it can produce an enzyme that hydrolyzes nitrate into nitrite.
Finally, Pasteurella multocida grows well at 37ºc on sheep blood agar, which is the preferred culture medium, but it can also grow on chocolate agar, Mueller-Hinton agar or brain heart infusion agar.
The colonies are opaque or grey, and small - they’re only about 1-2 millimeters in diameter each.
Now, Pasteurella multocida has a number of virulence factors, that are like assault weaponry that help it attack and destroy the host cells, and evade the immune system.
First, on its capsule there are fimbriae, which are hair-like extensions that help the bacteria attach to host cells.
Pasteurella multocida is a gram-negative, facultative anaerobic coccobacillus inhabiting the upper respiratory tract of animals, particularly in cats and dogs. It is known to cause zoonotic infections from animals to humans, including cellulitis, osteomyelitis, endocarditis, or even meningitis.
Symptoms vary depending on the type of infection, and the diagnosis relies on cultures from biological samples like pus, cerebrospinal, blood, or respiratory tract samples, and PCR. Pasteurella multocida infections are treated with antibiotics such as penicillin, tetracyclines, cephalosporins, and quinolones.
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