Introduction
Pasteurella is small gram-negative bacteria that are present in animals. They are normal habitats in cats' and dogs' oral and nasal secretions. However, these bacteria are capable of causing various infections in humans. For example, Pasteurella multocida enters the human body through bites or starches from animals (cats or dogs) and causes severe skin infections. However, in some cases, these bacteria can enter humans directly from the nasal and salivary secretions of dogs and cats.
What Is Pasteurella?
Pasteurella genus members are small, gram-negative, nonmotile, facultatively anaerobic organisms. These bacteria are named Pasteurella after the microbiologist Louis Pasteur first identified them. Pasteurella bacteria live in the mouth of animals like cats and dogs and enter the human body through a scratch and bite from these animals. Therefore, Pasteurella species are considered zoonotic pathogens. They cause life-threatening complications such as pneumonia in sheep, cattle, and birds. However, Pasteurella bacteria do not cause any disease in dogs and cats. They constitute the normal flora of the mouth and nose of cats and dogs.
Pasteurella multocida frequently causes human Pasteurella infection with common symptoms like swelling, bloody drainage from the wound, and cellulitis. In severe cases, infections may progress to nearby joints and result in further complications such as arthritis, severe pain, swelling, and abscesses.
What Is Pasteurellosis?
Pasteurella bacteria cause infections known as pasteurellosis. Pasteurella multocida is the most common species causing human infections. They can infect cats, rabbits, cattle, and dogs. Pasteurella multocida is a common commensal in the mouth and respiratory tract of animals. They cause numerous infectious conditions in domestic animals. Pasteurella multocida acts with other infectious agents, including viruses, Mycoplasma, and Chlamydia species, and causes fatal infectious conditions. They cause various infectious diseases alone or in association with other pathogens.
It includes:
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Shipping fever in sheep and cattle.
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Fowl cholera.
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Pasteurellosis of rabbit.
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Enzootic pneumonia in goats and sheep.
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Pasteurellosis of chinchillas.
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Atrophic rhinitis in pigs.
What Are the Different Types of Pasteurella Infections?
Pasteurella species cause skin and soft tissue infections. The several forms of infections caused by Pasteurella are the following.
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Skin or Subcutaneous Tissue Infection - It usually develops in the forearm and hand after a cat bite. Skin infection is marked by a localized area of inflammation known as phlegmon. Inflammatory signs develop rapidly within one to two hours and result in severe pain, fever, edema, vomiting, diarrhea, headache, and exudate from the affected area. In cases of severe infection, complications may occur in the form of osteitis (bone inflammation) and septic arthritis.
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Pneumonia Disease - It occurs in patients with chronic pulmonary diseases. Chronic Pasteurella infection in these cases presents as a bilateral consolidating type of pneumonia.
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Sepsis - Pasteurella infection sometimes leads to a life-threatening condition called sepsis. It presents with high fever, vomiting, chills, coagulopathy, and shock.
How Does Pasteurella Infection Spread?
Pasteurella infections are commonly associated with scratches or bites from dogs and cats. The highest risk of disease occurs from a cat bite due to the sharp, small teeth of cats can cause punctures and increase the incidence of infection. In some cases, Pasteurella infections have been associated with the licking of open wounds by animals. However, the majority of Pasteurella infection cases show a history of scratch or bite from an animal, mostly cat or dog. Pasteurella infections are spread through inhalation of aerosol droplets, direct contact, ingestion of contaminated oral discharges, water, food, and nasal discharges from infected animals. In addition, humans can directly acquire Pasteurella species through cat and dog bites.
What Are the Signs of Pasteurella Infection?
The common signs and symptoms associated with Pasteurella infection are the following:
1. Initial Symptoms
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Swelling.
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Skin irritations.
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Redness.
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Tenderness of the skin.
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Edema.
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Warmth skin.
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Fever.
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Chills.
2. Severe Complications
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Joint infections (arthritis).
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Septicemia (blood infections).
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Osteomyelitis.
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Tendon infection.
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Urinary tract infections.
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Eye infections.
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Pneumonia.
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Lymphadenopathy.
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Appendicitis.
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Brain abscess.
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Empyema.
What Are the Diagnostic Tests Used for Pasteurella Infections?
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Peripheral white blood cell count.
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C-reactive protein levels.
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Erythrocyte sedimentation rate (ESR).
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Blood cultures.
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Cultures of draining wounds.
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Culture of Pasteurella species from body fluids (joint fluid, peritoneal fluid, and cerebrospinal fluid).
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Respiratory tract cultures.
How Can We Avoid Pasteurella Infection?
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Avoid bites from cats and dogs.
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Avoid cat and dog saliva contact, especially in cases of broken skin.
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Antibiotic prophylaxis for animal bites in patients with severe injuries, wounds in hands, immunocompromised cases, and prosthetic joints.
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Wash hands properly after contact with pets.
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Avoid unnecessary contact with the nasal and oral secretions of pets.
What Are the Treatment Options for Pasteurella Infections?
Oral antibiotic drugs can be used for the prophylactic treatment of animal bite wounds and in cases of mild to moderate infections caused by Pasteurella bacteria. Amoxicillin is the first choice in Pasteurella infections as they cover Pasteurella species and other polymicrobial spectrum associated with scratch and bite wounds like Streptococci, anaerobic bacteria, and Staphylococcus aureus.
Other antibiotic agents like Doxycycline, Moxifloxacin, and a combination of Clindamycin and Levofloxacin can also be used. For patients with severe complications and illness due to Pasteurella, infection hospitalization is required. Systemic management of the associated complications, such as joint infections, pneumonia, meningitis, and others, must be done to save lives. For mild skin infections, antibiotics can be given for seven to ten days. However, severe infections involving deeper structures, including bone and joints, need antibiotic treatment for nearly four to six weeks.
Conclusion
Pasteurella is a species of gram-negative bacteria that commonly cause skin and soft tissue infections in humans following an animal scratch or bite. These small, oval, or rod-shaped bacteria are found in dogs' and cats' nasal and oral secretions. Pasteurella bacteria enter the human body through animal bites and scratches or through direct contact with animals' secretions. After entering the human cells, they initially cause mild to moderate infectious symptoms and later progress into severe conditions involving the brain, respiratory system, and bone. Therefore, proper precautions must be taken in individuals in frequent contact with dogs and cats to avoid Pasteurella infections.