Introduction:
Pasteurella multocida or P.multocida is a gram-negative bacteria that is nonmotile, non-spore-forming, and sensitive to Penicillin. This bacteria frequently causes human soft tissue infections due to animal bites or scratches. These bacteria are typically present on the mucosal lining of the respiratory tract of several mammals, birds, etc.
What Is Pasteurella Multocida?
Pasteurella multocida is a non-spore-forming, gram-negative bacteria belonging to the Pasteurellaceae family. The Pasteurellaceae is a noteworthy family of facultative anaerobes, and these bacteria are typically rod-shaped. Facultative anaerobic organisms can generate ATP (adenosine triphosphate) by aerobic respiration if oxygen is available. However, it is capable of fermentation if oxygen is unavailable. Many cattle, poultry, and domestic pet species, particularly cats and dogs, frequently have Pasteurella multocida as a commensal in their upper respiratory tracts. Moreover, these bacteria are the most common commensal bacteria found in both domestic and wild animals globally.
What Is Pasteurella Multocida Infection?
Pasteurella multocida infections are infections occurring due to exposure to Pasteurella multocida bacteria, and the most common mode of contracting this infection is through an animal scratch or animal bite. Pasteurella multocida infection in humans is frequently linked to an animal bite, scrape, or lick, but the infection can sometimes occur without epidemiologic proof of animal interaction. In addition, soft tissue infection frequently occurs due to P. multocida. But, in the elderly, immunocompromised, and newborns, respiratory and other severe invasive infections, like bacteremia, meningitis, and endocarditis, can also occur. Fortunately, Pasteurella species are rather sensitive microorganisms that respond well to a Penicillin-based treatment plan.
What Causes Pasteurella Multocida Infection?
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Although Pasteurella multocida infection is most frequently linked to injury from domestic animals like dogs and cats, the infection can also be spread by other animals like rats, rabbits, birds, etc.
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A bite or penetrative injury is not always required for the infection to be transmitted, as there are reported cases of Pasteurella osteitis (inflammation of bones) and meningitis (inflammation of the brain and spinal cord) following only a lick by a carrier animal.
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Open wounds licked by cats or dogs can also lead to P. multocida infection.
How Common Is Pasteurella Multocida Infection?
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Every year, emergency departments in the United States report approximately 300,000 animal scratches or bites. The pathogen or bacteria most frequently linked to infection in these patients is Pasteurella multocida.
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According to one study, wound cultures from 50 percent of dog bites and 75 percent of cat bites have Pasteurella species.
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According to statistics, 10 to 20 human deaths annually are caused by animal bites.
What Are the Symptoms of Pasteurella Multocida Infection?
The signs and symptoms of Pasteurella multocida infection are:
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The infection could develop within 3 to 48 hours of the injury.
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Quickly progressing swelling in the area of the wound.
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Redness or erythema around the wound.
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Tenderness around the wound.
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Drainage may consist of blood, the liquid part of the blood (serosanguinous), and pus.
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Localized lymphadenopathy (swelling of lymph nodes).
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In rare cases, necrotizing fasciitis may also be seen. Necrotizing fasciitis is a rapidly spreading bacterial infection that can be fatal.
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Popping or clicking sound in the affected tissues (crepitus).
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Pain in the area of the wound.
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If bacteremia occurs, there can be fever, increased heart rate (tachycardia), and decreased blood pressure (hypotension).
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Patients with comorbidities like diabetes mellitus and alcoholism can have symptoms of a septic joint. These symptoms include fever, pain in the joints, swelling in the joints, etc.
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Osteomyelitis can also occur in wounds that penetrate the periosteum. Osteomyelitis occurs in patients with deep, penetrating injuries (usually caused by cat bites).
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Symptoms of meningitis include high-grade fever, stiff neck, headaches, fits, etc.
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If endocarditis occurs, symptoms include high fever, chills, difficulty breathing, excess sweating, cough, etc.
How Is Pasteurella Multocida Infection Diagnosed?
Diagnosis of Pasteurella multocida includes:
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Medical History: A detailed medical history of the patient should be obtained to know the possibilities of any recent animal encounter. A thorough physical and clinical evaluation of the patient’s wound should also be done to study the signs and symptoms.
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Blood Examination: A complete blood count (CBC) can be performed to check for signs of an immune response to an infection. To evaluate for inflammation and the risk of osteomyelitis, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) tests may also be performed.
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Imaging Test: An X-ray of the affected area should be prescribed to people who have been bitten or scratched by an animal to check for any fractures, foreign bodies that have been retained, osteomyelitis, or necrotizing infections. A magnetic resonance imaging scan (MRI) might be performed to further assess cases of probable osteomyelitis.
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Wound Culture: Wound cultures can be taken to detect local infections, and blood cultures can be taken if systemic infections are a concern. A sputum culture may help with a conclusive diagnosis in patients with respiratory problems. Meningitis patients need a lumbar puncture, and the cerebrospinal fluid (CSF) should be cultured to identify the causative organism.
How Is Pasteurella Multocida Infection Treated?
The treatment of Pasteurella multocida infection includes:
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Management of Uncomplicated Animal Injury: The wound should be washed and flushed with sufficient sterile water. The primary closure of the wound should be performed if required. If closure is done, enough space should be left between the sutures for drainage. Tetanus prophylaxis should be administered. For any injuries caused by animals, rabies prophylaxis should also be advised. Without injuries-related complications, these patients can typically be sent home with watchful monitoring. If antibiotic prophylaxis is administered, three to five days of oral therapy are sufficient. The patient needs to be reminded to get reevaluated if there are any symptoms of infection.
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Management of Complicated and Infected Injuries: A complicated injury includes systemic illness and spreading the injury to deeper soft tissues. Symptoms can advance quickly, even when undergoing oral antibiotic treatment. Therefore, patients with complex injuries should be given parenteral antibiotics (intravenous, intramuscular, or subcutaneous injections). If parenteral antibiotics are administered, they must be continued until the patient exhibits definite symptoms of resolved infection. Moreover, surgical therapy may be indicated for deeper soft tissue infections, such as wounds with damaged tissue, signs of abscess formation, or developing necrotizing infection symptoms.
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Antibiotic Prophylaxis: Oral administration of Amoxicillin and Clavulanate combination is the first-line antibiotic for prophylaxis or treatment of active infections. Any anti-Pasteurella antibiotic, such as Doxycycline, Penicillin V, Cefuroxime, Ciprofloxacin, or Levofloxacin, may be used in combination with an anti-anaerobic medication, such as Metronidazole or Clindamycin. Moreover, Ampicillin-Sulbactam, Piperacillin-Tazobactam, or Carbapenem monotherapy is the first-line parenteral antibiotic treatment.
What Are the Complications of Pasteurella Multocida Infection?
Complications could arise from an infected animal bite if prompt treatment is not initiated. Systemic diseases like bacteremia, endocarditis, meningitis, etc., may manifest in the worst-case scenarios. Osteomyelitis, septic arthritis, and abscess development are examples of local complications. The most typical cases of these regional consequences involve hand injuries.
Conclusion:
Pasteurella multocida is the most common infection due to an animal bite or scratch (sometimes an animal lick). The infection generally has a good prognosis, but in some cases, systemic complications can develop. Pasteurella multocida-related soft-tissue infections heal without complications, and the symptoms rapidly subside when appropriately treated. However, due to the high rates of complications, infections in hand have a worse prognosis. Osteomyelitis and septic arthritis are some of the possible complications that can cause long-term problems.
