Overview
Definition:
Cat bite infections are a significant concern in pediatrics, primarily due to the high likelihood of bacterial inoculation into deeper tissues from the sharp teeth of cats
Pasteurella multocida is the most common pathogen isolated from cat bites, accounting for over 50% of infections.
Epidemiology:
Cat bites are common in children, with boys being more frequently affected
While many bites are superficial, deep puncture wounds pose a higher risk of infection
Pasteurella multocida is ubiquitous in the oral flora of domestic cats and is readily transmitted during a bite.
Clinical Significance:
Prompt and appropriate management of cat bite infections is crucial to prevent serious local and systemic complications, including cellulitis, abscess formation, osteomyelitis, septic arthritis, and in rare cases, bacteremia or meningitis
Understanding Pasteurella coverage is key to effective antimicrobial therapy.
Clinical Presentation
Symptoms:
Local signs of infection typically appear within 24-48 hours of the bite
These include erythema, warmth, tenderness, and swelling at the bite site
Purulent discharge may be present
Systemic symptoms such as fever, malaise, and lymphadenopathy can also occur.
Signs:
On physical examination, findings may include a localized inflammatory response at the bite wound
The wound may appear red, swollen, and tender to palpation
Palpable lymphadenopathy in the draining lymphatic basin is common
Vital signs may be normal in uncomplicated cases, but fever may indicate systemic involvement.
Diagnostic Criteria:
Diagnosis is primarily clinical, based on the history of a cat bite and the presence of signs and symptoms of infection
Microbiological confirmation is usually reserved for severe or recurrent infections, or when an abscess is present
Culture and sensitivity testing of wound exudate or aspirate is recommended.
Diagnostic Approach
History Taking:
A detailed history should include the circumstances of the bite (domestic vs
stray animal, depth of the wound, location), time since the bite, and any immediate wound care
Immunization status (especially tetanus and rabies) and any underlying medical conditions (e.g., immunocompromise, diabetes) are important
Note any known allergies.
Physical Examination:
A thorough physical examination should focus on the bite wound, assessing its depth, any signs of penetration into underlying structures like joints or bones, and the extent of surrounding cellulitis
Regional lymph nodes should be palpated for enlargement and tenderness
A general examination to assess for systemic signs of infection is also necessary.
Investigations:
For uncomplicated, superficial bites without signs of infection, laboratory investigations may not be necessary
However, in cases of deep wounds, signs of systemic infection, or immunocompromised patients, complete blood count (CBC) with differential, C-reactive protein (CRP), and blood cultures may be indicated
Wound cultures are essential if purulent discharge is present or if initial treatment fails
Radiography may be considered if there is suspicion of foreign body or underlying bone/joint involvement.
Differential Diagnosis:
Other bacterial infections (e.g., Staphylococcus, Streptococcus), viral infections (e.g., rabies), and non-infectious inflammatory processes can mimic cat bite infections
Animal bite injuries themselves can also cause significant trauma and tissue damage independent of infection.
Management
Initial Management:
Immediate management includes thorough wound cleaning with soap and water
Copious irrigation is critical
Antiseptic solutions may be used
Tetanus prophylaxis should be administered if indicated based on the patient's immunization history
The decision for rabies prophylaxis depends on the animal's status and local guidelines.
Medical Management:
Antibiotic prophylaxis or treatment is a cornerstone of managing cat bite infections, with a focus on Pasteurella coverage
For prophylaxis in low-risk bites, amoxicillin-clavulanate is the drug of choice, typically given for 3-5 days
For established infections, amoxicillin-clavulanate is also first-line, with doses adjusted for age and weight
Duration of treatment is typically 7-14 days, depending on the severity
Alternatives include clindamycin or a combination of a beta-lactamase inhibitor with an appropriate cephalosporin or fluoroquinolone if penicillin allergy exists
Document common pediatric dosing for amoxicillin-clavulanate (e.g., 25-45 mg/kg/day divided BID or TID).
Surgical Management:
Puncture wounds, especially those on the hands or over joints, generally should not be surgically debrided or sutured due to the high risk of trapping bacteria
If an abscess forms, surgical drainage is indicated
Debridement may be necessary for extensive tissue necrosis or if there are signs of necrotizing fasciitis.
Supportive Care:
Elevation of the affected limb and pain management with analgesics are important
Close monitoring for signs of worsening infection or systemic spread is crucial
Patients should be instructed on wound care and signs of complications to report immediately.
Complications
Early Complications:
Cellulitis, local abscess formation, lymphadenitis, tenosynovitis, and septic arthritis are common early complications
Less commonly, osteomyelitis or direct spread to joints can occur.
Late Complications:
Chronic osteomyelitis, persistent joint dysfunction, and disfigurement from severe infections or inadequate treatment can be late sequelae
Scarring at the bite site is also common.
Prevention Strategies:
Prompt and thorough wound cleansing is paramount
Judicious use of antibiotic prophylaxis, particularly for deep puncture wounds, bites on the hands, or in immunocompromised individuals, significantly reduces infection rates
Educating parents and children about safe interaction with animals is also important.
Prognosis
Factors Affecting Prognosis:
Prognosis is generally good with prompt diagnosis and appropriate management
Factors negatively influencing prognosis include delayed presentation, deep puncture wounds, immunocompromised status, and development of complications like osteomyelitis or septic arthritis.
Outcomes:
With timely and effective antibiotic therapy and wound care, most cat bite infections resolve without significant sequelae
However, severe infections can lead to long-term morbidity.
Follow Up:
Follow-up is essential to ensure resolution of infection and to monitor for any delayed complications
The duration of follow-up depends on the severity of the initial infection and the presence of any complications.
Key Points
Exam Focus:
Pasteurella multocida is the most common pathogen in cat bite infections
amoxicillin-clavulanate is the drug of choice for prophylaxis and treatment
Avoid primary closure of puncture wounds
Tetanus and rabies prophylaxis are important considerations.
Clinical Pearls:
Always consider the possibility of Pasteurella in cat bites
Irrigate wounds generously
For bites on hands or over joints, even if seemingly minor, be vigilant for deeper infections
Prophylactic antibiotics are often warranted for puncture wounds.
Common Mistakes:
Underestimating the risk of infection with seemingly superficial bites
Premature closure of puncture wounds
Inadequate wound irrigation
Not initiating appropriate antibiotic prophylaxis or treatment promptly
Failing to consider tetanus or rabies prophylaxis.