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Patients with bite wounds should be seen in follow-up within 24 hours of initial treatment. Any increase in pain, swelling, or cellulitis should prompt hospitalization.
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Empiric and prophylactic antibiotic therapy should be directed against the microorganisms found most frequently in bite wound infections. The most common bacteria vary according to the biting animal, the environment of the bite, and the type of wound infection, if present. Empiric therapy for dog and cat bite wounds should be directed against Pasteurella, Streptococci, Staphylococci, and anaerobes, while empiric therapy for human bite wounds should include coverage against Streptococci, Staphylococci, E.corrodens, and anaerobes41 (Table 46–9).
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Bite wounds that occur in the aquatic environment require additional empiric antibiotics to cover microorganisms present in the water, regardless of the type of biting animal. The choice of antibiotic used for aquatic bite wounds is determined by the type of water in which the bite occurred. Injuries that occur in saltwater should receive antibiotic coverage for Vibrio spp. such as ceftazidime or cefotaxime plus doxycycline or ciprofloxacin. Freshwater wounds should be treated with antibiotics that cover A. hydrophila and Pseudomonas aeruginosa; ceftazidime, imipenem, or ciprofloxacin are reasonable options.
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Many microorganisms isolated from infected dog and cat bite wounds are beta-lactamase producers. Optimal empiric therapy should include either a combination of a beta-lactam antibiotic and a beta-lactamase inhibitor, a second-generation cephalosporin with anaerobic activity (e.g., cefoxitin), or combination therapy with either penicillin and a first-generation cephalosporin or clindamycin and a fluoroquinolone. Antimicrobial agents of choice for dog bite wound infections are amoxicillin/clavulanic acid and ampicillin/sulbactam. Metronidazole plus ampicillin offers another good choice.35 One study has evaluated the efficacy of prophylactic trimethoprim–sulfamethoxazole for dog bites, and demonstrated a nearly significant reduction in the incidence of hand infections.23 The role of clindamycin, increasingly used for coverage of community-acquired methicillin-resistant S. aureus, has not been examined in bite wound infections.
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Recent surveillance data of Pasteurella strains isolated from infected bite wounds in humans indicate that amoxicillin, cefotaxime, azithromycin, and clarithromycin are all effective as single agents.42 Trimethoprim–sulfamethoxazole usually offers good coverage for Pasteurella. In addition, doxycycline, minocycline, and several fluoroquinolones are effective, but may not be appropriate drugs for pediatric patients.
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Amoxicillin–clavulanic acid and moxifloxacin demonstrate the best activity against the most frequently isolated strains of bacteria from human bite wounds. E. corrodens has a peculiar susceptibility pattern, being susceptible to penicillin, but resistant to penicillinase-resistant penicillins, such as dicloxicillin.43E. corrodens has been found to be uniformly resistant to clindamycin.43 Erythromycin, antistaphylococcal penicillins, first-generation cephalosporins, metronidazole, and most aminoglycosides also have poor activity against E. corrodens. In vitro susceptibility testing of 151 clinical strains of E. corrodens found all isolates to be sensitive to ampicillin/sulbactam, amoxicillin/clavulanic acid, and cefoxitin. Relative resistance to doxycycline was found in 17.8%.43 For penicillin-allergic pediatric patients, a combination of antibiotics may be necessary for empiric coverage of human bite wounds, including clindamycin plus a second- or third-generation cephalosporin.10
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Marine environment wounds should be treated with doxycycline and a third- or fourth-generation cephalosporin or a fluoroquinolone. Patients with bite wounds occurring in freshwater should receive a third- or fourth-generation cephalosporin.
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Ciprofloxacin, like other fluoroquinolones, is associated with arthropathy and histopathologic changes in weight-bearing joints of juvenile animals. The American Academy of Pediatrics states that the use of fluoroquinolones (e.g., ciprofloxacin, gatifloxacin, levofloxacin, moxifloxacin) in children younger than 18 years of age may be justified. The most recent recommendations for the use of fluoroquinolones in children state two circumstances in which they may be useful: (1) infection is caused by multidrug-resistant pathogens, and (2) parenteral therapy is not feasible and no other effective oral agent is available. The drugs should be used only after careful assessment of the risks and benefits for the individual patient and after these benefits and risks have been explained to the parents or caregivers.44 Doxycycline and minocycline are generally not recommended for use in children younger than 8 years owing to risk for tooth enamel hypoplasia and discoloration.
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Patients with infected bite wounds should be reevaluated 24 hours after initial treatment. If the wound appears clinically worse, inpatient therapy is required. If the condition is better, further follow-up can be dictated by the return of signs or symptoms of infection. With initial adequate wound care, most bite wound infections will resolve after 5–7 days of antibiotics. High-risk wounds that are initially left open should be considered for delayed closure in 3–5 days. The results of cultures should guide treatment of refractory infections.