Antimicrobial Therapy for Pasteurella multocida Empyema in Immunocompetent Adults
Pasteurella multocida is a gram-negative zoonotic coccobacillus. It is well known to cause soft tissue infections in humans after bites from domestic pets like cats and dogs. It can also cause bacteremia, septic shock, endocarditis, meningitis, cardiac valve infections, osteomyelitis, prosthetic joint infections, and rarely glossitis, peritonitis, and ocular infections.1–5 The respiratory tract is the second most common site of P. multocida infection after soft tissue infection. These infections occur through inhalation of the contaminated secretions of the animals and can occur without bites or scratches.6,7 Older age, underlying pulmonary pathologies such as bronchiectasis and chronic obstructive disease, and immunosuppressive states such as HIV, poorly controlled diabetes, or malignancy predispose patients to P. multocida pulmonary disease which may be pneumonia, empyema, or lung abscess.8–10 This article discusses our experience in managing P. multocida empyema and literature review of the antibacterial therapy.
A 67-year-old female nurse with a medical history of systemic lupus erythematosus presented with cough and fever. Intravenous ceftriaxone and azithromycin were started for community-acquired pneumonia. However, her fever continued to spike. Computed tomography of her chest showed bilateral parapneumonic effusions requiring chest tube drainage. Her blood cultures grew P. multocida. Antibiotics were switched to ampicillin-sulbactam as per culture sensitivity. On the fifth day, the chest tube was removed, and on the seventh day, the patient was discharged on levofloxacin. The patient did not have any signs of recent or remote cat bites. Besides taking prednisone 5 mg daily since last 3 weeks, she was not on any immunosuppressive therapy. She was taking hydroxychloroquine for many years. Her leukocyte count on admission was 9.4 K/μL and glycosylated hemoglobin was only 5 units. On further questioning, she revealed volunteering as a cats' rescuer in free time. She used protective precautions while handling them and was never scratched or bitten by any cat. Possibly, she had tracheobronchial colonization of P. multocida through inhalation of the secretions of the cats that got complicated because of immunosuppressant prednisone taper therapy.
Parapneumonic effusions secondary to P. multocida can be catastrophic.11,12 Based on several case studies, the sensitive antibiotics for P. multocida infections are penicillins, including amoxicillin-clavulanate, ampicillin-sulbactam, and piperacillin-tazobactam. Other sensitive antibiotics are doxycycline, fluoroquinolones, third- or higher-generation cephalosporins, carbapenems, and trimethoprim-sulfamethoxazole. Semisynthetic penicillins such as oxacillin or dicloxacillin, first-generation cephalosporins, and clindamycin fail to show significant in vitro activity against P. multocida. The benefit of using long-term macrolides has been shown in chronic respiratory P. multocida infections.13 Among macrolides, some strains of Pasteurella species are susceptible to erythromycin, azithromycin, and clarithromycin, but lower susceptibility is reported with telithromycin (89.4%).14 Fifth-generation cephalosporin, ceftaroline, shows sensitivity against almost all bacterial infections that occur with animal bites. It is the most active agent among cefazolin, ceftriaxone, ertapenem, ampicillin-sulbactam, azithromycin, doxycycline, and sulfamethoxazole-trimethoprim against all Pasteurella species, including P. multocida subsp. multocida and P. multocida subsp. septica.15 Considering the severe spectrum of P. multocida infections, vaccination is also being developed.