Serratia marcescens bullous cellulitis after iguana bites

Abstract

To the Editor: Iguana iguana, a natural inhabitant of Southern Mexico and Brazil, is becoming increasingly popular as a US household pet, and there are an estimated 700,000 of these creatures within the United States.1Rosen T. Jablon J. Infectious threats from exotic pets: dermatological implications.Dermatol Clin. 2003; 21: 229-236Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar We report herein two cases of Serratia marcescens bullous cellulitis after the bite of I iguana and discuss empiric antibiotic therapy. An otherwise healthy 54-year-old man presented 2 days after being bitten by his Mexican pet iguana (I iguana) on the posterior midcalf. He developed a circumferential area of indurated and tender erythema with small vesicles spread throughout the site (Fig 1). A nonbacteriostatic saline aspirate of the cellulitis grew S marcescens. The only oral agent to which the isolate was sensitive was trimethoprim-sulfamethoxazole (TMP-SMX). The patient was placed on TMP-SMX 160 to 800 mg twice daily; the eruption resolved uneventfully within 2 weeks. A similar case presented in a healthy 25-year-old man who was bitten on the medial aspect of the left ankle by his pet Mexican iguana (I iguana). The following day, a blister appeared at the site. Within 48 hours, the blister evolved into a hemorrhagic bulla (Fig 2). Fluid obtained by sterile aspiration of the bulla yielded solitary growth of S marcescens, which was sensitive to parenteral aminoglycoside antibiotics and oral TMP-SMX. He was subsequently treated in the same manner as the first case, with a resolution of the signs and symptoms in 10 days. There is a paucity of data regarding the expected oral flora of I iguana, so it is not clear if S marcescens is a normal constituent for this reptile. In our cases, S marcescens was the only organism identified in bacterial culture of lesional aspirates. Both cases are unique in that there has been only one reported case of S marcescens nonbullous cellulitis after an iguana bite2Hsieh S. Babl F.E. Serratia marcescens cellulitis following an iguana bite.Clin Infect Dis. 1999; 28: 1181-1182Crossref PubMed Scopus (43) Google Scholar and only one report of bullous cellulitis that was determined to be solely caused by S marcescens.3Cooper C.L. Wiseman M. Brunham R. Bullous cellulitis caused by Serratia marcescens.Int J Infect Dis. 1998; 3: 36-38Abstract Full Text PDF PubMed Scopus (19) Google Scholar The latter case occurred within the setting of chlorhexadine solution contaminated by S marcescens.3Cooper C.L. Wiseman M. Brunham R. Bullous cellulitis caused by Serratia marcescens.Int J Infect Dis. 1998; 3: 36-38Abstract Full Text PDF PubMed Scopus (19) Google Scholar Antibiotics used to treat S marcescens infection include third-generation cephalosporins, aminoglycosides, carbapenems, fluoroquinolones, and TMP-SMX.3Cooper C.L. Wiseman M. Brunham R. Bullous cellulitis caused by Serratia marcescens.Int J Infect Dis. 1998; 3: 36-38Abstract Full Text PDF PubMed Scopus (19) Google Scholar Other than parenteral aminoglycoside antibiotics, S marcescens isolates from our patients were sensitive to TMP-SMX. However, the current recommendations for the prophylactic treatment of reptile bite wounds is amoxicillin-clavulanate, presumably for coverage of enteric Gram-negative bacteria and anaerobes.4American Academy of Pediatrics Committee on Infectious DiseasesPickering L.K. Baker C.J. Long S.S. McMillian J.A. Red book: 2006 report of the Committee on Infectious Diseases. 27th ed. American Academy of Pediatrics, Elk Grove, IL2006: 191Google Scholar The findings in our two cases—and in those of a previous report of an infected iguana bite2Hsieh S. Babl F.E. Serratia marcescens cellulitis following an iguana bite.Clin Infect Dis. 1999; 28: 1181-1182Crossref PubMed Scopus (43) Google Scholar—are particularly important because the current recommendations for prophylactic treatment of reptile bites would not routinely cover for S marcescens as an infecting microbe. In a recent study examining the susceptibility of various microbial pathogens, only 1.2% to 2.7% of S marcescens isolates were susceptible to amoxicillin-clavulanate, while 96% to 96.8% were resistant.5Dowzicky M.J. Park C.H. Update on antimicrobial susceptibility rates among gram-negative and gram-positive organisms in the United States: results from the Tigecycline Evaluation and Surveillance Trial (TEST) 2005 to 2007.Clin Ther. 2008; 30: 2040-2050Abstract Full Text PDF PubMed Scopus (55) Google Scholar In the setting of I iguana bites with clinical evidence of infection, empiric therapy with TMP-SMX or a fluoroquinolone antibiotic is advisable until culture results and sensitivities are available. Both patients were placed on TMP-SMX according to isolate sensitivities, and symptoms resolved within 2 weeks.