A. HYDROPHILA IN AN INFECTED TIGER BITE CASE REPORT AEROMONAS HYDROPHILA WOUND INFECTION FOLLOWING A TIGER BITE IN NEPAL JM Easow and Rashmi Tuladhar Department of Clinical Microbiology, Manipal Teaching Hospital, Phulbari, Pokhara, Nepal Abstract. Aeromonas hydrophila is a rare human pathogen. Reports of zoonotic infection de- veloping after large feline bites are even rarer. We are documenting the first case of human wound infection with A. hydrophila following a tiger bite. The patient responded well following wound debridement, secondary suturing and combination antibiotic therapy. INTRODUCTION in humans due to A. hydrophila following a ti- ger bite. We are documenting the first case of Aeromonads were discovered more than such an infection in Nepal. 100 years ago. Their taxonomy has undergone a “sea of change” (Carnahan, 1993) but their CASE REPORT role in human infections are just being scien- tifically validated in the last few decades, pre- A 50-year-old man was mauled by an dominantly by three species: A. hydrophila, A. adult tiger in the village of Bhalam, Western caviae and A. veronii biotype sobria. Gas- Region, Nepal. He was immediately attended trointestinal tract infections are the common- to at a local clinic, where the wound was est source of aeromonads followed by wound cleaned and bandaged. For further radiologi- infections. In immunosuppressed individuals cal investigations, he was brought to our ter- or those with hepatobiliary disease, tiary care hospital within 2 hours of the bite. aeromonads can cause otitis media, menin- Upon arrival his vital signs were within the gitis, endocarditis, peritonitis, cholecystitis, normal range. On examination, he had mul- hemolytic uremic syndrome and septicemia tiple abrasions over his back and on the up- (Janda and Abbott, 1998). Zoonotic infections per third of his left forearm; there were mul- developing after large feline bites have been tiple lacerated wounds, the largest measur- recognized but their reports are limited. A. ing approximately 2 cm x 1 cm. There was hydrophila is a pathogen among fishes, swelling and tenderness over the elbow joint. snakes, lizards, frogs, turtles and other cold- He had difficulty in moving his fingers and there blooded animals. It causes infections follow- was pain on movement at the elbow joint. ing water related injuries (Semel and Radial pulses were palpable, and neurovas- Trenholme, 1990). To the best of our knowl- cular examination revealed no abnormality. Ra- edge there are no reports of wound infections diological investigation revealed a nondis- Correspondence: Dr Joshy M Easow, Department placed chip fracture of the upper third of the of Clinical Microbiology, Manipal Teaching Hospi- left ulna. The wound was washed thoroughly tal, Phulbari, P O Box 341, Pokhara 33701, Nepal. and dressed daily with povidone iodine. On Tel: 00977 9856021227; Fax: 00977-61-527862 the third day, the patient was febrile and pu- E-mail: [email protected] rulent discharge soaked the bandage. Blood Vol 38 No. 5 September 2007 867 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH and pus samples were sent for culture. Wound DISCUSSION debridement was performed under general Bite injuries account for 1-2% of all emer- anesthesia; multiple small lacerations were seen gency room visits annually in the USA, cost- over the forearm of which three were muscle ing over US$100 million; human bites are the deep and other two were bone deep. No pus most prevalent mammalian bites after those was seen in the deeper plane. The patient was of dogs and cats, accounting for 2-3% of bites empirically started on intravenous cloxacillin, (Goldstein, 1992), however this does not re- amikacin and metronidazole. A week later the flect the incidence as most bites are self wounds were closed by secondary suturing. treated, thus seldom reported. Mammalian The aerobic wound culture grew A. hydrophila bite wound infections are polymicrobial in na- and a fully sensitive strain of Escherichia coli. ture and the microbes isolated represent the Anaerobic culture was not performed. A. oral flora of the mammal, skin flora of the vic- hydrophila was resistant to penicillin by disk tim, and environmental contaminants of the diffusion method but sensitive to ciprofloxacin, wound. A bacteriological analysis of infected gentamicin, cefuroxime, cefotaxime and dog and cat bites reported that the most fre- trimethoprim-sulfamethoxazole. The patient quently isolated aerobes were Pasteurella fol- was discharged on ciprofloxacin and had an lowed by Streptococci, Staphylococci, Neis- uneventful recovery. seria, Corynebacterium and Moraxella; the The Aeromonas species was identified by commonest anaerobes were Fusobacterium, Gram’s staining of the purulent material, which Bacteroides, Porphyromonas, Prevotella and showed plenty of polymorphonuclear leuko- Propionibacterium (Talan et al, 1999). Descrip- cytes and gram-negative bacilli. It was inocu- tions of the microbes from animal bite wound lated on blood agar, chocolate agar and infection in humans reflect the evolution of MacConkey agar. Heavy growth of beta modern microbiology rather than any change hemolytic colonies was seen on blood agar in the actual etiology of the disease process and non-lactose fermenting colonies on (Love et al, 2000). A literature search for or- MacConkey Agar. They were motile, both ganisms associated with bite wound infections catalase and oxidase positive. It grew at 37ºC yielded many for cats, dogs and humans but and not at 4ºC. Colonies were buff-colored were limited for tiger bites as it is an uncom- and did not grow on TCBS. An array of bio- mon cause for wound infection in humans. The chemical tests was performed; the isolate was microbe isolated from tiger bite wound infec- a fermentative gram-negative bacillus; it was tion in humans was Pasteurella multocida. This anaerogenic and produced acid from glucose, commonly colonizes the oral cavity of tigers maltose, mannitol, mannose, arabinose, su- and other cats (Burdge et al, 1985; Woolfrey crose but not from lactose, sorbitol and sali- et al, 1985; Isotalo et al, 2000). P. multocida cin. It reduced nitrate, hydrolyzed esculin, has been reported to be isolated in pure cul- decarboxylated lysine, dihydrolysed arginine, ture from cat bite wound infections of humans produced hydrogen sulphide and indole on as early as the 1930s (Kapel and Holm, 1930). sulphide indole motility media. The Voges- Phenotypic variants of P. multocida have Proskauer’s test was positive. It did not utilize been reported from large cat bite wound in- citrate as a sole source of carbon. It did not fections in humans and the dental-gingival have urease and phenylalanine deaminase junction of several species of large cats activity. Based on these phenotypic charac- (Woolfrey et al, 1985). The sucrose negative teristics, the isolate was identified as variants of P. multocida belong genotypically Aeromonas hydrophila (Abbott et al, 2003). to two distinct groups; those isolated from 868 Vol 38 No. 5 September 2007 A. HYDROPHILA IN AN INFECTED TIGER BITE large cat bite wounds belong to a new taxon ported (Hsueh et al, 1998). During this period (taxon 45 of Bisgaard) (Burdge et al, 1985). we did not isolate any strains of Aeromonas Bergeyella zoohelcum was previously known from our in-patients or from the hospital envi- as Weeksella zoohelcum; historically this spe- ronmental samples which we studied as a part cies was referred to as “CDC group II j”. It was of our hospital infection control surveillance. isolated from a wound infection in a 35-year Since we did not isolate Aeromonas from old man attacked by a Siberian tiger (Isotalo other probable sites, this supports our hypoth- et al, 2000). Neisseria weaveri, previously esis the source of the bacteria was the tiger known as “CDC group M-5”, is a gram-nega- oral flora might sound better. tive bacillus associated with dog and cat bites. Large numbers of bacteria have been It was isolated from a wound infection in a 7 described following animal bites. This empha- year old attacked by an adult white Siberian sizes the need to characterize the oral flora of tiger (Christian et al, 2002). felines and continuously monitor antibiotic Aeromonas wound infections have an in- susceptibility patterns. It will help emergency cubation period of 1-2 days and may be even room physicians in initiating appropriate anti- as short as 8 hours. It resembles streptococ- biotic therapy following feline bites. Proper ir- cal infection due to its rapid progression. Tis- rigation, debridement, delayed wound closure sue adherence, cytotoxins, enterotoxin pro- and appropriate antibiotic selection are essen- duction and extracellular substances contrib- tial (Minnaganti et al, 2000). Flouroquinolones ute towards its pathogenecity (Minnaganti et are advocated as the drug of choice for treat- al, 2000). The origin of our isolate could have ment of Aeromonas infection. If the strain is been either from the soil in the field or a part resistant to nalidixic acid and sensitive to of the tiger’s oral flora (colonization/infection) ciprofloxacin, it indicates a mutation in the or a nosocomial pathogen. We visited the site gyrA gene; a second mutation of resistance is and observed that the incident had occurred easily attainable thus generating a minimum in a dry field. Soil samples collected from the inhibitory concentration (MIC) of ciprofloxacin site were processed for aerobic culture. A. above the cut-off point (Vila et al, 2002); un- hydrophila was not isolated from the soil cul- der such circumstances, ciprofloxacin should ture. An outbreak of Aeromonas wound infec- be avoided. Gentamicin and amikacin have tions among participants of a “mud football” better activity than tobramycin (Overman and competition was reported in Australia. The Janda, 1999). Empiric therapy with penicillins source of Aeromonas was identified to be a or cephalosporins is of no therapeutic use. An- nearby river and probably the irrigation sys- tibiotic resistance in Aeromonas is due to chro- tem which was used to irrigate the football field mosomally mediated inducible beta- (Vally et al, 2004).