Catfish spine envenomation and bacterial abscess withProteusandMorganella: a case report
Abstract
Abscess formation and cellulitis in the setting of envenomation are rare complications of handling catfish. To the best of our knowledge, isolation ofProteus vulgarishas not been previously recorded, and recovery ofMorganella morganiihas been reported in only one prior case from wound cultures in patients injured by catfish stings. We report a case of catfish envenomation characterized by abscess formation and cellulitis, in which wound cultures grew these unusual organisms.
A 52-year-old Chinese-American man was hospitalized with erythema and swelling of his right arm of 10 days’ duration after skin penetration by a catfish barb. An abscess of his right thumb had undergone incision and drainage, with purulent drainage sent for wound culture immediately prior to admission. Laboratory studies revealed elevated white blood count, sedimentation rate, and C-reactive protein. The patient was treated with intravenous ampicillin-sulbactam and vancomycin during his hospitalization, and symptoms improved. Wound cultures obtained prior to presentation grew manyProteus vulgarisandMorganella morganii. He was subsequently discharged on a 10-day course of oral ciprofloxacin and amoxicillin-clavulanate. At a 12-month telephone follow-up, the patient denied developing further symptoms and reported that the wound had healed completely without complication.
Although envenomation and secondary infection are not uncommon sequelae of handling catfish, the present case is unique by virtue of the infecting organisms isolated. Given the prevalence of injury from catfish stings, a review of the literature is presented in order to provide recommendations for prevention and treatment of catfish envenomation.
Introduction
Catfish have been farmed as food for the past several hundred years throughout the world, in Africa, Asia, Europe, and North America. One of the most commonly farmed catfish in the United States of America is channel catfish,Ictalurus punctatus, one of more than 1000 catfish species. Virtually all catfish, includingIctaluridae, possess spines on their dorsal and pectoral fins, which serve as defense mechanisms when they are agitated or disturbed [1]. In addition to inducing mechanical injury, the spines also contain venom glands, which, when compressed after the overlying sheath has been broken, release venom that can cause both a severe local inflammatory reaction and possible systemic symptoms. However, the most serious complications of catfish stings in humans involve bacterial superinfections. Waterborne organisms such asVibriospecies for saltwater infections andAeromonasfor freshwater infections have been isolated from sting wounds and have been commonly reported [2,3].
By contrast, we report a case of a channel catfish spine puncture complicated by aProteusandMorganellabacterial abscess, representing an apparently unique infectious complication of catfish injury.
Case presentation
A 52-year-old immunocompetent Chinese-American man with no significant past medical history, including an absence of chronic diseases, was injured while handling a catfish 10 days prior to admission while working as a fishmonger in a New York City supermarket. He had picked up a live channel catfish (I. punctatus) from a fish tank with his ungloved right hand, after which he was stung in the right nail groove of his thumb by the spine of the catfish. The patient experienced immediate and severe pain at the puncture site. As the day progressed, he developed pain, erythema, and swelling throughout his right thumb. Over the next few days, the patient reported an increase in pain from 1 out of 10 to 7 out of 10 in intensity, with radiation to his right forearm, and progressive erythema and swelling which extended proximally up his right arm. Subsequently, he sought medical attention from his primary care physician, who found the patient to be afebrile and prescribed amoxicillin-clavulanate to treat cellulitis and ibuprofen as needed for pain control. The patient revisited his physician 3 days later with the development of an abscess and no response to the antibiotic while remaining afebrile. The ibuprofen that he was taking for pain control likely served as an anti-pyretic and obscured possible fever. His doctor performed an incision and drainage procedure of the lesion and sent the purulent drainage for wound culture. He then referred the patient to the emergency department for admission and intravenous antibiotics. There, the patient was given 900mg intravenous clindamycin and tetanus immunization, as well as ibuprofen 600mg for pain control.
Upon admission, the patient reported the pain as 2 out of 10 diffusely in his right thumb. He described the pain as throbbing and intermittent, with radiation to his right forearm. The patient was non-toxic appearing, but in severe pain. Vital signs demonstrated a temperature of 96.9°F (36.1°C), pulse of 62 beats per minute, respiratory rate of 18, and blood pressure of 112/71mmHg. The physical examination was unremarkable aside from an indurated, red, firm 2cm swelling to the medial aspect of his right thumb that was tender to palpation, with surrounding erythema and warmth, and lymphangitic erythematous streaks that tracked medially to his antecubital fossa. The laboratory evaluation was unremarkable, including normal liver and renal panels, except for an elevated white blood cell count (WBC) of 13.2K/uL (80% neutrophils), sedimentation rate of 38mm/hour (reference range 0 to 13), and C-reactive protein of 4.5mg/dL (reference range 0 to 1). X-ray views of the thumb were negative for foreign body and gas (Figure1). There was no evidence of cortical irregularity or periosteal reaction to suggest osteomyelitis.
Figure 1
Right thumb radiographs taken on admission to the hospital.Plain films show cellulitis and edema of the skin overlying the interphalangeal joint of the first digit. There is no evidence of fracture, dislocation, or osteomyelitis.
The patient was initially treated with intravenous tobramycin, oral tetracycline, and intravenous ampicillin-sulbactam. Hydrogen peroxide immersion of his right thumb and wet to dry dressings were used for wound care. One day after admission, the patient’s WBC decreased to 7.8K/uL, and Gram stain from the wound on initial presentation revealed moderate Gram-negative bacilli and a few Gram-positive cocci in pairs. Ampicillin-sulbactam was continued and vancomycin was added for possible methicillin-resistantStaphylococcus aureuscoverage. After substantial relief of symptoms and reduced signs, including less erythema and induration, and normalization of the WBC, the patient was discharged and prescribed a 10-day course of oral ciprofloxacin and amoxicillin-clavulanate. Wound cultures obtained by his primary care physician grew manyProteus vulgarisandMorganella morganii. Table1shows the antimicrobial susceptibility data of the two case isolates. Both organisms, while susceptible to ciprofloxacin, with minimum inhibitory concentration (MIC) less than 0.25μg/mL, were resistant to ampicillin, with MIC greater than 32μg/mL. At a 12-month telephone follow-up, the patient denied developing further symptoms and reported that the wound had healed completely without complication.
Discussion
Over 1000 species of freshwater and saltwater catfish exist worldwide, with some weighing a few grams and others up to 200kg. They vary greatly in their adaptations to different ecological conditions. An Egyptian catfish,Malapterurus, contains electrical organs capable of causing a fatal electric shock in humans [1]. Candiru (genusVandellia) is a small Amazonian catfish that is attracted to urine and may penetrate the urethral orifice of mammals, including humans, requiring surgical intervention [2]. Almost all catfish have the ability to inflict extremely painful wounds with their pectoral and dorsal spines (Figure2). The freshwater catfishI. punctatusis capable of causing significant injury with its stings [1]. Contrary to popular belief, the prominent barbels (whiskers) characteristic of catfish are for sensory purposes only and are incapable of causing envenomation.
Figure 2
Photographs of channel catfish,Ictalurus punctatus, with exposed pectoral (A) and dorsal spines (B).Note the sharp and deeply serrated contours of the spines.
Envenomations generally occur when the catfish are being handled. They react to being grasped by lashing from side to side and locking their dorsal and pectoral spines, which are enclosed in an integumentary sheath containing venom glands, into a rigid and extended position (Figure3).
Figure 3
Dorsal spine of the striped eel catfish,Plotosus lineatus[1].Permission for use obtained from Darwin Press, Inc.
These sharp spines may penetrate skin, in the process damaging the delicate integumental sheath and exposing the venom glands. The retrorse barb (upturned tip) thatIctaluridaepossess on their spines is capable of lacerating skin, facilitating absorption of the venom and often necessitating surgical removal [1]. Catfish venom consists of hemolytic, dermonecrotic, edema-producing, and vasospastic factors, all of which have shown to be heat, pH, and lyophilization labile [3]. A second source of toxins, crinotoxins, is released by the epidermal cells of catfish skin upon agitation. These proteinaceous substances may coat the spine and become passively introduced into the wound upon skin breach [4]. Both venom and crinotoxin promote a marked localized inflammatory reaction, resulting in common findings of

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