CASE REPORT

Thoracic vertebral osteomyelitis following catfish spine impalement Elizabeth Sateren-Zoller, PA-C; Manish S. Sharma, MBBS, MS, MCh; Thiha Tin, MD; Dominic M. Cannella, MD; Douglas Chyatte, MD

ABSTRACT Although rare, thoracic osteomyelitis can occur when toxins from a catfish spine impalement to the hand spread via the blood. This article describes diagnosis and management of this condition in a man who required hospitalization for debilitating back pain that developed 3 weeks after the initial injury. Keywords: catfish spine, injury, thoracic osteomyelitis, hematogenous spread, Staphylococcus aureus, vertebral

CASE A 51-year-old man presented to the ED with a 1-week history of spontaneous, acute-onset, right-sided, mid-thoracic pain. The pain worsened with activity and deep inspiration, and improved with immobilization and opioids. He did not report nausea, vomiting, shortness of breath, neurologic symptoms, or fever. He was treated conservatively for 3 weeks (rest, muscle relaxants, and opioids) but did not improve. After cardiac, pulmonary, and gastrointestinal causes were excluded, a contrast-enhanced MRI of the thoracic spine was obtained, revealing bone marrow edema in the T7 and T8 vertebral bodies. Avid postcontrast enhancement was noted at these levels and in the prevertebral and bilateral paraspinal locations extending from T5 to T9 (Figure 1). He was diagnosed with T7-T8 osteomyelitis with prevertebral and paraspinal abscess. The patient was admitted to the hospital and evaluated by the departments of neurosurgery and infectious disease. Upon additional focused questioning, he reported that he had been impaled in the right hand by a catfish fin spine about 3 weeks before the onset of his symptoms of thoracic pain. Shortly following the injury, his hand became intensely At the Mayo Clinical Health System in Mankato, Minn., Elizabeth Sateren-Zoller practices neurosurgery, Manish S. Sharma is a consultant in neurologic surgery, Thiha Tin is an attending physician in internal medicine and infectious disease, Dominic M. Cannella is a consultant neurosurgeon in the Department of Neurosurgery at the system’s Immanuel St. Joseph Hospital, and Douglas Chyatte is a professor of neurosurgery. The authors have disclosed no potential conflicts of interest, financial or otherwise. DOI: 10.1097/01.JAA.0000455659.73037.ed Copyright © 2014 American Academy of Physician Assistants

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FIGURE 1. Contrast-enhanced sagittal (a, b) and axial (c)

MRIs indicating avid contrast enhancement in the T7 and T8 vertebral bodies with additional paraspinal and prevertebral contrast enhancement extending from T5 to T9

painful and edematous; this resolved spontaneously within 8 days. He denied associated symptoms of fever, erythematous streaking over his right arm, or tender axillary lymphadenopathy at that time and did not seek medical attention. Two weeks later, the patient developed midthoracic pain. On examination, the patient was comfortable at rest and afebrile with normal vital signs. A neurologic examination www.JAAPA.com

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CASE REPORT

Key points As commercial catfish farming grows in the United States, clinicians need to be familiar with catfish-related injury and management. Untreated catfish spine impalement injury may lead to bacteremia, deep soft-tissue infection, nerve injury, and septic arthritis. Hematogenous seeding of distant sites, such as the thoracic spine, is rare. The most common causative organisms found in bacterial infections related to catfish spine injury are Streptococcus and Staphylococcus species. Treatment of catfish spine injury includes irrigation and scrubbing with soap, followed by immersion in warm water and tetanus prophylaxis. Antibiotics may be necessary in more serious cases. In general, treatment is nonoperative.

revealed a band of hyperesthesia over the right chest wall below the nipple, but was otherwise normal. Plain radiographs of the right hand were obtained, which did not demonstrate a foreign body. The patient’s erythrocyte sedimentation rate (ESR) was 110 mm/hour (normal range, 0 to 22 mm/hour) and his C-reactive protein (CRP) level was 140.7 mg/L (normal, none detected). All other hematobiochemical parameters were normal, including viral markers for hepatitis, antinuclear, antimitrochondrial, and antismooth muscle antibodies. After a CT-guided aspiration of the area of thoracic spine enhancement, the patient was started on empiric IV antibiotic therapy with ceftriaxone, metronidazole, and vancomycin. Cultures obtained by CTguided aspiration and blood cultures grew methicillinsensitive Staphylococcus aureus sensitive to all panel antibiotics. The patient responded to the empiric antibiotic regimen, which was subsequently modified to IV ceftriaxone and oral metronidazole. After blood cultures became sterile, he was discharged, completing 10 total days of IV ceftriaxone and oral metronidazole. This was followed by 9 weeks of oral ciprofloxacin and 18 weeks of oral cephalexin. At 6 months follow-up, the patient had mild localized thoracic pain, but remained neurologically normal. The ESR and CRP fell to 18 mm/hour and 0.6 mg/L, respectively, and antibiotic therapy was discontinued. A repeat MRI of the thoracic spine revealed marked radiologic improvement. DISCUSSION S. aureus is the most common organism causing vertebral osteomyelitis and accounts for almost half of all infections caused by hematogenous spread, typically from invasive procedures, vascular catheters, or soft-tissue or skin infections.1-4 Aerobic gram-negative pathogenic bacteria are the next most common pathogens.3,4 Urinary tract infections secondary to Escherichia coli, Proteus, Enterobacter, and Klebsiella are an important source of infection, especially in older patients and those who are immunocompromised www.JAAPA.com

TABLE 1.

Timeline illustrating the clinical course following catfish spine impalement and thoracic osteomyelitis.

Onset

Catfish fin spine impalement and onset of right hand pain and edema

Week 1

Spontaneous resolution of right hand soft-tissue symptoms

Week 3

Onset of thoracic pain

Week 6

Diagnosis of thoracic osteomyelitis and initiation of antibiotic treatment

Week 8

Discontinuation of IV antibiotics and initiation of oral ciprofloxacin

Week 17 Modification of oral antibiotics to oral cephalexin Week 35 Discontinuation of oral antibiotics. Marked clinical and radiologic improvement

or have diabetes. In postsurgical patients, coagulase-negative staphylococci, specifically S. epidermidis, and anaerobes, specifically Propionibacterium acnes, have been commonly implicated. In patients with a history of IV drug use, Pseudomonas aeruginosa and Serratia marcenscens have been found to be responsible organisms, though the commonest pathogen in this patient population is S. aureus. Though rarer in developed countries, vertebral osteomyelitis due to Mycobacterium tuberculosis and Brucella species is prevalent in endemic areas.1,2,4,5 In about half of all cases, a source is unidentifiable.1,3,6 Vertebral osteomyelitis is often caused by hematogenous seeding, as the source of the infection is often distant, and arterial and venous routes of spread are possible.2,3,6 Infections may be spread to the spine via the arterial route from anywhere in the body. Venous mechanisms are believed to be from a pelvic source to the spine.5,7 Common predisposing factors include older age, diabetes, end-stage renal disease, recent trauma, recent spinal surgery, recent invasive procedures, and IV drug use. Classical presenting symptoms include back pain, point spinal tenderness, fever, and rapidly progressive motor and sensory deficits, especially if there is an associated epidural abscess.2,3,5 Vertebral osteomyelitis is most often found in the lumbar spine, then thoracic and cervical spine.1,5,6 Diagnosis is often delayed by 42 days to 6 months because the presenting symptoms may mimic common mechanical or degenerative causes of back pain.1,2,6 DIAGNOSTIC TESTING Diagnostic testing includes hematobiochemical studies, plain radiographs, CT scan, and contrast-enhanced MRI. Leukocytosis is a nonspecific finding, as are elevated ESR and CRP levels. However, the latter are more specifically associated with active infection. Blood cultures should always be drawn and authorities have recommended that positive blood cultures obviate the need for a biopsy unless Volume 27 • Number 11 • November 2014

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Thoracic vertebral osteomyelitis following catfish spine impalement

MANAGEMENT Initial antibiotic therapy must be broad-spectrum and empirically directed at the most common pathogens: methicillin-sensitive S. aureus and gram-negative aerobes such as E. coli.1,8 Once the causative organism has been identified, broad-spectrum antibiotic therapy can be modified to include appropriate, culture-sensitive antibiotics. Although most literature supports a 4- to 6-week course of IV antibiotics, evidence suggests that early transition from IV to oral, highly bioavailable antimicrobials, such as fluoroquinolones, may be similarly effective in uncomplicated cases.4,6 The duration of antibiotic therapy, however, must be decided on a case-by-case basis depending on improving radiologic, laboratory, and clinical parameters. Most patients with hematogenous spinal osteomyelitis do not require surgical intervention and can be treated with medical management alone, consisting of parenteral, then oral antibiotics and analgesics. Indications for surgery may include a lack of response to antibiotics, presence of an abscess requiring surgical drainage, vertebral instability, and infections following instrumented spinal surgery.1,4,6,9 Follow-up for patients affected with spinal osteomyelitis involves monitoring symptomatic improvement, repeated clinical evaluation focusing on the neurologic examination, radiologic surveillance, and observing trends toward normalization of hematologic parameters such as the leukocyte count, ESR, and CRP.4 CATFISH INJURIES Catfish are a group of diverse, bottom-feeding, ray-finned fish with prominent barbels that resemble a cat’s whiskers. All species of catfish have eight barbels which serve a touch/ taste function and, contrary to popular belief, are harmless. About 3,000 species of catfish are recognized in both fresh and salt waters. In the United States, more than 80,000 acres of water are used for commercial catfish farming.10 In Minnesota, the Department of Natural Resources notes three genera: the flathead (Pylodictis olivaris); the yellow (Ameiurus natalis), brown (Ameiurus nebulosus) and black (Ameiurus melas) bullhead; and the channel catfish (Ictalurus punctatus).11 All the Minnesotan native species have three serrated bony spines located within the single dorsal and bilateral pectoral fins (Figure 2). These spines defend against predators and extend rigidly to a vertical (90-degree angle) position from a flattened one when a threat is encountered. JAAPA Journal of the American Academy of Physician Assistants

Microscopic anatomy of these spines demonstrates venomproducing glands deep to the epidermal layer. Rigid impalement of the spine into a predator causes the underlying glands to rupture and release toxic proteins into the wound, resulting in envenomation.12 Envenomation can result in intense pain lasting for up to 6 hours, local edema, erythema, and occasional cutaneous necrosis, but systemic manifestations are rare. More catfish injuries have been reported to the hands of freshwater fishermen than to marine fishermen.12 Bacterial infections are most commonly caused by Streptococcus and Staphylococcus species.13 Occasionally, Vibrio, Pseudomonas, or Edwardsiella species may be cultured.14-16 Fungal infections are usually caused by Sporothrix schenckii.13 Human catfish injuries result when these innocuouslooking fish are handled incorrectly. In the presence of a local host reaction disproportionate to the extent of physical injury, clinicians should suspect either envenomation, a superimposed bacterial infection, exposure to noxious crinotoxins, or the retention of a part of the catfish spine as a foreign body.11,17 Catfish injuries have resulted in deep soft-tissue infections (sometimes requiring amputation), nerve injury, radial artery injury, septic arthritis, and even a fatal heart perforation.18-21 A review of literature indicates that this is the first report of spinal osteomyelitis resulting from a catfish injury. The rarity of this event raises the question of causation or coincidence. The patient was diagnosed with osteomyelitis about 3 weeks after a soft-tissue injury due to a catfish fin spine. This fits temporal causation. The pathogen was identified first on blood culture and confirmed by a CT-guided biopsy as S. aureus, establishing a hematogenous spread. We hypothesize that the catfish-induced hand injury was the only chronologically relevant source of infection in the pathogenesis of spinal osteomyelitis, as this patient was an otherwise

ILLUSTRATION COURTESY OF THE MAYO CLINIC, ROCHESTER, MINN.

polymicrobial infection is suspected.1,6 Radiographic evidence of osteomyelitis on plain radiograph, CT, and bone scans can be misleading, especially in patients with degenerative disk disease. Gadolinium-enhanced MRI is the gold standard and confirms the extent of bony involvement, as well as specific involvement of the spinal cord, dura, and extradural soft tissues.1 MRI can direct a subsequent, percutaneous CT-guided biopsy, which has a 47% to 100% yield. A positive culture not only establishes the diagnosis, but can also be used to direct antimicrobial pharmacotherapy.1,5

FIGURE 2. Schematic diagram illustrating the hypothesized

hematogenous spread of S. aureus from a catfish spine induced hand injury to the thoracic spine. www.JAAPA.com

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CASE REPORT

healthy man with no history of diabetes, renal failure, autoimmune disease, immunosuppression, hepatitis, or IV drug use. Catfish injuries have been reported both within the United States and abroad, and frequently are responsible for deep soft-tissue infections secondary to S. aureus.12,13,22-24 TREATMENT The initial treatment of catfish-induced soft-tissue injuries involves thorough irrigation and scrubbing with soap and subsequent immersion in warm water or 0.9% sodium chloride solution at 45° to 50° C (113° to 122° F) for 60 to 90 minutes. Catfish toxins are thought to be heat labile and should respond to this regimen. The toxin also induces vasoconstriction, so warm water produces vasodilation and helps wash away the toxin, reduces local concentrations, and relieves pain. Embedded catfish spines should be removed and radiographs obtained to rule out a retained foreign body. Administer tetanus prophylaxis and analgesics.12,23,24 Local instillation of bupivacaine has been reported to be effective.23 Splint the affected extremity. Superficial abrasions and minor lacerations may be managed with serial wound inspections and delayed primary surgical closure, if needed. More serious injuries can be treated empirically with antibiotics such as ciprofloxacin (500 mg twice daily for 5 days) or an oral cephalosporin.23 Because catfish envenomation may mimic necrotizing fasciitis, exploration and debridement of wounds is imperative when the clinical suspicion is high. Tissue cultures may then be obtained for analysis and appropriate IV antibiotics prescribed.11 Prevention remains the best strategy—experienced fishermen use canvas gloves and pliers to remove the fin spines.22 CONCLUSION Commercial freshwater catfish farming is widespread in the United States, so clinicians should be aware of the possibility and spectrum of catfish-related injury, as well as their appropriate management. Catfish have three rigid spines associated with their single dorsal and bilateral pectoral fins that can penetrate skin when the fish is handled. This can result in the local injection of toxins and surface pathogenic bacteria. Untreated wounds may result in deep soft-tissue infections, possibly resulting in bacteremia and infection at distant sites. We report the first known case of thoracic osteomyelitis following catfish fin spine impalement. The initial treatment for catfish fin spine injury is irrigation, followed by immersion in warm water. Tetanus prophylaxis is recommended. Empirical antibiotics such as ciprofloxacin may be used in more serious cases. A neurologically intact patient with thoracic osteomyelitis and a stable spinal column may be treated nonoperatively and successfully with appropriate antibiotics once the pathogen has been cultured either from the blood or from a CT-guided tissue biopsy. JAAPA www.JAAPA.com

REFERENCES 1. Priest DH, Peacock JE Jr. Hematogenous vertebral osteomyelitis due to Staphylococcus aureus in the adult: clinical features and therapeutic outcomes. South Med J. 2005;98(9):854-862. 2. Mete B, Kurt C, Yilmaz MH, et al. Vertebral osteomyelitis: eight years’ experience of 100 cases. Rheumatol Int. 2012;32(11): 3591-3597. 3. Gasbarrini AL, Bertoldi E, Mazzetti M, et al. Clinical features, diagnostic and therapeutic approaches to haematogenous vertebral osteomyelitis. Eur Rev Med Pharmacol Sci. 2005; 9(1):53-66. 4. Sia IG, Berbari EF. Infection and musculoskeletal conditions: osteomyelitis. Best Pract Res Clin Rheumatol. 2006;20(6):10651081. 5. Zimmerli W. Clinical practice. Vertebral osteomyelitis. N Engl J Med. 2010;362(11):1022-1029. 6. Pigrau C, Almirante B, Flores X, et al. Spontaneous pyogenic vertebral osteomyelitis and endocarditis: incidence, risk factors, and outcome. Am J Med. 2005;118(11):1287. 7. Fantoni M, Trecarichi EM, Rossi B, et al. Epidemiological and clinical features of pyogenic spondylodiscitis. Eur Rev Med Pharmacol Sci. 2012;16(suppl 2):2-7. 8. Mayo Clinic Antimicrobial Therapy: Quick Guide. Rochester, MN: Mayo Clinic Scientific Press; 2008:326. 9. Sax H, Lew D. Osteomyelitis. Curr Infect Dis Rep. 1999;1(3): 261-266. 10. US Department of Agriculture. National Agriculture Statistics Service. Catfish production. http://usda.mannlib.cornell.edu/ MannUsda/viewDocumentInfo.do?documentID=1016. Accessed August 21, 2014. 11. Minnesota Department of Natural Resources. Catfish. http:// www.dnr.state.mn.us/fish/catfish/index.html. Accessed August 11, 2014. 12. Carty MJ, Kutz RH, Finley RL Jr, et al. Digital catfish envenomation mimicking necrotizing fasciitis. Plast Reconstr Surg. 2010;126(5):226e-230e. 13. Haddad V Jr. Cutaneous infections and injuries caused by traumatic and venomous animals which occurred in domestic and commercial aquariums in Brazil: a study of 18 cases and an overview of the theme. An Bras Dermatol. 2004;79:157-167. 14. Broderick A, Perlman S, Dietz F. Pseudomonas bursitis: inoculation from a catfish. Pediatr Infect Dis. 1985;4(6):693694. 15. Hargreaves JE, Lucey DR. Life-threatening Edwardsiella tarda soft-tissue infection associated with catfish puncture wound. J Infect Dis. 1990;162(6):1416-1417. 16. Midani S, Rathore MH. Vibrio species infection of a catfish spine puncture wound. Pediatr Infect Dis J. 1994;13(4):333334. 17. Hoffman J. Extremely late presentation of catfish spine injury to the hand. Wilderness Environ Med. 2010;21(4):383. 18. Crosby SN, Snoddy MC, Atkinson CT, et al. Upper extremity myonecrosis caused by Edwardsiella tarda resulting in transhumeral amputation: case report. J Hand Surg Am. 2013;38(1): 129-132. 19. Roth BJ, Geller SM. Deep soft-tissue necrosis of the foot and ankle caused by catfish envenomation: a case report. J Am Podiatr Med Assoc. 2010;100(6):493-496. 20. Ferlic RJ, Bonatz E, Robbin ML. Radial artery injury from a catfish sting. Am J Orthop (Belle Mead NJ). 2003;32(8):412-414. 21. Ashford RU, Sargeant PD, Lum GD. Septic arthritis of the knee caused by Edwardsiella tarda after a catfish puncture wound. Med J Aust. 1998;168(9):443-444. 22. David NF. Letter: still more on catfish stings. JAMA. 1975;233 (8):864. 23. Das SK, Johnson MB, Cohly HH. Catfish stings in Mississippi. South Med J. 1995;88(8):809-812. 24. Haddad V Jr, Martins IA. Frequency and gravity of human envenomations caused by marine catfish (suborder siluroidei): a clinical and epidemiological study. Toxicon. 2006;47(8):838-843. Volume 27 • Number 11 • November 2014

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Thoracic vertebral osteomyelitis following catfish spine impalement.

Although rare, thoracic osteomyelitis can occur when toxins from a catfish spine impalement to the hand spread via the blood. This article describes d...
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