Exotic pet ownership is common, and human interaction with these animals puts owners at risk for infections with unusual organisms. Human infections with atypical organisms are more common in immunocompromised patients. In this article, we describe a woman with chronic kidney disease and a nonhealing papule after a cockatoo bite to the hand.
A 68-year-old woman who owns 3 birds-an African gray parrot, a conure, and a cockatoo-came to our clinic in October 2005, approximately 30 days after being bitten by the cockatoo on her right hand between the second and third digits. She reported cleaning the bite immediately with hydrogen peroxide and applying bacitracin daily. Despite local care, swelling of the hand and an erythematous nodule developed over the ensuing 14 days. The patient went to an emergency department and was prescribed oral levofloxacin, 500 mg daily; oral trimethoprim/sulfamethoxazole, 160/800 mg twice daily; and 2% mupirocin ointment 3 times daily. The swelling resolved with 14 days of antibiotic therapy, but the nodule persisted. She denied any constitutional symptoms.
The patient's medical history was contributory for hypertension, stage 3 chronic kidney disease with a baseline creatinine level of 1.8 mg/dL (reference range, 0.7-1.2 mg/dL) and a glomerular filtration rate of 30 mL/min (reference range, 87-141 mL/min), and hyperglycemia. She was a former cigarette smoker and rarely drank alcohol. She has a dog and is actively involved in the care of her pets. She received a tattoo in the past but had no other risk factors for human immunodeficiency virus and no history of immunosuppression. Her current medications are antihypertensives and paroxetine. She has no known drug allergies.
On examination, the patient was afebrile. A 5 × 2.5-cm violaceous nodule was seen on the right hand between the second and third digits. There was no erythema, edema, or palpable increased warmth, and no epitrochlear or axillary lymph nodes were palpable.
The lesion was incised and produced a yellow-white material. Treatment was withheld until culture and sensitivity reports were available. Figure 1 shows the residual lesion.
The bacterial culture had near-confluent growth on the plate of Mycobacterium chelonae/abscessus sensitive to clarithromycin, amikacin, and tigecycline and resistant to doxycycline, sulfamethoxazole, vancomycin, ciprofloxacin, moxifloxacin, levofloxacin, and gatifloxacin. The organism was intermediately sensitive to linezolid and cefoxitin. Magnetic resonance imaging revealed no evidence of osteomyelitis or tenosynovitis beneath the lesion.
The lesion was surgically excised. Operative cultures were negative for bacteria and fungi. The acid-fast bacilli smear was negative, but cultures again yielded M. chelonae/abscessus. A perioperative blood culture for acid-fast bacilli was also negative. At that time, clarithromycin, 500 mg twice daily, was initiated.
Within the week after the surgical excision, the patient noted the development of additional nodules on her forearm but did not report this until her follow-up appointment 1 month later. Examination revealed several small maculopapular lesions without erythema, swelling, or exudates. This occurrence was thought to be too soon to be considered a clarithromycin treatment failure, and treatment with clarithromycin was continued. Two of the 7 arm lesions resolved after 3 months of antibiotic therapy. The remaining lesions were then surgically removed to obtain specimens for cultures, the results of which were negative. After consulting the literature regarding this organism,1,2 clarithromycin therapy was continued for 12 months with only minor adverse effects and no complications, and the patient remains asymptomatic to date.
Members of the genus Mycobacterium can be divided into 2 groups on the basis of their growth rates on agar plates.3 The slow-growing organisms (taking several weeks of incubation) include the tuberculous species (eg, Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium africanum, and Mycobacterium microti) and some nontuberculous species such as Mycobacterium avium complex. The rapidly growing group (growth in days rather than weeks) includes Mycobacterium chelonae/abscessus, Mycobacterium fortuitum, Mycobacterium smegmatis, Mycobacterium phlei, and Mycobacterium vaccae. Of these, M.chelonae/abscessus and M. fortuitum account for the majority of clinically important infections.
Mycobacterium chelonae/abscessus is a ubiquitous environmental organism, found in water, soil, milk and fruit products, and domestic and wild animals. Human infections are relatively uncommon, but an increase in the number of reported cases has been identified among immunocompromised persons.4 Mycobacterium chelonae/abscessus skin infections are commonly associated with penetrating injury or surgery.2,5,6 The skin lesions can present as cellulitis, abscesses, nodules, sinus tracts, and ulcers with serosanguineous or purulent discharge.6,7 Regional lymphadenitis is often present.8,9
Lymphocutaneous and hematogenous spread of M. chelonae/abscessus can occur. Lymphocutaneous spread ("sporotrichoid disease") usually occurs in immunocompetent patients, and hematogenous dissemination more commonly occurs in patients with immunocompromising conditions.3,10 Other possible areas of infection include lung, heart, bone, joint, eye, and central nervous system.9
Diagnosis rests on isolation of M. chelonae/abscessus from culture specimens on appropriate media, with appropriate temperature control. Mycobacterium chelonae/abscessus grows optimally at 28°C to 30°C, in contrast to the standard incubating temperature of 35°C for most mycobacterial organisms.8 Because of this difference in optimal temperature growth, the microbiology laboratory should be notified of suspected M. chelonae/abscessus infections, so that optimal conditions for incubation can be assured. The diagnosis requires a high index of suspicion and should be considered in any patient with a long-term, nonhealing wound that is unresponsive to usual antibiotics.
Therapeutic modalities include surgical excision, localized heating, and antimicrobial therapy. Surgical excision and localized heating may not be easily performed if lesions are numerous.11,12 Drug therapy can be difficult because of frequent antibiotic resistance to the usual antituberculous drugs. Mycobacterium chelonae/abscessus isolates are usually susceptible in vitro to clarithromycin but are generally resistant to ciprofloxacin. Susceptibility testing should guide therapy and should include traditional agents as well as newer agents such as tigecycline, linezolid, moxifloxacin, and gatifloxacin. Although the use of at least 2 active drugs is recommended because of the possibility of the emergence of resistance associated with monotherapy,9,10,13 several cases have been reported demonstrating successful treatment of disseminated cutaneous M. chelonae/abscessus infections with clarithromycin alone.1,8
Regarding risk for disease, the patient did not appear to be overtly immunocompromised, although she does have long-term kidney disease. Because M. chelonae/abscessus is an environmental bacterium, the source is impossible to determine; it is clear, however, that the cockatoo bite was the penetrating injury that served as the portal of inoculation. There have been reports of such infections transmitted by other unusual penetrating trauma such as bee stings,14 but to our knowledge, this is the first reported case of M. chelonae/abscessus resulting from a bird bite. Because of the ubiquitous nature of this and other environmental mycobacterial organisms, medical professionals must consider the possibility of atypical infections such as these in patients presenting with chronic nodular lesions that are unresponsive to the usual antibiotics.9
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