You are in: eMedicine Specialties > Infectious Diseases > MEDICAL TOPICS Mycobacterium XenopiArticle Last Updated: Feb 17, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Sailaja Kolli, MD, Fellow, Department of Internal Medicine, Division of Pulmonary and Critical Care, The Brooklyn Hospital Center Sailaja Kolli is a member of the following medical societies: American Medical Association Coauthor(s): Klaus-Dieter Lessnau, MD, FCCP, Clinical Assistant Professor of Medicine, New York University School of Medicine; Medical Director, Pulmonary Physiology Laboratory, Director of Research in Pulmonary Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital Editors: Wesley W Emmons, MD, FACP, Assistant Professor, Department of Medicine, Thomas Jefferson University; Consulting Staff, Infectious Diseases Section, Department of Internal Medicine, Christiana Care, Newark, DE; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Aaron Glatt, MD, Professor of Clinical Medicine, New York Medical College; Chief Medical Officer, Departments of Medicine and Infectious Diseases, New Island Hospital; Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital; Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital Author and Editor Disclosure Synonyms and related keywords: Mycobacterium xenopi, M xenopi, South African toad, Xenopus laevis, X laevis, nontuberculous mycobacterium, nontuberculous mycobacteria, mycobacteremia, leukocytosis, leucopenia, leukopenia, anemia, reactive thrombocytosis, thrombocytopenia, nontuberculous mycobacterial lung disease, pulmonary disease, cavitary apical pulmonary disease, multifocal bronchiectasis, granulomatous inflammation, acid-fast bacilli INTRODUCTIONSection 2 of 10
  BackgroundResearchers first described Mycobacterium xenopi in 1959 after isolating it from skin lesions of the South African toad Xenopus laevis. M xenopi, a slow-growing, nontuberculous mycobacterium, is often considered to be a saprophyte or an environmental contaminant. It grows optimally at 45°C (113°F) and has been found, occasionally in large numbers, in hospital hot water supplies at the outlet valves of water heaters. M xenopi colonization occurs from ingestion or inhalation of, or cutaneous exposure to, organisms in water, soil, or airborne particles. Colonization of hospital water systems is associated with infection, disease, and nosocomial isolation. PathophysiologyM xenopi has low pathogenicity, and host impairment is required to contract disease from the organism. Most M xenopi infections occur in the lungs, usually in patients with preexisting lung disease or with predisposing conditions (eg, extrapulmonary malignancy, alcoholism, diabetes mellitus, HIV infection). Extrapulmonary and disseminated disease may develop in patients with AIDS or other immunodeficiencies. For pulmonary disease, inhalation of infected airborne particles is the usual route of infection. For skin and soft tissue infections, direct contact through penetrating injuries and surgical procedures provide the route. Person-to-person transmission of nontuberculous mycobacterial disease has never been documented. FrequencyUnited StatesSurveillance data for M xenopi infection are not available because such infection is not a reportable disease. More than 500 cases have been reported, but only approximately 70 cases seem to document true disease. InternationalPrevalence is unknown. Mortality/MorbiditySubjects with documented M xenopi infections are divided into the following broad categories:
RaceNo racial predilection has been identified. SexNo predilection for either sex has been demonstrated. AgeNo age predilection has been reported. CLINICALSection 3 of 10
HistoryInfection with M xenopi may result in pulmonary infection, usually in older adults with COPD, in patients who are immunocompromised with disseminated disease, or in patients with extrapulmonary disease involving the lymphatic system, skin, bones, or joints. Onset of symptoms is insidious, and the infection may progress slowly or increase and decrease over the course of months or years.
PhysicalPhysical findings relate to underlying long-term illness and are not specific for M xenopi infection. More than 95% of patients have abnormal lung findings. Causes
DIFFERENTIALSSection 4 of 10
Bronchiectasis Bronchitis Mycobacterium Avium-Intracellulare Mycobacterium Chelonae Mycobacterium Fortuitum Mycobacterium Gordonae Mycobacterium Haemophilum Mycobacterium Kansasii Mycobacterium Marinum Tuberculosis
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| Drug Name | Clarithromycin (Biaxin) |
|---|---|
| Description | Probably most important drug. To avoid development of resistance, should not be used as monotherapy. Inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. |
| Adult Dose | 500 mg PO bid |
| Pediatric Dose | 15 mg/kg PO divided bid |
| Contraindications | Documented hypersensitivity; coadministration of pimozide |
| Interactions | Toxicity increases with coadministration of fluconazole, astemizole, and pimozide; effects decrease and adverse GI effects may increase with coadministration of rifabutin or rifampin; may increase toxicity of anticoagulants, cyclosporine, tacrolimus, digoxin, omeprazole, carbamazepine, ergot alkaloids, triazolam, and HMG CoA-reductase inhibitors; serious cardiac arrhythmias may occur with coadministration of cisapride; plasma levels of certain benzodiazepines may increase, prolonging CNS depression; arrhythmias and increased QTc intervals occur with disopyramide; coadministration with omeprazole may increase plasma levels of both agents |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Coadministration with ranitidine or bismuth citrate is not recommended with CrCl <25 mL/min; administer half dose or increase dosing interval if CrCl <30 mL/min; diarrhea may be sign of pseudomembranous colitis; superinfections may occur with prolonged or repeated antibiotic therapies |
| Drug Name | Ethambutol (Myambutol) |
|---|---|
| Description | Probably second most important drug. Diffuses into actively growing mycobacterial cells (eg, tubercle bacilli). Impairs cell metabolism by inhibiting synthesis of one or more metabolites, which in turn causes cell death. No cross-resistance demonstrated. Mycobacterial resistance is frequent with previous therapy. Use in these patients in combination with second-line drugs that have not been administered previously. Administer q24h until permanent bacteriologic conversion and maximal clinical improvement is observed. Absorption is not altered significantly by food. |
| Adult Dose | No previous antituberculous therapy: 15 mg/kg/d (7 mg/lb/d) PO; previous antituberculous therapy: 25 mg/kg/d (11 mg/lb/d) |
| Pediatric Dose | <12 years: Not recommended >12 years: Administer as in adults |
| Contraindications | Documented hypersensitivity; optic neuritis (unless clinically indicated) |
| Interactions | Aluminum salts may delay and reduce absorption (administer several h before or after ethambutol dose) |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Reduce dose in impaired renal function; optic neuritis/color blindness with doses >15 mg/kg/d; obtain ophthalmology consult if 25 mg/kg/d dose used |
| Drug Name | Rifabutin (Mycobutin) |
|---|---|
| Description | Ansamycin antibiotic derived from rifamycin S. Inhibits DNA-dependent RNA polymerase, preventing chain initiation in susceptible strains of Escherichia coli and Bacillus subtilis but not in mammalian cells. If GI upset, administer dose bid with food. |
| Adult Dose | 300 mg PO qd is regular dose; maximum 600 mg/d PO; alternatively, 10-20 mg/kg/d; not to exceed 600 mg/d; if GI upset, administer dose bid with food |
| Pediatric Dose | Not established; suggested dose, 5 mg/kg/d PO |
| Contraindications | Documented hypersensitivity |
| Interactions | Steady-state zidovudine plasma levels may decrease after repeated rifabutin dosing but do not affect inhibition of HIV by zidovudine |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Do not administer to patients with active tuberculosis; no evidence of effectiveness in preventing Mycobacterium tuberculosis infection; may administer isoniazid concurrently in patients requiring prophylaxis against both M tuberculosis and Mycobacterium avium complex; perform hematologic studies periodically in patients receiving prophylaxis because of association with neutropenia and, more rarely, thrombocytopenia |
| Drug Name | Streptomycin |
|---|---|
| Description | For treatment of susceptible mycobacterial infections. Use in combination with other antituberculous drugs (eg, isoniazid, ethambutol, rifampin). Total period of treatment for tuberculosis is minimum of 1 y; however, indications for terminating therapy may occur at any time. Recommended when less potentially hazardous therapeutic agents are ineffective or contraindicated. |
| Adult Dose | 1 g IM qd 2 times/wk dosing: 15 mg/kg/d IM; not to exceed 1 g/d 3 times/wk dosing: 25-30 mg/kg/d IM; not to exceed 1.5 g/d |
| Pediatric Dose | 2 times/wk dosing: 20-40 mg/kg/d IM; not to exceed 1 g/d 3 times/wk dosing: 25-30 mg/kg/d IM; not to exceed 1.5 g/d |
| Contraindications | Documented hypersensitivity; non–dialysis-dependent renal insufficiency |
| Interactions | Increased toxicity with loop diuretics (eg, furosemide) and amphotericin B; increased prolonged effect depolarizing and nondepolarizing neuromuscular blocking agents |
| Pregnancy | D - Unsafe in pregnancy |
| Precautions | Monthly audiogram; narrow therapeutic index; not intended for long-term therapy; caution in patients with renal failure who are not on dialysis; caution with myasthenia gravis, hypocalcemia, and conditions that depress neuromuscular transmission |
| Drug Name | Rifampin (Rifadin) |
|---|---|
| Description | Probably an important drug for treatment. For use in combination with at least 1 other antituberculous drug. Inhibits DNA-dependent bacteria but not mammalian RNA polymerase. Cross-resistance may occur. |
| Adult Dose | 10 mg/kg/d PO/IV; divided doses if patient is intolerant; not to exceed 600 mg/d; treat for 6-9 mo or until 6 mo elapse from conversion to negative sputum culture results |
| Pediatric Dose | 10-20 mg/kg PO/IV; not to exceed 600 mg/d |
| Contraindications | Documented hypersensitivity |
| Interactions | Induces microsomal enzymes, which may decrease effects of acetaminophen, oral anticoagulants, barbiturates, benzodiazepines, beta-blockers, chloramphenicol, oral contraceptives, corticosteroids, mexiletine, cyclosporine, digitoxin, disopyramide, estrogens, hydantoins, methadone, clofibrate, quinidine, dapsone, tazobactam, sulfonylureas, theophyllines, tocainide, and digoxin; blood pressure may increase with coadministration of enalapril; coadministration with isoniazid may result in higher rate of hepatotoxicity than with either agent alone (discontinue one or both agents if alterations in LFT findings occur) |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Colors urine, sweat, tears, and contact lenses orange-brown; order pretreatment LFT (repeat if symptomatic); obtain CBC counts and baseline clinical chemistries prior to and throughout therapy; in liver disease, weigh benefits against risk of further liver damage; interruption of therapy and high-dose intermittent therapy are associated with thrombocytopenia that is reversible if therapy is discontinued |
| Drug Name | Azithromycin (Zithromax) |
|---|---|
| Description | Similar to clarithromycin but may allow once-per-wk dosing. |
| Adult Dose | 250-500 mg/d PO for 5-14 d 1200 mg/d PO once-per-wk dosage has been used |
| Pediatric Dose | <6 months: Not established >6 months: 10 mg/kg PO on day 1, not to exceed 500 mg/d; 5 mg/kg/d PO on days 2-5, not to exceed 250 mg/d |
| Contraindications | Documented hypersensitivity; hepatic impairment; do not administer with pimozide |
| Interactions | May increase toxicity of theophylline, warfarin, and digoxin; effects are reduced with coadministration of aluminum and/or magnesium antacids; nephrotoxicity and neurotoxicity may occur when coadministered with cyclosporine |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Site reactions can occur with IV route; bacterial or fungal overgrowth may result with prolonged antibiotic use; may increase hepatic enzymes and cholestatic jaundice; caution in patients with impaired hepatic function or prolonged QT intervals; caution in patients who are hospitalized, elderly, or debilitated |
| Drug Name | Levofloxacin (Levaquin) |
|---|---|
| Description | For treatment of tuberculosis in combination with rifampin and other antituberculosis agents. |
| Adult Dose | 500-1000 mg/d PO |
| Pediatric Dose | <18 years: Not recommended >18 years: Administer as in adults |
| Contraindications | Documented hypersensitivity; pregnancy; lactation |
| Interactions | Antacids, iron salts, and zinc salts may reduce serum levels; administer antacids 1-2 h ac or pc |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Adjust dose in renal function impairment |
Article Last Updated: Feb 17, 2006
