Infections caused by Mycobacterium szulgai in humans

Lungenerkrankung durch seltenere nicht-tuberkulöse Mykobakterien – Neue internationale Empfehlungen

Therapie von NTM-Infektionen Für die Behandlung von NTM-Infektionen der Lungen stehen erstmals Evidenz-basierte internationale Leitlinien zur Verfügung. Nach der ersten Publikation der neuen ATS/ERS/ESCMID- und IDSA-Leitlinien zur Behandlung von Lungenerkrankungen durch M. avium complex, M. kansasii, M. xenopi und M. abscessus von 2020 liegen nun weitere Empfehlungen zur Behandlung von selteneren Lungenerkrankungen durch NTM vor.

Relevante NTM-Spezies Die neuen Empfehlungen umfassen Lungenerkrankungen durch die schnellwachsenden Mykobakterien M. chelonae und M. fortuitum sowie durch die langsam-wachsenden Mykobakterien M. genavense, M. gordonae, M. malmoense, M. simiae und M. szulgai.

Disseminated Mycobacterium szulgai infection in a patient with anti-interferon-gamma autoantibodies

Incidence of nontuberculous mycobacterial infections has increased during the past decades. Disseminated infections are relatively rare and associated with immunocompromised status. We report a case of disseminated Mycobacterium szulgai infection of cervical lymphadenitis and pulmonary involvement with positive anti-interferon-gamma autoantibodies. The patient was successfully treated with rifampin, ethambutol, and clarithromycin. The case reports and series through search engines of Pubmed and Google with the keyword of disseminated infection of M. szulgai were reviewed. Fifteen patients of disseminated M. szulgai infection were reviewed and included. DisseminatedM. szulgaiinfection involves bone, skin and lymph node more common instead of pulmonary involvement, and most are associated with immunocompromised status with neoplastic hematologic disorders. In patients with disseminated M. szulgai infection, long term anti-mycobacterial agents are necessary. Most patients will respond to rifampin and ethambutol combination regimens.

Mycobacterium szulgai Infection after Carpal Tunnel Release Requiring Extensive Debridement and ALT Flap Reconstruction

Nontuberculous mycobacteria (NTM) refer to all mycobacteria species not associated with the Mycobacterium tuberculosis complex. NTM have been shown to cause superficial and deep tissue infections of the hand, the vast majority of which are attributed to Mycobacterium marinum . There have been only eight cases of Mycobacterium szulgai -associated infections of the hand described in the English literature, none requiring surgical reconstruction. We describe a severe case of M. szulgai -associated carpal tunnel infection reported in an immunocompetent patient requiring extensive soft tissue debridement and reconstruction. This case illustrates the importance of a multidisciplinary team approach with microbiology specialists when managing severe soft tissue infections of the hand.

Other Slow-Growing Nontuberculous Mycobacteria

The list of clinically important slow-growing nontuberculous mycobacteria (NTM) continues to expand as new species are identified and older ones are found to be pathogenic. Based on pigment production, the strains may be classified as photochromogenic, scotochromogenic, or unpigmented. Some of these organisms are not newly discovered but have heretofore been considered virtually nonpathogenic. Previously, many were regarded as contaminants when isolated from clinical specimens. Ubiquitous in nature, many NTM have been isolated from groundwater or tap water, soil, house dust, domestic and wild animals, and birds. Most infections result from inhalation or direct inoculation from environmental sources. They are not spread from person to person. The infections may be localized or disseminated. In most cases, the optimal regimen or duration of therapy has not been firmly established. The results of in vitro susceptibility testing may be used to select a therapeutic regimen. Many experts recommend clarithromycin with companion drugs such as rifampin and ethambutol for most, but not all, slowly growing species. Aminoglycosides, clofazimine, fluoroquinolones, linezolid, pyrazinamide, or trimethoprim-sulfamethoxazole also may be effective against some strains. Immunocompetent patients with clinically significant infections with NTM usually should receive 18 to 24 months of therapy. Infected immunocompromised patients, particularly those with disseminated infection, probably should receive therapy as long as their immune systems remain impaired. Some of the species discussed include Mycobacterium alsiense, M. celatum, M. gordonae, M. haemophilum, M. kyorinense, M. malmoense, M. simiae complex, M. szulgai, M. terrae complex, M. ulcerans, and M. xenopi.

Mycobacterium avium complex olecranon bursitis resolves without antimicrobials or surgical intervention: A case report and review of the literature

Introduction

Nontuberculous mycobacteria are an uncommon cause of septic olecranon bursitis, though cases have increasingly been described in both immunocompromised and immunocompetent hosts. Guidelines recommend a combination of surgical resection and antimicrobials for treatment. This case is the first reported case of nontuberculous mycobacterial olecranon bursitis that resolved without medical or surgical intervention.

Case presentation

A 67-year-old female developed a painless, fluctuant swelling of the olecranon bursa following blunt trauma to the elbow. Due to persistent bursal swelling, she underwent three separate therapeutic bursal aspirations, two involving intrabursal steroid injection. After the third aspiration, the bursa became erythematous and severely swollen, and bursal fluid grew Mycobacterium avium complex. Triple-drug antimycobacterial therapy was initiated, but discontinued abruptly due to a rash. Surgery was not performed. The patient was observed off antimicrobials, and gradually clinically improved with a compressive dressing. By 14 months after initial presentation, clinical exam revealed complete resolution of the previously erythematous bursal mass.

Discussion

This is the first reported case of nontuberculous mycobacterial olecranon bursitis managed successfully without surgery or antimicrobials. Musculoskeletal nontuberculous mycobacterial infections are challenging given the lack of clinical data about optimal duration and choice of antimicrobials or the role of surgery. Additionally, the potential toxicity and drug interactions of antimycobacterials are not insignificant and warrant close monitoring if treatment is pursued.

Conclusion

This case raises an important clinical question of whether close observation off antimicrobials is appropriate in select cases of immunocompetent patients with localized atypical mycobacterial disease of soft tissue and skeletal structures.

Mycobacterial infections in reptiles

Mycobacteriosis is an important disease worldwide. Although commonly associated with higher vertebrates, including humans, it has been reported in only a handful of reptile cases. The purpose of this article is to review the literature as it relates to mycobacteriosis in reptiles. Knowledge of the epidemiology of this disease can be useful to veterinarians working with these animals, especially when working on a diagnosis and making recommendations to clients regarding the need for case follow-up to rule in or rule out the potential presence of these pathogens in pet reptiles and best handling practices to minimize their exposure.

Nine-year progression of untreated pulmonary Mycobacterium szulgai infection

A 58-year-old man was seen with complaints of fevers, night sweats, weight loss, and multiple bilateral cavitary lung lesions. Mycobacterium szulgai with nearly identical antibiograms grew from separate sputum specimens 9 years apart. He was treated with a combination of clarithromycin and ethambutol with clinical, microbiologic, and radiographic resolution of disease. This is the longest untreated case of documented Mycobacterium szulgai infection reported, and offers a glimpse of its natural history when left untreated. Despite an infrequent isolation (<0.5% of cases), it is a pathogenic organism which warrants treatment.

Clinical significance of Mycobacterium asiaticum isolates in Queensland, Australia

Mycobacterium asiaticum was first reported as a cause of human disease in 1982, with only a few cases in the literature to date. This study aims to review the clinical significance of M. asiaticum isolates in Queensland, Australia. A retrospective review (1989 to 2008) of patients with M. asiaticum isolates was conducted. Data were collected through the Queensland TB Control Centre database. Disease was defined in accordance with the American Thoracic Society criteria. Twenty-four patients (13 female) had a positive culture of M. asiaticum, many residing around the Tropic of Capricorn. M. asiaticum was responsible for pulmonary disease (n = 2), childhood lymphadenitis (n = 1), olecranon bursitis (n = 1), 6 cases of possible pulmonary disease, and 2 possible wound infections. Chronic lung disease was a risk factor for pulmonary infection, and wounds/lacerations were a risk factor for extrapulmonary disease. Extrapulmonary disease responded to local measures. Pulmonary disease responded to ethambutol-isoniazid-rifampin plus pyrazinamide for the first 2 months in one patient, and amikacin-azithromycin-minocycline in another patient. While M. asiaticum is rare in Queensland, there appears to be an environmental niche. Although often a colonizer, it can be a cause of pulmonary and extrapulmonary disease. Treatment of pulmonary disease remains challenging. Extrapulmonary disease does not mandate specific nontuberculous mycobacterium (NTM) treatment.

Olecranon bursitis secondary to Mycobacterium kansasii infection in a patient receiving infliximab for Behçet's disease

We present a case of Mycobacterium kansasii olecranon bursitis in a woman with known immunosuppression secondary to the treatment received for her Behçet's disease. We found only one other case report of olecranon bursitis caused by M. kansasii in the literature, which, unlike our case, presented in an immunocompetent adult following trauma. This case extends the range of opportunistic mycobacterial infections that are associated with anti-tumour necrosis factor therapy.

Multifocal osteomyelitis due to Mycobacterium szulgai in a patient with chronic lymphocytic leukemia

Mycobacterium szulgai is a pathogenic organism that most frequently causes pulmonary infection and may rarely result in disseminated disease in immunocompromised individuals. We report a case of multifocal osteomyelitis and cutaneous lesions due to M. szulgai in a patient with chronic lymphocytic leukemia. The successful treatment of multifocal osteomyelitis was accomplished using isoniazid, rifampin, and ethambutol.

First pulmonary case reported in Argentina of infection with mycobacterium szulgai, a rare pathogen

Mycobacterium szulgai is a rare pathogen. Nontuberculous mycobacteria usually produce disease in people with some kind of immunosuppression or another predisposing condition. A case of pulmonary Mycobacterium szulgai infection is described.

Mycobacterium kansasii olecranon bursitis

A case is reported of a post-traumatic olecranon bursitis caused by Mycobacterium kansasii following an injury sustained in a public swimming pool. It responded to surgical debridement and combined rifampicin, isoniazid, pyrazinamide and ethambutol antimicrobial therapy. A literature search was performed and a treatment regimen for this uncommon condition is suggested.

Mycobacterium szulgaiin a Patient with Advanced Acquired Immunodeficiency Syndrome: An Unusual Pathogen with Unusual Multidrug Resistance

A 37-year-old Hispanic man with advanced acquired immunodeficiency syndrome developed extensive pulmonary disease with persistent cough, fever, night sweats, worsening dyspnea, and weight loss. Sputum samples showed scant growth of acid-fast bacilli. He failed to respond to the standard tuberculosis regimen of isoniazid, rifampin, ethambutol, and pyrazinamide. Subsequently, Mycobacterium szulgai was identified, and susceptibility tests showed it to be resistant to all four of those agents. Therapy was changed to clarithromycin, doxycycline, ciprofloxacin, and amikacin. Within 2 weeks, the patient's condition improved significantly, and 6 months after treatment, extensive pulmonary infiltrates had nearly resolved. Fewer than 1% of all human isolates of mycobacteria consist of M. szulgai, which is relatively susceptible to standard antimycobacterial agents. To our knowledge, this is the first reported case of M. szulgai with resistance to all primary antituberculosis drugs.

Pulmonary nontuberculous mycobacterial infection caused by Mycobacterium szulgai in a young healthy woman

A 20-year-old woman with no history of pulmonary disease had no symptom and her chest CT scans demonstrated adhesive small multiple nodules in the bronchial lung biopsy specimen showed epithelioid cell granuloma containing Langhans giant cells, therefore she was diagnosed as pulmonary mycobacteriosis caused by M. szulgai. This is the youngest case of this rare condition occurring in a healthy subject without underlying pulmonary diseases.

Delayed-onset mycobacterial keratitis after LASIK

PURPOSE

To describe the time course, diagnosis, clinical features, and treatment of seven patients with Mycobacterium szulgai keratitis that developed from 7 to 24 weeks after laser in situ keratomileusis (LASIK).

METHODS

Seven of 30 eyes of 18 patients were identified with keratitis after LASIK. The first two patients presented 12 to 14 weeks after LASIK; nontuberculous mycobacteria were identified 1 month after the flaps were cultured. Patient recall identified three additional cases by culture and two cases by clinical features alone. Pulsed-field gel electrophoresis (PFGE) was used to type the isolates, and treatment was modified based on susceptibilities.

RESULTS

M. szulgai was identified in five patients for whom cultures were performed, but response to empiric therapy based on cultures proved unsatisfactory. The keratitis resolved in all patients with treatment including clarithromycin based on susceptibilities. Medical therapy was sufficient, although one patient required flap amputation. Six of seven patients recovered best-corrected visual acuity (BCVA), while one patient lost one line of BCVA. Two patients lost one line of postoperative uncorrected visual acuity (UCVA), two patients gained one line of UCVA, and three patients recovered postoperative UCVA. PFGE analysis revealed that the M. szulgai strains were identical, and the infection source was contaminated ice used to chill syringes for saline lavage.

CONCLUSIONS

Nontuberculous mycobacterial keratitis after LASIK is a diagnostic and management challenge, but outcomes can be preserved with treatment based on susceptibilities. This cluster underscores the importance of adherence to sterile protocol during LASIK.

A Cluster of cases of Mycobacterium szulgai keratitis that occurred after laser-assisted in situ keratomileusis

Laser-assisted in situ keratomileusis (LASIK) is a recently developed ophthalmic procedure. When 2 patients developed keratitis caused by Mycobacterium szulgai after they underwent LASIK surgery, we conducted a retrospective cohort study of all LASIK procedures performed at Scott & White Clinic (Temple, Texas) during a 4.5-month period. Seven patients had compatible symptoms and signs, 5 of whom had confirmed M. szulgai keratitis. Five cases occurred among 30 procedures performed by doctor A, and there were no cases among 62 procedures performed by doctor B (approximate relative risk, 12.0; 95% confidence interval, 1.6-679.0; P=.0029). Doctor A had chilled syringes of saline solution in ice for intraoperative lavage-the only factor that differentiated the procedures of the 2 surgeons. Cultures of samples from the source ice machine's drain identified M. szulgai; the strain was identical to isolates recovered from all confirmed cases and differed from 4 standard M. szulgai strains, as determined by pulsed-field gel electrophoresis. Intraoperative contamination from ice water apparently led to M. szulgai keratitis in these patients.

Pseudoepidemic due to a unique strain of Mycobacterium szulgai: genotypic, phenotypic, and epidemiological analysis

In mid-1999, we noted multiple isolations at the Veterans Affairs Medical Center (VAMC) Houston Tex. of an unusual nonpigmented Mycobacterium species. Since, on the basis of 16S rRNA gene sequence analysis, the strains were identical to the Mycobacterium szulgai type strain and since M. szulgai has been reported only rarely as a commensal or environmental isolate, we were concerned about laboratory contamination, nosocomial spread, or even the possibility that this could be a novel organism associated with disease. Our investigation found that from 1999 to 2000, 37 strains of M. szulgai were isolated from patients at the VAMC (the base rate for the previous 10 years had been <1 isolation per year). We compared the phenotypic properties and genetic relatedness of these 37 strains (31 of which were nonpigmented) as well as eight stock strains and the M. szulgai type strain. All strains were similar in cellular fatty acid patterns, growth rates, and biochemical characteristics. However, we found three genogroups by gene sequence analysis. Genogroup I comprised the M. szulgai type strain, all the tested nonpigmented strains (27 of the 31 strains were tested), two pigmented strains isolated in 1999 and 2000, and five pigmented stock strains. Genogroup II comprised five pigmented strains: three were isolated from 1999 to 2000 and two were stock strains. The single strain (isolated in 1996) in genogroup III was pigmented and was the only strain associated with disease. Whereas the randomly amplified polymorphic DNA (RAPD) patterns of all nonpigmented strains were identical, indicating that they came from a common source (the pseudoepidemic strain), the RAPD patterns of the other strains were varied. In our investigation for a possible source, we found that there were no common reagents, specimen-processing or patient locations, or procedures linking the 31 pseudoepidemic strains. However, a nonpigmented M. szulgai strain with a gene sequence and RAPD pattern identical to those of the pseudoepidemic strain was recovered from a water storage tank serving the hospital. We concluded that the strains most likely originated from hospital water, which transiently inoculated our patients. Although no disease was associated with this cluster of isolates, the event was costly because identification was problematic and we could not easily discount the isolations, since most of the patients were immunocompromised and were candidates for opportunistic infection.

Mycobacterium marinum with associated bursitis

BACKGROUND

Mycobacterium marinum infections have been reported for over 50 years, mostly in association with trauma in the setting of water exposure.

OBJECTIVE

The differential diagnosis for nodules in a sporotrichoid distribution with simultaneous bursitis is discussed. Mycobacterium marinum treatment regimens for skin and joint involvement are reviewed.

METHODS

Mycobacterium marinum was identified by skin tissue culture with Lowenstein-Jensen medium at 32 degrees C. Histopathologic findings support mycobacterial infection.

RESULTS

Bursitis and nodules resolved in the first 2 months of a 6-month course of minocycline treatment.

CONCLUSION

Bursitis is an extremely rare but significant complication of M. marinum.

Mycobacterium szulgai osteomyelitis

Mycobacterium szulgai is a rare cause of human infections, and when present it is mostly known to cause lung infection. We report the first case of isolated Mycobacterium szulgai osteomyelitis in a 68-year-old woman on chronic immunosuppressive therapy. Review of the literature revealed a total of three other cases of M. szulgai osteomyelitis. In all these cases there was evidence of hematogenous or contiguous spread, including one with extensive dissemination. Pulmonary M. szulgai infections tend to occur in patients with chronic lung disease and/or concomitant lung infections, whereas osteomyelitis tends to occur in patients who have severe immunosuppression secondary to disease or drugs.

Diagnosis and treatment of disease caused by nontuberculous mycobacteria. This official statement of the American Thoracic Society was approved by the Board of Directors, March 1997. Medical Section of the American Lung Association

Diagnostic criteria of nontuberculous mycobacterial lung disease in HIV-seropositive and -seronegative hosts. The following criteria apply to symptomatic patients with infiltrate, nodular or cavitary disease, or a high resolution computed tomography scan that shows multifocal bronchiectasis and/or multiple small nodules. A. If three sputum/bronchial wash results are available from the previous 12 mo: 1. three positive cultures with negative AFB smear results or 2. two positive cultures and one positive AFB smear B. If only one bronchial wash is available: 1. positive culture with a 2+, 3+, or 4+ AFB smear or 2+, 3+, or 4+ growth on solid media C. If sputum/bronchial wash evaluations are nondiagnostic or another disease cannot be excluded: 1. transbronchial or lung biopsy yielding a NTM or 2. biopsy showing mycobacterial histopathologic features (granulomatous inflammation and/or AFB) and one or more sputums or bronchial washings are positive for an NTM even in low numbers.

COMMENTS

these criteria fit best with M. avium complex, M. abscessus, and M. kansasii. Too little is known of other NTM to be certain how applicable these criteria will be. At least three respiratory samples should be evaluated from each patient. Other reasonable causes for the disease should be excluded. Expert consultation should be sought when diagnostic difficulties are encountered.

Mycobacterium szulgai infection of the lung: case report and review of an unusual pathogen

The nontuberculous mycobacteria are responsible for considerable morbidity in the immunocompromised and immunocompetent host, especially in the older patient with chronic fibrotic or cavitary disease of the lung. Mycobacterium szulgai is a slow growing mycobacterium infrequent in nature and man. Except from a snail and a tropical fish, it has been isolated only from humans and nearly always represents a true pathogen. Three-drug therapy using in vitro susceptibilities as a guide for 12 to 18 months increases the likelihood of success. We present a patient who developed M szulgai pulmonary infection 30 years after an episode of pulmonary tuberculosis. After successful therapy for his M szulgai infection, this patient developed chronic pulmonary histoplasmosis. We review the 25 years of clinical experience with this mycobacteria; particular emphasis is on the presentation and treatment of this very unusual infection.

Nontuberculous mycobacterial infections

OBJECTIVE

To review the epidemiology, clinical manifestations, diagnosis, and treatment of nontuberculous mycobacterial infections other than Mycobacterium avium complex (MAC).

DATA SOURCES

A MEDLINE search of English-language literature pertaining to nontuberculous mycobacteria other than MAC was performed. Additional literature was obtained from reference lists of pertinent articles identified through the search.

STUDY SELECTION AND DATA EXTRACTION

All articles were considered for possible inclusion in the review. Information judged by the author to be pertinent was selected for discussion.

DATA SYNTHESIS

Mycobacterial infections, including those caused by nontuberculous mycobacteria other than MAC, have assumed greater importance over the past decade, due in part to the changing spectrum of immunosuppression as manifested by organ transplantation and HIV infection. Many pathogenic nontuberculous mycobacteria have been identified that are associated with a wide variety of localized, organ-specific, and systemic infections. Of concern, these organisms exhibit variable, species-specific susceptibility to traditional antimycobacterial drugs and other antimicrobials. In addition, long treatment courses and adjunctive surgical therapy are often required to effect cure. Important antimicrobials for the management of these infections include cefoxitin, imipenem/cilastatin, aminoglycosides (other than streptomycin), tetracyclines, macrolides, and trimethoprim/sulfamethoxazole, as well as traditional antimycobacterials.

CONCLUSIONS

Nontuberculous mycobacteria have assumed an increasing role in disease etiology in both nonimmunocompromised and immunocompromised individuals. Advent of rapid diagnostic techniques and susceptibility testing has allowed the clinician to identify these organisms and initiate effective treatment on a more timely basis with an improved chance for cure. Few therapeutic agents are available for treatment of these infections, many of which are not considered classic antimycobacterials.

Pulmonary infections caused by less frequently encountered slow-growing environmental mycobacteria

Pulmonary mycobacteriosis is usually caused by Mycobacterium tuberculosis or Mycobacterium avium complex. There are, however, other slow-growing mycobacteria that can cause pulmonary infection. Mycobacterium kansasii, Mycobacterium malmoense, Mycobacterium xenopi, Mycobacterium szulgai and Mycobacterium simiae typically infect middle-aged to elderly persons with preexisting lung disease. Differentiation of infection with these five mycobacteria from infection with Mycobacterium tuberculosis, by culture and determination of the antimicrobial susceptibility pattern of the organism are important for several reasons. All five organisms are found in water and soil. They probably infect humans from environmental habitats; human-to-human spread of infection is thought not to occur. Furthermore, isolation of the organisms in culture may represent contamination of the specimen or colonization of the patient, and not necessarily an infection. Finally, although the antituberculosis drugs-isoniazid, ethambutol, rifampin and streptomycin-have been used for treatment of infection with these five organisms, there are often differences between the antimycobacterial susceptibility patterns of Mycobacterium tuberculosis and those of the non-tuberculous mycobacteria. Thus, the optimal choice of drug therapy may differ from that used for tuberculosis.

Clarithromycin in the treatment of skin and skin structure infections: two multicenter clinical studies. Clarithromycin Study Group

BACKGROUND

Clarithromycin is a new macrolide analog of erythromycin with activity against a number of dermatologic pathogens.

METHODS

The efficacy and safety of clarithromycin, 250 mg bid, were compared with those of reference drugs, cefadroxil and erythromycin, in two multicenter studies: (1) a randomized, double-blind 45-center study, in which clarithromycin or cefadroxil 500 mg bid was given for 5-14 days; and (2) a single-blind 31-center study, in which clarithromycin or erythromycin, 250 mg qid, was given for < or = 14 days.

RESULTS

In the first study, efficacy and safety were evaluated in 299 and 538 patients, respectively. In the second study, the numbers were 141 and 261 patients, respectively. Overall, clarithromycin was as effective and safe as cefadroxil and erythromycin.

CONCLUSIONS

Clarithromycin provides an alternative therapy to cefadroxil and erythromycin for skin and skin structure infections, especially in beta-lactam allergic patients.

Activities of clarithromycin against eight slowly growing species of nontuberculous mycobacteria, determined by using a broth microdilution MIC system

MICs of clarithromycin against 324 clinical isolates belonging to eight species of slowly growing nontuberculous mycobacteria were determined by using a broth microdilution system. Isolates were inoculated into twofold drug dilutions in Middlebrook 7H9 broth (pH corrected to 7.4) and then incubated at 30 degrees C for 7 days for Mycobacterium marinum and for 14 days for all other species. The MIC for 90% of the strains (MIC90) was less than or equal to 0.5 micrograms/ml for isolates of Mycobacterium gordonae (6 strains), Mycobacterium scrofulaceum (5 strains), Mycobacterium szulgai (6 strains), and Mycobacterium kansasii (35 strains). MICs for M. marinum (25 strains) and Mycobacterium avium complex (237 strains) were higher, but 100% and 89% of the strains, respectively, were susceptible to less than or equal to 4 micrograms/ml. In contrast, MICs for five of six M. simiae strains were greater than 8 micrograms/ml, and the range of MICs for Mycobacterium nonchromogenicum varied from less than or equal to 0.125 to 8 micrograms/ml. For the 237 isolates of M. avium complex, the MIC50 was 2 micrograms/ml and the MIC90 was 8 micrograms/ml. MICs for most isolates (77%) were in the 1- to 4-micrograms/ml range. For the 80 isolates in this group known to be from AIDS patients, the MIC50 was 4 micrograms/ml and the MIC90 was 8 micrograms/ml. These MIC studies combined with preliminary clinical trials suggest that clarithromycin may be useful for drug therapy of most species of the slowly growing nontuberculous mycobacteria except M. simiae.

Agents of newly recognized or infrequently encountered mycobacterial diseases

This paper reviews recent information on the systematics and clinical significance of potentially pathogenic environmental mycobacteria. A short history of these mycobacteria is given. Information on species for which clinical and systematic aspects have already been well documented, i.e., Mycobacterium kansasii, M. marinum, M. scrofulaceum, M. simiae, M. szulgai, M. ulcerans, M. xenopi, and members of the M. fortuitum complex, is updated. Although the M. avium complex was extensively reviewed in earlier literature, major new systematic and clinical information is presented in some detail. Species that have received very limited prior coverage, i.e., M. asiaticum, M. haemophilum, M. malmoense, and M. shimoidei, are the main subjects of this review and are discussed in detail. The rare infections attributed to species that are normally considered nonpathogenic, i.e., M. gastri, M. gordonae, the M. terrae complex, and most of the rapidly growing mycobacteria outside of the M. fortuitum complex, are critically reviewed. Finally, suggestions are offered for practical measures that can minimize the risk of failing to isolate or misidentifying some of the more obscure potentially pathogenic environmental mycobacteria that are only infrequently recognized.