Disseminated Mycobacterium xenopi infection

Arthritis Due toMycobacterium xenopi:A Retrospective Study of 7 Cases in France

BACKGROUND

Mycobacterium xenopi is a nontuberculous mycobacterium responsible for opportunistic and nosocomial infections, chiefly of the lung; few cases of bone and joint infection have been reported. From July 1989 through May 1993, an outbreak of 58 cases of nosocomial discitis due to M. xenopi infection following percutaneous nucleotomy occurred in a French hospital. Peripheral M. xenopi arthritis seems exceedingly rare. We conducted a study to assess the epidemiological and clinical patterns of M. xenopi arthritis.

METHODS

We retrospectively reviewed cases of M. xenopi arthritis reported from May 1993 through October 2004.

RESULTS

We identified 7 cases, all of which occurred after invasive surgical procedures were performed on the affected joint, suggesting a nosocomial pattern of infection. Two patients may have been contaminated at the hospital where the M. xenopi discitis outbreak occurred. No source was identified in the other 5 patients. Despite the probable nosocomial nature of the infections, the diagnosis was delayed (mean time until diagnosis, 50 months). Repeated collection of deep tissue specimens for bacteriological analysis seemed crucial to the diagnosis. The treatment relied on combination antimicrobial therapy and surgery. Among 11 cases of M. xenopi osteoarticular infection reported in the literature from 1975 to 2005, (arthritis in 9 cases and osteitis in 2), none were nosocomial.

CONCLUSION

A high index of suspicion should be maintained to ensure the diagnosis of M. xenopi arthritis before chronic monoarthritis and before the development of irreversible joint damage.

Increasing incidence of Mycobacterium xenopi at Bellevue hospital: An emerging pathogen or a product of improved laboratory methods?

STUDY OBJECTIVES

To investigate the dramatic rise in number of Mycobacterium xenopi isolates identified in our mycobacteriology laboratory, and to determine if this increase was due to emerging clinical pathology or to changes in culture technique.

DESIGN

Retrospective chart and laboratory review.

SETTING

University-affiliated tertiary-care city hospital.

PATIENTS

Eighty-one patients with a single culture positive for M xenopi from 1975 to 1994 (period 1), and 47 patients with two or more cultures positive from 1994 to 1998 (period 2).

INTERVENTIONS

The Bellevue mycobacteriology laboratory changed the culture medium from solid Lowenstein-Jensen medium (used from 1975 to 1990) to the Septi-Check AFB System (Becton-Dickinson; Glencoe, MD; used from 1991 to 1994), to the Mycobacteria Growth Indication Tube (MGIT; Becton-Dickinson; used from 1995 to 1998).

MEASUREMENTS AND RESULTS

We recovered 29 M xenopi isolates from 1975 to 1990, 12 isolates from 1991 to 1994, and 381 isolates from 1995 to 1998. We subsequently identified and reviewed the medical records of all 81 patients who were culture positive for M xenopi from 1975 to 1994 (period 1), and 46 patients who had two or more isolates culture positive for M xenopi from 1995 to 1998 (period 2). For period 1, 75% of the subjects were male, 80% were minority, and at least 43% were HIV positive. Only one patient had clinical M xenopi lung disease during this period. For period 2, 79% of the subjects were male, 83% were minority, and at least 58% were HIV positive; two additional patients were identified who had clinical M xenopi lung disease.

CONCLUSIONS

The dramatic increase in M xenopi isolates noted in our hospital was due to a more sensitive laboratory isolation technique, rather than a true increase in clinical disease. Other hospitals utilizing MGIT systems for mycobacterial recovery should interpret positive M xenopi cultures with caution.

Laboratory and clinical evaluation of Mycobacterium xenopi isolates

Mycobacterium xenopi and Mycobacterium avium complex (MAC) are biochemically similar. To define the laboratory characteristics of M. xenopi that distinguish it from MAC, 53 M. xenopi isolates from different areas in the United States and 47 isolates recovered at one hospital were evaluated by 13 biochemical tests, AccuProbe MAC (Gen-Probe, Inc., San Diego, CA, USA), colony morphology, formation of X-colonies, pigmentation in response to light, growth on MacConkey agar without crystal violet, and relative growth rates at 25 degrees C, 36 degrees C, and 45 degrees C on solid media. Relative growth rates of 10 M. xenopi and 11 MAC isolates were measured at 25 degrees C, 36 degrees C, and 42 degrees C in Middlebrook broth processed using the BACTEC TB System. Ten M. xenopi were tested for p-nitro-alpha-acetylamino-beta-hydroxypropiophenone inhibition at 36 degrees C and 42 degrees C. Reevaluation of 81 isolates previously identified as MAC by biochemical tests alone revealed that two were M. xenopi. The most reliable characteristics distinguishing M. xenopi from MAC were the presence of X-colonies (M. xenopi 97% vs MAC 1%), positive 3-day arylsulfatase (M. xenopi 88% vs MAC 1%), growth at 25 degrees C (M. xenopi 0% vs MAC 100%), and AccuProbe MAC test results (M. xenopi 0% hybridized). Retrospective chart review of 37 patients using American Thoracic Society criteria revealed that six (16%) patients had clinically important isolates. At one of our hospitals M. xenopi was the second most common mycobacterial species isolated for 1990-1992, accounting for 27% of all isolates, whereas at our other hospital it accounted for 1% of isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Valvular tuberculous endocarditis: a case report and review of the literature

Tuberculous valvular endocarditis is exceptionally rare. It is usually manifest in the context of miliary tuberculosis, and in all but one case the diagnoses have been made at necropsy. Because of its rarity there is still uncertainty as to whether true tuberculous endocarditis exists as a clinical entity. This paper describes a case of miliary tuberculosis with aortic valvulitis that resolved on antituberculous therapy.