Chest
Volume 118, Issue 5, November 2000, Pages 1365-1370
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Clinical Investigations
Tuberculosis
Increasing Incidence of Mycobacterium xenopi at Bellevue Hospital: An Emerging Pathogen or a Product of Improved Laboratory Methods?

https://doi.org/10.1378/chest.118.5.1365Get rights and content

Study objectives

To investigate the dramatic rise innumber of Mycobacterium xenopi isolates identified inour mycobacteriology laboratory, and to determine if this increase wasdue to emerging clinical pathology or to changes in culturetechnique.

Design

Retrospective chart and laboratoryreview.

Setting

University-affiliated tertiary-carecity hospital.

Patients

Eighty-one patients with asingle culture positive for M xenopi from 1975 to 1994(period 1), and 47 patients with two or more cultures positive from1994 to 1998 (period 2).

Interventions

The Bellevuemycobacteriology laboratory changed the culture medium from solidLowenstein-Jensen medium (used from 1975 to 1990) to the Septi-CheckAFB System (Becton-Dickinson; Glencoe, MD; used from 1991 to 1994), tothe Mycobacteria Growth Indication Tube (MGIT; Becton-Dickinson; usedfrom 1995 to 1998).

Measurements and results

Werecovered 29 M xenopi isolates from 1975 to 1990, 12isolates from 1991 to 1994, and 381 isolates from 1995 to 1998. Wesubsequently identified and reviewed the medical records of all 81patients who were culture positive for M xenopi from1975 to 1994 (period 1), and 46 patients who had two or more isolatesculture positive for M xenopi from 1995 to 1998 (period2). For period 1, 75% of the subjects were male, 80% were minority,and at least 43% were HIV positive. Only one patient had clinicalM 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 hadclinical M xenopi lung disease.

Conclusions

The dramatic increase in Mxenopi isolates noted in our hospital was due to a moresensitive laboratory isolation technique, rather than a true increasein clinical disease. Other hospitals utilizing MGIT systems formycobacterial recovery should interpret positive Mxenopi cultures with caution.

Section snippets

Materials and Methods

A list of all patients with positive culture results for Mxenopi from January 1, 1975, to October 1995, and two or morepositive culture results from November 1995 to January 1998 wasobtained from the mycobacteriology laboratory records of BellevueHospital. Medical records were reviewed for age, gender, ethnicity,chest radiograph, pathology specimens, HIV status, and clinical course.

Sputum samples using a nebulized saline solution induction technique orBAL samples were obtained. Specimens were

Results

During period 1 (January 1975 to October 1995), we identified 81patients (61 male and 20 female) with at least one M xenopiisolate. Specimens were recovered from sputum alone (60 cases), BAL (20cases), and blood and sputum (1 case). Twenty-nine cultures of Mxenopi were isolated prior to 1991, 12 from 1991 through 1993, and40 from January 1994 to September 1995. Of the 81 patients, 33 wereAfrican American, 26 were Hispanic, 16 were white, and 6 were Asian,reflecting the ethnic distribution at

Discussion

We have observed a dramatic increase in M xenopiisolates in the Bellevue Hospital mycobacteriology laboratory, from 29isolates over a 15-year period to 381 isolates over a recent 3-yearperiod. This dramatic increase was coincident with the institution ofmore-sensitive culture techniques in our mycobacteriology laboratory.Despite these 422 patients' isolates, we identified only threepatients with clinical M xenopi pulmonary disease. Two ofthese patients had severe COPD, and the third patient had

ACKNOWLEDGMENT

The authors thank Drs. Claudia Plottel, KarenHoover, and Fred Bevelacqua for sharing information on their patients;the New York City mycobacteriology laboratory for sharing its dataconcerning the changing isolate profiles; and Jessie A. Pierre foreditorial assistance.

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