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


METHODS
Retrospective chart and laboratory review.


METHODS
University-affiliated tertiary-care city hospital.


METHODS
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).


METHODS
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).


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.
Donnabella
V
V
Bellevue Chest and Mycobacteriology Services, New York University School of Medicine, New York, NY 10016, USA. donnav01@popmail.med.nyu.edu
Salazar-Schicchi
J
J
Bonk
S
S
Hanna
B
B
Rom
W N
WN
D017088:AIDS-Related Opportunistic Infections / Q000453:epidemiology; D000328:Adult; D000368:Aged; D001431:Bacteriological Techniques / Q000706:statistics & numerical data; D021821:Communicable Diseases, Emerging / Q000453:epidemiology*; D003470:Culture Media; D005260:Female; D006679:HIV Seropositivity / Q000453:epidemiology; D006785:Hospitals, University / Q000706:statistics & numerical data; D006786:Hospitals, Urban / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008913:Minority Groups / Q000706:statistics & numerical data; D009165:Mycobacterium Infections, Nontuberculous / Q000453:epidemiology*; D019912:Mycobacterium xenopi / Q000302:isolation & purification*; D009519:New York City / Q000453:epidemiology; D012189:Retrospective Studies; D012737:Sex Factors; D014397:Tuberculosis, Pulmonary / Q000453:epidemiology
D003470:Culture Media