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Journal of Clinical Microbiology, May 2007, p. 1663-1665, Vol. 45, No. 5
0095-1137/07/$08.00+0 doi:10.1128/JCM.00119-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
Unusual Clinical Presentation of Mycobacterium fortuitum Infection in an Immunocompetent Woman
Corrado Serra,1
Giovanni Loi,1
Barbara Saddi,2
Marisa Pautasso,3 and
Aldo Manzin1*
Dipartimento di Scienze e Tecnologie Biomediche, Sezione di Microbiologia Medica, Policlinico Universitario Monserrato, Università degli Studi di Cagliari,1
Laboratorio Analisi, Ospedale S. S. Trinità,2
Laboratorio Analisi, Ospedale S. Giovanni di Dio, ASL 8 Cagliari, Italy3
Received 17 January 2007/
Returned for modification 25 February 2007/
Accepted 6 March 2007

ABSTRACT
The
Mycobacterium fortuitum group of rapidly growing nontuberculous
mycobacteria is an uncommon cause of renal infection, particularly
in otherwise healthy hosts. We describe a case of nephritis
due to
M. fortuitum in an immunocompetent woman with a clinical
and radiological diagnosis of renal tuberculosis.

CASE REPORT
A 32-year-old woman was admitted to the hospital because of
mild fever and severe pain in the right lumbar region of 3 days'
duration. Her history was negative for similar episodes or infections
with mycobacteria and other opportunistic microorganisms. Physical
examination revealed a temperature of 37.8°C and colic pain
in the right flank radiating to the back and the urogenital
tract. Laboratory findings demonstrated a hemoglobin level of
13.0 g/dl, a platelet count of 230
x 10
9/liter, and a white
cell count of 10.8
x 10
9/liter (neutrophils, 7.4
x 10
9/liter;
monocytes, 0.6
x 10
9/liter; lymphocytes, 3.3
x 10
9/liter; eosinophils,
0.1
x 10
9/liter; basophils, 0.1
x 10
9/liter); the erythrocyte
sedimentation rate was 24 mm/h, and C-reactive protein was at
295 mg/dl. Hematuria, proteinuria, and leukocyturia were not
detected by urine analysis. Serology for human immunodeficiency
virus and syphilis was negative, and the patient was not otherwise
immunocompromised. An ultrasound scan performed on the second
day showed a discrete dilation of the right pelvic calyceal
system without significant pathoanatomical renal changes.
The patient was discharged on the third day with a diagnosis of ureteral colic and lithiasis. However, she continued to suffer from lumbar pain and mild temperature and 2 months later was again admitted for urological evaluation. Intravenous urography showed moderate bilateral dilation of the midproximal ureter, a discrete deformity of the left upper-pole calyx with ill-defined margins, and a small, irregular collection of extracalyceal contrast material. Slight distention of the right pelvis was also noted. No functional abnormalities of the kidneys were documented. Infection with Mycobacterium tuberculosis was suspected on a clinical and radiological basis.
After 3 consecutive days of collection of urine samples for microbiological examination, antituberculosis treatment (with 300 mg oral isoniazid once a day and 600 mg oral rifampin once a day) was started, pending identification and sensitivity test results. Urine samples were decontaminated with equal volumes of N-acetyl-L-cysteine and 3% sodium hydroxide, neutralized with phosphate-buffered saline, centrifuged, and processed for microscopy, culture, and PCR analysis. Smears were stained by the Gram and conventional basic fuchsin (Ziehl-Neelsen) methods, and the resuspended specimens were inoculated into International Union tuberculosis medium (IUTM). PCR analysis using primers specific for M. tuberculosis and the Mycobacterium avium complex was also carried out. All tests performed on the first three urine samples gave negative results. However, acid-fast bacteria from two different urine specimens collected during antituberculosis therapy showed Ziehl-Neelsen staining. Bacteria also gave rise on day 4 to the rapid growth of small, buff-colored colonies on IUTM. Isolates were subcultured on blood agar, chocolate agar, MacConkey agar, brain heart infusion agar, and mannitol-salt agar, all incubated at 35°C in air, and on Sabouraud agar, incubated at 25°C and 35°C (all purchased from Difco Laboratories, Detroit, MI). Mycobacterium fortuitum was isolated and identified in cultures and in biochemical tests (Table 1). Specific diagnostic properties included rapid growth on MacConkey agar, nitrate positivity, urease positivity, catalase positivity at 68°C, NaCl tolerance positivity in Lowenstein-Jensen medium, tellurite positivity, 3-day arylsulfatase test positivity, and pyrazinamidase positivity. The identity of the isolate was confirmed by the API ZYM system (bioMérieux, Marcy l'Etoile, France) (profile, 63130165).
Antimicrobial susceptibility was tested by inoculation into
Middlebrook 7H11 agar supplemented with 10% oleic acid-albumin-dextrose-catalase
(Table
2). As susceptibility tests revealed resistance to the
antituberculosis drugs being administered, the treatment was
changed to ofloxacin (400 mg twice a day). After 3 days of ofloxacin
treatment, the temperature normalized and the lumbar pain disappeared.
Therapy was continued for 14 days. Repeated urine samples and
urine cultures were negative for acid-fast bacteria, and the
treatment was discontinued. The patient remained afebrile and
asymptomatic during follow-up.
M. fortuitum is a member of the rapidly growing Reunion Group
IV nontuberculous mycobacteria (NTM). It is a ubiquitous organism
frequently acquired from environmental sources, such as water,
soil, and dust, and from nosocomial sources (
4,
11,
16). It
is a gram-positive bacillus, frequently confused with contaminant
species such as corynebacteria.
M. fortuitum is increasingly
recognized as an opportunistic pathogen causing disseminated
infection, mainly in patients with impaired cellular immunity
or receiving glucocorticoid therapy. Rarely, infections can
occur in otherwise healthy hosts. Clinical presentation includes
mainly cutaneous and soft tissue infections; localized posttraumatic
wound infections; surgical wound infections, especially following
augmentation mammaplasty; and keratitis, lymphadenitis, arthritis,
osteomyelitis, rarely meningitis, endocarditis, and hepatitis,
mostly in AIDS patients or other immunocompromised patients
(
1,
6,
10,
12,
13,
14,
15,
16,
17). Previously rare, cases of
peritonitis in dialysis patients, catheter-associated sepsis,
pulmonary infection, and pleural effusion, including empyema,
are now on the increase (
2,
6,
7).
M. fortuitum has also been
associated with disseminated lesions in dialysis patients (
18).
It has been detected in urine from otherwise healthy hosts with
neither significant pathoanatomical nor functional renal disorders
(
9). Urinary
M. fortuitum infection in subjects suspected of
having a specific disease of the genitourinary tract has been
described only rarely, and then almost exclusively in immunocompromised
patients or patients being treated with glucocorticoids (
3,
5,
8).
Three main comments are in order. This is one of the few documented cases of renal infection due to M. fortuitum in an apparently healthy subject with a diagnosis of urolithiasis. This is the first case of M. fortuitum isolation in our laboratory. Prolonged urinary tract elimination of M. fortuitum has been described in the past, mainly from AIDS and hemodialysis patients (3, 8, 18), but primary localization in renal tissue causing a colic-like syndrome in an immunocompetent patient is a rare, possibly unique case. Secondly, the similar clinical and radiological presentations of atypical mycobacteriosis and renal tuberculosis suggest the need for specific microbiological and drug susceptibility investigations to avoid the administration of unsuccessful and potentially harmful treatments, given that most rapidly growing NTM are resistant to traditional antituberculosis agents (11). In this respect, although cases of NTM infection have increased recently because of the dissemination of human immunodeficiency virus infection and the extensive use of chemotherapy and immunosuppressive treatments, isolation and identification of NTM from otherwise healthy hosts are becoming more common (11, 15, 16). Finally, this report highlights the role and potential of traditional culture methods in the identification of atypical microorganisms. A number of commercially available automated assays have recently been developed, and newer genetic methods, such as molecular probes, PCR-based restriction fragment length polymorphism analysis, and 16S rRNA gene sequence analysis, have been recommended for more-accurate detection and characterization of tuberculous mycobacteria and NTM. Nevertheless, conventional biochemical and culture methods, together with acid-fast smear microscopy, still retain all of their potential in the diagnostic work-up of and therapeutic approach to these increasingly common infections.

FOOTNOTES
* Corresponding author. Mailing address: Servizio di Microbiologia Clinica, Policlinico Universitario, Università di Cagliari, Presidio di Monserrato, Strada Statale 554Bivio Sestu, 09042 Cagliari, Italy. Phone: 39.070.5109.6350. Fax: 39.070.675.8482. E-mail:
aldomanzin{at}pacs.unica.it 
Published ahead of print on 14 March 2007. 

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Journal of Clinical Microbiology, May 2007, p. 1663-1665, Vol. 45, No. 5
0095-1137/07/$08.00+0 doi:10.1128/JCM.00119-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.