Human infections due to Mycobacterium lentiflavum.

Abstract

Three cases of human disease due to Mycobacterium lentiflavum are reported. In the first, the mycobacterium was responsible for chronic pulmonary disease in an elderly woman; in the second, it gave rise to cervical lymphadenitis in a child; and in the third, it caused a liver abscess in a young AIDS patient.

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JOURNAL OF CLINICAL MICROBIOLOGY, Feb. 2002, p. 728–729
0095-1137/02/$04.00?0DOI: 10.1128/JCM.40.02.728–729.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Vol. 40, No. 2
Human Infections Due to Mycobacterium lentiflavum
Enrico Tortoli,1* Alessandro Bartoloni,2Maria Luigia Erba,3Egle Levrè,4Natalia Lombardi,4
Antonia Mantella,2and Lorenzo Mecocci5
Regional Reference Center for Mycobacteria, Microbiology and Virology Laboratory, Careggi Hospital,1Infectious Diseases Unit,
University of Florence,2and Infectious Disease Unit, S. Maria Annunziata Hospital,5Florence, Lung Disease Center,
S. Anna Hospital, Como,3and Institute of Hygiene, University of Pisa, Pisa,4Italy
Received 5 January 2001/Returned for modification 24 April 2001/Accepted 14 August 2001
Three cases of human disease due to Mycobacterium lentiflavum are reported. In the first, the mycobacterium
was responsible for chronic pulmonary disease in an elderly woman; in the second, it gave rise to cervical
lymphadenitis in a child; and in the third, it caused a liver abscess in a young AIDS patient.
CASE REPORTS
Case 1. A 61-year-old woman, bronchiectastic since the age
of 30 and with a history of surgical intervention and reiterated
cancer chemotherapy because of an ovarian adenocarcinoma,
underwent in 1995 a thoracic X ray in the presence of produc-
tive cough, weight loss, and slight fever. The radiographic in-
vestigation revealed a reticulonodular alteration of the right
upper lobe and adenopathy. Following isolation from sputum
of numerous colonies of an unidentified scotochromogenic my-
cobacterium, the patient was hospitalized and treatment with
rifampin, isoniazid, and pyrazinamide was undertaken and
continued for several months. One year later, the patient was
still smear positive and growth from cultures of a mycobacte-
rium subsequently identified as Mycobacterium lentiflavum led
to replacement of the previous antituberculosis treatment with
rifabutin, ethambutol, clarithromycin, and ciprofloxacin. The
patient was again microscopically positive for acid-fast bacilli
18 months later when an X ray did not reveal any improve-
ment. Further isolation of M. lentiflavum from sputum led to
our acknowledging that the treatment was ineffective. At
present, the clinical picture remains unchanged and the pa-
tient’s sputum vacillates between being positive and negative
for M. lentiflavum.
Case 2. M. lentiflavum was isolated from a 4-year-old boy
suffering from left cervical lymphadenitis. After excision of the
gland, the patient completely recovered and no relapse was
observed at follow-up 1 year later.
Case 3. The third case concerns a severely immunocompro-
mised AIDS patient. The subject, a 45-year-old bisexual man,
was first hospitalized in 1998 because of fever, weight loss,
asthenia, lumbago, and oral candidiasis. On that occasion, he
was found to be human immunodeficiency virus type 1 sero-
positive (viral load, ?500,000 copies/ml), with 61 CD4?lym-
phocytes/ml. A thoracic X ray revealed a basal opacity in the
left lung, while echography and computerized tomography
showed a hepatic nodular lesion, 5 cm in diameter and with a
hypodense center, most likely due to inflammation. Comput-
erized tomography and scintigraphic studies showed that the
fourth dorsal vertebra appeared deformed, most likely as a
result of septic inflammation. Treatment with three antiretro-
viral drugs and with rifabutin and clarithromycin was under-
taken. An evident improvement of clinical conditions was soon
noted, characterized by disappearance of fever, gain in weight,
resolution of the lung opacity, and improvement of the radio-
graphic vertebral picture. There was, however, no change in
hepatic status. The microbiological test results of a needle
biopsy indicated the presence of M. lentiflavum. This finding
was assumed to be the link among the pulmonary, bony, and
hepatic symptoms. Ethambutol and ciprofloxacin were added
to the previous antimycobacterial therapy, but no appreciable
results were obtained. In fact, 2 months later, the nodular
lesion had enlarged to 6 cm in diameter and continued growing
for the subsequent 4 months during which the antimycobacte-
rial treatment was reduced to rifabutin and clarithromycin
only. Finally, a lobectomy was performed, and histologic ex-
amination led to the diagnosis of non-Hodgkin’s lymphoma. At
present (1 year later), the patient is in good condition, with a
viral load of ?400 copies/ml.
Microbiologic analysis. Forty-seven strains of M. lentiflavum
have been identified in our laboratory within the last 4 years.
From this conspicuous cluster, a homogeneous picture of the
characteristics of M. lentiflavum has emerged. The organism
grows slowly at temperatures ranging from 25 to 37°C and is
characterized by small, flat, smooth, scotochromogenic colo-
nies. Its biochemical features (3) are similar to those of
Mycobacterium avium, the majority of tests for both being
negative, with only the thermostable catalase test being often
positive (Table 1). M. lentiflavum is extremely resistant to an-
timycobacterial drugs; MICs, particularly of isoniazid and ri-
fampin, are very high (5). Lipid analyses have revealed the
presence of ?-mycolates, ??-mycolates, and keto-mycolates (1).
The high-performance liquid chromatographic profile is, as
defined in the M. lentiflavum sp. nov. description (4), very
similar to that of Mycobacterium simiae: however, it is distin-
guished from that of the latter by a closer arrangement of the
first and second clusters of peaks (5) (Fig. 1). Genetic investi-
gation of 16S ribosomal DNA has revealed a unique sequence
in region A and a short helix 18 in region B, a feature distinc-
* Corresponding author. Mailing address: Laboratorio di Microbio-
logia e Virologia, Piastra dei Servizi, Viale Morgagni 85, 50134 Flo-
rence, Italy. Phone: 39-055-4279199. Fax: 39-055-4279830. E-mail:
e.tortoli@libero.it.
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tive of rapidly growing mycobacteria but shared also by M.
simiae and an increasing number of related organisms, (4).
Discussion. M. lentiflavum was recognized as a new species
in 1996 on the basis of a cluster of 22 isolates (4). Although 11
such isolates were due to a contaminated bronchoscope, all the
others were independently isolated in Germany, Switzerland,
and the United States. Among them, one isolate was clinically
significant, as it had been isolated from a vertebral disk in an
elderly patient suffering from spondilodiscitis (4). One year
later, a report concerning two cases of cervical lymphadenitis
in two very young children was published (2). No other infor-
mation about the clinical significance of M. lentiflavum has
been published so far.
The isolation of a nontuberculous mycobacterium always
raises doubts about clinical significance, and the touchstone in
such cases is represented by the ad hoc diagnostic criteria
defined several years ago by the American Thoracic Society
(6). The medical relevance of the M. lentiflavum isolations
reported here appears, on the basis of such diagnostic criteria,
unquestionable, because in one case the organism was repeat-
edly isolated from sputum over a period of 4 years and in the
others it was observed in and isolated from biopsy specimens.
Some small doubt exists as to the clinical importance of the
hepatic isolate, since there was another active disease process
(lymphoma) predisposing the patient to opportunistic coloni-
zation or infection.
An approximate assessment of the prevalence of cases in
which an M. lentiflavum isolation may be clinically significant is
about 10% in our survey, as of the 29 isolates (out of 47
investigated in our laboratory) for which it was possible to get
clinical information, only 3 could be clinically assessed.
These cases serve to confirm the potential pathogenicity of
M. lentiflavum, with cervical lymphadenitis in children appear-
ing to be the most common infection, accounting for one half
of the pathologies due to M. lentiflavum reported so far. On the
contrary, the cases described here represent the first report of
M. lentiflavum pulmonary disease.
Of grave concern is the apparent multidrug resistance of M.
lentiflavum, first described in in vitro testing (5) and now par-
tially confirmed in vivo by the two cases reported here in which
patients remained unresponsive to therapy. If this organism is
truly as resistant as our limited data suggest, then it truly may
be an emerging opportunistic pathogen.
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FIG. 1. Comparison of representative high-pressure liquid chro-
matographic patterns of mycolic acid bromophenacyl esters of M.
lentiflavum and M. simiae. IS, internal standard.
TABLE 1. Biochemical and cultural features of M. lentiflavum,
as determined by investigation of 47 clinical isolates
Test Resulta
Niacin accumulation......................................................................?
Nitrate reduction............................................................................?
Room temperature catalase..........................................................?
68°C catalase...................................................................................?
Catalase ?45 mm of foam............................................................?
Tween 80 hydrolysis.......................................................................?
Tellurite reduction.........................................................................?
?-Glucosidase.................................................................................?
Arylsulfatase ...................................................................................?
Urease .............................................................................................?
Growth rate ....................................................................................Slow
Growth at 25°C ..............................................................................?
Growth at 45°C ..............................................................................?
Pigmentation
Scotochromogenic......................................................................?
Photochromogenic .....................................................................?
Colony morphology........................................................................Smooth
Growth on MacConkey agar........................................................?
Tolerance for:
NaCl (5%)...................................................................................?
Thiophene-carboxylic acid hydrazide (1 ?g/ml).....................?
Thiacetazone (10 ?g/ml)...........................................................?
p-Nitrobenzoic acid (500 ?g/ml)..............................................?
Hydroxylamine hydrochloride (500 ?g/ml).............................?
Isoniazid (1 ?g/ml) ....................................................................?
Oleate (250 ?g/ml) ....................................................................?
a?, positive; ?, variable; ?, negative.
VOL. 40, 2002 CASE REPORTS729