Acrophialophora fusispora Brain Abscess in a Child with Acute Lymphoblastic Leukemia: Review of Cases and Taxonomy

Abstract

A 12-year-old girl with acute lymphoblastic leukemia was referred to King Faisal Specialist Hospital and Research Center. The diagnosis without central nervous system (CNS) involvement was confirmed on admission, and chemotherapy was initiated according to the Children Cancer Group (CCG) 1882 protocol for high-risk-group leukemia. During neutropenia amphotericin B (AMB) (1 mg/kg of body weight/day) was initiated for presumed fungal infection when a computed tomography (CT) scan of the chest revealed multiple nodular densities. After 3 weeks of AMB therapy, a follow-up chest CT revealed progression of the pulmonary nodules. The patient subsequently suffered a seizure, and a CT scan of the brain was consistent with infarction or hemorrhage. Because of progression of pulmonary lesions while receiving AMB, antifungal therapy was changed to liposomal AMB (LAMB) (6 mg/kg/day). Despite 26 days of LAMB, the patient continued to have intermittent fever, and CT and magnetic resonance imaging of the brain demonstrated findings consistent with a brain abscess. Aspiration of brain abscess was performed and the Gomori methenamine silver stain was positive for hyphal elements. Culture of this material grew Acrophialophora fusispora. Lung biopsy showed necrotizing fungal pneumonia with negative culture. The dosage of LAMB was increased, and itraconazole (ITRA) was added; subsequently LAMB was discontinued and therapy was continued with ITRA alone. The patient demonstrated clinical and radiological improvement. In vitro, the isolate was susceptible to low concentrations of AMB and ITRA. A. fusispora is a thermotolerant, fast-growing fungus with neurotropic potential. We report the first case of human infection involving the CNS. Acrophialophora resembles Paecilomyces but differs in having colonies that become dark and in the development of phialides along the sides or at the tips of echinulate brown conidiophores. Conidia are borne in long chains and are smooth or ornamented with fine-to-coarse echinulations, sometimes in spiral bands. The taxonomy of the genus Acrophialophora is reviewed, and Acrophialophora nainiana and Acrophialophora levis are considered as synonyms of A. fusispora.

Full text

JOURNAL OF CLINICAL MICROBIOLOGY,
0095-1137/00/$04.00⫹0Dec. 2000, p. 4569–4576 Vol. 38, No. 12
Copyright © 2000, American Society for Microbiology. All Rights Reserved.
Acrophialophora fusispora Brain Abscess in a Child with Acute
Lymphoblastic Leukemia: Review of Cases and Taxonomy
I. Z. AL-MOHSEN,
1
* D. A. SUTTON,
2
L. SIGLER,
3
E. ALMODOVAR,
1
N. MAHGOUB,
1
H. FRAYHA,
1
S. AL-HAJJAR,
1
M. G. RINALDI,
2
AND T. J. WALSH
4
King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
1
; Fungus Testing Laboratory, University of
Texas Health Science Center, San Antonio, Texas
2
; University of Alberta Microfungus Collection, Edmonton, Alberta,
Canada
3
; and Pediatric Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
4
Received 6 June 2000/Returned for modification 10 July 2000/Accepted 21 September 2000
A 12-year-old girl with acute lymphoblastic leukemia was referred to King Faisal Specialist Hospital and
Research Center. The diagnosis without central nervous system (CNS) involvement was confirmed on admis-
sion, and chemotherapy was initiated according to the Children Cancer Group (CCG) 1882 protocol for
high-risk-group leukemia. During neutropenia amphotericin B (AMB) (1 mg/kg of body weight/day) was
initiated for presumed fungal infection when a computed tomography (CT) scan of the chest revealed multiple
nodular densities. After 3 weeks of AMB therapy, a follow-up chest CT revealed progression of the pulmonary
nodules. The patient subsequently suffered a seizure, and a CT scan of the brain was consistent with infarction
or hemorrhage. Because of progression of pulmonary lesions while receiving AMB, antifungal therapy was
changed to liposomal AMB (LAMB) (6 mg/kg/day). Despite 26 days of LAMB, the patient continued to have
intermittent fever, and CT and magnetic resonance imaging of the brain demonstrated findings consistent with
a brain abscess. Aspiration of brain abscess was performed and the Gomori methenamine silver stain was
positive for hyphal elements. Culture of this material grew Acrophialophora fusispora. Lung biopsy showed
necrotizing fungal pneumonia with negative culture. The dosage of LAMB was increased, and itraconazole
(ITRA) was added; subsequently LAMB was discontinued and therapy was continued with ITRA alone. The
patient demonstrated clinical and radiological improvement. In vitro, the isolate was susceptible to low
concentrations of AMB and ITRA. A. fusispora is a thermotolerant, fast-growing fungus with neurotropic
potential. We report the first case of human infection involving the CNS. Acrophialophora resembles Paecilo-
myces but differs in having colonies that become dark and in the development of phialides along the sides or
at the tips of echinulate brown conidiophores. Conidia are borne in long chains and are smooth or ornamented
with fine-to-coarse echinulations, sometimes in spiral bands. The taxonomy of the genus Acrophialophora is
reviewed, and Acrophialophora nainiana and Acrophialophora levis are considered as synonyms of A. fusispora.
During the past 2 decades invasive fungal infections have
emerged as a major cause of morbidity and mortality in an
expanding spectrum of high-risk immunocompromised pa-
tients (27). The numbers and types of saprobic and opportu-
nistic filamentous fungi that have been documented as etio-
logic agents of invasive diseases continue to escalate (15, 18,
26). Candida, Aspergillus, Trichosporon, and Fusarium species
are the leading fungal pathogens in patients with hematologic
malignancies (1), but less common molds are increasingly be-
ing documented as occasional pathogens (2, 12). Acrophialo-
phora fusispora is a thermotolerant soil fungus that grows well
at 45°C or higher temperatures. It has been reported once from
a human corneal infection (22) and implicated in disseminated
infection involving the brain in two dogs. In one of the latter
cases, the etiologic agent was originally identified as Scopulari-
opsis chartarum (29), suggesting that A. fusispora may go un-
recognized by diagnostic laboratories. We describe the first
case of human cerebral brain abscess due to A. fusispora and
use this case to compare microbiologic features and antifungal
susceptibilities of pathogenic and nonpathogenic isolates and
to review the taxonomy of the genus Acrophialophora.
CASE REPORT
Clinical course. The patient was a 12-year-old Sudanese girl
diagnosed with acute lymphoblastic leukemia on 12 July 1998.
She received four courses of induction chemotherapy with
vincristine and prednisone for 4 weeks in Sudan prior to ad-
mission to the King Faisal Specialist Hospital and Research
Center (KFSH&RC) on 14 August 1998. The diagnosis of
acute lymphoblastic leukemia without central nervous system
(CNS) involvement was confirmed, and chemotherapy was initi-
ated according to the CCG 1882 protocol for high-risk leukemia.
This protocol included weekly vincristine and daunomycin and
daily dexamethazone. After 2 weeks of chemotherapy, hyper-
glycemia and hypertension developed, following which dexa-
methasone was changed to prednisone to complete the 4 weeks
of induction therapy. The patient received nine doses of as-
paraginase over 4 weeks. A bone marrow aspirate at 28 days
postinduction showed remission of leukemia. The consolida-
tion phase of chemotherapy consisted of cytosine arabinoside,
6-mercaptopurine, and cyclophosphamide, as well as intrathe-
cal methotrexate. Subsequently the patient continued on main-
tenance chemotherapy.
At her initial presentation to the KFSH&RC, the patient
was febrile with no focus of infection. Empirical broad-spec-
trum antibiotics (ceftazidime and gentamicin) were initiated.
Subsequently vancomycin was added. As her fever persisted
during neutropenia, while she was on broad-spectrum antibi-
otics, amphotericin B (AMB), 1 mg/kg of body weight/day, was
* Corresponding author. Mailing address: Department of Pediatrics,
King Faisal Specialist Hospital & Research Center, P.O. Box 3354,
Riyadh 11211, Saudi Arabia. Phone: 966 1 442 7762. Fax: 966 1 442
7784. E-mail: imohsen@kfshrc.edu.sa or ialmohsen@hotmail.com.
4569

initiated on the 5th day for presumed fungal infection when the
chest computed tomography (CT) scan revealed multiple nod-
ular densities. A lung biopsy was deferred because of coagu-
lopathy. After 3 weeks of AMB therapy, a follow-up chest CT
scan revealed an increase in size and numbers of pulmonary
nodules (Fig. 1). The patient subsequently suffered a seizure,
and a CT scan of the brain was consistent with infarction or
hemorrhage. Antifungal therapy was changed to liposomal
AMB (LAMB) (AmBisome), 6 mg/kg/day, due to the progres-
sion of pulmonary lesions while receiving AMB. Despite 26
days of LAMB, the patient continued to have intermittent
fever, and a follow-up CT and magnetic resonance imaging of
the brain demonstrated a ring-enhancing lesion at the site of
previously reported infarct. These findings were consistent
with a brain abscess in the parieto-occipital area (Fig. 2). As-
piration of the brain abscess was performed. Thick yellowish
pus was drained from the abscess, and the Gomori methena-
mine silver (GMS) stain was positive for a large number of
septate hyphae (Fig. 3). Culture of the brain abscess aspirate
grew a fungus closely resembling a Paecilomyces species.
The patient also underwent right thoracotomy, and there
was a cavitating fungal lesion in the lower lobe penetrating
through the diaphragm. Histopathology of this lesion was con-
sistent with necrotizing fungal pneumonia with septate hyphae
(Fig. 4); however, the culture of this tissue yielded no growth.
Because of the radiological and histopathologic findings the
dosage of LAMB was increased to 10 mg/kg/day and itracon-
azole (ITRA), 7.5 mg/kg/day, was added and increased to 7.5
mg/kg every 12 h according to levels in serum. The patient also
received granulocyte colony-stimulating factor, 5 ␮g/kg/day, as
adjunctive therapy. Clinical and radiological improvement oc-
curred after the LAMB dose was increased and ITRA was
added. This combination was continued for 8 months, follow-
ing which LAMB was discontinued and ITRA was continued
as suppressive therapy. Repeated CT of the chest and brain 3
months after LAMB was discontinued showed no progression
of the lesions. The child currently remains stable on ITRA, 15
mg/kg/day, with concomitant reduction in size of the brain
abscess and resolution of the lung nodules.
Histopathology. The specimen from the brain aspirate con-
sisted of multiple tiny pieces of grayish soft and necrotic white
tissue. The frozen section showed necrotic brain tissue with
granulomatous inflammation suggestive of fungal infection.
GMS stain revealed numerous branching septate hyphae (Fig.
3). The lung biopsy consisted of a central rounded irregular
cavity measuring 3 cm in diameter filled with creamy gray solid
mass separated from the surrounding tissue (Fig. 4A). The
microscopic findings were consistent with necrotizing cavitat-
ing invasive fungal pneumonia (Fig. 4B). The GMS stain dem-
onstrated multiple hyphal elements similar to those in the
brain.
MATERIALS AND METHODS
Mycology. The aspirate of the brain abscess and the lung biopsy were plated on
Sabouraud dextrose agar (SDA) and brain heart infusion agar. No organisms
grew from lung biopsy. The brain abscess aspirate yielded several colonies of a
mold that was identified initially as a Paecilomyces species based on its formation
of conidia in short chains. The isolate was referred to the Fungus Testing
Laboratory, Department of Pathology, University of Texas Health Science Cen-
ter at San Antonio for further identification and susceptibility testing. There, the
isolate was examined on potato flakes agar (PFA) prepared in-house and incu-
bated at room temperature in ambient air with alternating daylight and darkness.
Based on its colonial and microscopic features, the fungus was identified as A.
fusispora and given accession number UTHSC 98-2508. The isolate was subse-
FIG. 1. Chest CT showing nodular lung lesions with cavitation.
FIG. 2. (A) CT of the brain with contrast demonstrating the brain lesion in
the left parieto-occipital region. (B) Brain magnetic resonance imaging with
contrast showing the ring-enhancing lesion in the left parieto-occipital region
with minimal surrounding edema.
4570 AL-MOHSEN ET AL. J. CLIN.MICROBIOL.

quently referred to the University of Alberta Microfungus Collection and Her-
barium, Edmonton, Alberta, Canada, accession number UAMH 9508, for com-
parison with six other isolates of this species (Table 1) (23). Cultural and
microscopic features were examined on SDA, PFA, and potato dextrose agar
(Difco Laboratories, Detroit, Mich.) plates incubated at 30 and 37°C. Terms for
colony colors are according to Kornerup and Wanscher (14). PFA slant cultures
were evaluated for growth at 25, 35, and 42°C. The case isolate (UTMB 3307 ⫽
UTHSC R-3122 ⫽UAMH 9684) from a dog with systemic mycosis (Welsh,
personal communication) was acquired later and included in some comparative
analyses (Table 1).
Scanning electron microscopy. Stubs were mounted with Spot-O-Glue labels
(Avery, Diamond Bar, Calif.) and touched to the fungal culture. Preps were
coated with gold-palladium using a Balzers MED 010 vacuum evaporator (Tech-
notrade International, Inc., Manchester, N.H.) and examined with a JEOL (To-
kyo, Japan) 840A microscope.
Antifungal susceptibility testing. The case isolate and six additional strains
(Table 2) were tested in a broth macrodilution method using NCCLS reference
standard M27-T or M27-A (16, 17) modified for filamentous fungi to determine
their susceptibility to antifungal agents. Isolates were grown on PFA slants at
25°C for approximately 1 week. Mycelium was flooded with sterile distilled water
and scraped to obtain a conidial suspension. The case isolate was tested in 1999
utilizing M27-A in which conidial suspensions were standardized by hemacytom-
eter conidial counts, with a final inoculum concentration of 1.0 ⫻10
4
CFU/ml.
Isolates 96-2378 and R-2940 through R-2944 were tested in 1997 utilizing M27-T
in which the suspension was standardized spectrophotometrically at 95%T at 530
nm and then diluted 1:10 to provide a final inoculum concentration of 1.0 ⫻10
4
CFU/ml.
Antifungal agents and ranges tested included AMB (E. R. Squibb & Sons,
Princeton, N.J.), 0.03 to 16 ␮g/ml; 5-fluorocytosine (5-FC) (Roche Laboratories,
Nutley, N.J.), 0.125 to 64 ␮g/ml; fluconazole (FLU) (Pfizer, Inc., New York,
N.Y.), 0.125 to 64 ␮g/ml; ITRA (Janssen Pharmaceutica, Titusville, N.J.), 0.03 to
16 ␮g/ml; and miconazole (MON), 0.03 to 16 ␮g/ml. Tubes were incubated at
35°C and read at 24 and 48 h. MICs were defined based on the first tube with a
score of 0 (optically clear) for AMB and a score of 2 (a reduction of 80% or more
in turbidity as contrasted with the drug-free control tube) for the other agents
tested. Minimum lethal concentrations (MLCs) were determined for AMB by
plating 100 ␮l of the 24-h growth from the drug-free control tube, the MIC tube,
and each tube with a concentration above the MIC onto an SDA plate. The
MLCs, read at both 24 and 48 h, were defined as the lowest concentration of
antifungal compound resulting in five or fewer colonies on the SDA plate. The
Paecilomyces quality control strain UTHSC 90-459, which has known values, was
run in conjunction with the test isolates in all antifungal susceptibility testing.
RESULTS
Features of case isolate UTHSC 98-2508. After 10 days of
incubation at 30°C, colonies appeared white to buff with darker
concentric circles on SDA and were a darker gray-brown on
PFA. The reverse of colonies was brownish with centrally
darker areas on SDA and a solid gray-brown on PFA. Basally
inflated phialides (6 to 10 ␮m long by 3.5 to 6 ␮m wide)
occurred along the sides of thin-walled, hyaline-to-pale brown
septate hyphae (1.5 to 3.5 ␮m in diameter) (Fig. 5A) and on
long, unbranched brown echinulate conidiophores (3 to 4 ␮m
wide) that tapered at the tip. The phialides, sometimes prolif-
erating, occurred singly or in pairs and occasionally in whorls
(Fig. 5B). They bore long chains of limoniform-to-fusiform,
one-celled, smooth, hyaline conidia (4.5 to 6.5 ␮m by 2.5 to 3.5
␮m) (Fig. 5C). The echinulate brown conidiophores were pros-
trate on the subhyaline (very slightly pigmented) vegetative
mycelium and were sometimes anchored by a definite basal
hyphal cell (Fig. 5D), and they bore phialides sparingly along
the sides and near the apex (Fig. 5E). Temperature studies on
PFA revealed rapid growth at both 35 and 42°C.
Comparison with other isolates. The isolates identified as A.
fusispora varied in growth rates and colonial features (Table 1).
All grew faster at 37°C (colony diameters, 5 to 8 cm after 7
days) (Table 1) than at 30°C (diameter 3.1 to 5.2 cm). Colonies
of the case isolate (UTHSC 98-2508) (Fig. 6A) and isolates
R2942, R2940, and R2943 were similar in being predominantly
light orange with patches of pale gray on the top side and
yellow to brownish orange, grayish brown, or uniformly brown-
ish black on the reverse (Table 1). The other isolates were
darker gray to brownish gray on the obverse and reverse (Fig.
6B). All produced dark, echinulate conidiophores, but none
displayed the complex whorls of phialides borne at the tips as
is usually depicted for the species (6, 13, 20). More commonly,
FIG. 3. GMS stain of the brain abscess aspirate showing multiple fungal
elements.
FIG. 4. Lung biopsy. (A) Cavitary lesion in the right lobe; (B) hematoxylin
and eosin stain showing necrotizing cavitating pneumonia.
VOL. 38, 2000 BRAIN ABSCESS CAUSED BY ACROPHIALOPHORA FUSISPORA 4571

TABLE 1. Source and features of A. fusispora isolates grouped by conidial ornamentation
UTHSC
a
(UAMH
b
)
accession no. Source Conidium
ornamentation
seen by SEM
c
Conidium appearance observed on slide culture
after 7 days at 37°C Colonial features on PDA after 7 days at 37°C
Size (␮m) Color Colony
diam (cm) Colony color
d
(Top/Reverse)
98-2508 (9508)
f
Human brain; Saudi Arabia;
I. Z. Al-Mohsen (⫽MRN-
435262)
Smooth to very slightly
roughened 4 to 6.5 by 2.5 to 3.5 Hyaline to yellow 6 Pale orange (6A3/4) with pale
grayish patches centrally/light
brownish orange
96-2378 (8781) Human lung nodules and
bronchoalveolar lavage fluid;
California; N. McClenny
(⫽SUH H2976)
Smooth to very slightly
roughened 4 to 6 by 2 to 3 Hyaline to yellow 6.5 Gray (6D1) to brownish gray
(6E2), zonate/brownish black
R-2942 (6731) Soil; Zaire; T. Matsushima
(⫽OS-178) Smooth to slightly
roughened 5 to 6 by 2.5 to 3 Hyaline to yellow 6.1 Pale orange (6A3) to grayish
orange [6B3]/light yellow
R-3122 (9684) Dog, systemic infection
involving brain; Stillwater,
Okla.; R. D. Welsh
(⫽UTMB
e
3307 [reference
29])
Smooth to slightly
roughened 5 to 7 by 2.5 to 4 Hyaline to yellow 8 Brownish gray (6E2) to pale gray/
brownish black
R-2944 (7792) Human corneal ulcer; South
India (⫽CDC B-5574) Fine spirals 4 to 8 by 3.5 to 5 Hyaline to yellow 5 Brownish gray (6E2) with lighter
pale orange (6A3) sector/
brownish black
R-2940 (2889) Soil; Ontario, Canada; G. C.
Bhatt (⫽Barron OAC 10156) Coarse spirals 4 to 8 by 2.5 to 3.5 Pale brown 7.8 Pale orange (6A3) to pale gray,
zonate/grayish brown
R-2941 (4425) Dog, heart and brain tissue;
Oklahoma; J. A. Jackson
(⫽CDC B-3538 ⫽CDC 81-
057308)
Coarse spirals 4 to 6 by 2 to 4 Pale brown 6.5 Gray (6D1) to brownish gray
(6E2), zonate/brown
R-2943 (6967) Human bronchial wash fluid;
Edmonton, Alberta, Canada;
P. Kibsey (⫽MY 1246)
Coarse spirals 5.5 to 9 by 3.5 to 6 Pale brown 6.5 Grayish orange (6B3) darkening to
gray near edge/patchy brownish
orange
a
UTHSC, Department of Pathology, University of Texas Health Science Center at San Antonio.
b
UAMH, Edmonton, University of Alberta Microfungus Collection and Herbarium.
c
SEM, scanning electron microscopy.
d
Color names are from Kornerup and Wanscher (14).
e
UTMB, University of Texas Medical Branch, Galveston.
f
Case isolate.
4572 AL-MOHSEN ET AL. J. CLIN.MICROBIOL.

phialides occurred singly and in pairs along the length of the
conidiophore or on the vegetative hyphae. The brown conid-
iophores were prominant in isolates with darker colonies but
developed in all isolates in older cultures and on media such as
PFA. Sometimes they arose from sclerotium-like structures
(round aggregations of hyphae). Conidial size and ornamen-
tation varied among the isolates (Table 1). Walls were smooth
or very slightly roughened (case isolate, 96-2378 and R-2942
[Fig. 7A]) to finely echinulate (R-2944 [Fig. 7B]) or coarsely
echinulate in spiral bands (R-2940, R-2941, and R-2943 [Fig.
7C]) (Table 1). Conidium dimensions fell within a range of 4 to
9␮m long by 2 to 6 ␮m wide, with R-2943 having the largest
dimensions. The conidia of the case isolate and R-2941 (dog)
were similar in size, but they differed in color and ornamenta-
tion. Our observations were similar to those of Brown and
Smith (4) for both microscopic features and growth habit. They
had noted that isolates grew rapidly within 7 to 10 days but that
by 21 days, colonies rarely reached the edge of the petri dish.
Although some of our isolates did attain diameters of 100 mm
within 15 days at 37°C, the average hourly growth rate after 3
days at 37°C was 0.46 mm/h, compared with 0.38 mm/h after 7
days (0.33 and 0.25 mm/h, respectively, at 30°C).
Antifungal susceptibility. The MICs of AMB against isolates
of A. fusispora ranged between 0.25 and 2.0 ␮g/ml, and the
MLCs ranged from 1.0 to 16 ␮g/ml (Table 2). These concen-
trations are within or above the safely achievable levels in
plasma. Human isolates had lower 48-h MLCs of AMB than
did nonhuman isolates, suggesting cidal activity at generally
achievable drug levels. The isolates were inhibited by relatively
low concentrations of ITRA and MON, but only by relatively
high concentrations of FLU, demonstrating dose-dependent
susceptibility (a term employed to indicate susceptibility of an
organism at escalated doses of the drug). All isolates were
resistant to high concentrations of 5-FC.
DISCUSSION
Other cases. A. fusispora is a thermotolerant fungus with a
wide distribution in tropical and temperate regions. Although
this fungus has been regarded as suspicious for potential
pathogenicity due to its isolation from eye and lung specimens
(Table 1) (23), data have been insufficient to establish etiology.
There is only one confirmed report concerning an eye infec-
tion, in a patient from India, and in that case, the authors were
able to induce keratitis experimentally in rabbits by using the
organism recovered from the patient (22). A. fusispora, origi-
nally placed in the genus Paecilomyces, is seldom described in
medical mycology texts (5, 24), raising the question as to
whether lack of information on this fungus has led to its being
misidentified or overlooked as a potential pathogen. We have
determined that one case published under the name S. char-
tarum involves this fungus. Welsh (personal communication)
described systemic infection with brain involvement in a stray
dog captured in Edmond, Okla. Their isolate is reidentified
here as A. fusispora (UTMB 3307 ⫽UTHSC R-3122 ⫽
UAMH 9684 [Table 1]). Coincidentally, UAMH 4425, ac-
quired in 1981, was isolated from heart and brain tissue of a
dog from Stillwater, Okla. Although no further details are
available concerning the second dog, R. D. Welsh (personal
communication) has confirmed that these are two separate
cases. Ours is the first case of human cerebral infection and
demonstrates that A. fusispora is another dark fungus poten-
tially able to cause brain infection (2, 25). However it should be
noted that isolates of A. fusispora vary in pigmentation and are
not uniformly dark, as demonstrated by our patient’s isolate
(Table 1).
Present case. Our patient demonstrated clinical and radio-
logical response only to combination therapy with high-dose
LAMB and ITRA. The pneumonia in this case was most likely
caused by the same pathogen, which failed to grow due to the
prolonged antifungal therapy prior to the time of the lung
biopsy. Brain abscesses caused by molds can be very difficult to
treat and often have a fatal outcome. The clinical manifesta-
tions (seizures, pneumonia) and risk factors (history of neu-
tropenia and corticosteroids) of CNS Acrophialophora infec-
tion, in this case, are very similar to those of CNS aspergillosis
(28). Hagensee et al. (11) found a 97% mortality rate in a
review of the records of 58 patients with brain abscess follow-
ing bone marrow transplant for treatment of hematologic con-
ditions such as leukemia and aplastic anemia. Fungi, mainly
Aspergillus and Candida species, were isolated in 92% of cases.
AScopulariopsis species was identified as the etiologic agent in
one of these cases. As noted above, the disseminated infection
in the dog was also attributed to a species of Scopulariopsis
(29). Baddley et al. (2), when reporting the dematiaceous as-
comycete Microascus cinereus (anamorph Scopulariopsis)as
the cause of brain abscess in a bone marrow transplant recip-
ient, pointed out that careful examination is required to dis-
criminate the conidial stage from the superficially similar genus
Paecilomyces.
TABLE 2. Antifungal susceptibility data
UTHSC
a
(UAMH
b
)
accession no.
and origin
MLC
f
(␮g/ml)
of AMB
c
at
24 h (48 h)
MIC
e
(␮g/ml) of drug at 24 h (48 h)
g
AMB
c
5-FC
d
FLU
d
ITRA
d
MON
d
98-2508 (9508) human
(case isolate) 1.0 (1.0) 1.0 (1.0) ⬎64 (⬎64) NT 0.125 (0.25) NT
R-2943 (6967) human 1.0 (1.0) 0.5 (1.0) ⬎64 (⬎64) 16 (32) 0.06 (0.125) ⱕ0.03 (ⱕ0.03)
96-2378 (8781) human 1.0 (2.0) 0.5 (1.0) ⬎64 (⬎64) 8 (32) 0.25 (0.25) ⱕ0.03 (ⱕ0.03)
R-2944 (7792) human 1.0 (1.0) 1.0 (1.0) ⬎64 (⬎64) 32 (32) 0.125 (0.125) ⱕ0.03 (ⱕ0.03)
R-2941 (4425) animal 1.0 (16) 0.25 (0.5) ⬎64 (⬎64) 32 (32) 0.125 (0.125) ⱕ0.03 (ⱕ0.03)
R-2942 (6731) soil 2.0 (16) 0.5 (2.0) ⬎64 (⬎64) 16 (64) 0.06 (0.125) ⱕ0.03 (0.06)
R-2940 (2889) soil 2.0 (8) 0.25 (0.25) ⬎64 (⬎64) 16 (32) 0.06 (0.125) ⱕ0.03 (ⱕ0.03)
a
UTHSC, Department of Pathology, University of Texas Health Science Center at San Antonio.
b
UAMH, University of Alberta Microfungus Collection and Herbarium.
c
Tested in antibiotic medium 3, pH 7.0, 35°C.
d
Tested in RPMI-1640, pH 7.0, 35°C.
e
MICs are defined on the basis of the first tube showing no growth (AMB) or the first tube with an 80% reduction in growth (the azoles and 5F-C) compared to
the drug-free control.
f
MLC is defined on the basis of the tube, for which the MIC was lowest, that was plated onto drug-free SPA and yielded five colonies or fewer.
g
Tubes were read after 24 and 48 h of incubation.
VOL. 38, 2000 BRAIN ABSCESS CAUSED BY ACROPHIALOPHORA FUSISPORA 4573

Susceptibility and therapy. Although standardization of an-
tifungal susceptibility testing for filamentous fungi is only com-
mencing (9) and breakpoints for Candida do not apply (19),
some assessment as to an isolate’s in vitro susceptibility can be
inferred by comparing normally achievable concentrations of
the antifungal agents in serum in patients receiving the recom-
mended dosages (10, 21) with the MICs or MLCs for the
isolate. Utilizing this approach showed that all isolates ap-
peared susceptible to ITRA and MON. Isolates also appeared
susceptible to AMB based on MICs (Table 2), except R-2942,
FIG. 5. Microscopic morphology. (A) Basally inflated phialides of case isolate, UTHSC 99-2508, occurring along the sides of thin-walled, hyaline-to-pale brown
septate hyphae (magnification, ⫻306). (B) Proliferating phialides of the case isolate, UTHSC 99-2508 (magnification, ⫻306). (C) Long chains of limoniform-to-
fusiform, one-celled, smooth, hyaline conidia of the case isolate, UTHSC 99-2508 (magnification, ⫻613). (D) Echinulate, brown, prostrate conidiophore of isolate
UTHSC 96-2378, anchored by a definite basal hyphal cell (magnification, ⫻580). (E) Basally inflated phialides of dog isolate R-3122, borne along the sides of brown,
echinulate conidiophores (magnification, ⫻306).
4574 AL-MOHSEN ET AL. J. CLIN.MICROBIOL.

for which the 48-h MIC was 2 ␮g/ml. Curiously, most human
isolates appeared susceptible to AMB based on MLCs, excluding
96-2378, while nonhuman (one animal and two soil) isolates ap-
peared resistant. Although the isolates displayed dose-depen-
dent susceptibility to FLU, this agent is generally less effica-
cious for opportunistic filamentous fungi.
The MIC of AMB for the index isolate was 1.0 ␮g/ml, which
is near the higher range of the maximum safely achievable
peak concentrations of this polyene in plasma. The patient’s
infection progressed despite a high dosage of AMB (1 mg/kg/
day). Thus, the MIC of 1 ␮g/ml in this patient correlates with
a response observed only at the highest dose range of ampho-
tericin. ITRA also may have contributed substantially to treat-
ment of this patient’s infections and was instituted in order to
provide a compound that achieved high concentrations in brain
tissue (10). That the MICs and MLCs of AMB against other
isolates of A. fusispora are relatively high suggests that therapy
in immunocompromised patients may fail despite administra-
tion of conventional AMB or lipid formulation of AMB. The
addition of high-dose ITRA (21) with documentation of ther-
apeutic plasma concentrations above its MIC may have an
important role in management of disseminated infections due
to this new human pathogen.
Taxonomy. The genus Acrophialophora was described by
Edward in 1959 with the type species A. nainiana for a fungus
that was repeatedly recovered from Indian soil during the
warmer months (7). The fungus was considered similar to
Paecilomyces in forming chains of ellipsoidal to fusiform
conidia from basally swollen phialides that were borne either
on conidiophores or directly from the vegetative hyphae. How-
ever, the organism manifested several striking differences that
included (i) unbranched, erect, brown, echinulate conidio-
phores that were fertile only near the apex; (ii) a basal, hyphal
FIG. 6. Colonial morphology after 7 days of incubation on PDA at 37°C. (A)
Colony of the case isolate, UTHSC 99-2508; (B) colony of dog isolate R-3122.
FIG. 7. Electron microscopy. (A) Scanning electron micrograph of smooth-
to-slightly roughened conidia, soil isolate R-2942 (magnification, ⫻10,000). (B)
Scanning electron micrograph of conidia with fine spirals, from human corneal
isolate R-2944 (magnification, ⫻10,000). (C) Scanning electron micrograph of
conidia with coarse spirals, from human bronchial washing isolate R-2943 (mag-
nification, ⫻10,000).
VOL. 38, 2000 BRAIN ABSCESS CAUSED BY ACROPHIALOPHORA FUSISPORA 4575

cell anchoring the conidiophore to the vegetative hyphae,
somewhat like a foot cell in the genus Aspergillus; (iii) a distinct
swelling at the base of the phialides; and (iv) phialides that did
not curve or bend away from the main axis. Barron (3) did not
accept the genus as being different from Paecilomyces, but Ellis
(8) accepted it as distinct and listed A. fusispora as the type
species based on an earlier published name (Paecilomyces fu-
sisporus Saksena 1953). Ellis regarded A. nainiana Edward as a
synonym of A. fusispora; however, he was apparently unaware
of the redescription of Acrophialophora by Samson and Mah-
mood (20) that appeared about the same time. These authors
compared 13 strains mostly isolated from the soil and recog-
nized three species. They were differentiated mainly by conid-
ial ornamentation and the degree of development of brown
conidia but showed overlapping conidial dimensions: A. naini-
ana, with mature conidia that were hyaline and finely echinu-
late (measuring 4 to 10.5 ␮m long and 2 to 5 ␮m wide); A.
fusispora (Saksena) Samson, with mature conidia brown, thick
walled, and with echinulations in spiral bands (measuring 5 to
12 ␮m long and 3 to 6 ␮m wide); and A. levis Samson et T.
Mahmood, with mature conidia smooth to slightly roughened
and hyaline (measuring 4.5 to 8 ␮m long and 2 to 3.5 ␮m wide).
Although the case isolate could fit the description of A. levis
following the species concepts proposed by Samson and Mah-
mood, we take the broader view that A. fusispora includes a
continuum of conidial roughness from smooth to distinctly
spiraled. This broad concept is supported by other common
and overlapping characteristics, including thermotolerance,
growth rates, colonial pigmentation, conidial dimensions, and
in vitro susceptibility data. Although the four human isolates
demonstrated lower MLCs of AMB (Table 2), these same
isolates demonstrated variability in growth rates, colony color,
and conidial wall ornamentation and size (Table 1).
Based on this broad species concept, the case isolate and
other isolates are identified as A. fusispora. Features identify-
ing the species include the following. (i) Isolates are thermo-
tolerant, showing good growth at 42°C or higher. (ii) Colonies
are initially buff or tan, usually becoming grayish brown with an
uncolored or dark grayish brown reverse. Note that colonies of
the case isolate remained lighter colored. (iii) Basally swollen
phialides are borne mostly singly on the vegetative hyphae or
along the length and near the tip of brown, echinulate conid-
iophores. (iv) Limoniform-to-fusiform or ellipsoidal conidia
are borne in long chains and are smooth or finely to coarsely
echinulate, sometimes in spiral bands. (v) Phialides do not
curve away from the main axis. (vi) Phialides sometimes pro-
liferate to form a second opening (Fig. 5B). Phialides produc-
ing more than one opening not delimited by a septum are also
referred to as polyphialides. This recently recognized fungal
pathogen differs from Paecilomyces in having colonies that turn
dark and in forming brown echinulate conidiophores and dif-
fers from Scopulariopsis species in forming conidia from phi-
alides rather than annellides.
As demonstrated by the present case, A. fusispora is capable
of causing a devastating cerebral infection in a human, thus
requiring aggressive antifungal therapy. This fungus has the
potential to be neurotropic, as evidenced by our case and two
cases involving dogs.
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