Download Corneal Ulcer Due to Exserohilum longirostratum

CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASE
Case Report
Corneal Ulcer Due to Exserohilum
longirostratum
CHERIE L. BOUCHON, MT(ASCP)SM/ DONALD L. GREER, P H D , 2
AND CHARLES F. GENRE, MD 3
A 47-year-old man sustained a traumatic injury to the left eye, and a
corneal ulcer subsequently developed. Histologic examination of the
corneal tissue revealed septate hyphae with acute angle branching. The
mycologic and bacterial cultures yielded a dematiaceous fungus with
ellipsoidal pigmented macroconidia borne sympodially on geniculate
conidiophores. The multicellular macroconidia had prominent, protruding, truncated hila. The shorter macroconidia averaged 5-7 septa,
and the longer conidia 13-21 septa. Growth on V-8 agar, alternating
between fluorescent light and the dark, produced macroconidia more
than 200 pm in length. The isolate was identified as Exserohilum longirostratum. This is believed to be the first documented case of mycotic
keratitis caused by the phaeohyphomycete E longirostratum. (Key
words: Exserohilum; Mycotic keratitis; Phaeohyphomycosis) Am J
Clin Pathol 1994;101:452-455.
In our environment are many dematiaceous (pigmented)
fungi, which can cause a variety of infections in humans. At
present, there are more than 63 species of dematiaceous fungi
known to cause disease in humans and animals. 1 These infections, called phaeohyphomycoses, are characterized by the presence of pigmented hyphae, pseudohyphae, and yeast-like cells
in tissue. Phaeohyphomycosis occurs in both healthy and immunocompromised hosts and may present clinically as cutaneous, subcutaneous, or systemic disease.
Among this group of "black" molds are the genera Bipolaris,
Drechslera, Exserohilum, and Helminthosporium. In the past,
several cases of human phaeohyphomycosis have been attributed to species of the genera Drechslera2'9 and Helminthosporium. 10~13 After reviewing these cases, McGinnis and colleagues'
concluded that the true pathogenic species were actually of the
genera Bipolaris and Exserohilum. Only species contained in
these genera represented well-documented cases of phaeohyphomycosis.
Many reports have documented mycotic keratitis caused by
the species Drechslera3, '•' and Helminthosporium.10'1213 These
isolates have since been reclassified as either Bipolaris or Exserohilum species.1,14 In a recent review of these agents in neutropenic patients, Douer and colleagues15 did not identify a
single case caused by E longirostratum. We describe here the
first documented case of human phaeohyphomycotic keratitis
caused by E longirostratum.
CASE REPORT
A 47-year-old man, a native of Honduras, came to the Ochsner
Clinic, New Orleans, Louisiana, on July 1 with a referral diagnosis of a
perforated left corneal ulcer. The illness began in April, when the patient was on a train and was struck in the left eye by an unknown
foreign object that entered through an open window. The patient was
seen by physicians in Honduras and treated with antibacterial agents.
Because of a slow, progressive illness, he was told that a corneal transplant was needed, but corneal tissue was unavailable. The patient was
referred to the Ochsner Clinic for possible corneal transplant.
When seen in the outpatient clinic in July, the patient had a normal
right eye. The left eye showed a 3 x 3 mL central corneal defect. The
conjunctiva was severely inflamed, and microcystic changes were
noted on the corneal epithelium surrounding the ulcer. More than 75%
of the anterior chamber was filled with a dense hypopyon. The remainder of the anterior chamber contained fibrin and numerous inflammatory cells. The initial diagnosis was mycotic keratitis, approximately 3 months old. In addition, severe uveitis and possible
endophthalmitis were noted. At this time, corneal scrapings were sent
to the microbiology laboratory for culture.
The patient was treated with topical antibiotics and oral ketoconazole and placed on treatment to lower intraocular pressure. After 3 days
of therapy, the anterior chamber filtrate increased, and intraocular
From the Departments of 'Microbiology and ^Pathology, Alton pressure began to rise. On July 4, a corneal graft and anterior chamber
Ochsner Medical Foundation, Jefferson, Louisiana; and ''•Departmentdebridement was performed. Numerous cultures of both areas were
of Dermatology, Louisiana State University Medical Center, New Or- taken. Frozen section of the native cornea showed branching hyphal
leans, Louisiana.
elements thought to be consistent with a zygomycete. Because of nonviability of the eye and the high mortality rate of zygomycosis, the best
Manuscript received October 20, 1992; revision accepted June 24,
course of action was determined to be enucleation. An extensive exami1993.
nation at the time of surgery revealed no sinus or extraorbital involveAddress reprint requests to Ms. Bouchon: Department of Microbiolment. As a result, systemic antifungal chemotherapy was not initiated.
ogy, Alton Ochsner Medical Foundation, 1516 Jefferson Highway, Jefferson, LA 70121.
The patient's postoperative course was uneventful and he recovered
452
BOUCHON, GREER, AND GENRE
Corneal Ulcer Due
453
E longirostratum
acid-SchifF and Gomori-Grocott methenamine silver. All tissue slides were read and interpreted by the anatomic pathologist.
RESULTS
Direct
Examination
The gram stain of the corneal scrapings, the corneal tissue
obtained during surgery, and the exudate from the anterior
chamber showed only rare polymorphonuclear leukocytes. No
microorganisms were observed.
Histologic
Findings
Tissue sections of the cornea stained with hematoxylin and
eosin revealed focally compressed and necrotic stroma. The
epithelium was effaced, and Bowman's membrane could not
be identified. The periodic acid-Schiff stain revealed fungal hyphae in the necrotic zones. These elements appeared broad,
septate, and pleomorphic with acute angle branching, but pigment was not visible in their walls (Fig. 1).
FIG. 1. Tissue section of eye showing period acid-Schiff positive, pleomorphic hyphal elements compatible with phaeohyphomycosis
(X400).
well. The patient was placed on topical therapy and returned to Honduras to be followed by ophthalmology services there.
Microbiologic
Findings
Two colonies of a dematiaceous fungus grew on the blood
agar from the corneal scrapings taken in the ophthalmology
clinic. No growth occurred on the chocolate agar.
All cultures of the anterior chamber exudate and the corneal
tissue obtained from surgery were negative for all organisms.
The plates were held for 7 days.
MATERIALS A N D METHODS
Materials
On admission from the outpatient clinic, the infected cornea
was scraped, and fragments were inoculated onto trypticase soy
agar plates containing 5% rabbit blood and chocolate agar (Becton-Dickinson Microbiology System, Cockeysville, MD).
These routine cultures were processed in the general bacteriology laboratory. In addition, a Sabouraud's dextrose agar plate
containing only .5 mg/mL of chloramphenicol (Becton-Dickinson Microbiology System, Cockeysville, MD) was inoculated
and incubated in the mycology laboratory.
At the time of surgery, corneal tissue debris and anterior
chamber exudate were plated on agar plates as above and cultured for bacteria and fungi. Fragments of corneal tissue were
also placed in formalin and submitted for histologic examinations.
Methods
All routine cultures for bacteria were incubated at 37 °C in
5% to 10% carbon dioxide for 7 days. The Sabouraud's dextrose
media for fungi was incubated at 25 °C in the dark and held for
30 days. Fungal growth from both bacterial and fungal media
was identified by their morphologic features using standard
laboratory procedures. Speciation of the dematiacious mold
isolated was according to McGinnis and colleagues.1
Surgical specimens were routinely stained with hematoxylin
and eosin. Special stains for fungal structures included periodic
Vol. 101
FIG. 2. Cylindro-ellipsoidal macroconidia with 5-8 septa produced on
V-8 Agar. Note protruding hila and darkly pigmented basal and distal
septa (XI60).
No. 4
454
CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASE
Case Report
TABLE 1. CHARACTERISTICS OF PRESENT ISOLATE COMPARED WITH THOSE OF
BIPOLARIS, DRECHSLERA, AND EXSEROHILUM
Conidia
Reported
as Pathogen
Cortidiation
Average
Size
(lim)
+
Profuse
8X26
Poor
Bipolaris
Drechslera
Germ lubes
No.
of Septa
Hilum
Origin
3-5
Protrudes slightly
16X65
3-5
Does not protrude
One or both end cells,
adjacent to hilum
Intermediate and end
cells, not adjacent to
hilum
One or both end cells,
adjacent to hilum;
often other cells
One or both end cells,
adjacent to hilum,
often other cells
Exserohilum
+
Profuse
14 X90
5-12
Protrudes strongly
Present
+
Profuse
14X90
5-12
Protrudes strongly
Orientation from
Basal Cell
Along axis of conidium
Perpendicular to conidial
axis
Along axis of conidium
Along axis of conidium
Modified from Larone.16
On Sabouraud's dextrose agar, colonies of a dematiaceous,
woolly mold grew in 5 days from all fragments of the corneal
scrapings received from the outpatient clinic. No growth occurred on either Sabouraud's dextrose agar or Mycosel from
either surgical specimen (corneal tissue or anterior chamber
exudate). These cultures were held for 30 days.
A cellophane tape preparation mounted in lactophenol cotton blue was made of the fungus from the original corneal
scrapings. The preparation revealed a pigmented, filamentous
mold with cylindrical macroconidia compatible with a species
of Drechslera. For further identification, slide cultures were
prepared on potato dextrose and 15% V-8 juice agar.1 After 1
FIG. 3. Elongated macroconidia seen on V-8 Agar cultures exposed to
intermittent fluorescent light. Length varied from 196-260 iim (X64).
week incubation at room temperature (25-28 °C), both cultures produced abundant macroconidia. On V-8 juice agar,
brown pigmented, septate hyphae were produced on geniculate
conidiophores with cylindro-ellipsoidal macroconidia. The
conidia had strongly protruding truncate hila. The shorter conidia averaged 5-9 septa. The basal and distal septa were darkly
pigmented, and occasional warty projections were observed
(Fig. 2). These findings identified the isolate as a species of
Exserohilum (Table 1).
Additional duplicate cultures on V-8 agar were incubated at
25 °C totally in the dark and at 25 °C with periodic exposure to
fluorescent light.1 Cultures that had been exposed to intermittent fluorescent light produced unusually long, thin, rostrate
macroconidia, 196-260 nm in length, with 13-21 septations
(Fig. 3). These studies suggested that the isolate was E longirostratum (Table 2).
Germination was studied by emulsifying a teased portion of
the fungal growth in sterile water and allowing the suspension
to incubate at 25 °C for 24 hours.' After incubation, germ tube
formation was observed in direct wet preparations. Macroconidia produced germ tubes from the ends of the conidia along the
conidial axis. The germ tube arose adjacent to the hilum of the
basal cells and displaced it to one side. Based on our results and
the reports by McGinnis and colleagues,1 the isolate was identified as E longiroslratum.
DISCUSSION
Mycotic keratitis is an opportunistic infection that usually
follows trauma to the cornea. The present case illustrates that a
previously unreported, usually saprophytic dematiaceous fungal species could cause a serious infection in an otherwise
healthy host after trauma to the cornea. The only microorganism isolated from the specimens was the dematiaceous fungus
E longiroslratum.
Tissue sections stained with hematoxylin and eosin showed
an acute infectious process. The mycotic infection was confirmed further by the observation of septate, branching hyphae
in the native cornea. The failure to recover the fungal agent
from the surgical specimens is unexplained. The small amount
of specimen received may not have contained any viable fungal
elements, or perhaps the topical antibiotics given before surgery inhibited the growth of the fungus in culture.
AJ.C.P. • April 1994
455
BOUCHON, GREER, AND GENRE
Corneal Ulcer Due to E longirostratum
TABLE 2. CHARACTERISTICS OF THE MATURE CONIDIA OF PRESENT ISOLATE COMPARED
WITH THOSE OF OTHER SPECIES OF EXSEROHILUM
Anamorph
Shape
Septation
Size (urn)
9-11
13X83
7-9
15X73
E longirostratum
Straight, curved, or slightly bent; ellipsoidal;
strongly protruding, truncate hilum; walls
with irregular warty projections
Same as E mcginnisii except rostrate,
septum above hilum thickened and dark,
walls often finely roughened
Same as E rosiratum
Present
Same as E longirostratum
E mcginnisii
E rosiratum
Long conidia, 13-21; short
conidia, 5-9
Long conidia, 12-19; short
conidia, 5-9
Long conidia, 196-260; short
conidia, 16x61
Long conidia, 192-260; short
conidia, 16X61
Modified from McGinnis1.
An increase in phaeohyphomycotic infections has been observed in recent years. This increase is due partly to the heightened awareness of the dematiaceous fungi as agents of infection, and partly to an increase in the population of
immunocompromised patients. At the Alton Ochsner Medical
Foundation, we have observed that solid organ transplant patients are particularly vulnerable to infections caused by this
group of fungi.
Recently, the taxonomy and nomenclature of this large
group of fungi have been clarified.1,17"'9 Specific identification
of these fungi becomes vital, because they play a large role as
infectious agents in both hospitalized patients and healthy persons. The clinician must be aware of the invasive capabilities of
these fungi. This growing knowledge will aid in a more rapid
diagnosis and initiation of appropriate therapy.
6. McAleer R, Kroenert DB, Elder J L, Froudist JH. Allergic bronchopulmonary disease caused by Curvularia lunata and Drechslera
hawaiiensis. Thorax 1981;36:338-344.
7. Rolston K.VI, Hopfer RL, Larson DL. Infections caused by
Drechslera species: Case report and review of the literature. Rev
Infect Dis 1985;7:525-529.
8. Yoshimori RN, Moore RA, Itabashi HH, Fijikawa DG. Phaeohyphomycosis of brain: Granulomatous encephalitis caused by
Drechslera spicifera. Am J Clin Pathol 1982;77:363-370.
9. Zapater RC, Albesi EJ, Garcia GH. Mycotic keratitis by Drechslera spicifera. Sabouraudia 1975;13:295-298.
10. Chin GN. Corneal perforation due to Helminthosporium and
Mima polymorpha. Ann Opthalmol 1978; 10:607-609.
11. Dolan CT, Weed LA, Dines DE. Bronchopulmonary Helminthosporiosis. Am J Clin Pathol 1970;53:235-242.
12. Harris R, Smith RE, Wood TR, Biddle M. Helminthosporium corneal ulcers. Ann Opthalmol 1978; 10:729-733.
13. Krachmer JH, Anderson RL, Binder PS, Waring GO, Rousey JJ,
Acknowledgment. The authors thank Dr. G. W. Willis, Department
Meeks ES. Helminthosporium corneal ulcers. Am J Opthalmol
of Pathology, Alton Ochsner Medical Foundation, for the photographs
1978;85:666-670.
in Figures 1-3.
14. Adam RD, Paquin ML, Petersen EA, et al. Phaeophyphomycosis
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