Anaerobes and Medical Mycology

obligate aerobes

bacteria that only grow in the presence of oxygen (21%)

Ex: pseudomonas, bacillus

facultative

bacteria that can grow in both aerobic and anaerobic conditions

Ex: enterobacterales, staphylococci, streptococci

Microaerophilic

bacteria that are close to being anaerobic; grow in 5% oxygen

Ex: campylobacter

Capnophilic

bacteria that require less oxygen but love growing in carbon dioxide (5-8%)

Ex: strep pneumoniae, neisseria (especially gonorrhoea), haemophilus

obligate anaerobe

bacteria that require very trace amounts of oxygen or no oxygen at all (3%)

good specimen sources for anaerobes

Ex: fluids/aspirates, deep abscesses, biopse, direct lung aspirates

bad specimen sources for anaerobes

Ex: gingival crevices, throat/nasopharyngeal swabs, sputum/BAL, gastric contents, feces/rectal swabs, voided urine, cervical/vaginal swabs, surface of ulcers or wounds

anaerobes

CDC blood agar is non-selective for growth of all _________________

gram-negative facultative

phenylethylalcohol agar inhibits _________________

B. fragilis

bacteroides bile esculin agar selects for

anaerobes (especially acintomyces) and facultative

thioglycolate broth selects for _______________

anaerobes (especially chlostridium)

cooked meat glucose broth

B. fragilis

Reservoir: lower GIT normal flora

infections: bloodstream, wound, abscess, intra-abdominal, appendix, bone

Most common anaerobe isolates

screen with Bile tolerance test

fusobacterium

· Reservoir: oral cavity and lower GIT

· Infections: recurrent tonsillitis, pharyngitis, Lemierre's syndrome, bacteremia

clostridiodes difficile

· Reservoir: lower GIT

· Infections: antibiotic-associated diarrhea; pseudomonas colitis

· Worry more about the toxin than the bug itself

clostridium perfringenes

· Reservoir: marine and terrestrial environment; GIT

· Infections: gas gangrene; gastroenteritis

chlostridium tetani

· Reservoir: soil, dust, manures; vaccine-preventable illness

· Infections: tetanus (rigid paralysis); potential mortality due to asphyxiation

clostridium botulinum

· Reservoir: environment

· Infections: wound botulism, infant botulism, flaccid paralysis, potential mortality due to diaphragm deficit covert bioterrorism

· Don’t give babies unpasteurized honey

B. fragilis, fusobacterium

gram negative anaerobes

Clostridioides, clostridium

gram positive anaerobes

chronic

fungal infections are generally more __________ than accute

iatrogenic

most fungal infections are ______________ and generally involve a predisposition that suppresses the immune system

signal disease

Candida albicans, Cryptococcus neoformans, and Pneumocystis jirovecii infections can be a _________________________ for an immune deficiency

25C

ideal growth temperature for mold

37C

ideal growth temperature for yeast

mold

appear to have more textures and pigments; identify with observation

yeast

appear creamy and glabrous; identify with biochemical tests

hyphae

basic unit (single cell) of molds

blastoconidium

basic unit (single cell) of yeast

4 weeks

test time for mold: report negative at _____________

overnight

test time for yeast

non-selective

sabourad dextrose agar

opportunists

Chloramphenicol and cycloheximide selective media inhibit ___________

mycobaiotic agar

Sabouraud dextrose with antibiotics - chloramphenicol + cycloheximide

2

pathogenic molds take _____ or more weeks to grow

mycobiotic

Nastier the mold = longer it takes to grow and more likely to grow on ___________ agar

mannoproteins

fungal protein that is located on the surface of the cell wall

B-glucans

polysaccharide in fungal outer membrane between chitin and mannoproteins

chitin

provides both toughness and flexibility in the fungal outer membrane

opportunists

hyaline molds, mucormyctes, and yeasts are subdivisions of ___________

aspergillosis

must come from nasoorbital, endocardial, cutaneous, disseminated, CNS, or pulmonary pathologies

aspergillus fumigatus

· Maturity ~3 days

· Colony surface becomes dark greenish to gray; reverse white to tan; inhibited by cycloheximide

· Composed of stalk (forearm), vesicle (fist) and phialides (hair)

· Conidiophores short and smooth

· Phialides on upper 2/3 of vesicle --> mohawk haircut

aspergillus flavus

· Commonly associated with aflatoxins

· Colony surface velvety, yellow to green or brown; reverse white to tan; inhibited by cycloheximide

· Conidiophores rough and spiny

· Phialides covering entire vesicle (all directions) --> afro haircut

Fusarium

· Common contaminant: mycotic keratitis (#1), disseminated disease

· Maturity in about 4 days (quick grower)

· Cottony surface, develops violet or pink center with light periphery; reverse light; inhibited by cycloheximide

· Canoe-shaped macroconidia ± 1 to 2-celled conidia in clusters

Mucor

· Common contaminant

· Lid lifters

· Maturity in about 4 days; growth inhibited by cycloheximide

o Rapid growers

· Cottony or moist surface, becomes grey; reverse white

· Rhizoids absent

haircut: Don King the boxing promotor

mucormycosis

· Diabetic susceptibility and high mortality rate

· Orbital mucor myotic infections

Rhizopus

· Common contaminants

· Maturity in about 4 days; growth inhibited by cycloheximide

· Cotton candy – white at first, then grey or yellowish brown; reverse white

· Rhizoids are opposite of sporangiophores

Candida albicans

· Normal flora (small numbers) in skin, vagina, oral cavity, and intestine

· Finger-like or star-like projections on blood agar

· Most common species isolated from all forms of candidiasis

· Contiguous germ tube formed from incubation of colony in serum

· Distinctive morphology on chromogenic medium

· Terminal chlamydocondia, especially at 25C

c. albicans

causes thrush, vaginitis, onychomycosis, skin infection, and fungemia - immunocompromised patients, those with indwelling catheters, those on broad-spectrum antibacterial are most susceptible

candida glabrata

· Potential induction of fluconazole resistance upon suboptimal treatment

· colony forming units on eosin methylene blue agar are larger

· Small blastocondida; may bud at 11:00 and 1:00 (mickey mouse)

· “distinctive” morphology on chromogenic medium

· Rapid trehalose testive gives presumptive ID within 3 hours

c. glabrata

causes endocarditis, meningitis, multifocal disease, and makes up 20% of candida UTIs

cryptococcus neoformans

· Signal disease for HIV or Kaposi sarcoma

· Tinkertoy structure

pneumocystis jiovecii

· Serology, nucleic acid detection not useful

· Cyst wall, intracystic body stains

pathogenic

dimorphs and dermatophytes are subdivisions of _____________ molds

dimorphs

-have two growth phases (mold and yeast)

-geographic distribution helps with diagnosis

-produce multi-focal clinical disease (most respiratory, some cutaneous, CNS, bone, reticuloendothelial)

-morphology mimics non-pathogenic fungi so extra measures must be taken to conform

mold, yeast

to identify dimorphs, convert __________ to ________ by subculturing in blood media at 37C

opportunistic

Aspergillus, Fusarium, Mucor, Rhizopus, Candida, Cryptococcus, and Pmeumocystis are ______________ molds

pathogenic

Histoplasma, Blastomyces, Coccidiodes, and Dermatophytes are ______________ molds

dimorph

Histoplasma, Blastomyces, and Coccidioides are examples of ______________ pathogenic molds

histoplasma capsulatum

· soil with starling, bat guano; inhalation

· Tuberculate macroconidia

· small, budding yeast; loves macrophages

· Bob Dylan

· Breathe in as mold --> turns into yeast

histoplasmosis (Darling's Disease)

subacute self-limited respiratory illness (like TB); disseminates to liver, spleen, and brain

Darling's disease

Histoplasmosis

Blastomyces dermatitidis

· Soil (alkalinity, moisture, organic matter); inhalation

· Lollipop (single) conidia, at top of conidiophores

· Big, broad -based buds of Blasto

Blastomycosis (Gilchrist's Disease)

o 50% asymptomatic, self-limiting

o Lower respiratory disease

o Disseminate to skin, bone, prostate

Gilchrist's Disease

Blastomycosis

coccidiodes immitis

· Hot, dry, alkaline soil; wind, construction; inhalation

· Barrel-shaped, alternate arthroconidia

o May grow quicker than other dimorphs

· No yeast form; spherule in vivo

coccidioidomycosis (Valley Fever)

o 60% asymptomatic, self-limiting

o Lower respiratory disease

o Rate dissemination to skin, bone, joints (Filipino, African, Asian, Mexican)

o CNS in AIDS patients (#3; devastating)

Valley Fever

Coccidioidomycosis

dermatophytes

· Infrequent mortality

· Tinea (ringworm)

· Immunocompromised host not required (anyone can get athletes foot or jock itch)

· #1 infectious disease

trichophyton

causes tinea capitis, and tinea pedis

trichophyton rubrum

#1 dermatophyte in humans