Micro exam 8

Bacillus anthracis

spore forming, G+ rod, boxcar appearance, Spores in culture and soil, viable for decades --> easy to grow too. Spores not seen in clinical samples. polypeptide (poly-D-glutamic acid) capsule seen in clinical samples. 3 proteins that form 2 toxins = PA + (


Bacillus anthracis. 95% cutaneous, enter through cut in skin, inoculation site reddens, small papule blisters and ulcerates = blackened nectroic lesion (eschar) - painless but may have swelling of adjacent lymph nodes and edema. inhalation (bioterrorism c

Brucella spp.
B. abortus (cattle)
B. melitensis (goats, sheep)
B. suis (pigs)]

G(-) coccobacillus, intracellular pathogen that reside in acidified phagolysosomes of macrophages/monocytes, therefore Cell mediated immunity (INF-g) is essential for resolution. Has endotoxin -- varies in virulence. Causes Brucellosis


Caused by Brucella spp. risk = slaughter house workers, butchers, veterinarians, farmers, ranchers - occupational disease. B. abortus most common in CA, FL, TX, VA. B. melitensis endemic in Mediterranean, Latin America, Middle East usually through contami

Yersinia pestis

Causes plague. G(-) intracellular rod, Enterobacteriaceae family. Giemsa stain shows "closed safety pin" appearance (blue instead of red also). 3 pasmids that encode proteins that facilitate regurgitation of bacteria by fleas, enhance survival in macropha


Caused by Yersinia pestis.
Transmitted by: rodents through fleas, bites and scratches of cats that have killed infected rodent, or inhalation of aerosol during skinning/cleaning infected rodent
NM, AZ, CA, CO, NV, WY due to prarie dogs
Bubonic plague: pai

Pasteurella multocida

Causes Pasteurelloses. G(-) coccobacilli, normal flora in nasopharynx of many domestic and wild animals (dogs, cats). bite wound begins to redden and swell, becomes painful, may have cellulitis, abscess formation and regional lymphadenopathy. Increased ri

Burkholderia pseudomallei causes

G(-) rod found in surface waters and soil -- rice farmers in Asia, wounds/abrasions on body. single/multiple tender nodules/abscess with lymphadenopathy. True zoonnoses at question.

Leptospira interrogans

Causes Leptospirosis. G(-) spiral shaped with hooks, obligate anaerobes, dark microscopy. Found in tropic waters contaminated w/ infected urine -- most infections are recreational (swimmers) or occupational (veterinarians). Invade abraded skin and intact

Borrelia burgdorferi causes
Lyme Diseasee

G(-) spirochete, leading vector-borne disease in US. Ixodes scapularis and Ixodes pacificus are major vectors. Fever, HA, joint aches/pains, bull's eye rash typical for acute infection. Chronic is more serious and can develop blue color over joint areas

Borrelia recurrentis causes
Relapsing fever

Poorly Giemsa staining in blood smears, G(-) spirochetes, difficult to grow. Antigentic variation -- fever, chills, headache, muscle aches, splenomegaly, hepatomegaly, lasts 3-7 days, resolves but reappears after another week results from increasing numbe

RICKETTSIA organisms

G(-) coccobacilli, obligate intracellular pathogens, grow in cytoplasm. Transmitted by arthropod vector, reservoir can be human or animal
Most infected develop clinical disease.
Infect vascular endothelium of small blood vessels
In skin - inflammation, en

Rocky Mountain Spotted Fever caused by
Rickettsia rickettsii

Difficult to grow in lab. Found in S. Atlantic region (Delaware to Florida), thru tickbites. Rash develops on wrists, forearms, ankles and progresses to torso

Rickettsial Pox caused by
Rickettsia akari

Transmitted by bite of mites that feed on infected rodents, including house mouse. Develop painless papule at site of inocluation that becomes ulcerated, scabs over (eschar). 2nd phase: pox-like eruptions 1-3 weeks later

Epidemic typhus caused by
Rickettsia prowazekii

Associated with war, poverty, human tragedy, crowded conditions, Central Africa, S. and Central America. Transmitted by body lice -- innoculation through scratching. Very high fever (104F), conjunctivitis, severe headache, myalgia, arthralgia. Rash progre

Endemic (Murine) Typhus caused by
Rickettsia typhi

Not many US cases, most Gulf Coast of TX. Transmitted by rat flea. Symptoms resemble epidemic typhus

Scrub Typhus (aka Tsutsugamushi Fever)
Orientia tsutsugamushi

Still in Rickettsia Family. Endemic in SE Asia, Pacific Islands, N. Australia. Transmission through bit of infected mide that feeds on rodents, lagomorphs and marsupials. Symptoms resemble epidemic typhus

Human Monocytic Ehrlichiosis (HME) &
Human Granulocytic Ehrlichiosis (HGE)

HME - Ehrlichia chaffeensis. SE, Mid-Atlantic, Midwest, S Central US - lone star tick, white tailed deer. Invades monocytes, macrophages, others.
HGE - Anaplasma phagocytophilium. N Central Midwest, NE, Central Atlantic US - Ixodes ticks, small mammals. I

Coxiella Burnetii causes
Q (Query) Fever

G(-) pleomorphic intracellular. Replication starts when phagocytic vesicles w/organisms fuses with lysosomes and become acidified
Small-cell develops into large-cell that divides to small-cell/forms endospores
Inhalation of endospores or consumption of un

Bartonella spp.
1) Trench Fever - B. quintana
2) Cat Scratch Fever - B. henselae
3) Bacillary Angiomatosis - both

Small, slightly curved, G(-), can reside in erythrocytes.
1) relapsing fever and shin pain, transmitted by body louse, associated with poverty, lack of hygiene, overcrowding (homeless)
2) fairly common, massive lymphadenopathy, usually children/adolescent

Staph aureus

Gram +, facultative anaerobe, form grape-like clusters, ?-hemolytic
Protein A inhibits clearance by binding to IgG Fc.
Alpha toxin forms pores in various cell types
Exfoliative toxins (ETA/ETB) split intraepidermal junctions causing skin lesions (eg. SSS

Suppurative cutaneous infections cause by S. aureus:
1) Bullous impetigo
2) Ecyhyma
3) Furuncle/Boil
4) Carbuncle
5) Folliculitis

1) Blisters are initially filled with cloudy fluid and later rupture, resulting in erosions and crusting caused by the production of exfoliative toxin.
2) slightly deeper form of impetigo with resultant scarring and ulceration. Causes punched-out ulcerati

more Staph aureus infections:
1) Staphylococcal scalded skin syndrome (SSSS)
3) Osteomyelitis
4) Septic arthritis

1) usually neonates, starts clinically inapparent infection of conjunctiva nasopharynx or ubilicus; high recovery w/o scarring; can't culture from skin (toxin mediated); no leukocytes either. Phase 1 = initial (local erythroderma) Phase 2 = exfoliative (s

Streptococcus. pyogenes (Group A Strep -- GAS)

G+ cocci in chains/pairs, B-hemolytic; Lancefield antigens separate into groups, Bacitracin sensitive; respiratory droplet transmission --> pharyngitis; breaks in skin --> SSTI; can have transient colonization briefly. Hyaluronic Acid Capsule, Adhesins (F

S. pyogenes GAS infections
1) Impetigo (Pyodermal)
2) Glomerulonephritis
3) Streptococcal TSS
4) Ecthyma

1) mainly seen in young children in warmer months, lesions break down, coalesce and form honeycomb-like crusts; hard to differentiate from S. aureus so may use Oxacillin or vanco in addition to PCN. Bullous impetigo (S. aureus) distinguished by more exten

Necrotizing fasciitis

much more painful than cellulitis, but doesn't look as bad
S. pyogenes > C. perfringens, mixed anaerobes, S. aureus
Tx: aggressive surgical debridement and intensive support therapy

Cellulitis (and Erysipelas)

Extend depper into skin than impetigo and ecthyma, leads to acute inflammation
Cellulitis -- heat, erythema (redness), swelling, tenderness, usually face and extremities. Borders blend in with surrounding tissues in cellulitis
GAS > Staph Aureus, Pasteure

Pseudomonas aeruginosa

G- rod, oxidase +, produces blue/green pyocanin pigment on blood agar (and in tissue), minimalist, wide temp range, usually nosocomial/opportunistic, Exotoxin A is AB toxin -- blocks protein synthesis, neutropenia predisposes bc PMNs are crucial to fighti

Pseudomonas aeruginosa infections:
1) Burn Wounds
2) Folliculitis
3) Osteochondritis
4) Bacteremia/sepsis
5) Green Nails
6) Webspace Intertrigo

1) often colonizes burn victims
2) usually from hot tub
3) usually after penetrating injury
4) secondary to skin infection; can lead to blood vessel infection resulting in skin lesions -- ecthyma gangrenosum
5) paronychia; biofilm on ventral/dorsal surfac


Between nail and cuticle.
Acute: Staph aureus most common
Chronic (>6wks): usually Candida albicans


Anaerobic G+ spore formers, ubiquitous, commensal, usually toxin mediated disease -- alpha-toxin. Can cause: cellulitis, fasciitis, suppurative myositis, Gas gangrene (myonecrosis) --> H and CO gas produced, and also food poisoning, necrotizing enteritis,


acid fast, lipid rich cell membrane, thick waxy wall - hard to disinfect and Tx, slowly developing, no toxins, slow growing light-colored colonoies grown on Lowenstein-Jensen or Middlebrooks media.

Skeletal tuberculosis (aka Pott's disease)

M. tuberculosis - disseminates from lung to bone, "gibbus" back deformity, visualized in aspirate or Bx - usually granulomas also, +PPD test, Tx is 6-9 mos due to waxy wall, Isoniazid & Rifampin = First Line, vaccine (attenuated M.bovis) not useful in adu


M. leprae - armadillo reservoir, Bx shows organism, can't grow culture, two response types: 1) Th1 = Tuberculoid Leprosy - cell mediated response, kills many of the bacterium (paucibacillary) 2) Th2 = Lepromatous Hansen's Disease - humoral (AB) response,


Filamentous branched bacteria, look like hyphae - mistaken for fungi, G+ rod (bead-like appearance), weakly acid fast, aerial hyphae protrude upward
cutaneous infections - mycetoma: minor injury (usually foot) causes slowly progressing, painless lesions a

Actinomycosis (israellii)

Filamentous branched bacteria, look like hyphae - mistaken for fungi, G+ rod. Culture looks like molar tooth, already present in mucous linings (GI, GU, URT, mouth --> dental work, or poor dental hygiene), abscesses contain sulfur granules (looks like gra

Acne vulgaris

Papules, pustules, nodules on face, chest, back, pilosebaceous unit infection.
Propionibacteriunm acnes is organism: G+ rod, endogenous flora, inflammatory response causes pathology, commensal

Gingivitis (just gingival tissues -- reversible) and
periodontitis (soft tissue and bone -- not)

1/3 of adults have periodontal disease, can lead to carditis, plaque of bacteria secrete toxins
Streptococcus mutans - forms dental caries (cavities) due to acid byproducts (no AG associated to make it a group blank strep)


intracellular in macrophages, vector = sandfly. self-limiting thru cell-mediated immunity. can be disfiguring/debilitating from scaring
Cutaneous disease (L. major, L. tropica, L. mexicana) = raised dry, crusty lesion at site of parasite inoculation. slow

Onchocerca volvulus causes
River Blindness

vector = black fly (breed near fast-moving rivers), subcutaneous nodule w/ microfilaria (nematode larvae) at inoculation site which may disseminate over many years, often to the eye -- immune response causes over-inflammation and blindness. almost solely

Mansonella spp.
streptocerca - Africa
perstans - widespread
ozzardi - central/south america, caribbean

filarial nematode, vector = midge, usually asymptomatic (many infected) but can cause itching, edema, joint pain. Dx: microfilaria on stained blood smear or skin snips.

Dracunculosis - Dracunculus medinensis

largest tissue dwelling nematode (2-3 ft), females lay eggs in lower extremity causing blisters which burst in water then others drink that water and are infected. clean drinking water has lowered incidence dramatically. Tx: wind worm out over time (so yo

Cutaneous larva migrans (aka creeping eruptions) caused by dog/cat Ancylostoma (hookworms)

Larvae penetrate skin of accidental host and burrow deep into epidermis resulting intense inflammatory reaction after exposure to infected dog/cat urine/feces

Scabies (sarcoptes scabiei)

Infestation in superficial dermatitis. Mites lay eggs deep into skin, usually around finger web space, elbows, skin fold areas, etc. rash can occur (allergic response) esp. if much exposure. Presents as severe itching. easily spread, need to Tx household

Lice (Pediculosis)
1) Pediculus humanus (body louse)
2) P. humanus capitis (head louse)
3) Phthirus pubis (crab louse)

obligate blood-feeding ectoparasites, wingless 6-legged, flat insects. Intense itching occurs. Pruritic, reddneed papules
1) body lice tend to live on clothing of infected also, easily spreads (eg. closets)
2) stay close to head, eggs (nits) in hair
3) se

Human Botfly (Myiasis) infection

S. or Central America. Larvae (maggots) of flies, transmitted by arthropod, develop in subcutaneous tissue then fall out. foul smelling exudate present. can force them out or put vasoline on to suffocate them.

Chagas Disease (Trypanosoma cruzi)

Protozoa, redivid bug, intracellular, can infect cardiac tissue and years later have damage

Trchinellosis (Trichinella spiralis)

Helminth that infects muscle cells, depending on which muscle it infects dictates the disease. Encysted larvae in undercooked wild pork, bear, horse, boar etc. penetrate GI (cramping, diarrhea) and go to muscle causing edema, pain, etc. fever, chills, EOS

Eye Worm aka Loiasis (Loa loa)

Helminth. Africa. Mango fly bite. Adults in subQ tissue, microfilariae in bloodstream --> diagnostic, 15 cm edematous swelling at site of infection = "Calabar swelling". often migrate to eye. Rare occurance. EOSINOPHILIA

Lung Fluke (Paragonimus westermani)

Helminth. Transmitted by snails in water to freshwater crabs or crayfish, penetrate tissue and spread to lungs EOSINOPHILIA. 1% of Asian immigrants infected. Bloody sputum, lung abscess, eggs in sputum (makes it look brown/rust-colored).

Cysticercosis (Taenia solium)

Helminth. Pork tapeworm. Neurocystircercosis if eggs (in feces) ingested

Hydatid Cyst (Echinococcus granulosus)

Helminth. Dog tapeworm. Hydatid cyst in brain, liver, elsewhere after ingesting eggs.

Superficial Mycoses

limited to outermost skin (stratum corneum) and hair (cuticle) so more like colonization. No inflammatory reaction. More of a cosmetic concern

Pityriasis Versicolor (Tinea Versicolor)

Malassezia furfur, dimorphic, normal flora, lipophilic -- sebaceous glands (head, trunk, upper back) will cause hyphal phase and disease. more often in warmer climates. yellow-brown to dark brown color (hyper or hypo pigmentation and failure to tan)

Tinea Nigra

Exophiala werneckii, oval light-brown to black pigmented yeast colonies (hyphae mold in environment) often on palm or sole. Found in warm coastal regions (Tx, Fl, Al, Lou, Carolinas). Superficial innoculation of soil, sewage, etc.
KOH prep of skin reveals

Black Piedra (hair shaft)

Piedraia hortae. More common in tropics. Hard black gritty nodules on shaft of hair (may look like nits) usually on scalp. Nodules firmly attached. Tx: shave infected hairs and improve hygiene

White Piedra (hair shaft)

Trichoporon beigelli. More common in semi-tropics like S. USA. Usually acquired by contact with pets/animals. White/light brown soft (fluffy) nodules on pubic or axillary hairs, beards, eyebrows. Loosely attached. Tx: shave infected hairs and improve hygi

Cutaneous Mycoses

caused by dermatophytes (microsporum, trichophyton, epidermophyton --> usually lower 1/2 of body). infection of skin, nails, hair. usually limited to keratinized layers, epidermis and dermis. use keratin as nutrient source. tissue damage and inflamation o

Tinea capitis

scalp, eyebrows, lashes. distinct scaly lesion, can result in hair loss over whole scalp. may be a "favus" mass of hyphal elemnts surrounding base of hair shaft
Tx: Griseofulvin

Tinea barbae


Tinea corporis

torso, arms, legs aka ring worm. Red round scaly patch w/ raised border. inflamed periphery w/ pustules, occuring anywhere esp. trunk

Tinea manus


Tinea unguium - onychomycosis

nail plate and bed. hyperkeratosis/discoloation (dry, cracked, brittle, disfigured nails). not painful, just embarrassing. DM and AIDS pt's common. Difficult for drug to get into nail, may need systemic oral antifungals (toxic)

Tinea cruris

groin aka jock itch. 90% in men, 2ndary infection common. Raised border of pustules

Tinea pedis

feet, athletes foot, usually chronic, may spread to nails, 2ndary bacterial infection common

Candidiasis (not a dermatophyte)

C. albicans. yeast naturally (commensal), pseudohyphal/hyphal in tissue (pathalogical). can cause skin/nail infections in moist areas. (diaper rash, dishwasher's hands). May present as papules or confluent plauqes of redness tenderness and cracking.
Can s

Subcutaneous Mycoses

infect dermis, subcutaneous tissue, and bone. usually acquired through traumatic innoculation (usually feet, hands, legs, buttocks) from soil or vegetation.


found in US. infection of cutaneous/subcutaneous and lymphatics by Sporothrix schenckii - mold in nature, yeast in tissues. usually thru rose thorns, wood splinters, sphagnum moss. Inflammation at site, then painless granulomatous lesion and secondary les


Usually tropics. Darkly pigmented soil fungi. Lower limb red/gray cauliflower lesions - painless. Looks like a wart. Brown hyphae in KOH prep, copper penny appearance under microscope. Tx: radical surgery and drugs

Mycetoma (Madura foot)

Usually tropics. Chronic subcutaneous infection usually in foot from soil fungi. Slow growing papule at site of inoculation. Pus/blood from ulcers, drains to bone. Colored grains in discharge. Tx: radical surgery and drugs

Viral Papillomas/Nodules - Warts (HPV)

Papovaviridae family, non-enveloped, dsDNA, matures w/ tissue gradient. Expansion of layers due to E6/E7 (no cancer tho). Hyperkeratosis and Koilodal (halo & altered nucleus) cells visible in scrapes
- Common warts (Verruca valgaris, HPV 2,3,10): exophyti

Viral Papillomas/Nodules Molluscum (contagiosum)

Poxviridae, large dsDNA, replicates in cytoplasm.
Painless, Pearly, Umbilicated Nodule. Usually in sexual area (sexually transmitted) but can be on face/hands/etc in kids (fomite eg. towel transmission). Divot in center (umbilicated) can sometimes express

Viral Ulcers & Purulent Lesions - Herpes labialis (HSV)

cold sores, reactivation events (primary herpetic lesions much worse). Can cause herpes simplex keratitis (looks like conjunctivitis) leading to blindness if unTx'ed. Encephalitis also possible (most common cause of infectious encephalitis in US). Herpeti

Viral Ulcers & Purulent Lesions - Chicken Pox/Shingles (VZV)

Varicella Zoster Virus. Herpesviridae. One serotype, respiratory transmission along w/ saliva and lesions.
Chicken Pox: Lesions most prevalent on trunk, (centripetal) face and scalp accompanied by fever x 5 days. Vesicles to pustules to scabs, usually fou

Viral Ulcers & Purulent Lesions - Smallpox (Variola)

Variola. Poxviridae family, dsDNA, cytoplasmic replication.
Transmission thru lesions (months) and aerosol.
Abrupt onset of high fever, malaise, HA, myalgia, nausea. Lesions on mouth (enanthem) progress to skin (exanthem). Centrifugal distribution (face/e

Classic childhood Exanthems
1) Measles *
2) scarlet fever
3) German Measles *
4) atypical scarlet fever
5) Erythema Infectiosum *
6) Roseola *

1) Measles (Rubeola) - pink to red macculopapular rash starting on hairline and spreading downward, can be confluent x 5-6 days. Prodrome = cough coryza and conjunctivits; Koplik's spots (small white spots opposite molars); high fever. Transmitted via res

Classic childhood Exanthems
3) German Measles

3) German Measles (Rubella) - similar to Measles but fainter and doesn't coalesce. Prodrome of low grade fever, lymphadenopathy and URT Sx. May be associated w/ arthralgia and arthritis. Congenital (mom gets rubella during 1st trimester) possible: deafnes

Classic childhood Exanthems
5) Erythema Infectiosum

5) Erythema Infectiosum aka 5th disease (B19 Parvovirus). Fever and rash starts on cheeks and moves in lace-like pattern over rest of body. Usually self-limiting, but...
Aplastic Crisis in those w/ chronic anemias
Arthralgia & Arthritis - may be only Sx i

Classic childhood Exanthems
6) Roseola

6) Roseola Infantum (HHV-6 or 7).
High fever x 4 days followed by maculopapular rash x 1-2 days
Herpesviridae family, dsDNA, enveloped
- HHV-6 shed by 85% of adults, replicates in T/B cells and oral pharynx. Latent in T cells
- HHV-7 replicates in CD4+ T