Pictures Flashcards
Sporothrix schenckii
Dimorphic, cigar-shaped budding yeast that lives on vegetation.
Nodules and ulcers extending along path of lymphatic drainage (ascending lymphangitis)
Rose gardener’s disease
Varicella-zoster (chickenpox)
Chickenpox, shingles, encephalitis, pneumonia. Latent in dorsal root or trigeminal ganglia. Most common complication of shinges is post-herpetic neuralgia.
Transmitted by respiratory secretions.
Vibrio cholerae
Produces profuse rice-water diarrhea via enterotoxin that permanently activates Gs, increases cAMP. Endemic to developing countries.
Secondary syphilis produces disseminated disease with constitutional symptoms.
Maculopapular rash
Bacillus anthrax
Gram-positive, spore-forming rod
Adenovirus (febrile pharyngitis)
DNA Virus
DS and linear
Febrile pharyngitis–sore throat
Acute hemorrhagic cystitis
Pneumonia
Conjuntivitis –“pink eye”
HSV-2 (Positive Tzanck smear in genital herpes; multinucleated giant cells).
Tzanck test – a smear of an opened skin vescile to detect multinucleated giant cells commonly seen in HSV-1, HSV-2, and VZV infection.
“Tzanck heavens I do not have herpes.”
Schistosoma mansoni (egg with lateral spine)
Trematodes (flukes)
Transmission: Snails are host; cercariae penetrate skin of humans
Disease: Liver and spleen enlargment, fibrosis, and inflammation
Treatment: Praziquantel
Tinea capitis
Occurs on head, scalp.
Associated with lymphadenopathy, alopecia, scaling.
Mucor
Irregular, broad, nonseptate hyphae branching at wide angles.
Primary syphilis, presenting as localized disease with painless chancre.
HHV-6/HHV-7 (Roseola; diffuse macular rash)
DNA virus; Herpesvirus
High fevers for several days that can cause seizures, followed by a diffuse macular rash. Transmitted by saliva.
Ixodes tick
Vector for Borrelia burdorferi (Lyme disease), Anaplasma spp., and protozoa (Babesia)
Mycobacterium leprae
Leprosy (Hansen disease)
Leonine facies (lepromatous form)
Lepromatous form is worse than tuberculoid, characterized by low cell-mediated immunity with humoral Th2 response.
Plasmodium malariae
72-hour cycle (quartan)
Schistosoma haematobium (egg with terminal spine)
Trematodes (flukes)
Transmission: Snails are host; cercariae penetrate skin of humans
Disease: Chronic infection with S. hematobium (egg with terminal spine) can lead to squamous cell carcinoma of the bladder (painless hematuria) and pulmonary hypertension.
Treatment: Praziquantel
Epstein-Barr virus (Mononucleosis; posterior cervical lymphadenopathy)
Mononucleosis. Characterized by fever, hepatosplenomegaly, pharyngitis, and lymphadenoapthy (especially posterior cervical nodes).
Transmitted by respiratory secretions and saliva; also called “kissing disease” since commonly seen in teens, young adults.
Infects B cells through CD21. Atypical lymphocytes seen on peripheral blood semar are not infected B cells but rather reactive cytotoxic T cells.
Detect by positive Monospot test – heterophile antibodies detected by agglutination of sheep or horse RBCs.
Associated with lymphoas (eg., endemic Burkitt lymphoma), nasopharyngeal carcinoma.
Pneumocystis jirovecii
Yeast-like fungus
Diffuse, bilateral ground-glass opacities on CSR/CT.
Start prophylaxis when CD4+ count drops to <200 cells/mm3 in HIV patients.
Aspergillus fumigatus
Conidiophore with radiating chains of spores
Trypanosoma cruzi blood smear
Protozoa–Visceral Infections
Chagas disease: dilated cardiomyopathy with apical atrophy, megacolon, megaesophagus; predominantly in South America
Unilateral periorbital swelling (Romana sign) characteristic of acute state
Transmission: Reduviid bug (“kissing bug”) feces, deposited in a painless bite (much like a kiss)
Diagnosis: Blood smear
Treatment: Benzidazole or nifurtimox
Plasmodium (Blood smear)
Trophozoite ring form within RBC
Disease: Malaria (fever, headache, anemia, splenomegaly)
Transmission: Anopheles mosquito
Treatment: Chloroquine (for sensitive species), which blocks Plasmodium heme polymerase; if resistant, use mefloquine or atovaguone/proguanil
If life-threatening, use intravenous quinidine or artesunate (test for G6PD deficiency).
For P. vivax/ovale, add primaquine for hypnozoite (test for G6PD deficiency).
Varicella-zoster (shingles)
Chickenpox, shingles, encephalitis, pneumonia. Latent in dorsal root or trigeminal ganglia. Most common complication of shinges is post-herpetic neuralgia.
Transmitted by respiratory secretions.
Blastomycosis
States east of Mississippi RIver and Central America. Causes inflammatory lung disease and can disseminate to skin and bone.
Forms granulomatous nodules.
Broad-base budding (same size as RBC).
Blasto buds broadly.
Helicobacter pylori
Curved gram-negative rod that is catalase, oxidase, and urease (+)
Giardia lamblia cysts
GI parasite
Transmission: cysts in water
Treatment: metronidazole
Echinococcus granulosus (hydatid cyst)
Cestodes (tapeworms)
Transmission: Ingestion of eggs from dog feces; sheep are an intermediate host
Disease: Hydatid cysts in liver, causing anaphylaxis if antigens released (hydatid cyst injected with ethanol or hypertonic saline to kill duaghter cysts before removal)
Treatment: Albendazole
Coccidioidomycosis
Spherule (much larger than RBC) filled with endospores.
Southwestern United States, California.
Causes pneumonia and meningitis; can disseminate to bond and skin.
Case rate increases after earthquakes (spores in dust thrown into air -> inhaled -> spherules in lung).
Streptococcus pneumoniae
CMV (Infected cells have characteristic “owl eye” inclusions.
DNA virus; Herpesvirus
Congenital infection, mononucleosis (Monospot-negative), pneumonia, retinitis. Infected cells have characteristic “owl eye” inclusions. Latent in mononuclear cells.
Transmitted congenitally and by transfusion, sexual contact, saliva, urine, transplant.
Plasmodium falciparum
Severe;
Irregular fever patterns;
Parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs
HHV-8 (Kaposi sarcoma)
Neoplasm of endothelial cells. Seen in HIV/AIDS and transplant patients. Dark/violaceous plaques or nodules representing vascular proliferations. Can also affect GI tract and lungs.
Transmitted by sexual contact.
Entamoeba histolytica cysts (with up to 4 nuclei)
Amebiasis: bloody diarrhea (dysenter), liver abscess (“anchovy paste” exudate), RUQ pain; histology shows flask-shaped ulcer
Transmission: cysts in water
Treatment: Metronidazole; iodoquinol for asymptomatic cyst passers
Aspergillus fumigatus
Septate hyphae that branch at 45° angle
Ascaris lumbricoides (giant roundworm) (egg in feces)
Nematodes (roundworms)–Intestinal
Transmission: Fecal-oral; eggs visible in feces under microscope
Disease: Intestinal infection with possible obstruction at ileocecal valve
Treatment: Bendazoles
Tinea cruris
Occurs in inguinal area
Often does not show central slearing seen in tinea corporis
Echinococcus granulosus (Hydatid cysts in liver)
Cestodes (tapeworms)
Transmission: Ingestion of eggs from dog feces; sheep are an intermediate host
Disease: Hydatid cysts in liver, causing anaphylaxis if antigens released (hydatid cyst injected with ethanol or hypertonic saline to kill duaghter cysts before removal)
Treatment: Albendazole
Spirochetes
Spiral-shaped bacteria with axial filaments
Includes Borrelia (big), Leptospira, and Treponema. Only Borrelia can be visualized using aniline dyes in light microscopy due to size.
Lysteria monocytogenes actin rockets
“Rocket tails” (red structures) of Listeria enable intracellular movement and spread between two cells.
HSV-1 (herpes labialis)
Herpesvirus
Mycoplasma pneumoniae
No cell well. Not seen on gram stain. Pleiomorphic.
Classic cause of atypical “walking” pneumonia (insidious onset, headache, nonproudctive cough, patchy or diffuse interstital infiltrate)
Rickettsia rickettsii (Rocky Mountain Spotted Fever)
Rash typically starts at wrists and ankles and then spreads to trunk, palms, and soles.
Vector is tick.
Giardia lamblia trophozoites
GI parasite
Transmission: cysts in water
Treatment: metronidazole
Congenital syphilis
Facial abnormalities such as rhagades (linear scars at angle of mouth), snuffles, saddle nose, notched (Hutchinson) teeth, mulberry molars, and short maxilla; saber shins; CN VIII deafness.
Naegleria fowleri (amoebas in spinal fluid)
Protozoa–CNS Infections
Disease: Rapidly fatal meningoencephalitis
Transmission: Swimmin in freshwater lakes (think Nalgene bottle filled with fresh water containing Naegleria); enters via cribiform plate
Diagnosis: Amoebas in spinal fluid
Treatment: Amphotericin B has been effective for a few surivors
Nocardia
Branching filaments on acid-fast stain
Gram-positive aerobe
Weakly acid fast
Found in soil
Haemophilus influenzae epiglottitis
Thickening of epiglottis on ateral neck radiograph, showing “thumbprint sign.”
Toxoplasma gondii tachyzoite
Congenital toxoplasmosis = classic traid of chorioretinitis, hydrocephalus, and intracranial calcifications;
Reactivation in AIDS -> brain abscess seen as ring-enhancing lesions on CT/MRI
Transmission: Cysts in meat (most common); oocysts in cat feces; crosses placenta (pregnant women should avoid cats)
Diagnosis: Serology, biopsy (tachyzoite)
Treatment: Sulfadizaine + pyrimethamine
Echinococcus granulosus
Cestodes (tapeworms)
Transmission: Ingestion of eggs from dog feces; sheep are an intermediate host
Disease: Hydatid cysts in liver, causing anaphylaxis if antigens released (hydatid cyst injected with ethanol or hypertonic saline to kill duaghter cysts before removal)
Treatment: Albendazole
Toxoplasma gondii
Congenital toxoplasmosis = classic traid of chorioretinitis, hydrocephalus, and intracranial calcifications;
Reactivation in AIDS -> brain abscess seen as ring-enhancing lesions on CT/MRI
Transmission: Cysts in meat (most common); oocysts in cat feces; crosses placenta (pregnant women should avoid cats)
Diagnosis: Serology, biopsy (tachyzoite)
Treatment: Sulfadizaine + pyrimethamine
Corynebacterium diphtheriae
(Pseudomembranous pharyngitis)
HSV-1 (keratoconjunctivitis)
Herpesvirus
Secondary syphilis produces disseminated disease with constituional symptoms
Maculopapular rash on palms and soles
Taenia solium (Neurocysticercosis)
Cestodes (tapeworms)
Ingestion of larvae encysted in undercooked pork causes intestinal infection; treat with Praziquantal
Ingestion of eggs causes cysticercosis, neurocysticercosis; treat with Praziquantal; albendazole for neurocysticercosis
Entamoeba histolytica trophozoites (with RBCs in the cytoplasm)
Amebiasis: bloody diarrhea (dysenter), liver abscess (“anchovy paste” exudate), RUQ pain; histology shows flask-shaped ulcer
Transmission: cysts in water
Treatment: Metronidazole; iodoquinol for asymptomatic cyst passers
Streptococcus pyogenes (Group A strep)
Trichomonas vaginalis (trophozites [motile] on wet mount)
Protozoa–Sexually transmitted infections
Disease: Vaginitis – foul-smelling, greenish discharge; itching and burning; do not confuse with Gardnerella vaginalis, a gram-variable bacterium associated with bacterial vaginosis
Tranmission: Sexual (cannot exist outside human because it cannot form cysts)
Diagnosis: Trophozoites (motile) on wet mount; “strawberry cervis”
Treatment: Metronidazole for patient and partner (prophylaxis)
Taenia solium
Cestodes (tapeworms)
Ingestion of larvae encysted in undercooked pork causes intestinal infection; treat with Praziquantal
Ingestion of eggs causes cysticercosis, neurocysticercosis; treat with Praziquantal; albendazole for neurocysticercosis
Candida albicans
Pseudohyphae and budding yeasts at 20°C
Gas gangrene (Clostridium perfringens)
Leishmania donovani (macrophage containing amastigotes)
Protozoa–Visceral Infections
Visceral leishmaniasis–spiking fevers, hepatosplenomegaly, pancytopenia
Transmission: Sandfly
Diagnosis: Macrophages containing amastigotes
Treatment: Amphotericin B, sodium stibogluconate
Haemophilus influenzae epiglottitis
Paracoccidioidomycosis
Budding yeast with “captain’s wheel” formation (much larger than RBC).
Pneumocystis jirovecii
Yeast-like fungus
Diagnosed by lung biopsy or lavage.
Disc-shaped yeast forms on methenamine silver stain of lung tissue.
Candida albicans
Systemic or superficial fungal infection
Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS).
Babesia blood smear
Protozoa–Hematologic infections
Babesiosis–fever and hemolytic anemia; predominantly in northeastern United States; asplenia increases risk of severe disease
Transmission: Ixodes tick (same as Borrelia burgdorferi of Lyme disease; may often coinfect humans)
Diagnosis: Blood smear: ring form (C1); Maltese cross (C2); PCR
Treatment: Atovaquone + axithromycin
Condyloma lata of secondary syphilis
Smooth, moist, painless, wart-like white lesions on genitals
Pseudomonas aeruginosa infection
Ecthyma gangrenosum (typically seen in immunocompromised patients) of the chest
Large ulcer with necrotic region.
Staphylococcus aureus
Tinea pedis
Three varieties
Interdigital
Moccasin distribution
Vesicular type
Wucheria bancrofti (elephantiasis)
Nematodes (roundworms)–Tissue
Transmission: Female mosquito
Disease: Elephantiasis–worms block lymphatic vessels, takes 9 months-1 year after bite to become symptomatic
Treatment: Diethylcarbamazine
Congenital syphilis
Facial abnormalities such as rhagades (linear scars at angle of mouth), snuffles, saddle nose, notched (Hutchinson) teeth, mulberry molars, and short maxilla; saber shins; CN VIII deafness.
Tertiary syphilis
Gummas (chronic granulomas)
Chlamydia trachomatis
Reactive arthritis (Reiter syndrome)
Follicular conjunctivis (Types A, B, C, can cause blindness in Africa)
Nongonococcal urethritis, PID (Types D-K)
Neisseria
N. gonorrhoeae is often intracellular (within neutrophil in picture)
Caseating gramuloma (secondary tuberculosis)
Central necrosis (pinkish region in upper left) with multinucleated Langerhans giant cell (arrow).
P. vivax/ovale
Red granules (Schuffner stippling) throughout RBC cytoplasm seen with P. vivax/ovale
Tinea (dermatophytes)
Cutaneous fungal infections
Branching septate hyphae visible on KOH preparation with blue fungal stain.
HSV-2 (Herpes genitalis)
Herpesvirus
Latent in sacral ganglia
Tinea versicolor
“Speghetti and meatballs” appearance on microscopy
Mycobacteria
Acid fast (pink rods)
Erlichia
Monocytes with morulae (berry-like inclusions) in cytoplasm.
Vector is tick
Trypanasoma brucei (blood smear)
Protozoa–CNS infections
African sleeping sickness–enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma
Two subspecies: Trypanosoma brucei rhodesiense, Trypanosoma brucei gambiense
Transmission: Tsetse fly, painful bite
Diagnosis: Blood smear
Treatment: Suramin for blood-borne disease or melarsoprol for CNS penetration
Tinea versicolor
Caused by Malassezia spp., a yeast-like fungus
Degradation of lipids produces acids that damage melanocytes and cause hypopigmented and.or pink patches.
Can occur any time of year but common in summer (hot, humid weather).
Histoplasmosis
Mississippi and Ohio River valleys.
Causes pneumonia
Macrophage filled with Histoplasma (smaller than RBC)
Epstein-Barr Virus (atypical lymphocytes on blood smear are reactive cytotoxic T cells [not infected B cells])
DNA virus; Herpesvirus (Enveloped; DS and linear)
Mononucleosis. Characterized by fever, hepatosplenomegaly, pharyngitis, and lymphadenoapthy (especially posterior cervical nodes).
Transmitted by respiratory secretions and saliva; also called “kissing disease” since commonly seen in teens, young adults.
Infects B cells through CD21. Atypical lymphocytes seen on peripheral blood semar are not infected B cells but rather reactive cytotoxic T cells.
Detect by positive Monospot test – heterophile antibodies detected by agglutination of sheep or horse RBCs.
Associated with lymphoas (eg., endemic Burkitt lymphoma), nasopharyngeal carcinoma.
Gardnerella vaginalis
Presents as a gray vaginal discharge with a fishy smell
Nonpainful (vs. vaginitis)
Clue cells, or vaginal epithelial cells covered with Gardnerella bacteria (“stippled” appearance along outer margins), are visible under the microscope.
Cryptosporidium oocysts (on acid-fast stain)
Severe diarrhea in AIDS
Mild disease (watery diarrhea) in immunocompetent hosts
Prevention: By filtering city water supplies
Nitazoxanide: in immunocompetent hosts
Molluscum contagiosum–flesh-colored papule with central umbilication
Poxvirus
Enveloped
DS and linear
Pseudomembranous colitis
(Clostridium difficile)
Cryptococcus neoformans
5-10 µm yeasts with wide capsular halos and unequal budding in India Ink stain.
Cutaneous anthrax
Painless papule surrounded by vesicles ->ulcer with black eschar (painless necrotic)
Legionella pneumophila
Gram-negative rod. Gram stains poorly – use silver stain.
Grow on charcoal yeast extract.
Detected by presence of antigen in urine.
Aerosol transmission from environmental water source habitat (e.g., air conidtioning systems, hot water tanks).
No person-to-person transmission.
Legionnaire’s disease – severe pneumonia (often unilateral and lobar), fever, GI, and CNS symptoms
Enterobius vermacularis (pinworm) (egg)
Nematodes (roundworms)–Intestinal
Transmission: Fecal-oral
Disease: Intestinal infection causing anal pruritis (diagnosed by seeing egg via the tape test)
Treatment: Bendazoles (because worms are bendy)
Tinea pedis
Three varieties
Interdigital
Moccasin distribution
Vesicular type
Pseudomonas aeruginosa
Aerobic, motile, gram-negative rod.
Has a grape-like odor.
PSEUDDOmonas is associated with:
Pneumonia
Sepsis
Otitis Externa (swimmer’s ear)
UTIs
Drug use
Diabetes
Osteomyelitis
Darkfield microscopy to visualize treponemes in fluid from lesions in primary or secondary syphilis.
Candida albicans
Germ tubes at 37°C
Actinomyces israelii
Gram positive anaerobe
Not acid fast
Adenovirus (conjunctivitis)
No Envelope
DNA Virus
DS and linear
Febrile pharyngitis–sore throat
Acute hemorrhagic cystitis
Pneumonia
Conjuntivitis –“pink eye”
