Entamoeba histolyticaProtazoa.- Transmission: Cysts in water Amebiasis – 1-4 weeks of bloody diarrhea (dysentery), liver abscess ("anchovy paste" exudate), usually a single liver abscess in the right lobe, RUQ pain. Diagnosis: ...
CryptosporidiumProtazoa.- Severe diarrhea in AIDS- Mild disease (watery diarrhea) in immunocompetent hosts - Transmission: Oocysts in water Diagnosis: Oocysts on acid-fast stain, antigen detection Treatment: Nitazoxanide ...
Naegleria fowleriProtazoa.- Transmission: Swimming in freshwater lakes; enters via cribriform plate. - Rapidly fatal meningoencephalitis Diagnosis: Amoebas in CSF. Treatment: Amphotericin B has been effective for a few ...
PlasmodiumMalaria – fever, headache, anemia, splenomegaly, GI symptoms P. vivax/ovale – 48-hour cycle, dormant form (hypnozoite) in liverP. falciparum – severe, irregular fever patterns; parasitized ...
BabesiaBabesiosis – fever and hemolytic anemia.- Predominantly in northeastern United states- Asplenia ↑ risk of severe disease. - Transmission: Ixodes tick (same as Borrelia burgdorferi) Diagnosis: ...
Trichomonas vaginalisAnaerobic, motile protazoan with flagella- Transmission: sexual (cannot exist outside human because it cannot form cysts) Vaginitis – foul-smelling, yellow or green discharge; itching and burning.- ...
Trichuris trichura (whipworm)Nematode (roundworm) Transmission: fecal-oral. Clinical features:- Often asymptomatic- Loose stools, anemia- Rectal prolapse in children Treatment: Bendazoles
Echinococcus granulosusCestode (tapeworm) Transmission: Ingestion of eggs in food contaminated with dog feces- Sheep are intermediate host Cystic echinococcosis:- Hydatid cysts in liver ("eggshell calcification"); cysts can ...
Clonorchis sinensisTrematode (fluke) Transmission: undercooked fish Clinical features:- Biliary tract inflammation → pigmented gallstones- Associated with cholangiocarcinoma Treatment: Praziquantel
EctoparasitesScabies (Sarcoptes scabiei)- Common in children, crowded populations (jails, nursing homes)- Mites that burrow into the stratum corneum and cause pruritus (worse at night)- Serpiginous burrows (lines) in ...
Haemophilus ducreyiTransmission: sexual transmission and direct contact - Chancroid- Soft, painful genital ulcer with exudate- Slow to heal without treatment- Inguinal adenopathy Diagnosis: DNA probe, 'school of fish' appearance ...
HistoplasmosisDimorphic fungus. Environmental form: hyphae with microconidia. Tissue form: intracellular yeasts, no capsule. Location: Mississippi and Ohio River Valleys- Found in soil with bird (eg, starlings) or ...
BlastomycosisDimorphic fungus. Location: Eastern and Central US Pathology: Broad-based budding of Blastomyces (same size as RBCs) Symptoms:- Inflammatory lung disease- Can dissiminate to skin/bone- Verrucous skin ...
CoccidioidomycosisDimorphic fungus. Location: Southwestern US, California- Found in desert sand Pathology: Spherule filled with endospores of Coccidioides Disease: Valley fever- Flu-like illness or pneumonia- Dissiminates ...
ParacoccidioidomycosisLocation: Latin America Pathology: Budding yeast of Paracoccidoides with "captain's wheel" formation Clinical presentation: Similar to blastomycosis- Acute pneumonia- Painful nasal, pharyngeal, and laryngeal ...
Tinea (dermatophytes)Cutaneous mycosis Dermatophytes include Trichophyton, Epidermophyton, Microsporum.- Branching septae hyphae visible on KOH preparation with blue fungal stain.- Associated with pruritus. Tinea capitis: ...
Pityriasis versicolorCaused by Malassezia spp., a yeast-like fungus - Degradation of lipids produces acids that damage melanocytes and cause hypopigmented, hyperpigmented, and/or pink patches - More common in summer; moist, ...
Mucor and Rhizopus spp.Irregular, broad, nonseptate hyphae branching at wide angles. Mucormycosis- Mostly in ketoacidotic diabetic and/or neutropenic patients (eg, leukemia).- Inhalation of spores → fungi proliferate in ...
Nematode routes of infectionIngested:- Enterobius- Ascaris- Toxocara- Trichinella Cutaneous:- Strongyloides- Ancylostoma- Necator Bites:- Loa loa (deer, horse, mango flies)- Onchocerca volvulus (blackflies)- Wuchereria bancrofti ...
Periodic-acid-Schiff stainStains glycogen, mucopolysaccharides. - Used to diagnose Whipple disease (Tropheryma whipplei).
Ziehl-Neelsen stain (carbol fuchsin)Acid-fast bacteria (eg, Mycobacteria, Nocardia; stains mycolic acid in cell wall); protozoa (eg, Cryptosporidium oocytes). - Auramine-rhodamine stain is more often used for screening (inexpensive, more ...
India ink stainCryptococcus neoformans - Mucicarmine can also be used to stain thick polysaccharid capsule red.
Special culture requirementsH influenzae – Chocolate agar (Factors V [NAD+] and X [hematin]) N gonorrhoeae, N meningitidis – Thayer-Martin agar (Selectively favors growth of Neisseria by inhibiting growth of gram ⊕ bacteria ...
Bugs with exotoxinsDiphtheria toxin (Corynebacterium diphtheriae), exotoxin A (Pseudomonas aeruginosa): Inactivate elongation factor (EF-2). Shiga toxin (Shigella), shiga-like toxin (EHEC): Inactivate 60S ribosome by ...
EndotoxinLPS found in outer membrane of gram ⊝ bacteria. Composed of O-antigen + core polysaccharid + lipid A (the toxic component). Released upon cell lysis or by living cells by blebs detaching from outer ...
Nocardia vs. ActinomycesBoth are gram ⊕ and form long, branching filaments resembling fungi Nocardia:- Aerob- Acid fast (weak)- Found in soil- Pulmonary infections in immunocompromised (can mimic TB but with Θ PDD)- Cutaneous ...
SalmonellaGram ⊝ rod. Non-lactose fermenter, oxidase ⊝. Can invade the GI tract via M cells of Peyer patches. Flagellated. Produce H2S, motile. Salmonella typhi:- Human reservoir only- Can disseminate hematogenously- ...
ShigellaGram Θ rod. Non-lactose fermenter, oxidase Θ. Reservoir: Human colon onlyTransmission: fecal-oral spread. Low infectious dose (vs. Salmonella - high). Pathogenesis:- Invasion of M cells, create very ...
Tick-borne illnessesEhrlichosis:- Ehrlichia, vector is tick.- Monocytes with morulae in cytoplasm. Anaplasmosis:- Anaplasma, vector is tick.- Granulocytes with morulae in cytoplasm. Q fever:- Coxiella burnetii, no arthropod ...
Bugs causing food-borne illnessS aureus and B cereus food poisoning starts quickly and ends quickly B cereus - Reheated rice C botulinum - Improperly canned foods (toxins), raw honey (spores) C perfringens - Reheated meat E coli - ...
Bugs causing diarrheaBloody diarrhea- Campylobacter - comma-shaped, grow at 42°C- Salmonella- Shigella- EHEC, EIEC- Y enterocolitica - day care outbreaks, pseudoappendicitis- Entamoeba histolytica - protozoan; amebic dysentery; ...
Common causes of pneumoniaNeonates: Group B streptococci, E. coliChildren: Mycoplasma, C trachomatis/pneumoniae, S pneumoniaeAdults: S pneumoniae, H influnzae, anaerobes, viruses (eg, influenza)Elderly: S pneumoniae, influenza, ...
Common causes of meningitisNeonates: Group B streptococci, E coli, ListeriaChildren: S pneumoniae, N meningitidis, H influenzae B6-60 years: S pneumoniae, N meningitidis (#1 in teens), enteroviruses, HSVElderly: S pneumoniae, Listeria ...
Infections causing brain abscessMost commonly viridans streptococci and Staphylococcus aureus - Multiple abscesses are usually from bacteremia- single lesions from contiguous sites: otitis media and mastoiditis --> temperal lobe and ...
Osteomyelitis- Assume if no other information is available- S aureus - - Sexually active - N gonorrhoeae (septic arthritis more common) - Sickle cell disease - Salmonella and S aureus - Prosthetic joint replacement ...
Urinary tract infectionsCystitis presents with dysuria, frequency, urgency, subrapubic pain, and WBCs (but not WBC casts) in urine - Males: infants with congenital defects, vesicourethral reflux- Elderly: enlarged prostate ...
UTI bugsE coli: Leading cause of UTI. Colonies show green metallic sheen on EMB agar Staphylococcus saphrolyticus: 2nd leading cause of UTI in sexually active women Klebsiella pneumoniae: 3rd leading cause of ...
Common vaginal infectionsBacterial vaginosis:- No inflammation- thin, white discharge with fishy odor- Clue cells- pH >4.5- Treatment: Metronidazol Trichomonas vaginitis:- Inflammation ("strawberry cervix")- Frothy, yellow-green, ...
ToRCHeS infectionsToxoplasmosa gondii:- Cat feces or ingestion of undercooked meat- Usually asymptomatic; lymphadenopathy- Neonate: Classic triad: chorioretinitis, hydrocephalus, and intracranial calcifications ± blueberry ...
Red rashes of childhoodCoxsackievirus type A: Hand-foot-mouth disease.- Oval-shaped vesicles on palmes and soles; vesicles and ulcers in oral mucosa Human herpesvirus 6: Roseola (exanthema subitum)- Asymptomatic rose-colored ...
Red rashes of childhoodCoxsackievirus type A: Hand-foot-mouth disease.- Oval-shaped vesicles on palmes and soles; vesicles and ulcers in oral mucosa Human herpesvirus 6: Roseola (exanthema subitum)- Asymptomatic rose-colored ...