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• Staphylococcus aureus Gram-positive, β-hemolytic, catalase ⊕, coagulase ⊕, cocci in clusters.- Protein A (virulence factor) binds Fc-IgG, inhibiting complement activation and phagocytosis.- Forms fibrin clot around self → abscess.- Commonly colonizes the nares, ears, axilla, and groin. Causes:- Inflammatory disease – skin infections, organ abscesses, pneumonia (often after influenza virus infection), endocarditis, septic arthritis, osteomyelitis.- Toxin-mediated – Toxic shock syndrome (TSST-1, superantigen), scalded skin syndrome (exfoliative toxin), rapid-onset food poisoning (enterotoxins).- MRSA (methicillin-resistant S aureus) infection – important cause of serious nosocomial and community-acquired infection; resistant to methicillin and nafcillin because of altered penicillin-binding protein. Staphylococcal toxic shock syndrome (TSS) – fever, vomiting, rash, desquamation, shock, end-organ failure. ↑ AST, ↑ ALT, ↑ bilirubin. Associated with prolonged use of vaginal tampons or nasal packing. S aureus food poisoning due to ingestion of preformed toxin → short incubation period (2-6 hr) followed by nonbloody diarrhea and emesis. Enterotoxin is heat stable → not destroyed by cooking.
• Staphylococcus epidermidis Gram ⊕, catalase ⊕, coagulase ⊝, urease ⊕ cocci in clusters.- Novobiocin sensitive.- Does not ferment mannitol (vs S aureus).- Normal flora of skin; contaminates blood cultures. - Infects prosthetic devices (eg, hip implant, heart valve) and IV catheters by producing adherent biofilms.
• Staphylococcus saprophyticus - Gram ⊕, catalase ⊕, coagulase ⊝, urease ⊕, cocci in clusters.- Novobiocin resistant.- Normal flora of female genital tract and perineum. - Second most common cause of uncomplicated UTI in young women (most common cause is E. coli).
• Streptococcus pneumoniae - Gram ⊕, lancet-shaped diplococci. Encapsulated. IgA protease. - Optochin sensitive.- Quellung-reaction-positive (capsule swelling on microscopy after exposure to capsular antigens) Most common cause of:- Meningitis- Otitis media (in children)- Pneumonia- Sinusitis - Pneumococcus is associated with "rusty" sputum, sepsis in patients with sickle cell disease, and asplenic patients.- No virulence without capsule.
• Viridans group streptococci Gram ⊕, α-hemolytic cocci.- Resistant to optochin (vs S pneumoniae).- Normal flora of the oropharynx. - Streptococcus mutans and S mitis cause dental caries. - S sanguinis makes dextrans that bind to fibrin-platelet aggregates on damaged heart valves, causing subacute bacterial endocarditis.
• Streptococcus pyogenes (group A streptococci) Gram ⊕ cocci in chains. - Bacitracin sensitive, β-hemolytic, pyrrolidonyl arylamidase (PYR) ⊕.- Hyaluronic acid capsule and M protein inhibit phagocytosis. Cause:- Pyogenic – pharyngitis, cellulitis, impetigo ("honey-crusted" lesions), erysipelas- Toxigenic – scarlet fever, toxic shock-like syndrome, necrotizing fasciitis- Immunologic – rheumatic fever, glomerulonephritis - Antibodies to M protein enhance defense but can give rise to rheumatic fever.- ASO titer or anti-DNase B antibodies indicate recent infection.- Strains causing impetigo can induce glomerulonephritis. Jones criteria: Guidelines to diagnose rheumatic fever (Joint pain, ♥ Carditis, Nodules, Erythema marginatum, Syndeham chorea) Scarlet fever – blanching, sandpaper-like body rash, strawberry tongue, and circumoral pallor in the setting of group A streptococcal pharyngitis (erythrogenic toxin ⊕).
• Streptococcus agalactiae (group B streptococci) Gram ⊕ cocci, β-hemolytic, bacitracin resistant, colonizes vagina. - Causes pneumonia, meningitis, and sepsis, mainly in babies - Produces CAMP factor, which enlarges the area of hemolysis formed by S aureus.- Hippurate test ⊕. PYR ⊝. - Screen pregnant woman at 35-37 weeks of gestation with rectal and vaginal swabs. Patients with ⊕ culture receive intrapartum penicillin prophylaxis.
• Streptococcus bovis Gram ⊕ cocci, γ-hemolysis, grows in bile, but does no growth in 6.5% NaCl. - Colonizes the gut. - S gallolyticus (S bovis type 1) can cause bacteremia and subacute endocarditis and is associated with colon cancer.
• Enterococci Gram ⊕ cocci. Catalase ⊝, PYR ⊕ (like group A streptococcus)- γ-hemolysis. Can grow in 6.5% NaCl and bile (vs Streptococcus bovis).- Enterococci (E faecalis and E faecium) are normal colonic flora that are penicillin G resistant. Cause:- UTI- Biliary tract infections- Subacute endocarditis (following GI/GU procedures). - VRE (vancomycin-resistant enterococci) are an important cause of nosocomial infection.
• Bacillus anthracis Gram ⊕, spore-forming rod that produces anthrax toxin.- Only bacterium with an antiphagocytic polypeptide capsule (contains D-glutamate).- Colonies show halo of projections, sometimes referred to as "medusa head" appearance.- Anthrax toxin: made up of A and B subunits. The A subunit has two components: EF (edema factor, → ↑ cAMP → cell death) and LF (lethal factor, a metalloprotease) Cutaneous anthrax- Painless papule surrounded by vesicles → Ulcer with black eschar (painless, necrotic) → uncommonly progresses to bacteremia and death. Pulmonary anthrax (= Woolsorter's disease)- Inhalation of spores from sheep or goat skin → flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock.- CXR may show widened mediastinum. (Gastrointestinal anthrax: Hematemesis and bloody diarrhea) Treatment: penicillin, doxycyclin, ciprofloxacin
• Bacillus cereus - Gram ⊕ rod. Spores are heat-stable.- Grows in heated food that cools down too slowly or is improperly refrigerated (also known as reheated rice syndrome).- Keeping rice warm results in germination of spores and enterotoxin formation. - Causes food poisoning. - Emetic type usually seen with rice and pasta. Nausea and vomiting within 1-5 hours.- Caused by cereulide, a preformed toxin.- Diarrheal type causes watery, nonbloody diarrhea and GI pain within 8-18 hours.
• Corynebacterium diphtheriae Gram-⊕, aerobic rod.- Transmitted by respiratory droplets.  - Causes diphtheria via exotoxin encoded by β-prophage. Potent exotoxin inhibits protein synthesis via ADP-ribosylation of EF-2. Symptoms:- Pseudomembranous pharyngitis (grayish-white membrane) over posterior wall/tonsils- Bull neck, which may result in airway obstruction.- Lymphadenopathy- Myocarditis → Arrhythmias Lab diagnosis:- Gram-⊕ rods with metachromatic (blue and red) granules.- ⊕ Elek test for toxin.- Black colonies on cysteine-tellurite agar/Löffler medium. - Toxoid vaccine prevents diphtheria- Treatment: IM injections of penicillin G for 14 days
• Listeria monocytogenes Gram ⊕, catalase ⊕, motile, facultative intracellular rod.- Acquired by ingestion of unpasteurized dairy products and cold deli meats, via transplacental transmission, or by vaginal transmission during birth.- Grows well at refrigeration temperatures (4-10°C; "cold enrichment"). - Forms "rocket tails" via actin polymerization that allow intracellular movement and cell-to-cell spread across cell membranes, therefore avoiding antibody.- Characteristic tumbling motility in broth. Can cause:- Pregnant women: Chorioamnionitis, septicemia, and spontanous abortion- Infants: Granulomatosis infantiseptica (sepsis with high mortality; disseminated granulomas with central necrosis), neonatal meningitis- Meningitis in immunocompromised patients (eg, renal transplant patients, adults with cancer)- Self-limited gastroenteritis in healthy individuals Treatment: Ampicillin
• Leprosy (Hansen disease) - Caused by Mycobacterium leprae, an obligate intracellular, acid-fast bacillus - Likes cold temperatures (infects skin and superficial nerves – "glove and stocking" sensation).- Cannot be cultured.- Reservoir in United States: armadillos 1. Lepromatous form- Presents diffusely over the skin, with leonine facies - Acral, distal, symmetrical anesthesia, usually begins as "glove and stocking" neuropathy- Low cell-mediated immunity with humoral Th2-type response (IL-4, IL-5, IL-10)- Communicable, infectious (high bacterial load)- Lethal2. Tuberculoid form- Limited to a few hypoesthetic, hairless skin plaques- High cell-mediated immunity with Th1-type immune response (IL-2, IFN-γ, IL-12)- Low bacterial load- Granulomas formed by epithelioid cells and Langerhans giant cells Diagnosed via skin biopsy or tissue PCR.- Lepromin skin test (M leprae antigens injected intradermally) sued to distringuish forms. Patients with tuberculoid leprosy will develop an indurated nodule at the site of injection. Nonreactive in lepromatous leprosy due to weak Th1-respose. Treatment:- Dapsone and rifampin for tuberculoid form- Clofazimine is added for leptomatous form
• Neisseria Gram ⊝ diplococci. Metabolize glucose and produce IgA proteases. Contain lipooligosaccharides (LOS) with strong endotoxin activity. N gonorrhoeae is often intracellular (within neutrophils). Meningococci- Polysaccharide capsule- Maltose fermentation- Vaccine (except type B due to mimicry)- Transmitted via respiratory and oral secretions and are able to colonize the nasopharnyx due to fimbriae, pili. Penetrate epithelium and enter bloodstream. Penetrate cerebral capillary endothelium or choroid plexus.- Causes meningococcemia with petechial hemorrhages and gangrene of toes, meningitis, Waterhouse-Friderichsen syndrome (adrenal insufficiency, fever, DIC, shock)- Treatment: Ceftriaxone or penicillin G Gonococci- No polysaccharide capsule- Maltose not fermented- No vaccine due to antigenic variation of pilus proteins- Sexually or perinatally transmitted- Causes gonorrhea, septic arthritis, neonatal conjunctivitis, pelvic inflammatory disease (PID), and Fitz-Hugh-Curtis syndrome- Diagnosis: Nucleic acid amplification testing- Treatment: Ceftriaxone (+ azithromycin or doxycycline for possible chlamydial coinfection). Erythromycin eye ointment prevents neonatal blindness.
• Haemophilus influenzae Small gram ⊝ coccobacillary rod. - Aerosol transmission. - Produces IgA protease. - Culture on chocolate agar, which contains factors V (NAD+) and X (hematin) for growth. - Can also be grown with S aureus, which provides factor V via RBC hemolysis.- Capsule is composed of the polymer polyribosylribitol phosphate (PRP). It protects bacterium against phagocytosis and complement-mediated lysis by binding factor H, a circulating regulator protein that normally prevents complement (C3b) deposition on host cells Can cause:- Epiglottis: "cherry red" in children; "thumbprint sign" on lateral neck x-ray- Meningitis: epidemic in unvaccinated children ages 3 months to 2 years- Otitis media: usually nontypeable strains- Pneumonia Diagnosis: blood or CSF culture on chocolate agar; PCR; antigen detection of capsule - Vaccine contains type b capsular polysaccharide conjugated to diphtheria toxoid. Given between 2 and 18 months of age. Treatment: cefotaxime or ceftriaxone; use rifampin if still colonized
• Bordetella pertussis Gram ⊝, obligate aerobic coccobacillus.- Attachment to nasopharyngeal ciliated epithelial cells is via hemagglutinin; pertussis toxin aids in attachment.- Pertussis toxin (A and B component): ADP ribosylation of Gi, thereby impairing it → adenylate cyclase is no longer inhibited → ↑ cAMP → impaired cell signalling. Stages:- Catarrhal (1-2 weeks): Rhinorrhea, malaise, sneezing, anorexia- Paroxysmal: (2-4 weeks): Repetitive cough with inspiratory whoops, tongue protrusion, cyanosis, posttussive vomiting- Convalescent (3-4 weeks): Deminished paroxysmal cough, development of secondary complications (pneumonia, seizures, encephalopathy) Diagnosis: Regan-Lowe or Bordet-Genou media, direct immunofluorescence on nasopharyngeal smear, PCR- Blood count: lymphocyte-predominant leukocytosis >50'000 µl that corresponds to disease severity Treatment: supportive care; erythromycin for 14 days including all household contacts- Prevented by DTaP vaccines; immunity wanes 5-7 years
• Legionella pneumophila Gram ⊝ rod, facultative intracellular, obligate aerobe.- Aerosol transmission from environmental water source habitat (eg, air conditioning systems, hot water tanks). No person-to-person transmission.- Predisposing factors: smokers age >55 with high alcohol intake, chronic lung disease, immunosuppressed patients such as renal transplant patients. Legionnaires' disease- Severe atypical pneumonia (often unilateral and lobar)- High fever with relative bradycardia- Watery diarrhea - Headache & confusion- Common in smokers and in chronic lung diseasePontiac fever- Mild flu-like syndrome- Pneumonitis Lab findings:- Hyponatremia- Urine antigen test- Sputum gram stains showing many neutrophils, but few or no organisms → requires silver stain. - Legionella culture: charcoal yeast extract medium with iron and cysteine. Treatment: macrolide or quinolone
• Pseudomonas aeruginosa Gram ⊝, aerobic, motile. Non-lactose fermenter. Oxidase ⊕.- Grows in water and humid conditions, eg, hot tub, contaminated lens solution.- Has grape-like odor. - Produces pyoverdin and pyocyanin (blue-green pigment; generates ROS)- Produces exotoxin A (inactivates EF-2)- Produces phospholipase C (degrades cell membranes)- Elastase (degrades elastin – important for blood vessel destruction) - Mucoid polysaccharide capsule may contribute to chronic pneumonia in cystic fibrosis patients due to biofilm formation.- Wound infection in burn victims- Frequently found in water → hot tub folliculitis- Corneal ulcers/keratitis in contact lens wearers/minor eye trauma- Associated with pneumonia, sepsis, UTIs, diabetes, osteomyelitis, otitis externa (swimmer's ear), nosocomial infections (eg, catheters, equipment), addicts (drug abusers) - Ecthyma gangrenosum – rapidly progressive, necrotic cutaneous lesion. Typically in immunocompromised patients. Treatments: Carbapenems, aminoglycosides, monobactams, polymyxins (eg, polymyxin B, colistin), fluoroquinolones (eg, ciprofloxacin, levofloxacin), 3rd and 4th generation cephalosporins (eg, ceftazidime, cefepime), extended-spectrum penicillins (eg, piperacillin, ticarcillin)
• E coli Gram-negative rod. Produces β-galactosidase, which breaks down lactose into glucose and galactose. EMB agar – lactose fermenters grow as purple/black colonies. E coli grows colonies with a green sheen. Virulence factors:- Fimbriae – cystitis and pyelonephritis (P-pili)- K-capsule – pneumonia, neonatal meningitis- LPS endotoxin – septic shock EIEC: Dysentery. Clinical manifestations similar to Shigella. ETEC: Enterotoxins. Travelers' diarrhea (watery). (T for traveler) EPEC: No toxin. Diarrhea, usually in children. (P for pediatrics) EHEC. O157:H7 is most common serotype. Often transmitted via undercooked meat. Does not ferment sorbitol (distinguishes EHEC from other E. coli).Shiga-like toxin (bacteriophage) causes hemolytic-uremic syndrome: triad of anemia, thrombocytopenia, and acute renal failure → mechanical hemolysis, platelet consumption, ↓ renal blood flow
• Klebsiella Gram ⊝ rod. - Polysaccharide capsule.- Reservoir: human colon and upper respiratory tract. - Mucoid, lactose-fermenting colonies on MacConkey agar.- Dark red "current jelly" sputum (blood/mucus) - Pneumonia: Community-acquired, most often older males, most commonly those with chronic lung disease, alcoholism, or diabetes. Often aspirated.- Nosocomial UTI: from fecal contamination of catheters- Septicemia: in immunocompromised patients, may originate from bowel defect - Associated with evolution of multidrug resistance (MDR). Treatment: 3rd generation cephalosporin, fluorochinolones
• Campylobacter jejuni Gram ⊝, oxidase ⊕. Comma-shaped rod with polar flagella. Grows at 42°C.- Reservoir: Intestinal tracts of humans, cattle, sheep, dogs, cats, poultry- Transmission: Fecal-oral transmission through person-to-person contact or via ingestion of undercooked poultry or meat Disease:- Major cause of bloody diarrhea, especially in children- ≥10 stools/day- Abdominal pain, fever, malaise, nausea, and vomiting- Generally self-limiting in 3-5 days Complications: antecedent to Guillain-Barré syndrome (ascending muscle weakness) and reactive arthritis 
• Clostridium tetani Gram-⊕, spore-forming, obligate anaerobic rods.- Produces tetanospasmin- Ubiquitous (especially animal feces and soil) - Wounds with compromising blood supply create anaerobic conditions that are ideal for the multiplication and germination of C tetani, eg, penetrating wounds (gunshot, animal bites), open fractures, surgical procedures, burns, umbilical stump infections. - Tetanus toxin: protease that cleaves SNARE proteins for neurotransmitters. Blocks release of inhibitory neurotransmitters (GABA and glycine) from Renshaw cells in spinal cord. Causes:- Initially headache and flu-like symptoms - Spastic paralysis that begin in face muscles and descend: trismus (lockjaw), risus sardinocus (raised eyebrows and open grin), opisthotonus (spasms of spinal extensors).- Laryngospasm → respiratory failure- Autonomic dysfunction → circulatory arrest and shock - Tetanus is a clinical diagnosis. - Prevent with tetanus vaccine.- Treat with antitoxin +/- vaccine booster, antibiotics (metronidazole), diazepam (for muscle spasms), and wound debridement.
• Clostridium botulinum Gram-⊕, spore-forming, obligate anaerobic rod. - Produces a heat-labile toxin that inhibits ACh release at the neuromuscular junction, causing botulism. - In adults, disease is caused by ingestion of preformed toxin. - In babies, ingestion of spores (eg, in honey) leads to desease (floppy baby syndrome). Symptoms: - Descending paralysis: diplopia, dysarthria, dysphagia, dyspnea.- Autonomic nervous system: Xerostomia Treat with human botulinum immunoglobulin.
• Clostridium perfringens Gram-⊕, spore-forming, obligate anaerobic rod.- Ubiquitous - Wounds with compromised blood supply create an anaerobic environment → optimal for the proliferation of C perfringens → necrosis progresses within 24-36 hours. Such wounds include deep, penetrating wounds (eg, gunshot, knife), open fractures, septic surgical wounds. - Produces α toxin (lecithinase, a phospholipase) that can cause myonecrosis (gas gangrene; presents as soft tissue crepitus) and hemolysis.- Spores can survive in undercooked food; when ingested, bacteria release heat-labile enterotoxin → food poisoning. Symptoms:- Excruciating muscle pain- Massive edema with bronze → black skin discoloration and overlying bullae- Sweet, foul-smelling, or nonodorous discharge- Crepitus- Systemic symptoms: fever, tachycardia, altered mental status, shock, multi-organ failure Differential:- Necrotizing enterocolitis: No crepitus, differentiate with culture- Vibrio vulnificus infection: Wound is exposed to seawater; gram-stain to distinguish Treatment: Debridement and antibiotics (penicillin + clindamycin/tetracycline)
• Clostridium difficile Gram-⊕, spore-forming, obligate anaerobic rod. Produces 2 toxins:- Toxin A, an enterotoxin, binds to the brush border of the gut and alters fluid secretion.- Toxin B, a cytotoxin, causes cytoskeletal disruption via actin depolymerization.Both toxins lead to diarrhea → pseudomembranous colitis. - Often 2° to antibiotic use, especially clindamycin or ampicillin; associated with PPIs. - Can occur as late as 10 weeks after treatment. - Diagnosed by PCR or antigen detection (EIA for glutamate dehydrogenase antigen) of one or both toxins in stool.- Abdominal x-ray/CT: detection of toxic megacolon, abscesses, perforation, pseudomembranous colitis. Treatment: oral vancomycin (1st line), metronidazole- For recurrent cases, consider repeating prior regimen, fidaxomicin (macrocyclic antibiotic that inhibits the sigma subunit of RNA polymerase), or fecal microbiota transplant.Control measures: Gloves and protection gown; mask not necessary. Wash hands with soap because spores are resistant to alcoholic disinfectants.
• Vibrio cholerae Gram ⊝, flagellated, oxidase ⊕, grows in alkaline media.- Endemic to developing countries.- Transmitted via ingestion of contaminated water or uncooked food (eg, raw shellfish). - Fecal-oral spread; sensitive to stomach acid (acid labile), requires large inoculum (high ID50) unless host has ↓ gastric acidity.- Produces profuse rice-water diarrhea (white flecks of mucus) via enterotoxin that permanently activates Gs, ↑ cAMP → efflux of Cl- and H2O. (Similar to E coli heat-labile toxin)- Fever is rare because V cholerae is noninvasive. Diagnosis: Culture stool on TCBS Treatment: Prompt oral rehydration is necessary
• Yersinia enterocolitica Gram ⊝ coccobaccili. Lactose non-fermenter. Oxidase ⊝. Reservoir: ZoonoticTransmission: Pet feces (eg, puppies), contaminated milk, pork- Prominent in cold, northern climates (Michigan, Scandinavia) Presentation:- Acute diarrhea (may be bloody in severe cases)- Pseudoappendicitis: right lower abdominal pain due to mesenteric adenitis and/or terminal ileitis. Diagnosis: Stool culture, 25˚C, cold enrichment
• Helicobacter pylori Gram ⊝, curved, flagellated (motile), triple ⊕: catalase ⊕, oxidase ⊕, urease ⊕- Urease produces ammonia, creating an alkaline environment, which helps H pylori survive in acidic mucosa.- Colonizes mainly antrum of the stomach - Causes gastritis and peptic ulcers (especially duodenal)- Risk factor for peptic ulcer disease, gastric adenocarcinoma, and MALT lymphoma, B-cell lymphomas Diagnosis: - Biopsy with culture, histology with Giemsa or silver stain. - Urea breath test: 13C-urea swallowed; ammonia+13C-CO2 exhaled- Serology Treatment:- Triple therapy: Amoxicillin (metronidazole if penicillin allergy) + clarithromycin + PPI for 10-14 days- Quadruple therapy where clarithromycin resistance is ≥15%, eg, PPI + bismuth + metronidazole + tetracycline
• Spirochetes Spiral-shaped bacteria with axial filaments. - Borrelia: only spirochete visible in light microscopy due to big size; aniline dyes (Wright or Giemsa stain) - Leptospira - Treponema: dark-field microscopy or direct fluorescent antibody (DFA) microscopy
• Leptospira interrogans Spirochete with hook-shaped ends.- Zoonosis. - Found in water contaminated with animal urine.- Prevalent among surfers and in tropics (eg, Hawaii). Leptospirosis- Flu-like symptoms - Myalgias (classically of calves)- Jaundice- Photophobia with conjunctival suffusion (erythema without exudate) Weil disease (icterohemorrhagic leptospirosis)- Severe form with jaundice and azotemia- Liver and kidney dysfunction- Pulmonary hemorrhage → hemoptysis Diagnosis: Serodiagnosis (agglutination test), culture (blood CSF, urine) Treatment: Penicillin G or doxycycline
• Lyme disease - Caused by Borellia burgdorferi, an anaerobe facultative intracellular spirochete, which is transmitted by the Ixodes deer tick- Natural reservoir is the mouse- Common in northeastern United States Stage 1 – early localized: erythema migrans (typical "bulls-eye" configuration), flu-like symptoms Stage 2 – early disseminated: secondary lesions, carditis, AV block, facial nerve (Bell) palsy, migratory myalgias/transient arthritis Stage 3 – late disseminated: encephalopathies, chronic arthritis Diagnosis: ELISA, confirmatory with Western Treatment: Doxycyclin (1st line); amoxicillin and cefuroxime (2nd generation cephalosporin) in pregnant women and children.
• Syphilis - Caused by spirochete Treponema pallidum Primary syphilis: Painless chancre. VDRL ⊕ in 80%, dark-field microscopy. Secondary syphilis: Maculopapular rash (including palms and soles), condylomata lata (smooth, moist, painless, wart-like white lesions on genitals), lymphadenopathy, patchy hair loss. Serologic testing: VDRL/RPR (nonspecific), confirm diagnosis with specific test (FTA-ABS). Latent syphilis (⊕ serology without symptoms) may follow. Tertiary syphilis: Gummas (chronic granulomas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis), Argyll Robertson pupil (constricts with accommodation but is not reactive to light; also called "prostitute's pupil"). Signs: broad-based ataxia, ⊕ Romberg, Charcot joint, stroke without hypertension. Congenital syphilis: Facial abnormalitis with rhagades (linear scars at angle of mouth), snuffles (nasal discharge), saddle nose, notched (Hutchinson) teeth, mulberry molars, and short maxilla; saber shins; CN VIII deafness. Placental transmission typically occurs after first trimester.
• Congenital syphilis - facial abnormalities such as rhagades (linear scars at angle of mouth), snuffles (nasal discharge), notched (Hutchinson) teeth, deafness - To prevent, treat mother early in pregnancy, as placental transmission typically occurs after first trimester
• VDRL false positives - VDRL detects nonspecific antibody that reacts with beef cardiolipin. - Widely available test for syphilis, quantitative, sensitive but not specific. False-positive results on VDRL with:V: Viral infection (eg, EBV, hepatitis)D: DrugsR: Rheumatic feverL: Lupus and leprosy- Pregnancy
• Jarisch-Herxheimer reaction Flu-like syndrome (fever, chills, headache, myalgia) after antibiotics are started. Due to killed bacteria (usually spirochetes: Borrelia, Leptospira, Treponema) releasing toxins.
• Gardnerella vaginalis Pleomorphic, gram-variable rods. Catalase and oxidase negative. - Involved in bacterial vaginosis (excessive growth of certain anaerobic bacteria in vagina). - Thin, gray vaginal discharge with a fishy smell; nonpainful (vs vaginitis). Not itchy.- Amine whiff test – mixing discharge with 10% KOH enhances fishy odor. - Associated with sexual activity, but not sexually transmitted - Clue cells (vaginal epithelial cells covered with Gardnerella) have stippled appearance along outer margin. - Treatment: metronidazole or clindamycin
• Q fever Zoonosis caused by Coxiella burnetti, no arthropod vector - Spores inhaled as aerosols from cattle/sheep amniotic fluid, animal waste Acute Q fever:- Nonfebrile illness with fever lasting >10 days- Fatigue, myalgia- Severe headaches, which are often retroorbital and associated with photophobic- Pneumonia, most common x-ray abnormalitiy is lobar consolidation Chronic Q fever: often lethal- Most common cause of culture Θ endocarditis in patients with valvular disease Labs: - Leukocyte count is often normal- Increased liver enzymes- Thrombocytopenia
• Rickettsial diseases Rocky Mountain spotted fever- Rickettsia rickettsii, vector is Dermacentor (dog tick)- Occurs primarily on the East Coast (esp. North Carolina)- Rash typically starts at wrists and ankles and then spreads to trunk, palms, and soles.- Classic triad: 1. Headache, 2. Fever (102˚F), 3. Rash (vasculitis) (Palms and soles rash is seen in Coxsackievirus A infection, RMSF, and 2° syphilis) Typhus:- Endemic (cat and rat fleas) - R typhi- Epidemic (human body louse) - R prowazekii- Rash starts centrally and spreads out, sparing palms and soles Diagnosis: Serology, positive Weil-Felix reaction Therapy: Doxycycline
• Chlamydiae Obligate intracellular organisms (cannot make their own ATP) with lack of peptidoglycan (muramic acid) in cell wall. Chlamydia trachomatisTypes A, B, C: chronic infection, blindness due to follicular conjunctivitis in Africa (trachoma)Types D-K: Urethritis/PID, reactive arthritis, ectopic pregnancy, neonatal pneumonia (staccato cough) with eosinophilia, neonatal conjunctivitis (1-2 weeks after birth); can be acquired during passage through birth canal.Types L1, L2, L3: Lymphogranuloma venereum – small, painless ulcers on genitals → swollen, painful inguinal lymph nodes that ulcerate (buboes).  Chlamydia pneumoniae and Chlamydia psittaci- Atypical pnemonia- Transmitted by aerosol 2 forms:- Elementary body (small dense), enters cell via endocytosis; transforms into reticulate body.- Reticulate body replicates in cell by fission; reorganizes into elementary bodies. Lab diagnosis: PCR, nucleic acid amplification test. Cytoplasmic inclusions (reticulate bodies) seen on Giemsa or fluorescent antibody-stained smear. - Treatment: azithromycin (macrolid, favored because one-time treatment) or doxycycline (+ ceftriazone for possible concomitant gonorrhea)
• Mycoplasma pneumoniae Pleomorphic, microaerophile, no cell wall (contains sterols for stability). Not seen on Gram stain.- Frequent outbreaks in military recruits and prisons, <30 years old. - Classic cause of "walking" atypical pneumonia (insidious onset, headache, nonproductive cough, sweating, diffuse interstitial infiltrate) - X-ray looks worse than patient- Attaches to respiratory epithelium using surface antigens (I-antigen) that are also present on the plasma membrane of erythrocytes.- High titer of cold agglutinins (IgM), which can agglutinate or lyse RBCs- Grown on Eaton agar Treatment: macrolides, doxycycline, fluoroquinolone (penicillin ineffective since no cell wall).
• Systemic mycoses All can cause pneumonia and can disseminate.All are caused by dimorphic fungi: cold (20°C) = mold; heat (37°C) = yeast. Only exception is Coccidioides, which is a spherule (not yeast in tissue).Systemic mycoses can form granulomas (like TV); cannot be transmitted person-to-person.- Treatment: fluconazole/itraconazole for local infection; amphotericin B for systemic infection. Histoplasmosis: Dimorphic fungi with septate hyphae- Mississippi and Ohio River Valleys- Bird (eg, starlings) or bat droppings- Palatal/tongue ulcers, splenomegaly- Macrophage filled with Histoplasma (smaller than RBC)- Diagnosis via urine/serum antigen.  Blastomycosis: Broad-based budding- Eastern and Central US.- Inflammatory lung disease, can disseminate to skin/bone. - Verrucous skin lesions can simulate squamous cell carcinoma.- Forms granulomatous nodules. Coccidioidomycosis: Spherule filled with endospores- Southwestern United States, California.- Causes pneumonia and meningitis, disseminates to skin/bone.- Erythema nodosum (desert bumps) or multiforme.- Arthralgias (desert rheumatism). Paracoccidioidomycosis: Budding yeast with "captain's wheel" formation- Latin America- Similar to blastomycosis, males > females
• Candida albicans Dimorphic; forms pseudohyphae and budding yeasts at 20°C, germ tubes (true hyphae) at 37°C serum. Forms pseudohyphae when it invades tissues. This test helps differentiate C albicans from other Candida species. - Oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS)- Perlèche: crevices of mouth/malnutrition- Vulvovaginitis (diabetes, use of antibiotics)- Diaper rash- Endocarditis (IV users)- Disseminated candidiasis Treatment: - Vaginal: oral fluconazole/topical azole- Oral: Nystatin, fluconazole, or echinocandins- Systemic: fluconazole, echinocandines, amphotericin B 
• Aspergillus fumigatus Monomorphic septate hyphae that branch at 45°. Produces conidia in radiating chains at the end of conidiophore (like broccoli). - Causes invasive aspergillosis in pre-existing lung cavities, especially after TB infection, in immunocompromised patients, neutrophil dysfunction (eg, chronic granulomatous disease). - Some species produce aflatoxins, which are associated with hepatocellular carcinoma. Allergic bronchopulmonary aspergillosis (ABPA) – hypersensitivity response associated with asthma and cystic fibrosis; may cause bronchiectasis and eosinophilia.
• Cryptococcus neoformans - Opportunistic infection in patients with CD4 <100/mm3.- 5-10 µm round/oval cells with narrow-based budding. Heavily encapsulated yeast with a polysaccharide capsule. Not dimorphic (grows as a yeast in cold and hot temperatures). - Found in soil, pigeon dumpings.- Acquired through inhalation with hematogenous dissemination to meninges.- Culture on Sabouraud agar. Highlighted with India ink (clear halo) and mucicarmine (red inner capsule)- Latex agglutination detects polysaccharide capsular antigen and is more specific. - Causes cryptococcosis, cryptococcal meningitis, cryptococcal encephalitis ("soap bubble" lesions in brain), primarily in immunocompromised. Treatment: Amphotericin B + flucytosine followed by fluconazole for cryptococcal meningitis.
• Pneumocystis jirovecii Causes Pneumocystis pneumonia (PCP), a diffuse interstitial pneumonia.- Yeast-like fungus.- Most infections are asymptomatic.- Immunosuppression (eg, AIDS) predisposes to disease. - Diffuse, bilateral ground-glass opacities on CXR/CT, with pneumatoceles. - Diagnosed by lung biopsy or lavage.- Disc-shaped yeast seen on methanamine silver stain of lung tissue. - Treatment: TMP-SMX, pentamidine, dapsone (prophylaxis only), atovaquone.- Start prophylaxis when CD4+ count drops to <200 cells/mm3 in HIV patients.
• Sporothrix schenckii Dimorphic, cigar-shaped budding yeast that grows in branching hyphae with rosettes of conidia; lives on vegetation.- Spores are traumatically introduced into the skin, typically by a thorn ("rose gardener's disease") Sporotrichosis:- Local pustule or ulcer with ascending lymphangitis.- Disseminated disease possible in immunocompromised host. Treatment: itroconazol or potassium iodide Think of a rose gardener who smokes a cigar and pot.
• Toxoplasma gondii Protazoa. - Immunocompetent: mononucleosis-like symptoms, ⊝ heterophile antibody test.- Reactivation in AIDS → brain abscesses usually seen as multiple ring-enhancing lesions on MRI.- Congenital toxoplasmosis: triad of chorioretinitis, hydrocephalus, and intracranial calcifications.  - Transmission: Cysts in meat; oocytes in cat feces; crosses placenta Diagnosis: Serology, biopsy (tachyzoite) Treatment: Sulfadiazine + pyrimethamine
• Trypanosoma cruzi Chagas disease – dilated cardiomyopathy with apical atrophy, megacolon, megaesophagus, achalasia.- Acute stage: Romaña sign (unilateral periorbital swelling). - Predominantly in South America- Transmission: Reduviid bug ("kissing") bug, deposits feces in a painless bite Diagnosis: Trypomastigote in blood smear Therapy: Benznidazole or nifurtimox (cruzing in my Benz, with a fur coat on)
• Giardia lamblia Protazoa.Intestinal flagellate that exists in 2 forms: a trophozoite (pathogenic stage) or a cyst (infective stage). - The trophozoite is a bilaterally symmetric, pear-shaped oragnism with multiple flagella and 2 nuclei (owl's eyes appearance)- The cysts are oval and contain up to 4 nuclei.- Transmission: Cysts in water by drinking contaminated water (eg, campers, travelers). Giardiasis – bloating, flatulence, foul-smelling, fatty diarrhea  - Multinucleated trophozoites or cysts in stool, antigen detection.- Small-bowel biopsy can show varying degrees of villus atrophy and crypt hyperplasia. - Treatment: Metronidazole - Children with IgA deficieny, X-linked agammagloulinemia, and CVID have a predisposition to chronic giardiasis.

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