Pelvic inflammatory diseaseChlamydia trachomatis (subacute, often undiagnosed) and Neisseria gonorrhea (acute) - Cervical motion tenderness (chandelier sign), purulent cervical discharge - May include salpingitis, endometritis, ...
Nosocomial infectionsAspiration (2° to mental status, old age): polymicrobial gram -, often anaerobes- Right lower lobe infiltrate or right upper/middle lobe; purulent malodorous sputum Intravascular catheters: S aureus ...
Pleomorphic bacteriaNo cell wall - Chlamydia (Giemsa)- Rickettsia (Giemsa)- Mycoplasma (contain sterols, which do not Gram stain)- Anaplasma, Ehrlichia- Haemophilus
Type III secretion systemAlso known as "injectisome." Needle-like protein appendage facilitating direct delivery of toxins from certain gram ⊝ bacteria (eg, Pseudomonas, Salmonella, Shigella, E coli) to eukaryotic host cell. ...
Bacterial virulence factorsThese promote evasion of host immune response. Protein A: Binds Fc region of IgG. Prevents opsonization and phagocytosis.- Expressed by S aureus. IgA protease: Enzyme that cleaves IgA, allowing bacteria ...
TransformationCompetent bacteria can bind and import short pieces of environmental naked bacterial chromosomal DNA (from bacterial cell lysis). - The transfer and expression of newly transferred genes is called transformation. ...
Mycobacteria- Mycobacterium tuberculosis (TB, often resistant to multiple drugs)- M avium-intracellulare (causes disseminated, non-TB disease in AIDS; often resistant to multiple drugs). Prophylaxis with azithromycin ...
Neurocysticercosis- Ingestion of Taenia solium (pork tapeworm) eggs excreted in feces of human carriers. Presentation:- Common in Central & South America, sub-Saharan Africa, Asia- Prolonged incubation (months to years)- Seizures, ...
Bacterial exotoxinsBacillus anthracis- Edema factor: Increases cAMP concentration by acting as an adenylate cyclase, causing edema & phagocyte dysfunction- Lethal factor: Zinc-dependent protease that inhibits mitogen-activated ...
Actinomyces israeliiGram ⊕, anaerobic, non-acid fast, branching rod.- Normal flora of oral and female genital tract. Presentation:- Poor dental hygiene, oral surgery (tooth extraction), local tissue inflammation (tonsillitis), ...
Moraxella catarrhalisGram-negative diplococcus. Close relative of Neisseria. - Reservoir: nasopharynx- Transmission: respiratory droplets Diseases:- Otitis media- Sinusitis- Bronchitis and bronchopneumonia in elderly patients ...
Pasteurella multocidaSmall gram ⊝ coccobacillus; facultative anaerobic. Reservoir: Mouth of many animals, especially cats and dogsTransmission: Animal bites; particularly from cat bites Disease: Cellulitis with lymphadenitis ...
Vibrio parahaemolyticusReservoir: Marine life Transmission: Consumption of undercooked or raw seafood Presentation: Watery diarrhea with cramping and abdominal pain - Self-limiting- Life-threatening sepsis can occur in those ...
Klebsielle granulomatisTransmission: sexual contact Disease: Granuloma inguinale (Donovanosis)- small painless nodules that burst and ulcerate- beefy red painless genital ulcers that bleed readily on contact Diagnosis: Donovan ...
ProteusGram-Θ, highly motile/"swarming motility", non-lactose-fementing, urease-positive Proteus mirabilis (90% of infections), Proteus vulgaris Reservoir: human colon and environment Pathogenesis:- Urease ...
Eikenella corrodensGram-negative rods; bleach-like odor Reservoir: Human oropharynxTransmission: Human bites or fist fight injuries Disease: Cellulitis Treatment: 3rd generation cephalosporins, fluoroquinolones
Bactericides fragilisGram-negative rod. Anaerobic. Reservoir: Human colonTransmission: Endogenous from bowel defects Diseases:- Septicemia- Peritonitis (often mixed infections)- Abdominal abscess Treatment: Metronidazole, ...
Treponema pallidumThin spirochete with periplasmic flagella. Obligate pathogen. Pathogenesis: Endarteritis resulting in lesions. Primary (10 days to 3 months after exposure):- Nontender chancre; clearn, indurated edge; ...
Borrelia burgdorferiSpirochetes, microaerophilic Reservoir: white-footed mice (nymphs) and white-tailed deer (adult ticks)Transmission: By Ixodes (deer) ticks and nymphs Pathogenesis: Invades skin and spreads via the bloodstream ...
Chlamydia trachomatisObligate intracellular bacterium; cannot make ATP. Found in cells as replicating reticulate bodies. Inactive, extracellular elementary bodies. Not seen on Gram stain. Peptidoglycan layer lacks muramic ...
Ehrlichia chaffeensisGram-negative bacilli, obligate intracellular bacteria of mononuclear or granulocytic phagocytes.- Reservoir: white tail deer- Transmission: Bite of the lone star tick (Ambylomma) Disease:- Similar to ...
Phage-coded pathogenic factors- Cholera toxin - O antigen of Salmonella - Botulinum toxin - Erythrogenic exotoxins of Streptococcus pyogenes - Diphtheria toxin - Shiga toxin
Fungal morphologyHyphae = filamentous cellular units of molds and mushrooms- Nonseptate hyphae = Broad hyphae with irregular width, broad angle of branching, no cross walls (eg, Mucor, Rhizopus spp)- Septate hyphae = ...
NocardiaGram ⊕ rod (beading or branching), partially acid-fast, aerobic.- Ubiquitous in soil - Trasmission via spore inhalation or traumatic inoculation into skin- Immunocompromised or elderly patients Symptoms:- ...
Bacterial structuresFlagellum: Proteins. MotilityPilus/fimbria: Glycoprotein. Mediate adhesion of bacteria to cell surface; sex pilus forms during conjugation. Spore: Keratin-like coat; dipicolinic acid; peptidoglycan, DNA. ...
Catalase-positive organismsCatalase degrades H2O2 into H2O and bubbles of O2 before it can be converted to microbicidal products by the enzyme myeloperoxidase. People with chronic granulomatous disease (NADPH oxidase deficiency) ...
AnaerobesExamples include Clostridium, Bacteroides, Fusobacterium, and Actinomyces israelii. They lack catalase and/or superoxide dismutase and are thus susceptible to oxidative damage. Generally foul smelling ...
Encapsulated bacteria- Pseudomonas aeruginosa- Streptococcus pneumoniae- Haemophilus influenzae type b- Neisseria meningitidis- E coli- Salmonella- Klebsiella- Group B Strep Are opsonized, and then cleared by spleen.Their ...
Urease-positive organisms- Proteus- Cryptococcus- H pylori- Ureaplasma- Nocardia- Klebsiella- S epidermidis- S saphrophyticus Urease hydrolyzes urea to release ammonia and CO2 → ↑ pH. Predisposes to struvite (ammonium magnesium ...
Pigment-producing bacteriaActinomyces israelii – yellow "sulfur" granules, which are composed of filaments of bacteria. S aureus – yellow pigment. P aeruginosa – blue-green pigment (pyocyanin and pyoverdin). Serratia marcescens ...
In vivo biofilm-producing bacteriaS epidermidis – Catheter and prosthetic device infections Viridans streptococci (S mutans, S sanguinis) – Dental plaques, infective endocarditis P aeruginosa – Respiratory tree colonization in patients ...
ConjugatinoF+ x F-: F+ plasmid contains genes required for sex pilus and conjugation. Bacteria without this plasmid are termed F-. Sex pilus on F+ bacterium contacts F- bacterium. A single strand of plasmid DNA ...
TransductionGeneralized: A packaging "error." Lytic phage infects bacterium, leading to cleavage of bacterial DNA. Parts of bacterial chromosomal DNA may become packaged in phage capsid. Phage infects another bacterium, ...
TranspositionSegment of DNA (eg, transposon) that can "jump" (copy/excise and reinsert) from one location to another, can transfer genes from plasmid to chromosome and vice versa. This is a critical process in creating ...
Spore-forming bacteriaSome bacteria can form spores when nutrients are limited.Spores lack metabolic activity.Spores are highly resistant to heat and chemicals. Most autoclave to kill spores by steaming at 121°C for 15 minutes. ...
Main features of exotoxins and endotoxinsExotoxins:- Source: Certain species of gram ⊕ and gram ⊝ bacteria- Secreted from cell: Yes- Chemistry: Polypeptide- Location of genes: Plasmid or bacteriophage- Adverse effects: High (fatal dose ...
α-hemolytic bacteriaGram ⊕ cocci. Partial reduction of hemoglobin causes greenish or brownish color without clearing around growth on blood agar. - Streptococcus pneumoniae (catalase ⊝ and optochin sensitive)- Viridans ...
β-hemolytic bacteriaGram ⊕ cocci. Complete lysis of RBCs → clear area surrounding colony on blood agar. - Staphylococcus aureus (catalase and coagulase ⊕)- Streptococcus pyogenes – group A strep (catalase ⊝ ...
Lactose-fermenting enteric bacteriaFermentation of lactose → pink colonies on MacConkey agar. Fast-fermenters:- E coli- Klebsiella- Enterobacter Slow-fermenters:- Citrobacter- Serratia - E coli produces β-galactosidase, which breaks ...
Escherichia coliGram ⊝ rod, fast lactose-fermenter, indole ⊕ (ability to convert tryptophan to indole; distinguishes from Enterobacter cloacae). - Fimbriae – cystitis and pyelonephritis (P-pili)- K capsule – ...
Bartonella sppGram ⊝ rod, facultative intracellular, microaerophile. Bartonella henselae- Reservoir: Cats are asymptomatic carriers- Cat scratch disease: one or more 5-10mm large, erythematous, non-tender papules ...
Borrelia recurrentisTransmission via louse (recurrent due to variable surface antigens). Relapsing fever
Tinea (pityriasis) versicolorCaused by Malassezia spp, a yeast-like fungus (not a dermatophyte despite being called tinea). Degradation of lipids produces acids that damage melanocytes and cause hypopigmented, hyperpigmented, and/or ...
