| Question | Answer |
| carbuncle | lateral and deep extension of S. aureus; several coalesced furuncles with several openings to the surface with discharging pus |
| abscess | central area of necrosis, infection with dead host cells and bacteria surrounded by reactive fibrosis |
| empyema | infection of thoracic cavity external to lung |
| erysipelas | infection of superficial skin with marked involvement of lymphatic vessels |
| exfoliatin | EC product of S. aureus responsible for intradermal splitting and necrosis seen with scalded skin syndrome (SSS) |
| furuncle | small abscess or boil; painful, indurated, erythematous and caused by S. aureus |
| impetigo | infection of the superficial layers of skin - epidermis and outer dermis |
| leucocidin | exotoxin of S. aureus that destroys PMN leukocytes (specifically Panton-Valentine leukocidin) |
| puerperal sepsis | bacteremia in mother following childbirth |
| shock | syndrome characterized by hypotension from systemic vasodilation |
| likely function of coagulase in S. aureus | makes it an invasive organism; allows it to wall off infection and stop blood supply thus inhibiting leukocyte entry into wound |
| function of protein A in S. aureus | bings IgG's Fc portion, allows bacteria to evade immune cells labeling it for phagocytosis |
| Name another Staphylococcus besides aureus that's resistant to methicillin | up to 98% of S. epidermidis and other coag neg spp. |
| Staphylococcus saprophyticus | the only coag neg Staphylococcus that is resistant to novobiocin disc on agar plates; causes 20-30% of symptomatic UTIs in young, sexually active females |
| L-pyrrolidonyl arylamidase (PYR) | diagnostic enzyme for Group A beta hemolytic strep (S. pyogenes) |
| important diagnostic tool to distinguish beta hemolytic strep bacteria apart | bacitracin resistance |
| M protein | major virulence factor within Streptococcus pyogenes; is antiphagocytic and allows them to bind to epithelial cells & keratinocytes; ~ 100 diff serotypes identified by M protein DNA sequencing |
| hyaluronate capsule | typical of group A beta hemolytic strep, barrier to complement components and binds CD44 on host tissues |
| methods of virulence for GABHS | M protein, EC matrix binding protein, hyaluronic acid capsule, Ig-binding protein, C5a peptidase, streptolysins, DNAases acting on lysed cells in pus, streptokinase, superantigens |
| streptokinase | GABHS - degrades clots by activating host plasminogens and allowing spread in tissues |
| name of GABHS proteases that degrade host and bacterial tissues | SpeA, -B and -C proteases |
| 2 important immune-mediated conditions caused by GABHS infection | acute post-streptococcal glomerulonephritis
acute rheumatic fever |
| tonsillopharyngitis/strep throat - mainly caused by this bacterial group | GABHS (sometimes groups C or G) |
| differences btwn TSS by S. aureus and GABHS | S. aureus - inapparent site of infection, lacks bacteremia and low fatality rate |
| description/mechanism of acute rheumatic fever | occurs 7-21 days post-strep infection of the PHARYNX; thought to be a cross-rxn to antibodies initially produced against Strep, affects heart and other tissues |
| signs of acute rheumatic fever | heart inflammation producing arrhythmias, polyarthritis, fever, skin abnormalities, choreiform movements |
| description/mechanism of acute poststreptococcal glomerulonephritis | occurs 7-21 days post-strep infection of either skin or pharynx; immune complexes to Strep antigens are deposited in glomerular subepithelium |
| signs of acute poststreptococcal glomerulonephritis | from simple proteinuria or microscopic hematuria to complete renal failure then death |
| mechanism of puerperal sepsis | GABHS (or GBBHMS) travel up vagina, invades endometrium and uterine lymphatics to cause bacteremia |
| the major virulence factor associated with GBBHS | type III capsule, allowing evasion of phagocytosis |
| abx of preference for treating GBBHS | PCN or ampicillin |
| environmental niche of GBBHS | vagina - causes many OB and neonatal infections |
| most prevalent causative agent of CAP | Streptococcus pneumoniae |
| niche of Strep pneumo | upper resp tract/oropharynx |
| 2 main spots Strep pneumoniae has specific adhesion factors for | NAG and 3-Gal disaccharides on epithelial cells; PAF in the plasma |
| phase variation - definition and example of bacteria that exhibits it | ability to up or downregulate adhesion factors in the cell wall according to the site of attachment or infection; pneumococci |
| 3 abx of choice for pneumococcal infection | PCN G, vanc and Rocephin |
| features on would look for when Gram-staining sputum for pneumococcal infection | GP, lancet or football-shaped diplococci, optochin-sensitive, alpha hemolytic |
| drug of choice to treat VRE | ampicillin |
| special features typical for growing Enterococcus | grow in presence of bile and 6.5% NaCl |
| niche of viridans Streptococci like species mutans, sanguis and salivarius | mouth, on surface of teeth and gums |
| name diseases from toxins of Clostridia: difficile, tetani, botulinum, perfringens | C-diff diarrhea (nosocomial usually)
tetanus - spastic neurological dz
perfringens - gas gangrene, necrotizing skin infections
botulism - paralyzing neurological dz |
| name diseases from toxins of Bacillus genus: cereus and anthracis | anthrax - non-hemolytic type
food-borne diarrhea, is hemolytic |
| 2 most medically important non spore-forming GP rods | Corynebacterium and Listeria (both are non-filamentous also) |
| the most likely people to be affected by anthrax spores | abbatoir or slaughterhouse workers who are exposed to the hides or meat of animals who were previously infected |
| 3 clinical syndromes that could result from anthrax spore intoxication | cutaneous - from open wounds, trauma
GI - from eating contaminated meat
inhalational - from inhaling aerosolized spores |
| 3 virulence factors of Bacillus anthracis | edema toxin, lethal toxin and protective antigen |
| B. anthracis virulence factors are A-B toxins | protective antigen - B
edema and lethal factor - A (EF = calmodulin-dependent adenylate cyclase = anti-inflammatory cytokines; LF = MAPK kinase that stops cell growth) |
| best abx to treat B. anthracis | doxycycline and cipro (if naturally occuring, PCN hopefully) |
| pneumococcus vaccines | 13-valent polysaccharide version for children
23-valent " " " adults |
| 2 types of illneses produced from B. cereus intoxication | emetic and diarrheal illness |
| Contrast the 2 syndromes from B. cereus intoxication | emetic - from heat-stable endotoxin, improperly heated fried rice, sx within 1-6 hours
diarrheal - heat-labile endotoxin, from ingesting spores in cream sauce, vegetative cells germinate in gut, sx in 12-24 hrs |
| Clostridium species/type associated with gas gangrene | perfringens type A (a in both gas and gangrene) |
| Clostridium species/type associated with necrotizing enterocolitis | perfringens type C (C in colitis) |
| How does C. perfringens gain access to soft tissues and skin? | usually through trauma/dirty wounds where clostridia were in soil or feces and contacted wound |
| T/F Inflammatory cells are usually intermixed with C. perfringens when looking at gas gangrene tissue histologically. | no, they release toxins to lyse WBCs = no inflammatory cells |
| method of contracting C. perfringens gastroenteritis/specific pathogenic substance | ingesting meat that was stored at high temps allows spores to germinate and release heat-labile enterotoxin once in the body |
| mechanism of action of C. difficile toxins | toxins A/B - combo of enterotoxin that causes massive fluid secretion and cytotoxin that causes death and sloughing of intestinal epithelium |
| possible deadly outcome of C. difficile diarrhea | toxic megacolon |
| abx of choice to kill any remaining C. tetani bacteria at site of infection in tetanus pt | metronidazole (NOT!! PCN) |
| functions of the two chain toxin of C. tetani | heavy - specific binding to GABA-containing inhibitory nerves
light - endopeptidase that cleaves synaptobrevin = no vesicle release |
| neurotoxin that causes tetanus | tetanospasmin |
| mechanism of C. botulinum toxin | has light chain endopeptidase that prevents ACh release from NMJ = flaccid paralysis |
| most typical circumstance in which person comes into contact with C. botulinum | home canned products, eating food that wasn't cooked well enough and heat-labile toxin persists |
| why no raw honey to infants? | infant botulism from possible clostridial spores in honey |
| tx for tetanus | equine antitoxin |
| how C. diphtheriae become virulent | by acquiring the diphtheria toxin from a lysogenic phage |
| niche of C. diphtheriae | resp tract and skin |
| mechanism of A-B toxin of diphtheroids | B binds cell surface, A ADP-ribosylates EF-2 (elongation-factor 2) effectively stopping eukaryotic protein synthesis |
| vaccines available? tetanus, botulism, diphtheria, C. difficile infection | tetanus - yes
botulism - no
diphtheria - yes
C. diff - no |
| cause of death from diphtheria | toxin-induced cell death of throat epithelium, formation of pseudomembranes, obstruction of throat and resp failure from inability to get air or diaphragm paralysis |
| primary route of infection of Listeria | fecal-contaminated foods like milk or queso fresco, even when properly refrigerated |
| abx of choice for Listeria | ampicillin, possibly also Bactrim for some isolates |
| Listeria's preferred method for growing in host | intracellularly, induces phagocytosis then escapes into cytoplasm to replicate |
| tests to differentiate btwn Listeria and Streptococci | Listeria - catalase +, beta-hemolytic
Streptococci - catalase -, all types of hemolysis |
| erysipelothrix | caused by Erysipelothrix rhusiopathiae - erysipelas-like rash on hands of fisherman/abattoirs |
| causes severe acne | Propionibacterium acnes |
| diseases caused by Listeria monocytogenes | meningitis or bacteremia in immunocompromised and neonates, most typically though self-limited diarrheal illness |
| psychrophilic | able to live in refrigerator temps |
