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Term 3/4 Flash Cards > Micro Pre-Midterm > Flashcards

Micro Pre-Midterm Flashcards

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1
Q

Gram-positive cells

A

Positively blue! 2 layers:

  1. inner cytoplasmic mem;
  2. outer thick peptidoglycan layer (60-100%)

Low lipid content; NO endotoxin; NO periplasmic space; NO porin channel; vulnerable to lysozyme and penicillin attack

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2
Q

Streptococcus

A

Gram-pos. Form strips of cocci. Microaerophilic (some species of streptococci are facultative anaerobes)

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3
Q

Enterococcus

A

Gram-pos. Form strips of cocci. Microaerophilic

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4
Q

Staphylococcus

A

Gram-pos. Form clusters of cocci. Facultative anaerobes.

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5
Q

Bacillus

A

Gram-pos. Bacilli/rod. Produces spores

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6
Q

Clostridium

A

Gram-pos. Bacilli/rod. Produces spores. Obligate anaerobes.

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7
Q

Corynebacterium

A

Gram-pos. Bacilli/rod. NO SPORES

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8
Q

Listeria

A

Gram-pos. Bacilli/rod. NO SPORES. Facultative anaerobes.

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9
Q

Gram-negative cells

A

Red is negative! 3 layers:

  1. inner cytoplasmic mem
  2. thin peptidoglycan layer (5-10% peptidoglycan)
  3. outer mem w/LPS

High lipid content; endotoxin (LPS) - lipid A; periplasmic space; porin channel; resistant to lysozyme and penicillin attack

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10
Q

Neisseria

A

Gram-neg. Diplococcus (looks like 2 coffee beans kissing)

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11
Q

Spirochetes

A

Gram-neg. Spiral. NOTE: have addtn’l phospholipid-rich outer mem w/few exposed proteins -> protection from immune recog.

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12
Q

Mycoplasma

A

NO CELL WALL! Only have simple cell mem, so neither gram-pos or gram-neg

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13
Q

Nocardia

A

Obligate aerobes. Weakly acid-fast.

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13
Q

Bacillus cereus (reservoir, transmission, metab, virulence, clinical, tx, dx)

A

Transmission - endospores

Metab - aerobic

Virulence - 1. NO capsule, 2. motile

Clinical - food poisoning: nausea, vomiting and diarrhea

Tx: 1. vancomycin, 2. clindamycin, 3. resistant to beta-lactam abx, 4. no txt for food poisoning (Be serious, Dr. Goofball, food poisoning is caused by pre-formed enterotoxin)

Dx - culture specimen from suspected food source

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14
Q

Bacillus cereus

A

Gram-pos. Bacilli/rod. Produces spores. Obligate aerobes.

Food poisoning enterotoxin - heat stable toxin

Dz: 1. vomiting that lasts for less than 24 hrs
2. limited diarrhea

Note: 1. B. cereus endospores survive low temp cooking. Then, this bacterium grows and deposits this toxin on food
2. B. cereus can also produce food poisoning by secretion of a heat labile enterotoxin (similar to that of E. coli)

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15
Q

Bacillus anthracis

A

Gram-pos. Bacilli/rod. Produces spores. Facultative anaerobes

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16
Q

Bacillus anthracis (reservoir, transmission, metab, virulence, clinical, tx, dx)

A

Reservoir: Herbivores (zoonotic): sheep, goats, cattle

Transmission: endospores - 1. cutaneous, 2. inhalation, 3. ingestion

Metab - aerobic (can grow w/out O2 -> classified as facultative anaerobe)

Virulence - 1. Unique prot capsule (polymer of gamma-D-glutamic acid): antiphagocytic

  1. Non-motile
  2. Virulence depends on acquiring 2 plasmids. One carries the gene for the protein capsule; the other carries the gene for its exotoxin (PA, EF, LF)

Clinical: anthrax 1. cutaneous (95%) - painless black vesicles; can be fatal if untx’ed

  1. Pulmonary (woolsorter’s dz)
  2. GI: abdominal pain, vomiting, and bloody diarrhea -> infxn results in perm immunity (if pt survives)

Tx: 1. ciprofloxacin, 2. doxycycline, 3. vaccine for high-risk people (vaccine is composed of PA. Animal vaccine is composed of live strain, attenuated by loss of its protein capsule)

Dx: 1. Gram stain, 2. culture, 3. serology, PCR of nasal swab

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17
Q

Bacillus anthracis (miscellaneous exotoxins)

A

Misc exotoxins: anthrax toxin (edema factor/EF, lethal factor/LF, protective antigen/PA)

Mech: 1. PA - binding B subunit, which allows entry of EF into cell

  1. EF - (A subunit). Calmodulin-dependent AC increases cAMP, which impairs neutrophil fxn and causes massive edema (disrupts water homeostasis)
  2. LF - zinc MMP that inactivates protein kinase. This toxin stimulates macrophage to release TNF-a and IL-1B, which contributes to death in anthrax

Dz: anthrax. EF -> an EC AC that gets internalized by “defensive” phagocytic cells. AC is activated by calmodulin, increasing cAMP conc w/in neutro and macs -> this inhibs their ability to phagocytose bacteria.

Notes: 1. All 3 components needed for toxin activity. 2. PA is the B (action) subunit and EF is the A (binding) subunit of anthrax toxin

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18
Q

Actinomyces

A

Gram-pos. Facultative anaerobes

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19
Q

Pseudomonas

A

Gram-neg. Obligate aerobes

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20
Q

Bordetella

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A

Gram-neg. Obligate aerobes

21
Q

Legionella

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A

Gram-neg. Obligate aerobes

22
Q

Brucella

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A

Gram-neg. Obligate aerobes

23
Q

Spirochetes Treponema

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A

Gram-neg. Microaerophilic

24
Spirochetes Borrelia
Gram-neg. Microaerophilic
25
Spirochetes Leptospira
Gram-neg. Microaerophilic
26
Campylobacter
Gram-neg. Microaerophilic
27
Bacteroides
Gram-neg. Obligate anaerobes
28
Mycobacterium
Acid-fast. Obligate aerobes
29
Facultative intracellular organisms
1. Listeria monocytogenes 2. Salmonella typhi 3. Yersinia 4. Francisella tularensis 5. Brucella 6. Legionella 7. Mycobacterium Listen Sally Yer Friend Bruce Must Leave
30
Clostridium tetani (reservoir, transmission, metab, virulence, clinical, tx, dx)
Reservoir: soil Transmission: endospores: introduced through wound Metab: anaerobic Virulence: motile: flagella (so H-Ag pos) Toxins: tetanospasmin - inhibs release of GABA and glycine from nerve cells -> sustained mm contraction Clinical: tetanus - 1. muscle spasms, 2. lockjaw (trismus), 3. risus sardonicus, 4. resp mm paralysis Tx: 1. Tetanus toxoid - vaccination w/formaline-inactivaed toxin (toxoid). Part of DPT vaccine 2. Antitoxin - human tetanus Ig 3. Clean wound 4. Penicillin 5. Supportive therapy - may require ventilatory assistance Dx: 1. Gram stain - gram-pos rods, often w/endospore at one end (drumstick) 2. Culture: requires ANAEROBIC conditions
31
Clostridium tetani
Neurotoxin - tetanospasmin (tetanus toxin) Mech - 1. H subunit - binds to neuronal gangliosides 2. L subunit - blocks release of inhib NTs (glycine, GABA) from Renshaw inhib interneurons Dz: tetanus - continuous motor neuron activity. Unctrl'ed mm contractions w/lockjaw and tetanic paralysis of resp mm Notes - 1. vaccine - formalin-inactivated tetanus toxin (DPT) 2. Toxin gene carried on plasmid
32
Clostridium botulinum
Neurotoxin - botulinum toxin Mech - inhibs ACh release from motor neuron endplates at NMJs Dz: botulism - flaccid paralysis w/resp mm paralysis Notes - 1. most potent exotoxin 2. Toxin obtained by lysogenic conversion
33
Clostridium botulinum ((reservoir, transmission, metab, virulence, clinical, tx, dx)
Reservoir - soil, stored vegetables (home-canned, zip-lock storage bags), smoked fish, fresh honey (associated w/infant botulism) Transmission - endospores (heat resistant) Metab - anaerobic Virulence - motile: flagella (so H-Ag positive) Toxins - 1. neurotoxin: inhibs release of ACh from peripheral nn 2. Toxin is not secreted; rather it is released upon death of bacterium Clinical - food-borne botulism - cranial nn palsies, mm wkness, resp paralysis Infant botulism - constipation, flaccid paralysis Wound botulism - similar to food-borne except absence of GI prodromal sx's Tx: 1. antitoxin (for food-borne and wound) 2. human botulism Ig (for infant) 3. penicillin 4. hyperbaric O2 5. supportive therapy, including incubation and ventilatory assistance Dx: 1. Gram stain, 2. culture - requires ANAEROBIC conditions, 3. pt's serum inj into mice results in death
34
Staphylococcus aureus
Food poisoning enterotoxin - staphylococcal heat stable toxin. Dz: diarrhea and vomiting that lasts for less than 24 hrs. Note: toxins are deposited on food colonized w/toxin-producing Staphylococcus
35
Vibrio cholerae
Infections diarrhea enterotoxin: choleragen Mech: 1. Five B subunits: binds to GM1 gangliosides on intestinal cell mems 2. Two A subunits: carry out the ADP-ribosylation of the GTP-binding protein. This activates mem-assoc AC, converting ATP to cAMP. High cAMP induces secretion of NaCl and inhibs reabs of NaCl. Dz: cholera - increasing cAMP levels result in increased intraluminal NaCl -> osmotically pulls fluid and electrolytes into the intestinal tract -> diarrhea and dehydration Note: death by dehydration
36
1. E. coli 2. Campylobacter jejuni 3. Bacillus cereus
Infectious diarrhea enterotoxin - E. coli heat labile toxin (LT). Structurally similar to choleragen Mech: 1. Five B subunits: binds to GM1 gangliosides on intestinal cell mems 2. Two A subunits: carry out the ADP-ribosylation of the GTP-binding protein. This activates mem-assoc AC, converting ATP to cAMP. High cAMP induces secretion of NaCl and inhibs reabs of NaCl. Dz: cholera - increasing cAMP levels result in increased intraluminal NaCl -> osmotically pulls fluid and electrolytes into the intestinal tract -> diarrhea and dehydration Note: death by dehydration
37
1. E. coli | 2. Y enterocolitica
Infectious diarrhea enterotoxin - E. coli heat stable toxin (ST) Mech: no effect on conc of cAMP. Rather, it binds to rec on intestinal brush border and activates GC to make GMP. Results in inhib of resorption of NaCl. Dz: increasing cGMP inhibs NaCl resorption by intestinal epithelial cells -> increased osmotic pull of fluid and electrolytes into the intestinal tract, causing diarrhea
38
1. Shigella dysenteriae 2. Enterohemorrhagic E. coli 3. Enteroinvasive E. coli
Infectious diarrhea enterotoxins: 1. Shiga toxin, 2. Shiga-like toxin (when "shiga-toxin" is released by bacteria other than shigella) Mech: 1. Five B subunits: bind to intestinal epi cells 2. A subunit: inhibs protein syn by inactivating the 60S ribosomal subunit -> kills intestinal epithelial cells Dz: Shiga toxin kills absorptive intestinal epi cells, resulting in sloughing off of dead cells and poor absorption of fluid and electrolytes from intestinal tract Notes: 1. bloody diarrhea 2. may be responsible for hemolytic uremic sx 3. inhibs prot syn in a manner like the antiribosomal abx (erythromycin, tetracycline, etc.)
39
Streptococcus pyogenes (Grp A streptococci)
Pyrogenic toxin: Streptococcus pyrogenic toxin Mech: activates endogenous mediators of sepsis, such as IL-1 Dz: scarlet fever Notes: obtains exotoxin from temperate bacteriophage by lysogenic conversion
40
Streptococcus pyogenes
Tissue invasive toxins: 1. Hemolysins/streptolysin O and S; 2. streptokinase; 3. DNAases; 4. hyaluronidase; 5. NADase Mech: 1. lyses RBCs; 2. activates plasminogen to lyse fibrin clots; 3. hydrolyzes DNA; 4. breaks down proteoglycans; 5. hydrolyzes NAD Dz: tissue destruction - 1. abscesses; 2. skin infxns; 3. systemic infxn
41
Staphylococcus aureus (pyrogenic)
Pyrogenic toxins: TSST-1 Mech: activates the endogenous mediators of sepsis, such as IL-1 Dz: TSS - fever, rash, desquamation, diarrhea, hypotension (shock) Note: Streptococcus pyogenes can also cause TSS
42
Staphylococcus aureus (tissue invasive toxins)
Tissue invasive toxins: 1. lipases; 2. penicillinase; 3. staphylokinase; 4. leukocidin; 5. exfoliatin; 6. factors that bind complement Mech: 1. hydrolyzes lipids; 2. destroys penicillins; 3. activates plasminogen; 4. lyses WBCs; 5. epithelial cell lyses;
43
Clostridium perfringens (reservoir, transmission, metab, virulence, clinical, tx, dx)
Reservoir: ubiquitous - 1. soil, 2. GI tract of humans and mammals Transmission: endospores Metab - anaerobic Virulence: NON-MOTILE Toxins: 1. Alpha toxin: lecithinase (splits lecithin into phosphocholine and diglyceride) 2. 11 other tissue destructive ends Clinical: gaseous gangrene - 1. cellulitis/wound infxn, 2. clostridial myonecrosis - fatal if untx'ed, 3. watery diarrhea - assoc w/food-borne ingestion Tx: 1. radical surgery (may require amputation), 2. penicillin, 3. hyperbaric O2 Dx: 1. Gram stain, 2. culture - requires ANAEROBIC conditions
44
Clostridium perfringens
Tissue invasive toxins: more than 12 lethal toxins, named by Greek letters. Alpha toxin (lecithinase) is the most imp and most lethal Mech: Alpha toxin hydroylyzes lecithin in cell mems -> cell death Dz: Tissue destruction and gas gangrene
45
Corynebacterium diphtheriae
Misc exotoxin - diphtheria toxin Mech: 1. B subunit: binds to heart and neural tissue 2. A subunit: ADP ribosylates elongation factor (EF2), thereby inhibiting translation of human mRNA into proteins Dz: diphtheria - 1. myocarditis (heart), 2. peripheral nerve palsies, 3. CNS effects Notes: 1. This exotoxin can be human abc, as it inhibs prot sun, just as tetracycline and erythromycin inhib prot syn in bacteria 2. Vaccine: formaline-treated diphtheria toxin - part of DPT vaccine 3. Obtains exotoxin from temperate bacteriophage by lysogenic conversion
46
Bordetella pertussis
Four toxins: 1. pertussis toxin: B subunit - binds to target cells. A subunit - activates mem G prots to activate mem-bound AC (increase cAMP) -> inhibs phagocytosis 2. Extracytoplasmic AC - similar to B. anthracis edema factor, which impairs chemotaxis and phagocytosis 3. Filamentous hemagglutinin; allows binding to ciliated epithelial cells 4. Tracheal cytotoxin - dmgs resp epi cells Dz: whooping cough Note: Vaccine - DPT
47
Clostridium dificile
Toxins - 1. Toxin A - causes fluid secretion and mucosa inflammation, leading to diarrhea 2. Toxin B - cytotoxic to colonic epi cells Dz: pseudomem enterocolitis - colonic inflam, w/pseudo-mem formation. Clinically: diarrhea (often bloody), fever, and abdominal pain Notes: abx-assoc diarrhea
48
Clostridium dificile (reservoir, transmission, metab, virulence, clinical, tx, dx)
Reservoir: 1. intestinal tract, 2. endospores found in hospitals and nursing homes Transmission: fecal-oral ingestion of endospores Metab: anaerobic Virulence: motile - flagella (so H-Ag pos) Toxins: 1. Toxin A - diarrhea. 2. Toxin B - cytotoxic to colonic epithelial cells Clinical: pseudomembranous enterocolitis - abx-assoc diarrhea Tx: 1. metronidazole, 2. oral vancomycin, 3. terminate use of responsible abc Dx: 1. immunoassay for C. difficile toxin, 2. examine colon w/colonoscopy
49
Pseudomonas aeruginosa
Toxin - Pseudomonas exotoxin A Mech: inhibs prot syn by inhibiting elongation factor 2 (EF2): same mech as diphtheria toxin Note: Diphtheria has same action as P. aeruginosa, but they have diff targets 1. Exotoxin A - liver 2. Diphtheria toxin - heart

Term 3/4 Flash Cards (7 decks)

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