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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

A

Gram-neg. Obligate aerobes

21
Q

Legionella

A

Gram-neg. Obligate aerobes

22
Q

Brucella

A

Gram-neg. Obligate aerobes

23
Q

Spirochetes Treponema

A

Gram-neg. Microaerophilic

24
Q

Spirochetes Borrelia

A

Gram-neg. Microaerophilic

25
Q

Spirochetes Leptospira

A

Gram-neg. Microaerophilic

26
Q

Campylobacter

A

Gram-neg. Microaerophilic

27
Q

Bacteroides

A

Gram-neg. Obligate anaerobes

28
Q

Mycobacterium

A

Acid-fast. Obligate aerobes

29
Q

Facultative intracellular organisms

A
  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
Q

Clostridium tetani (reservoir, transmission, metab, virulence, clinical, tx, dx)

A

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

  1. Antitoxin - human tetanus Ig
  2. Clean wound
  3. Penicillin
  4. 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
Q

Clostridium tetani

A

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
Q

Clostridium botulinum

A

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
Q

Clostridium botulinum ((reservoir, transmission, metab, virulence, clinical, tx, dx)

A

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)

  1. human botulism Ig (for infant)
  2. penicillin
  3. hyperbaric O2
  4. 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
Q

Staphylococcus aureus

A

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
Q

Vibrio cholerae

A

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
Q
  1. E. coli
  2. Campylobacter jejuni
  3. Bacillus cereus
A

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
Q
  1. E. coli

2. Y enterocolitica

A

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
Q
  1. Shigella dysenteriae
  2. Enterohemorrhagic E. coli
  3. Enteroinvasive E. coli
A

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

  1. may be responsible for hemolytic uremic sx
  2. inhibs prot syn in a manner like the antiribosomal abx (erythromycin, tetracycline, etc.)
39
Q

Streptococcus pyogenes (Grp A streptococci)

A

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
Q

Streptococcus pyogenes

A

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
Q

Staphylococcus aureus (pyrogenic)

A

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
Q

Staphylococcus aureus (tissue invasive toxins)

A

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
Q

Clostridium perfringens (reservoir, transmission, metab, virulence, clinical, tx, dx)

A

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
Q

Clostridium perfringens

A

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
Q

Corynebacterium diphtheriae

A

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

  1. Vaccine: formaline-treated diphtheria toxin - part of DPT vaccine
  2. Obtains exotoxin from temperate bacteriophage by lysogenic conversion
46
Q

Bordetella pertussis

A

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

  1. Extracytoplasmic AC - similar to B. anthracis edema factor, which impairs chemotaxis and phagocytosis
  2. Filamentous hemagglutinin; allows binding to ciliated epithelial cells
  3. Tracheal cytotoxin - dmgs resp epi cells

Dz: whooping cough

Note: Vaccine - DPT

47
Q

Clostridium dificile

A

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
Q

Clostridium dificile (reservoir, transmission, metab, virulence, clinical, tx, dx)

A

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
Q

Pseudomonas aeruginosa

A

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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