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78 Cards in this Set

  • Front
  • Back
Steps of gram stain?
crystal violet
wash + iodine
decolarize with alcohol
counter with safranin
Color of gram + after gram stain?
Color of gram - after gram stain?
The layer ouside the bacterial cytoplasmic membrane?
Peptidoglycan Layer
Structure of Peptidoglycan Layer of bacteria?
repeating disaccharides with 4 aa side chains. cross link each other.
Mechanism of transpeptidase?
catalyzes the formation of the cross linkage of the peptidoglycan layer. Inhibited by penicillin.
Describe gram + cell envelope?
Outer cell wall of cross linked peptidoglycan, teichoic acid, polysaccharides
Describe gram - cell envelope?
1.cytoplasmic membrane
2.periplasmic space
3.extremely thin peptidoglycan layer (no teichoic acid, has murein lipoprotein binding 3rd layer)
4. outer cell membrane with LPS. Also contains porins.
What is structure of LPS?
1. Outer carb chain. the O antigen. differs with organisms.
2. core polysaccharide.
3. lipid A. (endotoxin)
Only gram+ with endotoxin?
Listeria Monocytogenes
Name 6 major gram + bugs with shape + spore formation?
1. Streptococcus
2. Staphylcoccus
3. Bacillus (spore forming rod)
4. Clostridium (spore forming rod)
5. Corynebacterium (rod)
6. Listeria (rod)
Only gram - cocci?
Gram - and spiral shaped?
Weakly gram + however need acid fast stain?
Gram - but too small for gram stain? use darkfield?
A bacteria with no cell wall?
What does bacterial DNA usually consists of?
single circle of DSDNA
Which ribosomes do bacteria use?
50S + 30S
How classify obligate aerobe?
use oxygen + have catalase, peroxidase + superoxide dismutase
How classify facultative anaerobes?
aerobic bacteria. Have catalase and superoxide dismutase. can be anaerobic but prefer aerobic.
How classify microaerophilic bacteria?
no electron transport chain. use fermentatino. have superoxide dismutase so tolerate low level oxygen.
Classify obligate anaerobe?
no enzmes against oxygen.
What is the only bacteria with a capsule made of amino acids?
Bacillus anthracis
What test is used primarily to identify cryptococcus?
India Ink Stain: not taken up by capsule appear as transparent halo around cell.
What is the Quellung reaction?
bacteria + their antibodies. capsule swell after two bind.
What two bacteria form endospores?
bacillus and clostridium.
Name the 7 facultative intracellular organisms?
Listeria, Salmonella typhi, Yersinia, Francisella, Brucella, Legionella, Mycobacterium
Mortality rate for septic shock?
Griffiths experiment with pneumococci demonstrated this?
When a bacteriophage transfers DNA to another bacterium?
Bacteria that have a prophage incorporated into their chromosomes?
Major mechanism of transfer of antibiotic resistance?
For bacteria to participate in conjugation they must have this?
F plasmid. encodes sex pilus.
Enzyme converting hydrogen peroxide into water and oxygen?
Type of Strep to completely lyse red blood cells?
Beta Hemolytic
Type of Strep to partially lyse RBC leaving a green color?
Alpha Hemolytic
Responsible for strep throat, scarlet fever, rheumatic fever, post stret glomerulonephritis?
Group A Beta-Hemolytic Strep, also known as Streptococcus Pyogenes
Name the 2 major antigenic components of Strep Pyogenes cell wall?
1. C carb: lancefield group A
2. M protein: major virulence factor. inhibits complement and plasma cells make Ab against.
What enzymes responsible for Strep Pyog being hemolytic?
1. Streptolysin O: also antigenic. See ASO antibodies develop.
2. Streptolysin S.
Enzyme of Strep Pyog responsible for Scarlet Fever and TSS? Why only few Strep's have this?
Pyrogenic exotoxin, also known as erythrogenic toxin. Found in few strains. Acquired by lysogenic conversion.
6 diseases Strep Pyogenes responsible for?
skin infection
Scarlet Fever
Rheumatic Fever
Type of skin infections seen with Strep Pyog + treatment?
folliculitis, cellulitis, impetigo.
Treat with dicloxacillin (they are also caused by Staph Aureus)
Why do some strains of Strep Pyogenes eat flesh? Treatment?
Some have M proteins that block phagocytosis.
Remove fascia, Penicillin G and clindamycin.
Pt with a sore throat develops a fever and a rash beginning on the trunk and neck, spreading to extremeties, sparing the face?
Scarlet Fever of Strep Pyogenes.
Rheumatic fever usually follows this disease in this age group?
Follows untreated pharyngitis.
Age 5-15.
Name 6 manifestation of rheumatic fever?
1. fever
2. myocarditis
3. migratory polyarthritis
4. chorea
5. subQ nodules
6. erythema marginatum.
10-20 yrs later heart murmur.
A child shows up in your office with a puffy face, high BP, and dark urine. One week ago the pt. had a sore throat. Diagnosis?
Acute post-streptococcal glomerulonephritis.
A neonate shows fever, vomiting, poor feeding, irritability. You suspect meningitis. What organism do you treat?
E. Coli, Listeria monocytogenes, Group B strep
What diseases are assoicated with Strep Agalactiae?
neonatal meningitis, pneumonia, sepsis
Name characteristics of Viridans Group Strep?
normal flora of GI tract, freq found in nasopharynx and gingival crevices
What 3 types infections see from Viridans strep?
Dental infections
Cause of cavities?
Strep Mutans
Pt presents with a slowly developing low grade fever, fatigue, anemia, and heart murmur. Pt. had untreated Strep throat when he was a child?
Viridans Strep: subacute bacterial endocarditis
IV drug user presents with abrupt onset of shaking chills, high spiking fevers, heart murmur? Culprit?
Staph aureus: acute infective endocarditis
Pt. blood shows Strep Intermedius? What is the next test you want to run?
CT: check for abscess.
Name the members of the enterococcus family of bacteria?
Faecalis and Faecium.
Where are common sites of Enterococcus infection?
UTI, biliary tract (grow in 40% bile), SBE.
What bacteria is a very common nosocomial offender who in normal GI flora and grows well in bile and 6.5% NaCl?
What allows the Enterococci to be Vancomycin resistant?
gene alters their cell wall d-ala d-ala to d-ala lactate.
Pt's blood test shows Strep Bovis? What is the cause of concern?
Bovis, normal GI flora (also grows well in bile but not 6.5% NaCl) may indicate colon malignancy
This organism is the major cause of bacterial pneuonia in adults?
Strep Pneumoniae
This bacteria is the #1 cause of meningitis in adults?
Strep Pneumoniae
This is #1 cause of otitis media in children?
Strep Pneumoniae
____ is to parents what group B strep is to kids?
Describe Quellung rxn and Optochin sensitivity?
1. Q=pneumococci on slide mixed with antiserum, will swell
2. O=Differ Pneumococcus with Strep Viridans (alpha hemo), Strep Pneumoniae growth inhibitied by Optochin
48 yr old pt. presents with rigors, high fever, SOB, and green sputum. On X ray there is consolidation of the middle R lobe and lower L lobe? What will be seen in culture of sputum?
lancet shaped gram positive diplocci
What does the pneumococcus vaccine target?
Targets the polysaccharide capsule, which is antigenic. Targets 23 different.
What drugs is Strep Pneumoniae gaining resistance to? How treat?
resistance: penicillin, erythro, tri/sulf, chloramphenicol
treat: high dose penicillin/cephalosporin or vancomycin
What simple test will differentiate Staph and Strep?
Catalase: staph are positive, strep are negative
You culture a specimen that is beta-hemolytic? You wonder if this is Strep Pyogenes or Staph Aureus? What agar will differentiate?
Sheep Blood Agar
on this Staph will elaborate a gold pigment.
We have differentiated Staph from Strep? What test do we run to see which type of Staph it is?
Coagulase test: Aureus is positive, epidermidis and saprophyticus is negative.
What 6 proteins does Staph Aureus use to diable our immune system?
1. Protein A: bind Fc portion IgG
2. Coagulase: fibrin formation around=protection
3. Hemolysins
4. Leukocidins
5. Penicillinase: secreted. disrupts beta lactam portion of penicillin.
6. Transpeptidase: some strains resistant to penicillin.
What 4 proteins Staph Aureus make to get through tissues?
1. Hyaluronidase: breaks proteoglycans in CT.
2. Staphylokinase: lyses fibrin clots
3. Lipase
4. Protease
Name 3 exotoxins of Staph Aureus?
1. Exfoliatin: scalded skin syndrome
2. Enterotoxin
3. TSST-1: bind MHC class II on APC. Result massive T cell outpouring cytokines, esp TNF and interleukin 1.
Name 11 diseases associated with Staph Aureus?
Gastroenteritis, TSS, Scalded Skin Syndrome, Pneumonia, Meningitis, Osteomyelitis, Acute bacterial endocarditis, septic arthritis, skin infection, bacteremia, UTI
Describe a classis attack of Staph Aureus food poisoning?
Eat pre formed toxin. nausea, vomiting, diarrhea, abd pain, fever occasionaly. Last 12-24 hours.
Describe a pt. who has TSS due to Staph Aureus?
Similar to a mix of food poisoning and scarlet fever.
Pt: high fever, nausea, vomit, watery diarrhea and BP may bottom out initially. few more days see diffuse rythematous rash. Later palms and soles undergo desquamation.
What type of pt. usually see scalded skin syndrome? symptoms? what must rule out?
Usually neonates with infection of the recently severed umbilicus or older child with skin infection. MUST rule out drug allergy.