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