Gram Positive Flashcards
Important surface antigen for Gram +
Teichoic acid
D-glutamic acid capsule
B. anthracis
Catalase +, Coagulase +
Staphylococcus aureus
Catalse -, beta hemolytic
Strep. agalactiae or pyogenes
Clinical presentation of toxin mediated Stap aureus
Toxic shock syndrome, salded skin syndrome, food poisoning
TSST-1 antigen
Increases release of cytokines leading to acute fever, rash, desquamation on palms and soles, and hypotensive shock
“5-month old baby consuming honey has loss of extremity muscle tone”
Think Clostridium botulinum
6 yo pt comes in with a fever and sore throat; no immunization record; PE reveals a grey pharyngeal exudate and gram stain with gram positive organisms. What is the organism?
1) Cornybacteria diphtheriae
Gram positive club shaped rod, catalase positive; grown on Cysteine tellurite agar; causes grey pharyngeal exudate
Cornybacteria diphtheriae
How does the Cornybacteria diphtheriae exotoxin work?
1) AB exotoxin
2) A unit (active)- transfers a ribose residue from NAD to a histidine on EF2 (elongation factor 2)
3) EF2 is essential for peptide chain translocation on the ribosomes which results in inhibition of protein synthesis
What organism releases lecithinase?
1) Clostridium perfringens
2) Enzyme degrades membrane phospholipids leading to cell membrane destruction
How do you prevent Clostridium tetani in newborns?
1) Immunize the mother
2) IgG created from the mother are passed on to the baby
Gram positive cocci found in clusters, catalase and coagulate positive, cause of toxic shock syndrome and scalded skin syndrome
Staphylococcus aureus
What component of staphylococcus aureus binds to the Fc portion of host IgG
Protein A
What organism has the exotoxin TSST-1 released and diffused symmetrically. What is the result of the presence of this superantigen?
1) staphylococcus aureus
2) superantigen promotes excess cytokine release resulting in acute fever, desquamation of the palms and soles, hypotensive shock
How does scalded skin syndrome occur?
1) caused by skin wound or cutting of the umbilicus
2) staphylococcus aureus releases exofoliative toxins
3) toxins cause epidermis to slough off
What is the cause of food poisoning from staphylococcus aureus?
1) Bacteria release toxin in food such as custard
2) heat stabile toxin known as endotoxin se-a
What is Ritter’s Syndrome?
1) most severe form of scalded skin syndrome in neonates
2) occurs after cutting umbilical cord
Cause of Ritter syndrome
Staphylococcus aureus
Gram positive cord cocci; catalase positive, coagulate negative; novobiocin sensitive; polysaccharide capsule; generally occurs with infection on in dwelling medical devices
Staphylococcus epidermidis
Treatment for staphylococcus epidermidis
1) vancomycin
2) removal of foreign body
Endocarditis within 60 days of prosthetic valve placement? After 60 days?
1) staphylococcus epidermidis
2) viridans streptococci
Gram positive cords of cocci that are catalase positive and coagulate negative; novobiocin resistant; common cause of uti in sexually active women
Staphylococcus saprophyticus
Treatment for staphylococcus saprophyticus
Trimethoprim and sulfamethoxazole
Gram positive cocci arranged in chains; catalase negative, beta hemolytic; cause of scarlet fever and necrotizing fasciitis; group A classification
Group A Streptococcus pyogenes
Young girl complains of rough appearing rash on trunk and neck, desquamation of palms and soles; also complains of sore throat and fever
Group A Streptococcus pyogenes
Cause of Rheumatic fever
Group A Streptococcus pyogenes
Describe the renal complications associated with group A streptococcus pyogenes infection
1) infection that results in glomerulonephritis due to the deposit of immune complexes in the subepithelium
What are the major points of the Jones criteria?
2 major or one major and two minor think: J<3NES Major criteria 1) Joints (polyarthritis) 2) carditis (endocarditis, myocarditis, and pericarditis) 3) Nodules (subucutaneous - aka Osler nodes) 4) Erythema marginatum (Janeway lesions) 5)Sydenham chorea
Scarlet rash sparing face, strawberry (scarlet tongue), scarlet throat
Streptococcus pyogenes
Adolescent presents with brownish urine. Two weeks earlier had a sore throat that resolved. Positive ASO. Renal biopsy shows subepithelial humps in glomerulus
Group A Streptococcus pyogenes (immune mediated)
What is the protein found on Group A Streptococcus pyogenes that has immune cross reaction resulting in endocarditis and the deposition of immune complexes? What is its function?
1) M protein
2) Blocks phagocytosis
What are the possible clinical presentations of Group A Streptococcus pyogenes?
1) pharyngitis
2) impetigo
What are the causes of impetigo?
1) Streptococcus pyogenes
2) staphylococcus aureus
Young child presents with fever and rash that appears pustular with yellow crust, a honey comb appearance, with the presence on gram stain of gram positive cocci
Impetigo
Treatment for Streptococcus pyogenes
Penicillin G
Gram positive cocci arranged in diplococci, catalase negative, alpha hemolytic, positive Quellung test
Streptococcus pneumoniae
Elderly woman presenting with cough producing rusty colored sputum, also has chest pain, chills and fever
Streptococcus pneumoniae
How does Streptococcus pneumonia infect?
1) Spread by respiratory droplets
2) evades host by capsule and IgA proteases
Treatment for Streptococcus pneumoniae
1) penicillin or cephalosporin
Gram positive cocci arranged in chains that is catalase negative and grows in bile
Streptococcus bovus
What bacteria should be suspected with endocarditis with carcinoma of the colon?
Streptococcus bovis
Gram positive cocci arranged in chains, beta hemolytic, catalase negative, infection occurs by being carried in maternal genital tract, cause of neonatal meningitis or neonatal pneumonia
Group B streptococcus agalactiae
Gram positive cocci; catalase negative, alpha hemolytic; cause of dental caries; normally inhabits the oropharynx epithelium
Streptococcus mutans
Gram positive cocci; catalase negative, alpha hemolytic; cause of brain or abdominal abscessess; normally inhabits the GI tract
Streptococcus intermedius
Gram positive fungi appearing bacteria with beaded filaments; weakly acid fast obligate aerobe; cause of pneumonia and abscesses in the kidney/brain
Nocardia
What makes Nocardia acid fast?
The presence of mycolic acid in the cell wall
Treatment for Nocardia
1) Trimethoprim/Sulfamethoxalate
Gram Positive fungi appearing bacteria with beaded filaments; not acid fast; causes of abscesses in the mouth, lungs, and GU tract; forms yellow sulfur granules
Actinomyces israelii
yellow Sulfur granules?
Actinomyces israelii
What are the two bacteria that appear as beaded filamentous fungi?
1) Nocardia
2) Actinomyces
Gram positive cocci; catalase negative, grows in bile (group D); grows in 6.5% NaCl; all strains are resistant to cephalosporin; 2nd most common nosocomial infection
Enterococcus faecalis
Gram positive rod; spore forming; aerobic; motile; causes food poisoning (reheated rice); heat labile and stabile eneterotoxins
Bacillus cereus
What does the heat labile Bacillus cereus toxin cause? Heat stabile enterotoxin?
1) Heat labile causes vomiting and nausea
2) Heat stabile causes diarrhea increasing cAMP leading to less NaCl reabsorption
Gram positive rod; spore forming; aerobic; non-motile; death if inhaled; protein capsule (poly-D-glutamic acid capsule)
Bacillus anthracis
What is so important about the capusle of Bacillus anthracis?
It is a protein capsule made up of poly-D-glutamic acid
What are the toxins of Bacillus anthracis?
1) Protective Factor antigen (PF) - binds to cell membrane and mediates EF and LF
2) Edema Factor (EF) antigen- increases cAMP causing edema and inhibition of leukocytosis (acts like adenyly cyclase)
3) Lethal Factor (LF) antigen- causes cell death
Gram positive rod; spore forming; obligate anaerobe; motile; has a terminal spore; causes spastic paralysis and lockjaw
Clostridium tetani
What is the toxin produced by Clostridium tetani and how does it work?
1) Telanospasmin
2) Travels down the axons of peripheral motor neurons and blocks release of inhibitor neurotransmitters GABA and glycine
3) Nerves become hyperexcited and results in spastic paralysis
Telanospasmin
Clostridium tetani
What does Telanospasmin inhibit?
It inhibits the release of GABA and glycine neurotransmitters resulting in spastic paralysis
Gram positive rod; spore forming; obligate anaerobe; motile; cause of botulism
Clostridium botulinum
Sx of Adult Botulism
1) Diplopia
2) Descending paralysis
3) Dysphagia
4) ptosis
How does the heat labile toxin of Clostridium botulinum work?
1) Toxin is released after ingestion of contaminated food in to the vascular system
2) Toxin spreads to the peripheral cholinergic nerve terminals
3) Blocks the release of acetylcholine
How does infant botulism occur? What are the symptoms?
1) Caused by ingestion of spores found in honey
2) Spores germinate in intestine
3) Results in the release of toxins
4) Toxins absorbed and slowly blocks the release of acetylcholine
5) Results in flaccid paralysis
How would you differentiate the symptoms of food poisoning from Clostridium botulinum and tetani?
1) botulinum = floppy paralysis
2) tetani = tight, spastic paralysis
Gram positive rod; spore forming; obligate anaerobe; motile; cause of pseudomembrane colitis
Clostridium difficile
Treatment for C. diff
1) Oral metronidazole
2) Vancomycin
What antibiotic is associated with the presence C. diff after use ?
Clindamycin and ampicillin
Gram positive rod; spore forming; obligate anaerobe; non-motile; cause of gas gangrene
Clostridium perfringens
Gram positive rod; motile (tumbling motility); facultative intracellular organism; cause of meningitis; only gram positive bacteria with an endotoxin
Listeria monocytogenes
What is the only gram positive bacteria that has an endotoxin?
Listeria monocytogenes
Gram positive rod; non-motile; appear as chinese letters; causes grey pseudomembrane
Corynebacterium diphtheriae
What are the functions of the toxins produced by Corynebacterium diphtheriae?
1) Toxin AB ADP ribosylates the EF2 protein resulting in the inhibition of protein synthesis
Streptococcus that completely lyse rbcs
Beta hemolytic
Streptococci that only partially lyse, leaves a greenish discoloration media
Alpha hemolytic
Streptococci that are unable to hemolyze rbcs
Gamma hemolytic
What does protein A on Staphylococcus aureus do?
Binds to the Fc portion of the IgG preventing opsonization and phagocyotosis
How does the exotoxin of C. difficile work?
1) Exotoxin A- neutrophil chemoattractant
2) Exotoxin B - causes actin depolymerization and loss of cellular cytokeleton integrity
What is the role of a capsule?
Prevents opsonization and phagocytosis of organisms
Gram positive coccus; catalase negative; alpha hemolytic; optochin resistant
Streptococcus viridans
Gram positive coccus, catalase negative, alpha hemolytic; optochin sensitive; cannot be culture in bile
Streptococcus pneumoniae
Gram positive coccus catalase negative, beta hemolytic; bacitracin resistant
Streptococcus agalactiae
Gram positive coccus; catalase negative; beta hemolytic; bacitracin sensitive
Streptococcus pyogenes
Gram positive coccus; catalase negative; gamma hemolytic; growth in bile; no growth in 6.5% saline
Streptococcus bovis
Gram positive coccus; catalase negative; gamma hemolytic; growth on both bile and 6.5% saline
Enterococci
Catalase positive; novobiocin sensitive
Staphylococcus epidermidis
Catalase positive; novobiocin insensitive
Staphylococcus saprophyticus
What gram positive bacteria has metachromatic granules (red and blue)?
Corynebacterium diphtheria
Cause of black painless ulcer (eschar) surrounded by an edematous ring
Cutaneous infection of B. anthracis
Pt. comes in 1-5 hours after eating rice and beans with nausea and vomitting; after staying in the hospital around 3 hours later from his nausea e begins to have diarrhea that is watery
B. cereus
Facultative intercellular gram positive bacteria acquired from unpasteurized milk/cheese; tumbling mobility
Listeria monocytogenes
What does Listeria monocytogenes cause?
1) Meningitis in the neonate and immunocompromised
2) Gastroenteritis
Fungi appearing bacteria with branching filaments that causes pulmonary infections in immunocompromised
Nocardia
Gram positive rod that grows at low temperatures
Listeria monocytogenes
Pt. presents with progressive difficulty walking over the last two days accompanied by tingling in feet. Absent DTRs; Hx of diarrhea 2 weeks ago. What does he have? What caused the diarrhea 2 weeks ago?
1) Guillan Barre syndrome (demylination of the peripheral nerves)
2) Campylobacter jejuni
What bacteria is associated with Guillan Barre syndrome
Campylobacter jejuni
What is Staph. aureus enterotoxin found in?
Custard, mayonnaise and processed meats
What is enterococci resistant to by aceytlating the drug?
Aminoglycosides
Note: Also resistant to penicillin, TMP/SM, and Vancomycin
Cause of liver abscess through hematogenous seeding
Staphylococcus aureus
