bacteria Flashcards
What are the associated toxicities of vancomycin and what can be done to prevent them?
Red man syndrome - nonspecific mast cell degranulation (similar to an allergic reaction) caused by infusing too quickly. Can prevent by premedicating with antihistamine.
Nephrotoxicity
what are the anti-staphylococcal penicillins?
nafcillin, oxacillin, dicloxacillin, methicillin
what are the extended-spectrum penicillins? To what do they extend the spectrum?
ampicillin, amoxicillin. gram negatives and anaerobes.
what is the activity spectrum for regular penicillin?
gram positives, gram negative cocci and spirochetes
How did MRSA change to become resistant to penicillin?
altered penicillin-binding-proteins
if a patient has a severe penicillin allergy, which antibiotic should you use?
monobactam - aztreonam
which cephalosporins can cross the BBB?
3rd and 4th generations: ceftazidime, ceftriaxone, cefotaxime, cefepime
what is the name of the 5th generation cephalosporin and what does it cover?
ceftaroline. Covers MRSA but not pseudomonas or other nosocomial infections
which generation of cephalosporin has the best activity against anaerobes?
2nd generation: cefotetan, cefuroxime, cefoxitin.
what are the obligate anaerobes?
“Can’t breathe air” - clostridium, bacteroides, actinomyces
what are the obligate aerobes?
“Nagging pests must breathe” - nocardia, pseudomonas, mycobacterium, bacillus
What are the shared properties of all staphylococcus species?
Gram positive cocci in clusters, catalase positive, grow in 7.5% salt
What test differentiates staph aureus from the other staphs
Coagulase test.
S. aureus is coagulase positive
s. saprophyticus and epidermis are coagulase negative
Mannose test
S. aureus can ferment mannose but other staph cannot
What are the major virulence factors for staph aureus?
capsule - antiphagocytic
protein A - inhibits opsonization, complement fixing and ADCC
lipoteichoic acid - adherence
catalase - reduces phagocytic killing
coagulase - forms the wall around the abscess
penicillinase - cleaves beta-lactam ring
salt tolerant - can grow in picnic foods
What are the toxin-mediated diseases caused by staph aureus? What are the suppurative diseases caused by staph aureus?
toxin mediated = food poisoning (< 3 hours), toxic shock syndrome and scaled skin syndrome
suppurative = necrotizing fasciitis, carbuncle/folliculitis/furuncles, impetigo, endocarditis, osteomyelitis, septic arthritis, pneumonia, wound infection after surgery
What is the treatment for s. aureus?
A penicillinase resistant beta-lactam - nafcillin, oxacillin or methicillin
MRSA - vancomycin, linezolid, Trimethoprim sulfamethoxazole, clindamycin
What is the treatment for s. epidermis?
vancomycin
what is the treatment for s. saprophyticus?
oral cephalosporin or amoxicillin
Which strep species are alpha hemolytic? beta hemolytic? gamma hemolytic?
alpha - strep viridans, strep pneumoniae
beta - strep pyogenes (GAS), strep agalactiae (GBS)
gamma - enterococcus
What are the virulence factors of strep pyogenes?
capsule
M protein - inhibits opsonization
F protein - adherence
C5a peptidase - reduces inflammatory responses mediated by C5a
DNase - aids in bacterial spread by reducing viscosity of abscess material
hyaluronidase - aids in bacterial spread by destroying tissue
streptokinase - aids bacterial spread by breaking down clots
streptolysin O and S - lyses blood cells, stimulate release of lysosomal enzymes
What are the toxin-mediated diseases caused by strep pyogenes? suppurative diseases? nonsuppurative sequelae?
toxin-mediated = toxic shock syndrome, scarlet fever
suppurative = pharyngitis, skin infections, cellulitis
nonsuppurative sequelae = acute glomerulonephritis, rheumatic fever
What is the treatment for strep pyogenes?
penicillin G
What age group is at high risk for strep agalactiae (group B strep) infections? Why? What diseases does GBS cause?
Neonates are at high risk for GBS because GBS colonizes the GI and lower genital tract
Causes bacteremia, pneumonia and meningitis in neonates. Can also cause sepsis in mothers via wound inflicted during childbirth
What diseases does strep viridans (s. mutans and s. sanguis) cause? What are the symptoms?
Both cause endocarditis in patients with previously damaged heart valves. Symptoms are prolonged fever, heart murmur, microembolizations from vegetations breaking off, splinter hemorrhages under nails
S. mutans can cause dental caries
What is the treatment for streptococcal endocarditis?
penicillin
Which bacterial species has a positive quelling reaction? What is a quelling reaction?
Strep pneumoniae has a positive quelling reaction which is capsular swelling in the presence of specific anti capsular antibodies
What are the virulence factors for strep pneumoniae?
capsule
pneumolysin - lyses cells
IgA protease - evades mucosal immune defenses and allows bacteria to adhere
neuraminidase - promotes bacterial spread into tissue
What diseases does strep pneumoniae cause?
typical community-acquired pneumonia
bacteremia, possibly leading to meningitis
acute otitis media
sinusitus
sepsis in asplenic patients
peritonitis in children with nephrotic syndrome and ascites
What are the properties of enterococcus species?
gram positive cocci in chains, catalase negative, bacitracin resistant, bile and salt tolerant, normal flora of the large bowel and feces, inherently resistant to many antibiotics
What are the gram positive rods? Which of these produce exotoxins?
Bacillus species, clostridium species, corynebacterium diptheriae, listeria monocytogenes, nocardia and actinomyces. Produce exotoxins – bacillus species, clostridium, corynebacterium diptheriae
What are the virulence factors for bacillus anthracis?
Capsule has glutamic acid that prevents phagocytosis and complement lysis. Only bacteria to have amino acid in capsule
Where are bacillus anthracis spores found?
Soil, wool and animal hides
What are the three anthrax diseases?
Cutaneous anthrax
pulmonary anthrax
GI anthrax
What two exotoxins does bacillus cereus produce? What disease do these exotoxins cause?
Heat-stable enterotoxin – emetic food poisoning is rapid onset, 1-5 hours (similar to S. aureus). Preformed toxin ingested in reheated food.
Heat-labile enterotoxin – diarrheal food poisoning is slower onset, 10-15 hours (similar to clostridium perfringens). Produced by bacterial multiplying in the GI tract
What diseases does clostridium perfringens cause?
Food poisoning
Gas gangrene
Necrotizing enterocolitis
Cellulitis and fasciitis