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
What are the characteristics of c. perfringens food poisoning?
watery diarrhea with no fever, nausea or vomiting. Due to enterotoxin. Produced by bacterial multiplying in the GI tract (slower onset than preformed toxin)
What are the characteristics of c. perfringens gas gangrene?
Sudden onset of intense pain and swelling around wound. Rapid heartbeat. Bronze discoloration of skin and brown discharge. Gas production.
What toxin does clostridium tetani produce? What does it do? How does it present?
Tetanus toxin blocks release of GABA and glycine in the CNS, resulting in spastic paralysis. Initally presents with spasms of muscles of mastication (lockjaw, trismus), drooling, irritability, persistent back spasms (opisthotonos) and sardonic grin (risus sardonicus)
What toxin does clostridium botulinum produce? What does it do? How is this toxin ingested?
Botulinum toxin block release of acetylcholine at cholinergic synapses, resulting in flaccid paralysis and floppy baby syndrome. Usually ingested in improperly home-canned foods and contaminated honey.
What toxin does corynebacterium diptheriae produce? What does the toxin do?
Diptheria toxin inhibits protein synthesis by ribosylation of elongation factor-2.
What are the enteric bacteria (enterobacteriaceae)? Which ones are lactose fermenters? What are the morphologic characteristics? Which ones are normal flora and which ones are invasive?
E. coli, klebsiella, salmonella, shigella, serratia, enterobacter, proteus, Yersinia
Lactose fermenters = e. coli and klebsiella
Non lactose fermenters – shigella and salmonella
Characteristics – gram negative rods, ferment glucose, oxidase negative, have flagella (except shigella)
Normal flora – e. coli, klebsiella, enterobacter and proteus
Invasive – shigella, salmonella, Yersinia
What are the toxin-producing e. coli strains?
ETEC (enterotoxigenic) – watery diarrhea, cramps, nausea and low grade fever in travelers and infants (traveler’s diarrhea)
EHEC (enterohemorrhagic) – grossly bloody diarrhea, severe abdominal cramps, can lead to hemolytic uremic syndrome due to microangiopathic hemolytic anemia
EIEC (enteroinvasive) – watery diarrhea develops into dysentery with scant, bloody stools
UPEC (uropathic e coli) – adheres to uroepithelium and causes UTIs
What are the clinical manifestations of bacterial sepsis?
Fever, leukopenia followed by leukocytosis, thrombocytopenia, DIC, shock
What causes bacterial sepsis?
Gram-negative bacteria shedding blebs of LPS which activates macrophages, endothelial cell to release lots of cytokines
What is the reservoir for carriers of salmonella typhi?
Gallbladder
What disease causing organism is associated with pet turtles?
Salmonella
What are the gram negative cocci species?
neisseria, bordetella pertussis, haemophilus, legionella pneumophilia,
What species are gram negative, diplococci?
neisseria
How do the sugar fermentation properties of neisseria gonorrhoeae and meningitides differ?
Meningitidis ferments maltose and glucose
gonorrhoeae ferments glucose only
What species of infection are associated with a deficiency of terminal complement components (C5-C9)?
Deficiency in C5-C9 of the complement cascade increases risk of neisseria infections
What are the meningococcal diseases (diseases caused by neisseria meningitides)?
Meningitis - inflammation of the meninges presenting with fever, N/V, headache, myalgias and stiff neck.
Meningococcemia - the presence of n. meningitidis bacteria in the blood causes fever, shock, DIC and petechiae/purpura
Meningococcemia with or without meningitis
Waterhouse-Friderichsen syndrome - bilateral hemorrhagic adrenal infarctions
Mild febrile illness with pharyngitis, pneumonia, arthritis or urethritis
What diseases does neisseria gonorrhoeae cause?
males - urethritis with discharge and painful urination
females - cervicitis with discharge, painful urination and abdominal pain
Pelvic inflammatory disease
septic arthritis
neonatal conjunctivitis
What disease does bordetella pertussis cause? How does the pertussis toxin cause this disease?
Causes whooping cough.
Toxin enters cells and turns off inhibitory G protein, resulting in increased cAMP levels that loss of fluids and massive mucus secretion in the respiratory tract
What species of bacteria need to be grown with Factor X and factor V?
Haemophilus species (influenza and ducreyi)
What diseases does H. influenza cause?
otitis media, sinusitis, meningitis in infants, epiglottitis, arthritis affecting single large joints in young children, bronchitis
What disease does H. ducreyi cause?
Chanchroid - painful ulcer accompanied by inguinal lymphadenopathy
What are the gram negative, oxidase positive rods? What are the gram negative, oxidase negative rods?
oxidase positive - pseudomonas, burkholderia, vibrio cholerae, campylobacter, helicobacter
oxidase negative - enterobacteraceae species
What organism is associated with a fruity odor?
pseudomonas aeruginosa
What organism produces a blue-green pigment called pyocyanin?
pseudomonas aeruginosa
Pseudomonas causes UTIs is what type of patient?
Patients with indwelling catheters
Burn wounds are at risk for infection with what type of bacteria?
pseudomonas
What types of skin infections does pseudomonas typically cause?
cellulitis, abscesses, subcutaneous infetions, ecthyma gangrenosum, hot-tub folliculitis
What types of bacteria cause chronic pulmonary infection in cystic fibrosis patients?
pseudomonas aeruginosa, burkholderia and staph aureus
How do people get osteomyelitis from pseudomonas aeruginosa?
from puncture of foot through sweaty athletic shoes
In what types of patients does Burkholderia cepacia cause lung infections in? UTIs?
causes lung infections in cystic fibrosis and chronic granulomatous disease patients.
causes UTIs in people with indwelling catheters
How does the vibrio cholerae toxin cause severe diarrhea?
the cholera toxin turns on a stimulatory G protein, increasing cAMP levels and increasing secretion of ions into the lumen of the small bowel
What are the clinical characteristics of cholera?
rapid onset with vomiting, severe watery diarrhea with mucous flecks (rice-water stools) leading to dehydration and electrolyte imbalance. The electrolyte imbalance leads to cardiac arrhythmia, renal failure and acidosis
Which organism is associated with Guillain-Barre syndrome?
campylobacter jejuni
possibly mycoplasma pneumoniae and
cytomegalovirus
What clinical symptoms does campylobacter jejuni cause?
profuse watery or bloody diarrhea
How is campylobacter jejuni transmitted?
Through ingestion of contaminated food, usually chicken
What organism is associated with an increased risk of a MALT lymphoma (mucosal associated lymphoid tissue lymphoma)?
Helicobacter pylori
What are the virulence factors of helicobacter pylori?
neutralizes acid by producing ammonia, NH3, via urease enzyme
multiple flagella allows this bacteria to rapidly penetrate the mucus barrier
What are the diseases caused by helicobacter pylori?
stomach and duodenal ulcers
metaplasia of the stomach lining which increases risk for gastric adenocarcinoma
MALT lymphoma
What are the methods of identifying an H. pylori infection?
campylobacter-like organism (CLO) test - detects urease in a gastric biopsy
serologic tests - not helpful
radiolabeled urea breath test
stool antigen test - cheapest
What is the treatment for h. pylori infections?
triple therapy for 2 weeks:
1) bismuth salt + metronidazole + amoxicillin
2) bismuth salt + ranitidine (H2 blocker) + clarithromycin
3) proton pump inhibitor + amoxicillin + clarithromycin
What are the characteristics of mycoplasmas?
One of the smallest bacteria
lack a cell wall -> very pleomorphic -> resistant to beta-lactam antibiotics
not visualized with Gram stain
Only bacteria with sterols in their cell membrane -> requires sterols for growth
What type of pneumonia does mycoplasma pneumoniae cause? What other diseases can m. pneumoniae cause?
“Walking” pneumonia/atypical pneumonia
Interstitial pneumonia with no alveolar exudate
initial malaise, low-grade fever, headache, nonproductive cough, rales, rhonchi and myalgia. Can be preceded by pharyngitis.
Rarely causes an IgM-mediated hemolytic anemia
Can cause tracheobronchitis
pharyngitis
Associated with Guillain Barre syndrome
What are the differences in typical (strep pneumo) pneumonia and atypical (m. pneumoniae) pneumonia?
Preceding pharyngitis: atypical (common), typical (never)
onset: atypical (gradual), typical (rapid with chills)
fever: atypical (low grade), typical (high)
cough: atypical (nonproductive and non-purulent), typical (productive and purulent)
pleuritic chest pain: atypical (absent), typical (present)
leukocytosis: atypical (absent), typical (present)
How do you treat mycoplasma pneumoniae?
macrolides, tetracycline or fluoroquinolones
naturally resistant to beta-lactam antibiotics because no peptidoglycan cell wall
What organisms can cause a sexually transmitted urethritis?
gonococcus
mycoplasma bominis
ureaplasma urealyticum
What bacteria form long branching filaments that look like fungi?
nocardia and actinomyces
Which bacteria are weakly gram positive due to mycolic acids in the cell wall? Which are acid fast and partially acid fast?
mycobacterium - acid fast
nocardia - partially acid fast
What diseases can nocardia cause?
bronchopulmonary disease with cough, dyspnea, fever, cavitary lesions possibly leading to pneumonia (patients with pulmonary nocardia should be screened for CNS infection because it can spread there)
cutaneous infections: skin wound infections, mycetoma (painless, chronic subcutaneous swellings with draining sinus tracts)
What organism is associated with “sulfur granules”?
actinomyces
What organism is associated with causing salpingitis in women with intrauterine devices?
actinomyces
What are the differences between nocardia and actinomyces regarding gram staining? acid fast stain? growth conditions? common disease manifestations? Common patient population affected?
nocardia - weakly positive for gram stain; weakly positive for acid fast stain; obligate aerobic organism; manifests a lung disease, CNS abscess, mycetoma; mostly in immunocompromised patients
actinomyces - strongly positive for gram stain, negative for acid fast stain; obligate anaerobic organism; manifests as abscesses with draining sinus tracts, mycetoma; mostly after surgery or trauma
What bacteria is associated with foul-smelling abscesses?
bacteroides fragilis
What types of infections does bacteroides fragilis cause?
surgery and trauma cause normal flora in the colon to spread to sterile sites -> intra-abdominal abscesses, suppurative pelvic infections, bacterema
