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bacteria Flashcards

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1
Q

What are the associated toxicities of vancomycin and what can be done to prevent them?

A

Red man syndrome - nonspecific mast cell degranulation (similar to an allergic reaction) caused by infusing too quickly. Can prevent by premedicating with antihistamine.
Nephrotoxicity

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2
Q

what are the anti-staphylococcal penicillins?

A

nafcillin, oxacillin, dicloxacillin, methicillin

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3
Q

what are the extended-spectrum penicillins? To what do they extend the spectrum?

A

ampicillin, amoxicillin. gram negatives and anaerobes.

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4
Q

what is the activity spectrum for regular penicillin?

A

gram positives, gram negative cocci and spirochetes

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5
Q

How did MRSA change to become resistant to penicillin?

A

altered penicillin-binding-proteins

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6
Q

if a patient has a severe penicillin allergy, which antibiotic should you use?

A

monobactam - aztreonam

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7
Q

which cephalosporins can cross the BBB?

A

3rd and 4th generations: ceftazidime, ceftriaxone, cefotaxime, cefepime

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8
Q

what is the name of the 5th generation cephalosporin and what does it cover?

A

ceftaroline. Covers MRSA but not pseudomonas or other nosocomial infections

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9
Q

which generation of cephalosporin has the best activity against anaerobes?

A

2nd generation: cefotetan, cefuroxime, cefoxitin.

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10
Q

what are the obligate anaerobes?

A

“Can’t breathe air” - clostridium, bacteroides, actinomyces

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11
Q

what are the obligate aerobes?

A

“Nagging pests must breathe” - nocardia, pseudomonas, mycobacterium, bacillus

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12
Q

What are the shared properties of all staphylococcus species?

A

Gram positive cocci in clusters, catalase positive, grow in 7.5% salt

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13
Q

What test differentiates staph aureus from the other staphs

A

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

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14
Q

What are the major virulence factors for staph aureus?

A

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

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15
Q

What are the toxin-mediated diseases caused by staph aureus? What are the suppurative diseases caused by staph aureus?

A

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

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16
Q

What is the treatment for s. aureus?

A

A penicillinase resistant beta-lactam - nafcillin, oxacillin or methicillin
MRSA - vancomycin, linezolid, Trimethoprim sulfamethoxazole, clindamycin

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17
Q

What is the treatment for s. epidermis?

A

vancomycin

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18
Q

what is the treatment for s. saprophyticus?

A

oral cephalosporin or amoxicillin

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19
Q

Which strep species are alpha hemolytic? beta hemolytic? gamma hemolytic?

A

alpha - strep viridans, strep pneumoniae
beta - strep pyogenes (GAS), strep agalactiae (GBS)
gamma - enterococcus

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20
Q

What are the virulence factors of strep pyogenes?

A

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

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21
Q

What are the toxin-mediated diseases caused by strep pyogenes? suppurative diseases? nonsuppurative sequelae?

A

toxin-mediated = toxic shock syndrome, scarlet fever
suppurative = pharyngitis, skin infections, cellulitis
nonsuppurative sequelae = acute glomerulonephritis, rheumatic fever

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22
Q

What is the treatment for strep pyogenes?

A

penicillin G

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23
Q

What age group is at high risk for strep agalactiae (group B strep) infections? Why? What diseases does GBS cause?

A

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

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24
Q

What diseases does strep viridans (s. mutans and s. sanguis) cause? What are the symptoms?

A

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

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25
What is the treatment for streptococcal endocarditis?
penicillin
26
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
27
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
28
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
29
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
30
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
31
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
32
Where are bacillus anthracis spores found?
Soil, wool and animal hides
33
What are the three anthrax diseases?
Cutaneous anthrax pulmonary anthrax GI anthrax
34
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
35
What diseases does clostridium perfringens cause?
Food poisoning Gas gangrene Necrotizing enterocolitis Cellulitis and fasciitis
36
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)
37
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.
38
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)
39
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.
40
What toxin does corynebacterium diptheriae produce? What does the toxin do?
Diptheria toxin inhibits protein synthesis by ribosylation of elongation factor-2.
41
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
42
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
43
What are the clinical manifestations of bacterial sepsis?
Fever, leukopenia followed by leukocytosis, thrombocytopenia, DIC, shock
44
What causes bacterial sepsis?
Gram-negative bacteria shedding blebs of LPS which activates macrophages, endothelial cell to release lots of cytokines
45
What is the reservoir for carriers of salmonella typhi?
Gallbladder
46
What disease causing organism is associated with pet turtles?
Salmonella
47
What are the gram negative cocci species?
neisseria, bordetella pertussis, haemophilus, legionella pneumophilia,
48
What species are gram negative, diplococci?
neisseria
49
How do the sugar fermentation properties of neisseria gonorrhoeae and meningitides differ?
Meningitidis ferments maltose and glucose | gonorrhoeae ferments glucose only
50
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
51
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
52
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
53
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
54
What species of bacteria need to be grown with Factor X and factor V?
Haemophilus species (influenza and ducreyi)
55
What diseases does H. influenza cause?
otitis media, sinusitis, meningitis in infants, epiglottitis, arthritis affecting single large joints in young children, bronchitis
56
What disease does H. ducreyi cause?
Chanchroid - painful ulcer accompanied by inguinal lymphadenopathy
57
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
58
What organism is associated with a fruity odor?
pseudomonas aeruginosa
59
What organism produces a blue-green pigment called pyocyanin?
pseudomonas aeruginosa
60
Pseudomonas causes UTIs is what type of patient?
Patients with indwelling catheters
61
Burn wounds are at risk for infection with what type of bacteria?
pseudomonas
62
What types of skin infections does pseudomonas typically cause?
cellulitis, abscesses, subcutaneous infetions, ecthyma gangrenosum, hot-tub folliculitis
63
What types of bacteria cause chronic pulmonary infection in cystic fibrosis patients?
pseudomonas aeruginosa, burkholderia and staph aureus
64
How do people get osteomyelitis from pseudomonas aeruginosa?
from puncture of foot through sweaty athletic shoes
65
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
66
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
67
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
68
Which organism is associated with Guillain-Barre syndrome?
campylobacter jejuni possibly mycoplasma pneumoniae and cytomegalovirus
69
What clinical symptoms does campylobacter jejuni cause?
profuse watery or bloody diarrhea
70
How is campylobacter jejuni transmitted?
Through ingestion of contaminated food, usually chicken
71
What organism is associated with an increased risk of a MALT lymphoma (mucosal associated lymphoid tissue lymphoma)?
Helicobacter pylori
72
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
73
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
74
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
75
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
76
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
77
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
78
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)
79
How do you treat mycoplasma pneumoniae?
macrolides, tetracycline or fluoroquinolones | naturally resistant to beta-lactam antibiotics because no peptidoglycan cell wall
80
What organisms can cause a sexually transmitted urethritis?
gonococcus mycoplasma bominis ureaplasma urealyticum
81
What bacteria form long branching filaments that look like fungi?
nocardia and actinomyces
82
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
83
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)
84
What organism is associated with "sulfur granules"?
actinomyces
85
What organism is associated with causing salpingitis in women with intrauterine devices?
actinomyces
86
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
87
What bacteria is associated with foul-smelling abscesses?
bacteroides fragilis
88
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

microbiology (8 decks)

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