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2: Other URT infections Flashcards

1
Q

what URT infections are caused by normal flora? mechanism by which this happens?

A

sinusitis, OM - secondary to blockage of sinus ostia, eustachian tube, by virally-induced or allergic inflammation

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2
Q

what are the four main normal flora dudes that cause URT infections? can these dudes cause meningitis? why or why not?

A

S. pneumoniae - G(+)
S. aureus - G(+)
H. influenzae, non type B - G(-)
M. catarrhalis - G(-)

no meningitis! b/c no capsule

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3
Q

symptoms of sinusitis

A
  • fever
  • pain to sinus palpation
  • purulent drainage at back of throat (can trigger asthma)
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4
Q

how can sinusitis/OM spread to become meningitis?

A

local infection -> invasive disease -> bacteremia -> systemic disease (inflammation of vessels allows crossing of BBB) -> once in CSF, no complement/opsonization -> grows -> meningitis

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5
Q

most common cause of invasive URT disease/meningitis in neonates

A
  • E. coli

- GBS

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6
Q

most common cause of invasive URT disease/meningitis in kids 1-5 y/o

A

now S. pneumoniae

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7
Q

most common cause of invasive URT disease/meningitis in adolescents/ young adults

A

N. meningitidis

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8
Q

most common cause of invasive URT disease/meningitis in all age groups

A

S. pneumoniae

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9
Q

what is the key to pathogenicity that allows some organisms to become systemic and cause meningitis?

A

ENCAPSULATION

  • allows persistence (evasion of immune system) to where it can reach blood (bacteremia), then dissemination, then endothelial cell/macrophage activation by LPS, then vascular leakage -systemic disease + through BBB and proliferate in CSF (no complement):
  • shock, DIC (disseminated intravascular coagulation)
  • meningitis
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10
Q

what actually kills the patient when they get meningitis from one of these guys?

A

the sepsis, DIC, shock

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11
Q

asplenia increases susceptibility to what organisms

A

encapsulated

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12
Q

describe capsule nature and implications for each:

  • pneumococcus
  • N. meningitidis
  • N. gonorrhea
  • H. influenzae type b
A
  • pneumo: PspC capsule: sepsis, meningitis
  • meningitidis: LPS capsule: DIC, sepsis, meningitis
  • gonorrhea: LOS capsule: septic arthritis
    * no sepsis, DIC, or meningitis!!
  • influenzae: LPS capsule: sepsis, meningitis
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13
Q

describe sepsis/shock

A

LPS stimulates TLRs (TLR4) to induce systemic cytokine secretion and endothelial cell activation -then increased vascular permeability, hypovolemia, shock, organ failure

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14
Q

describe DIC

A
  1. systemic activation of coagulation by bacteria

2. results in systemic microthrombi followed by hemorrhage after coagulation factors are used up - petechiae/purpura

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15
Q

what bug causes 95% of CA-pneumonias?

A

S. pneumoniae

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16
Q

what types of infections does S. pneumoniae cause?

A

normal flora -> secondary to obstruction/ other disease

MOPS: 
Meningitis 
OM 
Pneumonias (CA-lobar - often secondary to flu in elderly) 
Sinusitis
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17
Q

what is the most common cause of meningitis?

A

S. pneumoniae

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18
Q

lab findings in S. pneumoniae meningitis

A

in CSF:

  • bacteria
  • increased protein
  • increased PMNs
  • decreased glucose
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19
Q

what virulence factor of S. pneumoniae allows colonization of nasal mucosa?

A

IgA protease

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20
Q

what factors are associated with S. pneumoniae infections?

A
  • impaired immunity
  • malnutrition
  • alcoholism
  • age less than 2
  • sickle cell disease
  • any form of respiratory passage obstruction
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21
Q

what virulence factor of S. pneumoniae allows it to evade the immune system?

A

polysaccharide capsule (PspC) - antiphagocytic

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22
Q

other virulence factors of S. pneumoniae

A
  • pneumolysin (pore-forming and adherence)

- pspA (inhibits alternate complement pathway)

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23
Q

with S. pneumoniae, vaccines are effective for what age groups?

A

high risk groups: young and old

*different vaccines for young (conjugated) and old (not)

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24
Q

what does lobar pneumonia look like on XRay?

A
  • opaque (alveoli filled with pus, fibrin, and macrophages)

- fills entire lobe

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25
talk to me about the pneumococcal conjugate vaccine (PCV13)
-for all kids 5 y/o or less + adults at risk
26
what vaccine should kids 2 y/o or less + high risk patients also get in conjunction to PCV13?
pneumococcal polysaccharide vaccine (PPSV23)
27
what vaccine(s) should all adults 65 or older + those 19 and older at risk receive?
PPSV23 only!
28
risk factors for S. pneumoniae
- chronic diseases - immunodeficiency - asplenia
29
general characteristics about neisseria: - G(?) - capsule or no? - O2? - cofactors? - stable or labile in envt? - normal flora or no? - sensitivity?
``` G(-) encapsulated aerobic/facultative anaerobe needs Fe labile in environment not normal flora sensitive to penicillin ```
30
entry and incubation of N. meningitidis
enters nasopharynx and colonizes mucosa, then invades incubation less than 1w associated with cluster outbreaks - dorms, military
31
what happens when N. meningitidis gets into blood?
bacteremia, then - purulent meningitis, sepsis: - DIC with petechiae, particularly on earlobes, extremities - ischemic necrosis/gangrene in limbs (amputation) - vascular collapse
32
diagnostic confirmation of N. meningitidis
- examine CSF - gram stain!!!** - look at joint effusions for diplococci inside monocytes
33
what is an adrenal complication of N. meningitidis sepsis?
Waterhouse-Friderichson Syndrome: - adrenals fill w/ blood - if survive, end up with adrenal insufficiency b/c clot has compressed normal adrenal tissue
34
describe immune response to N. meningitidis
(antiphagocytic capsule) - Ab and complement-mediated phagocytosis
35
are vaccines effective for N. meningitidis
yes, for adolescents and adults | -but doesn't cover B serotype, which is most common cause of disease in neonates
36
describe entry of N. gonorrhea
attaches to columnar and transitional epithelia (pili) - mucosal membranes of the genital tracts, rectum, nasopharynx
37
virulence factors for N. gonorrhea
- LOS | - IgA protease (evades nasal mucosal immunity)
38
diseases caused by N. gonorrhea + pathophysiology
- gonorrhea - cystitis supporative inflammation of mucosal surfaces and subepithelial tissues (grossly purulent lesions and discharge) can cause supporative arthritis (knees, ankles) following bacteremia
39
what has prevented an effective vaccine for N. gonorrhea?
antigenic variability between strains
40
general characteristics of H. influenzae
G(-) pleomorphic type B = invasive, others noninvasive
41
what does non-invasive H. influenzae cause?
URT infections, sinusitis, OM - most unencapsulated - form part of normal URT flora (40-60% for kids, 35% for adults)
42
what does invasive H. influenzae cause?
meningitis, most commonly seen 1-6 y/o - most encapsulated - type B like an endotoxin - DIC - less than 10% have this as normal flora
43
describe two other hemophilus species and what they cause
H. parainfluenzae: normal flora of mouth, may cause endocarditis H. ducreyi: chancroids
44
what is the window of susceptibility for invasive disease by H. influenzae type b?
3 mo - 3 y | -kids can't make a good protective Ab response to type B capsular Ag's
45
general characteristics of M. catarrhalis
G(-) diplococcus normal flora of URT LPS endotoxin, but rarely causes septicemia and meningitis
46
why does M. catarrhalis not cause septicemia/meningitis even though it has LPS?
b/c capsule doesn't evade immunity like Neisseria can
47
what is the third most common cause of secondary bacterial infections such as sinusitis and OM?
M. catarrhalis
48
mechanisms of pathogenesis for diphtheria
- local epithelial necrosis (pseudomembrane formation) | - absorption and systemic release of exotoxin A (damage to distant organs - heart)
49
mechanisms of pathogenesis for pertussis
- cell-bound toxin with local epithelial inflammation - NO necrosis - swelling (narrowed epiglottis) - whooping of cough
50
what is a pseudomembrane composed of?
coagulation of: - dead cells (neutrophils) - blood - pus
51
general characteristics of bordetella pertussis
G(-) pleomorphic coccobacillus aerobic highly communicable, but self-limiting
52
histologic characteristic of pertussis
lymphocytosis!
53
tropism of pertussis, how this plays in with pathology
brush border: exotoxin leads to local ciliary paralysis with secondary inflammation
54
pertussis vaccine
gives immunization to exotoxin - DTaP 7 y/o or less - Tdap 10 y/o or more
55
general characteristics of corynebacterium diphtheria
G(+) | rod
56
action of diphtheria toxin when it goes systemic
- inhibits protein synthesis in eukaryotic cells | - leads to fatty myocardial changes, myofiber necrosis, and polyneuritis
57
what is the most common cause of death from diphtheria?
cardiac failure from exotoxin, NOT respiratory obstruction
58
what two main diseases do you think of with G(-) rods?
UTIs | intra-abdominal infections
59
general characteristics of G(-) rods
endotoxins: LPS frequent drug resistance has replaced pyogenic cocci as bulk of hospital-acquired and opportunistic infections
60
G(-) rods UTIs
non-obstructive: -E. coli obstructive: - Klebsiella - Edwardsiella
61
G(-) rods abdominal infections
- perforation - appendicitis - cholecystitis - diverticulitis last three are by obstruction
62
two main ways of getting G(-) infections
- spread of organisms that have colonized GI tract | - contamination of tissues and materials from the hospital
63
when do E. coli cause disease?
when they gain access to tissues (peritoneum, urinary tract, sepsis) or secondary to tissue inflammation in abdomen (appendicitis, obstruction)
64
can E. coli ferment lactose?
yes - coliform
65
what are two GI non-coliforms?
S and S - Salmonella and Shigella
66
E. coli types of infections
- UTIs/cystitis - supporative infections of abdominal cavity (secondary to obstruction, or via perforation/trauma) - hemorrhagic bronchopneumonia in debilitated patients (due to aspiration) - G(-) sepsis - DIC/shock
67
what is the cause of most uncomplicated UTIs in the absence of obstruction?
E. coli
68
what pneumonia is associated with aspiration in the hospital setting?
Klebsiella
69
infections caused by Klebsiella and Enterobacter
- UTIs secondary to obstruction* - septicemia: associated with thick mucoid capsule - pulmonary infections that may result in necrotizing abscesses
70
proteus mirabilis characteristics and infections
G(-) rod facultative anaerobe UTI/pyelonephritis pneumonia (debilitated patients)
71
virulence factor of proteus mirabilis and implications
secretes urease (urea to ammonia) - alkaline urine - in chronic pyelonephritis, get staghorn calculi (bladder)
72
serratia marcescens infections
pneumonia (debilitated patients) | UTIs
73
pseudomonas aeruginosa general characteristics
``` G(-) rod pyocyanin, pyoverdin motile, flagellum aerobic no spores ubiquitous in hospitals - nosocomial/opportunistic associated with conditions w/ decreased phagocytic fxn ```
74
pseudomonas virulence factors
- endotoxin LPS - exotoxin A (shock) - leukocidin
75
infections caused by pseudomonas
"superinfections" replace antibiotic suppressed organisms PSEUDOHmonas - pneumonia (cystic fibrosis) - sepsis (black lesions) - external otitis (swimmer's ear) - UTI - Drug use - osteomyelitis and endocarditis - Osteomyelitis in diabetics - Hot tub folliculitis also corneal keratitis in contact wearers
76
describe where pseudomonas localizes in tissues
overgrows around blood vessels - 'blue haze'
77
legionella pneumophilia general characteristics
``` G(-) rod flagella associated w/ water vapors- then causes epidemics community outbreaks ```
78
infections that legionella causes
90% get pontiac fever 10% get Legionaire's disease can get fibrinopurulent necrosis leading to scarring of pulmonary tissues
79
in what organisms do you see fibrinopurulent necrosis of pulmonary tissues?
ONLY staph and legionella strep pneumonias do not cause this
80
helicobacter pylori general characteristics
``` G(-) spiral/helical acid stable motile - moves through mucous secretions urease ```
81
function of urease in H. pylori
creates protective layer of ammonia around organism to protect it from acid
82
what does H. pylori cause?
90% of duodenal ulcers and 80% of chronic gastric ulcers
83
how often does H. pylori go asymptomatic
about 50% of affected adults
84
modes of infections for bacteroides and peptostreptococcus
- aspiration - trauma - fecal leakage
85
describe infections of bacteroides and peptostreptococcus
- ischemic, devitalized tissues - mixed infections - foul-smelling pus
86
two bacteroides
fusobacterium and peptococcus
87
what is peptostreptococcus known for?
gingival infections

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