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Gram Negative Cocci
Neisseria, Moraxella, & Acinetobacter
37
Microbiology
Graduate
03/30/2011

Additional Microbiology Flashcards

 


 

Cards

Term
the important neisseriaceae genus:
Definition
Neisseria (meningitidis & gonorrhoeae)
Term
characteristics/epidemiology of Neisseria meningitidis (meningococcus)
Definition

non-motile

fastidious

oxidase+ (produces acid from maltose & glucose)

colonizes: nasopharynx/pharynx

endemic disease worldwide esp cold/dry mo

transmission: respiratory droplets in prolonged close contact 

prevalence: highest in school-aged children

Term
Most of N. meningitidis virulence due to:
Definition

*outer membrane components:

1. capsule-antiphag; incr survival in blood/CSF

2. outer mem proteins: two major OMPs, PorA & PorB (=> hydrophilic pores, stim endocytosis & inflammation)

3. Lipooligosaccharide: antigenic variability

4. Pili (fimbriae): antigenic variability; adherence

5. more proteases

Term
LOS is structurally related to LPS, what is the difference?
Definition

[LOS = N. meningitidis endotoxin]

No repeating O-antigen subunits of sugars

lipid A (type of LOS) interaction w/ TLR4 & MD2 (mem prot; these both present on monocytes, macroph, dendritic cells, & other phagocytes)

*LOS circulating =morbidity/mortality

 

Term
pathogenesis of N. meningitidis: normal colonies of pharynx/nasopharynx can spread (via certain surface proteins) to non-ciliated epithelial mucosal cells of URT, then...
Definition
these cells internalize the N. meningitidis bacterium --> enter submucosa --> bloodstream
Term
name the diseases caused by N. meningitidis (2 life-threatening, 3 not)
Definition

life-threatening: 1. acute bacterial meningitis 

2. meningococcemia

 

not: 1. pneumonia (usually preceded w/ URT infection; symptoms: cough, chest px, fever/chills, pharyngitis perhaps)

2. arthritis

3. urethritis

Term
most rapid and lethal form of septic shock in humans
Definition

meningococcemia 

pt may also have meningitis

Term
how is meningococcemia different from other "shocks"? cause?
Definition

*prominent hemorrhagic skin lesions

LOS loosely attached to outer mem (released into circulation; stim monocytes/dendritic cells/endothel cells => release cytokines)

[N. meningitidis invade vasc endothel & prod procoagulants]

Term
disseminated intravascular coagulopathy (DIC)
Definition

once N. meningitidis produces procoagulants (this is the cause of skin lesions)

activate factor XII

characteristics: small petechial sking lesions (trunk & LE) may coalesce => lg hemorr lesions

may => Waterhouse-Friderichsen Syndrome

Term
what is Waterhouse-Friderichsen Syndrome (WFS)?
Definition

hemorrhagic adrenalitis (=> massive hemorrhage in 1 or both adrenals)

most common bacterial agent: N. meningitidis

characterized by: overwhelming bact infec, low BP, shock, DIC, widespread purpura, rapidly develop adrenocortical insufficiency

Term
most common form of Neisseria disease in the US:
Definition

N. meningitidis meningitis

#1 cause of bacterial meningitis in children <5 yoa in US (before 1995, was H. influenzae)

untx: 100% fatality 

w/ antibiotic tx: 10%

onset: abrupt, typical meningeal signs

frequently seen in: children; complement deficiencies

Term
typical meningeal signs
Definition

severe headache

stiff neck

bright-light phobia

fever/vomiting

drowsy/less responsive

rash (anywhere)

Term
what substances from the host plays a major role in causing the skin lesions of meningococcemia
Definition
cytokines (IL-1, IL-6, TNF-alpha)
Term
[image]
Definition
neisseria meningitidis
Term
identification of N. meningitidis
Definition

gram stain: gram- w/ coffee-bean shape

culture: growth on chocolate agar

oxidase test+ (dark blue/purple color change)

carbohydrate utilization test: maltose AND glucose positive

Term
virulence of N. gonorrhoeae (3)
Definition

1. transferrin binding protein (Fe acquisition)

2. lactoferrin binding protein (")

3. Hb Binding protein (")

 

also, pilin: antigenic variation (prior exposure cannot protect against different bacterium)

Term
primary sites of infection of N. gonorrhoeae in men and women
Definition

men: urethra

women: uterine cervix (higher risk of infection after single exposure; carriage may be asymptomatic)

Term
Neisseria gonorrhoeae can spread two ways, systemically & locally; what are the diseases associated w/ these pathways?
Definition

local spread: 

male-gonococcal urethritis

female-cervicitis

disseminated forms:

skin lesions

endocarditis

arthritis

opthalmia neonatorum

Term
symptoms of gonococcal urethritis in males
Definition

2-6d after exposure

dysuria

itching

purulent discharge

testicular px

(95% acute)

Term
symptoms of gonococcal cervicitis in females
Definition

frequently asymptomatic

cervical discharge (seen on swab test; normal/negative=white & positive=yellow)

lower abdominal px

cervical-vaginal tenderness

dysuria

Term
most common gynecological disorder in the US
Definition

pelvic inflammatory disease

early symptoms: dyspareunia & abdominal px

transmission: sexual contact

Term
N. gonorrhoeae complications in females (primary: cervicitis)
Definition

1. salpingitis

2. endometritis

caused by the close proximity of these structures to each other (propelled by menstruation)

 

Term
opthalmia neonatorum (neonatal conjunctivitis)
Definition

neisseria gonorrhoeae

mother-->child (delivery)

symptoms: lid edema, redness, purulent discharge, swelling, px

gram stain: lots of bacteria & inflamm cells

may lead to blindness (rapid progression; severe ulcerative keratitis & perforation)

Term

types of disseminated gonococcal infection (DGI)

occur when N. gonorrhoeae infections are left untreated

Definition

1. gonococcal skin papules

2. septic arthritis (joint is NOT infected, just an immune response) vs poly arthritis (joint not infected, host response) vs mono arthritis (organism in blood eventually gets into 1 joint-this joint is infected)

*N. gonorrhoeae is the #1 cause in 16-45 yoa (staphylococcus aureus is #2 in this case, #1 in all other age groups for septic arthritis)

Term
what is Thayer Martin agar
Definition
chocolate agar w/ antibiotics (vancomycin, colistin, trimethoprim & an antifungal agent)
Term
clinical sample: test for N. gonorrhoeae
Definition

1. gram stain (+ for PMN & gram- intracellular diplococci)

2. culture on thayer martin agar (+ w/ growth)

=> N. gonorrhoeae

Term
testing for N. gonorrhoeae, gram stain comparison of 1st 10 ml urine w/ mild stream:
Definition

urethritis: more PMNs w/ diplococci in 1st sample

cystitis: same # PMNs in both samples

Term
Moraxella catarrhalis characteristics
Definition

gram-

aerobic 

oxidase+

diplococcus

Term
Moraxella catarrhalis epidemiology & virulence 
Definition

normal flora of URT (esp in children)

virulence not known (possibly LPS); some w/ pili/fimbriae (attachment to epithelium)

Term
Diseases caused by M. catarrhalis
Definition

URT infections (otitis media/sinusitis): children

[3rd most common cause behind S. pneumoniae & non-typable Haemophilus influenzae]

LRT: adults

 

Term
identify M. catarrhalis
Definition

gram-

diplococcus

chocolate/blood agar culture: opaque & non-hemolytic

fermentation tests: does NOT use sucrose, glucose, maltose, or lactose

Term
Acinetobacter characteristics
Definition

non-motile

not pigmented

no fermentation

gram-

non-fastidious

Term
Acinetobacter epidemiology/prevalence
Definition

only gram- organism part of normal skin flora (skin & distal urethra of healthy people)

emerging nosocomial pathogen

*commonly isolated from wounded US troops in Iraq

Term
Acinetobacter baumanii virulence factors
Definition

1. capsule (antiphagocytic)

2. LPS

3. bacteriocins

4. no known cytotoxins

5. resistance to antibiotics

(produces biofilms)

Term
diseases caused by Acinetobacter baumanii
Definition

pneumonia (assoc w/ ventilator use)

bacteremia/septic shock

meningitis (usually after neurosurgery)

Term
identify Acinetobacter baumanii
Definition

log phase: bacilli

stationary phase: coccobacilli

colonies (non-pigmented) may be mucoid (from capsule)

*oxidase- (as opposed to both Neisseria & Moraxella, which are oxidase+)

Term
[image]
Definition

superoxal test

similar to catalase test except 30%, not 3% H202 is used

N. gonorrhoeae: rapid/strong bubbles=positive

(other Neisseria: no/weak bubbling)

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