Gram- Cocci Flashcards
what are 2 important species of Neisseria, a Gram- cocci?
- N. gonorrhoeae (gonococci): 2nd most common STI in US
- N. meningitidis (meningococci): common causative agent for bacterial meningitis
what family of bacteria does this describe?
- kidney-shaped diplococci
- aerobic
- sensitive to heat and drying
- often seen with PMNs upon Gram staining
Neisseria: Gram- diplococci, 2 species - N. gonorrhoeae and N. meningitidis
what species of bacteria does this describe?
- unencapsulated
- antigenically heterogenous pili, opa proteins, and LOS
- IgA protease virulence factor
- proteins that extract iron from host iron-binding proteins (transferrin)
Neisseria gonorrhoeae: Gram- cocci
phase variation and gene conversion enables heterogeneity of surface antigens:
- pili: facilitate attachment
- Opa: opacity proteins, formerly PII
- LOS: endotoxin, like LPS but more branched
IgA protease helps infect mucosa
Neisseria gonorrhoeae (Gram- cocci) is the 2nd most common STI in the US. It attacks mucous membranes via _____ which are critical for mediating adherence
type IV pili
Neisseria gonorrhoeae has several clinical manifestations, including:
1. pharingitis and rectal infections
2. ______ infections which may lead to pelvic inflammatory disease or infertility
3. _______ in neonates
4. rare bloodstream invasion, which can lead to _____
- pharingitis and rectal infections
- GENITOURINARY TRACT infections which may lead to pelvic inflammatory disease or infertility
- OPTHALMIA NEONATORUM in neonates
- rare bloodstream invasion, which can lead to DGI (DISSEMINATED GONOCOCCAL INFECTION)
Neisseria gonorrhoeae infection in neonates can cause opthalmia neonatorum. What is used for as prophylaxis for routine and high-risk cases, respectively?
routine prophylaxis: erythromycin ointment or silver nitrate
high-risk babies: ceftriaxone
rarely, Neisseria gonorrhoeae (Gram- cocci) invades the bloodstream and causes DGI
what is this and how does it present
disseminated gonococcal infection (DGI): present with arthritis and dermatitis (scattered skin lesions), and is common cause of septic arthritis in sexually active adults
how can Neisseria gonorrhoeae be cultured (what does it need)?
grow on Thayer-Martin media (chocolate agar) containing antimicrobial agents to suppress normal flora (example of selective media)
grows better under enhanced CO2, oxidase positive
(remember that Neisseria is aerobic and sensitive to heat and drying)
what do current guidelines suggest as first-line treatment of Neisseria gonorrhoeae?
gonococci are very antibiotic resistant (penicillin, tetracycline, quinolones) —> PPNG (penicillinase-producing), TRNG (tetracycline resistant), QRNG (quinolone resistant)
current guidelines: Ceftriaxone along with azithromycin or doxycycline for possible concomitant chlamydial infection (often travel together)
in addition to antigenically heterogeneous proteins (pili, Opa, LOS), IgA protease, and iron extraction system, what virulence factor does Neisseria meningitidis have that N. gonorrhoeae does not? (both are Gram- cocci)
antigenic capsule: 13 serogroups - A, B, C, Y, and W-135 cause most infections
in US, serogroup B is most common
[remember that N. gonorrhoeae is unencapsulated]
how does Neisseria meningitidis (Gram- cocci) spread? where is it found in carriers? how does it progress?
N. meningitidis spreads via epidemic waves in closed communities (dorms, barracks)
nasopharynx of carriers
can infect young and healthy individuals, infants more susceptible
rapid onset and progression (12-24 hours), life-threatening
vaccine available
infection with Neisseria meningitidis (Gram- diplococci) can manifest as meningococcemia, in which N. meningitidis rapidly divide in the bloodstream and cause spiking fevers, chills, joint/muscle pain, and non-blanching petechial rash
what 2 things could this develop into?
- meningitis: purulent CSF, inflamed meninges, triad of severe headache + stiff neck + photophobia, as well as altered mental state, fever, vomiting
- fulminant septicemia: LOS-mediated septic shock, large purple blotchy hemorrhages (purpura or ecchymoses), DIC, adrenal collapse (Waterhouse Friderichsen syndrome)
Pt is an 18yo F presenting to the ED with rapidly progressing spiking fever, chills, joint/muscle pain, and non-blanching petechial rash beginning 1 day ago. PMH is unremarkable. Pt recently moved into dormitory for college.
What is your biggest concern?
Meningococcemia, due to N. meningitidis infection (often spreads via epidemic waves in closed communities like dorms or barracks)
non-blanching petechial rash is key finding
this could develop into meningitis or fulminant septicemia
how is infection with Neisseria meningitidis treated?
bacterial meningitis is emergency - start antibiotics before definitive diagnosis
use 3rd generation cephalosporin - ceftriaxone or cefotaxime (because meningitis could also be due to strep. pneumoniae which is very resistant)
if confirmed N. meningitidis, large dose of penicillin or ampicillin
prophylactic rifampin for close contacts
which 2 bacterial strains are important common causes of meningitis? how does this affect treatment?
strep. pneumoniae and neisseria meningitis (both encapsulated)
bacterial meningitis is emergency, so start antibiotics before definitive diagnosis
start with ceftriaxone or cefotaxime (because strep. pneumoniae is resistant to drugs), then can switch to penicillin if confirmed N. meningitidis infection
*prophylactic rifampin for close contacts
