Gram Negative Pathogens (Neiserria and Enterics) Flashcards
T/F. Neisseria is G+.
False. G-
T/F. Neisseria exists as staphylococci.
False. Diplococci
T/F. Neisseria is aerobe.
False. Facultative anaerobe
T/F. Neisseria optimally grows in high O2 conditions.
False. Facultative anaerobe; optimal growth at high Co2 conditions
How do you differentiate N. meningitidis and N. gonorrheae?
N. meningitidis is a maltose and glucose fermenter
N. gonorrheae is a glucose fermenter only
T/F. N. meningitidis is part of the normal flora.
True. Accounting to 5% of the normal flora
T/F. N. meningitidis causes what characteristics diseases?
Meningitis and septicemia
N. meningitidis is spread via what infectious medium?
Respiratory secretions
The endotoxin associated with N. meningitidis is in the form of?
Lipopolysaccharide (LPS)
What are the virulence factors associated with N. meningitidis?
Pilus for adherence
Capsule
Endotoxin (LPS)
IgA Protease
Among the virulence factors of N. meningitidis, which provides capacity for adherence?
Pilus
Symptoms of N. meningitidis-induced meningitis:
fever
petechial rash
stick neck
lethargy
vomiting
Symptoms of N. meningitidis-induced septicemia:
fever
petechial rash
hypotension
Petechial rash appears to be associated with Neisseria infection. This condition is due to?
Destruction of the blood vessels caused by the LPS endotoxin in N. meningitidis
Treatment for N. meningitidis infection?
Penicilin G
rifampin
ceftriaxone
ciprofloxacin
Vaccine
T/F. Neisseria species are rods species.
False. Cocci
Culture medium for Neisseria isolation
Chocolate agar - supports fastidious nature of N species
Thayer- Martin VCN media - selective media against G+, other G- (esp rods), and fungi
V - vancomycin - against G+
C - Colistin - against other G-, esp G- rods
N - Nystatin - against fungi
What populations are particularly susceptible to N. meningitidis infection?
Neonates susceptible
Army recruits - coming from different places
Freshmen in dorms - coming from different place
What is the 2nd most common STD?
Gonorrhea
What are the virulence factors associated with N. gonorrheae?
Pilus
PorA and PorB (outer membrane porins)
Opa proteins
Of the virulence factors of N. gonorrheae, which allows invasion into epithelial cells?
PorA and PorB
Of the virulence factors of N. gonorrheae, which provides both adherence and invasion functions?
opa proteins
What is the primary presentation of N. gonorrheae infection in males?
urethritis
What is the primary presentation of N. gonorrheae infection in females?
cervical gonorrhea which may lead to pelvic inflammatory disease
What presentation of N. gonorrheae infection is common among males and females?
gonoccocal bacteremia and septic arthritis
What is the primary presentation of N. gonorrheae infection in neonates?
opthalmia neonatorum (neonatal conjunctivitis)
Treatment for N. gonorrheae (general population):
Ceftriaxone, cefixime, gentamicin
Treatment for N. gonorrheae (neonates):
erythromycin eyedrops and syrup for prophylaxis against N. gonorrheae and concurrent chlamydial infection
When diagnosing N. meningitidis, inoculum may be derived from?
CSF or petechial scrapings
T/F. Complete immunity can be developed after initial infection by N. gonorrheae making subsequent reinfection impossible.
False. No immunity; reinfection is possible
T/F. Enterobacteriaceae species are very common and are part of the normal gut microflora or may cause GI infections.
True.
How many genera are classified under Enterobacteriaceae?
63 genera
How many species of Enterobacteriaceae is considered clinically significant?
20-25 species
T/F. Enterobacteriaceae are G- coccus.
False. G- rods
T/F. All Enterobacteriaceae are motile.
False. Some are nonmotile
Motile Enterobacteriaceae are associated with having what structures?
A peritrichous flagella
T/F. Enterobacteriaceae are facultative anaerobes.
True.
T/F. Enterobacteriaceae can undergo glucose fermentation with gas production.
True
T/F. Enterobacteriaceae catalase positive.
True
T/F. Enterobacteriaceae are oxidase positive.
False. Oxidase negative
T/F. Enterobacteriaceae cannot reduce nitrate.
False. Can reduce nitrate to nitrite
Colony characteristics of E. coli include:
circular, convex, and smooth colonies
T/F. Some strains of E. coli may be hemolytic
True.
Colony characteristic of Enterobacter
Mucoid colonies
Colony characteristic of Klebsiella
large and mucoid colonies
Colony characteristic of Salmonella and Shigella
Colonies like E. coli but do not ferment lactose
What are the differential and biochemical tests for Enterobacteriaceae.
IMViC test
TSIA in slant/butt tubes
Use of differential media, e.g., EMB, MAC, and deoxycholate
MPN test
Which member of Enterobacteriaceae can ferment lactose and which do not?
E. coli - ferments lactose
Salmonella, Shigella, and Pseudomonas do not
In Eosin Methylene Blue (EMB) is a differential and selective medium. How does it differentiate/selects?
Eosin-Methylene Blue - selects G- bacteria and inhibits G+
Differentiates lactose fermentors (dark colonies) from non fermentors (pale/colorless)
E. coli, in particular, appear with characteristic green metallic sheen
In TSIA slant/butt test, A/A indicates that
bacterium can ferment all three sugar
The Triple Sugar Iron Agar (TSIA) contains what sugars allowing test for the capacity of bacteria to ferment these said sugars?
glucose
lactose
sucrose
In TSIA slant/butt test, a crack in the agar indicates
gas production
In TSIA slant/butt test, black precipitate indicates
hydrogen sulfide production through reduction of sulfur compounds
IMViC is a series of biochemical tests for the characterization of Enterobacteriaceae species and includes
Indole test
Methyl red test
Voges-Proskauer test
Citrat test
In TSIA slant/butt test, an A/K result indicates
glucose fermentation only
In writing the serotype notation of bacteria, O refers to what antigen?
O antigen component of the LPS of the outer membrane
O antigen also provides resistance to alcohol and heat and induces IgM production by host
In writing the serotype notation of bacteria, K refers to what antigen?
capsule
In writing the serotype notation of bacteria, H refers to what antigen?
Flagella
In this type of intestinal invasion by Enterobacteriaceae species, bacteria binds only to the cell and the release of exotoxins (de facto enterotoxins) cause watery diarrhea.
No cell invasion
Which member of the Enterobacteriaceae usually performs no cell invasion and causes watery diarrhea?
Enterotoxigenic E. Coli and V. cholerae
In this type of intestinal invasion by Enterobacteriaceae species, bacteria binds and invades the intestinal epithelium resulting in host cell death. This type is also associated with systemic immune response by the host.
Invasion of intestinal epithelial cells
Which member of the Enterobacteriaceae usually performs invasion of intestinal epithelium.
Enteroinvasive E. coli, Shigella, Salmonella enteritidis
In this type of intestinal invasion by Enterobacteriaceae species, bacteria enters and bloodstream and reaches the lymph nodes causing bacteremia, and sepsis.
invasion of lymph nodes and bloodstream
Which member of the Enterobacteriaceae usually performs invasion of lymph nodes and bloodstream?
Salmonella typhi; Yersinia enterocolitica, Campylobacter jejuni
What are the virulence factors associated with E. coli?
Pilus
Capsule
Exotoxin production (LT, ST, and Shiga-like toxin)
Endotoxin (Lipid A)
Iron-binding siderophores
Hemolysin
Among the virulence factors of E. coli, which allows mucosal interaction?
Pilus
E. coli exotoxin is in the forms of?
LT (cAMP) and ST (cGMP) toxins
Shiga-like toxins (acquired due to sharing of plasmid by Shigella)
E. coli endotoxin is in the form of?
Lipid A
What are the clinical findings associated with E. coli?
Neonatal meningitis
Diarrhea (Montezuma’s revenge aka traveller’s diarrhea)
UTI
Sepsis
What is the most common cause of UTI?
E. coli
What is the virulence factor allowing E. coli to produce urinary tract infection?
Pilus and fimbriae (allows E. coli to travel up the urethra)
Hemolysin
Clinical findings associated with E. coli induced UTI:
Cystitis
Pyelonephritis
Symptoms of E. coli induced UTI:
Dysuria - painful or difficult urination
Hematuria - blood in urine
Pyuria - pus in urine
Frequent urination
What is the virulence factor allowing E. coli to induce sepsis?
(endo)Toxins
T/F. E. coli induced sepsis is usually a primary infection.
False. E. coli induced sepsis is often secondary to UTI
What is the most common cause of G- sepsis?
E. coli
T/F E. coli induced sepsis generally affects the general population.
False. usually just the immunocompromised and neonates
What is the virulence factor allowing E. coli to produce neonatal meningitis?
capsule