gram (-) pathogens of mucosal surfaces pt. 1

Question 1

gram (-) path of mucosal surfaces

Answer 1

Enterobacteriaceae:
-e. coli,
-salmonella
-shigella
-klebsiella
-proteus
Vibrionoaceae:
-vibrio

Question 2

what is inoculum size?

Answer 2

how many bact are needed to cause disease

Question 3

natural barriers of GI tract

Answer 3

secretory antimicrobial compounds
microflora
acidity
motility 
mucous layer
tight jcns

Question 4

where are microflora bact and how do they help?

Answer 4

ileum and colon (b/c rest of GI tract is too motile)

outcompetes for food/binding sites

Question 5

what secretory antimicrobial compounds do we have and what do they do?

Answer 5

lysozyme - cleaves NAM and NAG of bact
lactoferrin - bacteriostatic b/c sequesters iron
cathelicidin - disrupts bact membrates of Gm-and Gm+ and fungi
defensins - create pores in microbes
IgA - makes it hard for microbes to adhere to surfaces

Question 6

how do bact fight innate barriers?

Answer 6

acid resistance
fimbriae/pili
cell structures (cationic AA's repel antimicrobial peptides and siderophores sequester iron in low iron environ. )
capsule
phagocytic compartment neutralization

Question 7

how do macrophages help w/ mucosal immunity?

Answer 7

hang out in mucous till activation of pattern recognition receptors (TLR4) initiates inflammatory resp.

Question 8

downside to macrophage activation?

Answer 8

inflammatory cytokines (TNF alpha) disrupt tight jcns of epithelial cells

Question 9

adaptive immune resp is generated in the …

Answer 9

lymph nodes

Question 10

traits and example of invasive pact pathogens

Answer 10

large intestine
sm. bloody stool w/ lymphocytes
tissue ulcerations
ex: salmonella and shigella

Question 11

types of shigella and how they’re distinguished

Answer 11

dist. by O antigen
dysenteriae
flexneri
boydii
sonnei

Question 12

shigella virulence factors/multiplication

Answer 12

acid resistant so low inoculum size

grow/multiply once in anaerobic env. in colon/ileum

Question 13

how do shigella cross epithelial membrane?

Answer 13

enter M cells via invasion plasmid antigen (IPA = membrane prot)
ingested by macrophages which start innate imm resp. causing inflammation opening tight jcns
ep cells ingest bact whose proteins lyse the phagosomal vesicle
shigella spread intracellularly by IcsA which help it avoid re-entering lamina propria where immune cells are

Question 14

which shigella is diff than the others and how?

Answer 14

s. dysenteriae type 1
causes invasive diarrhea (like other types) but also produces shiga toxin which kills intestinal ep and endothelial cells and disrupts Na absorption causing LOTS of watery bloody stool

Question 15

diseases caused by salmonella

Answer 15

gastroenteritis - self limiting
typhoid fever (only caused by s. typhi) - deadly

Question 16

characteristics of salmonella infection

Answer 16

fecal oral transmission
large inoculum (more acid sensitive than sigella)
acidity of stomach triggers virulence genes

Question 17

how do samonella enter cell?

Answer 17

induce phagocytosis through inducing cell signaling pathways and causing ruffled cell surface
remain in cell vescicles for hours then get into lamina propria
some are phagocytosed but some escape and cause bacteremia
(typhi stay in phagosomes where they thrive)

Question 18

traits of s. typhi

Answer 18

enter in lymph
replicate w/in macrophage phagosomes
only in humans
asymptomatic carriers with gall bladder infections

Question 19

similarities btwn shigella and salmonella

Answer 19

both respond/activate virulence factors due to env. changes (shig= anaerobic env.; salm = low pH)
both are invasive so cause low vol. bloody leukocytic diarrhea

Question 20

dissimilarities btwn shigella and salmonella

Answer 20

salm has high inoculum size, shig. has low innoculum size
salm. spreads thru bacterimia, shig spreads intracellularly and locally thru IcsA
species that cause severe disease are v. dissimilar (typhi v. dyssenteria)

Question 21

treatment of invasive enteric path

Answer 21

rehydration
fluoroquinolones
typhiod fever = vaccine, gall bladder removal or fluoroquinilones