microbiology Flashcards
campylobacter jejuni
food borne cause of fever, abdominal pain and diarrhea; both kids and adults
rotavirus
most common cause of viral gastroenteritis in infants/children; can lose fluids and become dehydrated
escherichia coli
hemolytic-uremic syndrome in kids
cryptosporidiosis
watery diarrhea in immunocompromised adults by cryptosporidium
listeriosis
congenital infection that is present with meningitis and sepsis at birth – food or water borne
norwalk virus
common cause of diarrhea in adults
shigellosis
dysentery with bloody diarrhea
cholera
massive fluid loss
what is the agent that is associated with duodenal peptic ulcers?
H pylori
vibrio parahaemolyticus
found in raw shellfish
yersinia enterocolitica
invasive; extraintestinal infection
staph aureus causes food poisoning through…
food poisoning through elaboration of an enterotoxin that causes explosive diarrhea within 2 hrs of ingestion
entamoeba histolytica
colonic mucosal invasion with exudate and ulceration; stool with blood and mucus
self limited diarrhea with following liver abscess(via submucosal invasion –> veins –> portal system –> liver)
Special defenses of saliva
and organisms with a resultant tactic?
secretory IgA in saliva that selectively inhibits adherence of bacteria
Neisseria gonorrhœae (which causes gonorrhea), Strep pneumoniae, and Haemophilus influenzae type B all releases a protease that destroys IgA.
small intestine defenses
peristalsis flow of liquids shedding of epithelium peyers patches igA mucous
peyers patches
cells that are only in the ileum
– they sample antigen, initiate immune response in the mucosa, and activate T and B cells
body flora increase in numbers with…
distance from stomach
few in esophagus or stomach
common oral flora
Many anaerobes: a-streptococci, Neisseria spp., diptheroids (nonpathogenic corynebacteria), lactobacilli, spirochetes (treponema denticola), mycoplasma
B-hemolytic strep groups vs a-hemolytic strep groups
B - complete hemolysis
—pyogenes or agalactiae
a - partial hemolysis
—pneumoniae or viridans
a-streptococci types that is abundant in flora of mouth? throat?
viridans is more common in mouth
pneumoniae is more common in the pharynx/throat
viridans streptococci
streptococci with no defined Lancefield group antigens (Lancefield classification is based on carbohydrate antigens on the bacterial surface); normal flora of the respiratory tract but can cause dental caries, bacterial endocarditis, and other disorders in immunocompromised hosts.
6 types of strep viridans
c,mm,sss
- S. mutans = dental caries
- S. mitis = cheek region
- S. sanguinis, no preference of locations
- S. salivarius = dorsal side of the tongue
- S. salivarius ssp. thermophilus
- S. constellatus, occasional human pathogen,
the strep of dental caries
strep mutans
strep of cheek region?
strep mitis
strep of dorsal side of tongue?
strep salivarius
lactobacilli
Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are part of the lactic acid bacterial group, whose members convert lactose and sugars to lactic acid. In humans they are present in the vagina and the GI tract. They are typically benign, except in the mouth where they are associated with cavities/dental caries.
Periodontitis
requires bacteria to occur but that alone is not sufficient –> genetics and environment also play a role
periodontitis due to diabetes mellitus –
porphyromonas gingivalis
periodontitis with cardiovascular disease –
Porphyromonas gingivalis
Tannerella forsythia
T. denticola
pariodontitis with adverse pregnancy
porphyromonas gingivalis
common oral pathogens
B-streptococci staph aureus herpesvirus coxsackievirus HPV candida \+others
B-Streptococci
•may present as pharyngitis (strep throat), scarlet fever (rash), impetigo (infection of the superficial layers of the skin), or cellulitis (infection of the deep layers of the skin).
Invasive, toxigenic infections can results in necrotizing fasciitis, myositis, and strep TSS. Patients may also develop immune-mediate post-strep sequelae, such as acute RF and acute glomerulonephritis
staph aureus
- Coagulase-negative Staph
- Staph mucositis (stomatitis) in debilitate elderly patients
- Oral mucositis – inflammation of oral mucosa resulting from chemotherapeutic agents or ionizing radiation erythema or ulcerations
- Stomatitis – any inflammatory condition of oral tissue, including mucosa, dentition/periapices, and periodontium; Includes mucositis
Others GNR GPR GNC GPC
o GNRs: prevotella (+ B-lactamase), fusobacteria
o GPR’s: proprionobacterium, actinomyces
o GPC’s: peptostreptococci, peptococci, gemella
o GNC’s: veillonella species
herpesvirus
- **all herpesviruses have identical morphology and cannot be distinguished under electron microscopy.
- Linear double-stranded DNA; 150-200 kbp
- Icosahedral capsid, 162 capsomeres
- Infect mucousal epithelial cells and Replicate in the nucleus
- Viral particles bud through nuclear membranes and into membrane of exocytic vesicles
- HSV-1 typically causes oral herpes, but HSV-2 can cause oral infections if spread during oral sex
coxsackievirus
-type types?
- Picornaviridae family
- Enterovirus and a single stranded RNA virus – Infects host cells and cause them to lyse
Separable into 2 groups, A and B, which are based on their effects on mice
o A results in muscle injury, paralysis and death
Cause herpangina (painful blisters in the mouth, throat, hands, feet) = hand/foot/mouth disease; children
HPV
• Can infect oral and genital areas
o HPV is a major cause of squamous esophageal carcinoma!
candida
- Candida is a yeast, which is normal flora in some, but can cause infection when in the wrong location or in immunocompromised patients (HIV)
- upper GI tract disease = candidiasis or thrush (C. albicans is most common species)
- Candida are dimorphic – grow as ovid yeast cells or elongated pseudohyphal/hyphael cells
- The hyphael form is the virulent form
what form of candida is virulent?
hyphael
few normal flora in esophagus because of…
constant swallowing
immunocompromised patients infection….
Herpes/CMV, HPV & Candida
- HSV-1 infection of the esophagus is usually in immunocompromised
- Immunocompromised hosts — HSV esophagitis occurs most frequently in solid organ and bone marrow transplant recipients. HSV and CMV are the most commonly identified pathogens in esophagitis patients who have undergone bone marrow transplantation.
- HSV is a less common cause of esophagitis in patients with HIV infection than in transplant recipients. The most common cause of esophagitis in patients with advanced AIDS is candida, whereas the most common viral cause is CMV.
two normal organisms of stomach
lactobacilli and fusobacterium
main causative organism of gastritis/gastric cancer?
H pylori
H, pylori
Gram-negative Spiral shaped rod
Microaerophilic; Urease-positive
only environmental reservoir = humans and primates in 50% of stomachs
The only bacterium classified as a type I carcinogen by WHO
Colonizes gastric epithelium and induces a strong inflammatory response
h pylori gastric infection clearance?
- Inflammation never clears infection – people are chronically colonized unless treated with antibiotics
- People can get recolonized after they are treated with antibiotics if they are re-exposed
- One consequence of acute inflammation is ulceration on gastric epithelial surfaces.
H pylori gastric pathogenesis
1 - Binds to gastric mucosa; uses:Urease, mucinase, phospholipase, flagella
2 - Epithelial damage
o Urease, VacA (vacuolating cytotoxin), CagA (cytotoxin associated gene A)
3 - Chronic superficial gastritis (superficial inflammatory infiltration)
o Arginase, superoxide dismutase, catalase
4 - Chronic deep gastritis (deep inflammatory infiltration)
o Arginase, superoxide dismutase, catalase
5 - Early stage of chronic atrophic gastritis (CAG)
6 - Late stage of chronic atrophic gastritis (CAG)
7 - Gastric carcinoma (and/or intestinal metaplasia)
three important virulence factors of H pylori
urease
VacA
CagA
urease as h pylori virulence factor
survive pH stress by converting urea to ammonia and CO2
o UreI is a proton gated pore; UreAB (two subunits, A and B) catalyzes reaction
VacA
vacuolating cytotoxin
o Causes the formation of large, nonfunctional endosomal-lysosomal hybrids
o Induces mitochondrial membrane permeability and reduced transmembrane potential in a dose-dependent fashion
o Releases cytochrome and induce apoptosis
o Can inhibit the ability of T cell to become activated
CagA
pokes into cell and injects CagA directly into cytoplasm of cell
o Encoded on pathogenicity island; Modulates numerous host cell pathways
o Oncoprotein
three factors used in H pylori colonization?
urease
mucinase or phospholipase
flagella
three factors used in H pylori direct damage to tissue?
urease
VacA
CagA
h pylori defense against phagocytes?
SOD - superoxide dismutase
catalase
arginase
transmission of H pylori
• Exact route is unknown (likely oral-oral)
• Genetic fingerprinting studies show that isolates from an individual are identical; from unrelated individuals are different; from spouses are different; children are similar to isolates from one parent
• Suggests once a strain colonized, much genetic change occurs over time
• Not due to horizontal exchange with other bacteria
o Co-infections are rare
old gastric ulcers treatment dogma
caused by excessive acid, damages tissues and causes inflammation
o Bland diet, histamine, H2 receptor blockers, surgery to remove ulcers
o Success: ulcers recur if H2 blockers are discontinued
o Cost: H2 receptor-blockers cost $60-100 per month (for life)
new gastric ulcers dogma
caused by H. pylori infection causes inflammation and damage to tissue
o Antibiotic regimen (1-4 weeks) of one or two antibiotics plus antacid
o Success: no recurrence after completion of therapy
o Cost: two weeks of therapy costs
H pylori is protective against…
asthma
active TB
esophageal cancer
triple therapies for H pylori infection
1) omeprazole, amoxicillin, and clarithromycin
2) lansoprazole, amoxicillin, and clarithromycin
3) busmuth subsalicylate, metronidazole, tetraycline and H2 blocker
ways to detect h pylori infection
1) glemsa or wirthin-starry stain (histologically)
2) urease tests
3) culture
