Microbiology: Upper GI Flashcards
Why is secretory IgA necessary in saliva?
It can selectively inhibit adherence of bacteria to the teeth and mouth
What are the special defenses present in oral cavity?
Flow of liquids (saliva, drinking)
Lysozyme
Normal Flora
What are special defenses against infection present in the esophagus?
Peristalsis
Flow of liquids
What are special defenses against infection present in stomach?
Low pH
What are special defenses against infection present in small intestine?
Peristalsis
Flow of Liquids
Shedding of Epithelium
Peyer patches
IgA
Mucus
What are special defenses against infection present in the large intestine?
Normal flora
Peristalsis
Shedding of epithelium
What kinds of normal and abnormal flora are found in the oral cavity?
Normal:
Predominantly anaerobes
alpha strep
Neisseria
Diptheroids
Lactobacilli
Spirochetes
Mycoplasma
Abnormal:
(in tissues)
beta strep
Staph
Fusobacterium
HSV
Coxsackievirus
Candida
What kinds of normal and abnormal flora are found in the esophagus?
Normal:
Sparse flora
Abnormal:
Candida
HSV
What kinds of normal and abnormal flora are found in the stomach?
Normal:
Sparse flora
Lactobacilli
Fusobacterium
Abnormal:
Helicobacter pylori
Much more rare:
- HSV
- CMV
What kinds of normal and abnormal flora are found in the small intestine?
Normal:
Sparse flora
(Increasing in #’s with distance from stomach)
Abnormal:
E. coli
Rotavirus
Giardia
Cryptosporidium
(many more)
What kinds of normal and abnormal flora are found in the large intestine?
Normal:
Predominantly anaerobes
Coliforms
streptococci (enterococci)
Lactobacilli
Spirochetes
Abnormal:
Shigella
E. coli
Campylobacter
Entamoeba histolytica
Trichuris
What is the most common streptococcus bacteria found in the oral cavity and what does it cause?
Streptococcus viridans:
Can cause:
- dental caries
- bacterial endocarditis
- other disorders in immunecompromised hosts
What are the characteristics of lactobacilli?
Gram + rod
facultative anaerobic or microaerophilic
Part of lactic acid bacterial group
(converts lactose and other sugars to lactic acid)
Commonly found in GI tract and vagina
Typically benign, except in mouth, where they cause dental caries
What systemic conditions is periodontitis associated with?
Diabetes Mellitus:
Porphyromonas gingivalis
Cardiovascular disease:
P. gingivalis
Tannerella forsythia
T. denticola
Adverse Pregnancy Outcomes:
P. gingivalis
What is oral mucositis?
Inflammation of oral mucosa resulting from chemotherapeutic agents or ionizing radiation
- Typically manifests as erythema or ulcerations
- May be exacerbated by local factors
What is somatitis?
Refers to any inflammatory condition of oral tissue, including mucosa, dentition/periapices, and periodontium
- includes infections of oral tissues as well as mucositis
What are characteristics of HSV?
- Enveloped virus
- Icossahedral capsid
- Linear dsDNA
(replicates in nucleus) - Infects mucoussal epithelial cells
- viral particles bud through nuclear membranes and into membrane of exocytic vesicles during egress from host cells
Where are HSV-1 and HSV-2 infections generall found?
HSV - 1 is typically oral
HSV - 2 is typically genital
What are characteristics of coxsackievirus?
Picornaviridae family
- enterovirus
- ssRNA
- seen in children or immune compromised adults
What is the typical presentation of Coxsackie A infection?
Herpangina: “Hand, foot, and mouth disease”
- painful blisters on the mouth, throat, hands, feet, or in all these areas
(Not to be confused with “foot and mouth disease”)
Can also cause conjunctivitis, meningitis, myocarditis, and pericarditis
What is the typical presentation of Coxsackie B infection?
Pleurodynia:
- fever, lung and abdominal pain with headache that lasts about 2-12 days and resolves
- Can also cause: meningitis, myocarditis, and pericarditis
What are symptoms of an oral HPV infection?
papillomas and verruca vulgaris (wart) on the mouth and throat regions
What are the characteristics of candida albicans?
- Dimorphic fungi: has a yeast and a hyphael (virulent) form
- Can cause thrush or candidiasis in upper GI tract of children or immunecompromised
What are common causes of esophagitis (inflammation of the esophagus)?
- GERD
- Allergies: food allergies can cause eosinophilic esophagitis
- Some medications
- Some infections (esp. in immune compromised): candida, HSV, CMV
- Other causes: alcohol abuse, radiation therapy, nasogastric tubes, chemical injury
What are characteristics of Helicobacter pylori?
Gram negative rod
Microaerophilic
Urease +
Extracellular pathogen
No known environmental reservoir other than humans and nonhuman primates
Only bacterium classified as a type I carcinogen by WHO
What can result from a Helicobacter pylori infection?
Gastritis
Adenocarcinoma
Ulcers
(gastric or duodenal)
MALT lymphoma
(Mucosal associated lymphoid tissue)
How does an H. pylori infection result in ulcers and lead to gastric carcinoma?
- Bacteria binds to gastric mucosa and causes epithelial damage with:
Urease
Mucinase
Phospholipase
Flagella - Chronic superficial gastritis occurs (superficial inflammatory infiltration) due to:
Urease
VacA - vacuolating cytotoxin
CagA - cytotoxin associated gene A - Leading to chronic deep gastritis (deep inflammatory infiltration)
- Early stage of chronic atrophic gastritis
- Late stage of chronic atrophic gastritis
- Gastric carcinoma (and/or intestinal metaplasia)
What are the virulence factors of H. pylori?
Urease (to help it survive in low pH and overcome innate defense of stomach)
VacA
CagA
How does Urease affect H.pylori virulence?
UreI acts as a proton gated pore to allow urea into the bacteria, where it is converted to ammonia and CO2 by urease
How does VacA affect H. pylori virulence?
Vacuolating Cytotoxin (VacA) causes the formation of large, nonfunctional endosomal lysosomal hybrids and additionally appears to have numerous important roles in targeting mitochondria of cell to become permeable and release cytochrome c
Also inhibits T Lymphocyte activation
How does CagA affect H. pylori virulence?
CagA has been shown to be an oncoprotein
and H.pylori with Cag islands are more likely to cause gastic cancer
How is H. pylori diagnosed?
Breath tests (looking for ammonia)
Biopsy with Giemsa or Wurthin-Starry stain
Urease test (from media innoculated with biopsy sample)
Culture
Antibody serology
