Bacterial GI Pathogens Flashcards

Question

Shigella

Answer 1

Four species: S. sonnei: industrial world S. flexneri: developing world S. dysenteriae: most severe infection 1. Gram- in Enterobacteriaceae family 2. Contaminated food/water, person to person; fecal oral 3. Low ID <200 to establish infection (very small inoculum) 4. Humans are the only reservoir 5. Invade mucosal cells, proliferate, cause mucosal damage (T3SS) - intracellular growth 6. Mucosal ulcers may form pseudomembranes 7. Resistant to gastric acid (survive low stomach pH) 8. Diarrhea, dysentery, fever, ab pain, prolonged course; common cause of diarrheal death in children 9. HUS from Shiga toxin 10. Non-motile, lactose negative

Answer 2

1. Shigellosis: Gastroenteritis incubation 1-3 days Watery diarrhea>ab cramps with bloody stools and tenesmus ``` 2. Dysentery: Mostly caused by S. dysenteriae Frequent passage of small volume of bloody, mucous stools and tenesmus Causes seizure in children <2 years Some strains cause HUS ``` Post infection sequelae: Reiter's syndrome (arthritis, conjunctivitis, urethritis)

Answer 3

1. Orally ingested bacteria survive low stomach pH 2. Taken up by M cells only (microfold) 3. Escape from vesicle 4. Phagocytosis into macrophage 5. Entry into epithelial cell 6. Escape from vesicle 7. Actin transport into next epithelial

Answer 4

1. T3SS-mediated invasion (plasmid) Important effectors cause macrophage apoptosis, endocytosis, phagosome lysis 2. Shiga toxin: cause host cell damage and death Causes HUS B binds GB3, A1 inactivates 60s ribosomal subunit Hemolysin: vacuolar escape (pore forming toxin) intracellular spread via actin polymerization (ICS)

Answer 5

1. Appropriate environment and personal hygiene 2. Rehydration for mild to moderate shigellosis 3. Antibiotic treatment for bloody diarrhea and dysentery DOC: Ciprofloxacin Levofloxacin Ceftriaxone

Answer 6

S Asia (indian subcontinent), Gulf of Mexico Contaminated water; small inoculum Non-invasive, minimal mucosal changes Vomiting, watery diarrhea, massive fluid loss "Rice water stools" Dehydration, hypovolemic shock, death Oral rehydration key to recovery NOt common in US

Answer 7

1. dsRNA virus, encapsulated 2. Common cause of diarrheal mortality in CHILDREN worldwide 3. Protection by maternal antibodies in first 6 mo of life 4. Vaccine available (2 oral) 5. Contaminated food/water; person to person Fecal oral 6. Small inoculum 7. Short incubation period 8. Nausea, vomiting, watery diarrhea, ab pain, low grade fever 9. Destruction of mature enterocytes with loss of absorptive surface 10. Infection of mucosal cells of small intestines

Answer 8

1. ssRNA of Caliciviridae 2. MOST common cause of acute gastroenteritis in US; second most common cause in severe diarrhea among children 3. Contaminated food/water; person to person; fecal oral 4. Low inoculum 5. Cruise ships, schools, camps, hospital 6. Short incubation period 24-72 hours then recovery 7. Nausea, vomiting, watery diarrhea, ab pain Low grade fever 8. Mild mucosal abnormalities/bowel 9. Self-limited, could lead to intermittant diarrhea w nutritional disturbances if not cleared No vaccine

Answer 9

1. Attachment (fimbriae), membrane ruffling (SPI-1 T3SS effectors), phagocytosis 2. Block of phagosome-lysosome fusion (SPI-2 T3SS effectors) and intravacuolar growth 3. Host cell death and spread to adjacent epithelial cell and lympoid tissue 4. Inflammatory response, release of prostaglandins, stimulation of cAMP, diarrhea OR S. typhi: 3. Taken up by submucosal macrophages 4. Transported to liver, spleen, bone marrow, replication, release 5. Gallbladder infection > reinfection of intestines

Answer 10

1. DNA non enveloped virus 2. Military uses vaccines 3. Fecal oral or direct inoculation 4. Attaches to cell then penetrates, uncoats, DNA migrates in; New virions are released with cell lysis 5. Pharyngitis, respiratory disease, conjuctivitis, hemorrhagic cystitis, nonbloodly diarrhea

Answer 11

1. DNA enveloped 2. Saliva, semen, cervical, blood and organ TRANSPLANTation 3. Oral, esophagus, bowel, liver (mononucleosis syndrome) 4. Can be asymptomatic Enters latent stage in monocytes and can be reactivated 5. After early protein synthesis, viral DNA polymerase replicates genome, DNA and late protein synthesis start 6. Structural proteins assemble virion which buds through the nuclear membrane and exits via tubules 7. Retinitis, esophagitis, mononucleosis, colitis, pneumonitis, systemic disease with fever, BONE marrow suppression 8. 80% of adults have been infected; acute disease can transmit fetal disease; likely reactivation

Answer 12

1. RNA enveloped 2. Vaccination lasts >10 years 3. Oral (parotitis) 4. Soluble Ag can be detected by complement fixation

Answer 13

1. Enveloped DNA 2. Oral (hairy leukoplakia, pharyngitis), liver (mononucleosis syndrome), cervical adenopathy (lymph nodes in neck) 3. Viral capsid antigen 4. Infects mainly B lymphocytes and epithelial cells of throat 5. 90% of Americans have antibody to EBV. Associated with hairy leukoplakia and cancers

Answer 14

1. Fecal oral or respiratory transmission 2. Oral herpangina Hand Foot Mouth 3. Virion enters cell, uncoats, mRNA translated to large polypeptide cleaved and forms capsid + noncapsid proteins Complementary RNA strands formed and RNA is coated with capsid proteins which are released at cell death A: Herpangina (blistered legions in back of throat), Conjuctivitis B: Myocarditis, pericarditis, pleurodynia, aseptic meningitis No vaccine

Answer 15

1. Anti-herpes 2. Inhibition of viral Genome Replication 3. Oral, IV or topical 4. Guanosine analogue; activted by viral thymidine Kinase (TK) Initial phosphorylation requires viral kinase. Acyclovir is substrate for viral polymerase. Incorporation of acyclovir causes chain termination and inhibition of DNA polymerase. TK- viruses resistant 5. Manage/suppress (cannot cure) HSV 1 and HSV 2. Given to transplant patients for prevention

Answer 16

1. Anti-herpes 2. Inhibition of viral Genome Replication 3. Dosed twice a day instead of 3-5. More expensive 4. Pro-drug. Cleaved by esterases to yield acyclovir 5. Treat HSV 1 and HSV 2. Same effect as acyclovir, but more expensive and requires less dosage

Answer 17

1. CMV Treatment - IV 2. Inhibition of viral Genome Replication 3. Myelosuppression (25-40% of patients)- bone marrow suppression 4. Requires phosphorylation by viral specific enzyme. Doesn’t have thymidine kinase like HSV so acyclovir doesn’t work. CMV gene codes for phosphotransferase that converts ganciclovir to a monophosphate Then enzymes in infected cell convert monophosphate to triphosphate that gets high levels in cell and helps stop CMV DNA from elongating. 5. Treatment for CMV. Not as selective as acyclovir so more toxic. Side effects: GI, neuropathies, some CNS, carcinogenic in animals at high doses.

Answer 18

1. CMV and Resistant Herpes Viruses 2. Not nucleoside analogy - instead pyrophosphate 3. IV 4. Binds to and directly inhibits viral polymerases (DNA, RNA and RT) 5. Treatment: Effective against ganciclovir - resistant CMV and acyclovir resistant HSV, VZV

Answer 19

1. Anti-herpes 2. Cytosine nucleotide analog 3. IV 4. Phosphorylated by host kinases (so also active against thymidine kinase deficient HSV) competitive inhibitor of viral DNA synthesis, incorporated into viral DNA 5. CMV third string drug. If Ganciclovir and forcarnet don’t work

Answer 20

1. Anti-herpes 2. Competes with TPP at viral polymerase 3. Topical 4. Competes with TPP at viral polymerase Inhibits DNA synthesis in HSV1 HSV 2 CMV Incorporates into both viral and host DNA 5. Used for HSV 1 and HSV 2 conjuctivitis, epithelial keratitis. Effective for acyclovir-resistant HSV

Answer 21

1. Antibiotic-associated, usually due to C. diff 2. C. diff overgrowth due to disruption of normal bowel flora 3. Pseudomembranes Adherent layer of inflammatory cells and debris 4. Fever, leukocytosis, ab pain, watery diarrhea, dehydration 5. Major concern in healthcare facilities

Answer 22

Parasite 1. Non-invasive diarrhea 2. Treat with oral rehydration and anti-protozoan agents

Answer 23

Parasite 1. Water borne, spores resistant to chlorine Spread through pools 2. Acute self-limited diarrhea or chronic in immunosuppressed host

Answer 24

1. DNA enveloped virus 2. Bind on cell surface, travel to nucleus to become circular, activates viral immediate early genes by host RNA polymerase and create proteins DNA + thymidine kinase 3. HSV1: Oral>sexual; Very sore mouth gingivostomatitis, herpes labialis on vermillion border, keratitis and encephalitis HSV2: Sexual>oral; herpes genitalis/labialis, neonatal encephalitis, aseptic meningitis

Answer 25

IgM = more fast acting than IgG Core = Actually had the illness Surface antigen = active disease No igG or igM = no immunity, never been infected or vaccinated Surface antibody = shows vaccination or previous manifestation

Answer 26

``` Telaprevir Simeprevir Sofosbuvir Daclatasvir Velapatasvir ``` Knowing genotype Current HepC viral lode Degree of fibrosis/cirrohosis Liver biopsy will show cirrhosis Ultrasound elastography can show fibrosis Na+ shows prognosis in patients with end stage liver disease Alpha fetal protein tumor makers helpful with HCC FibroTest-ActiTest used to stage fibrosis and evaluate for cirrhosis

Answer 27

Fecal oral Acute 2-6 week incubation Councilman bodies (represents a dying hepatocyte surrounded by normal parenchyma)

Answer 28

Fecal oral Acute 2-8 week incubation Could only progress to chronic hep in immunocompromised patients India No vaccination

Answer 29

No vaccination

Answer 30

The level A suggests that Data is derived from multiple randomized clinical trials, meta-analyses or equivalent. Level B would be a single randomized trial, nonrandomized studies, or equivalent Level C would mean Consensus opinion of experts and case studies.

Answer 31

After needle stick, risk of infection is 1.8% If HepC is acquired, 15-25% chance of clearing it Wouldn't make sense to treat it even though newer medications have better side effect profiles Baseline testing with follow up 2-3 weeks for Hep RNA

Answer 32

Ribavirin with interferon A

Answer 33

1. Common in adults, common cause of traveler's diarrhea 2. Contaminated food/water; small inoculum 3. Mucosal colonization and adherence 4. Watery diarrhea, dysentery (uncommon); usually self-limited 5. Arthritis - HLA-B27 Guillain-Barre syndrome 6. Curved Gram- rod Jejuni 1. Symptoms like ulcerative colitis or Crohn's disease