Lecture 22 Flashcards
Enteric bacteria
bacteria that cause gastrointestinal illness by using food or water (usually) as a way of getting into the gut
Food Borne Bacterial diseases
2 types
-caused by exotoxins
- Food poisoning
- Release exotoxins into food
- 4-6 hours symptoms
- consumption of live bacteria not required - Food infections
- Bacteria present and consumed
- release exotoxins in gut
- live consumption required
- 18-24 hours
Common contributing factors linked to food borne illness
- Improper refrigeration (food left at room temperature) - 43%
- Insufficient or improper cooking - 13%
- Food handlers who are ill or are asymptomatic carriers - 12%
- Contaminated raw foods and ingredients - 7%
- Too long a time between preparation and consumption
- Insufficient reheating
- Cross-contamination from raw to ready-to-eat foods
- Inadequate hot holding temperatures
- Inadequate hand washing
- Improper cleaning of equipment and utensils
- Staphylococcus aureus (Food Poisoning)
Persons who are asymptomatic carriers of S. aureus (in nose or on skin) contaminate foods they are working with
high-sugar / high-salt foods (favor growth of S. aureus), and foods that require more handling during prep, or left at room temp for long allows growth in food (exotoxin [Enterotoxin A])
Cured meats (ham, pork) egg, potato, pasta salad, cream filled pastries
Heating food to 100 degrees will kill staph not toxin
- Staphylococcus aureus (Food Poisoning)
Symptoms and prevention
prevents absorption of liquid (diarrhea)
stimulates nerve receptors in gut (nausea and vomiting)
Rapid symptoms 4 hours due to preformed toxin
Recover in 18 hours once clears gut
Prevention: refrigerate, take care in food handling
- Escherichia coli O157:H7 (Food Infection)
E. coli O157:H7 = “Enterohemorragic” strain of E. coli
“O157” = type of LPS “O” side chain (eg. 157th type)
“H7” = type of flagella antigen
- Escherichia coli O157:H7 (Food Infection)
Reservoir
Pathogenesis
Symptoms
Diagnosis
Treatment
Possible complications
Control
Intestinal tract of cattle (come into contact with cow feces)
-contaminated process, untreated water
E.coli attach to gut wall via pilli then grow
-secrete exotoxin dmging intestinal tract
Nausea, abdominal cramping, bloody diarrhea (5-7 days)
Stool culture (grow and id) look for symptoms (bloody diarrhea)
fluid replacement, anti diarrhea meds will increase E.coli stay(don’t use), antibiotics make symptoms worse
Hemolytic Uremic Syndrome (HUS)
-exotoxin enters blood, lysis of red blood cells and kidney dmg (high risk kids)
Vaccinate cows (not people) Avoid exposure
- Vibrio cholerae (Water-borne transmission)
causative agent of cholera
gram negative, fecal oral route
Small intestine, large # bacteria needed to cause disease (acidic stomach)
-attach via pili release cholera toxin
water treatment important
- Vibrio cholerae (Water-borne transmission)
Symptoms
Prevention
Hypersecretion of water from gut cells (no physical dmg like coli)
severe diarrhea (20 L) dehydration, leading to increased blood viscosity
need fluid replacement
Purification of drinking water, no raw sewage, raw food washed in contaminated water
-Dukoral Vaccine (killed whole vibrio cell, 2 year protection for travelers)
Review: Diagnostic Procedures used in Clinical Microbiology
Bacteria 5
Viruses 1
Fungi 2
Parasite 1
Gramstain + microscopy serology (antibodies in serum) nucleic acid amplification (pcr) test -growth on media + biochemical id antibiotic susceptibility testing
Serology, Pcr
Direct microscopic
growth on media
direct microscopic exam of specimen
Steps in diagnostic process
2
- Make preliminary diagnosis based on symptoms
2. collect specimen for lab
critical aspect, collect right specimen, at right time, right way
Right specimen
contains pathogen
depends on symptoms
-GI = feces
-resp = sputum, nasopharyngeal swab
nero = cerebrospinal fluid
testing methodology
-serological require blood
Right time
Before antimicrobial agent given
(antibiotics interfere with growth)
While pt showing symptoms
Right way
Collection device
- swabs “transport media”
- containers for urine/feces
sterile before use (normal flora introduced)
label
The main reasons why specimens are rejected by the lab
- Unlabeled / Improperly labeled / Incomplete requisition
- Collected with the wrong swab, wrong container, etc.
- Leaked in transit
- Inadequate volume
- Single specimen submitted for multiple tests(eg. aerobes, anaerobes, fungus, etc. require separate specimens )
- Delayed in transit to lab / improperly stored during transit
ASK LAB IF NOT SURE
