FH II Lab 1 Flashcards
Water borne pathogens
Bacteria - Vibrio, Salmonella, Shigella, Campylobacter, E. Ecoli (ETEC), Listeria, Staph Aurues, Clositrtidium
Viruses; Calicivirus, Hep A
Protazoa: Giardia intestinalis, Toxoplasma gondii, Cryptosporidium, Entamoeba
Worms: tricinhellaw, Taenia, Echinoccoccus
Indicator Microbes
- Found in all types of water, Drinking, waste, sea, lake river
Not an obligate pathogen
Long survival time
Quantity is in direct correlation with the degree of face contamination
Specific and easy detection
Micrbiologicalk requirements of drinking water
Coliform
E.coli, Enterococci
P. Aerunginosa
0/100ml
Sulphote reducing clostridium spores; 0/50ml
Microbiological requirements of bottled water
total count @ 22º 100/ml
@ 37º 20/ml
Coliform, E.coli, enterococci . P. Aerunginosa : 0/250 ml
Heterotrophic aerobic bacteria
General medium at 22º and 37º
Long term examination - changes
Sudden increase –> inadequate cleaning / disinfection
Requirement of bottled water
Detecting heterotrophic aerobic bacteria
Pour plate method, 22 and 37º, parallel plates
1ml of the undiluted samples (low limits, no dilution)
General medius, plate count
22º 100/ml 3 days
37º 20/ml, 2 days
Total Coliform bacteria
Enterobacteriaceae family
• Brillant green-bile-lactose broth: acid and gas
(37°C, 1-2 days)
• Beta-galactosidase enzyme
• Escherichia, Klebsiella, Citrobacter, Enterobacter
• No health risk
• Associated with fecal contamination
• Information about the microbiological status
Escherichia coli
Enterobacteriaceae family • Beta-glucuronidase enzyme • Beta-galactosidase enzyme (all Coliforms) • IMViC tests • Indole + • Methyl red + • Voges-Proskauer – • Citrate –
- Human / animal feaces: 109 cfu/g
- Direct indicator of fecal contamination
Total coliform bacteria and E. coli: Detection method
Membrane-filtration method
• 100 ml (drinking) / 250 ml (bottled) water sample • Chromogen coliform agar
• Incubation: 37°C, 1 day
Evaluation
• Coliforms: pink–>Confirmation: oxidase negative
• E. coli: violet–>No confirmation needed
• Coliform count: oxidase negative pink + violet colonies
• E. coli count: violet colonie
Enterococci and faecal Streptococci
- Feaces
- Streptococci = Gram positive cocci –> chains
- Enterococci = high tolerance of NaCl and alkalines
- Reduce 2,3,5,-triphenyl tetrazolium chloride to formazan
- Indicator of feacal contamination
- More resistant to disinfection than coliforms
- Indicator of inadequate disinfection (chlorination)
Enterococci: Detection method
- Membrane-filtration method
- 100 ml (drinking) / 250 ml (bottled) water sample
- Slanetz-Bartley agar
- Triphenil-tetrazolium chloride (TTC)àFormazan: RED • Sodium azide: Gram negative inhibitor
- Incubation: 37°C, 2 days
- Confirmation:
- Typical colonies: red / brown
- The membrane is placed onto bile-aesculin-azide agar
- 44°C, 2 hours
- Yellow / brown / black color around the colonies
P. Aeruginosa
- Gr -ve rod
- Oxidase +
- water, soil, faeces and waste water
- NOT feral contamination
- General cleanliness of the the system, sluggish flow rate
- unpleasant odor and flavour, turbidity
Culturing P. A
- can grow on medium containing cetrimide, product piocyanin, green
- able to grow on medium containing cetrimide, oxidase postive, fluorescent under UV Acetamide broth (+messler reagent) --> ammonia, (brownish red)
Sulphite-reducing Clostridium spores
- Obligate anaerobic
- Spore-forming
- Spores: persistent, resistant to disinfection
- Inadequate filtering
- Possibility of protozoa cysts
- Clostridium perfringens: natural member of faecal microflora
- Requirement of drinking water
Sulphite-reducing Clostridium spores Detection etc
- Heat treatment: 80°C, 15 minutes
- Destruction of vegetative cells
- Activate spores
- Membrane filtration
- 100 ml (drinking) water sample
- Sulfide-iron agar OR Tryptose-sulfite agar
- Incubation: 37°C, 1-2 days, anaerobic conditions (aerostat, CO2 atmosphere)
- Evaluation: black colonies = Clostridium spp. (no confirmation needed)
