Microbial Contamination of Water Presentation PDF

MICROBIAL CONTAMINATI ON OF WATER  indications 1. Outbreak investigation 2. Change in infection control practice 3. Construction( especially OT) 4. Research purpose  WATERBORNE PATHOGENS...

MICROBIAL CONTAMINATI ON OF WATER  indications 1. Outbreak investigation 2. Change in infection control practice 3. Construction( especially OT) 4. Research purpose  WATERBORNE PATHOGENS HOSPITAL PATHOGENS A threat to critically ill and immunocompromised ENTERIC PATHOGENS Spread:- Fecal contamination of drinking water. Incidence: Greater POTABLE WATER in community settings as compared to hospitals. Major disease:- ICE MACHINES Diarrhea  Examples of enteric Bacteria pathogens Virus Parasites Vibrio cholerae- rice water stools Shigella - bacillary dysente ry Examples of common hospital pathogens MULTIDRUG RESISTANT GRAM NEGATIVE PATHOGENS Legionellae  FEATURES:- Present in excess Indicator More resistant than organisms:- COMM pathogens to Commensal disinfection and aquatic ON envionment bacteria in intestine. TYPES What does it indicate? Contamination of sewage with enteric pathogens. COLIFORM ( other than E coli) Remote contamination by FECAL(THERMOTOLERANT ) fecal/soil/vegetation E.coli:- Ferments lactose at 44.50C. Other organisms BEST INDICATOR FOR Clostridium perfringens, CONTAMINATION:- time of Pseudomonas aeruginosa  Collection:- TAP SWABS Screw capped wide 1. Insert sterile swab into sterile nozzle of tap( without container touching tap surface) Screw capped wide sterile container with sodium thiosulphate in it 2. Rub the swab backwards and forwards and up and Volume:- 150-200 mL down on inside surface of tap or flow Neutralizer:- Sodium thiosulphate straightener. to neutralize the bactercidial effect of residual chlorine Sampling technique precautions:-  WHO,1996 1. Clean the tap. Remove any attachments that may cause splashing from the tap. These attachments are a frequent source of contamination that may influence the perceived quality of the water supply. Use a clean cloth to wipe the outlet and to remove any dirt. 2. Open the tap. Turn on the tap to maximum flow and let the water run for 1-2 minutes. Turn off the tap. Note: Some people omit the next two steps and take the samples at this stage, in which case the tap should not be adjusted or turned off, but left to run at maximum flow. 3.. Sterilize the tap for 1 minute with a flame (from a gas burner, cigarette lighter or an alcohol-soaked cotton wool swab). 4. Open the tap before sampling. Carefully turn on the tap and allow water to flow at medium rate for 1 - 2 minutes. Do not adjust the flow after it has been set. 5..Fill the bottle. Carefully remove the cap and protective cover from the bottle, taking care to prevent entry of dust that may contaminate the sample. Hold the bottle immediately under the water jet to fill it. A small air space should be left to allow mixing before analysis. Replace the bottle cap. SAMPLING SITES  DETECTION OF MULTIPLE TUBE METHOD MICROBIAL CONTAMINATION OF WATER MEMBRANE FILTRATION METHOD  Most common method Incubation period :- 24 -48 hours Medium:- MacConkey purple broth. Tube:- Durham’s tube Procedure:- Specific volume(100 mL) of water is mixed with MacConkey purple broth 50 mL water+ 50 mL culture medium 10 mL water+ 5 tubes having 10 mL culture medium each. Positive:- 1.Change in color from yellow to purple( due to lactose fermentation) 2.Turbidity of medium 3. Gas formation. DISADVANTAGE:- Cannot differentiate between fecal E.coli and other bacteria.  DIFFERENTIAL COLIFORM COUNT (Ejkman’s test)- Indicates E.coli DIFFERENTIATIO Lactose fermentation along N OF E.COLI with acid and gas at 440C FROM OTHER Positive indole test at440C COLIFORM BACTERIA MOST PROBABLE NUMBER ( MPN) Number of tubes giving positive reaction is compared with McCrady table This determines the MPN of coliform count per 100 mL of water Presumptive coliform count Intermediate or  100 mL of Water through a cellulose membrane of MEMBRANE FILTRATION METHOD pore size 0.2 or 0.45 micrometer. Advantages:- Testing dialysis water Testing clean water, with low bacterial count Large volume of water Disadvantages:- Unsuitable for turbid water Expensive as compared to multiple tube method. IDEAL WAY TO TEST WATER CONTAMINATED WITH PATHOGEN:- MEMBRANE FILTRATION METHOD SUITABLE CULTURE MEDIUM PLATING  ENDOTOXIN PERMISSIVE LEVEL:-