microb report

Bacteriological Examination of Water

INTRODUCTION
This paper presents the results of the quantitative bacterial examination of domestic water in the Tasek Pedu. Also studied were the hygiene and health of the water samples. The water samples from the Tasek Pedu were tested for bacterial existense.. Three test wee being perfomerd which The Presumtive Test, The Confirmed Test and The Completed Test are based on the estimation of the total number of coliforms, which is a nonspecific indicator of water quality.The findings of the experiments are clearly to determined the bacterial forms in the water smples.

Escherichia coli (E. coli), a rod-shaped member of the coliform group, can be distinguished from most other coliforms by its ability to ferment lactose at 44°C, and by its growth and color reaction on certain types of culture media. When cultured on an EMB plate, a positive result for E.Coli is metallic green colonies on a dark purple media. Unlike the general coliform group, E. coli are almost exclusively of fecal origin and their presence is thus an effective confirmation of fecal contamination. Typically, E. coli are about 11% of the coliforms in human feces.
OBJECTIVE :
a) to test the presence of the bacterial in water samples
b) to determined the type of the coliform either its Gram-positive or Gram-negative
c) to indicates the level of the safety of the water.





METHOD :

The Presumptive Test

The double strength of lactose broth (DSLB) agar was poured into 6 bottles of Durham tubes which contains 10 ml in each.
The single strength of lactose broth (SSLB) agar was poured into 12 bottles of Durham tubes which contains 1.0 ml for the first 6 bottles and 0.1 ml for another 6 bottles.

a) The bottle of water was mixed by shaking 25 times.
b) 10 ml pipette was used to transfer 10 ml of water to each of the DSLB tubes.
c) 1 ml pipette was used to transfer 1ml of water to each of the SSLB tubes.
d) The tubes were incubated at 35 C for 24 hours.
e) After 24 hours, the tubes were examined and recorded in each set that have 10% of gas or more.
f) The MPN was determined by referred to the table.




figure 1 figure 2
The water samples are tested in the lactose broth agar.



The Confirmed Test
a) One positive lactose broth tube was selected from the presumptive test and streaks a plate of medium according to your assignment. A streak method was used that will produce good isolation of colonies.
b) The plate was incubated for 24 hours at 35 C
c) The tipical coliform was observed and recorded.



Figure 3 Figure 4

Figure 3: The sample water was streaking on the Endo agar plate
Figure 4: The plate was sealed.












The Completed Test

a) The final check for the existence of the colonies was checked.
b) The media was inoculated on the agar slant and a Durham tube lactose broth.
c) The lactose broth was examines after 24 hours for gas production.
d) The slide was examined under the oil immersion optics.
e) The result was recorded.












Figure 5 Figure 6

Figure 5: The colonies on the endo agar are inoclulate
SFIgure 6: treak the medium on the slant agar






RESULT

1) Presumptive Test (MPN Determination)

WATER SAMPLE NUMBER OF POSITIVE TUBES MPN
3 TUBES DSLB 10 ml 3 TUBES OF SSLB 1.0 ml 3 TUBES OF SSLB 0.1 ml
SET A 3 1 1 75
SET B 2 1 0 15








Figure 7 : Gas production in the sample of lactose broth













2) Confirmed Test

WATER SAMPLE
(SOURCE) POSITIVE
(PLATES) NEGATIVE
(PLATES)
SET A (ENDO AGAR) 2 4
SET B (EMB AGAR) 1 5



Figure 8 : The colonies on the Endo agar plate


Figure 9 : The colonies on the Endo agar plate


Figure 9 : the colonies formed on the Levine EMB agar
3) Completed Test

WATER SAMPLE
(SOURCE) LACTOSE FERMENTATION RESULTS
A POSITIVE
B POSITIVE
C POSITVE



DISCUSSION

From the experiment, we had test the water sample from Tasek Pedu to test either it’s contain any coliform which unsafe to health. We get the result as above which some of the Durham test tube contain sample water in lactose broth was produce bubble. For the presumptive test, we observed that MPN for the Set A was 75. This means the sample water A would have approximately 75 organisms which probably contains 14 to 230 organisms per 100 ml of water. Meanwhile, the sample water of set B had record 15 MPN index. So, we assumed that the probability of existence organisms in 100ml of water between 3 and 44 organisms for set B.

After that we take another test, the Confirmed Test on 3 plates of Levine EMB agar and 3 plates of Endo Agar to confirm the presence of the Gram-negative lactose fermenter. These agars will inhibit the Gram-positive organism, so we can indicates the performing of the Gram-negative organisms on that samples. For this method, we use streaking techniques to get the single colony of the bacteria. Finally the result after 24 hours, only 3 plates formed the coliform which were one plate for the EMB agar and another 2 plates for the Endo agar. On the EMB agar plate, we observed that the greenish metallic shine were presence that means refer to the existence of E. coli or E. aerogenes in that water samples. Meanwhile on the Endo Agar, coliform colonies and the surrounding medium appear red. The effect of the medium colour showed that the coliform were performed.

Then, the last step was we did the test of Completed Test which we inoculated that three confirmatory media on the nutrient agar slant and Durham tube of lactose agar. After 24 hours, a Gram-stained technique was being done to prove the existence of the Gram-negative organisms. The results were all the samples were having Gram-negative which the non-spore-forming rod ferment the lactose on the slant agar and the gas was produced in the lactose tube.
Conclusion, the water of Tasek Pedu are not safe enough to human consume because the proof of the experiments that there are pathogens exist in the water.


REFERENCES:
-Lab manual
- http://www.popline.org/docs/1315/147133.html
- http://en.wikipedia.org/wiki/Coliform_bacteria












QUESTION:

1. Does a positive presumptive test mean that the water is absolutely unsafe to drink?
-No. This not enough to prove the water contain the unsafe organisms. We do not know the type of the organism yet, either its safe or not. From this test, we just only know that the coliform are present from the gas production.



2. What might cause a false positive presumptive test?
- the existence of air bubbles might be miss understood as gas production.



3. List three characteristics required of a good sewage indicator
a) the organisms can be easily identified by microbiological test.
b) it is not as fastidious as the intestinal pathogens,
c) survive longer in water samples.

4. What enteric bacterial disease transmitted in polluted water?
Diarrhea

5. Name one or more protozoan disease transmitted by polluted water
E. Coli and E.aerogenes

6. Why don’t health departments routinely test for pathogens instead of using a sewage indicator?
-its more easier because the sewage indicator will indicates the existence of the pathogens

7. List five characteristics of coliform bacteria
a) rod-shaped Gram-negative non-spore
b) can ferment lactose with the production of acid and gas
c) abundant in the feces of warm-blooded animals
d) coliforms themselves are not the cause of sickness
e) easy to culture

8.How is each of the collowing media used foe the detection of coliform?
a) lactose broth with Durham tube = producing gas
b) Levine EMB agar = the result shown “nucleated colonies”
c) nutrient agar slant = producing acids

9. Once the completed test established the presence of coliform in the water sample, why might you perform the IMV thest on these isolates?
Because the test is not enough to identify either the coliforms formed is E.coli or E.aerogenes. so the IMV test will make the certainty of it.