Coliform Detection in Irish Waters

1
Coliform Detection in Irish Waters
Manika Poply Adaptive Sensors Group
Abstract Water is a very critical part of the
human life. The contamination of this vital
element, with pathogenic microorganisms such as
Coliform Bacterias, due to faeces constitute a
serious threat to public health. The current
Coliform detection methods rely on the growth to
visible colonies. Therefore, they take a minimum
of 18-24 hours which is unacceptable in the case
where an immediate action has to be taken.
Results of this research showed that the sea
water had comparatively lesser number of
Coliforms than in the fresh water. Although, in
all samples both the total and faecal Coliform
content fairly exceeded the Guide limits given by
the Irish EPA. Thus, these high numbers have to
be controlled and monitored regularly for the
health and safety of general public.

• Introduction
• Escherichia coli commonly known as E. coli, a
  Coliform Bacteria is an indicator of faecal
  contamination of water.
• It can cause gastroenteritis, neonatal
  meningitis, peritonitis, pneumonia and many other
  serious urinary tract infections.
• Coliforms in water could be efficiently detected
  using number of standard methods namely Plate
  count, Most Probable Number, Petri films and
  Membrane Filtration.
• The advantages and disadvantages of all the
  techniques shown in Table 1. concludes Membrane
  filtration as the best Standard reference method
  and water samples were analysed using that
  technique.
• For the Comparisons and confirmation of results,
  Petrifilms were also prepared in duplicates for
  each sample.

• Results
• Membrane Filtration Petri dishes containing
  Membrane Lauryl sulphate Broth show Red coloured
  colonies for Total Coliforms (see Figure 3),
  whereas deep yellow colonies for E. coli
• Blue colonies entrapped in gas on Petrifilms in
  Figure 4 are counted as E. coli, whereas both
  Blue Red colonies with gas are interpreted as
  Total Coliforms.

Figure 3. Petridish showing red coloured Coliform
colonies (http//www.pall.com/images/1.r2_.jpg)
Figure 4. 3M Petrifilms showing the results for
Tolka water sample at 10-1 dilution.

• Experimental Results of Figure 5 and 6 clearly
  shows that none of the samples complied with the
  EPA Directive Guide Limits.

Irish EPA Guide Limits TC 500cfu/100ml
FC 100cfu/100ml
Table 1. Comparison of Different Standard
Microbial Detection Methods.

• Methods
• Membrane Filtration 0.1ml, 1ml and 10mls of
  Water sample were filtered individually through
  the cellulose membrane filter (0.45µm pore size).
• The membrane filter was placed in a small Petri
  dish with Absorbent pad and Membrane Lauryl
  Sulphate Broth (Specific for growth of
  Coliforms), see Figure 1.
• The Petri dishes were incubated for 24 hours at
  37ºC and 44ºC for the growth of Total and Faecal
  Coliforms respectively.
• Few confirmation tests such as Indole, Oxidase,
  Tryptone water and lactose peptone broth were
  also carried out for the confirmation and
  differentiation of bacteria as E. coli (Faecal
  Coliforms) or Total Coliforms.

Figure 5. Representation of Number of Total
Coliforms in colony forming units in various
water samples
Figure 6. Representation of Number of Faecal
Coliforms in colony forming units in various
water samples
TC Total Coliforms, FC Faecal Coliforms

• Conclusion
• All the Irish Public Water samples were fairly
  off the EPA Guide limits for Total and Faecal
  Coliforms.
• The Sea Water and the Galway Bay sample were
  found to have the least Number of Coliforms,
  whereas Fresh waters of Tolka, Broad meadow and
  Corrib river showed high numbers.
• Future Work
• Correlations of the above results could be done
  with turbidity measurements in order to get
  results sooner in the mobile device.
• Development of an instant and efficient device
  for continuous and rapid monitoring of water.

Figure 1. Step wise procedure of Membrane
filtration (http//www.pall.com/34696_7290.asp729
1)

• Petrifilms Commercially available
  sample-ready-culture medium systems for
  enumeration of E. coli and Total Coliforms were
  used (See Figure 2.)
• 1ml of water sample was placed on the Petrifilm
  and results were interpreted after incubation at
  37º C for 24 to 48 hours.

Figure 2. 3M Petrifilms for E. coli and Total
Coliforms (http//solutions.3m.com/wps/portal/3M/e
n_US/Food_Industry/Home/Prod_Info/Products/Microbi
ology/Petrifilm_Plates/)