Salmonella spp. and Campylobacter spp. (Campylobacter coli and Campylobacter jejuni) are
recognized as the leading causes of bacterial gastroenteritis, followed by Shigella spp. and
Shiga toxin-encoding Escherichia coli (STEC).(Control and Prevention 2010).Shigatoxigenic
Escherichia coli (STEC) include Escherichia coli serotypes whose genomes
contain one or more Shiga toxin genes. STEC infections in humans can range from mild selflimiting
diarrhea to more severe disease, including hemorrhagic colitis and hemolytic uremic
syndrome (HUS).
Real-time PCR allows for quantification of the target. Real-time PCR perform better
than the standard culture-based assays to detect pathogenic organisms. In summary, work
load and work flow issues may dictate which system is best for different-sized laboratories
and test volumes.PCR assays to perceive the stx1 and stx2 genes are utilized by several
public health laboratories for identification and confirmation of STEC infection. Depending
on the primers used, these assays will distinguish between stx1 and stx2 (Zaki and El-Adrosy
2007). Assays even have been developed that verify the specific O group of an organism,
detect virulence factors such as intimin and enterohemolysin, and can differentiate among the
subtypes of Shiga toxins.
So there was need to analyze soil of to check the presence of Escherichia coli
O157:H7 for avoiding fatal diseases caused by it and there was also monitored soil chemistry
and its relation with bacterial growth specifically Escherichia coli O157:H7 because
Different soil composition and different environmental risk factors promoted presence of
Escherichia coli O157:H7 in soil.
Real Time-PCR technique was opted to detect Escherichia coli O157:H7 in the soil
from distant areas of district Lahore of Punjab, Pakistan. Soil samples from 10 per cent
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villages were collected from this district and handled for genome extraction using
commercially available soil DNA extraction kit. After genome extraction, the samples were
keep running for Real Time-PCR at optimized conditions. The reaction was improved by
variations in standard concentrations of primers, probes, DNA, Taq-polymerase and sequence
of primers.
The dissemination of soil borne Escherichia coli O157:H7 was mapped in mentioned
district of Punjab, Pakistan using geographical co-ordinates recorded by GPS beneficiary.
Relationship of Escherichia coli O157:H7 with environmental factors,soil chemistry and
source of land irrigation (Canal, tubewell and rain or in combination), was resolved. Results of
present project were analyzed through SPSS.
The purpose of the research work was the understanding of occurrence and
distribution of Escherichia coli O157:H7 in district Lahore of Punjab province .It also threw
light on role of soil as a reservoir of Escherichia coli O157:H7, and association of this
infectious agent with various risk factors.
In this study depending upon the statistical analysis data, it was depicted that
Escherichia coli o157 H7 is present in soil although it can’t persist or survive. The prevalence
rate of Escherichia coli O157 h7 is 3.1% in 129 soil samples of Lahore. In case of villages it
is present in 2 villages of of 29.that shows it is 6.8% prevalent in villages.
The presence or absence of pathogen in relation to soil chemistry and seven potential
risk factors was determined through student t distribution (T-test). By observing p value of
variables of positive and negative sites it comes to know that there is no significant
association of these factors to the survival of Escherichia coli O157:H7 in soil.
Remaining all other analytes has not significant association with soil. But it can be
seen Escherichia coli O157 H7 has significant association with organic matters, phosphorus,
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54
copper, cobalt, calcium, sodium, ferrous ion, potassium and sand form of soil ranging from
(0.86-1.97), (9.7-22.5), (24.18-41.12), (0.048-0.51), (0.39-0.96), (0.08-0.16), (41.84-59.14),
(51.02-69.56), (83-86) respectively. Remaining all other analytes has not significant
association with soil.
For further investigations it is necessary that find out those factors which cause
hindrance in survival of Escherichia coli o157 h7 in soil specifically and also search out
those factors which support Escherichia coli O157 h7 persistence in soil.