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Letters in Applied Microbiology
Volume 49 Issue 6, Pages 685 - 688

ORIGINAL ARTICLE
Identification of coliform genera recovered from water using different 
technologies
C.R. Fricker 1,2 and B.J. Eldred 1 
  1 Analytical Services Inc., Allen Brook Lane, Williston, VT, USA 
  2 CRF Consulting, Child's Acre, Church Lane, Reading, UK 
Correspondence to Colin R. Fricker, Dr C Fricker Child's Acre, Church 
Lane, Three Mile Cross, Reading, RG7 1HD, UK. E-mail: colinfricker at aol.com
Copyright Journal compilation © 2009 The Society for Applied Microbiology

KEYWORDS
coliforms • galactosidase • identification • lactose • water

ABSTRACT
Aims: Methods for the detection of coliforms in water have changed 
significantly in recent years with procedures incorporating substrates for 
the detection of β-d-galactosidase becoming more widely used. This study 
was undertaken to determine the range of coliform genera detected with 
methods that rely on lactose fermentation and compare them to those 
recovered using methods based upon β-d-galactosidase.
Methods and Results: Coliform isolates were recovered from sewage-polluted 
water using m-endo, membrane lauryl sulfate broth, tergitol TTC agar, 
Colilert-18®, ChromoCult® and ColiScan® for primary isolation. Organisms 
were grouped according to whether they had been isolated based upon 
lactose fermentation or β-d-galactosidase production.
Conclusions: A wide range of coliform genera were detected using both 
types of methods. There was considerable overlap between the two groups, 
and whilst differences were seen between the genera isolated with the two 
method types, no clear pattern emerged. Substantial numbers of 'new' 
coliforms (e.g. Raoutella spp.) were recovered using both types of 
methods.
Significance and Impact of the Study: The results presented here confirm 
that both methods based on lactose fermentation or detection of 
β-d-galactosidase activity recover a range of coliform organisms. Any 
suggestion that only methods which are based upon fermentation of lactose 
recover organisms of public health or regulatory significance cannot be 
substantiated. Furthermore, the higher recovery of coliform organisms from 
sewage-polluted water using methods utilizing β-d-galactosidase-based 
methods does not appear to be because of the recovery of substantially 
more 'new' coliforms.
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Letters in Applied Microbiology
Volume 49 Issue 6, Pages 784 - 790

ORIGINAL ARTICLE
Persistence of Escherichia coli O157:H7 on the rhizosphere and 
phyllosphere of lettuce
A. Mark Ibekwe 1 , C.M. Grieve 1 , S.K. Papiernik 2 and C.-H. Yang 3 
  1 USDA-ARS, US. Salinity Lab. Riverside, CA, USA 
  2 USDA-ARS, North Central Soil Conservation Research Laboratory, Morris, 
MN, USA 
  3 Department of Biological Sciences, University of Wisconsin-Milwaukee, 
WI, USA 
Correspondence to Abasiofiok Mark Ibekwe, USDA-ARS-U. S. Salinity 
Laboratory, 450 W. Big Springs Rd, Riverside, CA 92507. E-mail: 
Mark.Ibekwe at ars.usda.gov
Copyright Journal compilation © 2009 The Society for Applied Microbiology

KEYWORDS
Escherichia coli O157:H7 • lettuce • persistence • phyllosphere • 
real-time PCR • rhizosphere

ABSTRACT
Aims: The major objective of this study was to determine the effects of 
low levels of Escherichia coli O157:H7 contamination on plant by 
monitoring the survival of the pathogen on the rhizosphere and leaf 
surfaces of lettuce during the growth process.
Methods and Results: Real-time PCR and plate counts were used to quantify 
the survival of E. coli O157:H7 in the rhizosphere and leaf surfaces after 
planting. Real-time PCR assays were designed to amplify the stx1, stx2 and 
the eae genes of E. coli O157:H7. The detection limit for E. coli O157:H7 
quantification by real-time PCR was 2·4 ? 103 CFU g?1 of starting DNA in 
rhizosphere and phyllosphere samples and about 102 CFU g?1 by plate 
count. The time for pathogens to reach detection limits on the leaf 
surface by plate counts was 7 days after planting in comparison with 
21 days in the rhizosphere. However, real-time PCR continued to detect stx
1, stx2 and the eae genes throughout the experimental period.
Conclusion:  Escherichia coli O157:H7 survived throughout the growth 
period as was determined by real-time PCR and by subsequent enrichment and 
immunomagnetic separation of edible part of plants.
Significance and impact of the Study: The potential presence of human 
pathogens in vegetables grown in soils contaminated with E. coli O157:H7 
is a serious problem to our national food supply as the pathogen may 
survive on the leaf surface as they come in contact with contaminated soil 
during germination.

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Letters in Applied Microbiology
Volume 49 Issue 6, Pages 659 - 665

ORIGINAL ARTICLE
Unravelling Escherichia coli dynamics close to the maximum growth 
temperature through heterogeneous modelling
E. Van Derlinden, K. Bernaerts and J.F. Van Impe 
CPMF2– Flemish Cluster Predictive Microbiology in Foods—
http://www.cpmf2.be,
BioTeC – Chemical and Biochemical Process Technology and Control, 
Department of Chemical Engineering, Katholieke Universiteit Leuven, 
Leuven, Belgium
Correspondence to Jan F. Van Impe, BioTeC – Chemical and Biochemical 
Process Technology and Control, Department of Chemical Engineering, 
Katholieke Universiteit Leuven, W. de Croylaan 46, B-3001 Leuven, Belgium. 
E-mail: jan.vanimpe at cit.kuleuven.be
Copyright Journal compilation © 2009 The Society for Applied Microbiology

KEYWORDS
adaptation • Escherichia coli • heterogeneous population • subpopulation • 
temperature

ABSTRACT
Aims: Previous work showed that the exponential phase of Escherichia coli 
K12 MG1655, grown in Brain Heart Infusion broth at temperatures close to 
its maximum growth temperature, is disturbed. Based on plate count data, 
microscopic images and literature, the existence of a heat-resistant 
subpopulation was hypothesized. Here, this hypothesis is mathematically 
explored via a heterogeneous model.
Methods and Results: A heat-sensitive and a heat-resistant subpopulation 
are considered. A large fraction of the population is inactivated, while 
the remaining smaller fraction is able to resist (or adapt to) the 
inimical temperature and grows. A heterogeneous model that encloses a 
growth model (resistant population) and an inactivation model (sensitive 
population) is used to describe the global population dynamics. Most 
experimental data can be predicted when taking parameter uncertainty via 
Monte Carlo simulation into account.
Conclusions: The heterogeneous model accurately describes disturbed growth 
curves at superoptimal temperatures, except for high initial cell 
densities.
Significance and Impact of the Study: This study strengthens the 
hypothesis of the existence of a (small) heat-resistant subpopulation in 
typical inoculum cultures of E. coli K12 MG1655.
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Water Research
Volume 43, Issue 19, November 2009, Pages 4802-4811 


Performance of CHROMagar™ Staph aureus and CHROMagar™ MRSA for detection 
of Staphylococcus aureus in seawater and beach sand – Comparison of 
culture, agglutination, and molecular analyses 
K.D. Goodwina, , and M. Pobudab
aNational Oceanic and Atmospheric Administration (NOAA) Atlantic 
Oceanographic & Meteorological Laboratories (AOML), 4301 Rickenbacker 
Causeway, Miami, FL 33149, USA
bCooperative Institute of Marine and Atmospheric Studies, Rosenstiel 
School of Marine and Atmospheric Science, University of Miami, 4600 
Rickenbacker Causeway, Miami, FL 33149, USA

Received 16 March 2009;  revised 3 June 2009;  accepted 4 June 2009.  
Available online 18 June 2009. 
Abstract
Beach seawater and sand were analyzed for Staphylococcus aureus and 
methicillin resistant S. aureus (MRSA) for samples collected from Avalon, 
and Doheny Beach, CA. Membrane filtration followed by incubation on 
CHROMagar™ Staph aureus (SCA) and CHROMagar™ MRSA (C-MRSA) was used to 
enumerate S. aureus and MRSA, respectively. Media performance was 
evaluated by comparing identification via colony morphology and latex 
agglutination tests to PCR (clfA, 16S, and mecA genes). Due to background 
color and crowding, picking colonies from membrane filters and streaking 
for isolation were sometimes necessary. The specificity of SCA and C-MRSA 
was improved if colony isolates were identified by the presence of a matte 
halo in addition to mauve color; however routine agglutination testing of 
isolates did not appear warranted. Using the appearance of a colony on the 
membrane filter in conjunction with isolate appearance, the positive % 
agreement, the negative % agreement, and the % positive predictive 
accuracy for SCA was 84%, 95%, and 99% respectively, and for C-MRSA it was 
85%, 98%, and 92%, respectively. Sensitivity and specificity of SCA and 
C-MRSA with membrane-filtered beach samples were optimized through 
identification experience, control of filter volume and incubation time, 
and isolation of colonies needing further identification. With 
optimization, SCA and C-MRSA could be used for enumeration of S. aureus 
and MRSA from samples of beach water and sand. For the sites studied here, 
the frequency of detection of S. aureus ranged from 60 to 76% and 53 to 
79% for samples of beach seawater and sand, respectively. The frequency of 
detection of MRSA ranged from 2 to 9% and 0 to 12% for samples of seawater 
and sand, respectively.
Keywords: Staphylococcus aureus; MRSA; Recreational water quality; 
CHROMagar; clfA; mecA
Abbreviations: CHROMagar™ Staph aureus, (SCA); CHROMagar™ MRSA, (C-MRSA)

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Murulee Byappanahalli, Ph. D.
Research Microbiologist
U.S. Geological Survey, Great Lakes Science Center
Lake Michigan Ecological Research Station,
1100 N. Mineral Springs Road
Porter, Indiana 46304
Phone: (219) 926-8336 ext. 421
Fax:      (219) 929-5792
E-mail: byappan at usgs.gov

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