Marine biofilms on submerged surfaces are a reservoir for Escherichia coli and Vibrio cholerae

The enteric bacterium and potential human pathogen, Escherichia coli, is known to persist in tropical soils and coastal waters. Vibrio cholerae causes the disease cholera and inhabits marine environments including microbial films on submerged surfaces. The abundances of E. coli and V. cholerae were quantified in biofilm and water-column samples from three harbors in Honolulu, Hawai‘i, which differ in their local and international ship traffic. E. coli and, in some cases V. cholerae, occurred in relatively high abundances in marine biofilms formed on abiotic surfaces, including the exterior hulls of ships. The community fingerprints of the biofilms and the water harboring these pathogens were further analyzed. The community compositions of biofilms from different locations were more similar to each other than to water-column communities from the same locations. These results suggest that biofilms are an overlooked reservoir and a source of dissemination for E. coli and V. cholerae.     

Uropathogenic Escherichia coli (UPEC) strains may carry virulence properties of diarrhoeagenic E. coli

To analyze whether Escherichia coli strains that cause urinary tract infections (UPEC) share virulence characteristics with the diarrheagenic E. coli (DEC) pathotypes and to recognize their genetic diversity, 225 UPEC strains were examined for the presence of various properties of DEC and UPEC (type of interaction with HeLa cells, serogroups and presence of 30 virulence genes). No correlation between adherence patterns and serogroups was observed. Forty-five serogroups were found, but 64% of the strains belonged to one of the 12 serogroups (O1, O2, O4, O6, O7, O14, O15, O18, O21, O25, O75, and O175) and carried UPEC virulence genes (pap, hly, aer, sfa, cnf). The DEC genes found were: aap, aatA, aggC, agg3C, aggR, astA, eae, ehly, iha, irp2, lpfA(O113), pet, pic, pilS, and shf. Sixteen strains presented aggregative adherence and/or the aatA sequence, which are characteristics of enteroaggregative E. coli (EAEC), one of the DEC pathotypes. In summary, certain UPEC strains may carry DEC virulence properties, mostly associated to the EAEC pathotype. This finding raises the possibility that at least some faecal EAEC strains might represent potential uropathogens. Alternatively, certain UPEC strains may have acquired EAEC properties, becoming a potential cause of diarrhoea.     

Yersinia HPI in septicemic Escherichia coli strains isolated from diverse hosts

High pathogenicity islands (HPIs), first identified in various Yersinia species, encode an iron uptake system. We have studied the occurrence of HPIs in septicemic strains of Escherichia coli isolated from a variety of hosts. The results presented in this communication indicate that most septicemic strains tested contained HPI sequences even though they already have the aerobactin encoding genes. We have also observed two types of HPI deletions, suggesting genetic instability of this element. Notable exceptions are several strains isolated from septicemia in sheep that lacked both iron acquisition systems.     

Effect of growth rate on the penicillin-binding proteins of Escherichia coli

Abstract In an Escherichia coli strain, the levels of penicillin-binding proteins (PBPs) 1A plus 1B, both peptidoglycan transglycosylase/transpeptidases, were found to be relatively independent of the imposed growth ratw in chemostat cultures under different nutrient limitation conditions. A considerable increase in levels of PBP 6 was observed as the growth rate was reduced, whilst, in contrast, a decrease was observed in levels of the other PBPs.     

Polyhydroxyalkanoate production in recombinant Escherichia coli

Abstract The bacterial species Escherichia coli has proven to be a powerful tool in the molecular analysis of polyhydroxyalkanoate (PHA) biosynthesis. In addition, E. coli holds promise as a source for economical PHA production. Using this microorganism, clones have been developed in our laboratory which direct the synthesis of poly-β-hydroxybutyrate (PHB) to levels as high as 95% of the cell dry weight. These clones have been further enhanced by the addition of a genetically mediated lysis system that allows the PHB granules to be released gently and efficiently. This paper describes these developments, as well as the use of an E. coli strain to produce the copolymer poly-(3-hydroxybutyrate- co -3-hydroxyvalerate (PHB- co -3-).     

Cloning of genes encoding coli-surface (CS) antigens in enterotoxigenic Escherichia coli

Abstract Sequences encoding the CS6 antigen of colonisation factor antigen (CFA)IV were cloned on a 3kb Cla I fragment. The recombinant plasmid pDEP5 coded for surface expression of CS6 measured by ELISA and production of CS6 polypeptides was detected in E. coli minicells. The genes for the CS1, CS2 and CS3 components of colonisation factor antigen CFA/II were cloned together on a length of DNA corresponding to about 17kb. CS3 was always expressed but production of either CS1 or CS2 depended on the serotype and biotype of the host strain. Separate subclones were obtained that expressed CS3 or CS1 and CS2.     

Detection of urovirulence factors in Escherichia coli by multiplex polymerase chain reaction

Abstract Primers to amplify the genes encoding the virulence factors of uropathogenic Escherichia coli , such as pilus associated with pyelonephritis ( pap ), haemolysin ( hly ), aerobactin ( aer ) and cytotoxic necrotizing factor 1 ( cnf 1) genes, were designed. The above primers along with previously reported primers for S fimbriae ( sfa ) and afimbrial adhesin I ( afaI ) genes were combined to develop a multiplex polymerase chain reaction (PCR) for detection of the respective virulence factors and for the identification of uropathogenic E. coli . The multiplex PCR to detect pap, sfa, afa I, hly, aer and cnf 1 genes was highly specific and the sensitivity was found to be about 5 × 10³ colony forming units of E. coli per ml. A total of 194 E. coli strains isolated from patients with simple acute cystitis were examined by the multiplex PCR and the results were in complete agreement with that obtained by DNA colony hybridization test. The multiplex PCR developed was, therefore, concluded to be a useful, sensitive and rapid assay system to identify uropathogenic E. coli .     

Impact of microbial diversity on rapid detection of enterohemorrhagic Escherichia coli in surface waters

Enterohemorrhagic Escherichia coli (EHEC) are a physiologically, immunologically and genetically diverse collection of strains that pose a serious water-borne threat to human health. Consequently, immunological and PCR assays have been developed for the rapid, sensitive detection of presumptive EHEC. However, the ability of these assays to consistently detect presumptive EHEC while excluding closely related non-EHEC strains has not been documented. We conducted a 30-month monitoring study of a major metropolitan watershed. Surface water samples were analyzed using an immunological assay for E. coli O157 (the predominant strain worldwide) and a multiplex PCR assay for the virulence genes stx(1), stx(2) and eae. The mean frequency of water samples positive for the presence of E. coli O157, stx(1) or stx(2) genes, or the eae gene was 50%, 26% and 96%, respectively. Quantitative analysis of selected enriched water samples indicated that even in samples positive for E. coli O157 cells, stx(1)/stx(2) genes, and the eae gene, the concentrations were rarely comparable. Seventeen E. coli O157 strains were isolated, however, none were EHEC. These data indicate the presence of multiple strains similar to EHEC but less pathogenic. These findings have important ramifications for the rapid detection of presumptive EHEC; namely, that current immunological or PCR assays cannot reliably identify water-borne EHEC strains.     

Shiga toxin-producing Escherichia coli and enteropathogenic Escherichia coli in healthy goats in India: occurrence and virulence properties

AIMS: To describe the occurrence and virulence gene pattern of shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) in healthy goats of Jammu and Kashmir, India. METHODS AND RESULTS: A total of 220 E. coli strains belonging to 60 different 'O' serogroups was isolated from 206 local (nonmigratory) and 69 migratory goats. All the 220 strains were screened for the presence of stx(1), stx(2), eaeA and hlyA genes. Twenty-eight E. coli (75.6%) strains from local and nine (24.3%) strains from migratory goats belonging to 18 different serogroups showed at least presence of one virulence gene studied. Twenty-eight strains (16.47%) (belonging to 13 different serogroups) from local goats carried stx(1) gene alone or in combination with stx(2) gene, while as only one strain (2%) from migratory goats possessed stx(2) gene alone. Interestingly in the present study none of the STEC strains carried eaeA gene. Similarly, none of the strains from local goats possessed eaeA and none of the migratory goats possessed stx(1) gene. Eight strains (16%) (belonging to four different serogroups) from migratory goats carried eaeA gene. Twenty-five (14.7%) and seven (14%) strains from local and migratory goats harboured hlyA gene respectively. CONCLUSIONS: Healthy goats of Jammu and Kashmir state serve as a reservoir of STEC and EPEC. Further studies in this direction are needed to work out whether or not they are transmitted to humans in this part of world. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first report of isolation of STEC and EPEC strains from healthy goats in Jammu and Kashmir State of India, which could be a source of infection to humans.     

Purification and characterization of heat-labile enterotoxin isolated from chicken enterotoxigenic Escherichia coli

Abstract The heat-labile enterotoxin (LTc) isolated from chicken enterotoxigenic Escherichia coli was purified to homogeneity and its molecular and antigenic properties were compared with those of purified LTs from porcine and human enterotoxigenic Escherichia coli (LTp, LTh). The A subunit of LTc was identical to that of LTp and the B subunit of LTc was identical to that of LTh but not that of LTp, in mobility on SDS-polyacrylamide gel electrophoresis. Ouchterlony tests demonstrated that LTc is antigenically identical to LTh but not with LTp. The p I point and amino acid composition of LTc were also compared and the results suggest that chicken enterotoxigenic E. coli produced an LT similar to LTh.     

Atomic Force Microscopic Observation of Escherichia coli Ribosomes in Solution

Ribosomes of Escherichia coli were visualized in buffer solution by atomic force microscopy (AFM). A series of time-dependent AFM images showed that ribosomes spontaneously adsorb on mica. Although ribosomes observed in air are forced to flatten on the surface, the height of ribosomal particles obtained under a physiological buffer solution is 21.8±0.5 nm, which is consistent with the ideal diameter. We succeeded in observing single ribosomes in a near-native condition.