A note on antibiotic-resistant Escherichia coli in adult man, raw sewage and sewage-polluted River Tigris in Mosul, Nineva

A total of 600 isolates of Escherichia coli were isolated, over a 9 month period during 1984, from healthy human adults, raw sewage and the sewage-polluted River Tigris in Nineva. Over 90% of these organisms were E. coli type 1, but only 8.3% could be serogrouped as enteropathogenic E. coli . Resistance of these organisms to 11 antimicrobial drugs was assessed. Over 40% were antibiotic-resistant and of these 77.1% were resistant to more than one antibiotic. The minimal inhibitory concentration of ampicillin for 193 selected strains from the various sources was determined and ranged from <0.625- > 160 μg/ml. The high incidence of antibiotic-resistant E. coli in this locality and the possible implications to human health are discussed.     

A note on antibiotic resistance in the bacterial flora of raw sewage and sewage-polluted River Tigris in Mosul, Iraq

Polluted water samples collected from the River Tigris in the vicinity of a raw sewage outfall were examined for the incidence of antibiotic resistance among coli-form bacteria on three occasions during 1983. Eighty percent or more of the coli-form bacteria were resistant to one or more antibiotics. At the same time, raw sewage samples were examined for the incidence of antibiotic-resistant bacteria, and Escherchia coli, Pseudomonas spp. and Staphylococcus spp. were selected for sensitivity testing. Collectively, more than 90% of the 480 strains of the three organisms were resistant to one or more antibiotics. The minimal inhibitory concentration (MIC) of ampicillin for twenty-nine strains including coliforms, E. coli, Klebsiella sp., Serratia sp., Ps. aeruginosa, Pseudomonas sp., Micrococcus sp., Staph. aureus, Streptococcus faecalis and Bacillus sp. from raw sewage and polluted River Tigris water was determined and that for Ps. aeruginosa was 250 μg/ml. The high incidence of antibiotic-resistant bacteria in natural waters could be related to the widespread use of antibiotics in this locality.     

A note on antibiotic resistance in the bacterial flora of raw sewage and sewage-polluted River Tigris in Mosul, Iraq

Polluted water samples collected from the River Tigris in the vicinity of a raw sewage outfall were examined for the incidence of antibiotic resistance among coliform bacteria on three occasions during 1983. Eighty percent or more of the coliform bacteria were resistant to one or more antibiotics. At the same time, raw sewage samples were examined for the incidence of antibiotic-resistant bacteria, and Escherichia coli, Pseudomonas spp. and Staphylococcus spp. were selected for sensitivity testing. Collectively, more than 90% of the 480 strains of the three organisms were resistant to one or more antibiotics. The minimal inhibitory concentration (MIC) of ampicillin for twenty-nine strains including coliforms, E. coli, Klebsiella sp., Serratia sp., Ps. aeruginosa, Pseudomonas sp., Micrococcus sp., Staph. aureus, Streptococcus faecalis and Bacillus sp. from raw sewage and polluted River Tigris water was determined and that for Ps. aeruginosa was 250 micrograms/ml. The high incidence of antibiotic-resistant bacteria in natural waters could be related to the widespread use of antibiotics in this locality.     

Occurrence, virulence characteristics and antimicrobial resistance of Escherichia coli O157 in slaughtered cattle and diarrhoeic calves in West Bengal, India

AIMS: (i) To study the occurrence of Escherichia coli serotype O157 in cattle stool in West Bengal, India, and (ii) the virulence properties and antimicrobial resistance of the E. coli isolates. METHODS AND RESULTS: Following enrichment in modified EC broth and plating onto HiCrome MS.O157 agar, a total of 14 strains of E. coli serotype O157 was isolated from faecal samples from two (2.04%) slaughtered cattle and six (7.59%) diarrhoeic calves. By multiplex PCR, Shiga toxin genes were detected in all the isolates. The enterohaemolysin phenotype was found in all, but one strain. Among 14 strains, ten were resistant to at least one of the antimicrobial agents tested. Multiple antibiotic resistance was frequent. CONCLUSIONS: The study showed that occurrence of Shiga toxin-producing and multiple antibiotic-resistant E. coli O157 among cattle population in this region of India is significant. SIGNIFICANCE AND IMPACT OF THE STUDY: Considering routine human contacts with cattle, a large human population in this region may be at risk for exposure to Shiga toxin-producing E. coli O157.     

Incidence of antibiotic-resistant Escherichia coli in milk produced in the west of Scotland

Antibiotic-resistant Esch. coli were found in 10.6% of milk samples collected from 998 farms in the west of Scotland. The incidence of both Esch. coli and antibiotic-resistant Esch. coli in milk was higher when the cattle were housed day and night than when they were outdoors. Of the 1125 Esch. coli isolates tested 22.2% were antibiotic resistant and of these 42.4% were resistant to more than one antibiotic. Escherichia coli carrying up to six resistance determinants were isolated. The possible implications to animal and human health are discussed.     

Incidence of antibiotic-resistant Escherichia coli in milk produced in the west of Scotland

Antibiotic-resistant Esch. coli were found in 10.6% of milk samples collected from 998 farms in the west of Scotland. The incidence of both Esch. coli and antibiotic-resistant Esch. coli in milk was higher when the cattle were housed day and night than when they were outdoors. Of the 1125 Esch. coli isolates tested 22.2% were antibiotic resistant and of these 42.4% were resistant to more than one antibiotic. Escherichia coli carrying up to six resistance determinants were isolated. The possible implications to animal and human health are discussed.     

Geographical variation in ribotype profiles of Escherichia coli isolates from humans,swine, poultry,beef, and dairy cattle in Florida

Waters impacted by fecal pollution can exact high risks to human health and can result in financial losses due to closures of water systems used for recreation and for harvesting seafood. Identifying the sources of fecal pollution in water is paramount in assessing the potential human health risks involved as well as in assessing necessary remedial action. Recently, various researchers have used the ribotyping method to identify sources of bacterial indicators (Escherichia coli and enterococci) in environmental waters. While these studies have identified genotypic differences between human- and animal-derived indicators that are capable of differentiating organisms isolated from humans and various animal hosts, most have focused on organisms collected from a confined geographic area and have not addressed the question of whether these ribotype profiles are watershed specific or if they can be applied universally to organisms from other geographic locations. In this study, E. coli isolates were obtained from humans, beef cattle, dairy cattle, swine, and poultry from locations in northern, central, and southern Florida and were subjected to ribotyping analysis. The intent was to determine (i) if ribotype profiles are capable of discriminating the source of E. coli at the host species level and (ii) if the resulting fingerprints are uniform over an extended geographic area or if they can be applied only to a specific watershed. Our research indicated that, using a single restriction enzyme (HindIII), the ribotyping procedure is not capable of differentiating E. coli isolates from the different animal species sampled in this study. Results indicate, however, that this procedure can still be used effectively to differentiate E. coli as being either human or animal derived when applied to organisms isolated from a large geographic region.     

Escherichia coli in settled-dust and air samples collected in residential environments in Mexico City.

Escherichia coli, an important indicator of the presence of fecal material, was isolated from indoor and outdoor environments in Mexico City. The heterogeneity of E. coli was represented by 89 serotypes, most of them coming from settled-dust indoor samples; 21% of them presented antibiotic multiresistance. The numbers of plasmids were higher among the antibiotic-resistant strains. The results of this study suggest that intestinal infections produced by environmental strains could be of more epidemiological impact than previously thought.     

Virulence, resistance genes, and transformation amongst environmental isolates of Escherichia coli and Acinetobacter spp

The association of verotoxic E. coli and Acinetobacter spp. with various antibiotic-resistant, diarrhogenic, and nosocomial infections has been a cause for concern worldwide. E. coli and A. haemolyticus isolated on a number of selective media were screened for virulence factors, antibiotic resistance, and transformation of resistance genes. Out of 69 E. coli isolates obtained, 25 (35.23%), 14 (20.30%), and 28 (40.58%) were positive for Vtx1&2, Vtx1, and Vtx2, respectively, 49 (71.015%) for extendedspectrum beta-lactamases (ESBLs), 34 (49.28%) for serum resistance, 57 (82.61%) for cell surface hydrophobicity, 48 (69.57%) for gelatinase production, and 37 (53.62%) for hemolysin production. For the 14 A. haemolyticus isolates, only 2 (14.29%) in each case from all the samples investigated were positive for Vtx1, Vtx2 and Vtx1&2 respectively, 8 (57.14%) for ESBLs, 7 (50.00%) for serum resistance, 11 (78.57%) for cell surface hydrophobicity, 4 (28.57%) for gelatinase production, and 8 (57.14%) for hemolysin production. Although transformation occurred among the E. coli and Acinetobacter isolates (transformation frequency: 13.3 × 10(-7) -53.4(-7)), there was poor curing of the plasmid genes, a confirmation of the presence of stable antibiotic-resistant genes (DNA concentration between 42.7 and 123.8 microgram) and intragenetic transfer of multidrugresistant genes among the isolates. The isolates were potentially virulent and contained potentially transferable antibiotic resistance genes. Detection of virulence factors, antibiotic resistance genes, and transformation among these isolates is a very significant outcome that will influence approaches to proactive preventive and control measures and future investigations. However, continued surveillance for drug resistance among these bacteria and further investigation of the mechanism of action of their virulence factors are a necessity.     

Distribution and characterization of integrons in Escherichia coli strains of animal and human origin

One hundred and twenty clinical and commensal Escherichia coli strains isolated in Switzerland from humans and from companion and farm animals were analysed for the prevalence of integrons of classes 1, 2, and 3 and for the characterization of their gene cassettes. The relationships between integron carriage and host category, and between integron carriage and phylogenetic E. coli lineage were also analysed. Integrons were detected in 48 (40%) of the isolates and were thus widely disseminated in the human and animal E. coli strains considered. Moreover, the association between integron carriage and certain animal categories (farm animals) suggests that animals that are raised for economic purposes might be exposed to a major antibiotic pressure. Finally, our data confirm that E. coli commensal strains represent a significant source of antibiotic-resistant determinants.     

Optimization of a reusable hollow-fiber ultrafilter for simultaneous concentration of enteric bacteria,protozoa, and viruses from water

The detection and identification of pathogens from water samples remain challenging due to variations in recovery rates and the cost of procedures. Ultrafiltration offers the possibility to concentrate viral, bacterial, and protozoan organisms in a single process by using size-exclusion-based filtration. In this study, two hollow-fiber ultrafilters with 50,000-molecular-weight cutoffs were evaluated to concentrate microorganisms from 2- and 10-liter water samples. When known quantities (10(5) to 10(6) CFU/liter) of two species of enteric bacteria were introduced and concentrated from 2 liters of sterile water, the addition of 0.1% Tween 80 increased Escherichia coli strain K-12 recoveries from 70 to 84% and Salmonella enterica serovar Enteritidis recoveries from 36 to 72%. An E. coli antibiotic-resistant strain, XL1-Blue, was recovered at a level (87%) similar to that for strain K-12 (96%) from 10 liters of sterile water. When E. coli XL1-Blue was introduced into 10 liters of nonsterile Rio Grande water with higher turbidity levels (23 to 29 nephelometric turbidity units) at two inoculum levels (9 x 10(5) and 2.4 x 10(3) per liter), the recovery efficiencies were 89 and 92%, respectively. The simultaneous addition of E. coli XL1-Blue (9 x 10(5) CFU/liter), Cryptosporidium parvum oocysts (10 oocysts/liter), phage T1 (10(5) PFU/liter), and phage PP7 (10(5) PFU/liter) to 10 liters of Rio Grande surface water resulted in mean recoveries of 96, 54, 59, and 46%, respectively. Using a variety of surface waters from around the United States, we obtained recovery efficiencies for bacteria and viruses that were similar to those observed with the Rio Grande samples, but recovery of Cryptosporidium oocysts was decreased, averaging 32% (the site of collection of these samples had previously been identified as problematic for oocyst recovery). Results indicate that the use of ultrafiltration for simultaneous recovery of bacterial, viral, and protozoan pathogens from variable surface waters is ready for field deployment.     

The control of experimental Escherichia coli diarrhoea in calves by means of bacteriophages

Seven phages highly active in vitro and in vivo against one or other of seven bovine enteropathogenic strains of Escherichia coli belonging to six different serotypes were isolated from sewage. Severe experimentally induced E. coli diarrhoea in calves could be cured by a single dose of 10(5) phage organisms. It could be prevented by doses as low as 10(2), by spraying the litter in the calf rooms with aqueous phage suspensions or simply by keeping the calves in uncleaned rooms previously occupied by calves whose E. coli infections had been treated with phage. Microbiological examinations of calves used in these experiments revealed that the phage organisms multiplied rapidly and profusely after gaining entry to the E. coli-infected small intestine, quickly reducing the E. coli to numbers that were virtually harmless. The only phage-resistant E. coli that emerged in the studies on calves infected with one or other of the seven E. coli strains were K-. These organisms were much less virulent than the K+ organisms from which they were derived and did not present a serious problem in calves given adequate amounts of colostrum. Infections produced by oral inoculation of a mixture of six strains of the E. coli could be controlled by administration of a pool of the six phages that were active against them but, in general, the control was less complete than that observed in the single-strain infections. K+ phage-resistant bacteria emerged in some of the calves used in these mixed infections and they were as virulent as their parent organisms; evidence from in vitro studies suggested that they might have arisen by genetic transfer between organisms of the different infecting strains. Infections produced by these K+ mutants and their parents could be controlled by the use of mutant phages derived from phages that were active on their parents. During the experiments with mixed E. coli infection, an extraneous phage active against one of the six E. coli strains suddenly appeared in calves kept in the same rooms. Microbiological examinations revealed that this phage was effectively controlling the multiplication of organisms of that particular strain of E. coli in the small intestines of the calves.     

Molecular characterization of antibiotic resistant Escherichia coli strains isolated from tap and spring waters in a coastal region in Turkey

A hundred and seventeen antibiotic-resistant Escherichia coli strains were isolated from public tap and spring waters which were polluted by fecal coliforms. There were no significant differences between two water sources as to the coliform pollution level (p> 0.05). All E. coli isolates were detected to be resistant to one or more antibiotics tested. Nearly 42% of the isolates showed multiresistant phenotype. Three (2.5%) of these isolates contained class 1 integron. Sequencing analysis of variable regions of the class 1 integrons showed two gene cassette arrays, dfr1-aadA1 and dhfrA17-aadA5. Resistance to ampicillin, tetracycline or trimethoprim-sulfamethoxazole was transferable according to the results of conjugation experiments. The rate of tetracycline resistance was 15%. tet(A)-mediated tetracycline resistance was widespread among tetracycline-resistant E. coli isolates. Genotyping by BOX-polymerase chain reaction (BOX-PCR) showed that some of the strains were epidemiologically related. This is the first report on the prevalence and characterization of class 1 integron-containing E. coli isolates of environmental origin in Turkey.     

Proteomic analysis of nalidixic acid resistance in Escherichia coli: identification and functional characterization of OM proteins

The worldwide emergence of antibiotic-resistant bacteria poses a serious threat to human health. To understand the mechanisms of the resistance is extremely important to the control of these bacteria. In the current study, proteomic methodologies were utilized to characterize OM proteome of Escherichia coli with nalidixic acid (NA) resistance. The OM proteins TolC, OmpT, OmpC and OmpW were found to be up-regulated, and FadL was down-regulated in the NA-resistant E. coli strains. The changes at the level of protein expression were validated using Western blotting. Furthermore, the possible roles these altered proteins played in regulation of NA resistance were investigated using genetically modified strains with the deletion of these genes. The results obtained from functional characterization of these genetically modified strains suggest that TolC and OmpC may play more important roles in the control of NA resistance than other OM proteins identified. To gain better understanding of the mechanisms of NA resistance, we also characterized the role of the two-component system EnvZ/OmpR which is responsible for the regulation of OmpC and OmpF expression in response to NA resistance using their genetically modified strains. Our results suggest that OmpF and the EnvZ/OmpR are also important participants of the pathways regulating the NA resistance of E. coli.     

Antibiotic resistance and resistance mechanisms in Campylobacter jejuni and Campylobacter coli

Campylobacter jejuni and Campylobacter coli are recognized as the most common causative agents of bacterial gastroenteritis in the world and infections with these organisms occur more frequently than do infections due to Salmonella species, Shigella species, or Escherichia coli 0157:H7. The incidence of human Campylobacter infections has increased markedly in both developed and developing countries worldwide and, more significantly, so has the rapid emergence of antibiotic-resistant Campylobacter strains, with evidence suggesting that the use of antibiotics, in particular the fluoroquinolones, as growth promoters in food animals and the veterinary industry is accelerating this trend. In this minireview, the patterns of emerging resistance to the antimicrobial agents useful in treatment of the disease are presented and the mechanisms of resistance to these drugs in Campylobacter spp are discussed.     

Factors influencing the survival and multiplication of bacteriophages in calves and in their environment

Seven phages were fairly susceptible in vitro to the lethal effect of acidified whey, more so than the enteropathogenic Escherichia coli strains on which they were active. The low acidity that prevailed in the abomasum contents of calves shortly after a milk feed had little harmful effect on orally administered organisms of these phages; they flooded into the small intestine. The high acidity that prevailed later was lethal to orally administered phage organisms; few entered the small intestine. The lethal effect could be counteracted by giving CaCO3 in the feed. Low concentrations of phage-neutralizing antibodies were found in some serum samples from human beings, cattle and pigs. Antibodies to one of the seven phages were common in the human samples and antibodies to another, phage B44/1, were common in the cattle and pig samples and in bovine colostrum. Phage B44/1 antibodies in a sample of colostral whey were destroyed at pH 3.25 or less. Giving colostrum containing phage B44/1 antibodies with CaCO3 to a calf greatly reduced the numbers of orally administered phage B44/1 organisms in its alimentary tract. Antibodies to another phage were induced in the serum of a calf suffering from E. coli diarrhoea by treating it with that phage. The phages were as susceptible as the E. coli strains to the lethal action of formaldehyde and sodium hypochlorite. In contrast to the E. coli strains, they were almost completely resistant to phenol and chloroxylenol. The in vitro virulence of 21 phages varied according to the temperature at which tests were performed.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of immunomagnetic separation and culture, Reveal and VIP for the detection of E. coli O157 in enrichment cultures of naturally-contaminated raw beef, lamb and mixed meat products

AIMS: The aims of this study were (i) to evaluate the specificity and sensitivity of three previously described PCR assays for the detection of E. coli O157 and, (ii) to compare PCR, culture, and two visual immunoassays (VIAs), BioSign and Path-Stik, for detecting E. coli O157 after enrichment culture and immunomagnetic separation (IMS) performed on various naturally contaminated raw beef, lamb and mixed meat products. METHODS AND RESULTS: Twelve sorbitol non fermenting (SNF) verocytotoxin-producing (VT+) E. coli O157, 6 SNF VT- E. coli O157, 4 sorbitol fermenting (SF) VT+ E. coli O157, 3 SF VT- E. coli O157, 23 E. coli belonging to 17 other serogroups and 12 organisms of other species were used to check the specificity of PCR reactions. Only one primer pair generated amplimers only with E. coli O157 and was used for all subsequent work. After enrichment culture and on inoculated minced beef samples, PCR was as sensitive as culture for detecting 9 of the 12 strains of E. coli O157, but up to 4 log10 more sensitive than culture for detecting three strains. Of the 120 samples of naturally contaminated meat products examined, 80 (67%) were positive by PCR, 70 (58%) were positive by BioSign, 69 (58%) were positive by culture and 67 (56%) were positive by Path-Stik. Eleven samples were positive by PCR and both VIAs, but negative by culture because culture plates were heavily overgrown with SF organisms making detection of any E. coli O157 present impossible. CONCLUSIONS: PCR and both VIAs compared well with culture of beads to CT-SMAC for detecting E. coli O157 after enrichment culture and IMS. PCR appeared to be the most sensitive method, but needed specialised equipment and was also the most expensive, laborious and technically demanding technique. Although lacking the sensitivity of PCR, the VIAs were of comparable sensitivity to culture and were extremely quick and easy to perform giving a result in less than 15 minutes. SIGNIFICANCE AND IMPACT OF THE STUDY: Culture techniques may fail to detect E. coli O157 retrieved by IMS due to overgrowth with other organisms.     

Membrane filter method for enumerating Escherichia coli.

A membrane filter procedure for enumerating Escherichia coli was developed and evaluated. The method quantifies E. coli within 24 h without requiring subculture and identification of isolates. It incorporates a primary selective-differential medium for gram-negative, lactose-fermenting bacteria; resuscitation of weakened organisms by incubation for 2 h at 35 degrees C before incubation at 44.5 degrees C for 18 to 22 h; and an in situ urease test to differentiate E. coli from other thermotolerant, lactose-positive organisms. The recovery of E. coli from marine, estuarine, and freshwater samples exceeded 90%. Of the presumptively positive colonies, 91% were verified as E. coli. Less than 1% of all of the verified E. coli colonies failed to react typically.     

Prevalence and molecular characterization of Escherichia coli O157:H7 on Irish lamb carcasses, fleece and in faeces samples

AIMS: To determine the prevalence, seasonal variation and virulence characteristics of Escherichia coli O157:H7 in lambs presented for slaughter in Ireland. METHODS AND RESULTS: Over a 13-month period, pre- and postchill carcass swabs, faeces and fleece samples from 1600 lambs were examined for the presence of E. coli O157:H7. Escherichia coli O157:H7 was isolated from 5.75% (23/400) of fleece samples, 1.5% (6/400) of pre- and 1% (4/400) of postchill carcass swabs but was not isolated in faeces (0/400). The present study detected no evidence of seasonal variation. Polymerase chain reaction analysis showed that both the vt1 and vt2 genes associated with clinical illness were carried by five of the E. coli O157:H7 isolates, while 24 of the remaining isolates carried the vt2 gene only. Phage typing detected four different subtypes: PT 32 (48.48%), PT 8 (12.12%), PT 31 (12.12%) and PT 21/28 (12.12%). CONCLUSIONS: Escherichia coli O157:H7 is present in lambs at slaughter in Irish abattoirs and the virulence profiles of these isolates reveals that they are potentially harmful to humans. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study provides crucial information indicating that sheep may be a significant contributing source to human E. coli O157:H7 infection.