Enterohemorrhagic Escherichia coli with particular attention to the German outbreak strain O104:H4

This review deals with the epidemiology and ecology of enterohemorrhagic Escherichia coli (EHEC), a subset of the verocytotoxigenic Escherichia coli (VTEC), and subsequently discusses its public health concern. Attention is also given to the outbreak strain O104:H4, which has been isolated as causative agent of the second largest outbreak of the hemolytic uremic syndrome worldwide, which started in Germany in May 2011. This outbreak strain is not an EHEC as such but possesses an unusual combination of EHEC and enteroaggregative E. coli (EAggEC) virulence properties

Bacterial contamination of table eggs and the influence of housing systems

With the introduction of alternative housing systems for laying hens in the EU, recent research has focussed on the bacterial contamination of table eggs, e.g. eggshell and egg content contamination. Contamination of eggshells with aerobic bacteria is generally higher for nest eggs from non-cage systems compared to nest eggs from furnished cages or eggs from conventional cages. Studies indicate limited or no systematic differences in eggshell contamination with aerobic bacteria between eggs laid in the nest boxes of furnished cages and eggs laid in conventional cages. The major differences found in experimental studies between cage- and non-cage systems are less pronounced under commercial conditions. The effect of housing system on eggshell contamination with specific groups of bacteria is variable. Limited information is available on the influence of housing system on egg content contamination. Recent research does not indicate large differences in egg content contamination between eggs from cage- and non-cage systems (ignoring outside nest and floor eggs). The microflora of the eggshell is dominated by Gram-positive bacteria, whereas Gram-negative bacteria are best equipped to overcome the antimicrobial defences of the egg content. Much of the research on eggshell and egg content contamination focuses on Salmonella, since infection with Salmonella enteritidis, resulting from the consumption of contaminated eggs or egg products, is still a major health problem. Observed Salmonella prevalence on the eggshell and in the egg content vary, depending on the fact whether investigations were based on randomly sampled table eggs or on eggs from naturally infected hens. The limited information available on other pathogens shows that they are exclusively isolated from the eggshell and not from the internal contents

A 10-day vacancy period after cleaning and disinfection has no effect on the bacterial load in pig nursery units

Background: Biosecurity measures such as cleaning, disinfection and a vacancy period between production cycles on pig farms are essential to prevent disease outbreaks. No studies have tested the effect of a longer vacancy period on bacterial load in nursery units. Methods: The present study evaluated the effect of a 10-day vacancy period in pig nursery units on total aerobic flora, Enterococcus spp., Escherichia coli, faecal coliforms and methicillin resistant Staphylococcus aureus (MRSA). Three vacancy periods of 10 days were monitored, each time applied in 3 units. The microbiological load was measured before disinfection and at 1, 4, 7 and 10 days after disinfection. Results: No significant decrease or increase in E. coli, faecal coliforms, MRSA and Enterococcus spp. was noticed. Total aerobic flora counts were the lowest on day 4 after disinfection (i.e. 4.07 log CFU/625 cm(2)) (P < 0.05), but the difference with other sampling moments was limited (i.e. 0.6 log CFU/625 cm(2)) and therefore negligible. Furthermore, this observation on day 4 was not confirmed for the other microbiological parameters. After disinfection, drinking nipples were still mostly contaminated with total aerobic flora (i.e. 5.32 log CFU/625 cm(2)) and Enterococcus spp. (i.e. 95 % of the samples were positive) (P < 0.01); the feeding troughs were the cleanest location (total aerobic flora: 3.53 log CFU/625 cm(2) and Enterococcus spp.: 50 % positive samples) (P < 0.01). Conclusions: This study indicates that prolonging the vacancy period in nursery units to 10 days after disinfection with no extra biosecurity measures has no impact on the environmental load of total aerobic flora, E. coli, faecal coliforms, MRSA and Enterococcus spp.

Exposure of ciprofloxacin-resistant Escherichia coli broiler isolates to subinhibitory concentrations of a quaternary ammonium compound does not increase antibiotic resistance gene transfer

Resistance to antibiotics threatens to become a worldwide health problem. An important attributing phenomenon in this context is that pathogens can acquire antibiotic resistance genes through conjugative transfer of plasmids. To prevent bacterial infections in agricultural settings, the use of veterinary hygiene products, such as disinfectants, has gained popularity and questions have been raised about their contribution to such spreading of antibiotic resistance. Therefore, this study investigated the effect of subinhibitory concentrations of benzalkoniumchloride (BKC), a quaternary ammonium compound (QAC), on the conjugative transfer of antibiotic resistance genes. Five Escherichia coli field strains originating from broiler chickens and with known transferable plasmid-mediated ciprofloxacin resistance were exposed to subinhibitory BKC concentrations: 1/3, 1/10 and 1/30 of the minimum bactericidal concentration. Antibiotic resistance transfer was assessed by liquid mating for 4 h at 25 degrees C using E. coli K12 MG1655 as recipient strain. The transfer ratio was calculated as the number of transconjugants divided by the number of recipients. Without exposure to BKC, the strains showed a ciprofloxacin resistance transfer ratio ranging from 10(-4) to 10(-7). No significant effect of exposure to subinhibitory concentrations of BKC was observed on this transfer ratio

Salmonella prevalence and persistence in industrialized poultry slaughterhouses

Salmonella contamination sources and transmission routes were studied in 5 Belgian poultry slaughterhouses. Samples from the slaughter and cutting line after cleaning and disinfection were collected, as well as neck skin samples and thighs during slaughter of the first flock. In total, 680 swab and water samples were taken from the slaughter line before slaughter. In all slaughterhouses, Salmonella was notwithstanding cleaning and disinfection still isolated from the slaughter line before start of activities. The prevalence of Salmonella in the plucking area was 10.4% (38/365) (hanging area: 5.0%, scalding tank: 5.8%, plucking machine: 17.0%); in the evisceration room, 1.5% (2/138); and in the cutting area, 2.0% (3/149). No Salmonella (0/28) was found in samples from the chilling line. On neck skin samples taken from the various lines, Salmonella prevalence was 16.1% (48/299) after plucking, 16.0% (48/300) after evisceration, 23.3% (70/300) after chilling; on thighs, prevalence was 10.0% (24/240). Nine Salmonella serotypes were identified of which Salmonella Infantis was the most common serovar (53.8%), especially in slaughterhouse A. Two contamination causes were identified; first, although all flocks had an official Salmonella negative status, this was in one case incorrect and led to an enormous contamination of the neck skins of the flock and the slaughterline (i.e., cooling water). Second, molecular typing revealed cross-contamination from flocks slaughtered 1 d before sampling. Salmonella was apparently not always eliminated by the cleaning and disinfection process and able to contaminate the carcasses of the first slaughtered flock. In conclusion, the results of this study provided practical insights for poultry production to further improve their Salmonella control, for example, Salmonella status determination closer to the slaughter date, to adapt cleaning and disinfection protocols especially for critical machinery and better hygienic designed equipment

Occurrence, distribution and diversity of Listeria monocytogenes contamination on beef and pig carcasses after slaughter

In this study we investigated the prevalence and location of Listeria monocytogenes and hygiene indicator bacteria on beef and pig carcasses. Carcasses were sampled after slaughter and before cooling at eight and nine sites on the carcass, respectively. For each sample, detection and enumeration of Listeria was performed, as well as the enumeration of Total Aerobic Counts (TAC) and Enterobacteriaceae. The L. monocytogenes isolates were also typed to determine pulsotypes and clonal complexes (CC). L. monocytogenes was detected on 46% [95% CI: 35-56%] of beef and 22% [95% CI: 11-32%] of pig carcasses. Contamination levels at the different carcass sites differed considerably between beef and pigs. Genetic typing of strains suggests that carcass contamination originates from both incoming animals with transmission during slaughter practices as well as persistent (CC9) contamination from the slaughterhouse environment. These findings can be used to understand the complexity of introduction and persistence of this pathogen in slaughter facilities. Accurate correlation of L. monocytogenes presence proved unfeasible with any of the tested hygiene indicator bacteria

Is competitive exclusion a valuable alternative for classical cleaning and disinfection of pig-growing units?

Colonization of the environment of pig-growing units by pathogenic microrganisms is an important factor in development of endemic diseases in pigs and, in spreading of zoonotic diseases. These pathogens are mostly controlled by the use of antibiotics and disinfection during vacancy. Because, the past years an increasing resistance against these measures is noticed, alternative methods such as competitive exclusion (CE) are promoted as promising. In this study the effect of a CE protocol on the bacterial infection in piggrowing units was compared to a classical cleaning and disinfection (C&D) protocol. Tests were performed during three successive production rounds using multiple identical pig-growing units. CE protocol consisted of cleaning (no disinfection) after loading piglets and spraying probiotic bacteria (Bacillus spp. spores) during vacancy and production. The cleaning product also contained Bacillus spores. Sampling was performed at different time-points: immediately after pig loading (manure still present); 24 hours after cleaning (CE units) or after disinfection (control units); after one week and five weeks of production (piglets present). At each time point, swab samples for analyses were taken. Enumerations of bacterial spores, Enterococcus spp., E. coli, fecal coliforms and MRSA and detections of E. coli, fecal coliforms and MRSA were performed. Next to bacterial analyses, also feed conversion and fecal consistency was monitored. This study showed that, although probiotic spores were administered well, the analyzed bacteria were not decreased after three production rounds in CE units and remained on the same level as the control units (C&D). Also, the infection pressure in CE units during vacancy was not as much reduced as after the disinfection-step in control units. Finally, no differences in feed conversion and fecal consistency were found. These results indicate that the used CE protocol is not a valuable alternative for classical C&D

Comparison of competitive exclusion with classical cleaning and disinfection on bacterial load in pig nursery units

Background: Colonisation of the environment of nursery units by pathogenic micro-organisms is an important factor in the persistence and spread of endemic diseases in pigs and zoonotic pathogens. These pathogens are generally controlled by the use of antibiotics and disinfectants. Since an increasing resistance against these measures has been reported in recent years, methods such as competitive exclusion (CE) are promoted as promising alternatives. Results: This study showed that the infection pressure in CE units after microbial cleaning was not reduced to the same degree as in control units. Despite sufficient administration of probiotic-type spores, the analysed bacteria did not decrease in number after 3 production rounds in CE units, indicating no competitive exclusion. In addition, no differences in feed conversion were found between piglets raised in CE and control units in our study. Also, no differences in faecal consistency (indicator for enteric diseases) was noticed. Conclusion: These results indicate that the CE protocol is not a valuable alternative for classical C&D

Effect of subinhibitory exposure to quaternary ammonium compounds on the ciprofloxacin susceptibility ofEscherichia colistrains in animal husbandry

Background Quaternary ammonium compound based disinfectants are commonly used in pig and poultry husbandry to maintain farm hygiene. However, studies have shown that subinhibitory concentrations of these disinfectants may increase antibiotic resistance. Investigation of antibiotic susceptibility is usually assessed via the microbroth dilution method, although this conventional culture-based technique only provides information on the bacteriostatic activity of an antimicrobial agent. Therefore, experiments were performed to investigate the effect of prior benzalkonium chloride (BKC) exposure on the viability of subsequent ciprofloxacin (CIP) treatedEscherichia coli. Results Following CIP treatment, bacterial cell counts were significantly higher after exposure to a subinhibitory BKC concentration than without BKC exposure. The flow cytometric results suggested a BKC-dependent onset of membrane damage and loss of membrane potential. Conclusion Our results indicate a lower bactericidal effect of CIP treatment on BKC-exposedE. coliisolates compared to unexposedE. coliisolates

Repeated disinfectant use in broiler houses and pig nursery units does not affect disinfectant and antibiotic susceptibility in Escherichia coli field isolates

Background Disinfectants are frequently used in animal production to reduce or eliminate the load of infectious agents and parasites in buildings and equipment associated with the housing or transportation of animals. There are growing concerns that the use of disinfectants would select for resistance to antibiotics and disinfectants. The aim of this study was to determine the effect of repeated use of different disinfectants on the disinfectant and antibiotic susceptibility under practical conditions in a broiler and pig pilot farm. Therefore, the susceptibility of Escherichia coli (E. coli) to 14 antibiotics and 4 disinfectants was monitored over a one-year period. Results High (20-50%) to very high (> 50%) resistance levels for ampicillin, sulfamethoxazole, trimethoprim and tetracycline were observed in both animal production types. Disinfectant susceptibility did not change over time and did not depend on the used disinfection product. Compared to in-use concentrations of formaldehyde, benzalkoniumchloride and a peracetic acid - hydrogen peroxide formulation, all E. coli strains remained susceptible indicating that the use of disinfectants did not select for disinfectant resistance. Moreover, no association could be found between the use of disinfectants and antibiotic resistance. Conclusions These findings suggest that repeated use of disinfectants in agricultural environments does not select for antibiotic resistance nor does it reduce disinfectant susceptibility