Prevalence of eae-positive, lactose non-fermenting Escherichia albertii from retail raw meat in China

Growth and Survival of Escherichia albertii in Food and Environmental Water at Various Temperatures

Escherichia albertii is an emerging foodborne pathogen that causes diarrhea. E. albertii has been isolated from various foods, including pork and chicken meat, and environmental waters, such as river water. Although many food poisoning cases have been reported, there have been insufficient analyses of bacterial population behaviors in food and environmental water. In this study, we inoculated 2-5 log CFU of E. albertii into 25 g of pork, chicken meat, Japanese rock oyster, Pacific oyster, and 300 mL of well water and seawater at 4°C, 10°C, 20°C, and 30°C, and analyzed the bacterial population behavior in food and environmental water. After 3 days at 4°C, the population of E. albertii strain EA21 and EA24 in foods maintained approximately 4 log CFU/25 g. After 3 days at 10°C, the population of E. albertii strains in pork and oysters maintained approximately 4 log CFU/25 g, and that in chicken meat increased to approximately 5-6 log CFU/25 g. After 2 days at 20°C, E. albertii strains grew to approximately 6-7 log CFU/25 g in pork and chicken meat, and E. albertii strain EA21 but not EA24 grew to 4.5 log CFU/25 g in Japanese rock oyster, E. albertii strain EA21 but not EA24 slightly grew to 3.1 log CFU/25 g in Pacific oyster. After 1 day at 30°C, E. albertii strains grew to approximately 7-8 log CFU/25 g in chicken meat and pork, grew to approximately 4-6 log CFU/25 g in Japanese rock oyster, and 6-7 log CFU/25 g in Pacific oyster. These results suggest that E. albertii survives without growth below 4°C and grew rapidly at 20°C and 30°C in foods, especially in meat. E. albertii strains did not grow in well water and seawater at 4°C, 10°C, 20°C, and 30°C. The population of E. albertii strains in well water and seawater decreased faster at 30°C than at 4°C, 10°C, and 20°C, suggesting that E. albertii has low viability at 30°C in environmental water.

Escherichia albertii isolated from the bloodstream of a patient with liver cirrhosis in China: A case report

A rare case of bacteremia caused by Escherichia albertii, in a 50-year-old male with liver cirrhosis was reported. Clear, colorless, and circular colonies were recovered on blood agar after 24 h of aerobic incubation at 37 °C. The isolate was identified as E. albertii using MALDI-TOF/MS and confirmed by the diagnostic triplex-PCR targeting clpX, lysP, and mdh genes. The administration of piperacillin/tazobactam intravenously (4.5g every 8 hours) for 3 days was effective. This study suggested that specific strains of E. albertii have been implicated in causing extraintestinal infections in humans, similar to extraintestinal pathogenic E. coli (ExPEC). However, a comprehensive understanding of the underlying pathogenic mechanisms requires further exploration.

Escherichia albertii as a Potential Enteropathogen in the Light of Epidemiological and Genomic Studies

Escherichia albertii is a new enteropathogen of humans and animals. The aim of the study was to assess the prevalence and pathogenicity of E. albertii strains isolated in northeastern Poland using epidemiological and genomic studies. In 2015-2018, a total of 1154 fecal samples from children and adults, 497 bird droppings, 212 food samples, 92 water samples, and 500 lactose-negative E. coli strains were tested. A total of 42 E. albertii strains were isolated. The PCR method was suitable for their rapid identification. In total, 33.3% of E. albertii isolates were resistant to one antibiotic, and 16.7% to two. Isolates were sensitive to cefepime, imipenem, levofloxacin, gentamicin, trimethoprim/sulfamethoxazole, and did not produce ESBL β-lactamases. High genetic variability of E. albertii has been demonstrated. In the PFGE method, 90.5% of the strains had distinct pulsotypes. In MLST typing, 85.7% of strains were assigned distinct sequence types (STs), of which 64% were novel ST types. Cytolethal distending toxin (CDT) and Paa toxin genes were found in 100% of E. albertii isolates. Genes encoding toxins, IbeA, CdtB type 2, Tsh and Shiga (Stx2f), were found in 26.2%, 9.7%, 1.7%, and 0.4% of E. albertii isolates, respectively. The chromosome size of the tested strains ranged from 4,573,338 to 5,141,010 bp (average 4,784,003 bp), and at least one plasmid was present in all strains. The study contributes to a more accurate assessment of the genetic diversity of E. albertii and the potential threat it poses to public health.

Melibiose–X-Gal–MacConkey Agar for Presumptive Differentiation of Escherichia albertii from E. coli and Salmonella from Poultry Meat

The bacterial foodborne enteropathogen Escherichia albertii, despite enjoying increased attention paid to its pathogenesis, global dissemination, and antimicrobial resistance capacity, remains difficult to identify from human foods. The primary objective of this study was to develop and test a selective and differential plating medium for the isolation of E. albertii from enteric pathogens commonly transmitted via fresh poultry meat, namely E. coli and Salmonella enterica. MacConkey agar supplemented with α-D-+-melibiose and the lactose analogue X-gal was prepared and used to differentially enumerate E. albertii, Salmonella, and E. coli from inoculated ground chicken meat. The medium, MXgMac agar, differentiated the inoculated pathogens with a greater degree of efficiency than did the previously developed E. albertii-selective medium xylose–rhamnose–melibiose (XRM) MacConkey agar, based on differential usage of the lactose analogue and melibiose. Chicken-derived feces and litter samples were subsequently tested using the medium and found not to contain E. albertii by 16S rRNA gene amplification. MXgMac agar facilitates improved differential recovery of E. albertii and other enteric pathogens from poultry meat versus other E. albertii selective/differential media.

Identification and Genomic Characterization of Escherichia albertii in Migratory Birds from Poyang Lake, China

Escherichia albertii is an emerging zoonotic foodborne enteropathogen leading to human gastroenteritis outbreaks. Although E. albertii has been isolated from birds which have been considered as the potential reservoirs of this bacterium, its prevalence in migratory birds has rarely been described. In this study, E. albertii in migratory birds from Poyang Lake was investigated and characterized using whole genome sequencing. Eighty-one fecal samples from nine species of migratory birds were collected and 24/81 (29.6%) tested PCR-positive for E. albertii-specific genes. A total of 47 isolates was recovered from 18 out of 24 PCR-positive samples. All isolates carried eae and cdtB genes. These isolates were classified into eight E. albertii O-genotypes (EAOgs) (including three novel EAOgs) and three E. albertii H-genotypes (EAHgs). Whole genome phylogeny separated migratory bird-derived isolates into different lineages, some isolates in this study were phylogenetically closely grouped with poultry-derived or patient-derived strains. Our findings showed that migratory birds may serve as an important reservoir for heterogeneous E. albertii, thereby acting as potential transmission vehicles of E. albertii to humans.

Development of a Novel Real-Time Polymerase Chain Reaction Assay to Detect Escherichia albertii in Chicken Meat

Escherichia albertii is an emerging enteropathogen. Several foodborne outbreaks of E. albertii have been reported in Japan; however, foods associated with most outbreaks remain unidentified. Therefore, polymerase chain reaction (PCR) assays detecting E. albertii specifically and sensitively are required. Primers and probe for real-time PCR assays targeting E. albertii-specific gene (EA-rtPCR) was designed. With 74 strains, including 43 E. albertii strains and several of its close relatives, EA-rtPCR specifically amplified E. albertii; therefore, the sensitivity of EA-rtPCR was then evaluated. The detection limits were 2.8 and 2.0-3.2 log colony-forming unit (CFU)/mL for E. albertii culture and enriched chicken culture inoculated with the pathogen, respectively. In addition, E. albertii was detected from 25 g of chicken meat inoculated with 0.1 log CFU of the pathogen by EA-rtPCR. The detection of E. albertii from chicken meat by EA-rtPCR was also evaluated by comparing with the nested-PCR assay, and 28 retail chicken meat and 193 dissected body parts from 21 chicken carcass were tested. One and three chicken meat were positive in the nested-PCR assay and EA-rtPCR, respectively. Fourteen carcasses had at least one body part that was positive for EA-rtPCR, and 36 and 48 samples were positive for the nested-PCR assay and EA-rtPCR, respectively. A total of 37 strains of E. albertii were isolated from seven PCR-positive samples obtained from six chicken carcass. All E. albertii isolates harbored eae gene, and were classified as E. albertii O-genotype (EAOg)3 or EAOg4 by EAO-genotyping. The EA-rtPCR developed in this study has potential to improve E. albertii detection in food and advance research on E. albertii infection.

Occurrence and Characteristics of Escherichia albertii in Wild Birds and Poultry Flocks in Switzerland

Escherichia albertii, a zoonotic pathogen, has sporadically been associated with infectious diarrhea in humans. Poultry and wild birds are considered potential reservoirs. We assessed the occurrence of E. albertii in 280 fecal samples from wild birds (n = 130) and pooled fecal samples collected at slaughterhouse level from poultry flocks (n = 150) in Switzerland. Using an E. albertii-specific PCR targeting the Eacdt gene, 23.8% (31/130) of the samples from wild birds, but not from the pooled poultry fecal samples, tested positive for Eacdt. The positive samples originated from 11 bird species belonging to eight families. Strain isolation was attempted on the PCR-positive samples by subculturing the broth cultures onto xylose–MacConkey plates. Isolation was possible on 12 of the 31 Eacdt-PCR-positive samples. Whole-genome sequencing revealed that the strains belonged to nine distinct sequence types, with ST13420 and ST5967 being represented by two and three isolates, respectively. All strains harbored the eae gene, while two strains were also positive for stx2f. Our study thus shows that E. albertii is present in the Swiss wild bird population, which can potentially act as a source of this pathogen to humans, other animals, and the environment.

Isolation and characterization of Escherichia albertii from wild and safeguarded animals in Okayama Prefecture and its prefectural borders, Japan

Escherichia albertii has recently been recognized as a zoonotic enteropathogen associated with food poisoning. The reservoirs and transmission routes of this bacterium to humans are still unclear. In this study, we performed a survey of E. albertii in fecal specimens of wild and safeguarded animals in Okayama Prefecture and its prefectural borders, Japan to understand its reservoir in the environment. Forty-two E. albertii were isolated from 10 and 31 droppings of 59 crows and 125 starlings, respectively. Fifty-two E. albertii were isolated from 906 mammal droppings, and out of 52 isolates, origin of 33, 6 and 1 isolates were from martens, foxes, and rabbit, respectively, however, origin of 12 isolates remained unknown. Three E. albertii were isolated from two and one feces of 159 dogs and 76 cats, respectively. Pulsed-filed gel electrophoresis analysis grouped 97 E. albertii strains into 66 pulsotypes including 36 and 30 pulsotypes of isolates from mammals and birds, respectively. E. albertii strains isolated in this study were genetically diverse. Although clonal relationship was not observed between mammal and bird isolates, there were intra- and inter-species relationship in mammalian isolates. All E. albertii strains were positive for eae and Eacdt virulence genes. Furthermore, 20 and 7 strains also carried Eccdt-I and stx2f genes, respectively. Taken together, the results indicate that genetically diverse and potentially virulent E. albertii are distributed among various wild and safeguarded animals in Okayama Prefecture, and the animals could also be reservoirs of E. albertii.

Microbiology and Epidemiology of Escherichia albertii—An Emerging Elusive Foodborne Pathogen

Escherichia albertii, a close relative of E. coli, is an emerging zoonotic foodborne pathogen associated with watery diarrhea mainly in children and immunocompromised individuals. E. albertii was initially classified as eae-positive Hafnia alvei, however, as more genetic and biochemical information became available it was reassigned to its current novel taxonomy. Its infections are common under conditions of poor hygiene with confirmed transmission via contaminated water and food, mainly poultry-based products. This pathogen has been isolated from various domestic and wild animals, with most isolates being derived from birds, implying that birds among other wild animals might act as its reservoir. Due to the absence of standardized isolation and identification protocols, E. albertii can be misidentified as other Enterobacteriaceae. Exploiting phenotypes such as its inability to ferment rhamnose and xylose and PCR assays targeting E. albertii-specific genes such as the cytolethal distending toxin and the DNA-binding transcriptional activator of cysteine biosynthesis encoding genes can be used to accurately identify this pathogen. Several gaps exist in our knowledge of E. albertii and need to be bridged. A deeper understanding of E. albertii epidemiology and physiology is required to allow the development of effective measures to control its transmission and infections. Overall, current data suggest that E. albertii might play a more significant role in global infectious diarrhea cases than previously assumed and is often overlooked or misidentified. Therefore, simple, and efficient diagnostic tools that cover E. albertii biodiversity are required for effective isolation and identification of this elusive agent of diarrhea.

Detection of Escherichia albertii in Retail Oysters

ABSTRACT

Escherichia albertii is an emerging foodborne pathogen. Owing to its distribution in river water, it is important to determine the presence of E. albertii in aquaculture-related foods. In this study, we investigated the distribution of E. albertii in retail oyster samples. A total of 427 raw oyster samples (385 Pacific oysters and 42 Japanese rock oysters) were enriched in modified Escherichia coli broth (mEC) or mEC supplemented with novobiocin (NmEC) at 42°C. The cultures were used for E. albertii-specific nested PCR assay, as well as for E. albertii isolation using deoxycholate hydrogen sulfide lactose agar (DHL), DHL supplemented with rhamnose and xylose, and MacConkey agar supplemented with rhamnose and xylose. The population of E. albertii in nested PCR-positive samples was determined using the most-probable-number (MPN) method. E. albertii isolates were subjected to biochemical and genetic characterization. E. albertii was detected in 5 (1.6%) of 315 Pacific oyster samples (one piece each), 2 (2.9%) of 70 Pacific oyster samples (25 g each), and 2 (4.8%) of 42 Japanese rock oyster samples procured from four geographically distinct regions. A total of 64 E. albertii strains were isolated from eight of the nine nested PCR assay-positive oyster samples, and the MPN value was under the detection limit (<3 MPN/10 g). A specific season or month for detecting E. albertii was not observed in this study, suggesting that the pathogen is present in seawater. All the E. albertii isolates, except one, were positive for the virulence factor eae, indicating that these isolates have the potential to infect humans.

HIGHLIGHTS

Comparative genomics of Chinese and international isolates of Escherichia albertii: population structure and evolution of virulence and antimicrobial resistance

Escherichia albertii is a recently recognized species in the genus Escherichia that causes diarrhoea. The population structure, genetic diversity and genomic features have not been fully examined. Here, 169 E. albertii isolates from different sources and regions in China were sequenced and combined with 312 publicly available genomes (from additional 14 countries) for genomic analyses. The E. albertii population was divided into two clades and eight lineages, with lineage 3 (L3), L5 and L8 more common in China. Clinical isolates were observed in all clades/lineages. Virulence genes were found to be distributed differently among lineages: subtypes of the intimin encoding gene eae and the cytolethal distending toxin gene cdtB were lineage associated, and the second type three secretion system (ETT2) island was truncated in L3 and L6. Seven new eae subtypes and one new cdtB subtype (cdtB-VI) were identified. Alarmingly, 85.9 % of the Chinese E. albertii isolates were predicted to be multidrug-resistant (MDR) with 35.9 % harbouring genes capable of conferring resistance to 10 to 14 different drug classes. The majority of the MDR isolates were of poultry source from China and belonged to four sequence types (STs) [ST4638, ST4479, ST4633 and ST4488]. Thirty-four plasmids with some carrying MDR and virulence genes, and 130 prophages were identified from 17 complete E. albertii genomes. The 130 intact prophages were clustered into five groups, with group five prophages harbouring more virulence genes. We further identified three E. albertii specific genes as markers for the identification of this species. Our findings provided fundamental insights into the population structure, virulence variation and drug resistance of E. albertii.

[Molecular epidemiology of Escherichia albertii, emerging zoonotic enteropathogen]

Escherichia albertii is an emerging zoonotic enteric pathogen, closely related to E. coli. Several foodborne outbreaks caused by E. albertii accounting for >100 patients have recently occurred in Japan. This bacterium carries eae gene, similar to enteropathogenic E. coli. Some of them harbor Shiga toxin 2 (stx2a, stx2f) genes, primary virulence factor of enterohemorrhagic E. coli (EHEC), suggesting that the Stx2 producers could cause severe diseases such as HUS in humans. However, due to lack of the knowledges about its bacteriological characteristics and of the diagnostic methods, E. albertii-related infections might have been underestimated, and the infection sources and routes have not yet been understood. We had continuously performed molecular epidemiological studies targeting for cytolethal distending toxin-producing E. coli, and unexpectedly found that cdt-II gene-positive isolates were not E. coli but E. albertii. This finding led us to initiate research more focusing on E. albertii. We have constructed simple, efficient and reliable methods for the detection, isolation and identification of this bacterium by developing an E. albertii-specific PCR assay targeting Eacdt genes and E. albertii-selective isolation medium named XRM-MacConkey agar. We have also identified raccoons as a potential natural reservoir of E. albertii through wildlife survey using these methods. Here, I describe what I have studied with my colleagues.

Proposal of a novel selective enrichment broth, NCT-mTSB, for isolation of Escherichia albertii from poultry samples

AIMS

Escherichia albertii is an emerging diarrheagenic pathogen causing food- and water-borne infection in humans. However, no selective enrichment broths for E. albertii have ever been reported. In this study, we tested several basal media, selective supplements and culture conditions which enabled selective enrichment of E. albertii.

METHODS AND RESULTS

We developed a selective enrichment broth, novobiocin-cefixime-tellurite supplemented modified tryptic soy broth (NCT-mTSB). NCT-mTSB supported the growth of 22 E. albertii strains, while inhibited growth of other Enterobacteriaceae at 37°C, except for Escherichia coli and Shigella spp. Enrichment of E. albertii was improved further by growth at 44°C, a temperature that suppresses growth of several strains of E. coli/Shigella. Combined use of NCT-mTSB with XR-DH-agar, xylose-rhamnose supplemented deoxycholate hydrogen sulphide agar, enabled isolation of E. albertii when at least 1 CFU of the bacterium was present per gram of chicken meat. This level of enrichment was superior to those obtained using buffered peptone water, modified-EC broth, or mTSB (with novobiocin).

CONCLUSIONS

Novobiocin-cefixime-tellurite supplemented modified tryptic soy broth enabled effective enrichment of E. albertii from poultry samples and was helpful for isolation of this bacterium.

SIGNIFICANCE AND IMPACT OF STUDY

To our knowledge, this is the first report of selective enrichment of E. albertii from poultry samples.

Detection, isolation and molecular characterization of Escherichia albertii in wild birds in West Japan

Escherichia albertii is an emerging zoonotic foodborne pathogen. Several outbreaks of E. albertii have occurred particularly in Japan. Although birds have been considered as one of the most important reservoirs of this bacterium, information regarding the prevalence in birds is still scanty. We performed a survey of E. albertii in wild birds in Japan, and examined characteristics of the isolates. E. albertii specific gene was detected in 5 cloacal swabs out of 156 birds by PCR. Four E. albertii were isolated from a swallow with 2 different E. albertii strains and 2 pigeons in a flock by XRM-MacConkey agar. These isolates were assigned to biogroup 3, shown no resistance to any antimicrobials tested, and classified into 2 EAO-genotypes (EAOg2 and EAOg33) and untypable. Similar to clinical E. albertii strains, these isolates carried virulence genes including eae (n=4), paa (n=4), Eccdt-I (n=2) and stx2f (n=1) in addition to Eacdt. Interestingly, stx2f genes in a strain were located on an inducible bacteriophage, which can confer the ability to produce Stx2f to E. coli. In conclusion, Japanese wild birds carried E. albertii at the similar levels to the reported prevalence in birds. These isolates may have a potential to cause gastroenteritis in humans.

Detection of Escherichia Albertii in Urinary and Gastrointestinal Infections in Kermanshah, Iran

Background: Escherichia albertii has been recently isolated from the feces of people with gastroenteritis as a pathogen that causes diarrhea. Due to insufficient information on the phenotypic and biochemical characteristics of E. albertii, it is difficult to distinguish it from other species of the Enterobacteriaceae family and, therefore, it is mistakenly identified as Escherichia coli or even Hafnia alvei. Objective: The present study which was conducted for the first time in Iran aimed to identify E. albertii in samples from individuals afflicted with urinary and gastrointestinal infections by using the polymerase chain reaction (PCR) method. The required samples were obtained from clinical laboratories in Kermanshah. Materials and Methods: Firstly, a total of 60 urinary and 40 fecal samples identified as E. coli in clinical laboratories were re-evaluated in terms of specific phenotypic and biochemical characteristics of E. coli. Then, two lysP and mdh genes were detected for E. albertii, and the uidA gene was found for E. coli by PCR using specific primers pairs. Results: The results from phenotypic and biochemical tests indicated that all samples shared common characteristics with E. coli. However, PCR findings demonstrated that out of 100 samples, 6 samples (6%) contained specific genes of E. coli while 94 remaining samples (94%) showed the uidA gene. Out of the given 6 samples, 5 samples carried urinary tract infections and only one showed gastrointestinal infection. Conclusion: Our study findings revealed that E. albertii could have been considered as one of the causes for urinary and gastrointestinal infections in Iran, and that it was mistakenly identified as E. coli in clinical laboratories.

Isolation and Identification of Escherichia albertii in Broiler Chickens From Kermanshah

Background: F Escherichia albertii is generally recognized as a human pathogen with a limited number of strains. It has also been identified as a cause of mortality among birds. The clinical significance and prevalence of E. albertii are somewhat unknown. Objectives: The aim of the present study was to isolate and identify E. albertii as a causative agent of respiratory infections in broilers. Materials and Methods: During a three-month period (Winter 2018), 200 samples of the air sacs of 100 chickens with suspected colibacillosis were collected. Routine biochemical tests were performed and suspected isolates of E. albertii were selected for polymerase chain reaction (PCR). Results: A total of 68 suspected samples of E. albertii and Escherichia coli were isolated. Further, E. coli was detected in all the suspected samples using species-specific sequences of E. coli (uidA) and E. albertii (mdh and lysP). Conclusion: Escherichia albertii was not identified as a cause of respiratory infection in broilers.

Isolation and characterization of Escherichia albertii in poultry at the pre-harvest level

Escherichia albertii, often misidentified as Escherichia coli, has become an emerging foodborne human enteric pathogen. However, the prevalence and major animal reservoirs of this significant pathogen are still not clear. Here, we performed comprehensive microbiological, molecular, comparative genomics and animal studies to understand the status and features of E. albertii in the US domestic and food animals. Although no E. albertii was identified in a total of 1,022 diverse E. coli strains isolated from pets and food animals in a retrospective screening, in a pilot study, E. albertii was successfully isolated from a broiler farm (6 out of 20 chickens). The chicken E. albertii isolates showed clonal relationship as indicated by both pulsed-field gel electrophoresis (PFGE) and whole-genome sequence analysis. The isolated chicken E. albertii displayed multidrug resistance; all the resistance determinants including the extended-spectrum beta-lactamase gene, carried by plasmids, could be conjugatively transferred to E. coli, which was further confirmed by S1-PFGE and Southern hybridization. Whole-genome sequence-based phylogenetic analysis showed the chicken E. albertii strains were phylogenetically close to those of human origins. Challenge experiment demonstrated that the E. albertii strains isolated from human and wild bird could successfully colonize in the chicken intestine. Together, this study, for the first time, reported the isolation of E. albertii in poultry at the pre-hrvest level. The findings from multi-tier characterization of the chicken E. albertii strains indicated the importance of chickens as a reservoir for E. albertii. A large scale of E. albertii survey in poultry production at the pre-harvest level is highly warranted in the future.

Escherichia albertii Pathogenesis

Escherichia albertii is an emerging enteropathogen of humans and many avian species. This bacterium is a close relative of Escherichia coli and has been frequently misidentified as enteropathogenic or enterohemorrhagic E. coli due to their similarity in phenotypic and genetic features, such as various biochemical properties and the possession of a type III secretion system encoded by the locus of enterocyte effacement. This pathogen causes outbreaks of gastroenteritis, and some strains produce Shiga toxin. Although many genetic and phenotypic studies have been published and the genome sequences of more than 200 E. albertii strains are now available, the clinical significance of this species is not yet fully understood. The apparent zoonotic nature of the disease requires a deeper understanding of the transmission routes and mechanisms of E. albertii to develop effective measures to control its transmission and infection. Here, we review the current knowledge of the phylogenic relationship of E. albertii with other Escherichia species and the biochemical and genetic properties of E. albertii, with particular emphasis on the repertoire of virulence factors and the mechanisms of pathogenicity, and we hope this provides a basis for future studies of this important emerging enteropathogen.

Escherichia albertii EA046 (O9) harbors two polysaccharide gene clusters for synthesis of the O-antigen by the Wzx/Wzy-dependent pathway and a mannan shared by Escherichia coli O8 by the Wzm/Wzt-dependent pathway

O antigen is a polysaccharide chain of a lipopolysaccharide on the outer membrane of Gram-negative bacteria. O-antigen-based serotyping and molecular typing are widely used for epidemiological and surveillance purposes. Two polysaccharides were isolated by Sephadex G-50 gel-permeation chromatography following mild acid degradation of the lipopolysaccharide of Escherichia albertii EA046 assigned to serotype O9. The polysaccharide eluted first was considered as the O-antigen. It was composed of tetrasaccharide repeating units containing two residues of d-Man and one residue each of d-Gal and d-GlcNAc as well as glycerol phosphate. It had the following unique structure which was established by NMR spectroscopy applied to the initial and dephosphorylated polysaccharides: The polysaccharide eluted from the gel second was identified as a mannan with a → 3)-β-d-Manp-(1 → 2)-α-d-Manp-(1 → 2)-α-d-Manp-(1 → trisaccharide repeating unit. In E. albertii EA046, two polysaccharide gene clusters were found at a chromosomal locus flanked by the conserved galF gene and the histidine synthesis operon (his). They were suggested to drive the biosynthesis of the O-antigen by the Wzy/Wzy-dependent pathway and the mannan by the Wzm/Wzt-dependent pathway. The mannan shares the structure and gene cluster with a polysaccharide isolated earlier from the lipopolysaccharide of Escherichia coli O8.

Non-biogroup 1 or 2 Strains of the Emerging Zoonotic Pathogen Escherichia albertii, Their Proposed Assignment to Biogroup 3, and Their Commonly Detected Characteristics

Escherichia albertii, a zoonotic enteropathogen, is responsible for outbreaks of disease in humans. Identifying strains of E. albertii by phenotypic characterization tests is difficult because of its poorly defined properties. Screening its phenotypic characteristics is, nevertheless, a necessary prerequisite for further genetic analysis of its properties, and species-specific polymerase chain reaction (PCR) analysis can be used to type the pathogen. While two E. albertii biogroups (1 and 2) have been described, strains with characteristics divergent from both biogroups have been reported worldwide. The aim of the present study was to evaluate the characteristics of non-biogroup 1 or 2 strains, and discern the characteristics common to all of the E. albertii strains from this study. Altogether, 107/414 field isolates were selected for examination based on pulsed-field gel electrophoresis analysis. The 107 strains were isolated from 92 sources, including humans and pigeon feces, other wild birds, and retail chicken livers. All strains were then examined using various culture-based, biochemical (API 50CHE tests, API Zym test, and others) and molecular (virulence gene screening, multi-locus sequence analysis) testing methods. Our results revealed that all field strains (n = 107) showed non-biogroup 1 or 2 characteristics, with multiple sequence differences. Variations in indole production and the lysine decarboxylase activity profiles among the isolates made identification of E. albertii very difficult. Therefore, we propose that non-biogroup 1 or 2 of E. albertii should be assigned to biogroup 3 to make screening of them easier in public health and clinical laboratory settings. Clearly, having group criteria for indole-negative/lysine-positive, indole-positive/lysine-negative, and indole-positive/lysine-positive E. albertii biogroups 1, 2, and 3 strains, respectively, should provide for more accurate identification of E. albertii isolates. Based on our findings, we recommend that isolates displaying phenotype mobility-negativity (sulfide-indole-motility medium, 37°C), hydrogen sulfide production-negativity (triple sugar iron medium), acid production-negativity from xylose, negative β-glucuronidase activity properties, and showing indole production and lysine decarboxylase activity profiles in accordance with one of the three biogroups, should be further assessed using an E. albertii-specific PCR assay.

The Evasive Enemy: Insights into the Virulence and Epidemiology of the Emerging Attaching and Effacing Pathogen Escherichia albertii

The diarrheic attaching and effacing (A/E) pathogen Escherichia albertii was first isolated from infants in Bangladesh in 1991, although the bacterium was initially classified as Hafnia alvei Subsequent genetic and biochemical interrogation of these isolates raised concerns about their initial taxonomic placement. It was not until 2003 that these isolates were reassigned to the novel taxon Escherichia albertii because they were genetically more closely related to E. coli, although they had diverged sufficiently to warrant a novel species name. Unfortunately, new isolates continue to be mistyped as enteropathogenic E. coli (EPEC) or enterohemorrhagic E. coli (EHEC) owing to shared traits, most notably the ability to form A/E lesions. Consequently, E. albertii remains an underappreciated A/E pathogen, despite multiple reports demonstrating that many provisional EPEC and EHEC isolates incriminated in disease outbreaks are actually E. albertii Metagenomic studies on dozens of E. albertii isolates reveal a genetic architecture that boasts an arsenal of candidate virulence factors to rival that of its better-characterized cousins, EPEC and EHEC. Beyond these computational comparisons, studies addressing the regulation, structure, function, and mechanism of action of its repertoire of virulence factors are lacking. Thus, the paucity of knowledge about the epidemiology, virulence, and antibiotic resistance of E. albertii, coupled with its misclassification and its ability to develop multidrug resistance in a single step, highlights the challenges in combating this emerging pathogen. This review seeks to synthesize our current but incomplete understanding of the biology of E. albertii.

Multidrug-Resistant Escherichia albertii: Co-occurrence of β-Lactamase and MCR-1 Encoding Genes

Escherichia albertii is an emerging member of the Enterobacteriaceae causing human and animal enteric infections. Antimicrobial resistance among enteropathogens has been reported to be increasing in the past years. The purpose of this study was to investigate antibiotic resistance and resistance genes in E. albertii isolated from Zigong city, Sichuan province, China. The susceptibility to 21 antimicrobial agents was determined by Kirby-Bauer disk diffusion method. The highest prevalence was tetracycline resistance with a rate of 62.7%, followed by resistance to nalidixic acid and streptomycin with a rate of 56.9 and 51.0%, respectively. All isolates were sensitive or intermediate susceptible to imipenem, meropenem, amoxicillin-clavulanic acid, and levofloxacin. Among 51 E. albertii isolates, 15 were extended-spectrum β-lactamase-producing as confirmed by the double disk test. The main β-lactamase gene groups, i.e., blaTEM, blaSHV, and blaCTX-M, were detected in17, 20, and 22 isolates, respectively. Furthermore, four colistin-resistant isolates with minimum inhibitory concentrations of 8 mg/L were identified. The colistin-resistant isolates all harbored mcr-1 and blaCTX-M-55. Genome sequencing showed that E. albertii strain SP140150 carried mcr-1 and blaCTX-M-55 in two different plasmids. This study provided significant information regarding antibiotic resistance profiles and identified the co-occurrence of β-lactamase and MCR-1 encoding genes in E. albertii isolates.

Characterization of four Escherichia albertii isolates collected from animals living in Antarctica and Patagonia

Escherichia albertii is a recently discovered species with a limited number of well characterized strains. The aim of this study was to characterize four of the E. albertii strains, which were among 41 identified Escherichia strains isolated from the feces of living animals on James Ross Island, Antarctica, and Isla Magdalena, Patagonia. Sequencing of 16S rDNA, automated ribotyping, and rep-PCR were used to identify the four E. albertii isolates. Phylogenetic analyses based on multi-locus sequence typing showed these isolates to be genetically most similar to the members of E. albertii phylogroup G3. These isolates encoded several virulence factors including those, which are characteristic of E. albertii (cytolethal distending toxin and intimin) as well as bacteriocin determinants that typically have a very low prevalence in E. coli strains (D, E7). Moreover, E. albertii protein extracts caused cell cycle arrest in human cell line A375, probably because of cytolethal distending toxin activity.

Defining the Genetic Features of O-Antigen Biosynthesis Gene Cluster and Performance of an O-Antigen Serotyping Scheme for Escherichia albertii

Escherichia albertii is a newly described and emerging diarrheagenic pathogen responsible for outbreaks of gastroenteritis. Serotyping plays an important role in diagnosis and epidemiological studies for pathogens of public health importance. The diversity of O-antigen biosynthesis gene clusters (O-AGCs) provides the primary basis for serotyping. However, little is known about the distribution and diversity of O-AGCs of E. albertii strains. Here, we presented a complete sequence set for the O-AGCs from 52 E. albertii strains and identified seven distinct O-AGCs. Six of these were also found in 15 genomes of E. albertii strains deposited in the public database. Possession of wzy/wzx genes in each O-AGC strongly suggest that O-antigens of E. albertii were synthesized by the Wzx/Wzy-dependent pathway. Furthermore, we performed an O-antigen serotyping scheme for E. albertii based on specific antisera against seven O-antigens and a high throughput xTAG Luminex assay to simultaneously detect seven O-AGCs. Both methods accurately identified serotypes of 64 tested E. albertii strains. Our data revealed the high-level diversity of O-AGCs in E. albertii. We also provide valuable methods to reliably identify and serotype this bacterium.

The Cytolethal Distending Toxin Contributes to Microbial Virulence and Disease Pathogenesis by Acting As a Tri-Perditious Toxin

This review summarizes the current status and recent advances in our understanding of the role that the cytolethal distending toxin (Cdt) plays as a virulence factor in promoting disease by toxin-producing pathogens. A major focus of this review is on the relationship between structure and function of the individual subunits that comprise the AB₂ Cdt holotoxin. In particular, we concentrate on the molecular mechanisms that characterize this toxin and which account for the ability of Cdt to intoxicate multiple cell types by utilizing a ubiquitous binding partner on the cell membrane. Furthermore, we propose a paradigm shift for the molecular mode of action by which the active Cdt subunit, CdtB, is able to block a key signaling cascade and thereby lead to outcomes based upon programming and the role of the phosphatidylinositol 3-kinase (PI-3K) in a variety of cells. Based upon the collective Cdt literature, we now propose that Cdt is a unique and potent virulence factor capable of acting as a tri-perditious toxin that impairs host defenses by: (1) disrupting epithelial barriers; (2) suppressing acquired immunity; (3) promoting pro-inflammatory responses. Thus, Cdt plays a key role in facilitating the early stages of infection and the later stages of disease progression by contributing to persistence and impairing host elimination.