A One Health Perspective for Defining and Deciphering Escherichia coli Pathogenic Potential in Multiple Hosts

Polyclonal carbapenemase-producing Escherichia coli in Northern Italy: the emergence of NDM-7

The spread of extended-spectrum beta-lactamase (ESBL)- and carbapenemase-producing Escherichia coli clones in humans, animals, and the environment is of great concern worldwide. In this study, we characterized four carbapenemase-producing E. coli (CP-Ec) isolated from human samples. Two isolates of ST401, rarely associated with carbapenemase and/or ESBL resistance genes, harbored blaKPC-3 and blaVIM-1 genes, respectively, and were genetically distant from each other. One CP-Ec isolate belonging to ST355, typically found in poultry and environmental sources and not associated with carbapenemases, was blaKPC-3 positive and showed a wide range of virulence genes. The last CP-Ec strain belonged to ST3564, previously described in livestock with a large virulome but no carbapenemase. The CP-Ec ST3564 isolate co-harbored blaVIM-1 and blaNDM-7 genes, which, to our knowledge, have not been previously reported in Italy. These results emphasize the crucial role of a genomic-based surveillance program to intercept the emergence of critical E. coli clones.

Degradation of plasmid-mediated resistance genes in poultry slaughterhouse wastewater employing a UV/H2O2 process: A metagenomic approach

Poultry slaughterhouse effluents are important hotspots for the spread of both antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs), contributing to the antimicrobial resistance (AMR). This study reports a novel investigation to assess the effects of UV/H2O2 treatment on the removal of metaplasmidome-mediated ARGs from poultry slaughterhouse effluents. The effluent samples were subjected at 0.005-0.15 mol L-1 of H2O2 and pH conditions (3, 5, 7 and 9). Bacterial community (rrs 16S rRNA), Escherichia coli (uidA) antimicrobial resistance (sul1 and int1) and metagenomic plasmid DNA removal were assessed. The UV/H2O2 treatment employing H2O2 = 0.01 mol L-1 at pH 3 resulted in decreased of several markers (uidA, sul1 and int1). A metaplasmidome indicated the persistence of Burkholderiales order. The UV/H2O2 process reduced plasmid-associated ARGs by 92.5% and 90.4% at pH 3 and 7, respectively. Persistent genes were mainly composed of genes associated with efflux pumps and resistance to beta-lactams and fluoroquinolones. These findings contribute to mitigate the spread of AMR in the agricultural sector, especially through the implementation of more efficient treatments, and reducing the use of antibiotics in livestock farming.

Recombinant Saccharomyces cerevisiae EBY100/pYD1-FaeG: a candidate for an oral subunit vaccine against F4+ ETEC infection

Diarrheal diseases attributable to multidrug-resistant F4+ enterotoxigenic Escherichia coli (ETEC) are escalating in severity, posing significant risks to the health and safety of both humans and animals. This study used Saccharomyces cerevisiae EBY100 to display the FaeG subunit of F4 colonizing factor as an oral vaccine against F4+ ETEC infection. Mice were orally immunized twice with 108 CFU of EBY100/pYD1-FaeG, followed by a challenge with F4+ ETEC EC6 on day 7 post-immunization. The results showed that the recombinant strain EBY100/pYD1-FaeG orally enhanced the growth of the small intestine villi, significantly boosted the expression of tight junction proteins (ZO-1, Occludin, MUC2, and Claudin) (P < 0.05), and modulated the gut microbiota composition. Additionally, immunization with EBY100/pYD1-FaeG also upregulated the levels of IL-2, IL-4, and IFN-γ in the intestines of mice (P < 0.01), while serum IgG and fecal sIgA titer significantly increased (P < 0.05). These immune responses enhanced the capacity to fight against ETEC, leading to an increased survival rate of mice and relieved damage to tissues and organs of mice infection. In summary, the study suggested that the recombinant Saccharomyces cerevisiae EBY100/pYD1-FaeG could effectively stimulate the immune response and generate specific antibodies against F4+ ETEC, showing its potential to serve as a subunit oral vaccine candidate for preventing F4+ ETEC infection.IMPORTANCEThe multidrug-resistant F4+ enterotoxigenic Escherichia coli (ETEC) strains are the primary clinical pathogens responsible for post-weaning diarrhea in piglets, resulting in substantial economic losses in the pig farming industry. In the study, we developed an oral vaccine candidate, Saccharomyces cerevisiae EBY100/pYD1-FaeG, to prevent diarrhea caused by multidrug-resistant F4+ ETEC. Oral administration of EBY100/pYD1-FaeG significantly enhanced immune responses, improved intestinal health, and provided protection against F4+ ETEC infection in mice. This approach offers a potential application prospect for preventing F4+ ETEC infections that lead to post-weaning diarrhea in clinical settings and provides a promising solution for addressing the growing threat of antibiotic resistance in bacterial pathogens.

Prevalent and Drug-Resistant Phenotypes and Genotypes of Escherichia coli Isolated from Healthy Cow's Milk of Large-Scale Dairy Farms in China

Escherichia coli is a common cause of mastitis in dairy cows, which results in large economic losses to the livestock industry. The aim of this study was to investigate the prevalence of E. coli in raw milk in China, assess antimicrobial drug susceptibility, and identify key antibiotic resistance genes carried by the isolates. In total, 350 raw milk samples were collected from large-scale farms in 16 provinces and cities in six regions of China to assess the resistance of E. coli isolates to 14 antimicrobial drugs. Among the isolates, nine resistance genes were detected. Of 81 E. coli isolates (23.1%) from 350 raw milk samples, 27 (33.3%) were multidrug resistant. Antimicrobial susceptibility testing showed that the 81 E. coli isolates were resistant to 13 (92.9%) of the 14 antibiotics, but not meropenem. The resistance gene blaTEM was highly distributed among the 27 multidrug-resistant isolates with a detection rate of 92.6%. All isolates carried at least one resistance gene, and 19 patterns of resistance gene combinations with different numbers of genes were identified. The most common gene combinations were the one-gene pattern blaTEM and the three-gene pattern blaTEM-blaPSE-blaOXA. The isolation rate of E. coli in raw milk and the identified resistance genes provide a theoretical basis for the rational use of antibiotics by clinical veterinarians.

Genomic characterization of Escherichia coli with a polyketide synthase (pks) island isolated from ulcerative colitis patients

The E. coli strains harboring the polyketide synthase (pks) island encode the genotoxin colibactin, a secondary metabolite reported to have severe implications for human health and for the progression of colorectal cancer. The present study involves whole-genome-wide comparison and phylogenetic analysis of pks harboring E. coli isolates to gain insight into the distribution and evolution of these organisms. Fifteen E. coli strains isolated from patients with ulcerative colitis (UC) were sequenced, 13 of which harbored pks islands. In addition, 2,654 genomes from the public database were also screened for pks harboring E. coli genomes, 158 of which were pks-positive (pks+) isolates. Whole-genome-wide comparison and phylogenetic analysis revealed that 171 (158 + 13) pks+ isolates belonged to phylogroup B2, and most of the isolates belong to sequence types ST73 and ST95. One isolate from a UC patient was of the sequence type ST8303. The maximum likelihood tree based on the core genome of pks+ isolates revealed horizontal gene transfer across sequence types and serotypes. Virulome and resistome analyses revealed the0020preponderance of virulence genes and a reduced number of antimicrobial genes in pks+ isolates. This study significantly contributes to understanding the evolution of pks islands in E. coli.

Metagenomic insights into plasmid-mediated antimicrobial resistance in poultry slaughterhouse wastewater: antibiotics occurrence and genetic markers

Slaughterhouse wastewater represents important convergence and concentration points for antimicrobial residues, bacteria, and antibiotic resistance genes (ARG), which can promote antimicrobial resistance propagation in different environmental compartments. This study reports the assessment of the metaplasmidome-associated resistome in poultry slaughterhouse wastewater treated by biological processes, employing metagenomic sequencing. Antimicrobial residues from a wastewater treatment plant (WWTP) that treats poultry slaughterhouse influents and effluents were investigated through high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). Residues from the macrolide, sulfonamide, and fluoroquinolone classes were detected, the latter two persisting after the wastewater treatment. The genetic markers 16S rRNA rrs (bacterial community) and uidA (Escherichia coli) were investigated by RT-qPCR and the sul1 and int1 genes by qPCR. After treatment, the 16S rRNA rrs, uidA, sul1, and int1 markers exhibited reductions of 0.67, 1.07, 1.28, and 0.79 genes copies, respectively, with no statistical significance (p > 0.05). The plasmidome-focused metagenomics sequences (MiSeq platform (Illumina®)) revealed more than 100 ARG in the WWTP influent, which can potentially confer resistance to 14 pharmacological classes relevant in the human and veterinary clinical contexts, in which the qnr gene (resistance to fluoroquinolones) was the most prevalent. Only 7.8% of ARG were reduced after wastewater treatment, and the remaining 92.2% were associated with an increase in the prevalence of ARG linked to multidrug efflux pumps, substrate-specific for certain classes of antibiotics, or broad resistance to multiple medications. These data demonstrate that wastewater from poultry slaughterhouses plays a crucial role as an ARG reservoir and in the spread of AMR into the environment.

Trends in the Prevalence of Antimicrobial Resistance in Escherichia coli Isolated from Outpatient Urine Cultures in French Amazonia

Antimicrobial resistance (AMR) in the community is increasing worldwide. We aimed to assess AMR trends in Escherichia coli from the community urine isolates in French Amazonia. We conducted a retrospective study from January 2016 to December 2022 in the Cayenne General Hospital microbiology laboratory (French Guiana). It included all urine samples positive for E. coli collected from adult outpatients. During the study period, 3,443 urinalyses positive for E. coli were studied. In 46% of cases, patients were women. In 64.4% of cases, E. coli were β-lactamase producers. The most frequently diagnosed resistance mechanisms were penicillinase production and sparing third-generation cephalosporins. Isolated E. coli were extended-spectrum β-lactamase (ESBL) producers in 6.1% of cases. Overall, E. coli was susceptible to amoxicillin in 35.9% [95% CI: 34.3-37.5], to amoxicillin/clavulanic acid in 62.2% [95% CI: 60.6-63.9], to cefotaxime in 94% [95% CI: 93.1-94.7], to gentamicin in 92.1% [95% CI: 89.1-92.6], to ofloxacin in 76.8% [95% CI: 75.3-78.2], to trimethoprim/sulfamethoxazole (SXT) in 58.8% [95% CI: 57.1-60.5], to fosfomycin in 99.1% [95% CI: 98.6-99.4], and to nitrofurantoin in 99% of cases [95% CI: 98.6-99.3]. We have observed a gradual decline in the susceptibility profile of E. coli for amoxicillin/clavulanic acid (P <0.001), piperacillin/tazobactam (P = 0.003), and temocillin (P = 0.006). However, susceptibility to ciprofloxacin was increasing (P = 0.001). In contrast, the susceptibility trends for amoxicillin, third-generation cephalosporins, gentamicin, SXT, nitrofurantoin, and fosfomycin remained stable over the 28 quarters of the study. In conclusion, isolated E. coli from outpatient urinalyses showed increased resistance profiles involving penicillinase and ESBL production. Close monitoring and strategies to decrease antibiotic consumption in the community are needed.

Escherichia coli Activate Extraintestinal Antibody Response and Provide Anti-Infective Immunity

The effects of intestinal microflora on extraintestinal immune response by intestinal cytokines and metabolites have been documented, but whether intestinal microbes stimulate serum antibody generation is unknown. Here, serum antibodies against 69 outer membrane proteins of Escherichia coli, a dominant bacterium in the human intestine, are detected in 141 healthy individuals of varying ages. Antibodies against E. coli outer membrane proteins are determined in all serum samples tested, and frequencies of antibodies to five outer membrane proteins (OmpA, OmpX, TsX, HlpA, and FepA) are close to 100%. Serum antibodies against E. coli outer membrane proteins are further validated by Western blot and bacterial pull-down. Moreover, the present study shows that OstA, HlpA, Tsx, NlpB, OmpC, YfcU, and OmpA provide specific immune protection against pathogenic E. coli, while HlpA and OmpA also exhibit cross-protection against Staphylococcus aureus infection. These finding indicate that intestinal E. coli activate extraintestinal antibody responses and provide anti-infective immunity.

Genomic characterization of Escherichia coli harbor a polyketide synthase ( pks ) island associated with colorectal cancer (CRC) development

The E. coli strain harboring the polyketide synthase ( Pks) island encodes the genotoxin colibactin, a secondary metabolite reported to have severe implications for human health and for the progression of colorectal cancer. The present study involved whole-genome-wide comparison and phylogenetic analysis of pks harboring E. coli isolates to gain insight into the distribution and evolution of these organism. Fifteen E. coli strains isolated from patients with ulcerative colitis were sequenced, 13 of which harbored pks islands. In addition, 2,654 genomes from the public database were also screened for pks harboring E. coli genomes, 158 of which were pks -positive isolates. Whole-genome-wide comparison and phylogenetic analysis revealed that 171 (158+13) pks -positive isolates belonged to phylogroup B2, and most of the isolates associated to sequence types ST73 and ST95. One isolate from an ulcerative colitis (UC) patient was of the sequence type ST8303. The maximum likelihood tree based on the core genome of pks -positive isolates revealed horizontal gene transfer across sequence types and serotypes. Virulome and resistome analyses revealed the preponderance of virulence genes and a reduced number of antimicrobial genes in Pks -positive isolates. This study strongly contributes to understanding the evolution of pks islands in E. coli .

Colonization factors of human and animal-specific enterotoxigenic Escherichia coli (ETEC)

Colonization factors (CFs) are major virulence factors of enterotoxigenic Escherichia coli (ETEC). This pathogen is among the most common causes of bacterial diarrhea in children in low- and middle-income countries, travelers, and livestock. CFs are major candidate antigens in vaccines under development as preventive measures against ETEC infections in humans and livestock. Recent molecular studies have indicated that newly identified CFs on human ETEC are closely related to animal ETEC CFs. Increased knowledge of pathogenic mechanisms, immunogenicity, regulation, and expression of ETEC CFs, as well as the possible spread of animal ETEC to humans, may facilitate the future development of ETEC vaccines for humans and animals. Here, we present an updated review of CFs in ETEC.

Multidrug resistance in pathogenic Escherichia coli isolates from urinary tract infections in dogs, Spain

Escherichia coli (E. coli) is a pathogen frequently isolated in cases of urinary tract infections (UTIs) in both humans and dogs and evidence exists that dogs are reservoirs for human infections. In addition, E. coli is associated to increasing antimicrobial resistance rates. This study focuses on the analysis of antimicrobial resistance and the presence of selected virulence genes in E. coli isolates from a Spanish dog population suffering from UTI. This collection of isolates showed an extremely high level of phenotypic resistance to 1st-3rd generation cephalosporins, followed by penicillins, fluoroquinolones and amphenicols. Apart from that, 13.46% of them were considered extended-spectrum beta-lactamase producers. An alarmingly high percentage (71.15%) of multidrug resistant isolates were also detected. There was a good correlation between the antimicrobial resistance genes found and the phenotypic resistance expressed. Most of the isolates were classified as extraintestinal pathogenic E. coli, and two others harbored virulence factors related to diarrheagenic pathotypes. A significant relationship between low antibiotic resistance and high virulence factor carriage was found, but the mechanisms behind it are still poorly understood. The detection of high antimicrobial resistance rates to first-choice treatments highlights the need of constant antimicrobial resistance surveillance, as well as continuous revision of therapeutic guidelines for canine UTI to adapt them to changes in antimicrobial resistance patterns.

Molecular Characterization of Hetero-Pathogenic and Diarrheagenic Escherichia coli Pathotypes in Diarrheic Children under Five Years and Exposure Environment in Ogun State, South-West Nigeria

BACKGROUND

Diarrheagenic Escherichia coli (DEC) is one of the most common etiological agents of moderate-to-severe diarrhea in Low- and Middle-Income Countries (LMICs). Therefore, determining the source(s) of DEC in index cases and exposure environment is important for developing a prevention strategy. The current study aims to investigate the prevalence of DEC among children under 5 years and their exposure environment in Ogun State, Nigeria.

METHODS

Samples from 228 diarrheic children and their exposure environment were collected and screened for E. coli. Bio-chemically compatible distinct colonies were molecularly characterized using a 7-virulence-gene multiplex PCR with virulence factors (VFs) indicative of four pathotypes of E. coli: enterotoxigenic (ETEC), verotoxigenic (VTEC), enteropathogenic (EPEC), and enteroinvasive (EIEC). Representative pathotypes were subjected to antimicrobial susceptibility and over-expressed efflux pump assays.

RESULTS

One or more VFs typical of specific pathotypes were detected in 25.9% (59/228) diarrhea cases consisting of ETEC (21.5%) and EPEC (0.4%), while hetero-pathogenic pathotypes were found in 4.0% of cases. Of the food sources, 27.9% (101/362) were positive for DEC, of which ETEC accounted for 21.0%, VTEC 1.9%, EPEC 0.6%, EIEC 0.6%, and hetero-pathogenic pathotypes were 3.9%. Furthermore, ETEC was the only pathotype detected in the wastewater (4/183). Interestingly, the consumption of street-vended foods was the most significant (p = 0.04) risk factor for DEC infection in the study area. A total of 73.3% of selected DEC pathotypes showed resistance to antimicrobials, while 27.5% demonstrated over-expression of efflux pump activity.

CONCLUSION

The high prevalence of ETEC across all sources and the occurrence of hetero-pathogenic DEC in diarrheic children and food sources emphasizes the importance of establishing a better strategy for the control and prevention of diarrhea among children in low- and medium-income households.

Improving the biocompatibility and antibacterial efficacy of silver nanoparticles functionalized with (LLRR)3 antimicrobial peptide

The selection of effective antibiotics is becoming increasingly limited due to the emergence of bacterial resistance. Designing and developing nanoscale antibacterials is a strategy for effectively addressing the antibiotic crisis. In this work, AgNPs@AMP nanoparticles were synthesized to take advantage of the synergistic antibacterial activity of the (LLRR)3 antimicrobial peptide (AMP) and silver nanoparticles (AgNPs). Based on morphological structure characterization and biocompatibility analysis, the inhibitory properties of AgNPs@AMP on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were evaluated. The results demonstrated that AMP and AgNPs were physically bound to form AgNPs@AMP nanoparticles, which had better solution stability, improved nanomaterial properties, and overcame the hemolytic activity of AMP and the cytotoxicity of AgNPs. The inhibitory activity of AgNPs@AMP against E. coli and S. aureus was significantly higher than that of AMP and AgNPs. It was capable of disrupting the morphology and internal structure of cells, damaging the cell membrane, and inhibiting the activity of enzymes related to the material-energy metabolism of the tricarboxylic acid cycle. Compared to AMP and AgNPs, AgNPs@AMP were found to effectively inhibit the infection of mouse wounds and promote their healing. Therefore, AMP-modified AgNPs can enhance their biocompatibility and antibacterial activity, and they can be further developed as a potential antimicrobial agent.

Recent Advances in Monoclonal Antibody-Based Approaches in the Management of Bacterial Sepsis

Sepsis is a life-threatening condition characterized by an uncontrolled inflammatory response to an infectious agent and its antigens. Immune cell activation against the antigens causes severe distress that mediates a strong inflammatory response in vital organs. Sepsis is responsible for a high rate of morbidity and mortality in immunosuppressed patients. Monoclonal antibody (mAb)-based therapeutic strategies are now being explored as a viable therapy option for severe sepsis and septic shock. Monoclonal antibodies may provide benefits through two major strategies: (a) monoclonal antibodies targeting the pathogen and its components, and (b) mAbs targeting inflammatory signaling may directly suppress the production of inflammatory mediators. The major focus of mAb therapies has been bacterial endotoxin (lipopolysaccharide), although other surface antigens are also being investigated for mAb therapy. Several promising candidates for mAbs are undergoing clinical trials at present. Despite several failures and the investigation of novel targets, mAb therapy provides a glimmer of hope for the treatment of severe bacterial sepsis and septic shock. In this review, mAb candidates, their efficacy against controlling infection, with special emphasis on potential roadblocks, and prospects are discussed.

Comparative Characteristics and Pathogenic Potential of Escherichia coli Isolates Originating from Poultry Farms, Retail Meat, and Human Urinary Tract Infection

The pathogenicity of many bacterial strains is determined by the acquisition of virulence genes and depends on many factors. The aim of this study was to analyse the phylogenetic background, virulence patterns, and drug susceptibility of 132 E. coli isolates tested in the context of the ExPEC (Extraintestinal Pathogenic E. coli) pathotype and the correlation of these features with bacterial isolation source: food (retail meat), poultry farms (AFEC—Avian Faecal E. coli), and patients with UTI (urinary tract infection) symptoms. The drug-susceptibility results of tested E. coli isolates obtained indicate that the resistance profile—ampicillin/tetracycline/trimethoprim+sulfamethoxazole/ciprofloxacin (AMP/TE/SXT/CIP)—was most frequently observed. The multidrug resistance (MDR) phenotype was found in 31.8% of isolates from poultry farms, 36.8% of strains isolated from food, and 20% of clinical samples. The greatest similarity of virulence profiles applied to isolates derived from poultry farms and food. Most of the AFEC from poultry farms and food-derived isolates belonged to commensals from phylogroups A and B1, while among the isolates from patients with UTI symptoms, the most common was the B2 phylogroup. The collective analysis showed similarity of the three studied groups of E. coli isolates in terms of the presented patterns of antimicrobial resistance, while the virulence profiles of the isolates studied showed great diversity. The phylogroup analysis showed no similarity between the poultry/food isolates and the UTI isolates, which had significant pathogenic potential.

Virulence Profiles and Antibiotic Susceptibility of Escherichia coli Strains from Pet Reptiles

Exotic reptiles are increasingly being bred as pets in many countries around the world, including Poland. However, the close contact between reptiles and their owners provides favourable conditions for the transmission of zoonotic pathogens. In this work, we examined E. coli isolates from 67 captive reptiles regarding their virulence, antibiotic susceptibility, phylogenetic affiliation, and genetic diversity. The incidence of E. coli was highest in snakes (51.6%, 16 isolates/31 samples), and slightly lower in turtles (44.4%, 8/18) and lizards (44.4%, 8/18). Genes encoding virulence factors were confirmed in 50% of isolates and the most common were the traT (37.5%, n = 12), fyuA (21.87%, n = 7), and irp-2 (15.62%, n = 5). The majority (71.87%, n = 23) of E. coli isolates were susceptible to all of the antimicrobial substances used in the study. Streptomycin resistance (21.87%, n = 7) was the most frequent, while resistance to other antimicrobial substances was sporadic. One strain (3.12%) was classified as multidrug-resistant. The presence of resistance genes (aadA, tetA, tetB, tetM, and blaTEM) was confirmed in 12.5% (n = 4) of the isolates. The majority (65.6%, n = 21) of E. coli isolates represented the B1 phylogenetic group. (GTG)₅-PCR fingerprinting showed considerable genetic variation in the pool of tested isolates. The frequency of E. coli in reptiles is much lower than in mammals or birds. Due to the presence of virulence genes, characteristic of both intestinal pathogenic E. coli (IPEC) and extraintestinal pathogenic E. coli (ExPEC), reptilian strains of E. coli have pathogenic potential, and therefore people in contact with these animals should follow good hygiene practices.

Evaluation of PLGA-Encapsulated Recombinant GroEL of S. typhi immune Responses Against Enterohaemorrhagic and Enteropathogenic Escherichia coli

Background

Heat Shock Proteins (HSPs) elicit humoral and cellular immune responses. Due to their high sequence homology, they can be developed as a new immunogen for cross prophylactic and vaccination effects against infectious agents such as Enteropathogenic and Enterohemorrhagic Escherichia coli (EPEC and EHEC). This study aimed to evaluate the immunogenicity and cross-protective efficacy of rGroEL of Salmonella typhi (S. typhi) encapsulated in poly lactic-co-glycolic acid (PLGA) nanoparticles against EPEC and EHEC.

Methods

Recombinant GroEL was expressed in Escherichia coli (E. coli) and purified using Ni-NTA affinity chromatography. The protein was encapsulated in PLGA by the double emulsion method, and the nanoparticles were characterized physicochemically. BALB/c mice were immunized, and the efficacy of the protein to elicit immune responses was assessed.

Results

Over-expression in E. coli led to corresponding 64.5 kDa protein bands in Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE). Non-aggregated nanoparticles had a spherical shape with a mean diameter of 194.3±3 nm and encapsulation efficiency of 89.5±2.5%. Antibody isotyping revealed that GroEL immunization induced both IgG1 and IgG2a antibodies. Moreover, immunization of the mice with recombinant GroEL protein conferred 80 and 60% protection against lethal infections by EPEC and EHEC, respectively. Furthermore, organ burden studies revealed a significant reduction in infection in the immunized mice compared to the non-immunized ones. Passive immunization with anti-GroEL sera also protected 50% of the mice against the lethal doses of EHEC and EPEC strains.

Conclusion

The findings indicated that immunization of the mice with recombinant GroEL of S. typhi elicited cross-protection against other bacterial infections. This represented the immense potential of GroEL to be developed as a single vaccine against multiple pathogens.