Non-O157:H7 Shiga Toxin Producing Diarrhoeagenic Escherichia coli (STEC) in Southern India: A Tinderbox for Starting Epidemic

Isolation and characterization of a relatively broad-spectrum phage against Escherichia coli

Multiple pathogenic types or serotypes restrict treatment for colibacillosis. In addition, rising antibiotic resistance has heightened public awareness to prevent and control pathogenic Escherichia coli. The bacteriophage is a viable technique to treat colibacillosis as an alternative to antibiotics. In this study, PH444, a relatively broad-spectrum obligate lytic phage, was screened from 48 Shiga toxin-producing Escherichia coli (STEC) phages isolated from farm manure samples and sewage samples in order to conduct genome-wide analysis, biological characterization, and a bacterial challenge experiment in milk. The results demonstrated that PH444 was a T7-like phage with a double-stranded DNA of 115,111 bp that belongs to the Kuravirus and was stable at temperatures between 4 and 50 °C and a pH range of 3 to 11. After adding PH444, the bacterial load in milk could be reduced from 3 × 103 PFU/ mL to zero within 1 h. In consideration of the biological properties of phage PH444, it was, therefore, demonstrated that PH444 has the potential to be used in phage biocontrol.

Isolation and genotypic characterization of extended-spectrum beta-lactamase-producing Escherichia coli O157:H7 and Aeromonas hydrophila from selected freshwater sources in Southwest Nigeria

The proliferation of antibiotic-resistant bacteria and antimicrobial resistance is a pressing public health challenge because of their possible transfer to humans via contact with polluted water sources. In this study, three freshwater resources were assessed for important physicochemical characteristics as well as heterotrophic and coliform bacteria and as potential reservoirs for extended-spectrum beta-lactamase (ESBL) strains. The physicochemical characteristics ranged from 7.0 to 8.3; 25 to 30 °C, 0.4 to 93 mg/L, 0.53 to 8.80 mg/L and 53 to 240 mg/L for pH, temperature, dissolved oxygen (DO), biological oxygen demand (BOD₅) and total dissolved solids, respectively. The physicochemical characteristics mostly align with guidelines except for the DO and BOD₅ in some instances. Seventy-six (76) Aeromonas hydrophila and 65 Escherichia coli O157: H7 isolates were identified by preliminary biochemical analysis and PCR from the three sites. Among these, A. hydrophila displayed higher frequencies of antimicrobial resistance, with all 76 (100%) isolates completely resistant to cefuroxime and cefotaxime and with MARI ≥ 0.61. The test isolates showed more than 80% resistance against five of the ten test antimicrobials, with resistance against cefixime, a cephalosporin antibiotic being the highest at 95% (134/141). The frequency of the detection of the resistance genes in the A. hydrophila isolates generally ranged between 0% (bla_SHV) and 26.3% (bla_CTX-M), while the frequency of detection among the E. coli O157:H7 isolates ranged between 4.6% (bla_CTX-M) and 58.4% (bla_TEM). Our findings indicate that the distribution of antibiotic-resistant bacteria with diverse ESBL-producing capabilities and virulence genes in freshwater sources potentially threatens public health and the environment.

Determination of the changes in the gastric fluid endurance of O157 and non-O157 Shiga toxin-producing Escherichia coli during storage of experimentally produced beef frankfurter

Resistance of Shiga toxin-producing Escherichia coli (STEC) O157:H7 and serogroups O103, O26 and O145 to synthetic gastric fluid (SGF, pH 1.5) were investigated during frankfurter storage. Pathogens were inoculated (5 ± 1 log₁₀ cfu g^-1) on frankfurters and frankfurters were stored at 4 °C for 75 days in vacuum packages. Population changes of the competitive flora and STEC, changes in the pH of the frankfurters and resistance of STEC to SGF were monitored on days 0, 15, 30, 45, 60 and 75 of frankfurter storage. Direct synthetic gastric fluid (DSGF) challenges were also conducted to assess pathogen resistance without being effected by frankfurters, by inoculating pathogen cultures directly into SGF. Results showed that acid resistance of O145 and O26 was stronger than that of O103 and O157 during frankfurter storage. Resistance of O103 to SGF was better than that of O157 during frankfurter storage but, was similar to that of O157 during DSGF challenges. Results indicate that acid resistance of some strains of STEC pathogens might differentiate during storage of frankfurters. Different resistance capabilities to SGF were observed in the STEC strains when inoculated and stored on frankfurters than directly inoculated in the SGF.

Shiga toxin producing Escherichia coli-associated diarrhea and hemolytic uremic syndrome in young children in Romania

Background

Diarrheagenic Escherichia coli (E. coli) is an important cause of diarrheal diseases in both developing countries and industrialized countries. An outbreak of hemolytic uremic syndrome (HUS) in young children from southern Romania was reported in early 2016 and was attributed to Shiga toxin producing E. coli (STEC) O26 infection. The aim of this study was to determine the prevalence, demographic and clinical characteristics of STEC infections in children hospitalized with diarrhea in Brașov in the central region of Romania. We also described the occurrence of HUS among hospitalized children, close in time to the 2016 HUS outbreak in southern Romania.

Methods

A prospective study was conducted between March and December 2016 among 722 children aged 1–30 months hospitalized with acute diarrhea. Stool samples obtained from patients with diarrhea were tested for the presence of Shiga toxin type 1 (STX1) and type 2 (STX2) by an immunochromatographic assay, and other enteropathogens. Demographic and clinical information on cases of HUS diagnosed in the same hospital was obtained from medical records.

Results

Overall 46/722 (6.4%) children (mean age 10.3 months, 32.6% females) hospitalized with diarrhea tested positive for STX1 or STX2; of these 79% were positive for both STX1 and STX2, 16% for STX2 only, and 5% for STX1 only. Bloody diarrhea, vomiting and fever were documented in 32.6%, 52.1% and 50.0%, respectively of patients with STEC infection. Eleven confirmed HUS cases (mean age 20 months, five females) were identified between 2014 and 2016 with prodromal diarrhea reported in 10 of them. Three of the 11 HUS patients required hemodialysis.

Conclusions

STEC prevalence among young children with diarrhea in Romania was high and the risk of HUS is emerging. The establishment of a systematic laboratory-based surveillance program including identification of the circulating STEC strains coupled with epidemiological investigation of HUS patients is warranted to determine the source and mode of transmission of STEC and prevent of STEC-associated diarrhea and HUS.

Hemolytic uremic syndrome in a developing country: Consensus guidelines

BACKGROUND

Hemolytic uremic syndrome (HUS) is a leading cause of acute kidney injury in children. Although international guidelines emphasize comprehensive evaluation and treatment with eculizumab, access to diagnostic and therapeutic facilities is limited in most developing countries. The burden of Shiga toxin-associated HUS in India is unclear; school-going children show high prevalence of anti-factor H (FH) antibodies. The aim of the consensus meeting was to formulate guidelines for the diagnosis and management of HUS in children, specific to the needs of the country.

METHODS

Four workgroups performed literature review and graded research studies addressing (i) investigations, biopsy, genetics, and differential diagnosis; (ii) Shiga toxin, pneumococcal, and infection-associated HUS; (iii) atypical HUS; and (iv) complement blockade. Consensus statements developed by the workgroups were discussed during a consensus meeting in March 2017.

RESULTS

An algorithm for classification and evaluation was developed. The management of Shiga toxin-associated HUS is supportive; prompt plasma exchanges (PEX) is the chief therapy in patients with atypical HUS. Experts recommend that patients with anti-FH-associated HUS be managed with a combination of PEX and immunosuppressive medications. Indications for eculizumab include incomplete remission with plasma therapy, life-threatening features, complications of PEX or vascular access, inherited defects in complement regulation, and recurrence of HUS in allografts. Priorities for capacity building in regional and national laboratories are highlighted.

CONCLUSIONS

Limited diagnostic capabilities and lack of access to eculizumab prevent the implementation of international guidelines for HUS in most developing countries. We propose practice guidelines for India, which will perhaps be applicable to other developing countries.