Screening of AmpC-/ESBL-producing Escherichia coli isolates from livestock for STEC/EHEC virulence genes

Livestock is an important reservoir of Shiga toxin-producing Escherichia coli and enterohemorrhagic E. coli (STEC/EHEC) strains and acts as a significant source of transmission to humans. In addition to the virulence of STEC/EHEC isolates, antibiotic resistance is also an escalating problem in these bacteria and increases the risk to public health. Therefore, the present study aimed to explore E. coli O157:H7 serotype and STEC/EHEC virulence genes in AmpC- and extended-spectrum beta-lactamase (ESBL)-producing E. coli isolates from cattle, chicken and sheep. A total of 61 confirmed AmpC- or ESBL-producing E. coli isolates were screened for the virulence genes (stx1, stx2, eae, ehxA, espP, katP and saa) and E. coli O157 (rfbO157) and H7 (fliCH7) genes by polymerase chain reaction (PCR). None of the ESBL-producing E. coli was positive for these genes, but six multidrug-resistant AmpC-producing E. coli were positive for the fliCH7 gene only. When considering the function of the H7 flagellar antigen of E. coli, it may be concluded that the development of ESBL/AmpC beta-lactamase production in the E. coli isolates with H7 flagella, which reside in the chicken intestine, may be potentially important for public health regarding both virulence and antimicrobial resistance.

Epidemiological Study of Salmonella typhi and Its Month-Wise Effect on Different Age Groups in Dehradun

Introduction: Salmonella typhi is a bacterial disease caused by contaminated food and water, also known as foodborne and waterborne infection, it transmitted via faeco-oral route. Materials and Methods: A total of 204 clinical isolates were considered for its proposed study. IgM/IgG rapid card test (CTK Biotech) was used for the detection and Widal test (BEACON) was also performed for the same. Duration: March 2020 to November 2020. Results: A total of 204 blood samples were analyzed with clinically suspected cases of typhoid fever, out of which, some cases showed reactiveness and 50.98% showed negative for Salmonella typhi. Widal test showed reactive result for O Ag (Somatic Antigen) and H Ag (flagellar antigen) and 8.82% IgG and 42.64% (monthly) IgM antibody showed positive result. Conclusion: Typhoid IgM/IgG antibody rapid card test and Widal Antigen test, a simple and rapid method for the detection of Salmonella typhi bacterium in patient’s serum by serological techniques. Maximum number of positive cases were in the month of August, 2020 and September, 2020. The age group between 21-40 years were most infected by Salmonella typhi.

Typhoid fever: a review

Typhoid fever is still a deadly disease in developing countries, particularly in India. Although, the paediatric population is mostly affected by this disease, yet the disease is an important cause of morbidity and mortality in adult populations also. In India, most of the cases of typhoid fever are diagnosed clinically, or at the most by the Widal test which is not fool proof. The disease typhoid fever is an orally transmitted communicable infectious disease caused by the bacteria Salmonella typhi. It is usually caused by consuming impure water and contaminated food. Salmonella typhi is serologically positive for lipopolysaccharide antigens O9 and O12, protein flagellar antigen Hd, and polysaccharide capsular antigen Vi. S. typhi Vi-positive strains are more infectious and virulent than Vi-negative strains. Following the incubation period of 7 to 14 days, there is onset of fever and malaise. The fever is then accompanied by chills, headache, malaise, anorexia, nausea, vague abdominal discomfort, dry cough and myalgia. These are followed by coated tongue, tender abdomen, hepatomegaly, and splenomegaly. Azithromycin (10mg/kg) given once daily for seven days has proven effective in the treatment of typhoid fever in some adults and children. A dose of 1g per day for five days was also found to be more effective in most adults. Of the third generation cephalosporins, oral Cefixime (15-20mg per kg per day, for adults, 100-200mg twice daily) has been widely used. Intravenous third generation cephalosporins (ceftriaxone, cefotaxime) are effective. Aztreonam and imipenem are potential third line drugs.

Study of a Cohort of 1,886 Persons To Determine Changes in Antibody Reactivity to Borrelia burgdorferi 3 Months after a Tick Bite

ABSTRACTLyme borreliosis is a tick-borne disease caused by the bacteriumBorrelia burgdorferi. The most frequent clinical manifestation is a rash called erythema migrans. Changes in antibody reactivity toB. burgdorferi3 months after a tick bite are measured using enzyme-linked immunosorbent assays (ELISAs). One assay is based on native purified flagellum antigen (IgG), and the other assay is based on a recombinant antigen called C6 (IgG or IgM). Paired samples were taken at the time of a tick bite and 3 months later from 1,886 persons in Sweden and the Åland Islands, Finland. The seroconversion or relative change is defined by dividing the measurement units from the second sample by those from the first sample. The threshold for the minimum level of significant change was defined at the 2.5% level to represent the random error level. The thresholds were a 2.7-fold rise for the flagellar IgG assay and a 1.8-fold rise for the C6 assay. Of 1,886 persons, 102/101 (5.4%) had a significant rise in antibody reactivity in the flagellar assay or the C6 assay. Among 40 cases with a diagnosis of Lyme borreliosis, the sensitivities corresponding to a rise in antibodies were 33% and 50% for the flagellar antigen and the C6 antigen, respectively. Graphical methods to display the antibody response and to choose thresholds for a rise in relative antibody reactivity are shown and discussed. In conclusion, 5.4% of people with tick bites showed a rise inBorrelia-specific antibodies above the 2.5% threshold in either ELISA but only 40 (2.1%) developed clinical Lyme borreliosis.

Genetic Diversity of thefliCGenes Encoding the Flagellar Antigen H19 of Escherichia coli and Application to the Specific Identification of Enterohemorrhagic E. coli O121:H19

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) O121:H19 belong to a specific clonal type distinct from other classical EHEC and major enteropathogenicE. coligroups and is regarded as one of the major EHEC serogroups involved in severe infections in humans. Sequencing of thefliCgenes associated with the flagellar antigen H19 (fliCH19) revealed the genetic diversity of thefliCH19gene sequences inE. coli. A cluster analysis of 12fliCH19sequences, 4 from O121 and 8 from non-O121E. colistrains, revealed five different genotypes. All O121:H19 strains fell into one cluster, whereas a second cluster was formed by five non-O121:H19 strains. Cluster 1 and cluster 2 strains differ by 27 single nucleotide exchanges in theirfliCH19genes (98.5% homology). Based on allele discrimination of thefliCH19genes, a real-time PCR test was designed for specific identification of EHEC O121:H19. The O121fliCH19PCR tested negative in 73E. coliH19 strains that belonged to serogroups other than O121, including 28 different O groups, O-nontypeable H19, and O-rough:H19 strains. The O121fliCH19PCR reacted with all 16 tested O121:H19 strains and 1 O-rough:H19 strain which was positive for the O121wzxgene. A cross-reaction was observed only withE. coliH32 strains which share sequence similarities in the target region of the O121fliCH19PCR. The combined use of O-antigen genotyping (O121wzx) and the detection of O121fliCH19allele type contributes to improving the identification and molecular serotyping of EHEC O121:H19 motile and nonmotile strains and variants of these strains lackingstxgenes.

Monophasic expression of FliC by Salmonella 4,[5],12:i:- DT193 does not alter its pathogenicity during infection of porcine intestinal epithelial cells

Non-typhoidal serotypes of Salmonella enterica remain important food-borne pathogens worldwide and the frequent emergence of epidemic strains in food-producing animals is a risk to public health. In recent years, Salmonella 4,[5],12:i:- isolates, expressing only phase 1 (FliC) of the two flagellar antigens, have emerged and increased in prevalence worldwide. In Europe, the majority of 4,[5],12:i:- isolates belong to phage types DT193 and DT120 of Salmonella Typhimurium and pigs have been identified as the reservoir species. In this study we investigated the ability of pig-derived monophasic (4,[5],12:i:-) and biphasic DT193 isolates to invade a porcine intestinal epithelial cell line (IPEC-1) and activate TLR-5, IL-8 and caspases. We found that the 4,[5],12:i:- isolates exhibited comparable adhesion and invasion to that of the virulent S. Typhimurium isolate 4/74, suggesting that these strains could be capable of colonizing the small intestine of pigs in vivo. Infection with 4,[5],12:i:- and biphasic DT193 isolates resulted in approximately the same level of TLR-5 (a flagellin receptor) and IL-8 (a proinflammatory chemokine) mRNA upregulation. The monophasic variants also elicited similar levels of caspase activation and cytotoxicity to the phase-variable DT193 isolates. These findings suggest that failure of 4,[5],12:i:- DT193 isolates to express a second phase of flagellar antigen (FljB) is unlikely to hamper their pathogenicity during colonization of the porcine intestinal tract.