Enterica Serovar Typhi Research Articles

Identification of Crp as a novel regulator of the Std fimbrial expression in Salmonella.

The Salmonella enterica serovar Typhi genome contains 14 putative fimbrial systems. The Std fimbriae belong to the chaperone-usher family and its regulation has not been investigated in S. Typhi. Several regulators of Std were previously identified in the closely related serovar Typhimurium. We hypothesize that regulators of S. Typhimurium may be shared with S. Typhi, but that several other regulators remain to be discovered. Here, we describe the role of more than 50 different candidate regulators on std expression. Three types of regulators were investigated: known regulators in S. Typhimurium, in silico predicted regulators and virulence/metabolic regulators. Expression of std was determined in the regulator mutants and compared with the wild-type strain. Overall, 21 regulator mutations affect std promoter expression. The role of Crp, a newly identified factor for std expression, was further investigated. Crp acted as an activator of std expression on a distal region of the std promoter region. Together, our results demonstrate the major influence of Crp as a novel transcriptional factor on std promoter expression and later production of Std fimbriae in Salmonella.

The low level of O antigen in Salmonella enterica Paratyphi A is due to inefficiency of the glycosyltransferase WbaV.

The group A O antigen is the major surface polysaccharide of Salmonella enterica serovar Paratyphi A (SPA), and the focal point for most current vaccine development efforts. The SPA O-antigen repeat (O unit) is structurally similar to the group D1 O unit of S. enterica serovar Typhi, differing only in the presence of a terminal side-branch paratose (Par) in place of tyvelose (Tyv), both of which are attached by the glycosyltransferase WbaV. The two O-antigen gene clusters are also highly similar, but with a loss-of-function mutation in the group A tyv gene and the tandem amplification of wbaV in most SPA strains. In this study, we show that SPA strains consistently produce less O antigen than their group D1 counterparts and use an artificial group A strain (D1 Δtyv) to show this is due to inefficient Par attachment by WbaV. We also demonstrate that group A O-antigen production can be increased by overexpression of the wbaV gene in both the D1 Δtyv strain and two multi-wbaV SPA strains. These findings should be broadly applicable in ongoing vaccine development pipelines, where efficient isolation and purification of large quantities of O antigen is of critical importance.

Prevalence of Salmonella enterica serovar Typhi infection, its associated factors and antimicrobial susceptibility patterns among febrile patients at Adare general hospital, Hawassa, southern Ethiopia

BackgroundSalmonellas enterica serovar Typhi (S.typhi) causes typhoid fever and is a global health problem, especially in developing countries like Ethiopia. But there is a little information about prevalence and factors association with S.typhi and its antimicrobial susceptibility pattern in Ethiopia especially in the study area.The aim of this study was to determine the prevalence of S.typhi infection, its associated factors and antimicrobial susceptibility pattern among patient with a febrile illness at Adare General Hospital, Hawassa, Southern Ethiopia.MethodsHospital based cross sectional study was conducted among 422 febrile patients from May 23, 2018 to October 20, 2018. A 5 ml venous blood was collected from each febrile patient. Culture and biochemical test were performed for each isolate. Antimicrobial susceptibility testing was performed for each isolate using modified Kirby-Bauer disk diffusion techniques.ResultIn this study, the prevalence of S.typhi among febrile illness patients at Adare General Hospital was 1.6% [95% confidence interval (CI): 0.5–2.9]. The age of the study subjects were ranged from 15 to 65 years (mean age 32 years). It was observed that participants who came from rural area had 8 times (AOR 8.27: 95% CI: 1.33, 51.55) more likely to had S. typhi infection when compared with urban dwellers. The microbial susceptibility testing revealed that all six of S.typhi isolates showed sensitive to Ceftriaxone and all 6 isolates showed resistant to nalidixic acid and Cefotaxime and 5(83.3%) susceptible to Chloramphenicol and Ciprofloxaciline. Multidrug resistance (resistance to three or more antibiotics) was observed among most of the isolates.ConclusionS. typhi bacteraemia is an uncommon but important cause of febrile illness in our study population. Ceftriaxone therapy is a suitable empirical antibiotic for those that are unwell and suspected of having this illness. Further surveillance is required to monitor possible hanging antibiotic resistant patterns in Ethiopia.

Isolation and characterization of antisalmonellal anthraquinones and coumarins from Morinda lucida Benth. (Rubiaceae)

A new anthraquinone, 1,6-dihydroxy-2-hydroxymethyl-5-methoxy-9,10-anthracenedione (1), along with four known compounds, including 1,2-dimethoxyanthraquinone (2), morindone-5-methylether (3), scopoletin (4), and fraxidin (5) were isolated from the methylene chloride extract of the stem bark of Morinda lucida Benth. Structure elucidation was accomplished by analysis of the 1D and 2D NMR, IR and mass spectra. Compounds 1, 2, 4 and 5 were tested against five Salmonella strains. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) were determined. The results indicated that the four compounds have different antibacterial activities, with MIC values ranging from 8 to 256 µg/mL. Among these four compounds, the best activity was observed for compound 4 against Salmonella enterica subsp. enterica serovar Typhimurim (STM), with a MIC value of 8 µg/mL. Compound 1 showed selective antibacterial activity toward the five Salmonella strains, with MICs of 16 µg/mL against STM, 32 µg/mL against S. enteritidis (STE), 64 µg/mL against S. enterica subsp. enterica serovar Typhi (ST) and S. enterica subsp. enterica serovar Typhi (ST566), and 128 µg/mL against S. enteritidis, S. enterica subsp. enterica serovar Typhi ATCC 6539 (STS). Compounds 1, 2, 4, and 5 have bactericidal effects (MBC/MIC ≤ 4) against the tested Salmonella strains, except for compound 4, which is bacteriostatic to STM with a MBC/MIC value of 16.

SopA inactivation or reduced expression is selected in intracellular Salmonella and contributes to systemic Salmonella infection

Pseudogenes are accumulated in host-restricted Salmonella enterica serovars, while pseudogenization is primarily regarded as a process that purges unnecessary genes from the genome. Here we showed that the inactivation of sopA, which encodes an effector of Salmonella Pathogenicity Island 1, in human-restricted S. enterica serovar Typhi (S. Ty) and Paratyphi A (S. PA) is under positive selection and aimed to reduce bacterial cytotoxicity toward host macrophages. Moreover, we found that the expression of sopA in Salmonella Typhimurium (S. Tm), a broad-host-range serovar which causes systemic disease in mice, was negatively regulated during mice infection and survival in murine macrophages. The sopA repression in S. Tm is mediated by IsrM, a small RNA absent from the genome of S. Ty and S. PA. Due to the lack of IsrM, sopA expression was unregulated in S. Ty and S. PA, which might have facilitated the convergent inactivation of sopA in these two serovars. In conclusion, our findings demonstrate that sopA inactivation or intracellular repression is the target of positive selection during the systemic infection caused by S. enterica serovars.

Burden of Ileal Perforations Among Surgical Patients Admitted in Tertiary Care Hospitals of Three Asian countries: Surveillance of Enteric Fever in Asia Project (SEAP), September 2016–September 2019

BackgroundTyphoid fever is caused by Salmonella enterica subspecies enterica serovar Typhi (S. Typhi) and can lead to systemic illness and complications. We aimed to characterize typhoid-related ileal perforation in the context of the population-based Surveillance of Enteric Fever in Asia Project (SEAP) in Bangladesh, Nepal and Pakistan.MethodsBetween September 2016 and September 2019, all cases of nontraumatic ileal perforation with a clinical diagnosis of typhoid were enrolled from 4 tertiary care hospitals in Karachi, 2 pediatric hospitals in Bangladesh, and 2 hospitals in Nepal. Sociodemographic data were collected from patients or their caregivers, and clinical and outcome data were retrieved from medical records. Tissue samples were collected for histopathology and blood cultures where available.ResultsOf the 249 enrolled cases, 2 from Bangladesh, 5 from Nepal and 242 from Pakistan. In Pakistan, most of the cases were in the 0–15 (117/242; 48%) and 16–30 (89/242; 37%) age groups. In all countries, males were most affected: Pakistan 74.9% (180/242), Nepal 80% (4/5), and Bangladesh 100% (2/2). Blood culture was done on 76 cases; 8 (11%) were positive for S. Typhi, and all were extensively drug resistant (XDR) S. Typhi. Tissue cultures was done on 86 patients; 3 (3%) were positive for S. Typhi, and all were XDR S. Typhi, out of 86 samples tested for histopathology 4 (5%) revealed ileal perforation with necrosis. Culture or histopathology confirmed total 15 (11%) enteric fever cases with ileal perforation are similar to the clinically diagnosed cases. There were 16/242 (7%) deaths from Pakistan. Cases of ileal perforation who survived were more likely to have sought care before visiting the sentinel hospital (P = .009), visited any hospital for treatment (P = .013) compared to those who survived.ConclusionsAlthough surveillance differed substantially by country, one reason for the higher number of ileal perforation cases in Pakistan could be the circulation of XDR strain of S. Typhi in Karachi.

Physico-chemical characteristics, antibacterial, and antioxidant activities of genuine forest honey from East Kalimantan

In the dense tropical forests of Kalimantan, Apis dorsata produces forest honey with pollen diversity that has the potential to have unique antibacterial and antioxidant properties. This study is aimed to report the physicochemical characteristics, antioxidant activity and antibacterial analysis of forest honey from East Kalimantan. A total of nine samples of forest honey were purchased from local buyers of several regions. The power of hydrogen (pH), water content, diastase enzymes, fructose levels, and glucose levels were measured. Antioxidant activity was measured with ABTS assay. Antibacterial activity was conducted against Staphylococcus aureus, Bacillus cereus, Escherichia coli, and S. enterica serovar Typhi. Fourier Transform Infra-Red (FTIR) identified antibacterial functional groups. Honey samples from tropical forests in East Kalimantan had pH between 2.93±0.06 and 3.83±0.06, a moisture content between 18.44±0.64 and 25.67±0.29%, fructose levels between 7.85±0.05 and 17.73±0.13%, and glucose levels between 1.24±0.16 and 17.34±0.14%. Goa Tembenus honey showed the highest IC50 antioxidant activity and the highest Diastase Enzyme activity. Goa Tembenus and Bongan honey showed good antibacterial activity against Gram-positive and Gram-negative. Minimum inhibitory levels of honey were found at concentrations of 25% and 30%. Honey from tropical forests in East Kalimantan has H2O2 as an antibacterial component.

Tenacious Endemic Typhoid Fever in Samoa.

BackgroundTyphoid fever has been endemic on the island nation of Samoa (2016 population, 195 979) since the 1960s and has persisted through 2019, despite economic development and improvements in water supply and sanitation.Methods Salmonella enterica serovar Typhi isolates from the 2 hospitals with blood culture capability and matched patient demographic and clinical data from January 2008 through December 2019 were analyzed. Denominators to calculate incidence by island, region, and district came from 2011 and 2016 censuses and from 2017–2019 projections from Samoa’s Bureau of Statistics. Data were analyzed to describe typhoid case burden and incidence from 2008 to 2019 by time, place, and person.ResultsIn sum, 53–193 blood culture-confirmed typhoid cases occurred annually from 2008 to 2019, without apparent seasonality. Typhoid incidence was low among children age < 48 months (17.6–27.8/105), rose progressively in ages 5–9 years (54.0/105), 10–19 years (60.7–63.4/105), and 20–34 years (61.0–79.3/105), and then tapered off; 93.6% of cases occurred among Samoans < 50 years of age. Most typhoid cases and the highest incidence occurred in Northwest Upolu, but Apia Urban Area (served by treated water supplies) also exhibited moderate incidence. The proportion of cases from short-cycle versus long-cycle transmission is unknown. Samoan S. Typhi are pansusceptible to traditional first-line antibiotics. Nevertheless, enhanced surveillance in 2019 detected 4 (2.9%) deaths among 140 cases.ConclusionsTyphoid has been endemic in Samoa in the period 2008–2019. Interventions, including mass vaccination with a Vi-conjugate vaccine coadministered with measles vaccine are planned.

Generation and Characterization of Typhoid Toxin-Neutralizing Human Monoclonal Antibodies.

Typhoid toxin is a virulence factor of Salmonella enterica serovar Typhi, the causative agent of typhoid fever, and is thought to be responsible for the symptoms of severe disease. This toxin has a unique A2B5 architecture with two active subunits, the ADP ribosyl transferase PltA and the DNase CdtB, linked to a pentameric B subunit, which is alternatively made of PltB or PltC. Here, we describe the generation and characterization of typhoid toxin-neutralizing human monoclonal antibodies by immunizing genetically engineered mice that have a full set of human immunoglobulin variable region genes. We identified several monoclonal antibodies with strong in vitro and in vivo toxin-neutralizing activity and different mechanisms of toxin neutralization. These antibodies could serve as the basis for the development of novel therapeutic strategies against typhoid fever.

The Salmonella enterica Serovar Typhi ltrR Gene Encodes Two Proteins Whose Transcriptional Expression Is Upregulated by Alkaline pH and Repressed at Their Promoters and Coding Regions by H-NS and Lrp.

LtrR is a LysR-type regulator involved in the positive expression of ompR to promote ompC and ompF expression. This regulatory network is fundamental for the control of bacterial transformation and resistance to the bile salt sodium deoxycholate in Salmonella enterica serovar Typhi. In this work, the transcriptional regulation of ltrR was characterized, revealing that the use of alternative promoters results in two transcripts. The larger one, the ltrR2 mRNA, was repressed at promoter and coding regions by H-NS, whereas Lrp repressed its expression at the coding region. In the case of the second and shorter ltrR1 transcript, it was repressed only at the coding region by H-NS and Lrp. Remarkably, pH 7.5 is a positive signal involved in the transcriptional expression of both ltrR units. Translational fusions and Western blot experiments demonstrated that ltrR2 and ltrR1 mRNAs encode the LtrR2 and LtrR1 proteins. This study adds new data on the complex genetic and regulatory characteristics of one of the most predominant types of transcriptional factors in bacteria, the LysR-type transcriptional regulators.IMPORTANCE The LysR-type transcriptional regulators are present in viruses, archaea, bacteria, and eukaryotic cells. Furthermore, these proteins are the most abundant transcriptional factors in bacteria. Here, we demonstrate that two LysR-type proteins are generated from the ltrR gene. These proteins are genetically induced by pH and repressed at the promoter and coding regions by the global regulators H-NS and Lrp. Thus, novel basic aspects of the complex genetic regulation of the LysR-type transcriptional regulators are described.

The Not so Good, the Bad and the Ugly: Differential Bacterial Adhesion and Invasion Mediated by Salmonella PagN Allelic Variants.

While advances in genomic sequencing have highlighted significant strain variability between and within Salmonella serovars, only a few protein variants have been directly related to evolutionary adaptation for survival, such as host specificity or differential virulence. The current study investigated whether allelic variation of the Salmonella adhesin/invasin PagN influences bacterial interaction with their receptors. The Salmonella enterica, subspecies enterica serovar Typhi (S. Typhi) allelic variant of PagN was found to bind significantly better to different enterocytes as well as to the extracellular matrix protein laminin than did the major Salmonella enterica, subspecies enterica serovar Typhimurium (S. Typhimurium) allele. The two alleles differed at amino acid residues 49 and 109 in two of the four predicted PagN surface loops, and residue substitution analysis revealed that a glutamic acid at residue 49 increased the adhesive and invasive properties of S. Typhi PagN. PagN sequence comparisons from 542 Salmonella strains for six representative S. enterica serovars and S. diarizonae further supported the role of glutamic acid at residues 49 and 109 in optimizing adhesion to cells and laminin, as well as for cell invasion. In summary, this study characterized unique residues in allelic variants of a virulence factor that participates in the colonization and invasive properties of different Salmonella stains, subspecies and serovars.

Oral typhoid vaccine Ty21a elicits antigen-specific resident memory CD4+ T cells in the human terminal ileum lamina propria and epithelial compartments

BackgroundSalmonella enterica serovar Typhi (S. Typhi) is a highly invasive bacterium that infects the human intestinal mucosa and causes ~ 11.9–20.6 million infections and ~ 130,000–223,000 deaths annually worldwide. Oral typhoid vaccine Ty21a confers a moderate level of long-lived protection (5–7 years) in the field. New and improved vaccines against enteric pathogens are needed but their development is hindered by a lack of the immunological correlates of protection especially at the site of infection. Tissue resident memory T (TRM) cells provide immediate adaptive effector immune responsiveness at the infection site. However, the mechanism(s) by which S. Typhi induces TRM in the intestinal mucosa are unknown. Here, we focus on the induction of S. Typhi-specific CD4+TRM subsets by Ty21a in the human terminal ileum lamina propria and epithelial compartments.MethodsTerminal ileum biopsies were obtained from consenting volunteers undergoing routine colonoscopy who were either immunized orally with 4 doses of Ty21a or not. Isolated lamina propria mononuclear cells (LPMC) and intraepithelial lymphocytes (IEL) CD4+TRM immune responses were determined using either S. Typhi-infected or non-infected autologous EBV-B cell lines as stimulator cells. T-CMI was assessed by the production of 4 cytokines [interferon (IFN)γ, interleukin (IL)-2, IL-17A and tumor necrosis factor (TNF)α] in 36 volunteers (18 vaccinees and 18 controls volunteers).ResultsAlthough the frequencies of LPMC CD103+ CD4+TRM were significant decreased, both CD103+ and CD103− CD4+TRM subsets spontaneously produced significantly higher levels of cytokines (IFNγ and IL-17A) following Ty21a-immunization. Importantly, we observed significant increases in S. Typhi-specific LPMC CD103+ CD4+TRM (IFNγ and IL-17A) and CD103− CD4+TRM (IL-2 and IL-17A) responses following Ty21a-immunization. Further, differences in S. Typhi-specific responses between these two CD4+TRM subsets were observed following multifunctional analysis. In addition, we determined the effect of Ty21a-immunization on IEL and observed significant changes in the frequencies of IEL CD103+ (decrease) and CD103− CD4+TRM (increase) following immunization. Finally, we observed that IEL CD103− CD4+TRM, but not CD103+ CD4+TRM, produced increased cytokines (IFNγ, TNFα and IL-17A) to S. Typhi-specific stimulation following Ty21a-immunization.ConclusionsOral Ty21a-immunization elicits distinct compartment specific immune responses in CD4+TRM (CD103+ and CD103−) subsets. This study provides novel insights in the generation of local vaccine-specific responses.Trial registration This study was approved by the Institutional Review Board and registered on ClinicalTrials.gov (identifier NCT03970304, Registered 29 May 2019—Retrospectively registered, http://www.ClinicalTrials.gov/NCT03970304)

Gene interaction network studies to decipher the multi-drug resistance mechanism in Salmonella enterica serovar Typhi CT18 reveal potential drug targets

Salmonella enterica subsp. enterica serovar Typhi, a human enteric pathogen causing typhoid fever, developed resistance to multiple antibiotics over the years. The current study was dedicated to understand the multi-drug resistance (MDR) mechanism of S. enterica serovar Typhi CT18 and to identify potential drug targets that could be exploited for new drug discovery. We have employed gene interaction network analysis for 44 genes which had 275 interactions. Clustering analysis resulted in three highly interconnecting clusters (C1–C3). Functional enrichment analysis revealed the presence of drug target alteration and three different multi-drug efflux pumps in the bacteria that were associated with antibiotic resistance. We found seven genes (arnA,B,C,D,E,F,T) conferring resistance to Cationic Anti-Microbial Polypeptide (CAMP) molecules by membrane Lipopolysaccharide (LPS) modification, while macB was observed to be an essential controlling hub of the network and played a crucial role in MacAB-TolC efflux pump. Further, we identified five genes (mdtH, mdtM, mdtG, emrD and mdfA) which were involved in Major Facilitator Superfamily (MFS) efflux system and acrAB contributed towards AcrAB-TolC efflux pump. All three efflux pumps were seen to be highly dependent on tolC gene. The five genes, namely tolC, macB, acrA, acrB and mdfA which were involved in multiple resistance pathways, can act as potential drug targets for successful treatment strategies. Therefore, this study has provided profound insights into the MDR mechanism in S. Typhi CT18. Our results will be useful for experimental biologists to explore new leads for S. enterica.

Typhoid and paratyphoid fever

Typhoid fever and paratyphoid fever are systemic infectious diseases of global significance caused by Salmonella enterica subspecies enterica Serovar Typhi (short name: Salmonella Typhi) or Serovar Paratyphi (short name: Salmonella Paratyphi). The course of these fecal-orally transmitted diseases is mainly characterized by a high fever. Left untreated, the course of typhoid fever can be severe and lethal. The infection is almost always acquired outside of Europe (mainly in India) and is notifiable in Germany, Austria and Switzerland. Paratyphoid is an attenuated disease of typhoid fever caused by Salmonella Paratyphi. Available vaccines only protect against Salmonella Typhi. Antibiotic resistance reflects the situation in endemic countries and shows a worrying increase of multi-drug resistant isolates. Currently, third-generation cephalosporins such as ceftriaxone are recommended as first-line therapy; if sensitive to quinolones, fluoroquinolones such as ciprofloxacin may continue to be administered. Crucial preventive measures for travelers to endemic regions include consistent water and food hygiene as well as vaccination, whereby only protection rates of 50-70 % are achieved by currently available vaccines. In the light of increasing multi-drug resistance, a more effective conjugate vaccine against Salmonella Typhi with cross-reactivity against Salmonella Paratyphi is needed more than ever.

Epidemiological and Clinical Characteristics of International Travelers with Enteric Fever and Antibiotic Resistance Profiles of Their Isolates: a GeoSentinel Analysis.

Enteric fever, caused by Salmonella enterica serovar Typhi (S Typhi) and S. enterica serovar Paratyphi (S Paratyphi), is a common travel-related illness. Limited data are available on the antimicrobial resistance (AMR) patterns of these serovars among travelers. Records of travelers with a culture-confirmed diagnosis seen during or after travel from January 2007 to December 2018 were obtained from GeoSentinel. Traveler demographics and antimicrobial susceptibility data were analyzed. Isolates were classified as nonsusceptible if intermediate or resistant or as susceptible in accordance with the participating site's national guidelines. A total of 889 travelers (S Typhi infections, n = 474; S Paratyphi infections, n = 414; coinfection, n = 1) were included; 114 (13%) were children of <18 years old. Most individuals (41%) traveled to visit friends and relatives (VFRs) and acquired the infection in South Asia (71%). Child travelers with S Typhi infection were most frequently VFRs (77%). The median trip duration was 31 days (interquartile range, 18 to 61 days), and 448 of 691 travelers (65%) had no pretravel consultation. Of 143 S Typhi and 75 S Paratyphi isolates for which there were susceptibility data, nonsusceptibility to antibiotics varied (fluoroquinolones, 65% and 56%, respectively; co-trimoxazole, 13% and 0%; macrolides, 8% and 16%). Two S Typhi isolates (1.5%) from India were nonsusceptible to third-generation cephalosporins. S Typhi fluoroquinolone nonsusceptibility was highest when infection was acquired in South Asia (70 of 90 isolates; 78%) and sub-Saharan Africa (6 of 10 isolates; 60%). Enteric fever is an important travel-associated illness complicated by AMR. Our data contribute to a better understanding of region-specific AMR, helping to inform empirical treatment options. Prevention measures need to focus on high-risk travelers including VFRs and children.

Cholestatic hepatitis in a child with typhoid fever –a case report

Typhoid fever is a common infectious disease in developing countries. It is caused by Salmonella typhi. Salmonella is a genus of the family Enterobacteriaceae. They are rod-shaped, Gram-negative, facultative anaerobic bacteria, most of which are motile by perit¬richous flagella (which bear H antigen [s]). S. Typhi is taxonomically designated as Salmonella enterica subspecies enterica serovar Typhi. In addition to the H antigen (s), 2 polysaccharide surface antigens aid in further characterization of S. enterica, namely the somatic O antigen and capsular Vi (virulence) anti¬gen. Vi antigen is associated with resistance to complement-mediated bacterial lysis and resistance to complement activation by the alternate pathway. Salmonella enterica serovars Paratyphi A and Paraty¬phi B (and uncommonly Paratyphi C) cause a disease (paratyphoid fever) that is clinically indistinguishable from typhoid fever, particularly in parts of Asia. Typhoid fever and paratyphoid fever are collectively termed enteric fever.

Ovarian abscess caused by Salmonella enterica serovar Typhi: a case report

BackgroundTyphoid fever is a human-specific disease caused by a bacterium, Salmonella enterica subspecies enterica serovar Typhi. It is transmitted through ingestion of contaminated food or water. It is mostly diagnosed by blood culture. Salmonella Typhi usually manifests as a febrile illness with bacteremia after initial entry through the gastrointestinal route, but it can occasionally cause significant disease in extraintestinal sites. We report a case of a girl in Fiji with a right ovarian abscess infected by Salmonella Typhi.Case presentationA 14-year-old iTaukei (indigenous Fijian) girl presented to our hospital with abdominal pain of 1 month’s duration. Two days prior to her admission, she developed high-grade fever and nausea and had one episode of vomiting. On presentation, she appeared unwell; she was tachycardic (116 beats per minute) and febrile (38.8 °C). Her abdominal examination revealed generalized tenderness. Other examination findings were normal. The provisional diagnosis of abdominal sepsis led to an emergency laparotomy during which an enlarged right ovary was found to be spontaneously discharging pus. The ovary was incised and drained, and the patient was commenced on intravenous ceftriaxone 1 g twice daily, cloxacillin 1 g four times daily, and metronidazole 500 mg three times daily. She recovered promptly and was discharged to home on the sixth postoperative day. The purulent material from the ovary grew Salmonella Typhi.ConclusionExtraintestinal infections caused by Salmonella Typhi are rare but can cause severe and life-threatening disease. Our patient had a prolonged history of abdominal pain and was found to have a ruptured right ovarian abscess due to Salmonella Typhi. Ovarian abscesses in girls who are not sexually active are not associated with pelvic inflammatory disease and suggest local or hematogenous spread. This case report may increase health workers awareness to include common and endemic infections in the differential diagnosis of unusual clinical presentations to help the initiation of appropriate investigation and management as quickly as possible.

Typhoid fever among febrile Nigerian patients: Prevalence, diagnostic performance of the Widal test and antibiotic multi-drug resistance.

Over-dependence on clinical presentation and/or the Widal agglutination test for the diagnosis of typhoid fever in developing countries can lead to antibiotic abuse. In Nigeria, the antibiotic resistance of typhoid organisms is poorly characterized. In this study, we determined the prevalence of culture positivity among patients suspected of having typhoid fever, evaluated the diagnostic value of the Widal test and the burden created by the multi-drug resistance of typhoid organisms in South-East Nigeria. This was a prospective and case-controlled study carried out between 2013 and 2016. We acquired samples of blood/stool/urine cultures, and data relating to the Widal agglutination test and malaria parasites from 810 febrile patients (suspected of having typhoid) and 288 apparently healthy controls. Individuals with a history of antibiotic use within the previous 14 days were excluded. We then carried out antibiotic susceptibility tests on all isolates. Multi-drug resistance was defined as a resistance to ≥3 of the antibiotics tested. We determined the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Widal test for typhoid laboratory diagnosis compared to bacterial culture which is the gold standard. A P-value <0.05 was considered to be statistically significant. The mean age of typhoid suspects was 33.1±6.5 years and 50.7% were women. Of the 810 typhoid suspects tested, 114 (14.1%) had positive cultures for the typhoid organisms Salmonella enterica serovar paratyphi (72) and S. enterica serovar Typhi (42). Sample-specific rates of culture positivity were as follows: stool (72; 8.9%), blood (21; 2.6%) and urine (21; 2.6%), P<0.001. None of the controls had typhoid isolates. The sensitivity, specificity, PPV and NPV of the Widal test were 49.1%, 90.7%, 46.2% and 91.6%, respectively. Malaria parasitaemia was detected in 180 (22.2%) febrile patients, out of whom 115 (63.9%) had a positive Widal test for O/H antigens vs. 1% (6/630) in those with negative malaria parasite test results (P<0.001). The rate of false-positive Widal titres was 48%. Antibiotic multi-drug resistance was detected in 52.6% of patients. The antibiotics with the highest susceptibility were ciprofloxacin, levofloxacin and meropenem (all 100% susceptibility) and ceftriaxone (95.6% susceptibility). Our data showed that while typhoid fever is common in Nigeria, malaria is more prevalent. Our analysis showed that the Widal test performed poorly as a diagnostic test and that the burden created by multi-drug resistance was high. Our data indicate that periodic surveillance of antibiotic susceptibility is critical for optimal typhoid therapy.

Human Bile-Mediated Regulation of Salmonella Curli Fimbriae.

Typhoid fever is caused primarily by Salmonella enterica serovar Typhi. Approximately 3% to 5% of individuals infected with S Typhi become chronic carriers with the gallbladder (GB) as the site of persistence, as gallstones within the GB are a platform on which the bacteria form a biofilm. S Typhi is a human-restricted pathogen; therefore, asymptomatic carriers represent a critical reservoir for further spread of disease. To examine the dynamics of the Salmonella biofilm during chronic carriage, the human gallstone (GS) environment was simulated by growing biofilms on cholesterol-coated surfaces in the presence of bile, and the transcriptional profile was determined. Some of the most highly activated genes corresponded to the curli fimbria operon, with the major structural component csgA upregulated >80-fold. The curli protein polymer is a major component of the extracellular matrix (ECM) in Salmonella biofilms. The upregulation of curli fimbriae by human bile was validated through reverse transcription-quantitative PCR (qRT-PCR), microscopy, and Western blotting. Interestingly, this activation appears human specific, as qRT-PCR showed repression of csgA in biofilms grown in mouse or ox bile. Comparative transcriptional studies of the two divergent csg operons suggest an early activation of both operons in minimal medium complemented with glucose that quickly diminishes as the biofilm matures. However, in the presence of human bile, there is a modest activation of both operons that steadily increases as the biofilm matures. Understanding the effect of the GB environment on key biofilm-associated factors can help target antibiofilm therapeutics or other preventative strategies to eradicate chronic carriage.IMPORTANCE Typhoid fever is caused by Salmonella enterica serovar Typhi, and 3% to 5% of patients become chronic gallbladder (GB) carriers (also known as "Typhoid Marys"). We have previously demonstrated a role for Salmonella biofilm formation on gallstones as a primary mechanism of carriage. In this study, we found that the important biofilm extracellular matrix component curli fimbria is induced in an in vitro human GB model system. This induction is specific to human bile and increases as the biofilm matures. We also found that the biofilm and curli regulator CsgD play a key role in this observed induction. This work further enhances our understanding biofilm-mediated chronic carriage and provides a potential target for eliminating persistent GB infection by S Typhi.

Physicochemical and Antimicrobial Properties of Hydroxypropyl Methylcellulose-Cinnamon Essential Oil Emulsion: Effects of Micro- and Nanodroplets

Abstract Emulsion is an efficient encapsulation tool for enhancing the functional properties of essential oils (EOs). Herein, two two-dimensional cinnamon essential oil emulsions (from micro- to nanoscales) were emulsified by hydroxypropyl methylcellulose, and their antimicrobial and physicochemical properties were investigated. For the models of Escherichia coli CGMCC 1.0907, Salmonella enterica subsp. Enterica serovar Typhi (CICC 10867), Staphylococcus aureus CGMCC 1.0089, and Listeria monocytogene CGMCC 1.9144, the minimum inhibitory concentration (MIC) of the nanoemulsion was 31.25 μL/mL compared to that of the microemulsion (62.5–125 μL/mL) and pure oil (125–250 μL/mL), indicating the superiority of nanoemulsion as an antibacterial agent. The results showed that the highest activity was seen in the gram-positive L. monocytogenes whereas the lowest was in the gram-negative S. enterica. The identified properties of HPMC (hydroxypropyl methylcellulose) provide the potential for emulsifying and enhancing essential oils in light industries, especially for food processing.