Salmonella infections: an update on epidemiology, management, and prevention

Molecular Characterization of Multidrug-Resistant and Extended-Spectrum β-Lactamases-Producing Salmonella enterica Serovars Enteritidis and Typhimurium Isolated from Raw Meat in Retail Markets

In the present study, a total of 720 samples were collected from retail raw meat from 13 upazilas in Sylhet District, Bangladesh, of which 225 samples were from cattle meat, 210 samples were from goat meat, and 285 samples were from chicken meat. Salmonella enterica serovars Typhimurium and Enteritidis were screened for extended-spectrum β-lactamase (ESBL) genes using multiplex PCR. Among the 720 samples, Salmonella spp. was detected in 28.06% (202 out of 720) of the samples, with S. Enteritidis and S. Typhimurium were identified in 11.53% (83 out of 720) and 12.22% (88 out of 720) of the samples, respectively. It was found that all Salmonella enterica serovars isolated from cattle meat displayed multidrug resistance (MDR) based on antimicrobial susceptibility testing. Notably, a significant proportion of S. Enteritidis isolates and all S. Typhimurium isolates from goat meat demonstrated complete resistance to multiple drugs (ampicillin, cefuroxime, and ceftazidime). Regarding chicken meat, out of 89 isolates encompassing both S. Typhimurium and S. Enteritidis, 57 isolates (64.04%) exhibited MDR. Additionally, blaCTX-M-1 exhibited the highest occurrence at 15.69% for S. Typhimurium and 7.89% for S. Enteritidis in chicken meat. Moreover, blaCTX-M-9 was only detected at 3.92% for S. Enteritidis in chicken meat. Furthermore, blaOXA had the highest prevalence rate of 19.04% for S. Enteritidis and 25.80% for S. Typhimurium in cattle meat, followed by chicken meat. These findings highlight the urgency for monitoring ESBL-producing Salmonella in retail raw meat and the need for strict measure to manage antibiotic use to prevent the spread of multidrug-resistant and ESBL-producing Salmonella strains, thereby protecting humans and reducing public health risks.

Prevalence and serotype of poultry salmonellosis in Africa: a systematic review and meta-analysis

RESEARCH HIGHLIGHTS

The pooled sample prevalence of poultry salmonellosis in Africa is high (14.4%).The highest PPE was recorded in meat and meat products.Salmonella serotypes of zoonotic importance were found in all sample types.Salmonella Enteritidis and Typhimurium are common serotypes spreading in Africa.

Emergence of Rarely Reported Extensively Drug-Resistant Salmonella Enterica Serovar Paratyphi B among Patients in East China

BACKGROUND

In recent years, global concern over increasing multidrug resistance (MDR) among various Salmonella serotypes has grown significantly. However, reports on MDR Salmonella Paratyphi B remain scarce, let alone the extensively drug-resistant (XDR) strains.

METHODS

In this retrospective study, we investigated the isolates of Salmonella Paratyphi B in Jiangsu Province over the past decade and carried out antimicrobial susceptibility tests, then the strains were sequenced and bioinformatics analyses were performed.

RESULTS

27 Salmonella Paratyphi B strains were identified, of which the predominant STs were ST42 (11), ST86 (10), and ST2814 (5). Among these strains, we uncovered four concerning XDR Salmonella Paratyphi B ST2814 strains (4/5) which were previously unreported. These alarmingly resistant isolates showed resistance to all three major antibiotic classes for Salmonella treatment and even the last resort treatment tigecycline. Bioinformatics analysis revealed high similarity between the plasmids harbored by these XDR strains and diverse Salmonella serotypes and Escherichia coli from China and neighboring regions. Notably, these four plasmids carried the ramAp gene responsible for multiple antibiotic resistance by regulating the AcrAB-TolC pump, predominantly originating from China. Additionally, a distinct MDR ST42(1/11) strain with an ICE on chromosome was also identified. Furthermore, phylogenetic analysis of global ST42/ST2814 isolates highlighted the regional specificity of these strains, with Jiangsu isolates clustering together with domestic isolates and XDR ST2814 forming a distinct branch, suggesting adaptation to local antibiotic pressures.

CONCLUSIONS

This research underscores the pressing need for closely monitoring the MDR/XDR Salmonella Paratyphi B, particularly the emerging ST2814 strains in Jiangsu Province, to effectively curb its spread and protect public health. Moreover, surveillance should be strengthened across different ecological niches and genera to track resistance genes and horizontal gene transfer elements under the concept of "ONE HEALTH".

Infectious factors in myocarditis: a comprehensive review of common and rare pathogens

BACKGROUND

Myocarditis is a significant health threat today, with infectious agents being the most common cause. Accurate diagnosis of the etiology of infectious myocarditis is crucial for effective treatment.

MAIN BODY

Infectious myocarditis can be caused by viruses, prokaryotes, parasites, and fungi. Viral infections are typically the primary cause. However, some rare opportunistic pathogens can also damage heart muscle cells in patients with immunodeficiencies, neoplasms and those who have undergone heart surgery.

CONCLUSIONS

This article reviews research on common and rare pathogens of infectious myocarditis, emphasizing the complexity of its etiology, with the aim of helping clinicians make an accurate diagnosis of infectious myocarditis.

Fractionation of Carlina acaulis L. Root Methanolic Extract as a Promising Path towards New Formulations against Bacillus cereus and Methicillin-Resistant Staphylococcus aureus

The root of Carlina acaulis L. has been widely used in traditional medicine for its antimicrobial properties. In this study, the fractionation of methanol extract from the root was conducted. Four fractions (A, B, C, and D) were obtained and tested against a range of bacteria and fungi. The results showed promising antibacterial activity, especially against Bacillus cereus, where the minimal inhibitory concentration (MIC) was determined to be equal to 0.08 mg/mL and 0.16 mg/mL for heptane (fraction B) and ethyl acetate (fraction C), respectively. In the case of the methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300 strain, the same fractions yielded higher MIC values (2.5 and 5.0 mg/mL, respectively). This was accompanied by a lack of apparent cytotoxicity to normal human BJ foreskin fibroblasts, enterocytes derived from CaCo2 cells, and zebrafish embryos. Further analyses revealed the presence of bioactive chlorogenic acids in the fractionated extract, especially in the ethyl acetate fraction (C). These findings support the traditional use of the root from C. acaulis and pave the way for the development of new formulations for treating bacterial infections. This was further evaluated in a proof-of-concept experiment where fraction C was used in the ointment formulation, which maintained high antimicrobial activity against MRSA and displayed low toxicity towards cultured fibroblasts.

Salmonellosis: An Overview of Epidemiology, Pathogenesis, and Innovative Approaches to Mitigate the Antimicrobial Resistant Infections

Salmonella is a major foodborne pathogen and a leading cause of gastroenteritis in humans and animals. Salmonella is highly pathogenic and encompasses more than 2600 characterized serovars. The transmission of Salmonella to humans occurs through the farm-to-fork continuum and is commonly linked to the consumption of animal-derived food products. Among these sources, poultry and poultry products are primary contributors, followed by beef, pork, fish, and non-animal-derived food such as fruits and vegetables. While antibiotics constitute the primary treatment for salmonellosis, the emergence of antibiotic resistance and the rise of multidrug-resistant (MDR) Salmonella strains have highlighted the urgency of developing antibiotic alternatives. Effective infection management necessitates a comprehensive understanding of the pathogen's epidemiology and transmission dynamics. Therefore, this comprehensive review focuses on the epidemiology, sources of infection, risk factors, transmission dynamics, and the host range of Salmonella serotypes. This review also investigates the disease characteristics observed in both humans and animals, antibiotic resistance, pathogenesis, and potential strategies for treatment and control of salmonellosis, emphasizing the most recent antibiotic-alternative approaches for infection control.

Quantitative Proteomics of the Intracellular Bacterial Pathogen Salmonella enterica Serovar Typhimurium

Mass spectrometry-based proteomics provides a wealth of information about changes in protein production and abundance under diverse conditions, as well as mechanisms of regulation, signaling cascades, interaction partners, and communication patterns across biological systems. For profiling of intracellular pathogens, proteomic profiling can be performed in the absence of a host to singularly define the pathogenic proteome or during an infection-like setting to identify dual perspectives of infection. In this chapter, we present techniques to extract proteins from the human bacterial intracellular pathogen, Salmonella enterica serovar Typhimurium, in the presence of macrophages, an important innate immune cell in host defense. We outline sample preparation, including protein extraction, digestion, and purification, as well as mass spectrometry measurements and bioinformatics analysis. The data generated from our dual perspective profiling approach provides new insight into pathogen and host protein modulation under infection-like conditions.

Salmonella enterica serotypes isolated for the first time in laying hens, and their susceptibility to antibiotics

In this study, a total of 323 drag swab samples were taken from laying hen fresh feces from 3 different provinces (Kırklareli, Edirne, and Tekirdağ), which are located in the European part of Türkiye. According to the ISO 6579: 2002 method, 17.3% of the samples were found positive for Salmonella. Obtained 56 Salmonella isolates were serotyped by slide agglutination using antisera according to Kauffmann White Le Minor Scheme. Sixteen serotypes of Salmonella were identified as S. Typhimurium (28.6%), S. Kentucky (17.9%), S. Abony (16.1%), S. Infantis (8.9%), S. Enteritidis (5.4%), S. Anatum (3.6%), S. Saintpaul (3.6%), S. Szentes (1.8%), S. Dibra (1.8%), S. Fallowfield (1.8%), S. Kimuenza (1.8%), S. Escanaba (1.8%), S. Nagoya (1.8%), S. Mbandaka (1.8%), S. Agona (1.8%), and Salmonella II 17: e, n, x, z15: 1,6 (1.8%). Isolations of S. Kimuenza, S. Escanaba, and S. Nagoya from laying hens are reported for the first time in Türkiye. The isolations of S. Dibra, S. Fallowfield, S. Szentes, and Salmonella II 17: e, n, x, z15: 1,6 from laying hens are the first report in the world. A total of 56 Salmonella isolates were tested for susceptibility to amoxicillin-clavulanic acid, cefepime, azithromycin, cefoxitin, and trimethoprim/sulfamethoxazole by the disk diffusion method. While 10% of S. Kentucky isolates were resistant to ofloxacin, and S. Kimuenza was only resistant to chloramphenicol.

The Microbial Tryptophan Metabolite Contributes to the Remission of Salmonella typhimurium Infection in Mice

Salmonella enterica serovar Typhimurium (S. Tm) causes severe foodborne diseases. Interestingly, gut microbial tryptophan (Trp) metabolism plays a pivotal role in such infections by a yet unknown mechanism. This study aimed to explore the impact of Trp metabolism on S. Tm infection and the possible mechanisms involved. S. Tm-infected C57BL6/J mice were used to demonstrate the therapeutic benefits of the Bacillus velezensis JT3-1 (B. velezensis/JT3-1) strain or its cell-free supernatant in enhancing Trp metabolism. Targeted Trp metabolomic analyses indicated the predominance of indole-3-lactic acid (ILA), an indole derivative and ligand for aryl hydrocarbon receptor (AHR). Based on the 16S amplicon sequencing and correlation analysis of metabolites, we found that B. velezensis supported the relative abundance of Lactobacillus and Ligilactobacillus in mouse gut and showed positive correlations with ILA levels. Moreover, AHR and its downstream genes (especially IL-22) significantly increased in mouse colons after B. velezensis or cell-free supernatant treatment, suggesting the importance of AHR pathway activation. In addition, ILA was found to stimulate primary mouse macrophages to secrete IL-22, which was antagonized by CH-223191. Furthermore, ILA could protect mice from S. Tm infection by increasing IL-22 in Ahr+/- mice, but not in Ahr-/- mice. Finally, Trp-rich feeding showed amelioration of S. Tm infection in mice, and the effect depended on gut microbiota. Taken together, these results suggest that B. velezensis-associated ILA contributes to protecting mice against S. Tm infection by activating the AHR/IL-22 pathway. This study provides insights into the involvement of microbiota-derived Trp catabolites in protecting against Salmonella infection.

Non-typhoidal Salmonella enteritidis prosthetic valve endocarditis

In this case, we present a rare cause of prosthetic valve endocarditis. A man in his 80s presented to the emergency department with fever and diarrhoea. The patient underwent a transcatheter aortic valve replacement 17 years earlier. A negative PCR result in faeces for Salmonella and positive blood cultures with Salmonella gave rise to the suspicion of an intravascular Salmonella infection, which was confirmed with a positron emission tomography. Due to the low prevalence of Salmonella endocarditis, there is no consensus on the most effective treatment. Guidelines recommend early surgery and long-term antimicrobial treatment in endocarditis with Gram-negative bacteria. In this case, surgery was not deemed feasible given the patient his advanced age and multiple comorbidities. Despite treatment with intravenous antibiotics, the patient succumbed to progression of endocarditis 37 days after admission.

Salmonella infection among the pediatric population at a tertiary care children's hospital in central Nepal: a retrospective study

Background

Typhoid fever, an infective bacterial disease, is capable of causing fatal systemic infection in humans, and in an era of antimicrobial resistance, it has become of public health importance. This study aimed to investigate the laboratory diagnosis of Salmonella bloodstream infection, its serotype, antimicrobial resistance pattern, and seasonal variation at a tertiary care children's hospital.

Methods

We undertook a retrospective, cross-sectional study by reviewing hospital-based laboratory records of patients whose blood culture samples were submitted from the outpatient department to the laboratory of a tertiary care children's hospital in Kathmandu, Nepal, from January 2017 to January 2019.

Results

Among the total blood culture samples obtained (n = 39,771), bacterial isolates (n = 1,055, 2.65%) belonged either to the Genus Enterobacteriaceae or Genus Acinetobacter. Altogether (n = 91, 8.63%), isolates were positive for Salmonella spp., which were further identified as Salmonella enterica subsp. enterica ser. Typhi (n = 79, 7.49%), Salmonella enterica subsp. enterica ser. Paratyphi A (n = 11, 1.04%), and Salmonella enterica subsp. enterica ser. Paratyphi B (n = 1, 0.1%). The median age of patients was 6  years (IQR: 4-9), with male and female patients constituting (n = 53, 58.24%; OR, 1.0; 95% CI, 0.60-1.67) and (n = 38, 41.76%; OR, 0.98; 95% CI, 0.49-2.05) cases, respectively. The disease was observed throughout the year, with a high prevalence toward the spring season (March-May). An antibiogram showed resistance more toward nalidixic acid with S. Typhi, comprising half the isolates (n = 52, 65.82%; p = 0.11). Resistance toward β-lactams with β-lactamase inhibitors (amoxicillin/clavulanate; 1.27%) was seen in a single isolate of S. Typhi. The multidrug resistance pattern was not pronounced. The multiple antibiotic resistance (MAR) index was in the range between 0.14 and 0.22 in S. Typhi and 0.22 and 0.23 in S. Paratyphi.

Conclusion

Salmonella Typhi was the predominant ser. Infection was common among children between 1 and 5 years of age, showing male predominance and with the spring season contributing to a fairly higher number of cases. Antimicrobial susceptibility testing of S. Typhi showed more resistance toward nalidixic acid, with only a single isolate resistant to β-lactamase inhibitors (amoxicillin/clavulanate). Alarming multidrug resistance patterns were not observed. The MAR index in this study indicates the importance of the judicious use of antimicrobials and hospital infection prevention and control practices.

SW16-7, a Novel Ackermannviridae Bacteriophage with Highly Effective Lytic Activity Targets Salmonella enterica Serovar Weltevreden

Salmonella enterica serovar Weltevreden is a foodborne pathogen commonly transmitted through fresh vegetables and seafood. In this study, a lytic phage, SW16-7, was isolated from medical sewage, demonstrating high infectivity against S. Weltevreden, S. London, S. Meleagridis, and S. Give of Group O:3. In vitro inhibition assays revealed its effective antibacterial effect for up to 12 h. Moreover, analysis using the Comprehensive Antibiotic Resistance Database (CARD) and the Virulence Factor Database (VFDB) showed that SW16-7's genome does not contain any virulence factors or antibiotic resistance genes, indicating its potential as a promising biocontrol agent against S. Weltevreden. Additionally, a TSP gene cluster was identified in SW16-7's genome, with TSP1 and TSP2 showing a high similarity to lysogenic phages ε15 and ε34, respectively, in the C-terminal region. The whole-genome phylogenetic analysis classified SW16-7 within the Ackermannviridae family and indicated a close relationship with Agtrevirus, which is consistent with the ANI results.

Manipulation of host immune defenses by effector proteins delivered from multiple secretion systems of Salmonella and its application in vaccine research

Salmonella is an important zoonotic bacterial species and hazardous for the health of human beings and livestock globally. Depending on the host, Salmonella can cause diseases ranging from gastroenteritis to life-threatening systemic infection. In this review, we discuss the effector proteins used by Salmonella to evade or manipulate four different levels of host immune defenses: commensal flora, intestinal epithelial-mucosal barrier, innate and adaptive immunity. At present, Salmonella has evolved a variety of strategies against host defense mechanisms, among which various effector proteins delivered by the secretory systems play a key role. During its passage through the digestive system, Salmonella has to face the intact intestinal epithelial barrier as well as competition with commensal flora. After invasion of host cells, Salmonella manipulates inflammatory pathways, ubiquitination and autophagy processes with the help of effector proteins. Finally, Salmonella evades the adaptive immune system by interfering the migration of dendritic cells and interacting with T and B lymphocytes. In conclusion, Salmonella can manipulate multiple aspects of host defense to promote its replication in the host.

Sensitive detection of viable salmonella bacteria based on tertiary cascade signal amplification via splintR ligase ligation-PCR amplification-CRISPR/Cas12a cleavage

Several viable Salmonella bacteria are capable of causing severe human diseases and huge economic losses. In this regard, viable Salmonella bacteria detection techniques that can identify small numbers of microbial cells are highly valuable. Here, we present a detection method (referred to as SPC) based on the amplification of tertiary signals using splintR ligase ligation, PCR amplification and CRISPR/Cas12a cleavage. The detection limit of the SPC assay was 6 copies (HilA RNA) and 10 CFU (cell). Based on Intracellular HilA RNA detection, this assay can be used to distinguish between viable and dead Salmonella. In addition, it is able to detect multiple serotypes of Salmonella and has been successfully used to detect Salmonella in milk or isolated from farms. Overall, this assay is a promising test for viable pathogens detection and biosafety control.

Peritonitis by perforation of the gall bladder of typhoid origin in children

Peritonitis by perforation of the gall bladder of typhic origin is a rare condition. In Côte d'Ivoire, no studies to our knowledge have addressed the vesicular complications of typhoid fever in children. The aim of this work was to describe the epidemic-clinical, therapeutic and evolutionary aspects of the perforation of the gall bladder of typhic origin in subjects under 15 years of age. In 6 years, five children showed a vesicular perforation of typhic origin or 9.4% of peritonites of typhic origin. They were 5 boys with an average age of 07.4 years 5-11 years. The children were from low socioeconomic backgrounds. No history was noted. Clinical examination revealed peritoneal syndrome. X-ray of the abdomen without preparation carried out in all children had objectified a diffuse greyness. Leucocytosis was present in all cases. Treatment in all children initially consisted of resuscitation and antibiotic therapy with the 3^rd generation cephalosporin and an imidazole. Surgical exploration revealed gangrene and perforated gallbladder without damage to other organs or the presence of stones. A cholecystectomy was performed. The following procedures were simple in 4 patients. A patient died of sepsis following postoperative peritonitis by biliary fistula. Perforation of the gall bladder of typhic origin is rare in children. It is usually discovered at the stage of peritonitis. The treatment combines antibiotic therapy and cholecystectomy. Systematic screening should reduce the progression to this complication.

Assessing milk products quality, safety, and influencing factors along the dairy value chain in eastern Democratic Republic of the Congo

Dairying is one of the new promising economic sectors in eastern Democratic Republic of Congo (DRC), but still not explored enough to ensure consumers' safety. This study aimed to assess the health risks and nutritional profile of milk products along the value chain in South-Kivu and Tanganyika provinces. A total of 288 milk actors, including 160 producers, 35 collectors and 93 vendors, were concerned for interview and milk samples collection. A total of 302 milk samples (159 raw, 44 pasteurized, 76 fermented and 19 white cheese so-called “Mashanza”) were collected for physicochemical [pH, fat, non-fat dry matter (NFDM), lactose, protein, freezing point, density] and microbiological (total Aerobic Mesophilic Flora, Escherichia coli, Total Coliforms, Fecal Coliforms, Salmonella and Staphylococci) analyses. Results revealed that the physicochemical characteristics of the milk mostly varied according to the type of milk and the regions. The pasteurized milk from Tanganyika presented the best physicochemical parameters [crude protein (CP) = 4.36%, Fat = 4.06%, NFDM = 12%, lactose = 5.4%, density = 1.02 and pH = 6.59] compared to other types of milk. For microbiology, no E. coli was recorded but Salmonella and Staphylococci were found in all the milk types with the values not exceeding 3 × 104 CFU ml−1 and 3 × 103 CFU ml−1, respectively. This implies a long-term consumers' health issue if appropriate measures are not taken by milk actors along the value chain. The microbiological quality was influenced by the ecologies of production axis (representing the production zones) and by handling methods and infrastructures used by the actors involved along the value chain. Factors related to animal husbandry, milking method, milk processing and packaging had no significant effect on the physicochemical parameters under study. These results indicated that health risks for milk consumers are accrued by production practices and handling by milk actors due to shortage of required skills and appropriate equipment along the milk value chain. Observance of hazard analysis critical control point (HACCP) measures is carefully required along the milk value chain nodes to improve the quality of milk produced and sold and thus reduce the risks among consumers in South-Kivu and Tanganyika provinces.

Cation Homeostasis: Coordinate Regulation of Polyamine and Magnesium Levels in Salmonella

Polyamines are organic cations that are important in all domains of life. Here, we show that in Salmonella, polyamine levels and Mg2+ levels are coordinately regulated and that this regulation is critical for viability under both low and high concentrations of polyamines. Upon Mg2+ starvation, polyamine synthesis is induced, as is the production of the high-affinity Mg2+ transporters MgtA and MgtB. Either polyamine synthesis or Mg2+ transport is required to maintain viability. Mutants lacking the polyamine exporter PaeA, the expression of which is induced by PhoPQ in response to low Mg2+, lose viability in the stationary phase. This lethality is suppressed by blocking either polyamine synthesis or Mg2+ transport, suggesting that once Mg2+ levels are reestablished, the excess polyamines must be excreted. Thus, it is the relative levels of both Mg2+ and polyamines that are regulated to maintain viability. Indeed, sensitivity to high concentrations of polyamines is proportional to the Mg2+ levels in the medium. These results are recapitulated during infection. Polyamine synthesis mutants are attenuated in a mouse model of systemic infection, as are strains lacking the MgtB Mg2+ transporter. The loss of MgtB in the synthesis mutant background confers a synthetic phenotype, confirming that Mg2+ and polyamines are required for the same process(es). Mutants lacking PaeA are also attenuated, but deleting paeA has no phenotype in a polyamine synthesis mutant background. These data support the idea that the cell coordinately controls both the polyamine and Mg2+ concentrations to maintain overall cation homeostasis, which is critical for survival in the macrophage phagosome. IMPORTANCE Polyamines are organic cations that are important in all life forms and are essential in plants and animals. However, their physiological functions and regulation remain poorly understood. We show that polyamines are critical for the adaptation of Salmonella to low Mg2+ conditions, including those found in the macrophage phagosome. Polyamines are synthesized upon low Mg2+ stress and partially replace Mg2+ until cytoplasmic Mg2+ levels are restored. Indeed, it is the sum of Mg2+ and polyamines in the cell that is critical for viability. While Mg2+ and polyamines compensate for one another, too little of both or too much of both is lethal. After cytoplasmic Mg2+ levels are reestablished, polyamines must be exported to avoid the toxic effects of excess divalent cations.

Identification of Small-Molecule Inhibitors of the Salmonella FraB Deglycase Using a Live-Cell Assay

Nontyphoidal salmonellosis is one of the most significant foodborne diseases in the United States and globally. There are no vaccines available for human use to prevent this disease, and only broad-spectrum antibiotics are available to treat complicated cases of the disease. However, antibiotic resistance is on the rise and new therapeutics are needed. We previously identified the Salmonella fraB gene, that mutation of causes attenuation of fitness in the murine gastrointestinal tract. The FraB gene product is encoded in an operon responsible for the uptake and utilization of fructose-asparagine (F-Asn), an Amadori product found in several human foods. Mutations in fraB cause an accumulation of the FraB substrate, 6-phosphofructose-aspartate (6-P-F-Asp), which is toxic to Salmonella. The F-Asn catabolic pathway is found only in the nontyphoidal Salmonella serovars, a few Citrobacter and Klebsiella isolates, and a few species of Clostridium; it is not found in humans. Thus, targeting FraB with novel antimicrobials is expected to be Salmonella specific, leaving the normal microbiota largely intact and having no effect on the host. We performed high-throughput screening (HTS) to identify small-molecule inhibitors of FraB using growth-based assays comparing a wild-type Salmonella and a Δfra island mutant control. We screened 224,009 compounds in duplicate. After hit triage and validation, we found three compounds that inhibit Salmonella in an fra-dependent manner, with 50% inhibitory concentration (IC50) values ranging from 89 to 150 μM. Testing these compounds with recombinant FraB and synthetic 6-P-F-Asp confirmed that they are uncompetitive inhibitors of FraB with Ki' (inhibitor constant) values ranging from 26 to 116 μM. IMPORTANCE Nontyphoidal salmonellosis is a serious threat in the United States and globally. We have recently identified an enzyme, FraB, that when mutated renders Salmonella growth defective in vitro and unfit in mouse models of gastroenteritis. FraB is quite rare in bacteria and is not found in humans or other animals. Here, we have identified small-molecule inhibitors of FraB that inhibit the growth of Salmonella. These could provide the foundation for a therapeutic to reduce the duration and severity of Salmonella infections.

The Prolonged Treatment of Salmonella enterica Strains with Human Serum Effects in Phenotype Related to Virulence

Salmonella enterica as common pathogens of humans and animals are good model organisms to conduct research on bacterial biology. Because these bacteria can multiply in both the external environments and in the living hosts, they prove their wide adaptability. It has been previously demonstrated that prolonged exposition of Salmonella serotype O48 cells to normal human serum led to an increase in resistance to sera in connection with the synthesis of very long O-antigen. In this work, we have studied the phenotype connected to virulence of Salmonella enterica strains that were subjected to consecutive passages in 50% human serum from platelet-poor plasma (SPPP). We found that eight passages in SPPP may not be enough for the bacteria to become serum-resistant (S. Typhimurium ATCC 14028, S. Senftenberg). Moreover, C1q and C3c complement components bound to Salmonellae (S. Typhimurium ATCC 14028, S. Hammonia) membrane proteins, which composition has been changed after passaging in sera. Interestingly, passages in SPPP generated genetic changes within gene fljB, which translated to cells’ motility (S. Typhimurium ATCC 14028, S. Erlangen). One strain, S. Hammonia exposed to a serum developed a multi-drug resistance (MDR) phenotype and two S. Isaszeg and S. Erlangen tolerance to disinfectants containing quaternary ammonium salts (QAS). Furthermore, colonial morphotypes of the serum adaptants were similar to those produced by starter cultures. These observations suggest that overcoming stressful conditions is manifested on many levels. Despite great phenotypic diversity occurring after prolonged exposition to SPPP, morphotypes of colonies remained unchanged in basic media. This work is an example in which stable morphotypes distinguished by altered virulence can be confusing during laboratory work with life-threatening strains.

Prevalence, serotype, and antimicrobial resistance profiles of children infected with Salmonella in Guangzhou, southern China, 2016-2021

Purpose

Salmonella infection is a key global public health concern and has lead to an increased economic burden on society. We investigated the epidemiological characteristics and antimicrobial resistance profiles of clinically isolated Salmonella strains in Guangzhou Women and Children's Medical Center.

Patients and methods

This was a retrospective study of 1,338 Salmonella strains collected from children in Guangzhou Women and Children's Medical Center during 2016 to 2021.

Results

The results revealed that 1,338 cases of Salmonella were mainly isolated from feces and blood samples. The age distribution was dominated by infants under 3 years old. The seasonal distribution was high in summer and autumn. 48 serotypes were detected, and S. typhimurium (78.7%) was the predominant serogroup. The results of antimicrobial susceptibility showed that the highest resistance was observed in ampicillin (84.5%), while lower resistance was observed in piperacillin/tazobactam, cefoperazone/sulbactam and ciprofloxacin. The antimicrobial resistance rate of fecal isolates was higher than that of blood isolates. The five-year average detection rate of multi-drug resistant Salmonella was 8.5% (114/1338) and the MDR rate of S. typhimurium was the lowest (6.9%; 73/1053).

Conclusion

We concluded that antibacterial treatment should be carefully selected according to serotype and antimicrobial sensitivity results in children. Antimicrobial resistance monitoring for multi-drug resistant Salmonella is still required.

In vitro Efficacy Evaluation of Leading Brands of Ciprofloxacin Tablets Found in Bishoftu City Against Salmonella Isolates, Central Ethiopia

Purpose

Salmonella Enteritidis (SE) and Salmonella Typhimurium (STM) are the serovars most frequently associated with human illness. Ciprofloxacin is most widely used to manage cases in adults. The present study aimed to evaluate the in vitro antibacterial activity of leading brands of ciprofloxacin (tablets) marketed in Bishoftu city against SE and STM serovars, and field isolates of Salmonella (non-serotyped) from dairy milk in central Ethiopia.

Methods

Five most widely prescribed ciprofloxacin brands (A-E) were subjected to in vitro efficacy evaluation against Salmonella isolates by using the disc diffusion method. The zone of inhibition (ZI) of the tested brands was compared with the standard disc and interpreted as susceptible, intermediate, and resistant.

Results

Out of 27 replicates (SE, STM, and field Salmonella isolates each = 9) tested for efficacy, the result revealed the mean ZI of the brands varies for all tested isolates (p < 0.05). The highest mean was recorded for Brand E (24.7±0.71, 24.3±0.50, and 19.5±2.69) and lowest for Brand A (22.0±0.87, 21.0±0.87, and 10.7±1.4) for field Salmonella isolates, STM and SE, respectively. All SE were resistant to four brands (Brand A-D) whereas 67% and 33% of them were resistant and intermediate to Brand E, respectively. Similarly, 33% of STM were resistant to Brand A while all the STM were intermediate to other brands. Furthermore, all non-serotyped field isolates of Salmonella were intermediate to all five tested ciprofloxacin brands with variable ranges of mean of ZI (p<0.05).

Conclusion

The study revealed that Brand E was found to have relatively better efficacy against SE than other brands. The current study warrants a need for periodic surveillance of both the quality and efficacy of antibiotics to improve patient well-being and minimize the risk of antimicrobial resistance.

Determination of MIC, MPC, and MSW of Ilex paraguariensis against non-typhoidal Salmonella with identification of the mechanisms of resistance and pathogenicity factors

This study investigated the antibacterial activity of the aqueous extract of Ilex paraguariensis against 32 different strains of nontyphoidal Salmonella (NTS) through the determination of the minimum inhibitory concentration (MIC), mutant prevention concentration (MPC), and mutant selection window (MSW) and the detection of virulence genes by multiplex PCR assays. The MIC values of Ilex paraguariensis against Salmonella spp. strains varied between 0.78 mg/ml and 6.25 mg/ml with a MIC90 of 3.12 mg/ml. The highest MPC in this study was 48 mg/ml yielding a mutant selection window of 41.75 mg/ml. The MSW values of the remaining strains varied between 1.56 and 8.87 mg/ml. Genes of pathogenicity detected in Salmonella spp. isolates were most commonly the stn, sdiA, invA, sopB, invH, and sopE genes. The antibacterial activity of yerba mate extract was not affected by the antimicrobial resistance patterns or pathogenicity genes expressed. More work is needed to identify the active antibacterial compound(s) responsible for the antibacterial activity.

Salmonella spp. in Aquaculture: An Exploratory Analysis (Integrative Review) of Microbiological Diagnoses between 2000 and 2020

The present study aimed to characterize, through descriptive statistics, data from scientific articles selected in a systematic integrative review that performed a microbiological diagnosis of Salmonella spp. in aquaculture. Data were obtained from research articles published in the BVS, Scielo, Science Direct, Scopus and Web of Science databases. The selected studies were published between 2000 and 2020 on samples of aquaculture animal production (fish, shrimp, bivalve mollusks, and other crustaceans) and environmental samples of aquaculture activity (farming water, soil, and sediments). After applying the exclusion criteria, 80 articles were selected. Data such as country of origin, categories of fish investigated, methods of microbiological diagnosis of Salmonella spp., sample units analyzed and most reported serovars were mined. A textual analysis of the word cloud and by similarity and descending hierarchical classification with the application of Reinert's algorithm was performed using R® and Iramuteq® software. The results showed that a higher percentage of the selected articles came from Asian countries (38.75%). Fish was the most sampled category, and the units of analysis of the culture water, muscle and intestine were more positive. The culture isolation method is the most widespread, supported by more accurate techniques such as PCR. The most prevalent Salmonella serovars reported were S. Typhimurium, S. Weltevreden and S. Newport. The textual analysis showed a strong association of the terms "Salmonella", "fish" and "water", and the highest hierarchical class grouped 25.4% of the associated text segments, such as "aquaculture", "food" and "public health". The information produced characterizes the occurrence of Salmonella spp. in the aquaculture sector, providing an overview of recent years. Future research focusing on strategies for the control and prevention of Salmonella spp. in fish production are necessary and should be encouraged.

Multiplex PCR Assay for Clade Typing of Salmonella enterica Serovar Enteritidis

Salmonella enterica serovar Enteritidis is one of the most commonly reported serovars of nontyphoidal Salmonella causing human disease and is responsible for both gastroenteritis and invasive nontyphoidal Salmonella (iNTS) disease worldwide. Whole-genome sequence (WGS) comparison of Salmonella Enteritidis isolates from across the world has identified three distinct clades, global epidemic, Central/East African, and West African, all of which have been implicated in epidemics: the global epidemic clade was linked to poultry-associated gastroenteritis, while the two African clades were related to iNTS disease. However, the distribution and epidemiology of these clades across Africa are poorly understood because identification of these clades currently requires whole-genome sequencing capacity. Here, we report a sensitive, time- and cost-effective real-time PCR assay capable of differentiating between the Salmonella Enteritidis clades to facilitate surveillance and to inform public health responses. The assay described here is limited to previously confirmed S. Enteritidis isolates. IMPORTANCE Challenges in the diagnosis and treatment of invasive Salmonella Enteritidis bloodstream infections in sub-Saharan Africa are responsible for a case fatality rate of approximately 15%. It is important to identify distinct clades of S. Enteritidis in diagnostic laboratories in the African setting to determine the different health outcomes associated with particular outbreaks. Here, we describe the development of a high-quality molecular classification assay for clade typing of S. Enteritidis that is ideal for use in public health laboratories in resource-limited settings.

Prevalence and Antimicrobial Resistance of Salmonella in Poultry Products in Central Ethiopia

Salmonellosis is a bacterial infection caused by salmonella, a member of the Enterobacteriaceae family. From December 2021 to May 2021, a cross-sectional study was carried out to isolate Salmonella from poultry farms in the towns of Bishoftu and Adama and to determine the antimicrobial susceptibility frequency of the isolates. A total of 384 samples were tested for the presence of Salmonella, including 259 feces, 56 eggs, and 69 types of meat, using the ISO, 2002 standard procedures. The raw data were organized, coded, and entered into an Excel spreadsheet before being analyzed with STATA via descriptive analysis with chi-square. From 384 collected samples, 62 (16.15%) isolates were obtained, with 9.9%, 3.65, and 2.6% found in feces, eggs, and meat, respectively. Statistically, there was a significant difference between breeds (p value = 0.036). Bovines had the highest prevalence (32.83%), while Saso had the lowest (30.81%). The variation within each sample type, housing condition, and age group was not statistically significant (p value >0.05). Antimicrobial resistance was found in 29 (96.77%) of the isolates. Ampicillin and sulphamethoxazole-trimethoprim were effective against all isolates. Salmonella was isolated from various locations, sample types, ages, and breeds, indicating a wider distribution. Salmonellosis detection isolates suggested that it could be an emerging poultry and public health issue. As a result, future research should concentrate on isolating and identifying salmonella from poultry in backyard systems and comparing it to that of an intensive farm, as well as molecular characterization for serotyping and genetic studies, as well as genes responsible for salmonella pathogenicity and drug resistance.

Emergence, Dissemination and Antimicrobial Resistance of the Main Poultry-Associated Salmonella Serovars in Brazil

Simple Summary

Salmonellosis is a human and animal disease caused by Salmonella, a bacterial genus classified into different species, subspecies, and serological variants (serovars) according to adaptation to one or more different hosts (animals and humans), pathogenicity profiles, and antigenic properties. Some specific Salmonella serovars can spread more easily in the enteric microbiota of avian species, often causing disease in birds and/or being transmitted to humans through food (such as chicken and eggs). Antimicrobial resistance (AMR) has also been reported in poultry-associated Salmonella isolates due to the widespread use of antimicrobials on farms. The availability of comprehensive data on the emergence and spread of Salmonella serovars, as well as their AMR profiles in farms and food products in Brazil (a major producer of poultry in the World), is necessary to understand their relevance in all avian production chains and also occurrence in poultry-derived foods. This article aims to provide an overview of the genus Salmonella and the main serovars that emerged in Brazilian poultry over time (Gallinarum, Typhimurium, Enteritidis, Heidelberg, and Minnesota), reviewing the scientific literature and suggesting more effective prevention and control for the future.

Abstract

Salmonella infects poultry, and it is also a human foodborne pathogen. This bacterial genus is classified into several serovars/lineages, some of them showing high antimicrobial resistance (AMR). The ease of Salmonella transmission in farms, slaughterhouses, and eggs industries has made controlling it a real challenge in the poultry-production chains. This review describes the emergence, dissemination, and AMR of the main Salmonella serovars and lineages detected in Brazilian poultry. It is reported that few serovars emerged and have been more widely disseminated in breeders, broilers, and layers in the last 70 years. Salmonella Gallinarum was the first to spread on the farms, remaining as a concerning poultry pathogen. Salmonella Typhimurium and Enteritidis were also largely detected in poultry and foods (eggs, chicken, turkey), being associated with several human foodborne outbreaks. Salmonella Heidelberg and Minnesota have been more widely spread in recent years, resulting in frequent chicken/turkey meat contamination. A few more serovars (Infantis, Newport, Hadar, Senftenberg, Schwarzengrund, and Mbandaka, among others) were also detected, but less frequently and usually in specific poultry-production regions. AMR has been identified in most isolates, highlighting multi-drug resistance in specific poultry lineages from the serovars Typhimurium, Heidelberg, and Minnesota. Epidemiological studies are necessary to trace and control this pathogen in Brazilian commercial poultry production chains.

Impact of Antibiotics as Waste, Physical, Chemical, and Enzymatical Degradation: Use of Laccases

The first traces of Tetracycline (TE) were detected in human skeletons from Sudan and Egypt, finding that it may be related to the diet of the time, the use of some dyes, and the use of soils loaded with microorganisms, such as Streptomyces spp., among other microorganisms capable of producing antibiotics. However, most people only recognise authors dating between 1904 and 1940, such as Ehrlich, Domagk, and Fleming. Antibiotics are the therapeutic option for countless infections treatment; unfortunately, they are the second most common group of drugs in wastewaters worldwide due to failures in industrial waste treatments (pharmaceutics, hospitals, senior residences) and their irrational use in humans and animals. The main antibiotics problem lies in delivered and non-prescribed human use, use in livestock as growth promoters, and crop cultivation as biocides (regulated activities that have not complied in some places). This practice has led to the toxicity of the environment as antibiotics generate eutrophication, water pollution, nutrient imbalance, and press antibiotic resistance. In addition, the removal of antibiotics is not a required process in global wastewater treatment standards. This review aims to raise awareness of the negative impact of antibiotics as residues and physical, chemical, and biological treatments for their degradation. We discuss the high cost of physical and chemical treatments, the risk of using chemicals that worsen the situation, and the fact that each antibiotic class can be transformed differently with each of these treatments and generate new compounds that could be more toxic than the original ones; also, we discuss the use of enzymes for antibiotic degradation, with emphasis on laccases.

Cefotaxime Exposure Selects Mutations within the CA-Domain of envZ Which Promote Antibiotic Resistance but Repress Biofilm Formation in Salmonella

Cephalosporins are important beta lactam antibiotics, but resistance can be mediated by various mechanisms including production of beta lactamase enzymes, changes in membrane permeability or active efflux. We used an evolution model to study how Salmonella adapts to subinhibitory concentrations of cefotaxime in planktonic and biofilm conditions and characterized the mechanisms underpinning this adaptation. We found that Salmonella rapidly adapts to subinhibitory concentrations of cefotaxime via selection of multiple mutations within the CA-domain region of EnvZ. We showed that changes in this domain affect the ATPase activity of the enzyme and in turn impact OmpC, OmpF porin expression and hence membrane permeability leading to increased tolerance to cefotaxime and low-level resistance to different classes of antibiotics. Adaptation to cefotaxime through EnvZ also resulted in a significant cost to biofilm formation due to downregulation of curli. We assessed the role of the mutations identified on the activity of EnvZ by genetic characterization, biochemistry and in silico analysis and confirmed that they are responsible for the observed phenotypes. We observed that sublethal cefotaxime exposure selected for heterogeneity in populations with only a subpopulation carrying mutations within EnvZ and being resistant to cefotaxime. Population structure and composition dynamically changed depending on the presence of the selection pressure, once selected, resistant subpopulations were maintained even in extended passage without drug. IMPORTANCE Understanding mechanisms of antibiotic resistance is crucial to guide how best to use antibiotics to minimize emergence of resistance. We used a laboratory evolution system to study how Salmonella responds to cefotaxime in both planktonic and biofilm conditions. In both contexts, we observed rapid selection of mutants within a single hot spot within envZ. The mutations selected altered EnvZ which in turn triggers changes in porin production at the outer membrane. Emergence of mutations within this region was repeatedly observed in parallel lineages in different conditions. We used a combination of genetics, biochemistry, phenotyping and structural analysis to understand the mechanisms. This data show that the changes we observe provide resistance to cefotaxime but come at a cost to biofilm formation and the fitness of mutants changes greatly depending on the presence or absence of a selective drug. Studying how resistance emerges can inform selective outcomes in the real world.

Salmonella Enteritidis GalE Protein Inhibits LPS-Induced NLRP3 Inflammasome Activation

Microbial infection can trigger the assembly of inflammasomes and promote secretion of cytokines, such as IL-1β and IL-18. It is well-known that Salmonella modulates the activation of NLRC4 (NLR family CARD domain-containing protein 4) and NLRP3 (NLR family pyrin domain-containing 3) inflammasomes, however the mechanisms whereby Salmonella avoids or delays inflammasome activation remain largely unknown. Therefore, we used Salmonella Enteritidis C50336ΔfliC transposon library to screen for genes involved in modulating inflammasomes activation. The screen revealed the galactose metabolism-related gene galE to be essential for inflammasome activation. Here, we found that inflammasome activation was significantly increased in J774A.1 cells or wild-type bone marrow-derived macrophages (BMDMs) during infection by ΔfliCΔgalE compared to cells infected with ΔfliC. Importantly, we found that secretion of IL-1β was Caspase-1-dependent, consistent with canonical NLRP3 inflammasome activation. Furthermore, the virulence of ΔfliCΔgalE was significantly decreased compared to ΔfliC in a mouse model. Finally, RNA-seq analysis showed that multiple signaling pathways related to the inflammasome were subject to regulation by GalE. Taken together, our results suggest that GalE plays an important role in the regulatory network of Salmonella evasion of inflammasome activation.

Salmonella typhimurium as a causative agent of spontaneous bacterial peritonitis

Spontaneous bacterial peritonitis (SBP) is a common complication of liver cirrhosis and abdominal ascites, usually caused by organisms from the Enterobacteriaceae family. A woman in her 40s with a history of alcoholic liver cirrhosis presented to the hospital with dyspnoea, abdominal distention and diffuse abdominal pain. She was found to have sepsis and abdominal ascites, with elevated ascitic fluid neutrophil counts consistent with SBP. Culture of ascitic fluid revealed Salmonella typhimurium Further investigation revealed that the patient shared her home with a pet bearded dragon, a reptile known to carry Salmonella spp. She was treated with intravenous ceftriaxone and oral ciprofloxacin for a total of 14 days. S. typhimurium, likely transmitted to the patient from the pet reptile, is a rare pathogen in SBP and highlights the importance of environmental exposures in the management of this condition.

Novel multiplex PCR assays for rapid identification of Salmonella serogroups B, C1, C2, D, E, S. enteritidis, and S. typhimurium

Foodborne illnesses caused by Salmonella represent a significant public health problem worldwide. The aim of this study was to establish multiplex PCR (mPCR) for the rapid identification of Salmonella serogroups B, C1, C2, D, and E as well as for the serovars enteritidis and typhimurium. Employing pan-genome analysis and PCR verification, B-rfbJ, C1-9679, C2-pimB, D-rfbJ, E-rfbC, and four genes (SE18636, SE16574, SE2599, and SE13329) were identified as specific target genes for Salmonella serogroups B, C1, C2, D, E, and S. enteritidis, respectively. Thereafter, three novel mPCR assays (one of 3-mPCR and two of 2-mPCR) were successfully developed to identify these bacteria based on the target genes and another S. typhimurium-specific STM4495 gene. The primers targeting C1-9679, C2-pimB, and E-rfbC genes specific to the serogroups C1, C2, and E, respectively, constituted a 3-mPCR, while the other two 2-mPCRs, respectively, consisting primers specific to serogroup D and S. enteritidis (D-rfbJ and SE16574), and serogroup B and S. typhimurium-specific primers (B-rfbJ and STM4495), were also designed. The specificity of each mPCR was further evaluated by using non-target strains. The detection limits of mPCRs were approximately 10³-10⁴ CFU mL^-1 in pure culture and 10⁴-10⁵ CFU g^-1 in spiked chicken meat. In addition, mPCR assays could correctly detect target Salmonella in food samples. These results suggest that specific targets could be mined efficiently through a pan-genome analysis tool, and the novel mPCR assays developed in this study offer a promising technique for rapid and accurate detection of five serogroups of Salmonella (B, C1, C2, D, and E) and two serovars (S. enteritidis and S. typhimurium).

Changes in physiological states of Salmonella Typhimurium measured by qPCR with PMA and DyeTox13 Green Azide after pasteurization and UV treatment

Diarrheal diseases caused by Salmonella pose a major threat to public health, and assessment of bacterial viability is critical in determining the safety of food and drinking water after disinfection. Viability PCR could overcome the limitations of traditional culture-dependent methods for a more accurate assessment of the viability of a microbial sample. In this study, the physiological changes in Salmonella Typhimurium induced by pasteurization and UV treatment were evaluated using a culture-based method, RT-qPCR, and viability PCR. The plate count results showed no culturable S. Typhimurium after the pasteurization and UV treatments, while viability PCR with propidium monoazide (PMA) and DyeTox13-qPCR indicated that the membrane integrity of S. Typhimurium remained intact with no metabolic activity. The RT-qPCR results demonstrated that invasion protein (invA) was detectable in UV-treated cells even though the log2-fold change ranged from - 2.13 to - 5.53 for PMA treatment. However, the catalytic activity gene purE was under the detection limit after UV treatment, indicating that most Salmonella entered metabolically inactive status after UV disinfection. Also, viability PCRs were tested with artificially contaminated eggs to determine physiological status on actual food matrices. DyeTox13-qPCR methods showed that most Salmonella lost their metabolic activity but retained membrane integrity after UV disinfection. RT-qPCR may not determine the physiological status of Salmonella after UV disinfection because mRNA could be detectable in UV-treated cells depending on the choice of target gene. Viability PCR demonstrated potential for rapid and specific detection of pathogens with physiological states such as membrane integrity and metabolic activity.Key Points• Membrane integrity of Salmonella remained intact with no metabolic activity after UV.• mRNA could be detectable in UV-treated cells depending on the choice of target gene.• Viability PCR could rapidly detect specific pathogens with their physiological states.

Paediatric enteric fever in Brussels: a case series over 16 years

Enteric fever (EF) is a major public health problem and a witness of the global health disparities. It is caused by Salmonella enterica serovar Typhi (Salmonella ser. Typhi) and Salmonella enterica serovar Paratyphi A, B, C (Salmonella ser. Paratyphi) and is estimated to infect 12-26 million persons yearly. Paediatric data on enteric fever in Europe are scarce. A case series of EF was analysed to describe the clinical presentation, laboratory characteristics and diagnostic challenges identified in a paediatric population in Brussels. We performed a retrospective study of all lab-confirmed cases of enteric fever in children aged 0-15 years at two Brussels teaching hospitals, between January 2005 and December 2020. We reviewed age, gender, travel history, consultations before diagnosis, hospitalisation duration, clinical symptoms and laboratory findings. There were 34 positive isolates of S. typhi and S. paratyphi: 31 patients had positive blood culture, 1 patient had positive bone aspirate and 2 patients had positive stool culture (one was excluded for missing data). There were 20 girls (60%). Median age was 3.5 years (range 5 months to 14 years). Travel to EF endemic areas was present in 55% of patients. Diagnosis was delayed in 80% of children. Eosinopenia was present in 93% of the cohort. The patients had not received any preventive travel education or vaccination.  Conlusion: Enteric fever poses diagnostic challenges to clinicians. Eosinopenia in a febrile patient coming from the tropics should raise suspicion of EF. Travellers to endemic areas should be better educated about EF risks, and typhoid fever vaccination must be promoted. What is Known: • Enteric fever is a global public health problem and includes typhoid and paratyphoid fever. • Typhoid fever is vaccine preventable disease. Paratyphoid fever is not vaccine preventable. What is New: • Enteric fever diagnosis is very challenging in non-endemic settings, and a large proportion of patients may develop serious complications if they receive delayed management. Occurrence of small family clusters is possible and mandates education and monitoring of the families of enteric fever affected children. • We report that the widest majority of our enteric fever affected patients (69%) had aneosinophilia (zero eosinophil count), and almost all patients (93%) had eosinopaenia (less than 50 eosinophil count) during their bacteriaemic phase.

Isolation, identification and antimicrobial susceptibility profile of Salmonella isolated from poultry farms in Addis Ababa, Ethiopia

Background

Salmonella has been found to be the major cause of foodborne diseases and a serious public health problem in the world, with an increasing concern for the emergence and spread of antimicrobial‐resistant strains.

Method

A cross‐sectional study was conducted on poultry and poultry farms in Addis Ababa from February 2016 to April 2016 to determine the occurrence and evaluate the antimicrobial susceptibility profile of Salmonella isolates. A total of 200 samples consisting of the cloacal swab (n = 168), pooled litter (n = 12), hand swab (n = 8), pooled feed and water (n = 12) were collected separately from six poultry farms. The samples were examined for the presence of Salmonella through culturing on bacteriological media. Descriptive statistics, Pearson's Chi‐square (X²) and bivariate logistic regression were used in the analysis of the data. Accordingly, out of 200 samples, 23 (11.50%) were Salmonella positive, of which 21(12.50%) were in cloacal swab and 2(16.67%) in the pooled litter. There was no statistical association between the bacteriological status of sample type and Salmonella positivity (X² = 3.07, P = 0.545). However, there was a statistical association between farms and the rate of Salmonella isolation (X² = 22.21, P ≤ 0.00). The antimicrobial susceptibility testing for Salmonella isolates was conducted following the Kirby–Bauer disc diffusion method (1961).

Results

Out of 23 samples tested, 95.65% of them were resistant to at least one or more antimicrobials. Multiple drug resistances were observed for 69.56% of Salmonella isolates. The highest resistance (73.9%) was observed in kanamycin followed by tetracycline (65.2%) and streptomycin (56.3%). gentamycin was the most effective antibiotic (95.7%; sensitivity) followed by ciprofloxacin (78.3% sensitivity) and ampicillin (69.6% sensitivity.

Conclusion

This current study finding indicated that further detailed epidemiological and molecular studies are essential on the frequency and sources of acquisition of resistant genes.

Salmonellosis is an infectious and economically important disease of humans and animals caused by different Salmonella species.

Non-typhoidal, Non-paratyphoidal Salmonella Species Causing Sacroiliitis and Pyomyositis in a Healthy 19-Year-Old Athlete

Salmonella is a gram-negative bacterium, subdivided into typhoidal and non-typhoidal Salmonella. It is usually caused by eating raw or undercooked meat, poultry, eggs, or egg products. The clinical manifestations of Salmonella infection can be divided into five syndromes: enterocolitis (food poisoning), enteric (typhoid) fever, bacteremia/septicemia, focal infection, and a chronic carrier state, which is usually asymptomatic. The most common clinical presentation is diarrhea. Salmonella osteomyelitis occurs most frequently in patients with sickle-cell disease; other risk factors include other hemoglobinopathies, immunocompromised status, and chronic Salmonella carrier state. The incidence of Salmonella osteomyelitis/septic arthritis in otherwise healthy individuals is rare. The duration of symptoms can range from a few months to several years, and multifocal involvement occurs in 15% of reported cases of Salmonella osteomyelitis. The symptoms of Salmonella osteomyelitis are pain and variable swelling of the affected limb; high temperatures are rarely noted. Our patient is a 19-year-old boy with no known past medical history who presented with severe right-sided sacroiliitis with extensive surrounding osteomyelitis on both sides of the sacroiliac joint with non-typhoidal, non-paratyphoidal Salmonella bacteremia.

Antimicrobial Drug-Resistant Salmonella in Urban Cats: Is There an Actual Risk to Public Health?

The present study was undertaken to investigate the presence of Salmonella spp. in the faeces of client-owned cats in urban areas and to evaluate the risk that is posed to public health. Fresh faecal samples were collected directly from the rectums from 53 diarrhoeic and 32 non-diarrhoeic cats. The samples were individually screened for the presence of Salmonella spp. using standard methods and, in the case of positive findings, the resulting typical colonies were then biochemically confirmed using the VITEK^®2 automated system. Subsequently, all of the Salmonella spp. isolates were molecularly tested for the presence of the invA gene. All of the isolates were serotyped using the slide agglutination technique according to the White–Kauffmann–Le Minor scheme. The phenotypic antimicrobial susceptibility profile of the isolated strains was obtained from the VITEK^®2 system using specific cards from the Gram-negative bacteria. A total of 16 of the samples (18.82%) tested positive for Salmonella spp. according to conventional and molecular testing methods. Serotyping of the Salmonella isolates showed the presence of three serotypes, namely S. enteritidis (n = 9; 56.3%), S. typhimurium (n = 4; 25%), and S. kentucky (n = 3; 18.8%). All of the tested strains showed strong resistance towards cefazolin, cefepime, ceftazidime, and ceftriaxone. Additionally, resistance (listed in descending order of strength) was observed to trimethoprim/sulfamethoxazole (11/16; 68.8%), ampicillin (10/16; 62.5%), ampicillin/sulbactam (9/16; 56.3%), gentamicin (9/16; 56.3%), nitrofurantoin (8/16; 50.0%), and amikacin (5/16; 31.3%). No resistance was expressed against ciprofloxacin, ertapenem, imipenem, levofloxacin, piperacillin/tazobactam, and tobramycin. The results of this study highlight a substantial public health issue and medical concern, especially in vulnerable people, such as children, the elderly, and immunocompromised individuals.

Prevalence, probability, and outcomes of typhoidal/non-typhoidal Salmonella and malaria co-infection among febrile patients: a systematic review and meta-analysis

The geographical overlaps of malaria parasites and Salmonella spp. can lead to co-infection of these two pathogens, especially in the tropics where malaria is endemic. Moreover, few literatures suggested that malaria infection was associated with Salmonella bacteremia. Therefore, this study quantified pooled prevalence of typhoidal/non-typhoidal Salmonella (NTS) and probability of typhoidal/NTS and malaria co-infection among febrile patients. The systematic review protocol was registered at PROSPERO (CRD42021252322). Studies on co-infection of typhoidal/NTS and malaria were searched in PubMed, Scopus, and Web of Science. The risk of bias of the included studies was assessed using the checklist for analytical cross-sectional studies developed by the Joanna Briggs Institute. Meta-analyses on the following criteria were performed: (1) pooled prevalence of typhoidal/NTS and malaria co-infection among febrile patients, (2) pooled prevalence of typhoidal/NTS among malaria patients, (3) pooled prevalence of malaria infections among patients with Salmonella spp. infection, and (4) probability of typhoidal/NTS and malaria co-infection among febrile patients. Additionally, the case fatality rate and mean difference of malarial parasitemia between typhoidal/NTS and malaria co-infection and Plasmodium monoinfection were also determined. The subgroup analyses of typhoidal/NTS, regions (Africa and Asia), countries, time (publication year), characteristics of participants, and diagnostic tests for identifying Salmonella spp. were also conducted. A sensitivity test was performed to determine the robustness of the study outcomes. Publication bias among the included studies was evaluated using the funnel plot and Egger’s test. All analyses were performed using Stata version 15 (StataCorp LLC, Texas, USA) with a p-value < 0.05 indicating statistical significance. Eighty-one studies that met the eligibility criteria were included in the analyses. Of the 73,775 study participants, 4523 had typhoidal/NTS and malaria co-infections. The pooled prevalence rates of typhoidal/NTS and malaria co-infection among febrile patients were 14% (95% confidence interval [CI], 9–19%; I², 99.4%; 2971/17,720 cases) and 1% (95% CI 1–1%; I², 89.9%; 252/29,081 cases) using the Widal test and culture methods for identifying Salmonella spp., respectively. The pooled prevalence rates of typhoidal/NTS infection among patients with malaria were 31% (95% CI 23–39%; I², 99.5%; 3202/19,208 cases) and 3% (95% CI 2–3%; I², 86.8%; 407/40,426 cases) using the Widal test and culture methods for identifying Salmonella spp., respectively. The pooled prevalence rates of malaria infection among patients with typhoidal/NTS were 17% (95% CI 6–29%; I², 33.3%; 13/75 cases) and 43% (95% CI 32–53%; I², 89.1%; 287/736 cases), respectively. Malaria infection was associated with typhoidal/NTS in children aged < 15 years (p < 0.0001; odds ratio, 0.36; 95% CI 0.23–0.58; I², 73.9%; 3188/43,212 cases). The case fatality rate in patients with malaria and NTS co-infections was 16% (95% CI 9–24%; I², 89.1%; 18/103 cases). From the view of the present study, the inappropriate use of the Widal test for Salmonella spp. diagnosis can overestimate the prevalence of typhoidal/NTS and malaria co-infections. Malaria infection associated with typhoidal/NTS in children and the high case fatality rates among few patients with co-infections were highlighted. Future prospective longitudinal studies using the appropriate and confirmatory dsiagnosis for Salmonella spp. infections are highly recommended to ensure the real prevalence of co-infection and highlight the outcome of co-infection for providing adequate treatment in febrile patients who live in areas where malaria is endemic, such as tropical Africa and India.

A rare case report of enteric fever causing gallbladder perforation

Introduction and importance

Enteric fever is one of the major public health problems mainly in developing countries. Gallbladder perforation is very unusual. Enteric fever rarely causes gallbladder perforation. We report a case of gallbladder perforation due to enteric fever in an adult patient.

Case presentation

A 50-year-old female without any medical illness presented with a history of intermittent fever for two weeks and three days duration of severe abdominal pain. Upper abdominal tenderness and guarding were found in the abdominal examination. Ultrasonography showed thickening of the gallbladder wall and pericholecystic fluid collection. Magnetic resonance cholangiopancreatography revealed a distended gallbladder with sludge, diffuse wall thickening, and contained perforation with a mild amount of free fluid seen in the abdomen. With the diagnosis of type II gallbladder perforation, percutaneous ultrasonography-guided drainage was done. The culture of bile revealed positivity for Salmonella Typhi. Intra-venous antibiotic (ceftriaxone and gentamicin) was administered for 14 days. Four weeks later, cholecystectomy with peritoneal lavage was done. She was discharged on the 8th postoperative day.

Clinical discussion

Preoperative diagnosing of gallbladder perforation is challenging. The accurate treatment and precise timing of the surgery remain important. In most cases, cholecystectomy and abdominal lavage are adequate to treat gallbladder perforation.

Conclusions

Gallbladder perforation is a life-threatening surgical problem. The clinician should have a high index of awareness about this unusual surgical entity due to enteric fever and early diagnosis with prompt surgical intervention is necessary to improve patient outcomes.

•

Enteric fever is one of the major public health problems mainly in developing countries.

•

Gallbladder perforation is a very uncommon complication of enteric fever.

•

Awareness of this rare entity due to enteric fever is important for prompt timely management for better patient outcomes.

Presence of Tetracycline and Sulfonamide Resistance Genes in Salmonella spp.: Literature Review

Tetracyclines and sulfonamides are broad-spectrum antibacterial agents which have been used to treat bacterial infections for over half a century. The widespread use of tetracyclines and sulfonamides led to the emergence of resistance in a diverse group of bacteria. This resistance can be studied by searching for resistance genes present in the bacteria responsible for different resistance mechanisms. Salmonella is one of the leading bacteria causing foodborne diseases worldwide, and its resistance to tetracyclines and sulfonamides has been widely reported. The literature review searched the Virtual Health Library for articles with specific data in the studied samples: the resistance genes found, the primers used in PCR, and the thermocycler conditions. The results revealed that Salmonella presented high rates of resistance to tetracycline and sulfonamide, and the most frequent samples used to isolate Salmonella were poultry and pork. The tetracycline resistance genes most frequently detected from Salmonella spp. were tetA followed by tetB. The gene sul1 followed by sul2 were the most frequently sulfonamide resistance genes present in Salmonella. These genes are associated with plasmids, transposons, or both, and are often conjugative, highlighting the transference potential of these genes to other bacteria, environments, animals, and humans.

Genetic interference exerted by Salmonella-delivered CRISPR/Cas9 significantly reduces the pathological burden caused by Marek's disease virus in chickens

Efficient in vivo delivery of a CRISPR/Cas9 plasmid is of paramount importance for effective therapy. Here, we investigated the usability of Salmonella as a plasmid carrier for in vivo therapy against virus-induced cancer using Marek’s disease virus (MDV) as a model for study in chickens. A green fluorescent protein-expressing CRISPR/Cas9 plasmid encoding the virulence gene pp38 was constructed against Marek’s disease virus. Therapeutic plasmids were transformed into Salmonella carrying lon and sifA gene deletions. The animals in 5 groups were intraperitoneally inoculated with phosphate-buffered saline, vector control, or Salmonella before or after MDV infection, or left uninfected as a naïve control. Therapeutic effectiveness was evaluated by observing disease outcomes and the viral copy number in peripheral blood mononuclear cells. The efficacy of plasmid delivery by Salmonella was 13 ± 1.7% in the spleen and 8.0 ± 1.8% in the liver on the 6^th day post-infection. The Salmonella-treated groups showed significant resistance to MDV infection. The maximum effect was observed in the group treated with Salmonella before MDV infection. None of the chickens fully recovered; however, the results suggested that timely delivery of Salmonella could be effective for in vivo CRISPR/Cas9-mediated genetic interference against highly pathogenic MDV. The use of Salmonella in CRISPR systems provides a simpler and more efficient platform for in vivo therapy with CRISPR than the use of conventional in vivo gene delivery methods and warrants further development.

Occurrence and distribution of fecal indicators and pathogenic bacteria in seawater and Perna perna mussel in the Gulf of Annaba (Southern Mediterranean)

The identification of fecal contamination in coastal marine ecosystems is one of the main requirements for evaluation of potential risks to human health. The objective of this study was to investigate the occurrence and distribution of fecal indicators and pathogenic bacteria in seawaters and mussels collected monthly during a period of 1 year from four different sites in Northeastern Algeria (sites S1 to S4), through biochemical and molecular analyses. Our research is the first to use molecular analysis to unambiguously identify the potentially pathogenic bacteria present in Algerian Perna perna mussels. The obtained results revealed that the levels of fecal indicator bacteria (FIB) from both P. perna and seawater samples largely exceeded the permissible limits at S2 and S3. This is mainly related to their location close to industrial and coastal activity zones, which contain a mixture of urban, agricultural, and industrial pollutants. Besides, P. perna collected from all sites were severalfold more contaminated by FIB than seawater samples, primarily during the warm season of the study period. Biochemical and molecular analyses showed that isolated bacteria from both seawater and mussels were mainly potentially pathogenic species such as E. coli, Salmonella spp., Staphylococcus spp., Klebsiella spp., Pseudomonas spp., and Proteus spp.

Analysis of the assessment of antimicrobial susceptibility. Non-typhoid Salmonella in meat and meat products as model (systematic review)

BACKGROUND

The scientific publications of antimicrobial susceptibilities and resistance must be precise, with interpretations adjusted to the standard. In this frame, knowledge of antimicrobial resistance is fundamental in pathogenic microorganisms such as Salmonella spp., known for many annual deaths worldwide. The objective of this work was to compare the interpretation of standards, the concentrations, and the breakpoints, to study antimicrobial resistance in Non-Typhoidal Salmonella (NTS) isolated from beef, pork, and chicken meat, meat products, and propose additional considerations that improve the use and usefulness of published results.

RESULTS

After refining the search based on meeting the inclusion and exclusion criteria, 48 papers were selected. In 33 (68.8%) of them, the disc diffusion method was used, in 11 (22.9%) the MIC determination method, and in 4 (8.33%) were used both. In 24 (50%) of the articles, the selection of a different (correct) standard could have had an impact on the interpretation of antimicrobial susceptibility, which observed when considering three scenarios, i) comparison between the year of the isolation versus the implemented standard, ii) comparison between the year of submission versus implemented standard and iii) comparison between the year of publication versus implemented standard.

CONCLUSIONS

The most frequent scenario was the inadequate selection of standards, indicating that some studies had not ensured that applied standards kept in line with the date of isolation, date of publication and interpretation of susceptibilities. We proposed 2 years for standards use for resistance and multi-resistance interpretations. On the other hand, we invite researchers to publish their results in the shortest possible time, and editors and reviewers of scientific journals to prioritise these types of studies and verify the correspondence between the standard cited and the one used and the one to be taken into account.

Antimicrobial Resistance of Non-Typhoid Salmonella in Meat and Meat Products

Salmonella enterica serovars are associated with numerous annual deaths worldwide and are responsible for a large number of foodborne diseases. Within this frame of reference, knowledge of antimicrobial susceptibility represents the fundamental approach of most Salmonella treatments. Therefore, scientific publications of antimicrobial susceptibilities and resistance must be precise, with interpretations adjusted to a particular standard. Hence, the three objectives in this study were: (i) to describe the frequency of antimicrobial-resistant isolates of Non-Typhoidal Salmonella (NTS) isolated from beef, pork, chicken meat, and other meat products; (ii) to describe the distribution of serovars and their multi-resistance to antibiotics for clinical use (veterinary and human) between 1996 and 2019; and (iii) to propose additional considerations that could improve the use and usefulness of the published results. Our results determined that the predominant isolates came from poultry. Enteritidis and Typhimurium were the most reported serovars by MIC (with both having the highest resistance to TET) while the lowest resistance was to CIP and CRO for Enteritidis and Typhimurium, respectively. The multi-resistance pattern AMP AMC CEP GEN KAN STR TET was the most frequently observed pattern by MIC in Montevideo and Seftenberg, while, for disc diffusion, the pattern AMP STR TET was the most frequent in the Bredeney serotype. In conclusion, researchers should carry out homogeneous sampling procedures, identify the types of the samples, use standard identification methods, and employ appropriate standards for antimicrobial susceptibility interpretation. Additionally, there is also a need for all WHO members to comply with the WHA 73.5 resolution. Our final recommendation is for all producers to reduce antibiotic prophylactic use.

Antimicrobial and insecticidal effects of essential oil and plant extracts of Myrcia oblongata DC in pathogenic bacteria and Alphitobius diaperinus

The secondary metabolism products of plants have influenced great economic interest, given their chemical diversity and biological activities. Because of this, this study evaluates the phytochemical composition, antimicrobial activity, insecticidal, and antioxidant activity of plant extracts and oil of Myrcia oblongata. Saponins, steroids, triterpenoids, tannins, and flavonoids were detected. The extracts showed antimicrobial capacity on the tested microorganisms, except for the methanolic extract, which showed no activity for P. mirabilis and S. enteritidis. Regarding the analysis of antioxidant compounds, the hexanic, ethyl acetate and acetone extracts showed higher antioxidant activities and also higher insecticidal performance on Alphitobius diaperinus larvae, resulting in 80% adult mortality. The results reported here show that there may be a relationship between antioxidant potential and the insecticidal effect of Myrcia oblongata DC. The components present in both the extract and the oil can be used as natural alternative to synthetic compounds in the biological control of parasites and pathogenic microorganisms.

Prevalence, Serovar, and Antimicrobial Resistance of Nontyphoidal Salmonella in Vegetable, Fruit, and Water Samples in Ho Chi Minh City, Vietnam

In this study, we investigated the prevalence, serovar distribution, and antimicrobial resistance pattern of Salmonella isolates from vegetable, fruit, and water samples in Ho Chi Minh City, Vietnam. Salmonella was detected in 75% (30/40), 57.1% (12/21), 17.5% (28/160), and 2.5% (1/40) of river water, irrigation water, vegetable, and ice water samples, respectively. However, no Salmonella was isolated from 160 fruit and 40 tap water samples examined. A total of 102 isolates obtained from 71 samples belonged to 34 different serovars, of which Salmonella Rissen was the most prevalent, followed by Salmonella London, Salmonella Hvittingfoss, and Salmonella Weltevreden. Certain Salmonella serovars such as Newport, Rissen, and Weltevreden were isolated from both vegetable and water samples. Antimicrobial resistance was most commonly observed against tetracycline (35.3%), followed by chloramphenicol (34.3%), ampicillin (31.4%), trimethoprim/sulfamethoxazole (23.5%), and nalidixic acid (10.8%). Of 102 isolates analyzed, 52 (51%) showed resistance to at least 1 antimicrobial class whereas 27 (26.5%) showed multidrug resistant (MDR) phenotype, being resistant to at least three different classes of antimicrobials. Determination of the presence and type of β-lactamase genes showed the cooccurrence of bla_TEM-1 and bla_CMY-2 in one Salmonella Agona isolate from a river water sample. Taken together, these data indicated that both environmental water and vegetables were contaminated with Salmonella, including MDR strains, and that environmental water used in irrigation might have been the source of Salmonella contamination in the vegetables.

Mass burial genomics reveals outbreak of enteric paratyphoid fever in the Late Medieval trade city Lübeck

Medieval Europe was repeatedly affected by outbreaks of infectious diseases, some of which reached epidemic proportions. A Late Medieval mass burial next to the Heiligen-Geist-Hospital in Lübeck (present-day Germany) contained the skeletal remains of more than 800 individuals who had presumably died from infectious disease. From 92 individuals, we screened the ancient DNA extracts for the presence of pathogens to determine the cause of death. Metagenomic analysis revealed evidence of Salmonella enterica subsp. enterica serovar Paratyphi C, suggesting an outbreak of enteric paratyphoid fever. Three reconstructed S. Paratyphi C genomes showed close similarity to a strain from Norway (1200 CE). Radiocarbon dates placed the disease outbreak in Lübeck between 1270 and 1400 cal CE, with historical records indicating 1367 CE as the most probable year. The deceased were of northern and eastern European descent, confirming Lübeck as an important trading center of the Hanseatic League in the Baltic region.

•

Salmonella enterica Paratyphi C detected in remains from a mass burial in Lübeck

•

Outbreak of enteric paratyphoid fever likely occurred in 1367 CE

•

Pathogen genomes showed close similarity to a strain from Norway (1200 CE)