Enhancing colistin efficacy against Salmonella infections with a quinazoline-based dual therapeutic strategy.

Colistin remains one of the last-resort therapies for combating infections caused by multidrug-resistant (MDR) Enterobacterales, despite its adverse nephro- and neuro-toxic effects. This study elucidates the mechanism of action of a non-antibiotic 4-anilinoquinazoline-based compound that synergistically enhances the effectiveness of colistin against Salmonella enterica. The quinazoline sensitizes Salmonella by deactivating intrinsic, mutational, and transferable resistance mechanisms that enable Salmonella to counteract the antibiotic impact colistin, together with an induced disruption to the electrochemical balance of the bacterial membrane. The attenuation of colistin resistance via the combined treatment approach also proves efficacious against E. coli, Klebsiella, and Acinetobacter strains. The dual therapy reduces the mortality of Galleria mellonella larvae undergoing a systemic Salmonella infection when compared to individual drug treatments. Overall, our findings unveil the potential of the quinazoline-colistin combined therapy as an innovative strategy against MDR bacteria.

Cananga oil inhibits Salmonella infection by mediating the homeostasis of purine metabolism and the TCA cycle.

ETHNOPHARMACOLOGY RELEVANCE: Cananga oil (CO) is derived from the flowers of the traditional medicinal plant, the ylang-ylang tree. As a traditional antidepressant, CO is commonly utilized in the treatment of various mental disorders including depression, anxiety, and autism. It is also recognized as an efficient antibacterial insecticide, and has been traditionally utilized to combat malaria and acute inflammatory responses resulting from bacterial infections both in vitro and in vivo. AIM OF THE STUDY: The objective of this study is to comprehensively investigate the anti-Salmonella activity and mechanism of CO both in vitro and in vivo, with the expectation of providing feasible strategies for exploring new antimicrobial strategies and developing novel drugs. METHODS: The in vitro antibacterial activity of CO was comprehensively analyzed by measuring MIC, MBC, growth curve, time-killing curve, surface motility, biofilm, and Live/dead bacterial staining. The analysis of the chemistry and active ingredients of CO was conducted using GC-MS. To examine the influence of CO on the membrane homeostasis of Salmonella, we conducted utilizing diverse techniques, including ANS, PI, NPN, ONPG, BCECF-AM, DiSC3(5), and scanning electron microscopy (SEM) analysis. In addition, the antibacterial mechanism of CO was analyzed and validated through metabolomics analysis. Finally, a mouse infection model of Salmonella typhimurium was established to evaluate the toxic side effects and therapeutic effects of CO. RESULTS: The antibacterial effect of CO is the result of the combined action of the main chemical components within its six (palmitic acid, α-linolenic acid, stearic acid, benzyl benzoate, benzyl acetate, and myristic acid). Furthermore, CO disrupts the balance of purine metabolism and the tricarboxylic acid cycle (TCA cycle) in Salmonella, interfering with redox processes. This leads to energy metabolic disorders and oxidative stress damage within the bacteria, resulting in bacterial shock, enhanced membrane damage, and ultimately bacterial death. It is worth emphasizing that CO exerts an effective protective influence on Salmonella infection in vivo within a non-toxic concentration range. CONCLUSION: The outcomes indicate that CO displays remarkable anti-Salmonella activity both in vitro and in vivo. It triggers bacterial death by disrupting the balance of purine metabolism and the TCA cycle, interfering with the redox process, making it a promising anti-Salmonella medication.

Role of medicinal plants from North Western Himalayas as an efflux pump inhibitor against MDR AcrAB-TolC Salmonella enterica serovar typhimurium: In vitro and In silico studies.

ETHNOPHARMACOLOGICAL RELEVANCE: Zingiber officinale Roscoe has been utilized traditionally to cure various diseases like cold, cough, diarrhoea, nausea, asthma, vomiting, toothache, stomach upset, respiratory disorders, joint pain, and throat infection. It is also consumed as spices and ginger tea. AIM OF THE STUDY: The current study was aimed to identify the phytocompounds of traditional medicinal plants of North-Western Himalaya that could inhibit the AcrAB-TolC efflux pump activity of Salmonella typhimurium and become sensitive to antibiotic killing at reduced dosage. MATERIAL AND METHODS: Medicinal plant extracts were prepared using methanol, aqueous, and ethyl acetate and tested for efflux pump inhibitory activity of Salmonella typhimurium NKS70, NKS174, and NKS773 strains using Ethidium Bromide (EtBr)-agar cartwheel assay. Synergism was assessed by the agar well diffusion method and EPI activity by berberine uptake and EtBr efflux inhibition assays. Microdilution method and checkerboard assays were done to determine the minimum inhibitory concentration (MIC) and fractional inhibitory concentration index (FICI) respectively for a bioactive compound. To validate the phytocompound and efflux pump interaction, molecular docking with 6IE8 (RamA) and 6IE9 (RamR) targets was done using autoDock vina software. Toxicity prediction and drug-likeness were predicted by using ProTox-II and Molinspiration respectively. RESULTS: Methanolic and ethyl acetate extracts of P. integerrima, O. sanctum, C. asiatica, M. charantia, Z. officinale, and W. somnifera in combination with ciprofloxacin and tetracycline showed synergistic antimicrobial activity with GIIs of 0.61-1.32 and GIIs 0.56-1.35 respectively. Methanolic extract of Z. officinal enhanced the antimicrobial potency of berberine (2 to 4-folds) and increased the EtBr accumulation. Furthermore, bioassay-guided fractionation leads to the identification of lariciresinol in ethyl acetate fraction, which decreased the MIC by 2-to 4-folds. The ΣFIC values varied from 0.30 to 0.55 with tetracycline, that indicated synergistic/additive effects. Lariciresinol also showed a good binding affinity with 6IE8 (-7.4 kcal mol-1) and 6IE9 (-8.2 kcal mol-1), which is comparable to tetracycline and chenodeoxycholic acid. Lariciresinol followed Lipinski's rule of five. CONCLUSION: The data suggest that lariciresinol from Z. officinale could be a potential efflux pump inhibitor that could lead to effective killing of drug resistant Salmonella typhimurium at lower MIC. Molecular docking confirmed the antibacterial EPI mechanism of lariciresinol in Salmonella typhimurium and confirmed to be safe for future use.

Antiinflammatory and antiinfective effect of caffeine in a mouse model of disseminated salmonellosis.

Caffeine has been reported for its antiinflammatory properties by stimulating phagocytosis. In this study, we investigated the antiinflammatory and antiinfective potential of caffeine in murine macrophage cell cultures and Swiss mice infected with virulent Salmonella enterica serotype typhimurium. Peritoneal macrophages (pMØ) were treated with caffeine on 96-well plates for 24 hr and then infected with Salmonella for 4 hr. In another experiment, the pMØ were first infected with the bacterium for 4 hr and then treated with caffeine for 24 hr. In addition, Swiss mice were inoculated, intraperitoneally, with S. typhimurium and then received caffeine intravenously. Control groups received phosphate-buffered saline (PBS) or dexamethasone. We found that treatments with caffeine increased the macrophage cell viability and reduced the intracellular bacterial load. The administration of caffeine to Swiss mice reduced the infiltration of leukocytes into the peritoneal cavity after the bacterial challenge. Furthermore, the bacterial burdens in the peritoneal fluid, bloodstream, spleen, and liver were decreased by caffeine treatment. The expression levels of tumor necrosis factor-alpha (TNF-α), interleukin-1ß (IL-1ß), IL-6, and inducible nitric oxide synthase (iNOs) were down-regulated after infection in caffeine-treated mice. We can conclude that caffeine has both antiinflammatory and antiinfective properties that can be useful for management of bacterial infections along with antibiotics.

Repurposing diphenylbutylpiperidine-class antipsychotic drugs for host-directed therapy of Mycobacterium tuberculosis and Salmonella enterica infections.

The persistent increase of multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) infections negatively impacts Tuberculosis treatment outcomes. Host-directed therapies (HDT) pose an complementing strategy, particularly since Mtb is highly successful in evading host-defense by manipulating host-signaling pathways. Here, we screened a library containing autophagy-modulating compounds for their ability to inhibit intracellular Mtb-bacteria. Several active compounds were identified, including two drugs of the diphenylbutylpiperidine-class, Fluspirilene and Pimozide, commonly used as antipsychotics. Both molecules inhibited intracellular Mtb in pro- as well as anti-inflammatory primary human macrophages in a host-directed manner and synergized with conventional anti-bacterials. Importantly, these inhibitory effects extended to MDR-Mtb strains and the unrelated intracellular pathogen, Salmonella enterica serovar Typhimurium (Stm). Mechanistically Fluspirilene and Pimozide were shown to regulate autophagy and alter the lysosomal response, partly correlating with increased bacterial localization to autophago(lyso)somes. Pimozide's and Fluspirilene's efficacy was inhibited by antioxidants, suggesting involvement of the oxidative-stress response in Mtb growth control. Furthermore, Fluspirilene and especially Pimozide counteracted Mtb-induced STAT5 phosphorylation, thereby reducing Mtb phagosome-localized CISH that promotes phagosomal acidification. In conclusion, two approved antipsychotic drugs, Pimozide and Fluspirilene, constitute highly promising and rapidly translatable candidates for HDT against Mtb and Stm and act by modulating the autophagic/lysosomal response by multiple mechanisms.

Chitosan propolis nanocomposite alone or in combination with apramycin: an alternative therapy for multidrug-resistant Salmonella Typhimurium in rabbits: in vitro and in vivo study.

Introduction. The emergence of multidrug-resistant Salmonella Typhimurium strains has increased the need for safe, alternative therapies from natural sources with antibacterial properties.Hypothesis/Gap Statement. There are no published data regarding the use of chitosan propolis nanocomposite (CPNP) either alone or in combination with antibiotics as antimicrobials against S. Typhimurium, especially in Egypt.Aim. This study evaluated the antibacterial activities of five antimicrobials [apramycin, propolis, chitosan nanoparticles (CNPs), chitosan propolis nanocomposite (CPNP) and CPNP +apramycin] against ten virulent and multidrug-resistant (MDR) S. Typhimurium field strains recovered from diarrheic rabbits through in vitro and in vivo study.Methodology. The expression levels of three virulence genes of S. Typhimurium strains were determined by quantitative reverse-transcription PCR (RT-qPCR) after exposure to sub-inhibitory concentrations of apramycin, propolis, CNPs, CPNP alone, and CPNP +apramycin. Additionally, 90 New Zealand rabbits were divided into control and experimentally S. Typhimurium-infected groups. The infected rabbits were orally administered saline solution (infected-untreated); 10 mg apramycin/kg (infected-apramycin-treated); 50 mg propolis/kg (infected-propolis-treated); 15 mg CPNP/kg (infected-CPNP-treated) and 15 mg CPNP +10 mg apramycin/kg (infected-CPNP +apramycin-treated) for 5 days.Results. The RT-qPCR analysis revealed different degrees of downregulation of all screened genes. Furthermore, the treatment of infected rabbits with CPNP or CPNP +apramycin significantly improved performance parameters, and total bacterial and Salmonella species counts, while also modulating both oxidative stress and altered liver and kidney parameters.Conclusion. This work demonstrates the use of CPNP alone or in combination with apramycin in the treatment of S. Typhimurium in rabbits.

Clinical presentation and outcomes of non-typhoidal Salmonella infections in patients with cancer.

BACKGROUND: Non-typhoidal Salmonella (NTS) infection is thought to be more severe in cancer patients, but this has not been studied since the development of new cancer therapies, increasing antibiotic resistance and the introduction of new antibiotics. We sought to describe the demographic characteristics, microbiological findings, clinical manifestations, and outcomes of NTS infections in cancer patients at our institution. METHODS: We reviewed microbiology laboratory records and identified patients who had cancer and from whom NTS organisms were recovered between January 1, 2000 and December 31, 2013, at a comprehensive cancer center in Houston, Texas. Descriptive statistics were used to summarize patient characteristics, clinical presentation and outcomes. RESULTS: We identified 110 isolates from 82 patients with 88 episodes of NTS infection (including five relapses [6%] in four patients, and two consecutive episodes in one patient). Fifty-five patients (67%) had hematologic malignancies. Most NTS isolates were susceptible to the commonly prescribed antimicrobials. Sixty-nine percent of patients had sepsis and one-third had severe sepsis or septic shock. Gastroenteritis, bacteremia, or both were present in 69% of patients, and the rest had focal infection. Mortality at 30 days was low (8%). Relapses occurred only in patients receiving ≤ 10 days of antibiotic therapy. CONCLUSIONS: NTS affects predominantly patients with hematologic malignancies, followed by gastrointestinal and genitourinary cancers. Invasive disease, sepsis, and septic shock are common presentations among admitted patients. Antimicrobial prophylaxis may not prevent NTS infection. Thirty-day mortality and attributable mortality rates were low in our series compared to older case series. Early appropriate antibiotic therapy may have had a role in decreasing mortality. Relapses occurred in patients receiving ≤ 10 days of therapy, suggesting the need for longer duration of antibiotic therapy in cancer patients with uncomplicated NTS infections.

Bovine NK-lysin peptides exert potent antimicrobial activity against multidrug-resistant Salmonella outbreak isolates.

Multidrug-resistant (MDR) Salmonella is a threat to public health. Non-antibiotic therapies could serve as important countermeasures to control MDR Salmonella outbreaks. In this study, antimicrobial activity of cationic α-helical bovine NK-lysin-derived antimicrobial peptides was evaluated against MDR Salmonella outbreak isolates. NK2A and NK2B strongly inhibited MDR Salmonella growth while NK1 and NK2C showed minimum-to-no growth inhibition. Scrambled-NK2A, which is devoid of α-helicity but has the same net positive charge as NK2A, also failed to inhibit bacterial growth. Incubation of negatively charged MDR Salmonella with NK2A showed increased Zeta potential, indicating bacterial-peptide electrostatic attraction. Confocal and transmission electron microscopy studies revealed NK2A-mediated damage to MDR Salmonella membranes. LPS inhibited NK2A-mediated growth suppression in a dose-dependent response, suggesting irreversible NK2A-LPS binding. LPS-NK2A binding and bacterial membrane disruption was also confirmed via electron microscopy using gold nanoparticle-NK2A conjugates. Finally, NK2A-loaded polyanhydride nanoparticles showed sustained peptide delivery and anti-bacterial activity. Together, these findings indicate that NK2A α-helicity and positive charge are prerequisites for antimicrobial activity and that MDR Salmonella killing is mediated by direct interaction of NK2A with LPS and the inner membrane, leading to bacterial membrane permeabilization. With further optimization using nano-carriers, NK2A has the potential to become a potent anti-MDR Salmonella agent.

Cinnamomum cassia and Syzygium aromaticum Essential Oils Reduce the Colonization of Salmonella Typhimurium in an In Vivo Infection Model Using Caenorhabditis elegans.

The regulation of intestinal colonization in livestock by means of non-bactericidal additives is an important management lever for zoonotic bacteria such as Salmonella spp. Caenorhabditis elegans is proposed here as a model for the evaluation of five essential oils (EOs) as anti-colonization products against Salmonella Typhimurium. An evaluation of the toxicity of EOs for C. elegans showed LD50 values ranging from 74.5 ± 9.6 µg/mL for Cinnamomum cassia (CEO) to 271.6 ± 14.9 µg/mL for Syzygium aromaticum (SyEO). Both EOs significantly inhibited bacterial colonization in the digestive tract of C. elegans with reductions of 0.88 and 0.70 log CFU/nematode at nontoxic concentrations of 50 µg/mL and 150 µg/mL, respectively. With the minimal bactericidal concentrations of CEO and SyEO against S. Typhimurium being 312.5 µg/mL and 625 µg/mL, respectively, an antibacterial effect can be excluded to explain the inhibition of the bacterial load. The anti-colonizing activity of these two EOs could, however, be related to an inhibition of the swimming motility, which was significantly reduced by 23.47% for CEO at 50 µg/mL and 19.56% for SyEO at 150 µg/mL. This study shows the potential of C. elegans as a predictive in vivo model of anti-colonizing activities that is suitable for the evaluation of essential oils.

Antibacterial activity of Citrus hystrix toward Salmonella spp. infection.

INTRODUCTION: Citrus hystrix is widely used by Indonesians as a traditional medicine for gastrointestinal diseases, including Salmonella spp. infection. We investigated the antibacterial activity of the ethanolic peel extract of C. hystrix against Salmonella typhimurium. METHODS: The antibacterial activity was evaluated both in vitro and in vivo. The minimum inhibitory concentration (MIC) of the extract was determined at a concentration of 0.625% by agar dilution assay. Later, the in vivo antibacterial activity was examined by the administration of 16mg of the extract daily for three consecutive days in a mouse model infected with S. typhimurium. RESULTS: The bacterial loads of S. typhimurium in the ileum, liver, and spleen decreased after 24h of administration of the extract (p=0.00008, p=0.00084, and p=0.00003, respectively). CONCLUSION: The ethanolic peel extract of C. hystrix shows antibacterial activity against S. typhimurium, indicating the potential of C. hystrix as an effective treatment for Salmonella spp. infection.

Mitracarpus frigidus (Rubiaceae) inhibits inflammatory and oxidative stress mediators in Salmonella sp. mouse infection.

OBJECTIVES: Evaluation of the in-vivo anti-inflammatory activity of the methanolic extract obtained from the aerial parts of Mitracarpus frigidus (MFM) in the infection caused by two Salmonella strains and its chemical fingerprint by UFLC-quadrupole time of flight-MS. METHODS: The efficacy of MFM was investigated in a classical in-vivo Salmonella infection mouse model. A Salmonella reference strain (ATCC 13311) and a clinical isolate were used to infect mice and then MFM was orally administered during 14 days. At the end of the treatment with MFM, the infection and inflammatory levels were assayed. KEY FINDINGS: MFM treatment showed a significant reduction in mice mortality by Salmonella infection and, also, did not cause alterations in the liver function. Inhibitions of inflammatory and oxidative stress mediators [malondialdehyde (MDA), catalase, and metalloproteinase] were possibly involved in the observed effects. Chlorogenic acid, clarinoside, quercetin-pentosylhexoside, rutin, kaempferol-3O-rutinoside, kaempferol-rhamnosylhexoside and 2-azaanthraquinone were identified in MFM. CONCLUSIONS: MFM was effective in some inflammatory parameters, in the experimental conditions that were used in the study. The results presented in this study and the previous in-vitro anti-Salmonella activity reported by our research group reinforce the importance of MFM studies to considerer it as an alternative treatment for salmonellosis.

Perspectives for the use of latex peptidases from Calotropis procera for control of inflammation derived from Salmonella infections.

BACKGROUND: Anti-inflammatory properties have been attributed to latex proteins of the medicinal plant Calotropis procera. PURPOSE: A mixture of cysteine peptidases (LPp2) from C. procera latex was investigated for control of inflammatory mediators and inflammation in a mouse model of Salmonella infection. METHODS: LPp2 peptidase activity was confirmed by the BANA assay. Cytotoxicity assays were conducted with immortalized macrophages. Peritoneal macrophages (pMØ) from Swiss mice were stimulated with lipopolysaccharide (LPS) in 96-well plates and then cultured with nontoxic concentrations of LPp2. Swiss mice intravenously received LPp2 (10 mg/kg) and then were challenged intraperitoneally with virulent Salmonella enterica Ser. Typhimurium. RESULTS: LPp2 was not toxic at dosages lower than 62.2 µg/mL. LPp2 treatments of pMØ stimulated with LPS impaired mRNA expression of pro-inflammatory cytokines IL-1ß, TNF-α, IL-6 and IL-10. LPp2 increased the intracellular bacterial killing in infected pMØ. Mice given LPp2 had a lower number of leukocytes in the peritoneal cavity in comparison to control groups 6 h after infection. The bacterial burden and histological damage were widespread in target organs of mice receiving LPp2. CONCLUSION: We conclude that LPp2 contains peptidases with strong anti-inflammatory properties, which may render mice more susceptible to early disseminated infection caused by Salmonella.

Evaluation of physicochemical properties of Qinling Apis cerana honey and the antimicrobial activity of the extract against Salmonella Typhimurium LT2 in vitro and in vivo.

Apis cerana honey collected from the Qinling Mountains in China has been widely used for its antimicrobial property in traditional Chinese medicine. However, its antibacterial mechanism against Salmonella Typhimurium LT2 is still uncertain. A total of 52 volatile components were identified using headspace-gas-chromatography-ion-mobility, and Qinling A. cerana honey exhibited more abundant aromas than monofloral honeys. The phenolic extracts of honey sample F exhibited the lowest minimum inhibitory concentration (5 mg/mL), and chlorogenic acid exhibited the highest (155.91 ± 0.79 mg/kg), followed by caffeic acid, and rutin. After being treated with the extract, cell membranes of S. Typhimurium LT2 significantly shrunk and further collapsed. The extract treatment on mice caused a significant decrease in S. Typhimurium LT2, and a dramatic increase in the potential prebiotic Lactobacillus in both the caecum and colon. The results demonstrate that the Qinling A. cerana honey extract could effectively inhibit S. Typhimurium in vitro and in vivo.

Latex proteins downregulate inflammation and restores blood-coagulation homeostasis in acute Salmonella infection.

BACKGROUND: Calotropis procera latex protein fraction (LP) was previously shown to protect animals from septic shock. Further investigations showed that LP modulate nitric oxide and cytokines levels. OBJECTIVES: To evaluate whether the protective effects of LP, against lethal bacterial infection, is observed in its subfractions (LPPII and LPPIII). METHODS: Subfractions (5 and 10 mg/kg) were tested by i.p. administration, 24 h before challenging with lethal injection (i.p.) of Salmonella Typhimurium. LPPIII (5 mg/kg) which showed higher survival rate was assayed to evaluate bacterial clearance, histopathology, leukocyte recruitment, plasma coagulation time, cytokines and NO levels. FINDINGS: LPPIII protected 70% of animals of death. The animals given LPPIII exhibited reduced bacterial load in blood and peritoneal fluid after 24 h compared to the control. LPPIII promoted macrophage infiltration in spleen and liver. LPPIII restored the coagulation time of infected animals, increased IL-10 and reduced NO in blood. MAIN CONCLUSIONS: LPPIII recruited macrophages to the target organs of bacterial infection. This addressed inflammatory stimulus seems to reduce bacterial colonisation in spleen and liver, down regulate bacterial spread and contribute to avoid septic shock.

Vitamin A supplementation boosts control of antibiotic-resistant Salmonella infection in malnourished mice.

Disseminated disease from non-typhoidal Salmonella enterica strains results in >20% mortality globally. Barriers to effective treatment include emerging multidrug resistance, antibiotic treatment failure, and risk factors such as malnutrition and related micronutrient deficiencies. Individuals in sub-Saharan Africa are disproportionately affected by non-typhoidal S. enterica bloodstream infections. To inform a clinical trial in people, we investigated vitamin A as a treatment in the context of antibiotic treatment failure in a mouse model of vitamin A deficiency. Vitamin A-deficient (VAD) mice exhibited higher systemic bacterial levels with a multidrug-resistant clinical isolate in comparison to mice on a control diet. Sex-specific differences in vitamin A deficiency and disseminated infection with S. enterica serotype Typhimurium (S. Typhimurium) were observed. VAD male mice had decreased weight gain compared to control male mice. Further, infected VAD male mice had significant weight loss and decreased survival during the course of infection. These differences were not apparent in female mice. In a model of disseminated S. Typhimurium infection and antibiotic treatment failure, we assessed the potential of two consecutive doses of vitamin A in alleviating infection in male and female mice on a VAD or control diet. We found that subtherapeutic antibiotic treatment synergized with vitamin A treatment in infected VAD male mice, significantly decreasing systemic bacterial levels, mitigating weight loss and improving survival. These results suggest that assessing vitamin A as a therapy during bacteremia in malnourished patients may lead to improved health outcomes in a subset of patients, especially in the context of antibiotic treatment failure.

The role of animals as a source of antimicrobial resistant nontyphoidal Salmonella causing invasive and non-invasive human disease in Vietnam.

BACKGROUND: Nontyphoidal Salmonella (NTS) are associated with both diarrhea and bacteremia. Antimicrobial resistance (AMR) is common in NTS in low-middle income countries, but the major source(s) of AMR NTS in humans are not known. Here, we aimed to assess the role of animals as a source of AMR in human NTS infections in Vietnam. We retrospectively combined and analyzed 672 NTS human and animal isolates from four studies in southern Vietnam and compared serovars, sequence types (ST), and AMR profiles. We generated a population structure of circulating organisms and aimed to attribute sources of AMR in NTS causing invasive and noninvasive disease in humans using Bayesian multinomial mixture models. RESULTS: Among 672 NTS isolates, 148 (22%) originated from human blood, 211 (31%) from human stool, and 313 (47%) from animal stool. The distribution of serovars, STs, and AMR profiles differed among sources; serovars Enteritidis, Typhimurium, and Weltevreden were the most common in human blood, human stool, and animals, respectively. We identified an association between the source of NTS and AMR profile; the majority of AMR isolates were isolated from human blood (p < 0.001). Modelling by ST-AMR profile found chickens and pigs were likely the major sources of AMR NTS in human blood and stool, respectively; but unsampled sources were found to be a major contributor. CONCLUSIONS: Antimicrobial use in food animals is hypothesized to play role in the emergence of AMR in human pathogens. Our cross-sectional population-based approach suggests a significant overlap between AMR in NTS in animals and humans, but animal NTS does explain the full extent of AMR in human NTS infections in Vietnam.

The phenotypic and molecular characteristics of antimicrobial resistance of Salmonella enterica subsp. enterica serovar Typhimurium in Henan Province, China.

BACKGROUND: Salmonella enterica subsp. enterica serovar Typhimurium infections continue to be a significant public health threat worldwide. The aim of this study was to investigate antibiotic resistance among 147 S. Typhimurium isolates collected from patients in Henan, China from 2006 to 2015. METHODS: 147 S. Typhimurium isolates were collected from March 2006 to November 2015 in Henan Province, China. Antimicrobial susceptibility testing was performed, and the resistant genes of ciprofloxacin, cephalosporins (ceftriaxone and cefoxitin) and azithromycin were detected and sequenced. Clonal relationships were assessed by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). RESULTS: Of the 147 isolates, 91.1% were multidrug resistant (MDR), with 4.1% being resistant to all antibiotic classes tested. Of concern, 13 MDR isolates were co-resistant to the first-line treatments cephalosporins and ciprofloxacin, while three were also resistant to azithromycin. Seven PFGE patterns were identified among the 13 isolates. All of the isolates could be assigned to one of four main groups, with a similarity value of 89%. MLST assigned the 147 isolates into five STs, including two dominant STs (ST19 and ST34). Of the 43 ciprofloxacin-resistant isolates, 39 carried double gyrA mutations (Ser83Phe, Asp87Asn/Tyr/Gly) and a single parC (Ser80Arg) mutation, including 1 isolate with four mutations (gyrA: Ser83Phe, Asp87Gly; parC: Ser80Arg; parE: Ser458Pro). In addition, 12 isolates not only carried mutations in gyrA and parC but also had at least one plasmid-mediated quinolone resistance (PMQR) gene. Among the 32 cephalosporin-resistant isolates, the most common extended-spectrum ß-lactamase (ESBL) gene was blaOXA-1, followed by blaCTX-M, blaTEM-1, and blaCMY-2. Moreover, the mphA gene was identified in 5 of the 15 azithromycin-resistant isolates. Four MDR isolates contained ESBL and PMQR genes, and one of them also carried mphA in addition. CONCLUSION: The high level of antibiotic resistance observed in S. Typhimurium poses a great danger to public health, so continuous surveillance of changes in antibiotic resistance is necessary.

Dual role of splenic mononuclear and polymorphonuclear cells in the outcome of ciprofloxacin treatment of Salmonella enterica infections.

OBJECTIVES: To determine the immune cell populations associated with Salmonella enterica serovar Typhimurium before and after ciprofloxacin treatment using a murine model of systemic infection. The effect of depletion of immune cells associating with Salmonella on treatment outcome was also determined. METHODS: We infected mice with a Salmonella enterica serovar Typhimurium strain expressing GFP and used multicolour flow cytometry to identify splenic immune cell populations associating with GFP-positive Salmonella before and after treatment with ciprofloxacin. This was followed by depletion of different immune cell populations using antibodies and liposomes. RESULTS: Our results identified CD11b+CD11chi/lo (dendritic cells/macrophages) and Ly6G+CD11b+ (neutrophils) leucocytes as the main host cell populations that are associated with Salmonella after ciprofloxacin treatment. We therefore proceeded to test the effects of depletion of such populations during treatment. We show that depletion of Ly6G+CD11b+ populations resulted in an increase in the number of viable bacterial cells in the spleen at the end of ciprofloxacin treatment. Conversely, treatment with clodronate liposomes during antimicrobial treatment, which depleted the CD11b+CD11chi/lo populations, resulted in lower numbers of viable bacteria in the tissues. CONCLUSIONS: Our study identified host cells where Salmonella bacteria persist during ciprofloxacin treatment and revealed a dual and opposing effect of removal of Ly6G+CD11b+ and CD11b+CD11chi/lo host cells on the efficacy of antimicrobial treatment. This suggests a dichotomy in the role of these populations in clearance/persistence of Salmonella during antimicrobial treatment.

In vitro and in vivo anti-salmonella properties of hydroethanolic extract of Detarium microcarpum Guill. & Perr. (Leguminosae) root bark and LC-MS-based phytochemical analysis.

ETHNOPHARMACOLOGICAL RELEVANCE: Typhoid fever treatment remains a challenge in endemic countries. Detarium microcarpum is traditionally used to manage typhoid. AIM OF THE STUDY: The study aims to explore the efficacy of hydroethanolic extract of Detarium microcarpum root bark in rats infected with salmonella. MATERIAL AND METHODS: The phytochemical profile of the extract was obtained by UHPLC-MS analysis in an attempt of standardization. The in vitro antimicrobial activity was determined using broth dilution method. Salmonella infection was induced by oral administration of S. thyphimurium to immunosuppressed rats. Infected rats were then treated 2 h later with the extract (75, 150 and 300 mg/kg), distilled water (normal and salmonella control) and ciprofloxacin (8 mg/kg) for control. Body weight was monitored and stools were cultured to determine the number of colony-forming units. At the end of treatment, animals were sacrificed, blood and organs were collected for hematological, biochemical and histopathological analyses. RESULTS: Detarium microcarpum extract as well as the isolated compound (rhinocerotinoic acid) exhibited good antimicrobial activity in vitro with bacteriostatic effects. The plant extract significantly (p < 0.05) inhibited the bacterial development in infected animals with an effective dose (ED50) of 75 mg/kg. In addition, the extract prevented body weight loss, hematological, biochemical and histopathological damages in treated rats. CONCLUSION: Detarium microcarpum extract possesses antisalmonella properties justifying its traditional use for the typhoid fever management.

Identification of the natural product paeonol derived from peony bark as an inhibitor of the Salmonella enterica serovar Typhimurium type III secretion system.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is an important zoonotic pathogen in public health and food safety. The type III secretion system (T3SS) encoded by Salmonella pathogenicity island (SPI) is a sophisticated molecular machine that facilitates active invasion, intracellular replication, and host inflammation. Due to increasing antibiotic resistance, new therapeutic strategies that target the Salmonella T3SS have received considerable attention. In this study, paeonol was identified as an inhibitor of the S. Typhimurium T3SS. Paeonol significantly blocked the translocation of SipA into host cells and suppressed the expression of effector proteins without affecting bacterial growth in the effective concentration range. Additionally, S. Typhimurium-mediated cell injury and invasion levels were significantly reduced after treatment with paeonol, without cytotoxicity. Most importantly, the comprehensive protective effect of paeonol was confirmed in an S. Typhimurium mouse infection model. Preliminary mechanistic studies suggest that paeonol inhibits the expression of effector proteins by reducing the transcription level of the SPI-1 regulatory pathway gene hilA. This work provides proof that paeonol could be used as a potential drug to treat infections caused by Salmonella.