Prevalence, serotypes, and drug resistance of nontyphoidal Salmonella among paediatric patients in a tertiary hospital in Guangzhou, China, 2014-2016

Dynamic antimicrobial resistance and phylogenomic structure of Salmonella Typhimurium from 2007 to 2019 in Shanghai, China

Salmonella enterica serovar Typhimurium is an important foodborne pathogen associated with human salmonellosis worldwide. A retrospective screening was performed to elucidate the prevalence, antimicrobial resistance, and phylogenomic characterization of this pathogen in Shanghai, China. S. Typhimurium isolates were selected from 2,211 serotyped Salmonella isolates collected during 2007-2019. Two hundred and seventy-seven S. Typhimurium isolates were detected in 15 of 16 districts in Shanghai. It was noted that 214 (77.3%) isolates were multi-drug resistant and 32 (11.6%) isolates were resistant to ciprofloxacin and 5 (1.8%) isolates were further resistant to ceftriaxone. Poisson generalized linear mixed model results showed that the multi-drug resistance (MDR) in 2017 and 2018 was significantly higher than that in 2010 (P＜0.05), highlighting an increase in the risk of MDR. Phylogenetic results showed that a global data set of 401 sequenced S. Typhimurium isolates was classified into four clones (ST36, ST313, ST19, and ST34), which appeared in international clonal dissemination. The ST34 isolates from China fell into two clades, ST34C1 and ST34C2, the latter of which might originate from Shanghai, and then expanded nationally, accompanied by extended-spectrum β-lactamase gene blaCTX-M-14 and a mutation in quinolone resistance-determining region of the gyrA 87 site. Furthermore, blaCTX-M-14 linking to ISEcp1 upstream and ΔIS903B downstream was found in IncI (Gamma)-like plasmids, and the plasmid conjugation contributed to its horizontal transmission. To our knowledge, it is the first report of the epidemiological and phylogenetic characterization for S. Typhimurium including the emerged clade ST34C2 in Shanghai, warranting the necessity of surveillance for this high-risk pathogen.

IMPORTANCE

Our study uncovered a widespread distribution of Salmonella enterica serovar Typhimurium isolates in Shanghai accompanied by the increase in antimicrobial resistance (AMR) especially MDR during a 10-year period, which filled in the gap about a long period of continuous monitoring of AMR in this pathogen in Shanghai. Meanwhile, we identified a new clade ST34C2 of S. Typhimurium with the acquisition of IncI (Gamma)-like plasmids mediated by extended-spectrum β-lactamase gene blaCTX-M-14 as well as gyrA 87 mutation, which had not been reported before. It was noted that IncI (Gamma)-like plasmids were reported in S. Typhimurium for the first time and conjugation could accelerate the spread of antimicrobial resistance gene blaCTX-M-14. These findings on the epidemic, antimicrobial resistance, and phylogenomic characterization for S. Typhimurium provide valuable insights into its potential risk to public health and also the basis for AMR prevention and control strategies in Shanghai in the future.

Molecular Characteristics of Salmonella Spp. Responsible for Bloodstream Infections in a Tertiary Hospital in Nanjing, China, 2019-2021

Objective

To investigate the clinical and molecular characteristics of Salmonella spp. causing bloodstream infections (BSIs) in our hospital.

Methods

We studied 22 clinical Salmonella isolates from BSIs and 16 from non-BSIs, performing antimicrobial susceptibility testing (AST) and whole genome sequencing (WGS). The analysis included serovars, antibiotic resistance genes (ARGs), virulence factors (VFs), sequence types (STs), plasmid replicons, and genetic relationships. We also assessed pathogenicity of the isolates causing BSIs through growth, biofilm formation, and anti-serum killing assays.

Results

WGS analysis identified 13 Salmonella serovars, with four responsible for BSIs. S. Enteritidis was the most prevalent serovar, involved in 19 (50.0%) cases. BSIs were caused by 17S. Enteritidis, two S. Typhimurium, two S. Munster and one S. Diguel. Of the 38 isolates, 27 (71.1%) exhibited high resistance to ampicillin, and 24 (63.2%) to ampicillin/sulbactam. Thirty-six types of ARGs were identified, with blaTEM-1B (n = 25, 65.8%) being the most frequent. Ten plasmid replicons were found; the combination of IncFIB(S)-IncFII(S)-IncX1 was the most common in S. Enteritidis (94.7%). Fifteen STs were identified, among which ST11 was the most prevalent and clonally disseminated, primarily responsible for BSIs. A total of 333 different VFs were detected, 177 of which were common across all strains. No significant differences were observed between the BSI and non-BSI isolates in terms of resistance rates, ARGs, plasmid replicons, and VFs, except for seven VFs. No strong pathogenicity was observed in the BSI-causing isolates.

Conclusion

BSIs were predominantly caused by clonally disseminated S. Enteritidis ST11, the majority of which carried multiple ARGs, VFs and plasmid replicons. This study provides the first data on clonally disseminated S. Enteritidis ST11 causing BSIs, highlighting the urgent need for enhanced infection control measures.

A Food Poisoning Caused by Salmonella Enterica (S. Enteritidis) ST11 Carrying Multi-Antimicrobial Resistance Genes in 2019, China

Purpose

This study was to identify and analyze the pathogen responsible for food poisoning in a tourist group traveling from Macao to Zhuhai.

Patients and Methods

Samples were obtained from 27 patients of 96 cases, as well as samples of contaminated food in Macau. The collected samples were subjected to serological identification, drug sensitivity analysis, drug resistance gene identification, virulence factor analysis, and tracing.

Results

Twenty-six isolates and the salad isolate were S. enteritidis ST11. Isolates from patients were exhibited significant resistance to Penicillin AMP (Ampicillin) and quinolones NAL (Nalidixic acid). Among these isolates, 21 strains were resistant to two or more antibiotics, indicating the multi-drug resistance (MDR). Genomic characteristics and phylogenetic analysis were performed on 9 of the isolates using whole genome sequencing (WGS). The analysis revealed that the resistance to AMP and NAL was primarily caused by a gryA mutation D87Y (9/9, 100%), and the presence of beta-lactam resistance genes blaOXA-1 (1/9, 11.11%), blaTEM-141 (1/9, 11.11%), and blaTEM-1B (8/9, 88.89%). It was also found a strains isolated from patients had two resistance genes to quinolones or beta-lactam drugs (1/8, 12.5%), respectively. The strains were found to possess 165 virulence genes, one adherence class virulence factor, one invasion class virulence factor and various pathogenicity islands, including SPI-1, SPI-2, SPI-3, SPI-4, SPI-5, SPI-9, SPI-10, SPI-13, SPI-14, SPI-15, SGI 1, CS54_island, and C63PI-1. Additionally, the virulence plasmids were detected, including IncFIB(s)-IncFII(s)-IncX1 (55.56%), IncFIB(s)-IncFII(s) (33.33%), and IncFIB(s)-IncFII(s)-IncHI2-IncHI2A (11.11%). PFGE (Pulsed Field Gel Electrophoresis) and phylogenetic tree analysis revealed a high degree of similarity between Salmonella isolates from patients and food samples from Macao.

Conclusion

This study identified Salmonella enterica ST11 as the cause of the food poisoning outbreak. The findings highlight the importance of phenotypic characterization and next-generation sequencing (NGS) tools in epidemiological studies and emphasize the potential risk of a new emerging multi-antibiotic ST11 clone for S. enteritidis.

Levels of Indicator Bacteria and Characteristics of Foodborne Pathogens from Carcasses of Cattle Slaughterhouses in Korea

The initial microbial contamination of carcasses during slaughtering adversely affects spoilage and shelf life and is of global concern for food safety and meat quality. This study evaluated the hygiene and quality using the prevalence of foodborne pathogens and the level of indicator bacteria on 200 carcasses, collecting 10 from each of 20 cattle slaughterhouses in Korea. The distribution of aerobic bacterial count in carcasses was significantly highest at 2.0-3.0 log10 CFU/cm2 (34.1%), whereas the Escherichia coli count was significantly highest at under 1.0 log10 CFU/cm2 (94.0%) (P < 0.05). Clostridium perfringens was most prevalent (60.0% of slaughterhouses; 17.5% of carcasses), followed by Yersinia enterocolitica (30.0% of slaughterhouses; 6.5% of carcasses), Staphylococcus aureus (15.0% of slaughterhouses; 4.0% of carcasses), Listeria monocytogenes 1/2a (5.0% of slaughterhouses; 1.0% of carcasses), Salmonella enterica subsp. enterica serovar Infantis (5.0% of slaughterhouses; 1.0% of carcasses), and Shiga toxin-producing E. coli O:66 (5.0% of slaughterhouses; 0.5% of carcasses). Although 28 C. perfringens isolates from 11 slaughterhouses were divided into 21 pulsotypes, all isolates showed the same toxinotype as type A and only carried the cpa. Interestingly, 83.3% of isolates from two slaughterhouses located in the same province showed resistance to tetracycline. Furthermore, 13 Y. enterocolitica isolates from six slaughterhouses were divided into seven pulsotypes that were divided into biotypes 1A and 2 and serotypes O:5 and O:8, except for isolates that could not be typed. Twelve (92.3%) isolates only carried ystB, but one (7.7%) isolate carried ail and ystA. Moreover, 46.2% of Y. enterocolitica isolates showed multidrug resistance against ampicillin, cefoxitin, and amoxicillin/clavulanic acid. This study supports the need for continuous monitoring of slaughterhouses and hygiene management to improve the microbiological safety of carcasses.

Molecular characterization of IncFII plasmid carrying blaNDM-5 in a Salmonella enterica serovar Typhimurium ST34 clinical isolate in China

IMPORTANCE

In this study, an IncFII plasmid pIncFII-NDM5 carrying blaNDM-5 was found in carbapenem-resistant Salmonella enterica serovar Typhimurium (S. enterica serovar Typhimurium), which has conjugative transferability and carried blaNDM-5, bleMBL, mph(A), and blaTEM-1 four resistance genes that can mediate resistance to multiple antibiotics including cephalosporins, beta-lactamase inhibitor combinations, carbapenems, and macrolides. Phylogenetic analysis showed that 1104-65 and 1104-75 were closely related to other S. enterica serovar Typhimurium in this area. The above-mentioned S. enterica serovar Typhimurium chromosome carries blaCTX-M-55, qnrS1, and tet(A) genes, so the antibiotic resistance of isolates will be further enhanced after obtaining the pIncFII_NDM5-like plasmid. Meanwhile, we discovered a novel genetic structure of blaNDM-5 mediated by the IS26 composite transposon, which will expand our understanding of the emergence and spread of carbapenem-resistance genes. Altogether, the presence of the IncFII plasmid pIncFII-NDM5 further underscores the need for vigilant surveillance and appropriate infection control measures to mitigate the impact of carbapenem-resistant S. enterica serovar Typhimurium in clinical settings.

Antibiotic resistance trends for common bacterial aetiologies of childhood diarrhoea in low- and middle-income countries: A systematic review

Background

Diarrhoea is the second most common cause of death among children under the age of five worldwide. The World Health Organization (WHO) recommends treating diarrhoea with oral rehydration therapy, intravenous fluids for severe dehydration, and zinc supplements. Antibiotics are only recommended to treat acute, invasive diarrhoea. Rising antibiotic resistance has led to a decrease in the effectiveness of treatments for diarrhoea.

Methods

A systematic literature review in PubMed, Web of Science, and EMBASE was conducted to identify articles relevant to antibiotic-resistant childhood diarrhoea. Articles in English published between 1990 to 2020 that described antibiotic resistance patterns of common pathogens causing childhood diarrhoea in low- and middle-income countries were included. The studies were limited to papers that categorized children as 0-5 years or 0-10 years old. The proportion of isolates with resistance to major classes of antibiotics stratified by major WHO global regions and time was determined.

Results

Quantitative data were extracted from 44 articles that met screening criteria; most focused on children under five years. Escherichia coli isolates had relatively high resistance rates to ampicillin and tetracycline in the African (AFR), American (AMR), and Eastern Mediterranean Regions (EMR). There was moderate to high resistance to ampicillin and third generation cephalosporins among Salmonella spp in the AFR, EMR, and the Western Pacific Region (WPR). Resistance rates for ampicillin, co-trimoxazole, and chloramphenicol for Shigella in the AFR started at an alarmingly high rate ( ~ 90%) in 2006 and fluctuated over time. There were limited antibiotic resistance data for Aeromonas, Yersinia, and V. cholerae. The 161 isolates of Campylobacter analysed showed initially low rates of fluoroquinolone resistance with high rates of resistance in recent years, especially in the Southeast Asian Region.

Conclusions

Resistance to inexpensive antibiotics for treatment of invasive diarrhoea in children under ten years is widespread (although data on 6- to 10-year-old children are limited), and resistance rates to fluoroquinolones and later-generation cephalosporins are increasing. A strong regional surveillance system is needed to carefully monitor trends in antibiotic resistance, future studies should include school-aged children, and interventions are needed to reduce inappropriate use of antibiotics for the treatment of community-acquired, non-invasive diarrhoea.

Registration

This systematic review was registered in Prospero (registration number CRD42020204004) in August 2020.

Interference with Bacterial Conjugation and Natural Alternatives to Antibiotics: Bridging a Gap

Horizontal gene transfer (HGT) in food matrices has been investigated under conditions that favor gene exchange. However, the major challenge lies in determining the specific conditions pertaining to the adapted microbial pairs associated with the food matrix. HGT is primarily responsible for enhancing the microbial repertoire for the evolution and spread of antimicrobial resistance and is a major target for controlling pathogens of public health concern in food ecosystems. In this study, we investigated Salmonella Heidelberg (SH) and Escherichia coli (EC) regarding gene exchange under conditions mimicking the industrial environment, with the coproducts whey (SL) and chicken juice (CJ). The S. Heidelberg strain was characterized by antibiotic susceptibility standards and PCR to detect the bla_TEM gene. A concentration of 0.39 mg/mL was determined to evaluate the anti-conjugation activity of nanostructured lipid nanocarriers (NLCs) of essential oils to mitigate β-lactam resistance gene transfer. The results showed that the addition of these coproducts promoted an increase of more than 3.5 (whey) and 2.5 (chicken juice) orders of magnitude in the conjugation process (p < 0.01), and NLCs of sage essential oil significantly reduced the conjugation frequency (CF) by 74.90, 90.6, and 124.4 times when compared to the transfers in the absence of coproducts and the presence of SL and CJ, respectively. For NLCs from olibanum essential oil, the decrease was 4.46-fold for conjugations without inhibitors and 3.12- and 11.3-fold in the presence of SL and CJ. NLCs associated with sage and olibanum essential oils effectively control the transfer of antibiotic resistance genes and are a promising alternative for use at industrial levels.

Exploring the prevalence of antibiotic resistance patterns and drivers of antibiotics resistance of Salmonella in livestock and poultry-derived foods: a systematic review and meta-analysis in Bangladesh from 2000 to 2022

Background

Antimicrobial resistance (AMR) is a severe public health problem that Bangladeshis are dealing with nowadays. However, we wanted to investigate the pooled prevalence of Salmonella and AMR in Salmonella strains isolated from livestock- and poultry-derived foods between 1 January 2000 and 31 August 2022.

Methods

The metafor and metareg packages in the R programming language were used to conduct all analyses. We used a random-effect or fixed-effect model for pooled prevalence of Salmonella and AMR to Salmonella, depending on the heterogeneity test for each antibiotic. The heterogeneity was examined using stratified analyses, the meta-regression approach and sensitivity analysis.

Results

The combined prevalence of Salmonella in livestock and poultry-derived food in Bangladesh is 37%, according to the 12-research considered (95% CI: 23%-52%). According to subgroup analysis, neomycin had the lowest prevalence of resistance (4%, 95% CI: 1%-13%), whereas tetracycline had the highest prevalence of resistance (81%, 95% CI: 53%-98%). According to univariate meta-analysis and correlation analysis, the prevalence of Salmonella increased with the study period (β = 0.0179; 95% CI: 0.0059-0.0298, P = 0.0034; R² = 46.11%) and without this, none of aforementioned variables was significantly associated with the detected heterogeneity and there was a positive relationship (r = 0.692, P = 0.001) between the Salmonella prevalence and study period.

Conclusions

AMR is rising alarmingly in Bangladesh by livestock-derived food consumption. However, monitoring and evaluating antibiotic sensitivity trends and developing effective antibiotic regimens may improve Salmonella infection inhibition and control in Bangladesh. Policymakers should be concerned about food handling practices. Doctors should be concerned when using prescribing antibiotics.

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.

Prevalence of Chromosomally Located blaCTX-M-55 in Salmonella Typhimurium ST34 Isolates Recovered from a Tertiary Hospital in Guangzhou, China

Nontyphoidal Salmonella (NTS) is one of the most prevalent bacterial causes of gastrointestinal infections worldwide. Meanwhile, the detection rate of CTX-M-55 ESBL-positive has increased gradually in China. To identify the molecular epidemiological and genomic characteristics of blaCTX-M-55-carrying nontyphoidal Salmonella (NTS) clinical isolates, a total of 105 NTS isolates were collected from a Chinese tertiary hospital. Antimicrobial susceptibility testing was performed to determine the resistance phenotype. Whole-genome sequencing and bioinformatics analysis were used to determine the antimicrobial resistance genes, serotypes, phylogenetic relationships, and the genetic environment of the blaCTX-M-55 gene. The results showed that among the 22 ceftriaxone resistant isolates, the blaCTX-M-55 was the most common β-Lactamase gene carried by 14 isolates, including serotypes S. Typhimurium (10/14), S. Muenster (2/14), S. Rissen (1/14), and S. Saintpaul (1/14). Phylogenetic analysis shows that 10 blaCTX-M-55-positive S. Typhimurium ST34 isolates were divided into two clusters. The genetic relationship of isolates in each cluster was very close (≤10 cgMLST loci). The blaCTX-M-55 gene was located on the chromosome in 10 isolates, on IncI1 plasmid in three isolates, and IncHI2 plasmid in one isolate. In conclusion, the blaCTX-M-55 gene, mainly located on the chromosome of S. Typhimurium ST34 isolates, was the main driving force associated with the resistance of NTS to cephalosporins. Therefore, close attention to the clonal dissemination of blaCTX-M-55-carrying S. Typhimurium ST34 in clinical settings must be monitored carefully. IMPORTANCE ESCs are the first choice for treating NTS infections. However, ESBLs and AmpC β-lactamases are the most typical cause for ESCs resistance. The CTX-M-55 ESBL-positive rate has gradually increased in the clinic in recent years. At present, the research about blaCTX-M-55-positive Salmonella mainly focuses on the foodborne animals or the environment while less on clinical patients. Thus, this study was carried out for identifying molecular epidemiological and genomic characteristics of blaCTX-M-55-carrying NTS clinical isolates. The results showed that the blaCTX-M-55 gene, mainly located on the chromosome of S. Typhimurium ST34 isolates from Conghua District, was the main driving force associated with the resistance of NTS to cephalosporins. Therefore, our work highlights the importance of monitoring the clonal dissemination of blaCTX-M-55-carrying S. Typhimurium ST34 in clinical settings.

Research progress on antibiotic resistance of Salmonella

Antibiotic abuse results in various antibiotic resistance among a number of foodborne bacteria, posing a severe threat to food safety. Antibiotic resistance genes are commonly detected in foodborne pathogens, which has sparked much interest in finding solutions to these issues. Various strategies against these drug-resistant pathogens have been studied, including new antibiotics and phages. Recently, a powerful tool has been introduced in the fight against drug-resistant pathogens, namely, clustered regularly interspaced short palindromic repeats-CRISPR associated (CRISPR-Cas) system aggregated by a prokaryotic defense mechanism. This review summarized the mechanism of antibiotic resistance in Salmonella and resistance to common antibiotics, analysed the relationship between Salmonella CRISPR-Cas and antibiotic resistance, discussed the changes in antibiotic resistance on the structure and function of CRISPR-Cas, and finally predicted the mechanism of CRISPR-Cas intervention in Salmonella antibiotic resistance. In the future, CRISPR-Cas is expected to become an important tool to reduce the threat of antibiotic-resistant pathogens in food safety.

Prevalence and Trends in Antimicrobial Susceptibility Patterns of Multi-Drug-Resistance Non-Typhoidal Salmonella in Central Thailand, 2012–2019

Purpose

Multi-drug resistance of non-typhoidal Salmonella (MDR-NTS) is an increasing threat worldwide. In Thailand, data for the past decade is limited. This research is to determine the prevalence and trends of nonsusceptibility patterns of the bacteria, especially to ciprofloxacin and ceftriaxone.

Methods

This retrospective study was extracted data of patients who had non-typhoidal Salmonella (NTS) infection, from 10 hospitals between June 2011 and June 2020. Demographic data, culture reports, and antimicrobial susceptibility were included in the analysis.

Results

A total of 433 patients were identified. The most common age group was less than 15 years old (53.6%), with a median age of 12 years (IQR 57–4). Of these people, 61.1% had gastroenteritis and 36.7% had bacteremia. The most prevalent serogroups was C (28.6%). MDR-NTS rate was 52.8% (95% CI 39–44). The resistant rates were 43%, 32.8%, 22.8%, 6.7%, 4%, 0.45%, 0.45% for sulfamethoxazole/trimethoprim, amoxicillin-clavulanic acid, cefotaxime, ampicillin/sulbactam, piperacillin/tazobactam, imipenem and meropenem retrospectively. Resistant rates have been increasing, especially for ciprofloxacin (30%), which rose from 16.6% in 2011–2015 to 39.5% in 2016–2020 (prevalence rate ratio (PRR) 2.4,95% CI 1.51–3.72) and for ceftriaxone 25.4% which rose from 16.1% to 32% (PRR 2 95% CI 1.24–3.16). Ampicillin, norfloxacin, tetracycline, amikacin, gentamicin, and ceftazidime remained static at 62.3%, 49.5%, 33.2%, 15.2%, 8.8%, 2.8%, respectively.

Conclusion

The prevalence of MDR-NTS has been increasing over the past decade, particularly those strains which demonstrate resistance to ciprofloxacin and ceftriaxone. Finding successful treatment requires a comprehensive selection of proper antimicrobials as well as close monitoring, especially in cases with severe infection.

Prevalence, Serotype Distribution and Antimicrobial Resistance of Non-Typhoidal Salmonella in Hospitalized Patients in Conghua District of Guangzhou, China

Salmonella infection is a major public health concern worldwide, has contributed to an increased economic burden on the health systems. Non-typhoidal Salmonella (NTS) is a common cause of bacterial enteritis in humans, causing 93.8 million cases of gastroenteritis globally each year, with 155,000 deaths. Guangzhou city is situated in the south of China and has a sub-tropical climate, the heat and heavy rainfall helps the spread of NTS. However, no information of NTS infection is available in humans in Conghua District, the largest administrative district of Guangzhou. To understand the prevalence, serotype distribution, risk factors and drug resistance of NTS infection in humans in the survey area, an epidemiological investigation was conducted in hospitalized patients in Conghua District in Guangzhou, China. A total of 255 fecal specimens were collected from hospitalized patients (one each), with a questionnaire for each participant, and NTS infection was identified by culture, as well as serotypes confirmed by slide agglutination tests. An average prevalence of 20.39% (52/255) was observed and three serogroups were identified—serogroup B (n = 46), serogroup C1 (n = 4) and serogroup D1 (n = 2). Among them, Salmonella Typhimurium (n = 39) was the most common serotype. Children aged &lt;3 years were observed to have a statistically higher prevalence of NTS infection than adults (25.15% versus 4.65%, P = 0.006); children with artificial feeding had a statistically higher prevalence than those with breastfeeding (30.77% versus 8.33%, P = 0.044). Antimicrobial resistance testing revealed that the majority of strains were resistant to ampicillin (92.16%), as well as 47.06% of all strains were multi-drug resistant. Therefore, it is necessary to continuous monitoring and rational use of antibiotics, which will be helpful to reduce the prevalence of resistant strains. These data will aid in making efficient control strategies to intervene with and prevent occurrence of salmonellosis.

Emergence and spread in Taiwan of multidrug-resistant serotypes of nontyphoidal Salmonella

PURPOSE

Antimicrobial resistance of nontyphoidal Salmonella (NTS) is a threat to public health worldwide.

METHODS

A study on longitudinally collected NTS isolates from a medical center in Taiwan from 2011 to 2019 was undertaken. The multidrug resistance (MDR) and extensively drug resistance (XDR) phenotypes were determined according to internationally used definitions. Molecular serotyping was performed on the resistant NTS.

RESULTS

Notably 16.1% (870/5412) of the isolates were MDR, while XDR accounted for 2.1% (111/5412). Both MDR and XDR NTS have increased significantly from 2011 to 2019, especially from 2015 to 2017 (MDR from 9.6% in 2015 to 23.1% 2017; XDR from 1.4% in 2016 to 4.7% in 2017). S. Anatum was the commonest NTS serotype expressing MDR and XDR, in 256/559 (45.8%) and 81/111 (73.0%) of the isolates, respectively, followed by S. Typhimurium and S. Goldcoast. Children < 18 years old contributed to 69.0% of all MDR cases and 64.0% of all XDR cases; majority of them aged less than 5 years.

CONCLUSIONS

Increasing MDR and XDR NTS is a threat to public health. MDR and XDR NTS usually caused gastroenteritis in children < 5 years old. Multiple NTS serotypes expressing MDR and XDR indicate multiple food vehicles involved in the transmission. Proper food hygiene practice should never be over-reinforced.

Prevalence, Clinical Characteristics and Changes of Antibiotic Resistance in Children with Nontyphoidal Salmonella Infections from 2009-2018 in Chongqing, China

Purpose

Nontyphoidal Salmonella (NTS) is a leading bacterial cause for acute gastroenteritis in children. With the increasing use of antibiotics worldwide, antibiotic resistance has become a global problem. However, data on NTS infections and changes in antibiotic resistance among children remain limited in China. We aimed to characterize the prevalence, clinical feature, serotype and the changes of antibiotic resistance of NTS in children in Chongqing.

Methods

501 hospitalized children with NTS infections (confirmed by positive NTS culture) in Children’s Hospital of Chongqing Medical University from January 2009 to December 2018 were included. The clinical data and drug sensitivity test results were retrospectively reviewed and analyzed. Antibiotic resistance in NTS infections was compared between 2009–2013 and 2014–2018.

Results

A total of 501 isolates were detected. Most NTS infections occurred in children under three years old, which mainly occurred between July and October. The numbers of patients with diarrhea, fever, and vomiting were 472 (94.2%), 422 (84.2%) and 146 (29.1%), respectively. Serogroup B (67.5%) was the predominant serogroup isolates. And Salmonella Typhimurium was the most common serotype (79.2%). The study compared the drug resistance of NTS from 2009 to 2013 with that from 2014 to 2018. We found the drug resistance rates of NTS to cefazolin, cefotaxime, ciprofloxacin, levofloxacin and imipenem showed an upward trend. The drug resistance rates of NTS to chloramphenicol, ampicillin, ceftriaxone, cefepime and compound sulfamethoxazole decreased slightly, but still showed high drug resistance rates. And drug resistance rates of NTS to piperacillin/tazobactam and ceftazidime decreased significantly in the last ten years. Multi-drug resistance (MDR) isolates, were detected among 69 cases (13.7%) of 501 children with NTS infections.

Conclusion

The overall antibiotic resistance rates remained at a high level in Chongqing. Continuous surveillance of antibiotic resistance in NTS and control measures such as avoiding unnecessary antibiotic therapy in general NTS gastroenteritis are important. For severe or invasive infections caused by NTS infection in Southwest China, the use of ceftazidime is recommended until antibiotic sensitivity test results are available. And the choice of antibiotics should be based on the curative effect and the antibiotics sensitivity results.

Non-typhoidal Salmonella infections among children in a tertiary hospital in Ningbo, Zhejiang, China, 2012-2019

Background

Non-typhoidal Salmonella (NTS), a common cause of diarrheal enterocolitis, may also cause severe invasive diseases. Limited information on NTS infections in children is available in China.

Methods

We performed a retrospective study of children admitted to the Ningbo Women and Children’s Hospital with culture-confirmed NTS infections between January 2012 and December 2019. Clinical and microbiological information were collected. We compared demographic, clinical and antibiotic resistance variables of invasive NTS (iNTS) infections and non-invasive NTS (non-iNTS) infections, and explored associations between hospitalizations for pediatric NTS infections and temperature and rainfall.

Results

A total of 166 pediatric hospitalizations due to NTS infection were identified during the 8-year study period. Most of the 166 children were <5 years old (93.4%). The primary serotype was Salmonella Typhimurium (62.6%). Of 166 children with NTS infections, 11 had invasive infection. Compared to 155 children with non-iNTS infections, we found that iNTS infections were more likely to occur in infants ≤6 months or children with an underlying medical condition of leukemia at admission, but iNTS infections less often presented with a symptom of diarrhea (P <0.05 in all cases). The resistance rates of non-iNTS isolates to ceftazidime, ceftriaxone, cefepime, and aztreonam were significantly higher than those of iNTS isolates (P <0.05 in all cases). In addition, compared with iNTS isolates, non-iNTS isolates were significantly associated with resistance to ≥4 CLSI (Clinical and Laboratory Standard Institute) classes (P = 0.041, OR: 0.089, 95% CI: 0.009–0.901) and ≥2 first-line treatment agents (P = 0.040, OR: 0.159, 95% CI: 0.028–0.916). On the other hand, we found that seasonal NTS hospitalizations were positively associated with average seasonal temperature (r = 0.961, P = 0.039) and average monthly rainfall (r = 0.921, P <0.001).

Conclusion

Non-iNTS accounts for the majority of infections in this study; infants ≤6 months and children with underlying medical conditions of leukemia are more likely to have invasive infection. The rates of antibiotic resistance in the iNTS isolates are generally lower than those in the non-iNTS isolates. On the other hand, high temperatures and heavy rainfall are positively associated with NTS hospitalizations among children in Ningbo.

Non-typhoidal Salmonella (NTS) infection is a foodborne disease with a global heavy burden. NTS usually causes diarrheal enterocolitis in humans and may also cause severe invasive NTS (iNTS) infections. Antimicrobial agents are not recommended for non-severe NTS diarrhea, but they are recommended for people at risk of severe or invasive infection. However, the recognition of iNTS infection among children is difficult before culture. We studied children who had NTS infections in a tertiary pediatric hospital in Ningbo and found that iNTS infections were more likely to occur in infants ≤6 months or children with an underlying medical condition of leukemia at admission, while diarrhea was more common in children with non-iNTS infections. The high rates of antibiotic resistance among children with NTS in Ningbo calls for continuous NTS surveillance. On the other hand, high temperatures and heavy rainfall were positively associated with NTS hospitalizations among children. These findings may help us to improve measures for the prevention, diagnosis and treatment of NTS infections among children.

Prevalence, serotypes, and antimicrobial resistance of Salmonella isolates from patients with diarrhea in Shenzhen, China

BACKGROUND

Salmonella is one of the main causative agents of diarrhea which results in substantial disease burden. To determine the prevalence, serotype distribution, and antimicrobial resistance profiles of clinical Salmonella isolates in Shenzhen, a 6-year surveillance study was conducted.

RESULTS

A total of 297 (5.7%) Salmonella strains were isolated from stool samples from 5239 patients. Among the 42 serotypes identified, serotype Typhimurium was the most common one which represented 39.7% of the isolates (118), followed by serotype Enteritidis (71, 23.9%), London (12, 4.0%), 4, 5, 12: i: - (11, 3.7%), and Senftenberg (8, 2.7%). A high frequency of resistance was found in ampicillin (70.6%), piperacillin (64.5%), tetracycline (63.5%), and streptomycin (54.3%). Resistance to ampicillin and tetracycline was observed in 95.3% of S. Typhimurium isolates; and nalidixic acid in 93.1% of S. Enteritidis isolates. Resistance to 5 or more antimicrobial agents was found in 78.8% of S. Typhimurium and 69.0% of S. Enteritidis isolates. A decreased susceptibility to ciprofloxacin and levofloxacin was associated with amino acid alteration in gyrA gene. Point mutations without amino acid changes were seen in gyrB, parC, and parE genes.

CONCLUSIONS

A broad range of serotypes are responsible for Salmonellosis in Shenzhen, with Enteritidis and Typhimurium being the most common serotypes. The high level of antibiotic resistance is of public health significance and ongoing monitoring combined with rational use of antibiotics are recommended. Point mutations in gyrA gene might play an important role in the resistance to fluoroquinolones.

Investigation of a Salmonellosis Outbreak Caused by Multidrug Resistant Salmonella Typhimurium in China

The rapid emergence of multidrug resistant Salmonella is a global public-health concern as outbreaks in recent years have mostly been caused by multidrug resistant strains. Here, we evaluated an outbreak in China caused by multidrug resistant Salmonella enterica serovar Typhimurium (S. Typhimurium) by employing an epidemiological and laboratory investigation using conventional methods and whole genome sequencing (WGS). Eleven of the 12 people who participated in a banquet showed gastrointestinal symptoms, and 8S. Typhimurium strains were recovered. Isolated outbreak strains showed multidrug resistance (MDR), and decreased susceptibility to ciprofloxacin, a first-line drug recommended by WHO for clinical treatment of intestinal infections. Antimicrobial resistance (AMR) gene analysis indicated that the MDR phenotype of these outbreak strains may be due to the presence of a number of AMR genes, including the blaOXA-1 and blaTEM-1 β-lactamase genes, which are often plasmid-borne and easily transferred. Further virulence gene analysis indicated that these outbreak strains also carried a large number of virulence genes, including 2 types of Salmonella pathogenicity islands (SPI-1 and SPI-2) and many adhesion-related virulence genes. Cluster analysis based on pulse-field gel electrophoresis data and phylogenetic analysis based on WGS revealed that the outbreak clone was closely related to and thus probably derived from local strains. This outbreak caused by multidrug resistant S. Typhimurium highlights the need for government improved strategies for the prevention and control of Salmonella infections.