Serogroup C1 Research Articles

Investigation of a Salmonella Montevideo Outbreak Related to the Environmental Contamination of a Restaurant Kitchen Drainage System, Québec, Canada, 2020–2021

In May 2020, the Direction de santé publique du CIUSSS de la Capitale-Nationale (DSPu) received a report from the Laboratoire de santé publique du Québec of a cluster of three cases of Salmonella enterica enterica, serogroup C1, serotype Montevideo. The epidemiological investigation identified a total of 67 cases between January 1, 2020, and August 13, 2021, 66% of which were directly linked to a restaurant in the area. The Salmonella strains from most of these cases were found to be identical by whole-genome sequencing (cluster code 2005MontWGS-1QC). The initial inspection of the restaurant by the competent authorities (Ministère de l’agriculture, des pêcheries et de l’alimentation du Québec) – including the evaluation of hygiene and food safety, the search for cases of illness among workers and food sampling – was unable to establish the source of the outbreak. Environmental samples showed that the restaurant’s kitchen drains were contaminated with the same strain of Salmonella Montevideo as the cases in the outbreak. Several cleaning and disinfection methods were used repeatedly. When environmental sampling at the restaurant sites was repeatedly and consecutively negative, cases in the community stopped. The prior occurrence of a fire in the kitchen may have played a role in the contamination of the restaurant drains. In conclusion, public health professionals should consider drainage systems (plumbing) and possible aerosolization of bacteria as a potential source of a restaurant-related salmonellosis outbreak.

CHARACTERIZATION OF FOUR MAIN SALMONELLA SEROVARS, ALBANY, KENTUCKY, MBANDAKA, AND MONTEVIDEO, ASSOCIATED WITH CHICKEN LINES, FARMS, AND SAMPLE SOURCES IN SOUTHERN TAIWAN

Poultry and its products are often referred to as reservoirs of Salmonella to infect humans. Salmonella serovars were determined from samples of terminated eggs (early-terminated eggs, EEs, and late-terminated eggs, LEs) on farms YA (layers), YB (native hybrid broilers, NHCs), and YF (NHCs); one-day-old chicks (OCs) on farm YB; and shoe covers (SCs) on farms YB, YC (broilers), YD (broilers), YE (NHCs), and YF using multiplex PCR and agglutination methods. One hundred isolates were examined for susceptibility to 13 antimicrobials and profiles of pulsotypes and plasmids. Nine serovars were identified as serogroup B Agona and Schwarzengrund, serogroup C1 Montevideo and Mbandaka, serogroup C2 Albany, Kentucky and Newport, serogroup E Weltevreden, and serogroup G Kedougou. Different from those in 2003, Albany, Kentucky, Montevideo, and Mbandaka were the predominant serovars that differed in chromosomal and plasmid variations and antibiogram profiles. Albany and Kentucky isolates had higher resistance levels to the antimicrobials than the Montevideo and Mbandaka isolates. The antibiogram differences among the serovars may be related to the presence of antibiotic resistance genes in Salmonella genomic island 1-F (SGI1-F) and plasmids in Albany isolates. Albany and Kentucky exhibited the largest chromosomal and plasmid variations, respectively. The main serovars associated with embryogenesis termination were Mbandaka and Montevideo in EEs and LEs, Newport in NHCs, and Kedougou in LEs from layers. Furthermore, Montevideo and Agona were the only serovars detected in OCs, and Albany and Kentucky were the main serovars on SCs. Farm management also affected the Salmonella prevalence and predominant serovars.

The Clinical Implication of Serogroup Distribution and Drug Resistance of Non-Typhoidal Salmonella in Children: A Single Center Study in Southern Taiwan during 2004-2019.

Background: A regional antibiotic susceptibility database of certain pathogens is crucial for first-line physicians in terms of providing clinical judgement and appropriate selection of antimicrobial agents. The aim of this study is to update the epidemiological data of Salmonella serogroups and drug resistance in pediatric patients. Methods: This is a single-center retrospective study enrolling patients aged from 0 to 18 years who were hospitalized with cultured proven non-typhoidal Salmonella (NTS) infection from 2004 to 2019. The isolates were collected and the demographic data, serogroups of Salmonella and antimicrobial susceptibilities were further analyzed. Results: A total of 1583 isolates of NTS were collected. Serogroup C2 was prone to cause invasive non-typhoidal salmonellosis (iNTS), especially bacteremia. Patients aged < 2 years were associated with serogroups B and C2 infection, while those aged ≥ 2 years were associated with serogroups D and E infection. The prevalence of serogroup B declined with simultaneous increase in prevalence of serogroups D and E. Serogroups B and E were associated with ceftriaxone resistance, while Serogroup D was less drug-resistant than the others. The prevalence of ceftriaxone-resistant Salmonella had not increased, although more ciprofloxacin-resistant isolates were found in iNTS infection. Conclusions: Age < 2 years is a risk factor of iNTS for children, and the distribution of serogroup changes should be closely monitored. Ceftriaxone is still the drug of choice for treating pediatric iNTS infection, and although no increase was observed in the prevalence of ceftriaxone-resistant strains in this study, continuing surveillance of such cases is warranted.

Molecular Characterization and Antimicrobial Resistance Profiling of Salmonella spp. from Onion Leaves Collected from Wet Markets in Metro Manila, Philippines

Salmonella spp. is the causative agent of salmonellosis outbreaks in poultry and meats, but recent studies have implicated this pathogen in foodborne outbreaks associated with vegetables. Salmonellosis is commonly managed with antibiotics, but antimicrobial resistance has complicated the treatment of the disease. The pathogenesis of Salmonella spp. is based on virulence factors such as plasmid-encoded genes and lipopolysaccharide moieties, which can be detected by PCR and serotyping, respectively. Thirteen (13) isolates previously identified and confirmed as Salmonella spp. using invA gene-targeting assay were isolated from onion leaf samples collected from wet markets in Metro Manila, Philippines. The isolates were characterized based on the presence of plasmid-encoded virulence gene, serogroup and serotype, and antibiotic resistance profiles using the VITEK®2 system. All 13 Salmonella spp. isolates were spvC-negative. O-serotyping revealed the presence of isolates belonging to serogroups C1 (30.8%), C2 (23.0%), and E1 (30.8%). Two isolates (15.4%) did not belong to the serogroups examined in the study. Further, sequence analysis revealed the presence of serovars Newport, Weltevreden, Tennessee, and Anatum. All the isolates were resistant to at least five antimicrobial agents. To our knowledge, this is the first study in the Philippines to establish baseline data for the molecular features and antibiogram profiles of Salmonella spp. isolated in onion leaf samples from selected wet markets in Metro Manila, Philippines. Furthermore, this study is the first report on the occurrence of four different Salmonella serovars from onion leaves. The data obtained in this study could be used as baseline information and guidance in the implementation of the GAP, monitoring programs of the Department of Agriculture, and the formulation of laws and regulations by policymakers that will address safety issues in fresh produce and quality management principles in farm operations.

A Pain in the Neck: An Adolescent with Neck Pain.

A Pain in the Neck: An Adolescent with Neck Pain.

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 <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.

Two homologous Salmonella serogroup C1-specific genes are required for flagellar motility and cell invasion

BackgroundSalmonella is a major bacterial pathogen associated with a large number of outbreaks of foodborne diseases. Many highly virulent serovars that cause human illness belong to Salmonella serogroup C1, and Salmonella ser. Choleraesuis is a prominent cause of invasive infections in Asia. Comparative genomic analysis in our previous study showed that two homologous genes, SC0368 and SC0595 in Salmonella ser. Choleraesuis were unique to serogroup C1. In this study, two single-deletion mutants (Δ0368 and Δ0595) and one double-deletion mutant (Δ0368Δ0595) were constructed based on the genome. All these mutants and the wild-type strain were subjected to RNA-Seq analysis to reveal functional relationships of the two serogroup C1-specific genes.ResultsData from RNA-Seq indicated that deletion of SC0368 resulted in defects in motility through repression of σ28 in flagellar regulation Class 3. Consistent with RNA-Seq data, results from transmission electron microcopy (TEM) showed that flagella were not present in △0368 and △0368△0595 mutants resulting in both swimming and swarming defects. Interestingly, the growth rates of two non-motile mutants △0368 and △0368△0595 were significantly greater than the wild-type, which may be associated with up-regulation of genes encoding cytochromes, enhancing bacterial proliferation. Moreover, the △0595 mutant was significantly more invasive in Caco-2 cells as shown by bacterial enumeration assays, and the expression of lipopolysaccharide (LPS) core synthesis-related genes (rfaB, rfaI, rfaQ, rfaY, rfaK, rfaZ) was down-regulated only in the △0368△0595 mutant. In addition, this study also speculated that these two genes might be contributing to serotype conversion for Salmonella C1 serogroup based on their apparent roles in biosynthesis of LPS and the flagella.ConclusionA combination of biological and transcriptomic (RNA-Seq) analyses has shown that the SC0368 and SC0595 genes are involved in biosynthesis of flagella and complete LPS, as well as in bacterial growth and virulence. Such information will aid to revealing the role of these specific genes in bacterial physiology and evolution within the serogroup C1.

Identification of Novel Sensitive and Reliable Serovar-Specific Targets for PCR Detection of Salmonella Serovars Hadar and Albany by Pan-Genome Analysis.

The accurate and rapid classification of Salmonella serovars is an essential focus for the identification of isolates involved in disease in humans and animals. The purpose of current research was to identify novel sensitive and reliable serovar-specific targets and to develop PCR method for Salmonella C2 serogroups (O:8 epitopes) in food samples to facilitate timely treatment. A total of 575 genomic sequences of 16 target serovars belonging to serogroup C2 and 150 genomic sequences of non-target serovars were analysed by pan-genome analysis. As a result, four and three specific genes were found for serovars Albany and Hadar, respectively. Primer sets for PCR targeting these serovar-specific genes were designed and evaluated based on their specificity; the results showed high specificity (100%). The sensitivity of the specific PCR was 2.8 × 101–103 CFU/mL and 2.3 × 103–104 CFU/mL for serovars Albany and Hadar, respectively, and the detection limits were 1.04 × 103–104 CFU/g and 1.16 × 104–105 CFU/g in artificially contaminated raw pork samples. Furthermore, the potential functions of these serovar-specific genes were analysed; all of the genes were functionally unknown, except for one specific serovar Albany gene known to be a encoded secreted protein and one specific gene for serovars Hadar and Albany that is a encoded membrane protein. Thus, these findings demonstrate that pan-genome analysis is a precious method for mining new high-quality serovar-targets for PCR assays or other molecular methods that are highly sensitive and can be used for rapid detection of Salmonella serovars.

Mining and evaluating novel serovar-specific Salmonella C1 serogroup genes by polymerase chain reaction analysis

Salmonella is a food-borne pathogen that causes worldwide infections in humans and animals. Over 2600 Salmonella serovars have been identified, and serogroup C1 (O:6, 7 epitopes) contains highly diverse serovars associated with high pathogenicity. Here, we aimed to develop a reliable polymerase chain reaction (PCR) method for detecting serovar-specific markers of Salmonella serogroup C1, with greater reliability and lower complexity than current methods. We identified three, two, four, and one novel genes unique to the Infantis, Rissen, Braenderup, and Virchow serovars. The PCR primers targeting these genes were specific for the target serovars. The detection limits of the PCR assays using 9 pairs of primers were 102–103 colony-forming units (CFUs)/mL and 104–105 CFU/g in pure bacterial cultures and artificially contaminated raw pork samples, respectively. No false-positive or false-negative results were obtained with 45 food samples, as determined by comparison with biochemical tests and traditional serotyping methods. The potential functions of all serovar-specific genes identified are unknown, except for one Rissen-specific gene that encodes a secreted protein. Our results imply that all 10 novel, specific genes can be considered as useful targets for detecting the Salmonella Infantis, Rissen, Braenderup, and Virchow serovars in food.

Safety and efficacy of a novel inactivated trivalent Salmonella enterica vaccine in chickens

Food poisoning in humans caused by Salmonella enterica remains a significant global public health concern, with the majority of infections associated with the consumption of contaminated eggs or poultry products. The safety and efficacy of a novel inactivated trivalent Salmonella enterica vaccine containing in addition to Salmonella serovars Enteritidis (O:9, serogroup D) and Typhimurium (O:4, serogroup B) also serovar Infantis (O:7, serogroup C1) formulated with an aluminium hydroxide-gel adjuvant was evaluated under field conditions. A total of 10,229 broiler breeder pullets, housed under commercial conditions, were vaccinated at 10 and 17 weeks of age by the intramuscular route in the breast muscle. The vaccine was safe with no local or systemic reactions or adverse effects on bird performance related to the vaccine detected. Vaccination resulted in notable increases in serovar specific antibodies that were maintained until at least 56 weeks of age. Vaccinated birds subjected to homologous challenges around onset of lay showed significantly reduced faecal shedding and organ invasion. Following heterologous challenge with S. Hadar (O:8, serogroup C2) faecal shedding was significantly reduced. These results demonstrate that this novel vaccine could play a significant role in a comprehensive Salmonella control programme intended to reduce both the incidence of food poisoning in humans and the use of antibiotics during poultry production.

Overview of the Antimicrobial Resistance of Salmonella Recovered from U.S. Poultry Processing Plants

The objectives of this study were to analyze the results of antimicrobial susceptibility testing on Salmonella isolated from poultry carcass and parts rinsates using a scoring system for antimicrobial resistance (AMR) and to deter-mine whether the resistance of Salmonella to selected antimicrobials critically or highly important to human medicine changed from 2017 to 2019. Samples were collected from 26 plants in the United States, analyzed for the presence of Salmonella, and tested for susceptibility to 12 antimicrobials (n=734 for 8 antimicrobials;&amp;nbsp;n=597 for 4 antimicrobials). The multidrug resistance (MDR) scores and AMR scores remained the same over time (P&amp;gt;0.05); however, MDR and AMR differed (P&amp;lt;0.0001) by serogroup and serogroup-by-year interactions. Most notably, MDR—and AMR for 7 out of the 12 antimicrobials—was greater (P&amp;lt;0.05) in serogroup C1 than other serogroups and/or lower (P&amp;lt;0.05) in serogroup D1 than other serogroups. The effect year-by-serogroup was also significant for MDR (P&amp;lt;0.0001) and—for 8 out of the 12 antimicrobials—AMR (P&amp;lt;0.05); differences (P&amp;lt;0.05) across years were identified in serogroup C1, B, and C2 but were highly variable. Resistance to ciprofloxacin and ceftriaxone,“highest priority critically important antimicrobials”to human medicine, were not different (P&amp;gt;0.05) across years, but there were significant (P&amp;lt;0.05) serogroup and serogroup-by-year effects for ceftriaxone resistance. Interestingly, gentamicin resistance across years differed (P&amp;lt;0.05) in serogroup B and C. Overall, mean Salmonella MDR and AMR scores were stable from year to year, but shifts in AMR in Salmonella serogroups across years were identified, emphasizing the need to continue monitoring AMR in Salmonella isolated from poultry products in the interest of food safety and human health.

Evaluation of 3-week-old layer chicks intratracheally challenged with Salmonella isolates from serogroup c1 (O:6,7) and Salmonella Enteritidis

ABSTRACTWith the exception to Salmonella enterica serotype Typhimurium and S. Enteritidis (serogroups B [O:4] and D [O:9], respectively), there have been very few studies conducted on the respiratory tract as route of infection in chickens with salmonellas from serogroup C1 (O:6,7). Therefore, the purpose of this present study was to determine the potential organ invasion by Salmonella enterica serotype Potsdam (SP), S. Mbandaka (SM), and S. Infantis (SI) from serogroup C1 (O:6,7) and compare their characteristics with those of S. Enteritidis (SE) on intratracheally (IT) challenged 3-week-old layer chicks. A total of 360 one-day-old White Leghorn layer chicks were acquired from a commercial hatchery and randomly assigned into four treatment groups (SP, SM, SI, and SE, respectively), consisting of three independent trials. Chicks were grown up to 21 days (3 weeks) and IT-challenged thereafter with 106 CFU of respective salmonella organisms per group (n = 30). Chicks (n = 5) were humanely sacrificed every 24 h for 6 days post-IT infection and organs such as lung, heart, liver, spleen, kidney and caecal content were cultured for salmonella. All treatment groups exhibited colonization of lungs and caecal contents at 1 d (P = 0.475) and 4 d (P = 0.696) post-IT infection, respectively. There was no isolation of SP, SM, and SI in heart, liver, spleen, and kidney. In contrast, SE was obtained from heart, liver, and spleen of IT-infected chicks. The findings of this study contribute to a better understanding of the importance of the respiratory route in salmonella infection in poultry.

Deletions in guaBA and htrA but not clpX or rfaL constitute a live-attenuated vaccine strain of Salmonella Newport to protect against serogroup C2-C3 Salmonella in mice

ABSTRACT Non-typhoidal Salmonella (NTS) are a leading cause of foodborne infections worldwide, and serogroups B, C1, C2-C3 and D are the most common serogroups associated with human disease. While live vaccine candidates that protect against S. Typhimurium (serogroup B) and S. Enteritidis (serogroup D) have been described by us and others, far less effort has been directed towards vaccines that target either serogroup C1 or C2-C3 Salmonella. Here we describe a Salmonella Newport-based live-attenuated vaccine (serogroup C2-C3). Deletion of the genes clpX or rfaL, previously used in live vaccines to attenuate S. Typhimurium and/or S. Enteritidis, failed to attenuate S. Newport. However, we found that deletion of either guaBA or htrA raised the 50% lethal dose of S. Newport in an intraperitoneal infection model in BALB/c mice. Our live-attenuated vaccine candidate CVD 1966 (S. Newport ΔguaBA ΔhtrA) elicited strong antibody responses against COPS, flagellin and outer membrane proteins when administered intraperitoneally or orally. Following lethal challenge with the parental virulent strain of S. Newport, we observed vaccine efficacies of 53% for immunization via the intraperitoneal route and 47% for immunization via the oral route. Following intraperiteonal immunization, the vaccine also significantly reduced the bacterial burden of challenge organisms in the liver and spleen. Interestingly, reducing the LPS chain length by deleting rfaL did not induce a stronger immune response towards surface antigens, and failed to elicit any protection against lethal homologous challenge. In conclusion, we have developed a live-attenuated Salmonella serogroup C2-C3 vaccine that we are further evaluating.

Utility of a blood culture time to positivity-incorporated scoring model in predicting vascular infections in adults with nontyphoid Salmonella bacteremia.

Vascular infections (VI) are potentially catastrophic complications of nontyphoid Salmonella (NTS). We aimed to develop a scoring model incorporating information from blood culture time to positivity (TTP-NTSVI) and compared the prediction capability for VI among adults with NTS bacteremia between TTP-NTSVI and a previously published score (Chen-NTSVI). This retrospective cohort study enrolled 217 adults with NTS bacteremia ≧ 50 years old. We developed a TTP-NTSVI score by multiple logistic regression modeling to identify independent predictors for imaging-confirmed VI and assigned a point value weighting by the corresponding natural logarithm of the odds ratio for each model predictor. Chen-NTSVI score includes hypertension, male sex, serogroup C1, coronary arterial disease (CAD) as positive predictors, and malignancy and immunosuppressive therapy as negative predictors. The prediction capability of the two scores was compared by area under the receiver operating characteristic curve (AUC). The mean age was 68.3±11.2 years-old. Serogroup D was the predominant isolate (155/217, 71.4%). Seventeen (7.8%) patients had VI. Four independent predictors for VI were identified: male sex (24.9 [2.59-239.60]; 6) (odds ratio [95% confidence interval]; assigned score point), peripheral arterial occlusive disease (9.41 [2.21-40.02]; 4), CAD (4.0 [1.16-13.86]; 3), and TTP <10h (4.67 [1.42-15.39]; 3). Youden's index showed best cutoff value of ≧7 with 70.6% sensitivity and 82.5% specificity. TTP-NTSVI score had higher AUC than Chen-NTSVI (0.851 vs 0.741, P=0.039). While the previously reported scoring model performed well, a TTP-incorporated scoring model was associated with improved capability in predicting NTSVI.

Characterization of Invasive Salmonella Serogroup C1 Infections in Mali.

.Nontyphoidal Salmonella (NTS) are the leading cause of foodborne infections worldwide and a major cause of bloodstream infections in infants and HIV-infected adults in sub-Saharan Africa (SSA). Salmonella Typhimurium (serogroup B) and Salmonella Enteritidis (serogroup D) are the most common serovars in this region. However, data describing rarer invasive NTS serovars, particularly those belonging to serogroups C1 and C2, circulating in SSA are lacking. We previously conducted systematic blood culture surveillance on pediatric patients in Bamako, Mali, from 2002 to 2014, and the results showed that serovars Typhimurium and Enteritidis accounted for 32% and 36% of isolates, respectively. Here, we present data on 27 Salmonella serogroup C1 strains that were isolated during this previous study. The strains were typed by serum agglutination and multilocus sequence typing (MLST). Sixteen strains were Salmonella Paratyphi C, four were Salmonella Colindale, and two were Salmonella Virchow. Interestingly, five strains were identified as the very rare Salmonella Brazzaville using a combination of serum agglutination and flagellin gene typing. Phenotypic characterization showed that Salmonella Brazzaville produced biofilm and exhibited catalase activity, which were not statistically different from the gastroenteritis-associated Salmonella Typhimurium sequence type (ST) 19. All tested Salmonella Paratyphi C strains were poor biofilm producers and showed significantly less catalase activity than Salmonella Typhimurium ST19. Overall, our study provides insight into the Salmonella serogroup C1 serovars that cause invasive disease in infants in Mali. In addition, we show that MLST and flagellin gene sequencing, in association with traditional serum agglutination, are invaluable tools to help identify rare Salmonella serovars.

Bacteriophage SP6 encodes a second tailspike protein that recognizes Salmonella enterica serogroups C2 and C3

SP6 is a salmonella phage closely related to coliphage K1-5. K1-5 is notable in that it encodes two polysaccharide-degrading tailspike proteins, an endosialidase that allows it to infect E. coli K1, and a lyase that enables it to infect K5 strains. SP6 is similar to K1-5 except that it encodes a P22-like endorhamnosidase tailspike, gp46, allowing it to infect group B Salmonella. We show here that SP6 can also infect Salmonella serogroups C2 and C3 and that a mutation in a putative second tailspike, gp47, eliminates this specificity. Gene 47 was fused to the coding region of the N-terminal portion of the Pseudomonas aeruginosa R2 pyocin tail fiber and expressed in trans such that the fusion protein becomes incorporated into pyocin particles. These pyocins, termed AvR2-SP47, killed serogroups C2 and C3Salmonella. We conclude that SP6 encodes two tail proteins providing it a broad host range among Salmonella enterica.

Characteristics of nontyphoidal Salmonella gastroenteritis in Taiwanese children: A 9-year period retrospective medical record review.

Nontyphoidal Salmonella is among the most common causes of acute pediatric gastroenteritis in Taiwan. It is important to study antibiotic resistance patterns in nontyphoidal Salmonella isolated from children. Therefore, the objective of this study was to investigate the prevalence of serogroups and susceptibility to antimicrobial nontyphoidal Salmonella isolated from Taiwanese children with gastroenteritis. A retrospective review of the medical records of patients aged under 18 years with a diagnosis of acute gastroenteritis at a regional hospital located in southern Taiwan from August 2000 to August 2009 was conducted. Patients whose records documented stool cultures positive for nontyphoidal Salmonella underwent serogrouping and antimicrobial susceptibility testing. Of the 1938 patients diagnosed with acute gastroenteritis, 100 (5.2%) had nontyphoidal Salmonella infections. Most of the cases of nontyphoidal Salmonella gastroenteritis occurred during the summer months of July and August. The most common Salmonella strains isolated were classified as belonging to serogroup B (51%). Three cases had blood cultures that tested positive for nontyphoidal Salmonella, all of which were classified as belonging to serogroup C2. Isolates from the stool cultures of 23 cases that occurred between 2007 and 2009 were further tested to determine their antimicrobial susceptibility profiles, and 87% of these isolates were sensitive to two common third-generation cephalosporins (cefotaxime and ceftriaxone). In conclusion, the results of this nine-year period medical record review study suggested that although extended-spectrum cephalosporins were more effective than ampicillin and ciprofloxacin in treating childhood nontyphoidal Salmonella gastroenteritis, only 87% of isolates were susceptible to these agents. Prevention through proper hygienic practices to minimize potential exposure to nontyphoidal Salmonella is clearly a better strategy than treating patients with antibiotics following the incidence of infection.

Salmonella Enteritidis predominance determined by serotyping andreal-time PCR in poultry-derived food and avian isolates

This study aimed to determine Salmonella enterica subspecies enterica serovar Enteritidis (SE) presence by conventional serotyping and SE-specific real-time PCR (SE-rPCR) in poultry-derived food and avian isolates in our laboratory Salmonella spp. collection. Conventional serotyping indicated that 32 (8 chicken meat, 10 egg, 14 avian) out of 56 (57%) isolates were SE, whereas 8 (3 chicken meat, 2 turkey meat, 3 avian) (14%) isolates were serogroup B, 6 (1 chicken meat, 1 egg, 4 avian) (11%) were serogroup C1, 4 (3 chicken meat, 1 turkey meat) (7%) were serogroup C2-C3, 4 (3 chicken meat, 1 turkey meat) (7%) were serogroup E4, and 2 (avian) (4%) isolates were categorized as nonserogrouped/nonserotyped. Thirty-three (8/18 chicken meat, 10/11 egg, 15/23 avian) out of 56 (59%) Salmonella isolates were positive by SE-rPCR. SE was determined as the most prevalent serotype in both of the tests regardless of the sample type. Conventional serotyping and SE-rPCR results were in agreement in all but 1 isolate. Considerably high relative accuracy (98%), sensitivity (100%), and specificity (96%) with almost perfect agreement between the two methods (Cohen's kappa = 0.96) indicated SE-rPCR as a reliable tool in the rapid identification of SE isolates to complement conventional serotyping.

Salmonella Persistence within the Peripheral Lymph Nodes of Cattle following Experimental Inoculation

Utilizing a transdermal method of inoculation developed in our laboratory, the duration of infection of Salmonella in the peripheral lymph nodes of steers was examined. Thirty-six Holstein steers (mean body weight of 137 kg) were inoculated with Salmonella Montevideo (day 0) on each lower leg and both sides of the back and abdomen. Calves were euthanized beginning at 6 h and subsequently on each of days 1, 2, 4, 7, 9, 11, 14, and 21 postinoculation (four animals each time). The subiliac, popliteal, and superficial cervical (prescapular) lymph nodes were collected and cultured (quantitatively and qualitatively) for the challenge strain of Salmonella. The challenge strain was detected via direct culture within the lymph nodes at 6 h postinoculation and on each subsequent necropsy date. Salmonella levels in lymph node were 0.8 to 1.8 log CFU/g. Lymph nodes were generally positive after enrichment culture throughout the experiment. Salmonella elimination appeared to begin approximately 14 days postinoculation. However, elimination was not completed by day 21; therefore, a second experiment was conducted identical to the first except that the time from inoculation to necropsy was extended. Salmonella was recovered via direct culture on each of the necropsy days, and results in general were similar to those of experiment I, except that on days 20, 24, and 28 isolates from serogroups C2 and E1 were identified in addition to the inoculation strain C1 in multiple animals. The data from both experiments indicate that after a single inoculation event, Salmonella would be completely cleared by approximately 28 days. Further research with expanded times between inoculation and necropsy is required for verification.

Oral vaccination with a rough attenuated mutant of S. Infantis increases post-wean weight gain and prevents clinical signs of salmonellosis in S. Typhimurium challenged pigs

We show that oral inoculation of 14day old conventional piglets with a rough attenuated Salmonella enterica serovar Infantis 1326/28Фr (serogroup C1), 24h prior to oral challenge with S. enterica serovar Typhimurium 4/74 (serogroup B), resulted in significant weight gain (~10%) measured at 14days post-weaning (38days of age). Two days after challenge the S. Typhimurium induced stunting and, in some cases loss, of villi but this was prevented by pre-inoculation with the S. Infantis strain. The clinical signs of disease associated with S. Typhimurium 4/74 challenge and faecal shedding were also significantly (P<0.05) reduced by pre-inoculation with the S. Infantis mutant. Pre-inoculation of pigs with the S. Infantis mutant also increased weight gain in pigs challenged with pathogenic Escherichia coli. However, Mycobacterium bovis BCG, an unrelated intracellular bacterium, did not protect against challenge with S. Typhimurium 4/74.