Comparison of four molecular methods to type Salmonella Enteritidis strains

The CRISPR genotypes and genetic diversity of different serogroups of nontyphoidal Salmonella in Guizhou Province, 2013-2018

Nontyphoidal Salmonella is a bacterial and foodborne pathogen that poses a severe public health threat. However, the genetic diversity of different serogroups of nontyphoidal Salmonella in Guizhou is unknown. This study aimed to obtain the RNA secondary structure of the typical direct repeat sequences, the characteristics of clustered regularly interspaced short palindromic repeats (CRISPR) genotypes, and the genetic diversity of different serogroups of nontyphoidal Salmonella strains. The 342 nontyphoidal Salmonella strains were collected from nine cities (prefectures) of Guizhou province during 2013-2018, serotyped by slide agglutination, and examined the molecular genotypes by CRISPR method. The strains were divided into five serogroups. The dominant serogroup was group B (47.08%), followed by group D1 (36.55%). One hundred and thirty-five CRISPR genotypes were detected with 108 novel spacer sequences amongst 981 unique spacer sequences. The diversity of nontyphoidal Salmonella CRISPR loci was not only the deletion, duplication, or point mutation of spacer sequences but also the acquisition of new spacer sequences to form novel genotypes. The CRISPR genotyping was an effective typing method that could reveal the genetic diversity of different nontyphoidal Salmonella serotypes except for S. Enteritidis.

Antimicrobial resistance and genetic background of non-typhoidal Salmonella enterica strains isolated from human infections in São Paulo, Brazil (2000-2019)

Salmonella enterica causes Salmonellosis, an important infection in humans and other animals. The number of multidrug-resistant (MDR) phenotypes associated with Salmonella spp. isolates is increasing worldwide, causing public health concern. Here, we aim to characterize the antimicrobial-resistant phenotype of 789 non-typhoidal S. enterica strains isolated from human infections in the state of São Paulo, Brazil, along 20 years (2000-2019). Among the non-susceptible isolates, 31.55, 14.06, and 13.18% were resistant to aminoglycosides, tetracycline, and β-lactams, respectively. Moreover, 68 and 11 isolates were considered MDR and Extended Spectrum β-Lactamase (ESBL) producers, respectively, whereas one isolate was colistin-resistant. We selected four strains to obtain a draft of the Genome Sequence; one S. Infantis (ST32), one S. Enteritidis (ST11), one S. I 4,[5],12:i:- (ST19), and one S. Typhimurium (ST313). Among them, three presented at least one of the following antimicrobial resistance genes (AMR) linked to mobile DNA: bla_TEM-1B, dfrA1, tetA, sul1, floR, aac(6')-laa, and qnrE1. This is the first description of the plasmid-mediated quinolone resistance (PMQR) gene qnrE1 in a clinical isolate of S. I 4,[5],12:i:-. The S. Typhimurium is a colistin-resistant isolate, but did not harbor mcr genes, but it presented mutations within the mgrB, pmrB, and pmrC regions that might be linked to the colistin-resistant phenotype. The virulence pattern of the four isolates resembled the virulence pattern of the highly pathogenic S. Typhimurium UK-1 reference strain in assays involving the in vivo Galleria mellonella model. In conclusion, most isolates studied here are susceptible, but a small percentage present an MDR or ESBL-producer and pathogenic phenotype. Sequence analyses revealed plasmid-encoded AMR genes, such as β-lactam and fluoroquinolone resistance genes, indicating that these characteristics can be potentially disseminated among other bacterial strains.

Genotypic correlation between Salmonella Enteritidis isolates from broiler breeders and hatchery flocks

In this study, Salmonella Enteritidis strains isolated from dust and environmental materials from different flocks located in Turkey’s Western Black Sea region were examined by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). A total of 59 S. Enteritidis strains isolated from broiler breeder and hatchery flocks, and one S. Enteritidis strain isolated from a stool sample of a farm worker were examined. PFGE analysis revealed two major PFGE groups and nine different macro restriction profiles. It was determined that 85% (51/60) of the strains were close to each other and comprised Group I. All S. Enteritidis strains had the same sequence type (ST): ST11. Isolation of strains with a single genotype suggests that there may be a cross transmission between the flocks.

Antimicrobial Resistance and CRISPR Typing Among Salmonella Isolates From Poultry Farms in China

Although knowledge of the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas system has been applied in many research areas, comprehensive studies of this system in Salmonella, particularly in analysis of antibiotic resistance, have not been reported. In this work, 75 Salmonella isolates obtained from broilers or broilers products were characterized to determine their antimicrobial susceptibilities, antibiotic resistance gene profiles, and CRISPR array diversities, and genotyping was explored. In total, 80.00% (60/75) of the strains were multidrug resistant, and the main pattern observed in the isolates was CN-AZM-AMP-AMC-CAZ-CIP-ATM-TE-SXT-FOS-C. The resistance genes of streptomycin (aadA), phenicol (floR-like and catB3-like), β-lactams (bla _TEM, bla _OXA, and bla _CTX), tetracycline [tet(A)-like], and sulfonamides (sul1 and sul2) appeared at higher frequencies among the corresponding resistant isolates. Subsequently, we analyzed the CRISPR arrays and found 517 unique spacer sequences and 31 unique direct repeat sequences. Based on the CRISPR spacer sequences, we developed a novel typing method, CRISPR locus three spacer sequences typing (CLTSST), to help identify sources of Salmonella outbreaks especially correlated with epidemiological data. Compared with multi-locus sequence typing (MLST), conventional CRISPR typing (CCT), and CRISPR locus spacer pair typing (CLSPT), discrimination using CLTSST was weaker than that using CCT but stronger than that using MLST and CLSPT. In addition, we also found that there were no close correlations between CRISPR loci and antibiotics but had close correlations between CRISPR loci and antibiotic resistance genes in Salmonella isolates.

Multilocus sequence typing of multidrug-resistant Salmonella strains circulating in poultry farms of Bangladesh

Salmonella is one of the most important foodborne zoonotic pathogens, and becoming multidrug-resistant (MDR), which represents a serious public health concern worldwide. This study aimed to identify the circulating MDR strains of Salmonella through cutting edge molecular techniques including gene specific PCR, RAPD-PCR, ribosomal gene sequencing, and multilocus sequence types (MLST) in the poultry industry of Bangladesh. Two hundred Salmonella isolates were retrieved from 154 samples comprising droppings (n = 60), cloacal swabs (n = 60), feeds (n = 14), feeding water (n = 14), and handler's swab (n = 6) from 14 commercial layer farms of Bangladesh. The isolates were confirmed as Salmonella through invA gene specific PCR, and further genotyping was done by RAPD-PCR, and 16S rRNA sequencing. The isolates were distributed into 18 different genotypes according to RAPD typing. The phylogenetic analysis identified three diverging phylogroups such as S. enterica Litchfield, S. enterica Enteritidis and S. enterica Kentucky with 11, 8, and 6 strains, respectively. The in vitro antibiogram profiling the Salmonella isolates through disc diffusion method using 13 commercially available antibiotics revealed highest resistance against doxycycline (91.5%) followed by tetracycline and ampicillin (86.0%, in each), and 72.0% isolates as MDR, being resistant to ≥ 5 antibiotics. The MLST typing was carried out based on the PCR amplification of seven housekeeping genes (aroC, hisD, hemD, purE, secA, thrA, and dnaN). MLST typing also revealed three sequence types (STs) such as ST11, ST198, and ST214 in these isolates, and eBURST analysis showed ST11 as the founder genotype. The three STs were highly resistant to tetracyclines and quinolone group of antibiotics, and all of the isolates harboring S. enterica Litchfield showed the highest resistance. Circulating common MLSTs with MDR properties in different farms confirmed the possibility of a common route of intra-farm transmission. We report for the first time of the association serovar Litchfield (ST11) in avian salmonellosis with MDR properties which is an urgent public health concern in Bangladesh.

Genomic Characterization of Antimicrobial Resistance in Food Chain and Livestock-Associated Salmonella Species

Simple Summary

In the era of the COVID-19 global pandemic, antimicrobial resistance is looming as an imminent threat and challenge to human public health. Antimicrobial resistance is a major global threat of increasing concern to human and animal health. It also has implications for both food safety and food security and the economic well-being of millions of humans. Among other zoonotic infectious diseases, antimicrobial resistance in food chain and livestock-associated pathogens such as Salmonella is of great concern. In the present study, the genomic characterization of antimicrobial resistance in food chain and livestock-associated Salmonella was summarized. Several antimicrobial resistance determinants were reported in Salmonella isolated from food chain animals and livestock. Monitoring of antimicrobial resistance in Salmonella in livestock and food chain animals through genomic characterization is significant to control and protect humans from the threat of antimicrobial resistance. Salmonella, a foodborne zoonotic enterobacterium species can transmit antimicrobial resistance from the microbiome of animals to humans. This study summarizes the genomic characterization of antimicrobial resistance in Salmonella species with special focus on resistance against carbapenems and colistin which are the last resort antibiotics used against infections caused by multidrug resistant bacteria. The present review aims to draw attention to prudent use of antibiotics, a good example of the One Health concept.

Abstract

The rising trend of antimicrobial resistance (AMR) by foodborne bacteria is a public health concern as these pathogens are easily transmitted to humans through the food chain. Non-typhoid Salmonella spp. is one of the leading foodborne pathogens which infect humans worldwide and is associated with food and livestock. Due to the lack of discovery of new antibiotics and the pressure exerted by antimicrobial resistance in the pharmaceutical industry, this review aimed to address the issue of antibiotic use in livestock which leads to AMR in Salmonella. Much attention was given to resistance to carbapenems and colistin which are the last-line antibiotics used in cases of multi drug resistant bacterial infections. In the present review, we highlighted data published on antimicrobial resistant Salmonella species and serovars associated with livestock and food chain animals. The importance of genomic characterization of carbapenem and colistin resistant Salmonella in determining the relationship between human clinical isolates and food animal isolates was also discussed in this review. Plasmids, transposons, and insertion sequence elements mediate dissemination of not only AMR genes but also genes for resistance to heavy metals and disinfectants, thus limiting the therapeutic options for treatment and control of Salmonella. Genes for resistance to colistin (mcr-1 to mcr-9) and carbapenem (blaVIM-1, blaDNM-1, and blaNDM-5) have been detected from poultry, pig, and human Salmonella isolates, indicating food animal-associated AMR which is a threat to human public health. Genotyping, plasmid characterization, and phylogenetic analysis is important in understanding the epidemiology of livestock-related Salmonella so that measures of preventing foodborne threats to humans can be improved.

Comparison of conventional molecular and whole-genome sequencing methods for subtyping Salmonella enterica serovar Enteritidis strains from Tunisia

We sought to determine the relative value of conventional molecular methods and whole-genome sequencing (WGS) for subtyping Salmonella enterica serovar Enteritidis recovered from 2000 to 2015 in Tunisia and to investigate the genetic diversity of this serotype. A total of 175 Salmonella Enteritidis isolates were recovered from human, animal, and foodborne outbreak samples. Pulsed-field gel electrophoresis (PFGE), multiple locus variable-number tandem repeat analysis (MLVA), and whole-genome sequencing were performed. Eight pulsotypes were detected for all isolates with PFGE (DI = 0.518). Forty-five Salmonella Enteritidis isolates were selected for the MLVA and WGS techniques. Eighteen MLVA profiles were identified and classified into two major clusters (DI = 0.889). Core genome multilocus typing (cgMLST) analysis revealed 16 profiles (DI = 0.785). Whole-genome analysis indicated 660 single-nucleotide polymorphism (SNP) divergences dividing these isolates into 43 haplotypes (DI = 0.997). The phylogenetic tree supported the classification of Salmonella Enteritidis isolates into two distinct lineages subdivided into five clades and seven subclades. Pairwise SNP differences between the isolates ranged between 302 and 350. We observed about 311 SNP differences between the two foodborne outbreaks, while only less or equal to 4 SNP differences within each outbreak. SNP-based WGS typing showed an excellent discriminatory power comparing with the conventional methods such as PFGE and MLVA. Besides, we demonstrate the added value of WGS as a complementary subtyping method to discriminate outbreak from non-outbreak isolates belonging to common subtypes. It is important to continue the survey of Salmonella Enteritidis lineages in Tunisia using WGS.

Highly clonal relationship among Salmonella Enteritidis isolates in a commercial chicken production chain, Brazil

In this study, we described the comparison among pulsed-field gel electrophoresis (PFGE), random amplified polymorphic DNA (RAPD), ribotyping, and PCR-ribotyping methods for subtyping Salmonella Enteritidis isolated from an industrial chicken production chain. One hundred and eight S. Enteritidis were isolated at all stages of poultry meat processing plant. These isolates were pheno- and genotypically characterized by using antimicrobial susceptibility test, phage typing, RAPD, PFGE, ribotyping, and PCR-ribotyping. The highest antibiotic resistance rates were observed for enrofloxacin (18.5%) followed by furazolidone (15.7%), cefoxitin (1.8%), ciprofloxacin, and ampicillin with 0.9% each one, while seven isolates (6.4%) were pan-susceptible. Most strains belonged to the globally disseminated phage type PT4 (n = 74; 69.2%). Additionally, we identified strains belonging to phage types PT1 (n = 19; 17.8%) and PT7a (n = 14; 13.1%). Moreover, our results showed that these four molecular methods indicate similar results showing high similarity (≥ 90%) among S. Enteritidis strains, suggesting that these isolates appear to be from a common ancestor being spread at all stages of the poultry production chain. In summary, the combined molecular approaches of these methods remain a suitable alternative to efficiently subtyping S. Enteritidis in the absence of high-resolution genotyping methods and these results may serve as a baseline study for development of mitigation strategies.

High similarity and high frequency of virulence genes among Salmonella Dublin strains isolated over a 33-year period in Brazil

Salmonella Dublin is a strongly adapted serovar that causes enteritis and/or systemic disease with high rates of mortality in cattle and occasionally infects humans. Despite the importance of this serovar, there is a lack of studies in Brazil. The aim of this study was to characterize the genetic diversity of 112 S. Dublin strains isolated from humans and animals in Brazil by CRISPR and CRISPR-MVLST and the relatedness among strains by MLST. In addition, the frequency of some important virulence genes was verified. The strains studied belonged to nine different sequence types, being all of them single- or double-locus variants of the ST10. CRISPR discriminated the strains into 69 subtypes with a similarity ≥ 84.4% and CRISPR-MVLST into 72 subtypes with a similarity ≥ 84.7%. The virulence genes ratB, lpfA, mgtC, avrA, sopB, sopE2, sifA, sseA, ssrA, csgA, fliC, and sinH were found in all the strains studied, while spvB, spvC, sodCl, rpoS, sipA, sipD, invA, and hilA were detected in ≥ 93.7% of the strains. In conclusion, the high similarity among the strains reinforces the clonal nature of the strains of this serovar that may have descended from a common ancestor that little differed over 33 years in Brazil. CRISPR and CRISPR-MVLST showed to be good alternatives to type S. Dublin strains. MLST suggested that S. Dublin strains from Brazil were phylogenetically related to strains from other parts of the globe. Moreover, the high frequency of virulence genes among the strains studied reinforces the capacity of S. Dublin to cause invasive diseases.

Antimicrobial resistance and molecular genotyping of Salmonella enterica serovar Enteritidis clinical isolates from Guizhou province of Southwestern China

Salmonella enterica serovar Enteritidis (S. Enteritidis) is the most common and essential serotype that causes salmonellosis in Guizhou province. This study aimed to investigate the antimicrobial resistance (AMR) and molecular genotyping of 79 S. Enteritidis clinical isolates from 2011 to 2016 in Guizhou, China. Antimicrobial resistance and minimum inhibitory concentrations (MICs) of S. Enteritidis clinical isolates were detected by micro broth dilution method against ten classes 16 antimicrobial agents, and molecular genotyping were examined by pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem repeat analysis (MLVA). All (100%) isolates showed resistance to at least one antimicrobial. Resistance to nalidixic acid (98.7%) was the highest, followed by sulfamethoxazole (87.3%) and ampicillin (77.2%). The majority of isolates (92.4%) showed decreased susceptibility to ciprofloxacin. Resistance to the third and fourth-generation cephalosporins was observed. Twenty-six AMR profiles were observed, and the predominant AMR profile was ampicillin-streptomycin-sulfamethoxazole-amoxicillin/clavulanic acid-nalidixic acid. A high burden of multidrug resistance (MDR) (81.0%) was found. Seventy-nine S. Enteritidis isolates were divided into 33 different pulsotypes (PTs), and the most frequent PT was PT18. Twenty-six different MLVA types (MTs) were generated with seven VNTR loci analysis of these isolates. The dominant PTs and MTs were persistent during 2011-2016. S. Enteritidis clinical isolates showed higher genetic diversity using PFGE combined with MLVA grouped into 60 PT-MT genotypes. No correlation was observed between genotypes, AMR profiles and geographic location. These data revealed the characteristics of AMR and molecular genotyping of S. Enteritidis clinical isolates in Guizhou province. These results highlight that strengthening the AMR and molecular genotyping surveillance is essential to prevent and control salmonellosis in Guizhou. PFGE combined with MLVA should be powerful tools for the molecular genotyping of S. Enteritidis isolates.

Communicable Disease Surveillance Ethics in the Age of Big Data and New Technology

Surveillance is essential for communicable disease prevention and control. Traditional notification of demographic and clinical information, about individuals with selected (notifiable) infectious diseases, allows appropriate public health action and is protected by public health and privacy legislation, but is slow and insensitive. Big data-based electronic surveillance, by commercial bodies and government agencies (for profit or population control), which draws on a plethora of internet- and mobile device-based sources, has been widely accepted, if not universally welcomed. Similar anonymous digital sources also contain syndromic information, which can be analysed, using customised algorithms, to rapidly predict infectious disease outbreaks, but the data are nonspecific and predictions sometimes misleading. However, public health authorities could use these online sources, in combination with de-identified personal health data, to provide more accurate and earlier warning of infectious disease events-including exotic or emerging infections-even before the cause is confirmed, and allow more timely public health intervention. Achieving optimal benefits would require access to selected data from personal electronic health and laboratory (including pathogen genomic) records and the potential to (confidentially) re-identify individuals found to be involved in outbreaks, to ensure appropriate care and infection control. Despite existing widespread digital surveillance and major potential community benefits of extending its use to communicable disease control, there is considerable public disquiet about allowing public health authorities access to personal health data. Informed public discussion, greater transparency and an ethical framework will be essential to build public trust in the use of new technology for communicable disease control.

A common Salmonella Enteritidis sequence type from poultry and human gastroenteritis in Ibagué, Colombia

Salmonella Enteritidis es una de las mayores causas de salmonelosis en el mundo, siendo los huevos contaminados y la carne de pollo cruda sus principales fuentes de infección. En Ibagué, Colombia, se identificaron los principales serovares circulando en granjas, superficies de huevos y canales de pollo, sin embargo, se desconoce si esos serovares son responsables de gastroenteritis. Objetivo. Evaluar la relación genética entre aislamientos de Salmonella Enteritidis de aves de corral y humanos con gastroenteritis mediante multilocus sequence typing (MLST). Materiales y métodos. Se aisló Salmonella spp., de casos clínicos de gastroenteritis (n=110). Se realizó test de sensibilidad antibiótica, seguido de serotipificación y tipificación por medio de MLST y se comparó S. Enteritidis de humanos frente a S. Enteritidis de granjas ponedoras y de huevo comercializado (n=6). Resultados. Se aislaron 10 cepas de Salmonella spp., a partir de heces de humanos con gastroenteritis. Se obtuvo una prevalencia de Salmonella spp. de 9.09%, siendo S. Enteritidis (n=4), S. Typhymurium (n=2), S. Newport (n=1), S. Grupensis (n=1), S. Uganda (n=1) y S. Braenderup (n=1) los serotipos presentes en pacientes con gastroenteritis. El MLST indico que un tipo de secuencia común (ST11) de S. Enteritidis estuvo presente en todas las tres fuentes y mostraron el mismo patrón de resistencia antibiótica. Conclusión. S. Enteritidis ST11 constituye un vínculo entre el consumo/manipulación de huevos contaminados y gastroenteritis humana en Ibagué. Son necesarios estudios complementarios para conocer si otros serovares de Salmonella aislados de carne de pollo cruda también se asocian con la gastroenteritis humana.

Phenotypic and Genotypic Eligible Methods for Salmonella Typhimurium Source Tracking

Salmonellosis is one of the most common causes of foodborne infection and a leading cause of human gastroenteritis. Throughout the last decade, Salmonella enterica serotype Typhimurium (ST) has shown an increase report with the simultaneous emergence of multidrug-resistant isolates, as phage type DT104. Therefore, to successfully control this microorganism, it is important to attribute salmonellosis to the exact source. Studies of Salmonella source attribution have been performed to determine the main food/food-production animals involved, toward which, control efforts should be correctly directed. Hence, the election of a ST subtyping method depends on the particular problem that efforts must be directed, the resources and the data available. Generally, before choosing a molecular subtyping, phenotyping approaches such as serotyping, phage typing, and antimicrobial resistance profiling are implemented as a screening of an investigation, and the results are computed using frequency-matching models (i.e., Dutch, Hald and Asymmetric Island models). Actually, due to the advancement of molecular tools as PFGE, MLVA, MLST, CRISPR, and WGS more precise results have been obtained, but even with these technologies, there are still gaps to be elucidated. To address this issue, an important question needs to be answered: what are the currently suitable subtyping methods to source attribute ST. This review presents the most frequently applied subtyping methods used to characterize ST, analyses the major available microbial subtyping attribution models and ponders the use of conventional phenotyping methods, as well as, the most applied genotypic tools in the context of their potential applicability to investigates ST source tracking.

Characterization of Salmonella enterica isolates causing bacteremia in Lima, Peru, using multiple typing methods

In this study, different molecular typing tools were applied to characterize 95 Salmonella enterica blood isolates collected between 2008 and 2013 from patients at nine public hospitals in Lima, Peru. Combined results of multiplex PCR serotyping, two- and seven-loci multilocus sequence typing (MLST) schemes, serotyping, IS200 amplification and RAPD fingerprints, showed that these infections were caused by eight different serovars: Enteritidis, Typhimurium, Typhi, Choleraesuis, Dublin, Paratyphi A, Paratyphi B and Infantis. Among these, Enteritidis, Typhimurium and Typhi were the most prevalent, representing 45, 36 and 11% of the isolates, respectively. Most isolates (74%) were not resistant to ten primarily used antimicrobial drugs; however, 37% of the strains showed intermediate susceptibility to ciprofloxacin (ISC). Antimicrobial resistance integrons were carried by one Dublin (dfra1 and aadA1) and two Infantis (aadA1) isolates. The two Infantis isolates were multidrug resistant and harbored a large megaplasmid. Amplification of spvC and spvRA regions showed that all Enteritidis (n = 42), Typhimurium (n = 34), Choleraesuis (n = 3) and Dublin (n = 1) isolates carried the Salmonella virulence plasmid (pSV). We conclude that the classic serotyping method can be substituted by the multiplex PCR and, when necessary, sequencing of only one or two loci of the MLST scheme is a valuable tool to confirm the results. The effectiveness and feasibility of different typing tools is discussed.

Antimicrobial resistance, virulence genes and genetic relatedness of Salmonella enterica serotype Enteritidis isolates recovered from human gastroenteritis in Tehran, Iran

OBJECTIVES

Salmonella enterica serotype Enteritidis is a major serotype associated with human salmonellosis. The main objective of this study was to determine the antibiotic susceptibility patterns and the presence of virulence-associated genes among S. Enteritidis strains isolated from patients with gastroenteritis in Tehran, Iran.

METHODS

Over a period of 14 months (May 2015 to July 2016), 44 S. Enteritidis isolates recovered from clinical sources were characterised for antimicrobial susceptibility and virulence genes. Possible genetic relatedness among the strains was also assessed using pulsed-field gel electrophoresis (PFGE).

RESULTS

Salmonella Enteritidis isolates showed high rates of resistance to ciprofloxacin (90.9%) and nalidixic acid (77.3%). Of the 44 S. Enteritidis isolates, 30 (68.2%) were resistant to three or more antibiotics. Twenty-two different antimicrobial resistance patterns were detected among the isolates. The most frequent resistance type was antibiotype 14 (resistance to ciprofloxacin, cefuroxime and nalidixic acid), occurring in 8 (18.2%) of the isolates. Notably, all of the isolates carried invA, sefA, sipA and sopE2 virulence genes. Furthermore, 17 virulence profiles were observed among the strains. The most common virulence profile was VP1 (n=17; 38.6%), harbouring all of the virulence genes. Two distinct PFGE patterns were observed among 44S. Enteritidis isolates. There was no association between virulence profiles or antibiotypes and PFGE clusters.

CONCLUSIONS

Overall, this study provides valuable information on the virulence gene content, antibiotic resistance and genetic diversity of S. Enteritidis isolated from human sources in Iran.

Molecular characterization of Salmonella Typhimurium isolated in Brazil by CRISPR-MVLST

CRISPR-multi-locus virulence sequence typing (CRISPR-MVLST) was performed to type 92 S. Typhimurium strains isolated from humans and food sources between 1983 and 2013 in Brazil and assess the suitability of this methodology comparing it with PFGE already used for subtyping the same strains. Among the 92 S. Typhimurium strains studied, we identified 25 CRISPR1 alleles, 27 CRISPR2 alleles, 2 fimH alleles and 3 sseL alleles showing that the genetic variability is much higher in the CRISPRs loci than in the virulence genes. The CRISPR-MVLST analysis provided similar results to the PFGE previously published used to type the same set of strains, demonstrating that CRISPR-MVLST is a very efficient approach for subtyping S. Typhimurium serovar and can be used to complement and validate results obtained by the PFGE methodology.

Molecular Characterization of Salmonella enterica Serovar Aberdeen Negative for H2S Production in China

Salmonella enterica infections continue to be a significant burden on public health worldwide. The ability of S. enterica to produce hydrogen sulfide (H2S) is an important phenotypic characteristic used to screen and identify Salmonella with selective medium; however, H2S-negative Salmonella have recently emerged. In this study, the H2S phenotype of Salmonella isolates was confirmed, and the selected isolates were subjected to antimicrobial susceptibility testing and molecular identification by multilocus sequence typing, pulsed-field gel electrophoresis, and clustered regularly interspaced short palindromic repeat (CRISPR) analysis. The phs genetic operon was also analyzed. A total of 160 S. enterica serovar Aberdeen isolates were detected between 2005 and 2013 in China. Of them, seven non-H2S-producing isolates were detected. Notably, four samples yielded four pairs of isolates with different H2S phenotypes, simultaneously. The data demonstrated that H2S-negative isolates were genetically closely related to H2S-positive isolates. Three new spacers (Abe1, Abe2, and Abe3) were identified in CRISPR locus 1 in four pairs of isolates with different H2S phenotypes from the same samples. Sequence analysis revealed a new nonsense mutation at position 208 in the phsA gene of all non-H2S-producing isolates. Additionally, we describe a new screening procedure to avoid H2S-negative Salmonella, which would normally be overlooked during laboratory and hospital screening. The prevalence of this pathogen may be underestimated; therefore, it is important to focus on improving surveillance of this organism to control its spread.

Molecular characterization of microbial contaminants isolated from Umbilical Cord Blood Units for transplant

Disposal of Umbilical Cord Blood Units due to microbial contamination is a major problem in Cord Blood Banks worldwide as it reduces the number of units available for transplantation. Additionally, economic losses are generated as result of resources and infrastructure used to obtain such units. Umbilical Cord Blood Units that showed initial microbial contamination were subject to strains isolation, identification, and characterization by sequencing the 16S rRNA gene and Enterobacterial Repetitive Intergenic Consensus (ERIC-PCR). Moreover, tests of antimicrobial resistance/sensitivity and phenotypic activities that may play an important role in microbial infection were performed. Microbial contamination was detected in 120 Umbilical Cord Blood Units (2.31%) in the period from 2003 to 2013. The most frequently isolated strains were Enterococcus faecium, followed by Staphylococcus epidermidis, Escherichia coli, Enterococcus faecalis, Staphylococcus haemoliticus, Klebsiella pneumoniae, Enterococcus durans, Lactobacillus helveticus, Enterococcus hiriae and Roseomonas genomospecies 5. The ERIC-PCR assays revealed a wide genetic diversity in some strains although belonging to the same genus and specie, indicating different sources of contamination. Broad-spectrum penicillins, third generation cephalosporins, aminoglycosides, and fluoroquinolones showed lower inhibitory activity on the tested strains. All strains were proteolytic, 67.69% were amylase-positive, 27.6% hemolysis-positive, and 34.71% nuclease-positive. The most common sources of contamination were: vaginal flora, digestive tract, and skin flora, highlighting the need for staff training in good manufacturing practices in collection SCU since all contaminants identified are part of the microbial flora of the donors. Implications and consequences in the therapeutic use of Umbilical Cord Blood Units for transplantation contaminated by multiresistant bacteria in immunocompromised patients are discussed.