[Shigellosis attended in the emergency department of a regional hospital in southeastern Spain: from their presence to multiresistance]. / Shigelosis atendidas en el servicio de urgencias de un hospital regional del sudeste de España: Desde su presencia a la multirresistencia.

OBJECTIVE: In the bacterial etiology of severe acute infectious diarrhea, except that caused by Clostridioides difficile, most of them have an invasive character and antibiotic treatment will be necessary in specific situations. Shigella is a classic pathogen, in which it is crucial to know the sensitivity to different classic and alternative antimicrobials. The objective of this work was to analyze the presence of shigellosis and the rate of antibiotic resistance. METHODS: A descriptive-retrospective study of the reports of shigellosis of stool cultures issued between January 2016 and April 2022 was conducted. RESULTS: A total of 34 episodes (16 -47.1%- by Shigella sonnei) were observed, as of 2018. There were only 2 pediatric cases. The overall resistance rate to azithromycin, trimethoprim-sulfamethoxazole and ciprofloxacin was 52.9%, 64.7% and 44.1%, respectively. 26.5% were resistant to the 3 groups of antibiotics. There was a higher rate of resistance for S. sonnei. The emergence of resistance to cephalosporins in recent years stands out. Episodes of multidrug-resistant shigellosis were detected between 2020 (1 by S. flexneri) and 2022 (4 by S. sonnei). CONCLUSIONS: The episodes of shigellosis are emerging in our environment with a higher rate of multi-resistance. In this context, current empirical treatments for acute enteroinvasive enteritis are at risk of failure, if necessary.

Isolation of Campylobacter spp. from Three Species of Antarctic Penguins in Different Geographic Locations.

The presence of Campylobacter species was studied in three Antarctic penguin species, Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis antarctica) and gentoo (Pygoscelis papua). A total of 390 penguins were captured in 12 different rookeries along the Antarctic Peninsula with differences in the amount of human visitation: six colonies were highly visited [Stranger Point, King George Island (P. papua and P. adeliae); Hannah Point, Livingston Island (P. papua and P. antarctica); Deception Island (P. antarctica); and Paradise Bay, Antarctic Peninsula (P. papua)], and six colonies were rarely visited [Devil's Point, Byers Peninsula, Livingston Island (P. papua); Cierva Cove, Antarctic Peninsula (P. papua); Rongé Island (P. papua and P. antarctica); Yalour Island (P. adeliae); and Avian Island (P. adeliae)]. A total of 23 strains were isolated from penguins from nine different rookeries. Campylobacter lari subsp. lari was isolated from eight samples (seven from P. papua and one from P. adeliae); C. lari subsp. concheus from 13 (ten from P. adeliae and three from P. antarctica) and C. volucris from two samples (both from P. papua). We did not find any significant differences in the prevalence of Campylobacter spp. between the populations in highly and rarely visited areas. This is the first report of C. lari subsp. concheus and C. volucris isolation from penguins in the Antarctic region.

Prospective use of whole genome sequencing (WGS) detected a multi-country outbreak of Salmonella Enteritidis.

Since April 2015, whole genome sequencing (WGS) has been the routine test for Salmonella identification, surveillance and outbreak investigation at the national reference laboratory in England and Wales. In May 2015, an outbreak of Salmonella Enteritidis cases was detected using WGS data and investigated. UK cases were interviewed to obtain a food history and links between suppliers were mapped to produce a food chain network for chicken eggs. The association between the food chain network and the phylogeny was explored using a network comparison approach. Food and environmental samples were taken from premises linked to cases and tested for Salmonella. Within the outbreak single nucleotide polymorphism defined cluster, 136 cases were identified in the UK and 18 in Spain. One isolate from a food containing chicken eggs was within the outbreak cluster. There was a significant association between the chicken egg food chain of UK cases and phylogeny of outbreak isolates. This is the first published Salmonella outbreak to be prospectively detected using WGS. This outbreak in the UK was linked with contemporaneous cases in Spain by WGS. We conclude that UK and Spanish cases were exposed to a common source of Salmonella-contaminated chicken eggs.

Characterization of an emergent clone of enteroinvasive Escherichia coli circulating in Europe.

Enteroinvasive Escherichia coli (EIEC) cause intestinal illness indistinguishable from that caused by Shigella, mainly in developing countries. Recently an upsurge of cases of EIEC infections has been observed in Europe, with two large outbreaks occurring in Italy and in the United Kingdom. We have characterized phenotypically and genotypically the strains responsible for these epidemics together with an additional isolate from a sporadic case isolated in Spain. The three isolates belonged to the same rare serotype O96:H19 and were of sequence type ST-99, never reported before in EIEC or Shigella. The EIEC strains investigated possessed all the virulence genes harboured on the large plasmid conferring the invasive phenotype to EIEC and Shigella while showing only some of the known chromosomal virulence genes and none of the described pathoadaptative mutations. At the same time, they displayed motility abilities and biochemical requirements resembling more closely those of the non-pathogenic E. coli rather than the EIEC and Shigella strains used as reference. Our observations suggested that the O96:H19 strains belong to an emerging EIEC clone, which could be the result of a recent event of acquisition of the invasion plasmid by commensal E. coli.

Virulence genes, antibiotic resistance and integrons in Escherichia coli strains isolated from synanthropic birds from Spain.

The aim of this study was to determine the presence of virulence genes and antibiotic resistance profiles in 164 Escherichia coli strains isolated from birds (feral pigeons, hybrid ducks, house sparrows and spotless starlings) inhabiting urban and rural environments. A total of eight atypical enteropathogenic E. coli strains were identified: one in a house sparrow, four in feral pigeons and three in spotless starlings. Antibiotic resistance was present in 32.9% (54) of E. coli strains. The dominant type of resistance was to tetracycline (21.3%), ampicillin (19.5%) and sulfamethoxazole (18.9%). Five isolates had class 1 integrons containing gene cassettes encoding for dihydrofolate reductase A (dfrA) and aminoglycoside adenyltransferase A (aadA), one in a feral pigeon and four in spotless starlings. To our knowledge, the present study constitutes the first detection of virulence genes from E. coli in spotless starlings and house sparrows, and is also the first identification worldwide of integrons containing antibiotic resistance gene cassettes in E. coli strains from spotless starlings and pigeons.

Molecular mechanisms of quinolone, macrolide, and tetracycline resistance among Campylobacter isolates from initial stages of broiler production.

The aim of this study was to investigate the resistance mechanisms of quinolones, macrolides and tetracycline in campylobacter isolates from grandparent and parent broiler breeders in Spain. Twenty-six isolates were investigated for quinolone resistance, three isolates for macrolide resistance and 39 for tetracycline resistance. All of the quinolone-resistant isolates possessed the mutation Thr86Ile in the quinolone resistance-determining region of gyrA and one isolate possessed the mutation Pro104Ser. Only one Campylobacter coli population (defined by restriction fragment length polymorphism-polymerase chain reaction of flaA and pulsed field gel electrophoresis) was resistant to erythromycin, and the mutation A2075G (23S rDNA) was responsible for macrolide resistance. The tetO gene was found in all of the tetracycline-resistant isolates. Twenty-two out of the 39 isolates investigated by Southern blot possessed chromosomic location of tetO and 17 were located on plasmids. Most of the plasmids with tetO were of around 60 kb and conjugation was demonstrated in a selection of them. In conclusion, we showed that Thr86Ile is highly prevalent in quinolone-resistant isolates as well as mutation A2075G in macrolide-resistant isolates of poultry origin. More variability was found for tetO. The possibility of horizontal transmission of tetO among campylobacter isolates is also an issue of concern in public health.

Use of virulence determinants and seropathotypes to distinguish high- and low-risk Escherichia coli O157 and non-O157 isolates from Europe.

The presence of 10 virulence genes was examined using polymerase chain reaction (PCR) in 365 European O157 and non-O157 Escherichia coli isolates associated with verotoxin production. Strain-specific PCR data were analysed using hierarchical clustering. The resulting dendrogram clearly separated O157 from non-O157 strains. The former clustered typical high-risk seropathotype (SPT) A strains from all regions, including Sweden and Spain, which were homogenous by Cramer's V statistic, and strains with less typical O157 features mostly from Hungary. The non-O157 strains divided into a high-risk SPTB harbouring O26, O111 and O103 strains, a group pathogenic to pigs, and a group with few virulence genes other than for verotoxin. The data demonstrate SPT designation and selected PCR separated verotoxigenic E. coli of high and low risk to humans; although more virulence genes or pulsed-field gel electrophoresis will need to be included to separate high-risk strains further for epidemiological tracing.

Cluster investigation of mixed O76:H19 Shiga toxin-producing Escherichia coli and atypical enteropathogenic E. coli infection in a Spanish household.

A Spanish household was identified through a Public Health follow up on a Shiga toxin-producing Escherichia coli (STEC)-positive 14-month-old girl reporting bloody diarrhoea, with the four household members experiencing either symptomatic or asymptomatic STEC and/or atypical enteropathogenic E. coli (aEPEC) shedding. In total, two different O76:H19 STEC strains and six aEPEC strains belonging to multiple serotypes were isolated and characterized in the household during a 5-month period. Prolonged asymptomatic shedding of O76:H19 STEC and O51:H49 aEPEC was detected in two family members. Although there was no conclusive evidence, consumption of vegetables fertilized with sheep manure was the suspected source of infection. This study highlights the risk of cross-infections posed by prolonged asymptomatic carriage and close household contact between family members, and illustrates the importance of molecular epidemiology in understanding disease clusters.

Prevalence of Shiga toxin-producing Escherichia coli, Salmonella spp. and Campylobacter spp. in large game animals intended for consumption: relationship with management practices and livestock influence.

Although wild ruminants have been identified as reservoirs of Shiga-toxin producing Escherichia coli (STEC), little information is available concerning the role of Salmonella spp. and Campylobacter spp. in large game species. We evaluated the presence of these pathogens in faeces (N=574) and carcasses (N=585) sampled from red deer (N=295), wild boar (N=333) and other ungulates (fallow deer, mouflon) (N=9). Animal sampling was done in situ from 33 hunting estates during two hunting seasons. Salmonella spp. and Campylobacter spp. strains associated with human campylobacteriosis were infrequently detected indicating that both pathogens had a limited zoonotic risk in our study area. The overall STEC prevalence in animals was 21% (134/637), being significantly higher in faeces from red deer (90 out of 264). A total of 58 isolates were serotyped. Serotypes O146:H- and O27:H30 were the most frequent in red deer and the majority of isolates from red deer and wild boar were from serotypes previously found in STEC strains associated with human infection, including the serotype O157:H7. The STEC prevalence in red deer faeces was significantly higher with the presence of livestock (p<0, 01) where high densities of red deer (p<0.001) were present. To the best of our knowledge, this is the first study reporting the occurrence of Salmonella spp. and STEC in carcasses of large game animals. Furthermore, this study confirmed by pulsed-field gel electrophoresis (PFGE) that cross contamination of STEC during carcass dressing occurred, implying the likelihood of these pathogens entering into the food chain.

Epidemiology of subclinical salmonellosis in wild birds from an area of high prevalence of pig salmonellosis: phenotypic and genetic profiles of Salmonella isolates.

The epidemiology of subclinical salmonellosis in wild birds in a region of high Salmonella prevalence in pigs was studied. Three hundred and seventy-nine faecal samples from 921 birds trapped in 31 locations nearby pig premises, and 431 samples from 581 birds of 10 natural settings far from pig farms were analysed for the presence of Salmonella spp. Positive samples were serotyped and analysed for antimicrobial resistance (AR). Phage typing and pulsed-field gel electrophoresis (PFGE) on Salmonella Typhimurium isolates were also carried out. The overall proportion of Salmonella-positive samples was 1.85% (95% CI=0.93, 2.77). Salmonella isolation was positively associated with samples collected from birds in the proximity of a pig operation (OR=16.5; 95% CI=5.17, 52.65), and from non-migratory (or short-distance migration) birds (OR=7.6; 95% CI=1.20, 48.04) and negatively related to mostly granivorous birds (OR=0.4; 95% CI=0.15, 1.13). Salmonella Typhimurium was the most prevalent serotype and four different XbaI PFGE patterns were observed that matched the four phage types identified (U310, U311, DT164 and DT56). Only 20% of the strains showed multi-AR. In three farms, a high degree of homogeneity among isolates from different birds was observed. These findings suggested that pig farms may act as amplifiers of this infection among wild birds, and the degree of bird density may have much to do on this transmission. Some of the Salmonella serotypes isolated from bird faeces were of potential zoonotic transmission and associated with AR. Monitoring salmonellosis in wild bird is advised.

Detection and characterization of Shiga toxin-producing Escherichia coli in game meat and ready-to-eat meat products.

A total of 142 samples of game meat and ready-to-eat meat products from red deer and wild boar were analysed in order to assess the presence of Shiga toxin-producing Escherichia coli (STEC). Shiga-toxin encoding genes (stx genes) were detected by PCR in 36 (25.4%) of the samples and STEC was isolated from 8 (5.6%) of the same samples. None of the samples tested positive for E. coli O157:H7. Four different serotypes were found among the 8 STEC isolates, with serotype O27:H30 being predominant (62.5%, 5/8). The PCR assay indicated the presence of the stx2 gene in all of the STEC isolates and further subtyping resulted in detection of three different subtypes: stx2a, stx2b and stx2g. The only stx1-positive isolate was further subtyped as stx1c. The ehxA gene was detected in 3 (37.5%) of the isolates and none of them contained the eae gene. All STEC isolates were sensitive to the 13 antibiotics tested. Some isolates possessed serotypes and virulence gene profiles previously associated with STEC infections in humans. The isolation of a STEC strain carrying the stx2a subtype from a ready-to-eat meat product from deer suggests the role of these products as a potential source of STEC infections in humans.

Salmonella Paratyphi B var Java infections associated with exposure to turtles in Bizkaia, Spain, September 2010 to October 2011.

Between September 2010 and October 2011, the Unit of Epidemiology in the Department of Public Health in Bizkaia, Spain identified eight cases of Salmonella Paratyphi B var Java infection and three cases of infection with its possible monophasic variant 4,5,12:b:- dT+. Six cases reported contact with turtles and S. Java was isolated from three of these turtles' habitats. The isolates from the patients and their respective turtles were indistinguishable by pulsed-field gel electrophoresis (PFGE). Although other reptiles can also carry Salmonella, turtles pose a special risk, as they are commonly kept as pets for children. This emphasizes the need to give recommendations regarding ownership and handling of aquatic turtles and other reptiles. As parents are often not aware of the risk of infection associated with the presence of turtles in the household, it would be appropriate to inform potential buyers at points of sale about the risk of infection and measures they can take to minimise this risk.

Nationwide outbreak of Salmonella serotype Kedougou associated with infant formula, Spain, 2008.

On 5 August 2008, the National Centre of Microbiology in Madrid, Spain, notified an increase in Salmonella Kedougou isolations compared to 2007, with 21 cases including 19 children under one year of age. Active case finding and a matched case-control study were carried out to confirm this increase, identify source, transmission mode and risk factors in order to implement control measures. Cases were defined as any child under one year of age with S. Kedougou isolated since 1 January 2008, and were matched for age, sex, medical practitioner and diagnosis week with controls who were selected among patients of the cases' medical practitioners. An ad hoc questionnaire was completed for cases and controls and a univariate analysis was conducted to identify risk factors. We found 42 isolates from 11 of the 19 Spanish Regions. Completed questionnaires were available for 39 of 42 patients identified; 31 were children under one year of age and fulfilled the case definition. The median age of the 31 cases was 4.3 months and 13 were male. Main symptoms were diarrhoea (n=31) and fever (n=13). Ten cases required hospitalisation. All 31 cases had consumed infant formula milk of Brand A which was associated with illness in the univariate analysis (exact matched odds ratio: 74.92; 95% confidence interval: 12.89-infinity). All patient isolates showed indistinguishable pulsed-field gel electrophoresis and antimicrobial susceptibility patterns. Five milk samples from three cases' households were negative for Salmonella. Our results suggest that Brand A was the transmission vehicle of S. Kedougou in the outbreak that occurred in Spain between January and August 2008. Food safety authorities recalled five batches of Brand A milk on 26 August 2008. No further cases have been detected as of 15 September 2009.

Spread of a multiresistant CTX-M-9-producing Salmonella enterica serotype Virchow phage type 19 in Spain.

The purpose of this study was to survey Salmonella enterica serotype Virchow phage type 19 (S. Virchow PT19) strains submitted to the Spanish National Reference Laboratory for Salmonella (SNRLS) from 2002 to 2006 in order to determine the rate type and genetic background of beta-lactam resistance and to further identify the associated resistances. Ninety-nine S. Virchow PT19 strains were analysed. Antimicrobial susceptibility was determined by the disk diffusion method using Mueller-Hinton agar medium. Polymerase chain reaction (PCR) assays and, later, sequencing of the obtained fragments were performed for the molecular characterisation of the resistances. Pulsed-field gel electrophoresis (PFGE) and plasmid analysis (using conjugation, Southern blot hybridisation and replicon typing) were used for characterisation. The characterisation of S. Virchow PT19 strains allowed the identification of a clonal multiresistant S. Virchow PT19 harbouring an IncH12 plasmid with the bla (CTX-M-9) gene within the complex integron In60 distributed across Spain. An IncH12 plasmid widely reported and studied in Enterobacteria is described in a clonal multiresistant S. Virchow PT19 which has successfully spread throughout Spain.

Pheno-genotypic characterisation of Escherichia coli O157:H7 isolates from domestic and wild ruminants.

Shiga toxin-producing Escherichia coli (STEC) O157:H7 represents a major public health concern worldwide, with ruminants recognised as their main natural reservoir. The aim of this work was to determine the phenotypic features and genetic relationships of 46 E. coli O157:H7 isolates obtained from sheep, cattle and deer faeces and from unpasteurised goat milk in Spain over a period of 11 years. Characterisation was performed by polymerase chain reaction (PCR), phage typing and pulsed-field gel electrophoresis (PFGE). An atypical E. coli O157:H7 strain (sorbitol-fermenting and beta-glucuronidase positive) originating from deer faeces was detected. Genes encoding Shiga toxins were detected in 69.6% of isolates, all of them carrying only the stx(2) gene. The isolates were from nine different phage types, although 67.4% were restricted to only three: PT14, PT34 and PT54. PT54 was the most prevalent phage type and contained isolates from cattle, sheep and deer. Majority of the isolates were from phage types previously found in strains associated with human infection. XbaI-PFGE identified 33 different types and 11 groups of closely related types (more than 85% similarity), one of which included 21 (45.7%) isolates originating from different animal species, including deer. These results indicate common origin or inter-species spread of genetically similar E. coli O157:H7 isolates and contribute to earlier investigations identifying deer as a natural source of E. coli O157:H7. The study also highlights the emergence of phenotypic variants of E. coli O157:H7, which may not be identified by routine culture methods or by biochemical tests used to characterise serotype O157:H7.

Detection and characterisation of O157:H7 and non-O157 Shiga toxin-producing Escherichia coli in wild boars.

The aim of this work was to determine the prevalence and characteristics of Escherichia coli O157:H7 and non-O157 Shiga toxin-producing E. coli (STEC) in free-ranging wild boars killed during the hunting season in southwest Spain. Faecal samples from 212 wild boars (Sus scrofa) were collected and examined for STEC. Characterisation of isolates was performed by PCR, serotyping, phage typing, and pulsed-field gel electrophoresis (PFGE). E. coli O157:H7 and non-O157 STEC were isolated from 7 (3.3%) and 11 (5.2%) animals, respectively, and the resulting 19 isolates were characterised. The PCR procedure indicated that 4 isolates carried the stx(1) gene, 12 carried the stx(2) gene, and 1 contained both of these genes. The ehxA, eae, and saa genes were detected in 13, 8, and 1 of the isolates, respectively. The eae-positive isolates comprised the types eae-gamma 1 and eae-zeta. The isolates belonged to 11 O:H serotypes, including 4 new serotypes not previously reported within STEC strains, and the majority of them were from serotypes previously associated with human infection. E. coli O157:H7 isolates belonged to phage types associated with severe human illness: PT14, PT34, and PT54. Indistinguishable PFGE types were found in E. coli O157:H7 isolates recovered from a wild boar and from a human patient with diarrhoea living in the same geographic area.

Characterization of a monoclonal antibody directed against Salmonella enterica serovar Typhimurium and serovar [4,5,12:i:-].

Flagellar extracts of Salmonella enterica serovars expressing phase 2 H1 antigenic complex (H:1,2, H:1,5, H:1,6, and H:1,7) and a mutant flagellin obtained by site-directed mutagenesis of the fljB gene from serovar Typhimurium at codon 218, transforming threonine to alanine, expressed in Escherichia coli (fljB218(A)) were used to analyze the H1 antigenic complex. Cross-reactions were detected by Western blotting and dot blotting using commercial polyclonal antibodies against the different wild-type extracts and mutant FljB218(A). Therefore, we produced a monoclonal antibody (MAb), 23D4, isotyped as immunoglobulin M, against H:1,2 S. enterica serovar Typhimurium flagellin. The mutant flagellin was not recognized by this MAb. When a large number of phase 1 and phase 2 flagellin antigens of different serovars were used to characterize the 23D4 MAb, only extracts of serovars Typhimurium and [4,5,12:i:-] reacted. The protein composition of phase 1 and phase 2 extracts and highly purified H:1,2 flagellin from serovar Typhimurium strain LT2 and extract of strain 286 (serovar [4,5,12:i:-]), which reacted with the MAb, was studied. Phase 2 flagellin (FljB(H:1,2)) was detected in phase 1 and phase 2 flagellar heat extracts of serovar Typhimurium and was the single protein identified in all spots of purified H:1,2 flagellin. FliC, FlgK, and other proteins were detected in some immunoreactive spots and in the flagellar extract of serovar [4,5,12:i:-]. Immunoelectron microscopy of complete bacteria with 23D4 showed MAb attachment at the base of flagella, although the MAb failed to recognize the filament of flagella. Nevertheless, the results obtained by the other immunological tests (enzyme-linked immunosorbent assay, Western blotting, and dot blotting) indicate a reaction against flagellins. The epitopes could also be shared by other proteins on spots where FljB is not present, such as aminopeptidase B, isocitrate lyase, InvE, EF-TuA, enolase, DnaK, and others. In conclusion, MAb 23D4 can be useful for detection and diagnostic purposes of S. enterica serovar Typhimurium and serovar [4,5,12:i:-] and could be also helpful for epitope characterization of flagellum-associated antigens.

Salmonella Indiana as a cause of abortion in ewes: Genetic diversity and resistance patterns.

Salmonella enterica subspecies enterica Indiana, a food-borne serovar uncommon in most countries, was responsible for an outbreak of abortion in a flock of Lacaune dairy ewes in southern Spain. Drinking water and feedstuff samples were analysed in an attempt to determine the source of the infection. Pigeons (Columba livia) and turtledoves (Streptopelia turtur) in close contact with the ewes were captured and examined for the bacterium. Seventeen S. Indiana strains were isolated from the ewes and wild birds and the genetic similarity among them analysed by Pulsed Field Gel Electrophoresis (PFGE) after the digestion of their genomic DNA with the restriction enzyme XbaI. The results suggest the wild birds might be responsible for the outbreak in the ewes. The strains recovered were fully susceptible to 15 out of the 16 antimicrobial agents tested: ampicillin, amoxycillin clavulanate, cephalothin, ceftriaxone, gentamicin, neomycin, streptomycin, tetracycline, ciprofloxacin, enrofloxacin, sulphonamides, trimethoprim-sulphamethoxazole, apramycin, colistin and chloramphenicol. Differences in the resistance pattern to nalidixic acid were observed; 11 strains (64.7%) were nalidixic acid resistant (R-Nx) and 6 (35.3%) sensitive (S-Nx). Among the R-Nx strains, a substitution of Gly to Cys at position 81 (Gly81àCys) of the gyrA gene in 10 strains isolated from wild birds and ovine foetuses, and of Asp to Tyr at position 87 (Asp87àTyr) in one strain isolated from ewe faeces, were revealed by sequencing the gene. To control the outbreak, enrofloxacin treatment was administered for 5 days. The same therapy was used to prevent infection during following gestation cycles, administering the antimicrobial agent at presentation and over 4 weeks before birth. Anti-bird meshes and closed drinking and feeding troughs were also installed to prevent further contact of the ewes with wild birds.

Molecular phylogeny of the salmonellae: relationships among Salmonella species and subspecies determined from four housekeeping genes and evidence of lateral gene transfer events.

The salmonellae are a diverse group of bacteria within the family Enterobacteriaceae that includes two species, Salmonella enterica and Salmonella bongori. In order to characterize the phylogenetic relationships of the species and subspecies of Salmonella, we analyzed four housekeeping genes, gapA, phoP, mdh and recA, comprising 3,459 bp of nucleotide sequence data for each isolate sequenced. Sixty-one isolates representing the most common serotypes of the seven subspecies of Salmonella enterica and six isolates of Salmonella bongori were included in this study. We present a robust phylogeny of the Salmonella species and subspecies that clearly defines the lineages comprising diphasic and monophasic subspecies. Evidence of intersubspecies lateral gene transfer of the housekeeping gene recA, which has not previously been reported, was obtained.

Antimicrobial resistance and phage and molecular typing of Salmonella strains isolated from food for human consumption in Spain.

The aims of this study were to ascertain the population structure and antimicrobial susceptibility of Salmonella enterica serovars isolated in 2002 from food in 16 Spanish regions. Serovars were characterized by serotyping, phage typing, antimicrobial susceptibility, and pulsed-field gel electrophoresis (PFGE) typing, and 264 nonrelated strains were selected for further analysis. The main sources were eggs and their derivatives (21.6% of strains), poultry and related products (16.6%), and seafood (16.3%). High serotype diversity was detected (51 serotypes); the most common were Enteritidis (n = 96, 36.3%) and Typhimurium (n = 53, 20.1%), followed by a miscellaneous group of 49 different serotypes (n = 115, 43.5%). A 15% increase in Salmonella Enteritidis isolation was observed. Common phage types for Salmonella Enteritidis were PT1 (41.6% of isolates), PT4 (9.4%), PT6 (9.4%), and PT6a (9.4%), and common types for Salmonella Typhimurium were DTU302 (18.8%), DT104 (15.1%), and DT104B (13.2%). Salmonella Enteritidis strains were categorized into eight PFGE types with a similarity of 81 to 96%, and 73.9% of the strains were grouped into just one cluster. Salmonella Typhimurium isolates were divided into 13 PFGE types with a similarity of 64 to 86%, and one predominant clone contained 41.5% of the strains. Resistance rates for Salmonella Enteritidis, Salmonella Typhimurium, and the miscellaneous group were, respectively, 8.3, 69.8, and 13.9% for ampicillin, 3.1, 52.8, and 59% for streptomycin, 40.6, 22.6, and 10.4% for nalidixic acid, 15.6, 71.7, and 31.1% for tetracycline, 7.3, 18.8, and 9.5% for trimethoprim-sulfamethoxazole, 0, 50.9, and 4.3% for chloramphenicol, and 6.2, 71.7, and 17.4% for multiple (at least four) antimicrobials. All the strains remained susceptible to other beta-lactams and fluoroquinolones. Surveillance of S. enterica isolated from food is strongly recommended to reduce community exposure to antimicrobial resistant strains.