Aquariums as reservoirs for multidrug-resistant Salmonella Paratyphi B

Retrospective study on the occurrence of Salmonella serotypes in veterinary specimens of Atlantic Canada (2012-2021)

AIM

This study aimed to summarize the frequency and the antimicrobial susceptibility profiles of the Salmonella serotypes identified from the specimens of companion animals, livestock, avian, wildlife and exotic species within Atlantic Canada.

MATERIALS AND METHODS

The retrospective electronic laboratory data of microbiological analyses of a selected subset of samples from 03 January 2012 to 29 December 2021 submitted from various animal species were retrieved. The frequency of Salmonella serotypes identified, and their antimicrobial susceptibility results obtained using the disk diffusion or broth method were analysed. The test results were interpreted according to the Clinical and Laboratory Standards Institute standard. The Salmonella serotypes were identified by slide agglutination (Kauffman-White-Le-Minor Scheme) and/or the Whole Genome Sequencing for the Salmonella in silico Serovar Typing Resource-based identification.

RESULTS

Of the cases included in this study, 4.6% (n = 154) had at least one Salmonella isolate, corresponding to 55 different serovars. Salmonella isolation was highest from exotic animal species (n = 40, 1.20%), followed by porcine (n = 26, 0.78%), and canine (n = 23, 0.69%). Salmonella subsp. enterica serovar Typhimurium was predominant among exotic mammals, porcine and caprine samples, whereas S. Enteritidis was mostly identified in bovine and canine samples. S. Typhimurium of porcine origin was frequently resistant (>70.0%) to ampicillin. In contrast, S. Typhimurium isolates from porcine and caprine samples were susceptible (>70.0%) to florfenicol. S. Oranienburg from equine samples was susceptible to chloramphenicol, but frequently resistant (>90.0%) to azithromycin. In avian samples, S. Copenhagen was susceptible (>90.0%) to florfenicol, whereas Muenchen was frequently resistant (>90.0%) to florfenicol. S. subsp. diarizonae serovar IIIb:61:k:1,5 of ovine origin was resistant (50.0% isolates) to sulfadimethoxine. No significant changes were observed in the antibiotic resistance profiles across the study years.

CONCLUSIONS

This report provides data for surveillance studies, distribution of Salmonella serotypes and their antimicrobial resistance among veterinary specimens of Atlantic Canada.

Emergence of Rarely Reported Extensively Drug-Resistant Salmonella Enterica Serovar Paratyphi B among Patients in East China

BACKGROUND

In recent years, global concern over increasing multidrug resistance (MDR) among various Salmonella serotypes has grown significantly. However, reports on MDR Salmonella Paratyphi B remain scarce, let alone the extensively drug-resistant (XDR) strains.

METHODS

In this retrospective study, we investigated the isolates of Salmonella Paratyphi B in Jiangsu Province over the past decade and carried out antimicrobial susceptibility tests, then the strains were sequenced and bioinformatics analyses were performed.

RESULTS

27 Salmonella Paratyphi B strains were identified, of which the predominant STs were ST42 (11), ST86 (10), and ST2814 (5). Among these strains, we uncovered four concerning XDR Salmonella Paratyphi B ST2814 strains (4/5) which were previously unreported. These alarmingly resistant isolates showed resistance to all three major antibiotic classes for Salmonella treatment and even the last resort treatment tigecycline. Bioinformatics analysis revealed high similarity between the plasmids harbored by these XDR strains and diverse Salmonella serotypes and Escherichia coli from China and neighboring regions. Notably, these four plasmids carried the ramAp gene responsible for multiple antibiotic resistance by regulating the AcrAB-TolC pump, predominantly originating from China. Additionally, a distinct MDR ST42(1/11) strain with an ICE on chromosome was also identified. Furthermore, phylogenetic analysis of global ST42/ST2814 isolates highlighted the regional specificity of these strains, with Jiangsu isolates clustering together with domestic isolates and XDR ST2814 forming a distinct branch, suggesting adaptation to local antibiotic pressures.

CONCLUSIONS

This research underscores the pressing need for closely monitoring the MDR/XDR Salmonella Paratyphi B, particularly the emerging ST2814 strains in Jiangsu Province, to effectively curb its spread and protect public health. Moreover, surveillance should be strengthened across different ecological niches and genera to track resistance genes and horizontal gene transfer elements under the concept of "ONE HEALTH".

A Familiar Outbreak of Monophasic Salmonella serovar Typhimurium (ST34) Involving Three Dogs and Their Owner's Children

Salmonella is a Gram-negative enteric bacterium responsible for the foodborne and waterborne disease salmonellosis, which is the second most reported bacterial zoonosis in humans. Many animals are potential sources of salmonellosis, including dogs, cats, and other pets. We report the case of an outbreak of salmonellosis in a family in central Italy, affecting two children and involving their three dogs as carriers. One of the children needed medical care and hospitalisation. Isolation and analysis of stool samples from the sibling and the animals present in the house were carried out. Serotyping allowed the identification of S. enterica subsp. enterica serovar Typhimurium in its monophasic variant for all the isolates. The results of whole-genome sequencing confirmed that the strains were tightly related. The minimum inhibitory concentration (MIC) test documented the resistance to ampicillin, sulfamethoxazole, and tetracycline. The origin of the zoonotic outbreak could not be assessed; however, the case study showed a clear passage of the pathogen between the human and non-human members of the family. The possibility of a transmission from a dog to a human suggests the need for further studies on the potential ways of transmission of salmonellosis through standard and alternative feed.

Uses of Antibiotics in Ornamental Fish in Hong Kong and the Antibiotic Resistance in the Associated Zoonotic Pathogens

The use of antibiotics in ornamental fish is not regulated, as they are not intended for human consumption. Although antibiotic resistant bacteria have been detected in ornamental fish worldwide, there have been no studies to look at the situation in Hong Kong. Therefore, the present study was conducted to investigate the use of antibiotics in ornamental fish. Ornamental fish were purchased from five local pet fish shops and the antibiotics in carriage water were quantified using liquid chromatography tandem mass spectrometry. Moreover, Aeromonas and Pseudomonas spp. present in carriage water were isolated and their minimum inhibitory concentrations against selected antibiotics were determined. Results indicated that among the twenty antibiotics screened, doxycycline (0.0155-0.0836 µg L^-1), oxytetracycline (0.0102-29.0 µg L^-1), tetracycline (0.0350-0.244 µg L^-1), enrofloxacin (0.00107-0.247 µg L^-1), and oxalinic acid (n.d.-0.514 µg L^-1) were detected in all sampled shops. Additionally, MIC results revealed that some of the Aeromonas and Pseudomonas spp. isolates were highly resistant to all antibiotics selected. Our findings confirmed that multiple antibiotics are being used in ornamental fish and the associated bacteria are resistant to selected antibiotics, suggesting that this could be a significant transmission route of antibiotic resistant bacteria to household indoor environments.

Contamination Status of Salmonella spp., Shigella spp. and Campylobacter spp. in Surface and Groundwater of the Kelani River Basin, Sri Lanka

Waterborne diseases are a global problem that causes more than 2.2 million deaths annually. Therefore, the present study was focused on microbiological contamination of both ground and surface water by means of total coliform, Escherichia coli (E. coli), Salmonella spp., Shigella spp. and Campylobacter spp. Seventy two groundwater and 45 surface water sampling locations were selected to collect water from the head, transitional and meandering regions of the Kelani River Basin for a period of one year (both dry and wet seasons). The results of the study revealed that the entire Kelani River basin was contaminated with total coliform and E. coli bacteria and almost all the sampling locations exceed Sri Lanka Standards Institute (SLSI) guideline value given for drinking water (0 CFU/100 mL). Further, in groundwater, 17 locations were positive for Salmonella spp., whereas only 2 locations were positive for Campylobacter spp. In surface water, 26 and three sampling locations were positive for Salmonella spp. and Campylobacter spp., respectively. In this study, 23 different human pathogenic serovars were isolated and the Salmonella enterica serovar Kentucky was identified as the commonest type. Thus, the result of the study revealed that the consumption of raw water from the Kelani River Basin is unsafe and possible to cause gastrointestinal diseases.

Molecular detection of virulence genes in Salmonella spp. isolated from chicken faeces in Mafikeng, South Africa

Chickens have been implicated in most Salmonella disease outbreaks because they act as carriers of the pathogen in their gut. There are over 2500 serotypes of Salmonella that have been reported worldwide and 2000 of these serovars can be found in chickens. The main objective of this study was to determine the Salmonella serotypes found in poultry farms around Mafikeng district, South Africa. Salmonella was identified according to the guidelines of the International Organization for Standardization (ISO) (ISO 6579:2002) standard techniques. Faecal samples were collected and analysed for Salmonella using conventional cultural methods and polymerase chain reaction targeting the 16S Ribosomal Deoxyribonucleic acid (rDNA) gene for Salmonella identification. Out of 130 presumptive Salmonella isolates determined by urease and triple sugar iron tests, only 46 isolates were identified as Salmonella serotypes of which S. Typhimurium was the most frequent with 18 (39.1%), followed by S. Heidelberg with 9 (19.6%), S. bongori with 7 (15.2%), S. Enteritidis with 6 (13.0%) and both S. Paratyphi B and S. Newport with 3 (6.5%) each. Seven virulence genes including invA 100%, spy 39%, hilA 9%, misL 30%, sdfI 13%, orfL 11% and spiC 9% were detected from these Salmonella isolates in this study. The presence of these virulence genes indicates high pathogenicity potential of these isolates which is a serious public health concern because of zoonotic potential of Salmonella.

Antimicrobial Resistance in Salmonella enterica Serovar Paratyphi B Variant Java in Poultry from Europe and Latin America

Salmonella enterica serovar Paratyphi B variant Java sequence type 28 is prevalent in poultry and poultry meat. We investigated the evolutionary relatedness between sequence type 28 strains from Europe and Latin America using time-resolved phylogeny and principal component analysis. We sequenced isolates from Colombia, Guatemala, Costa Rica, and the Netherlands and complemented them with publicly available genomes from Europe, Africa, and the Middle East. Phylogenetic time trees and effective population sizes (N_e) showed separate clustering of strains from Latin America and Europe. The separation is estimated to have occurred during the 1980s. N_e of strains increased sharply in Europe around 1995 and in Latin America around 2005. Principal component analysis on noncore genes showed a clear distinction between strains from Europe and Latin America, whereas the plasmid gene content was similar. Regardless of the evolutionary separation, similar features of resistance to β-lactams and quinolones/fluoroquinolones indicated parallel evolution of antimicrobial resistance in both regions.

Clinically Unreported Salmonellosis Outbreak Detected via Comparative Genomic Analysis of Municipal Wastewater Salmonella Isolates

Municipal wastewater includes human waste that contains both commensal and pathogenic enteric microorganisms, and this collective community microbiome can be monitored for community diseases. In a previous study, we assessed the salmonellosis disease burden using municipal wastewater from Honolulu, Hawaii, which was monitored over a 54-week period. During that time, a strain of Salmonella enterica serovar Paratyphi B variant L(+) tartrate(+) (also known as Salmonella enterica serovar Paratyphi B variant Java) was identified; this strain was detected simultaneously with a clinically reported outbreak, and pulsed-field gel electrophoresis patterns were identical for clinical and municipal wastewater isolates. Months after the outbreak subsided, the same pulsotype was detected as the dominant pulsotype in municipal wastewater samples, with no corresponding clinical cases reported. Using genomic characterization (including core single-nucleotide polymorphism alignment, core genome multilocus sequence typing, and screening for virulence and antibiotic resistance genes), all S Java municipal wastewater isolates were determined to be clonal, indicating a resurgence of the original outbreak strain. This demonstrates the feasibility and utility of municipal wastewater surveillance for determining enteric disease outbreaks that may be missed by traditional clinical surveillance methods.IMPORTANCE Underdetection of microbial infectious disease outbreaks in human communities carries enormous health costs and is an ongoing problem in public health monitoring (which relies almost exclusively on data from health clinics). Surveillance of municipal wastewater for community-level monitoring of infectious disease burdens has the potential to fill this information gap, due to its easy access to the mixed community microbiome. In the present study, the genomes of 21 S Java isolates (collected from municipal wastewater in Honolulu) were analyzed; results showed that the same Salmonella strain that caused a known salmonellosis clinical outbreak in spring 2010 remerged as the most dominant strain in municipal wastewater in spring 2011, indicating a new outbreak that was not detected by health clinics. Our results show that wastewater monitoring holds great promise to inform the field of public health regarding outbreak status within communities.

Improving Our Understanding of Salmonella enterica Serovar Paratyphi B through the Engineering and Testing of a Live Attenuated Vaccine Strain

We developed a live attenuated Salmonella enterica serovar Paratyphi B vaccine that conferred protection in mice against challenge with S. Paratyphi B sensu stricto and S. Paratyphi B Java, which are the causes of enteric fever and gastroenteritis, respectively. Currently, the incidence of invasive S. Paratyphi B sensu stricto infections is low; however, the development of new conjugate vaccines against other enteric fever serovars could lead to the emergence of S. Paratyphi B to fill the niche left by these other pathogens. As such, an effective S. Paratyphi B vaccine would be a useful tool in the armamentarium against Salmonella infections. Comparative genomics confirmed the serovar-specific groupings of these isolates and revealed that there are a limited number of genetic differences between the sensu stricto and Java strains, which are mostly hypothetical and phage-encoded proteins. The observed level of genomic similarity likely explains why we observe some cross-protection.

Enteric fever is caused by three Salmonella enterica serovars: Typhi, Paratyphi A, and Paratyphi B sensu stricto. Although vaccines against two of these serovars are licensed (Typhi) or in clinical development (Paratyphi A), as yet there are no candidates for S. Paratyphi B. To gain genomic insight into these serovars, we sequenced 38 enteric fever-associated strains from Chile and compared these with reference genomes. Each of the serovars was separated genomically based on the core genome. Genomic comparisons identified loci that were aberrant between serovars Paratyphi B sensu stricto and Paratyphi B Java, which is typically associated with gastroenteritis; however, the majority of these were annotated as hypothetical or phage related and thus were not ideal vaccine candidates. With the genomic information in hand, we engineered a live attenuated S. Paratyphi B sensu stricto vaccine strain, CVD 2005, which was capable of protecting mice from both homologous challenge and heterologous challenge with S. Paratyphi B Java. These findings extend our understanding of S. Paratyphi B and provide a viable vaccine option for inclusion in a trivalent live attenuated enteric fever vaccine formulation.

IMPORTANCE We developed a live attenuated Salmonella enterica serovar Paratyphi B vaccine that conferred protection in mice against challenge with S. Paratyphi B sensu stricto and S. Paratyphi B Java, which are the causes of enteric fever and gastroenteritis, respectively. Currently, the incidence of invasive S. Paratyphi B sensu stricto infections is low; however, the development of new conjugate vaccines against other enteric fever serovars could lead to the emergence of S. Paratyphi B to fill the niche left by these other pathogens. As such, an effective S. Paratyphi B vaccine would be a useful tool in the armamentarium against Salmonella infections. Comparative genomics confirmed the serovar-specific groupings of these isolates and revealed that there are a limited number of genetic differences between the sensu stricto and Java strains, which are mostly hypothetical and phage-encoded proteins. The observed level of genomic similarity likely explains why we observe some cross-protection.

Genomic interplay in bacterial communities: implications for growth promoting practices in animal husbandry

The discovery of antibiotics heralded the start of a “Golden Age” in the history of medicine. Over the years, the use of antibiotics extended beyond medical practice into animal husbandry, aquaculture and agriculture. Now, however, we face the worldwide threat of diseases caused by pathogenic bacteria that are resistant to all existing major classes of antibiotic, reflecting the possibility of an end to the antibiotic era. The seriousness of the threat is underscored by the severely limited production of new classes of antibiotics. Evolution of bacteria resistant to multiple antibiotics results from the inherent genetic capability that bacteria have to adapt rapidly to changing environmental conditions. Consequently, under antibiotic selection pressures, bacteria have acquired resistance to all classes of antibiotics, sometimes very shortly after their introduction. Arguably, the evolution and rapid dissemination of multiple drug resistant genes en-masse across microbial pathogens is one of the most serious threats to human health. In this context, effective surveillance strategies to track the development of resistance to multiple antibiotics are vital to managing global infection control. These surveillance strategies are necessary for not only human health but also for animal health, aquaculture and plant production. Shortfalls in the present surveillance strategies need to be identified. Raising awareness of the genetic events that promote co-selection of resistance to multiple antimicrobials is an important prerequisite to the design and implementation of molecular surveillance strategies. In this review we will discuss how lateral gene transfer (LGT), driven by the use of low-dose antibiotics in animal husbandry, has likely played a significant role in the evolution of multiple drug resistance (MDR) in Gram-negative bacteria and has complicated molecular surveillance strategies adopted for predicting imminent resistance threats.

Isolation and characterization of a rare waterborne lytic phage of Salmonella enterica serovar Paratyphi B

A lytic phage of Salmonella serovar Paratyphi B, named φSPB, was isolated from surface waters of the Pavana River in India. Phage φSPB is a member of the Podoviridae family and is morphologically similar to the 7-11 phages of the C3 morphotype of tailed phages, characterized by a very long, cigar-shaped head. The head measured approximately 153 × 57 nm, and the tail size was 12 × 7 nm. The phage was stable over a wide range of pH (4–9) and temperature (4–40 °C). The adsorption rate constant was 4.7 × 10−10. Latent and eclipse periods were 10 and 15 min, respectively, and the burst size was 100 plaque-forming units/infected cell after 25 min at 37 °C. The phage DNA was 59 kb in size. Ten major proteins were observed on SDS–PAGE, although some of these proteins could be bacterial contaminants. This is the first report of Salmonella enterica subsp. enterica serovar Paratyphi B phage of C3 morphotype from India that has many unique features, such as high replication potential, short replication time, and stability over a wide range of pH and temperature, making it a promising biocontrol agent against the drug-resistant strains of Salmonella Paratyphi B.

Mobile elements, zoonotic pathogens and commensal bacteria: conduits for the delivery of resistance genes into humans, production animals and soil microbiota

Multiple antibiotic resistant pathogens represent a major clinical challenge in both human and veterinary context. It is now well-understood that the genes that encode resistance are context independent. That is, the same gene is commonly present in otherwise very disparate pathogens in both humans and production and companion animals, and among bacteria that proliferate in an agricultural context. This can be true even for pathogenic species or clonal types that are otherwise confined to a single host or ecological niche. It therefore follows that mechanisms of gene flow must exist to move genes from one part of the microbial biosphere to another. It is widely accepted that lateral (or horizontal) gene transfer (L(H)GT) drives this gene flow. LGT is relatively well-understood mechanistically but much of this knowledge is derived from a reductionist perspective. We believe that this is impeding our ability to deal with the medical ramifications of LGT. Resistance genes and the genetic scaffolds that mobilize them in multiply drug resistant bacteria of clinical significance are likely to have their origins in completely unrelated parts of the microbial biosphere. Resistance genes are increasingly polluting the microbial biosphere by contaminating environmental niches where previously they were not detected. More attention needs to be paid to the way that humans have, through the widespread application of antibiotics, selected for combinations of mobile elements that enhance the flow of resistance genes between remotely linked parts of the microbial biosphere. Attention also needs to be paid to those bacteria that link human and animal ecosystems. We argue that multiply antibiotic resistant commensal bacteria are especially important in this regard. More generally, the post genomics era offers the opportunity for understanding how resistance genes are mobilized from a one health perspective. In the long term, this holistic approach offers the best opportunity to better manage what is an enormous problem to humans both in terms of health and food security.

Human infections attributable to the D-tartrate-fermenting variant of Salmonella enterica serovar Paratyphi B in Germany originate in reptiles and, on rare occasions, poultry

In this study, the population structure, incidence, and potential sources of human infection caused by the d-tartrate-fermenting variant of Salmonella enterica serovar Paratyphi B [S. Paratyphi B (dT+)] was investigated. In Germany, the serovar is frequently isolated from broilers. Therefore, a selection of 108 epidemiologically unrelated S. enterica serovar Paratyphi B (dT+) strains isolated in Germany between 2002 and 2010 especially from humans, poultry/poultry meat, and reptiles was investigated by phenotypic and genotypic methods. Strains isolated from poultry and products thereof were strongly associated with multilocus sequence type ST28 and showed antimicrobial multiresistance profiles. Pulsed-field gel electrophoresis XbaI profiles were highly homogeneous, with only a few minor XbaI profile variants. All strains isolated from reptiles, except one, were strongly associated with ST88, another distantly related type. Most of the strains were susceptible to antimicrobial agents, and XbaI profiles were heterogeneous. Strains isolated from humans yielded seven sequence types (STs) clustering in three distantly related lineages. The first lineage, comprising five STs, represented mainly strains belonging to ST43 and ST149. The other two lineages were represented only by one ST each, ST28 and ST88. The relatedness of strains based on the pathogenicity gene repertoire (102 markers tested) was mostly in agreement with the multilocus sequence type. Because ST28 was frequently isolated from poultry but rarely in humans over the 9-year period investigated, overall, this study indicates that in Germany S. enterica serovar Paratyphi B (dT+) poses a health risk preferentially by contact with reptiles and, to a less extent, by exposure to poultry or poultry meat.

Zoonotic bacteria, antimicrobial use and antimicrobial resistance in ornamental fish: a systematic review of the existing research and survey of aquaculture-allied professionals

Using systematic review methodology, global research reporting the frequency of zoonotic bacterial pathogens, antimicrobial use (AMU) and antimicrobial resistance (AMR) in ornamental fish, and human illness due to exposure to ornamental fish, was examined. A survey was performed to elicit opinions of aquaculture-allied personnel on the frequency of AMU and AMR in ornamental fish. The most commonly reported sporadic human infections were associated withMycobacterium marinum, whileSalmonellaParatyphi B var. Java was implicated in all reported outbreaks.Aeromonasspp. were most frequently investigated (n=10 studies) in 25 studies surveying ornamental fish from various sources. High levels of resistance were reported to amoxicillin, penicillin, tetracycline and oxytetracycline, which was also in agreement with the survey respondents' views. Studies on AMU were not found in our review. Survey respondents reported frequent use of quinolones, followed by tetracyclines, nitrofurans, and aminoglycosides. Recommendations for future surveillance and public education efforts are presented.

Salmonella genomic islands and antibiotic resistance in Salmonella enterica

Antibiotic resistance in several Salmonella enterica serovars that cause gastrointestinal disease in humans is due to a set of related genomic islands carrying a class 1 integron, which carries the resistance genes. Salmonella genomic island 1 (SGI1), the first island of this type, was found in S. enterica serovar Typhimurium DT104 isolates, which are resistant to ampicillin, chloramphenicol, florfenicol, streptomycin, spectinomycin, sulfonamides and tetracycline. Several Salmonella serovars and Proteus mirablis have since been shown to harbor SGI1 or related islands carrying various sets of resistance genes and some distinct groups have emerged. SGI1 is an integrative mobilizable element and can be transferred experimentally into Escherichia coli. However, within serovars, isolates recovered from different parts of the world appear to be clonal, indicating that SGI1 movement may be rare. Potential reservoirs in food-producing animals or in ornamental fish have been identified for some serovars.

Unusual class 1 integron configuration found in Salmonella genomic island 2 from Salmonella enterica serovar Emek

Salmonella genomic island 2 (SGI2) is an independently derived genomic island related to SGI1 with the integron in a different position. The integron in SGI2 was found to include an additional 2.1 kb derived from the tni module of Tn5058, Tn502, or Tn512 that was not detected previously. Independent evolution of the backbone was confirmed with 21 single base differences found in over 11.5 kb, representing 40% of the 27.4-kb SGI2 backbone.

Multistate outbreak of Salmonella infections associated with small turtle exposure, 2007-2008

OBJECTIVE

Turtle-associated salmonellosis was increasingly recognized in the United States during the 1960s, leading to a federal ban in 1975 on the sale of turtles <4 inches in carapace length (small turtles). Although sporadic reports of turtle-associated Salmonella are frequent, outbreaks are rare. In September 2007, several patients with Salmonella enterica serotype Paratyphi B var Java infections reported recent turtle exposure. We conducted an investigation to determine the source and extent of the infections.

PATIENTS AND METHODS

Patients with Salmonella Paratyphi B var Java infections with a specific pulsed-field gel electrophoresis pattern (outbreak strain) and illness onset between May 2007 and January 2008, were compared with healthy controls. Reptile exposure and awareness of a Salmonella-reptile link were assessed. Turtle size and purchase information were collected.

RESULTS

We identified 107 patients with outbreak-strain infections. The median patient age was 7 years; 33% were hospitalized. Forty-seven (60%) of 78 patients interviewed reported exposure to turtles during the week before illness; 41 (87%) were small turtles, and 16 (34%) were purchased in a retail pet store. In the case-control study, 72% of 25 patients reported turtle exposure during the week before illness compared with 4% of 45 controls (matched odds ratio [mOR]: 40.9 [95% confidence interval (CI): 6.9-unbounded]). Seven (32%) of 22 patients versus 11 (28%) of 39 controls reported knowledge of a link between reptile exposure and Salmonella infection (mOR: 1.3 [95% CI: 0.4-4.6]).

CONCLUSIONS

We observed a strong association between turtle exposure and Salmonella infections in this outbreak. Small turtles continue to be sold and pose a health risk, especially to children; many people remain unaware of the link between Salmonella infection and reptile contact.

Characterization of pathogenic and resistant genome repertoire reveals two clonal lines in Salmonella enterica subsp. enterica serovar Paratyphi B (+)-tartrate positive

A total of 36 contemporary human, animal, and environmental (+)-tartrate-fermenting (dT+) Salmonella enterica serovar Paratyphi B isolates, formerly called Salmonella serovar Java, and five related monophasic S. enterica serovar 4,5,12:b:- isolates from Belgium, Germany, the Netherlands, and the United Kingdom were investigated for clonality and antimicrobial resistance profiles, as well as their virulence and resistance gene repertoire. Two major clonal lines, which could be phenotypically differentiated by the expression of the O:5 antigen, were identified. All O:5 antigen negative strains were multidrug resistant and originated (with two exceptions) from Belgian, Dutch, or German poultry. Strains exhibiting the O:5 antigen encoded by the oafA gene revealed a more heterogeneous group including multidrug-resistant and susceptible strains. Compared to O:5 antigen negative isolates, Salmonella Paratyphi B dT+ O:5 positive strains possessed additional virulence determinants. The Salmonella genomic island 1 was only found in O:5 positive strains. Five monophasic Salmonella 4,5,12:b:- lacking the phase-2 flagellar antigen were assigned to Salmonella Paratyphi B dT+ isolates of the O:5 positive group. The conclusion of the analysis is that Salmonella Paratyphi B dT+ O:5 negative and O:5 positive isolates evolved from a different lineage. Salmonella Paratyphi B dT+ O:5 positive strains possess additional fimbrial and virulence genes that probably enable this clone to interact with a broader range of hosts and the environment. Salmonella Paratyphi B dT+ O:5 negative continuously persists in poultry across Western Europe, especially Belgium, the Netherlands, and Germany.

Emergence and evolution of multiply antibiotic-resistant Salmonella enterica serovar Paratyphi B D-tartrate-utilizing strains containing SGI1

The first Australian isolate of Salmonella enterica serovar Paratyphi B D-tartrate-utilizing (dT(+)) that is resistant to ampicillin, chloramphenicol, florfenicol, streptomycin, spectinomycin, sulfonamides, and tetracycline (ApCmFlSmSpSuTc) and contains SGI1 was isolated from a patient with gastroenteritis in early 1995. This is the earliest reported isolation globally. The incidence of infections caused by these SGI1-containing multiply antibiotic-resistant S. enterica serovar Paratyphi B dT(+) strains increased during the next few years and occurred sporadically in all states of Australia. Several molecular criteria were used to show that the early isolates are very closely related to one another and to strains isolated during the following few years and in 2000 and 2003 from home aquariums and their owners. Early isolates from travelers returning from Indonesia shared the same features. Thus, they appear to represent a true clone arising from a single cell that acquired SGI1. Some minor differences in the resistance profiles and molecular profiles also were observed, indicating the ongoing evolution of the clone, and phage type differences were common, indicating that this is not a useful epidemiological marker over time. Three isolates from 1995, 1998, and 1999 contained a complete sul1 gene but were susceptible to sulfamethoxazole due to a point mutation that creates a premature termination codon. This SGI1 type was designated SGI1-R. The loss of resistance genes also was examined. When strains were grown for many generations in the absence of antibiotic selection, the loss of SGI1 was not detected. However, variants SGI1-C (resistance profile SmSpSu) and SGI1-B (resistant to ApSu), which had lost part of the integron, arose spontaneously, presumably via homologous recombination between duplications in the In104 complex integron.

SGI2, a relative of Salmonella genomic island SGI1 with an independent origin

Multiply antibiotic-resistant Salmonella enterica serovar Emek strains isolated in Australia and the United Kingdom had similar features, suggesting that they all belong to a single clone. These strains all contain SGI2 (formerly SGI1-J), an independently formed relative of Salmonella genomic island SGI1. In SGI2, the complex class 1 integron which includes all of the resistance genes is not located between tnpR (S027) and S044 as in SGI1 and SGI1 variants. Instead, tnpR was found to be adjacent to S044, and the integron is located 6.9 kb away, within S023. In both SGI1 and SGI2, the 25-bp inverted repeats that mark the outer ends of class 1 integrons are flanked by a 5-bp duplication of the target, indicating that incorporation of the integron was by transposition. A small number of differences between the sequences of the backbones of SGI1 and SGI2 were also found. Hence, a class 1 integron has entered two different variants of the SGI backbone to generate two distinct lineages. Despite this, the integron in SGI2 has a complex structure that is very similar to that of In104 in SGI1. Differences are in the cassette arrays and in the gene which encodes the chloramphenicol and florfenicol efflux protein. The CmlA9 protein, encoded by InEmek, is only 92.8% identical to FloRc (also a CmlA family protein) from SGI1. A variant form of SGI2, SGI2-A, which has lost the tet(G) and cmlA9 resistance determinants, was found in one strain.