Pediatric infection due to multiresistant Salmonella enterica serotype Infantis in Honduras

Community-Acquired Antimicrobial Resistant Enterobacteriaceae in Central America: A One Health Systematic Review

Community-acquired antimicrobial resistant Enterobacteriaceae (CA-ARE) are an increasingly important issue around the world. Characterizing the distribution of regionally specific patterns of resistance is important to contextualize and develop locally relevant interventions. This systematic review adopts a One Health framework considering the health of humans, animals, and the environment to describe CA-ARE in Central America. Twenty studies were identified that focused on antimicrobial resistance (AMR) in Enterobacteriaceae. Studies on CA-ARE in Central America characterized resistance from diverse sources, including humans (n = 12), animals (n = 4), the environment (n = 2), and combinations of these categories (n = 2). A limited number of studies assessed prevalence of clinically important AMR, including carbapenem resistance (n = 3), third generation cephalosporin resistance (n = 7), colistin resistance (n = 2), extended spectrum beta-lactamase (ESBL) production (n = 4), or multidrug resistance (n = 4). This review highlights significant gaps in our current understanding of CA-ARE in Central America, most notably a general dearth of research, which requires increased investment and research on CA-ARE as well as AMR more broadly.

Differences in the expression of SPI-1 genes pathogenicity and epidemiology between the emerging Salmonella enterica serovar Infantis and the model Salmonella enterica serovar Typhimurium

BACKGROUND

Salmonella enterica serovar Infantis (S. Infantis) is one of the ubiquitous serovars of the bacterial pathogen S. enterica and recently has been emerging in many countries worldwide. Nonetheless, not much is known about its epidemiology, host adaptation, and virulence.

METHODS

Epidemiological and molecular approaches were used together with tissue-culture and mouse models to conduct phenotypic comparison with the model S. enterica serovar Typhimurium.

RESULTS

We show that S. Infantis is more frequently associated with infections in infants <2 years old and prone to cause significantly less invasive infections than serovar Typhimurium. Moreover, although S. Infantis adheres better to host cells and highly colonizes mouse intestines soon after infection, it is significantly less invasive and induces much lower inflammation and disease in vivo than S. Typhimurium. These differences were associated with lower expression of Salmonella pathogenicity island (SPI) 1 genes in S. Infantis than in S. Typhimurium.

CONCLUSIONS

Our results demonstrate previously unknown differences in the epidemiology, virulence pathway expression, and pathogenicity between two highly abundant Salmonella serovars and suggest that native variation in the expression of the SPI-1 regulon is likely to contribute to epidemiological and virulence variation between genetically similar nontyphoidal Salmonella serovars.

Genome Sequence of an Emerging Salmonella enterica Serovar Infantis and Genomic Comparison with Other S. Infantis Strains

Salmonella enterica serovar Infantis (S. Infantis) is one of the dominant serovars of the bacterial pathogen S. enterica. In recent years, the number of human infections caused by S. Infantis has been increasing in many countries, and often the emerging population harbors a unique virulence-resistant megaplasmid called plasmid of emerging S. Infantis (pESI). Here, we report the complete gap-free genome sequence of the S. Infantis Israeli emerging clone and compare its chromosome and pESI sequences with other complete S. Infantis genomes. We show a conserved presence of the Salmonella pathogenicity islands 1-6, 9, 11, 12, and CS54 and a common integration of five bacteriophages in the S. Infantis chromosome. In contrast, we found variable presence of additionally three chromosomally integrated phages and eight modular regions in pESI, which contribute to the genetic and phenotypic diversity (including antimicrobial resistance) of this ubiquitous foodborne pathogen.

Antimicrobial resistance and genetic diversity of Salmonella Infantis isolated from foods and human samples in Morocco

OBJECTIVES

Genotyping of Salmonella strains is an important molecular tool to discriminate isolates and to improve epidemiological studies when an outbreak occurs. Among the DNA-based genotyping methods, pulsed-field gel electrophoresis (PFGE) is currently used to subtype Salmonella isolates. In this study, the feasibility of genotyping Salmonella enterica serotype Infantis strains using XbaI restriction enzyme was evaluated. Separation of restricted fragments was performed by PFGE.

METHODS

To test the possibility of applying this methodology to epidemiological investigation, a collection of 26 Salmonella Infantis strains were tested for their susceptibility to 14 antimicrobial agents and were analysed by XbaI macrorestriction followed by PFGE. Detection of class 1 integrons as well as intI1 and bla_TEM genes in resistant strains was also studied.

RESULTS

Antimicrobial susceptibility testing showed that 84.6% (22/26) of Salmonella Infantis isolates were susceptible to all of the antimicrobials tested, whereas 7.7% (2/26) had low-level resistance to β-lactams and harboured the bla_TEM gene. A class 1 integron (0.8kb) and the intI1 gene (898bp) were detected in one Salmonella Infantis strain. However, five different PFGE profiles were defined by XbaI macrorestriction.

CONCLUSIONS

The PFGE method demonstrated adequate typing ability and represents a powerful tool to discriminate the serotype Salmonella Infantis.

Oral vaccination with a live Salmonella Enteritidis/Typhimurium bivalent vaccine in layers induces cross-protection against caecal and internal organ colonization by a Salmonella Infantis strain

Salmonella is an important zoonotic agent, and poultry products remain one of the main sources of infection for humans. Salmonella Infantis is an emerging serotype in poultry worldwide, reflected by an increased prevalence in poultry flocks, on broiler meat and in human foodborne illness cases. In the current study, the efficacy of oral administration of a live monovalent Salmonella Enteritidis and a live bivalent Salmonella Enteritidis/Typhimurium vaccine, against a Salmonella Enteritidis and Infantis infection, was determined. Oral administration of the live vaccines to day-old chickens caused a decrease in caecal colonization by Salmonella Enteritidis, but not Infantis, at day 7, when challenged at day 2. Vaccination with the bivalent vaccine at day 1 resulted in a decreased spleen colonization by both Salmonella Infantis and Enteritidis. Twice (at day 1 and week 6) and thrice vaccination (at day 1, week 6 and 16) of laying hens with the bivalent vaccine resulted in a decreased caecal colonization by Salmonella Enteritidis and Infantis, and significantly lower oviduct colonization levels by Salmonella Enteritidis. These data show cross-protection against Salmonella Infantis by oral administration of live vaccine strains belonging to other serogroups.

The plasmid-encoded Ipf and Klf fimbriae display different expression and varying roles in the virulence of Salmonella enterica serovar Infantis in mouse vs. avian hosts

Salmonella enterica serovar Infantis is one of the prevalent Salmonella serovars worldwide. Different emergent clones of S. Infantis were shown to acquire the pESI virulence-resistance megaplasmid affecting its ecology and pathogenicity. Here, we studied two previously uncharacterized pESI-encoded chaperone-usher fimbriae, named Ipf and Klf. While Ipf homologs are rare and were found only in S. enterica subspecies diarizonae and subspecies VII, Klf is related to the known K88-Fae fimbria and klf clusters were identified in seven S. enterica subspecies I serovars, harboring interchanging alleles of the fimbria major subunit, KlfG. Regulation studies showed that the klf genes expression is negatively and positively controlled by the pESI-encoded regulators KlfL and KlfB, respectively, and are activated by the ancestral leucine-responsive regulator (Lrp). ipf genes are negatively regulated by Fur and activated by OmpR. Furthermore, induced expression of both klf and ipf clusters occurs under microaerobic conditions and at 41°C compared to 37°C, in-vitro. Consistent with these results, we demonstrate higher expression of ipf and klf in chicks compared to mice, characterized by physiological temperature of 41.2°C and 37°C, respectively. Interestingly, while Klf was dispensable for S. Infantis colonization in the mouse, Ipf was required for maximal colonization in the murine ileum. In contrast to these phenotypes in mice, both Klf and Ipf contributed to a restrained infection in chicks, where the absence of these fimbriae has led to moderately higher bacterial burden in the avian host. Taken together, these data suggest that physiological differences between host species, such as the body temperature, can confer differences in fimbriome expression, affecting Salmonella colonization and other host-pathogen interplays.

A unique megaplasmid contributes to stress tolerance and pathogenicity of an emergent Salmonella enterica serovar Infantis strain

Of all known Salmonella enterica serovars, S. Infantis is one of the most commonly isolated and has been recently emerging worldwide. To understand the recent emergence of S. Infantis in Israel, we performed extensive comparative analyses between pre-emergent and the clonal emergent S. Infantis populations. We demonstrate the fixation of adaptive mutations in the DNA gyrase (gyrA) and nitroreductase (nfsA) genes, conferring resistance to quinolones and nitrofurans, respectively, and the carriage of an emergent-specific plasmid, designated pESI. This self-transferred episome is a mosaic megaplasmid (∼280 kb), which increases bacterial tolerance to environmental mercury (mer operon) and oxidative stress, and provides further resistance to tetracycline, sulfamethoxazole and trimethoprim, most likely due to the presence of tetRA, sulI and dfrA genes respectively. Moreover, pESI carries the yersiniabactin siderophore system and two novel chaperone-usher fimbriae. In vitro studies established that pESI conjugation into a plasmidless S. Infantis strain results in superior biofilm formation, adhesion and invasion into avian and mammalian host cells. In vivo mouse infections demonstrated higher pathogenicity and increased intestinal inflammation caused by an S. Infantis strain harboring pESI compared with the plasmidless parental strain. Our results indicate that the presence of pESI that was found only in the emergent population of S. Infantis in Israel contributes significantly to antimicrobials tolerance and pathogenicity of its carrier. It is highly likely that pESI plays a key role in the successful spread of the emergent clone that replaced the local S. Infantis community in the short time of only 2-3 years.

Characterization of antibiotic resistance and the emergence of AmpC-producing Salmonella Infantis from pigs

During the period of 2007-2008, a total of 270 pig fecal samples were collected from a meat processing plant located in southern Japan and examined for Salmonella species. A total of 44 Salmonella isolates were recovered, and antimicrobial resistance was detected in serotypes Typhimurium (n=9), Infantis and Choleraesuis (n=2), and Derby, Miyazaki and Schwarzengrund (n=1). Multidrug resistance was seen in serotypes Typhimurium (n=8) and Infantis (n=2). The most commonly observed resistance phenotypes were against streptomycin, oxytetracycline and sulfamethoxazole (100%), ampicillin (90%), chloramphenicol (50%), cephalothin (30%) and cefoxitin, ceftazidime and kanamycin (each 20%). Extended-spectrum cephalosporin-resistant Salmonella Infantis isolates producing plasmid-mediated, bla(CMY-2) gene were detected. These AmpC-producing isolates showed resistance to ampicillin and cephems (cephalothin, cefoxitin and ceftazidime). Resistance transfer experiments showed that transconjugants and transformants coexpressed resistance phenotypes similar to the donor isolates. To the best of our knowledge, this is the first report worldwide describing serovar Infantis from pigs capable of producing AmpC β-lactamase. Then, we detected the pentadrug-resistance phenotype in Salmonella Typhimurium isolates, which yielded class 1 integron amplicons of 1.0 and 1.2 kb. Genetic fingerprinting analysis by pulsed-field gel electrophoresis and an assay by polymerase chain reaction confirmed the isolates to be Salmonella Typhimurium DT104. In conclusion, the findings of this survey call for the systematic and comprehensive domestic and international surveillance programs to determine the true rates of occurrence of AmpC-producing Salmonella both in the livestock and public health sectors.

Extended-spectrum β-lactamase-producing Salmonella enterica serovar Oranienburg (CTX-M-2 group) in a pediatric hospital in Tucumán, Argentina

INTRODUCTION: Salmonella sp infections have been reported over recent years in hospitals in Argentina and other countries due to multiresistant strains. The aim of this study was to characterize the extended-spectrum β-lactamases in third-generation cephalosporin-resistant strains of Salmonella enterica serovar Oranienburg. METHODS: We studied 60 strains isolated from children with gastroenteritis and/or extraintestinal complications. The antibiotic susceptibility patterns of the isolates were analyzed and the β-lactamases were characterized using phenotyping and genotyping methods. RESULTS: All the strains were resistant to ampicillin, cefotaxime, cefepime and aztreonam and partially susceptible to ceftazidime, thus corresponding well with the resistance phenotype conferred by CTX-M-type β-lactamases. An isoelectric point enzyme (pI = 7.9) was detected in all of the strains, and this was confirmed by PCR as a member of the CTX-M-2 group. CONCLUSIONS: This is the first report of Salmonella enterica serovar Oranienburg producing β-lactamases of the CTX-M-2 group in a pediatric hospital in Tucumán, Argentina.

Genetic analysis of multi-drug resistance and the clonal dissemination of beta-lactam resistance in Salmonella Infantis isolated from broilers

An epidemiologic study was conducted to investigate the incidence and characterize the antimicrobial resistance determinants, analyzing plasmid profiles, and establishing the genetic relationship among beta-lactam-resistant isolates of Salmonella Infantis from broilers in Southern Japan. A total of 120 isolates were recovered from 56 flocks belonging to 44 holdings during 2004-2006. The percentages of resistance were as follows: ampicillin (24%), cephalothin (23%), cefoxitin (0%), ceftazidime (11%), cefotaxime (11%), chloramphenicol (0%), kanamycin (7.5%), ofloxacin (20%), oxytetracycline, streptomycin and sulfamethoxazole (100%) and trimethoprim (75%). The incidence of bla(TEM)-encoded beta-lactam resistance in 2004-2006 was significantly higher than in 1998-2003 (P<0.001). BlnI-digested PFGE patterns generated two related clusters implicated in the dissemination of beta-lactam resistance. Two types of plasmid profiles were observed and two plasmids of ca. 50 and 180-kb size were carried by beta-lactam-resistant isolates. Streptomycin resistance was conferred by aadA1 (n=116), aadA1-aadA2 (n=1), and aadA1-strA-strB (n=3). Resistances to kanamycin, oxytetracycline, sulfamethoxazole and trimethoprim were conferred by aphA1 (n=9, 100%), tetA (n=120, 100%) sul1 (n=120, 100%) and dfrA5 (n=90, 100%), respectively. Two types of class 1 integrons were detected: 1.0 kb (n=120) and, 1.0/1.5 kb (n=3). Integrons of 1.0/1.5 kb were found in isolates with the aadA1-strA-strB gene combination. For the first time, all S. Infantis isolates showed resistance to at least three classes of antimicrobial agents; and the intestinal tract of healthy poultry was a reservoir of the extended-spectrum cephalosporin-resistant isolates of serovar Infantis.

Comparison of Salmonella enterica serotype Infantis isolates from a veterinary teaching hospital

AIMS

To compare Salmonella enterica serotype Infantis isolates obtained from patients or the environment of a veterinary teaching hospital over a period of 9 years following a nosocomial outbreak to determine whether isolates were epidemiologically related or represented unrelated introductions into the hospital environment.

METHODS AND RESULTS

Fifty-six S. Infantis isolates were compared based on their phenotypic (antimicrobial drug [AMD] susceptibility pattern) and genotypic (pulsed-field gel electrophoresis [PFGE] pattern and presence of integrons) characteristics. Epidemiologically unrelated S. Infantis isolates clustered separately from all but two of the hospital isolates, and several isolates from different years and various sources were indistinguishable from each other in cluster analysis of two-enzyme PFGE results. A high percentage of isolates (80.3%) were resistant to at least one AMD, with 67.8% showing resistance to >5 AMD. The majority (74.1%) of isolates tested contained type 1 integrons.

CONCLUSION

Results strongly suggest that there was nosocomial transmission of S. Infantis during the initial outbreak, and that contamination arising from this outbreak persisted across years despite rigorous hygiene and biosecurity precautions and may have led to subsequent nosocomial infections.

SIGNIFICANCE AND IMPACT OF THE STUDY

Evidence of persistence and transmission of Salmonella clones across years, even in the face of rigorous preventive measures, has important implications for other facilities that have experienced outbreaks of Salmonella infections.

Molecular epidemiology of antimicrobial resistance among Salmonella enterica serovar Infantis from poultry in Kagoshima, Japan

Antimicrobial susceptibility and resistance genes of 135 strains of Salmonella enterica serovar Infantis isolated from poultry in Kagoshima were examined. One strain (0.7%) was resistant to ampicillin (A), 97% to streptomycin (S), 95.6% to sulphamethoxazole (Su), 96.3% to oxytetracycline (T), 11.1% to kanamycin (Km) and 36.3% to ofloxacin (O). Multiresistant phenotypes identified were ASSuT-Km, SSuT-Km, SSuT-O and SSuT. Class 1 integrons were detected in 94.8% of isolates. Approximately 89% of oxytetracycline-resistant strains carried the tetA gene and all of the 131 streptomycin-resistant isolates carried the aadA1a gene. Forty-percent of kanamycin-resistant isolates carried the aphA1-Iab gene. All isolates were susceptible to chloramphenicol. Recognition of TEM-type beta-lactamase in a S. Infantis strain from chickens is a recent rare finding in Japan.

Longitudinal farm study of extended-spectrum beta-lactamase-mediated resistance

Extended-spectrum beta-lactamase (ESBL)-mediated resistance is of considerable importance in human medicine. Recently, such enzymes have been reported in bacteria from animals. We describe a longitudinal study of a dairy farm suffering calf scour with high mortality rates. In November 2004, two Escherichia coli isolates with resistance to a wide range of beta-lactams (including amoxicillin-clavulanate and cefotaxime) were isolated from scouring calves. Testing by PCR and sequence analysis confirmed the isolates as being both bla(CTX-M14/17) and bla(TEM-35) ((IRT-4)) positive. They had indistinguishable plasmid and pulsed-field gel electrophoresis (PFGE) profiles. Transferability studies demonstrated that bla(CTX-M) was located on a conjugative 65-MDa IncK plasmid. Following a farm visit in December 2004, 31/48 calves and 2/60 cows were positive for E. coli with bla(CTX-M). Also, 5/48 calf and 28/60 cow samples yielded bla(CTX)- and bla(TEM)-negative E. coli isolates that were resistant to cefotaxime, and sequence analysis confirmed that these presented mutations in the promoter region of the chromosomal ampC gene. Fingerprinting showed 11 different PFGE types (seven in bla(CTX-M)-positive isolates). Six different PFGE clones conjugated the same bla(CTX-M)-positive IncK plasmid. One clone carried a different-sized, bla(CTX-M)-positive, transformable plasmid. This is the first report of bla(CTX-M) from livestock in the United Kingdom, and this report demonstrates the complexity of ESBL epidemiology. Results indicate that horizontal plasmid transfer between strains as well as horizontal gene transfer between plasmids have contributed to the spread of resistance. We have also shown that some clones can persist for months, suggesting that clonal spread also contributes to the perpetuation of resistance.

Salmonella resistant to extended-spectrum cephalosporins: prevalence and epidemiology

Salmonella resistant to extended-spectrum cephalosporins (ESCs) have emerged worldwide since 1988. By 2004, 43 countries had reported this public health problem. Resistance was mediated by classical extended-spectrum beta-lactamases, plasmid-mediated cephalosporinases, and recently a class A carbapenemase. Of these, CMY-2 is the most widely disseminated enzyme. Salmonella enterica serotype Typhimurium and S. enterica serotype Enteritidis are the most common serovars associated with ESC resistance in human infections. Many outbreaks in humans have been reported, most often among children and neonates. ESC-resistant Salmonella is frequently recovered from animals and food, with poultry as primary food source, suggesting that humans are often infected by these routes.

Resistance to Oxyiminocephalosporins Mediated byblaTEM-52Genes in Salmonella Typhimurium from Humans in England and Wales

The emergence of antimicrobial resistance among Salmonella is a matter of great public health concern, more so in the case of extended-spectrum cephalosporins, since these antimicrobials are normally regarded as the drugs of choice for complicated cases of infection. This study was designed to determine the occurrence of resistance mediated by the presence of extended-spectrum beta-lactamases (ESBL) enzymes belonging to the TEM family. Only two isolates were detected after analysis of the 278,308 Salmonella isolates from the last 10 years. In both cases, the gene involved was a bla (TEM-52)-like, and infections were linked with foreign travel. ESBL-TEM enzymes remain very rare in Salmonella in England and Wales, and no domestic cases have been detected to date.

Detection of a bla(SHV) extended-spectrum {beta}-lactamase in Salmonella enterica serovar Newport MDR-AmpC

Salmonella enterica serovar Newport MDR-AmpC expressing TEM-1b and extended-spectrum beta-lactamase SHV-12 was isolated from affected animals during an outbreak of salmonellosis that led to a 3-month closure of one of the largest equine hospitals in the United States.

Nosocomial outbreak of pediatric gastroenteritis caused by CTX-M-14-type extended-spectrum beta-lactamase-producing strains of Salmonella enterica serovar London

CTX-M-14-type extended-spectrum beta-lactamase was first detected in Salmonella enterica serovar London strains which were isolated from three hospitalized pediatric patients with gastroenteritis. The isolates had pulsed-field gel electrophoresis patterns identical to those of the previously isolated antimicrobial-susceptible strains from community-acquired gastroenteritis, suggesting the susceptible clone acquired the resistance.

Characterization of AmpC-mediated resistance in clinical Salmonella isolates recovered from humans during the period 1992 to 2003 in England and Wales

The increase in AmpC-mediated resistance in salmonellae constitutes a serious public health concern, since these enzymes confer resistance to a wide range of beta-lactams. One hundred six isolates were selected from 278,308 Salmonella isolates based on resistance to ampicillin and cephalosporins and were subjected to further characterization. Nine isolates had a cefoxitin inhibition diameter < or = 17 mm and were proven to be AmpC positive by multiplex PCR. Sequence analysis revealed the presence of bla(DHA-1), bla(CMY-2), and bla(CMY-4) genes. All nine isolates presented different pulsed-field gel electrophoresis restriction profiles. The AmpC genetic determinants were present in transferable plasmids of around 11, 42, 70, 98, and 99 MDa. A combination of size and restriction fragment length polymorphism (RFLP) analysis showed that all the bla(CMY) plasmids investigated in our study were different, which suggests that bla(CMY) may be located in different plasmid environments. Some United Kingdom isolates linked to foreign travel showed RFLP plasmid patterns consistent with plasmids previously seen in the United States, which suggests that bla(CMY-2) has also been disseminated through plasmid transfer. The fact that two of the domestically acquired United Kingdom isolates presented previously unseen RFLP plasmid patterns could indicate that these strains have followed routes different from those prevalent in North America or other parts of the world. This study represents the first report of bla(CMY) genes in Salmonella isolates in the United Kingdom and the first report of CMY-4 in Salmonella enterica serotype Senftenberg worldwide.