Clonal emergence of extended-spectrum beta-lactamase (CTX-M-2)-producing Salmonella enterica serovar Virchow isolates with reduced susceptibilities to ciprofloxacin among poultry and humans in Belgium and France (2000 to 2003)

Antimicrobial susceptibility and virulence characteristics of Salmonella enterica Typhimurium isolates from healthy and diseased pigs in Korea

This study compared the antimicrobial susceptibility and prevalence of virulence genes in Salmonella enterica Typhimurium isolated from healthy and diseased pigs in Korea. A total of 456 Salmonella Typhimurium isolated from healthy (n = 238) and diseased (n = 218) pigs between 1998 and 2011 were investigated. In total, 93.4% of the Salmonella Typhimurium isolates were resistant to at least one antimicrobial agent tested. The isolates were most often resistant to tetracycline (85.7%), followed by streptomycin (83.6%), nalidixic acid (67.3%), ampicillin (49.3%), chloramphenicol (42.8%), and gentamicin (37.1%). Moreover, multidrug resistance phenotype and resistance to ampicillin, florfenicol, gentamicin, nalidixic acid, neomycin, streptomycin, and tetracycline were significantly higher (P < 0.01) among Salmonella Typhimurium isolates from the diseased pigs compared with those from the healthy pigs. The most common resistance pattern observed in both groups of isolates was streptomycin-tetracycline. Overall, more than 96% of the isolates tested possessed invA, spiA, msgA, sipB, prgH, spaN, tolC, lpfC, sifA, sitC, and sopB virulence genes. The prevalence of orgA, pagC, and iroN were 50.2, 74.1, and 91.0%, respectively, whereas isolates carrying cdtB (1.5%), pefA (7.0%), and spvB (14.9%) were identified much less frequently. Furthermore, the prevalence of invA, lpfC, orgA, pagC, and iroN was significantly higher (P < 0.01) among the isolates from the diseased pigs than in isolates from the healthy pigs. Our results demonstrated that, among diseased pigs, there was significantly higher resistance to some antimicrobials and greater prevalence of some virulence genes than in healthy pigs, indicating the role these factors play in pathogenesis. Multidrug-resistant Salmonella isolates that carry virulence-associated genes are potentially more dangerous and constitute a public health concern. Thus, continuous surveillance of antimicrobial resistance and virulence characteristics in Salmonella is essential.

Long-term dissemination of CTX-M-5-producing hypermutable Salmonella enterica serovar typhimurium sequence type 328 strains in Russia, Belarus, and Kazakhstan

In this paper, we present evidence of long-term circulation of cefotaxime-resistant clonally related Salmonella enterica serovar Typhimurium strains over a broad geographic area. The genetic relatedness of 88 isolates collected from multiple outbreaks and sporadic cases of nosocomial salmonellosis in various parts of Russia, Belarus, and Kazakhstan from 1996 to 2009 was established by multilocus tandem-repeat analysis (MLVA) and multilocus sequence typing (MLST). The isolates belong to sequence type 328 (ST328) and produce CTX-M-5 β-lactamase, whose gene is carried by highly related non-self-conjugative but mobilizable plasmids. Resistance to nalidixic acid and low-level resistance to ciprofloxacin is present in 37 (42%) of the isolates and in all cases is determined by various single point mutations in the gyrA gene quinolone resistance-determining region (QRDR). Isolates of the described clonal group exhibit a hypermutable phenotype that probably facilitates independent acquisition of quinolone resistance mutations.

Association of veterinary third-generation cephalosporin use with the risk of emergence of extended-spectrum-cephalosporin resistance in Escherichia coli from dairy cattle in Japan

The use of extended-spectrum cephalosporins in food animals has been suggested to increase the risk of spread of Enterobacteriaceae carrying extended-spectrum β-lactamases to humans. However, evidence that selection of extended-spectrum cephalosporin-resistant bacteria owing to the actual veterinary use of these drugs according to criteria established in cattle has not been demonstrated. In this study, we investigated the natural occurrence of cephalosporin-resistant Escherichia coli in dairy cattle following clinical application of ceftiofur. E. coli isolates were obtained from rectal samples of treated and untreated cattle (n = 20/group) cultured on deoxycholate-hydrogen sulfide-lactose agar in the presence or absence of ceftiofur. Eleven cefazoline-resistant isolates were obtained from two of the ceftiofur-treated cattle; no cefazoline-resistant isolates were found in untreated cattle. The cefazoline-resistant isolates had mutations in the chromosomal ampC promoter region and remained susceptible to ceftiofur. Eighteen extended-spectrum cephalosporin-resistant isolates from two ceftiofur-treated cows were obtained on ceftiofur-supplemented agar; no extended-spectrum cephalosporin-resistant isolates were obtained from untreated cattle. These extended-spectrum cephalosporin-resistant isolates possessed plasmid-mediated β-lactamase genes, including bla(CTX-M-2) (9 isolates), bla(CTX-M-14) (8 isolates), or bla(CMY-2) (1 isolate); isolates possessing bla(CTX-M-2) and bla(CTX-M-14) were clonally related. These genes were located on self-transmissible plasmids. Our results suggest that appropriate veterinary use of ceftiofur did not trigger growth extended-spectrum cephalosporin-resistant E. coli in the bovine rectal flora; however, ceftiofur selection in vitro suggested that additional ceftiofur exposure enhanced selection for specific extended-spectrum cephalosporin-resistant β-lactamase-expressing E. coli clones.

Antimicrobial susceptibility of Salmonella isolates from healthy pigs and chickens (2008-2011)

Using the agar dilution method, antimicrobial susceptibility to human-use antibiotics was determined among Belgian faecal Salmonella isolates from healthy pigs and broiler chickens. Both epidemiological cut-off values and clinical breakpoints were applied for interpretation of the results. Cephalosporin-resistant isolates were examined for the presence of genes encoding CTX-M, SHV, TEM and CMY β-lactamases. All isolates with decreased quinolone susceptibility were screened for plasmid-borne genes qnr, qepA and aac(6')-Ib-cr. In all, 368 Salmonella isolates were recovered from pigs and 452 from chickens. Clinical resistance to ciprofloxacin was absent in isolates of both host species, and was 1.9 and 13.1% to cefotaxime in pig and poultry isolates, respectively. Decreased susceptibility to cefotaxime amounted to 2.2 and 0.7%, whereas for ciprofloxacin this was 3.0 and 23.0% in pig and poultry isolates, respectively. Ciprofloxacin decreased susceptibility was limited to few serovars, mainly Paratyphi B. Multidrug resistance was markedly higher for pig isolates (39.7%) than for chicken isolates (17.3%). Sixty-six cefotaxime-resistant isolates, 59 from chickens and 7 from pigs, were phenotypically determined as ESBL/AmpC producers; predominantly Paratyphi B and Typhimurium serovars. BlaCTX-M (mostly blaCTXM-1, but also blaCTXM-2 and blaCTXM-9) and blaTEM-52 were the predominant ESBL genes. Only few isolates expressed SHV-12 or an AmpC enzyme (CMY-2). Isolates of four serovars carried qnr genes: Brandenburg and Llandof from pigs, both qnrS; Indiana and Paratyphi B from chickens with qnrB and qnrA. The latter isolate carried blaCTX-M-9 and was the only strain with a plasmid-borne quinolone resistance gene among the ESBL/AmpC producers. This Salmonella survey confirms that the ESBL/AmpC producers are particularly prevalent in chickens (12.8%), and much less in pigs (1.9%). A link between plasmid-borne quinolone resistance genes and ESBLs/AmpC was uncommon.

The Study of Genetic Relationship Among Third Generation Cephalosporin-resistant Salmonella enterica Strains by ERIC-PCR

Background and Objectives:

Salmonella is an important food-borne pathogen responsible for disease in humans and animals. The aim of this study was to investigate the genetic relationship among third generation cephalosporin-resistant Salmonella enterica strains by Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR.

Methods:

The study included all Salmonella isolates obtained from clinical cases in a pediatric hospital in Tehran, Iran during 2006 to 2009. Antimicrobial susceptibility testing was performed according to the Clinical and Laboratory Standards Institute. The genetic relationship between third generation cephalosporins-resistant Salmonella enterica strains was determined using ERIC-PCR.

Results:

Of 136 Salmonella enterica isolates recovered from pediatric patients, six isolates including four Salmonella enterica serotype Infantis and two Salmonella enterica serotype Enteritidis showed an extended-spectrum cephalosporins resistant phenotype. ERIC-PCR differentiated Salmonella enterica serotypes Infantis and Enteritidis into 2 distinct clusters arbitrarily named as E1 and E2. Profile E1 was found in two Salmonella enterica serotype Enteritidis isolates, and profile E2 was found in four Salmonella enterica serotype Infantis isolates.

Conclusion:

Extended-spectrum cephalosporins resistant Salmonella could be attributed to a few predominant serotypes including Enteritidis and Infantis in this study. Genetic analysis using ERIC-PCR showed that closely related clones are responsible for the occurrence of extended-spectrum cephalosporins resistant Salmonella infection in Tehran.

Resistance to third-generation cephalosporins in human non-typhoidal Salmonella enterica isolates from England and Wales, 2010-12

OBJECTIVES

To identify the mechanism(s) underlying cefotaxime resistance in 118 of 21,641 (0.55%) non-typhoidal Salmonella enterica isolates collected from humans throughout England and Wales from January 2010 to September 2012.

METHODS

Non-duplicate isolates (n = 118) resistant to cefotaxime (MICs >1 mg/L) were screened by PCR for genes encoding CTX-M extended-spectrum β-lactamases (ESBLs) and associated ISEcp1-like elements, and for genes encoding acquired AmpC, SHV, TEM, VEB, PER and GES β-lactamases. Sequencing was used to identify specific alleles in selected isolates. Carbapenem resistance was sought by ertapenem disc screening.

RESULTS

Seventy-nine isolates (0.37% of all referred S. enterica) produced ESBLs, 37 isolates (0.17%) produced CMY-type AmpC enzymes, and 1 isolate had both enzyme types; the mechanism of cefotaxime resistance in 3 isolates could not be identified. Group 1 CTX-M genes were identified in 57 isolates belonging to 22 serotypes, with CTX-M-1 (n = 11), -15 (n = 9) and -55/57 (n = 8) the most prevalent alleles among the 29 (51%) investigated. CTX-M-2 (n = 5), -14 (n = 5), -8 (n = 1) and -65 (n = 1) were also identified. TEM-52 was identified in two isolates and SHV-12 in seven isolates. There was no evidence of carbapenem resistance. ESBL and AmpC genes were detected in both domestically acquired and travel-associated salmonellae. Eighty-nine isolates (75%) were multidrug resistant (resistant to at least three antimicrobial classes) and 42 (36%) had decreased susceptibility to ciprofloxacin (MICs 0.25-1 mg/L), with a further 13 (11%) isolates resistant (MICs >1 mg/L).

CONCLUSIONS

The prevalence of CTX-M and acquired AmpC genes in human non-typhoidal S. enterica from England and Wales is still low, but has increased from 0.03% in 2001-03 to 0.49% in 2010-12. Resistance to third-generation cephalosporins requires monitoring as it may reduce therapeutic options.

Extended-spectrum cephalosporin-resistant Gram-negative organisms in livestock: an emerging problem for human health?

Escherichia coli, Salmonella spp. and Acinetobacter spp. are important human pathogens. Serious infections due to these organisms are usually treated with extended-spectrum cephalosporins (ESCs). However, in the past two decades we have faced a rapid increasing of infections and colonization caused by ESC-resistant (ESC-R) isolates due to production of extended-spectrum-β-lactamases (ESBLs), plasmid-mediated AmpCs (pAmpCs) and/or carbapenemase enzymes. This situation limits drastically our therapeutic armamentarium and puts under peril the human health. Animals are considered as potential reservoirs of multidrug-resistant (MDR) Gram-negative organisms. The massive and indiscriminate use of antibiotics in veterinary medicine has contributed to the selection of ESC-R E. coli, ESC-R Salmonella spp. and, to less extent, MDR Acinetobacter spp. among animals, food, and environment. This complex scenario is responsible for the expansion of these MDR organisms which may have life-threatening clinical significance. Nowadays, the prevalence of food-producing animals carrying ESC-R E. coli and ESC-R Salmonella (especially those producing CTX-M-type ESBLs and the CMY-2 pAmpC) has reached worryingly high values. More recently, the appearance of carbapenem-resistant isolates (i.e., VIM-1-producing Enterobacteriaceae and NDM-1 or OXA-23-producing Acinetobacter spp.) in livestock has even drawn greater concerns. In this review, we describe the aspects related to the spread of the above MDR organisms among pigs, cattle, and poultry, focusing on epidemiology, molecular mechanisms of resistance, impact of antibiotic use, and strategies to contain the overall problem. The link and the impact of ESC-R organisms of livestock origin for the human scenario are also discussed.

Comparable high rates of extended-spectrum-beta-lactamase-producing Escherichia coli in birds of prey from Germany and Mongolia

Frequent contact with human waste and liquid manure from intensive livestock breeding, and the increased loads of antibiotic-resistant bacteria that result, are believed to be responsible for the high carriage rates of ESBL-producing E. coli found in birds of prey (raptors) in Central Europe. To test this hypothesis against the influence of avian migration, we initiated a comparative analysis of faecal samples from wild birds found in Saxony-Anhalt in Germany and the Gobi-Desert in Mongolia, regions of dissimilar human and livestock population characteristics and agricultural practices. We sampled a total of 281 wild birds, mostly raptors with primarily north-to-south migration routes. We determined antimicrobial resistance, focusing on ESBL production, and unravelled the phylogenetic and clonal relatedness of identified ESBL-producing E. coli isolates using multi-locus sequence typing (MLST) and macrorestriction analyses. Surprisingly, the overall carriage rates (approximately 5%) and the proportion of ESBL-producers among E. coli (Germany: 13.8%, Mongolia: 10.8%) were similar in both regions. Whereas bla(CTX-M-1) predominated among German isolates (100%), bla(CTX-M-9) was the most prevalent in Mongolian isolates (75%). We identified sequence types (STs) that are well known in human and veterinary clinical ESBL-producing E. coli (ST12, ST117, ST167, ST648) and observed clonal relatedness between a Mongolian avian ESBL-E. coli (ST167) and a clinical isolate of the same ST that originated in a hospitalised patient in Europe. Our data suggest the influence of avian migratory species in the transmission of ESBL-producing E. coli and challenge the prevailing assumption that reducing human influence alone invariably leads to lower rates of antimicrobial resistance.

Frequent combination of antimicrobial multiresistance and extraintestinal pathogenicity in Escherichia coli isolates from urban rats (Rattus norvegicus) in Berlin, Germany

Urban rats present a global public health concern as they are considered a reservoir and vector of zoonotic pathogens, including Escherichia coli. In view of the increasing emergence of antimicrobial resistant E. coli strains and the on-going discussion about environmental reservoirs, we intended to analyse whether urban rats might be a potential source of putatively zoonotic E. coli combining resistance and virulence. For that, we took fecal samples from 87 brown rats (Rattus norvegicus) and tested at least three E. coli colonies from each animal. Thirty two of these E. coli strains were pre-selected from a total of 211 non-duplicate isolates based on their phenotypic resistance to at least three antimicrobial classes, thus fulfilling the definition of multiresistance. As determined by multilocus sequence typing (MLST), these 32 strains belonged to 24 different sequence types (STs), indicating a high phylogenetic diversity. We identified STs, which frequently occur among extraintestinal pathogenic E. coli (ExPEC), such as STs 95, 131, 70, 428, and 127. Also, the detection of a number of typical virulence genes confirmed that the rats tested carried ExPEC-like strains. In particular, the finding of an Extended-spectrum beta-lactamase (ESBL)-producing strain which belongs to a highly virulent, so far mainly human- and avian-restricted ExPEC lineage (ST95), which expresses a serogroup linked with invasive strains (O18:NM:K1), and finally, which produces an ESBL-type frequently identified among human strains (CTX-M-9), pointed towards the important role, urban rats might play in the transmission of multiresistant and virulent E. coli strains. Indeed, using a chicken infection model, this strain showed a high in vivo pathogenicity. Imagining the high numbers of urban rats living worldwide, the way to the transmission of putatively zoonotic, multiresistant, and virulent strains might not be far ahead. The unforeseeable consequences of such an emerging public health threat need careful consideration in the future.

Multiresistant uropathogenic Escherichia coli from a region in India where urinary tract infections are endemic: genotypic and phenotypic characteristics of sequence type 131 isolates of the CTX-M-15 extended-spectrum-β-lactamase-producing lineage

Escherichia coli sequence type 131 (O25b:H4), associated with the CTX-M-15 extended-spectrum beta-lactamases (ESBLs) and linked predominantly to the community-onset antimicrobial-resistant infections, has globally emerged as a public health concern. However, scant attention is given to the understanding of the molecular epidemiology of these strains in high-burden countries such as India. Of the 100 clinical E. coli isolates obtained by us from a setting where urinary tract infections are endemic, 16 ST131 E. coli isolates were identified by multilocus sequence typing (MLST). Further, genotyping and phenotyping methods were employed to characterize their virulence and drug resistance patterns. All the 16 ST131 isolates harbored the CTX-M-15 gene, and half of them also carried TEM-1; 11 of these were positive for bla(OXA) groups 1 and 12 for aac(6')-Ib-cr. At least 12 isolates were refractory to four non-beta-lactam antibiotics: ciprofloxacin, gentamicin, sulfamethoxazole-trimethoprim, and tetracycline. Nine isolates carried the class 1 integron. Plasmid analysis indicated a large pool of up to six plasmids per strain with a mean of approximately three plasmids. Conjugation and PCR-based replicon typing (PBRT) revealed that the spread of resistance was associated with the FIA incompatibility group of plasmids. Pulsed-field gel electrophoresis (PFGE) and genotyping of the virulence genes showed a low level of diversity among these strains. The association of ESBL-encoding plasmid with virulence was demonstrated in transconjugants by serum assay. None of the 16 ST131 ESBL-producing E. coli strains were known to synthesize carbapenemase enzymes. In conclusion, our study reports a snapshot of the highly virulent/multiresistant clone ST131 of uropathogenic E. coli from India. This study suggests that the ST131 genotypes from this region are clonally evolved and are strongly associated with the CTX-M-15 enzyme, carry a high antibiotic resistance background, and have emerged as an important cause of community-acquired urinary tract infections.

Effect of subinihibitory and inhibitory concentrations of Plectranthus amboinicus (Lour.) Spreng essential oil on Klebsiella pneumoniae

We evaluated the antimicrobial activity and some mechanisms used by subinhibitory and inhibitory concentrations of the essential oil, obtained from leaves of Plectranthus amboinicus, against a standard strain of Klebsiella pneumoniae and 5 multiresistant clinical isolates of the bacteria. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), the rate of kill and the pH sensitivity of the essential oil were determined by microdilution tests performed in 96-well plates. Subinhibitory and inhibitory concentrations of the essential oil were tested in order to check its action on K. pneumoniae membrane permeability, capsule expression, urease activity and cell morphology. The MIC and MBC of the essential oil were 0.09±0.01%. A complete inhibition of the bacterial growth was observed after 2 h of incubation with twice the MIC of the essential oil. A better MIC was found when neutral or alkaline pH broth was used. Alteration in membrane permeability was found by the increase of crystal violet uptake when the bacteria were incubated with twice the MIC levels of the essential oil. The urease activity could be prevented when all the subinhibitory concentrations were tested in comparison to the untreated group (p<0.001). Alteration of the bacterial morphology besides inhibition of the capsule expression was verified by atomic force microscopy, and Anthony's stain method, respectively. Our data allow us to conclude that the essential oil of P. amboinicus can be a good candidate for future research.

Methicillin-resistant staphylococci (MRS) and extended-spectrum beta-lactamases (ESBL)-producing Enterobacteriaceae in companion animals: nosocomial infections as one reason for the rising prevalence of these potential zoonotic pathogens in clinical samples

The ongoing change in the relationship between humans and companion animals is hallmarked by the increasing intensive care provided to companion animals in veterinary medicine, resulting in growing numbers of high-risk animal patients. The emergence of nosocomial infections in small animal clinics is one of the major drawbacks of this development, especially in terms of multidrug-resistance and potentially zoonotic pathogens. This mini-review therefore addresses recent findings regarding the increasing prevalence of multi-resistant bacterial pathogens like methicillin-resistant staphylococci (MRS), including Staphylococcus aureus (MRSA) and Staphylococcus pseudintermedius (MRSP) as well as extended-spectrum beta-lactamases (ESBL)-producing Enterobacteriaceae in companion animals. Along with the steady increase of nosocomial infection rates in veterinary clinics, particular attention has recently been drawn to the genetic background of multi-resistant strains, resulting in the identification of certain genetic lineages which frequently appear in both, human and animal samples. These sequence types (ST), included ST254, ST8 and ST22 in terms of MRSA and ST131, ST405 and ST648 for ESBL-producing E. coli. The interspecies distribution of these STs resulted in the assumption that certain extended-host spectrum genotypes (EHSG) might exist both for MRS and ESBL-producing E. coli. These initial findings underline the necessity to investigate the major molecular or functional driving forces facilitating interspecies transferability of such EHSG strains. Due to the zoonotic potential of these multi-resistant bacteria, another aspect of the changing social role of companion animals needs to be addressed: the close contact of pets with their owners, resulting in presumptive new transmission and infection routes. We therefore envision retaliatory actions like initial surveillance and monitoring programs not only in livestock, but also particularly in companion animals. Interdisciplinary approaches including human and veterinary experts should be implemented to develop reliable investigation procedures with respect to the current reality of animal owners and their pets. Additionally, consequent basic hygienic measures, prudent use of antimicrobials in companion animals and efforts regarding implementation of antibiotic stewardships should be fostered.

Food animals and antimicrobials: impacts on human health

Antimicrobials are valuable therapeutics whose efficacy is seriously compromised by the emergence and spread of antimicrobial resistance. The provision of antibiotics to food animals encompasses a wide variety of nontherapeutic purposes that include growth promotion. The concern over resistance emergence and spread to people by nontherapeutic use of antimicrobials has led to conflicted practices and opinions. Considerable evidence supported the removal of nontherapeutic antimicrobials (NTAs) in Europe, based on the "precautionary principle." Still, concrete scientific evidence of the favorable versus unfavorable consequences of NTAs is not clear to all stakeholders. Substantial data show elevated antibiotic resistance in bacteria associated with animals fed NTAs and their food products. This resistance spreads to other animals and humans-directly by contact and indirectly via the food chain, water, air, and manured and sludge-fertilized soils. Modern genetic techniques are making advances in deciphering the ecological impact of NTAs, but modeling efforts are thwarted by deficits in key knowledge of microbial and antibiotic loads at each stage of the transmission chain. Still, the substantial and expanding volume of evidence reporting animal-to-human spread of resistant bacteria, including that arising from use of NTAs, supports eliminating NTA use in order to reduce the growing environmental load of resistance genes.

Food animals and antimicrobials: impacts on human health

Antimicrobials are valuable therapeutics whose efficacy is seriously compromised by the emergence and spread of antimicrobial resistance. The provision of antibiotics to food animals encompasses a wide variety of nontherapeutic purposes that include growth promotion. The concern over resistance emergence and spread to people by nontherapeutic use of antimicrobials has led to conflicted practices and opinions. Considerable evidence supported the removal of nontherapeutic antimicrobials (NTAs) in Europe, based on the "precautionary principle." Still, concrete scientific evidence of the favorable versus unfavorable consequences of NTAs is not clear to all stakeholders. Substantial data show elevated antibiotic resistance in bacteria associated with animals fed NTAs and their food products. This resistance spreads to other animals and humans-directly by contact and indirectly via the food chain, water, air, and manured and sludge-fertilized soils. Modern genetic techniques are making advances in deciphering the ecological impact of NTAs, but modeling efforts are thwarted by deficits in key knowledge of microbial and antibiotic loads at each stage of the transmission chain. Still, the substantial and expanding volume of evidence reporting animal-to-human spread of resistant bacteria, including that arising from use of NTAs, supports eliminating NTA use in order to reduce the growing environmental load of resistance genes.

Prevalence and mechanisms of quinolone resistance among selected nontyphoid Salmonella isolated from food animals and humans in Korea

The aim of this study was to investigate the prevalence and mechanism of quinolone resistance among selected nontyphoid Salmonella (NTS) isolates. A total of 1279 NTS isolated from food animals (n=692) and humans (n=587) between 1995 and 2009 were investigated by serotyping, antimicrobial susceptibility testing, screening for plasmid-mediated quinolone resistance (PMQR) genes qnr, aac(6')-Ib-cr, and qepA and mutations in the quinolone resistance-determining region (QRDR) of gyrA and parC by PCR, and DNA sequencing. Three hundred thirty (47.7%) of 692 animal isolates and 177 (30.2%) of 587 human isolates were resistant to nalidixic acid. Most animal (94.8%, 313/330) and human (99.4%, 176/177) NTS exhibited decreased ciprofloxacin susceptibility (minimum inhibitory concentration [MIC]: 0.125-2 mg/L). None of them carried qnr or qepA gene. However, aac(6')-Ib was identified in six animal isolates, of which four carried aac(6')-Ib-cr gene. Based on antimicrobial resistance profile, year of isolation, MIC for quinolones and fluoroquinolones, and isolation frequency of serotype, 114 animal and 83 human isolates were tested for QRDR mutations. All contained a single mutation within the QRDR of gyrA at either codon 87 or 83, and 41 of them contained an additional mutation in parC. The most prevalent mutation was Asp87-Tyr (n=107), followed by Asp87-Gly (n=28), Asp87-Asn (n=26), Ser83-Tyr (n=22), and Ser83-Phe (n=14). Point mutations in parC were observed outside the QRDR, which included 40 isolates with Thr57-Ser substitution and 1 Salmonella Typhimurium with a novel Glu51-Lys substitution. In conclusion, a point mutation within the QRDR of gyrA was primarily responsible for quinolone resistance and reduced susceptibility to fluoroquinolones in NTS in Korea. To our knowledge, this is the first report of occurrence of aac(6')-Ib-cr gene among NTS in Korea. The spread of NTS carrying aac(6')-Ib-cr is of serious concern and should be carefully monitored.

Transmission of multiple resistant Salmonella Concord from internationally adopted children to their adoptive families and social environment: proposition of guidelines

Since 2004, an increasing number of multidrug-resistant Salmonella serovar Concord infections have been isolated in Belgium among children adopted from Ethiopia. The patients or their family were interviewed and the isolates were subtyped. Between 2004 and 2009, a total of 39 Salmonella Concord infections were isolated from patients. Thirty-four isolates presented a multidrug resistance including resistance to extended-spectrum cephalosporins. Thirty-six cases involved children and 30 of these were adopted from Ethiopia. One case was due to contact with an adopted child and for the other 5 cases no direct epidemiological link with Ethiopia could be found, although four isolates displayed the same patterns observed on the adoptees’ isolates, strongly suggesting a phylogenetic relationship with the Ethiopian isolates. Our study confirmed the emergence in Europe of S. Concord isolates resistant to third-generation cephalosporin among Ethiopian adoptees. We have demonstrated that transmission (intra- and extra familial) can happen even if the frequency seems to be low. The presence and the transmission of such a multidrug-resistant Salmonella infection constitute a major concern, since such strains could jeopardize classical antibiotic therapy in patients at risk. This study provides useful information for parents adopting children and for their family practitioner.

Emergence of extended-spectrum beta-lactamase (CTX-M-15 and CTX-M-14)-producing nontyphoid Salmonella with reduced susceptibility to ciprofloxacin among food animals and humans in Korea

Twenty of 1,279 nontyphoid Salmonella strains isolated from food animals and humans produced CTX-M-type extended-spectrum β-lactamase. All expressed CTX-M-15, except two which coexpressed CTX-M-14 and TEM-1. Insertion sequence ISEcp1 was identified upstream of bla(CTX-M) genes. The bla(CTX-M-15) and bla(CTX-M-14) genes were disseminated by large conjugative IncFIIs and IncI1-Iγ plasmids, respectively.

Salmonella enterica serotype Virchow associated with human infections in Switzerland: 2004-2009

Background

Salmonellosis is one of the most important foodborne diseases and a major threat to public health. Salmonella serotype Virchow ranks among the top five serovars in Europe.

Method

A total of 153 strains isolated from different patients from 2004 through 2009 in Switzerland were further characterized by (i) assessing phenotypic antibiotic resistance profiles using the disk diffusion method and (ii) by genotyping using pulsed-field gel electrophoresis (PFGE) after macrorestriction with XbaI in order to evaluate strain relationship.

Results

The relative frequency of S. Virchow among other Salmonella serovars varied between 4^th to 8^th rank. The annual incidence ranged from 0.45/100'000 in 2004 to 0.40/100'000 in 2009. A total of 48 strains (32%) were resistant to one to 3 antimicrobials, 54 strains (36%) displayed resistance patterns to more than three antibiotics. No trend was identifiable over the years 2004 to 2009. We found a high prevalence (62%) of nalidixic acid resistant strains, suggesting an equally high rate of decreased fluoroqionolone susceptibility, whereas intermediate resistance to ciprofloxacin was negligible. Two strains were extended spectrum β-lactamase (ESBL) producers. Analysis of PFGE patterns uncovered a predominant cluster (similarity coefficient above 80%) consisting of 104 of the 153 strains.

Conclusion

The worldwide increase of antibiotic resistances in Salmonella is an emerging public health problem. For Switzerland, no clear trend is identifiable over the years 2004 to 2009 for S. Virchow. Antimicrobial susceptibility and resistance profiles varied considerably within this period. Nevertheless, the situation in Switzerland coincided with findings in other European countries. Genotyping results of this strain collection revealed no evidence for an undetected outbreak within this time period.

Increasing trend of resistance to nalidixic acid and emerging ceftriaxone and ciprofloxacin resistance in Salmonella enterica serovar Typhimurium in Slovakia, 2005 to 2009

A 5-year survey from 2005 to 2009 revealed an increasing trend of resistance to nalidixic acid (from 0% in 2005 to 11% in 2009) among 858 clinical isolates of Salmonella Typhimurium. In addition, 10 ceftriaxone-resistant and 3 ciprofloxacin-resistant Salmonella Typhimurium isolates were detected over the period of study.

Antimicrobial resistance ofEscherichia coliandEnterococcus faecalisin housed laying-hen flocks in Europe

The aim of this study was to determine the potential association between housing type and multiple drug resistance (MDR) inEscherichia coliandEnterococcus faecalisisolates recovered from 283 laying-hen flocks. In each flock, a cloacal swab from four hens was collected and produced 1102E. coliand 792E. faecalisisolates. Broth microdilution was used to test susceptibility to antimicrobials. Country and housing type interacted differently with the MDR levels of both species. In theE. colimodel, housing in a raised-floor system was associated with an increased risk of MDR compared to the conventional battery system [odds ratio (OR) 2·12, 95% confidence interval (CI) 1·13–3·97)]. In theE. faecalismodel the MDR levels were lower in free-range systems than in conventional battery cages (OR 0·51, 95% CI 0·27–0·94). In Belgium, ceftiofur-resistantE. coliisolates were more numerous than in the other countries.

Trends in production of extended-spectrum beta-lactamases among Enterobacteriaceae of clinical interest: results of a nationwide survey in Belgian hospitals

OBJECTIVES

to assess the frequency and diversity of extended-spectrum β-lactamases (ESBLs) in Enterobacteriaceae isolates in Belgium.

METHODS

during 2006 and 2008, non-duplicate clinical isolates of Enterobacteriaceae resistant to ceftazidime and/or cefotaxime were collected in 100 Belgian hospitals. ESBL production was confirmed by phenotypic and genotypic tests. MICs of 13 antimicrobial agents were determined by Etest. ESBL-encoding genes were identified by PCR sequencing and the bla(CTX-M) environment was characterized by PCR mapping. Selected isolates were genotyped by PFGE, multilocus sequence typing analysis and phylogenetic grouping by PCR.

RESULTS

overall, 733 isolates were confirmed as ESBL producers. Carbapenems and temocillin were active against ≥ 95% of all tested isolates. Co-resistance to co-trimoxazole and to ciprofloxacin was found in almost 70% and 80% of the strains, respectively. Overall, Escherichia coli (49%), Enterobacter aerogenes (32%) and Klebsiella pneumoniae (9%) represented the most prevalent species. Isolates harboured predominantly TEM-24 (30.7%), CTX-M-15 (24.2%) and TEM-52 (12.1%). Compared with 2006, the proportion of CTX-M-type enzymes increased significantly in 2008 (54% versus 23%; P < 10(-6)), mostly linked to a rising proportion of CTX-M-15-producing E. coli. TEM-24 decreased (19% in 2008 versus 43% in 2006; P < 10(-6)) during the same period, while the prevalence of TEM-52 remained unchanged (10% in 2008 versus 14% in 2006; not significant). Over 80% of the CTX-M-15-producing E. coli isolates clustered into a single PFGE type and phylogroup B2, corresponding to the sequence type (ST) 131 clone. Intra- and inter-species gene dissemination (CTX-M-15, CTX-M-2 and CTX-M-9) and wide epidemic spread of the CTX-M-15-producing E. coli ST131 clone in several Belgian hospitals were observed.

CONCLUSIONS

the rapid emergence of multiresistant CTX-M-15-producing E. coli isolates is of major concern and highlights the need for further surveillance in Belgium.

CTX-M-15-type extended-spectrum beta-lactamases-producing Escherichia coli from wild birds in Germany

The isolation of Escherichia coli from wild birds in Germany revealed the occurrence of four CTX-M-15-producing strains from four different birds (2.3% of 172 isolates). CTX-M producers were recovered from two Eurasian Blackbirds, one Rock Pigeon and a Greater White-fronted Goose. All CTX-M-producing E. coli revealed a clonal relationship as determined by pulsed-field gel electrophoresis (PFGE) and were assigned to multilocus sequence type (ST) 648. Our findings suggest the emergence of a new clone with epidemiological importance and strengthen the role of wild bird species other than waterfowl as possible reservoirs of ESBL-producing Enterobacteriaceae.

Characterization of extended-spectrum beta-lactamases produced by Escherichia coli isolated from hospitalized and nonhospitalized patients: emergence of CTX-M-15-producing strains causing urinary tract infections

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli isolates were obtained from hospitalized and nonhospitalized patients in Belgium between August 2006 and November 2007. The antimicrobial susceptibility of these isolates was determined and their ESBL genes were characterized. Clonal relationships between the CTX-M-producing E. coli isolates causing urinary tract infections were also studied. A total of 90 hospital- and 45 community-acquired cephalosporin-resistant E. coli isolates were obtained. Tetracycline, enrofloxacine, gentamicin, and trimethoprim-sulfamethaxozole resistance rates were significantly different between the community-onset and hospital-acquired isolates. A high diversity of different ESBLs was observed among the hospital-acquired E. coli isolates, whereas CTX-M-15 was dominating among the community-acquired E. coli isolates (n = 28). Thirteen different pulsed-field gel electrophoresis profiles were observed in the community-acquired CTX-M-15-producing E. coli, indicating that multiple clones have acquired the bla(CTX-M-15) gene. All community-acquired CTX-M-15-producing E. coli isolates of phylogroups B2 and D were assigned to the sequence type ST131. The hospital-acquired CTX-M-15-producing E. coli isolates of phylogroups B2, B1, A, and D corresponded to ST131, ST617, ST48, and ST405, respectively. In conclusion, CTX-M-type ESBLs have emerged as the predominant class of ESBLs produced by E. coli isolates in the hospital and community in Belgium. Of particular concern is the predominant presence of the CTX-M-15 enzyme in ST131 community-acquired E. coli.

IncI1 plasmid carrying extended-spectrum-beta-lactamase gene blaCTX-M-1 in Salmonella enterica isolates from poultry and humans in France, 2003 to 2008

We report the dissemination of a conjugative IncI1 plasmid carrying bla(CTX-M-1), conferring resistance to extended-spectrum cephalosporins, in Salmonella enterica isolates from poultry and humans in France from 2003 to 2008. By IncI1 plasmid subtyping, this plasmid was shown to be genetically related to that found in Escherichia coli isolates from healthy poultry in France.

Risk factors for ceftiofur resistance in Escherichia coli from Belgian broilers

A cross-sectional study on 32 different Belgian broiler farms was performed in 2007 and 2008 to identify risk factors for ceftiofur resistance in Escherichia coli. On each farm, one E. coli colony was isolated from 30 random birds. Following susceptibility testing of 14 antimicrobials, an on-farm questionnaire was used to obtain information on risk factors. Using a multilevel logistic regression model two factors were identified at the animal level: resistance to amoxicillin and to trimethoprim-sulfonamide. On the farm level, besides antimicrobial use, seven management factors were found to be associated with the occurrence of ceftiofur resistance in E. coli from broilers: poor hygienic condition of the medicinal treatment reservoir, no acidification of drinking water, more than three feed changes during the production cycle, hatchery of origin, breed, litter material used, and treatment with amoxicillin. This study confirms that not only on-farm antimicrobial therapy, but also management- and hatchery-related factors influence the occurrence of antimicrobial resistance.

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.

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.

Plasmid double locus sequence typing for IncHI2 plasmids, a subtyping scheme for the characterization of IncHI2 plasmids carrying extended-spectrum beta-lactamase and quinolone resistance genes

OBJECTIVES

IncHI2 plasmids are frequently encountered in clinical enterobacterial strains associated with the dissemination of relevant antimicrobial resistance genes. These plasmids are usually >250 kb, and technical difficulties can impair plasmid DNA purification and comparison by restriction fragment length polymorphism. We analysed the available IncHI2 whole DNA plasmid sequences to devise a rapid typing scheme to categorize the members of this plasmid family into homogeneous groups.

METHODS

We compared the available full IncHI2 plasmid sequences, identifying conserved and variable regions within the backbone of this plasmid family, to devise an IncHI2 typing method based on sequence typing and multiplex PCRs. A collection of IncHI2 plasmids carrying extended-spectrum beta-lactamase and quinolone resistance genes, identified in strains from different sources (animals and humans) and geographical origins, was tested by these typing systems.

RESULTS

We devised a plasmid double locus sequence typing (pDLST) scheme and a multiplex PCR discriminating IncHI2 plasmid variants. These systems were tested on a collection of IncHI2 plasmids, demonstrating that the plasmids carrying blaCTX-M-2 and blaCTX-M-9 belonged to two major plasmid variants, which were highly conserved among different enterobacterial species disseminated in several European countries.

CONCLUSIONS

The ability to recognize and subcategorize plasmids by pDLST in homogeneous groups on the basis of their phylogenetic relatedness can be helpful to analyse their distribution in nature and to discover of their evolutionary origin.

Emergence of human pandemic O25:H4-ST131 CTX-M-15 extended-spectrum-beta-lactamase-producing Escherichia coli among companion animals

OBJECTIVES

In view of the intercontinental emergence of Escherichia coli clone O25:H4-ST131 producing CTX-M-15 extended-spectrum beta-lactamase (ESBL) in human clinical settings it would be of great interest to explore its existence in animals to unravel a possible reservoir function and the origin and transmission of this group of multiresistant strains.

METHODS

A total of 177 clinical phenotypically ESBL-producing E. coli isolates, mainly obtained from companion animals with urinary tract infections, wound infections and diarrhoea, were collected in a veterinary diagnostic laboratory covering a European-wide service area. They were screened for molecular subtype O25b and multilocus sequence type 131. O25b-ST131 isolates were subsequently tested for ESBL types, and phenotypic and genotypic resistance determinants. Further characterization of the strains was performed by PFGE and virulence gene typing.

RESULTS

Ten (5.6%) of 177 phenotypically ESBL-producing E. coli isolates, nine strains from dogs and one strain from a horse, were allocated to the B2-O25b-ST131 lineage. Nine of these isolates harboured a CTX-M-15-type beta-lactamase enzyme while one strain possessed an SHV-12-type ESBL. Macrorestriction analysis revealed a cluster formation of six of the animal CTX-M-15-type ESBL-producing strains from five different European countries together with a human control strain constituting a group of clonally related strains at a similarity value of 87.0%.

CONCLUSIONS

Our findings demonstrate that the group of clonally related human B2-O25:H4-ST131 CTX-M-15-type ESBL-producing E. coli strains is present in companion animals from various European countries. This highlights the possibility of inter-species transmission of these multiresistant strains from human to animal and vice versa.

CTX-M-2-producing Salmonella Typhimurium isolated from pediatric patients and poultry in Brazil

Ten Salmonella enterica serovar Typhimurium isolates producing CTX-M-2 extended-spectrum beta-lactamase were identified from clinical and poultry sources in two distant cities in Brazil between 2003 and 2004. They included two isolates from pediatric patients and eight isolates from poultry or its environment. All isolates exhibited coresistance to non-beta-lactam antimicrobials including tetracycline and trimethoprim/sulfamethoxazole. The CTX-M-2 gene was located on transferable plasmids with sizes between 90 and 170 kb that also carried other resistance determinants in some isolates. By pulsed-field gel electrophoresis, the genetic similarity of the isolates including clinical and poultry ones ranged from 89% to 100%.

First report of extended-spectrum-beta-lactamase-producing Salmonella enterica serovar Kentucky isolated from poultry in Ireland

Therapy of invasive human salmonellosis is complicated by increasing antimicrobial resistance. Food animals are the principal source of infection with nontyphoid Salmonella. We report the emergence of broad-spectrum-cephalosporin resistance in Salmonella enterica serovar Kentucky in poultry in Ireland.

Transfer of plasmid-mediated CTX-M-9 from Salmonella enterica serotype Virchow to Enterobacteriaceae in human flora-associated rats treated with cefixime

Food animals are a potential source of CTX-M resistance genes for humans. We evaluated the transfer of the bla(CTX-M-9) gene from an animal strain of Salmonella enterica serotype Virchow to Enterobacteriaceae of the human intestinal flora by using human flora-associated (HFA) rats with and without cefixime treatment. In the absence of antibiotic, no transconjugant enterobacteria were found in the feces of HFA rats. However, the transfer rate was high if Escherichia coli J5 recipient strains were coinoculated orally with Salmonella. S. enterica serotype Virchow persisted in the rat fecal flora both during and after treatment with therapeutic doses of cefixime. The drug did not increase the transfer rate, and E. coli J5 transconjugants were eliminated from the flora before the end of cefixime treatment. No cefixime was recovered in the rat feces. In the presence of recipient strains, the bla(CTX-M-9) resistance gene was transferred from a strain of animal origin to the human intestinal flora, although transconjugant colonization was transient. Antibiotic use enhanced the persistence of donor strains, increasing the resistance gene pool and the risk of its spread.

Impact of therapeutic treatment with beta-lactam on transfer of the bla(CTX-M-9) resistance gene from Salmonella enterica serovar Virchow to Escherichia coli in gnotobiotic rats

The conjugative transfer of the plasmid carrying the bla(CTX-M-9) gene from Salmonella enterica serovar Virchow isolated from a chicken farm to a recipient Escherichia coli strain was evaluated in vitro and in axenic rats inoculated with both strains, with or without selective pressure due to therapeutic doses of cefixime. The transfer of the bla(CTX-M-9) gene of S. enterica serovar Virchow to E. coli was confirmed in vitro, at a low frequency of 5.9 x 10(-8) transconjugants/donors. This transfer rate was higher in gnotobiotic rats and reached approximately 10(-5) transconjugants/donors without selective pressure. This frequency was not affected by the addition of therapeutic doses of cefixime. Thus, estimates of in vitro transfer underestimated potential transfer in the digestive tract, and therapeutic doses of cefixime did not increase the selection for transconjugants.

Prevalence and antimicrobial resistance of Salmonella serovars in conventional and organic chickens from Louisiana retail stores

In this 1-year survey from October 2006 to September 2007, we isolated and characterized 126 Salmonella isolates from conventionally raised (n=141) and organically raised (n=53) chicken carcasses obtained from 27 retail stores in Baton Rouge, Louisiana. Salmonella was isolated from 22% of conventional and from 20.8% of organic chicken samples. Eight Salmonella serovars were identified; predominant ones included Kentucky, Hadar, and Enteritidis. The vast majority of isolates within the same chicken sample possessed the same pulsed-field gel pattern. All Salmonella isolates were susceptible to amikacin, ceftriaxone, and ciprofloxacin; however, decreased susceptibility to quinolones (7.1%) or extended-spectrum cephalosporins (45.2%) was observed. Resistance to multiple antimicrobials (two or more) was found among 52.4% of the Salmonella isolates. Antimicrobial resistance profiles differed greatly among Salmonella serovars and also depended on the type of chicken from which they were recovered. Salmonella Kentucky isolates from organic chicken samples were susceptible to 11 of the antimicrobials tested, whereas those from conventional chickens were only susceptible to 4 antimicrobials. Three Salmonella Kentucky isolates from conventional chickens possessed multidrug resistance phenotype MDR-AmpC. Results of this study provide baseline data on both prevalence and antimicrobial resistance of Salmonella in retail chickens in this region and emphasize the need for implementing effective control measures to reduce Salmonella contamination and the levels of antimicrobial-resistant Salmonella in both conventionally and organically raised poultry products. Further studies involving larger sample sizes over time are needed to better monitor and assess the trend of prevalence and antimicrobial susceptibility among Salmonella serovars in retail chickens.

Survey of the prevalence of Salmonella on commercial broiler farms in the United Kingdom, 2005/06

Between October 2005 and September 2006, all European Union member states were required to carry out standardised surveys of the prevalence of Salmonella in broiler flock holdings to establish baseline data from which to derive national targets for disease reduction. In the uk 382 holdings were sampled, 41 of which were positive for Salmonella, giving an estimated weighted prevalence of 10.7 per cent (95 per cent confidence interval [ci] 8.1 to 13.1 per cent). The serotype most frequently isolated was Salmonella Ohio, with a weighted prevalence of 2.2 per cent (95 per cent ci 1.2 to 3.7 per cent), followed by Salmonella Kedougou at 1.7 per cent (95 per cent ci 0.9 to 3.2 per cent). There were no isolates of Salmonella Enteritidis and only a single isolation of Salmonella Typhimurium (0.2 per cent, 95 per cent ci 0.0 to 1.6 per cent). Of the three other serotypes given top priority by the eu owing to their public health significance, Salmonella Virchow was isolated from one holding, but Salmonella Hadar and Salmonella Infantis were not detected on any of the holdings.