beta-Lactamases responsible for resistance to expanded-spectrum cephalosporins in Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis isolates recovered in South Africa

Carriage of CTX-M type extended spectrum β-lactamases (ESBLs) in gulls across Europe

BACKGROUND

Extended spectrum β-lactamases (ESBLs), a group of enzymes conferring resistance to third generation cephalosporins have rapidly increased in Enterobacteriacae and pose a major challenge to human health care. Resistant isolates are common in domestic animals and clinical settings, but prevalence and genotype distribution varies on a geographical scale. Although ESBL genes are frequently detected in bacteria isolated from wildlife samples, ESBL dissemination of resistant bacteria to the environment is largely unknown. To address this, we used three closely related gull species as a model system and collected more than 3000 faecal samples during breeding times in nine European countries. Samples were screened for ESBL-producing bacteria, which were characterized to the level of ESBL genotype groups (SHV, TEM), or specific genotypes (CTX-M).

RESULTS

ESBL-producing bacteria were frequently detected in gulls (906 of 3158 samples, 28.7 %), with significant variation in prevalence rates between countries. Highest levels were found in Spain (74.8 %), The Netherlands (37.8 %) and England (27.1 %). Denmark and Poland represented the other extreme with no, or very few positive samples. Genotyping of CTX-M isolates identified 13 different variants, with bla CTX-M-1 and bla CTX-M-14 as the most frequently detected. In samples from England, Spain and Portugal, bla CTX-M-14 dominated, while in the rest of the sampled countries bla CTX-M-1 (except Sweden where bla CTX-M-15 was dominant) was the most frequently detected genotype, a pattern similar to what is known from studies of human materials.

CONCLUSIONS

CTX-M type ESBLs are common in the faecal microbiota from gulls across Europe. The gull ESBL genotype distribution was in large similar to published datasets from human and food-production animals in Europe. The data suggests that the environmental dissemination of ESBL is high from anthropogenic sources, and widespread occurrence of resistant bacteria in common migratory bird species utilizing urban and agricultural areas suggests that antibiotic resistance genes may also be spread through birds.

Comparison of Extended-Spectrum β-Lactamase (ESBL) CTX-M Genotypes in Franklin Gulls from Canada and Chile

Migratory birds have been suggested to contribute to long-distance dispersal of antimicrobial resistant bacteria, but tests of this hypothesis are lacking. In this study we determined resistance profiles and genotypes of ESBL-producing bacteria in randomly selected Escherichia coli from Franklin´s gulls (Leucophaeus pipixcan) at breeding sites in Canada and compared with similar data from the gulls' wintering grounds in Chile. Resistant E. coli phenotypes were common, most notably to ampicillin (30.1%) and cefadroxil (15.1%). Furthermore, 17.0% of the gulls in Canada carried ESBL producing bacteria, which is higher than reported from human datasets from the same country. However, compared to gulls sampled in Chile (30.1%) the prevalence of ESBL was much lower. The dominant ESBL variants in Canada were blaCTX-M-14 and blaCTX-M-15 and differed in proportions to the data from Chile. We hypothesize that the observed differences in ESBL variants are more likely linked to recent exposure to bacteria from anthropogenic sources, suggesting high local dissemination of resistant bacteria both at breeding and non-breeding times rather than a significant trans-hemispheric exchange through migrating birds.

Assessment of the Prevalence of Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae in Ready-to-Eat Salads, Fresh-Cut Fruit, and Sprouts from the Swiss Market

Ready-to-eat (RTE) prepacked salads and fruit have been successfully marketed for the last decade in Switzerland and are increasingly important as a component of everyday diets. To determine whether extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae are present in RTE salads, fresh-cut fruit, and sprouts on the Swiss market, samples of 238 mixed and unmixed RTE produce from a large production plant and 23 sprout samples from two sprout farms were analyzed. Further, four samples from the production plant's recycled wash water, which is used for crop irrigation, were analyzed. Twelve (5%) of the 238 RTE products and one of the recycled wash water samples yielded ESBL-producing Enterobacteriaceae. Strain identification and PCR analysis of the blaESBL genes revealed Kluyvera ascorbata isolated from a tomato sample harboring a blaCTX-M-2-like gene; multidrug-resistant (MDR) Enterobacter cloacae detected in a chives sample imported from Spain harboring the clinically important bla(CTX-M-15) gene; and 10 Serratia spp. isolated from mixed salads (bla(FONA-2) and bla(FONA-2)-like genes were found in 6 [60%] and bla(FONA-4)-like and bla(FONA-5)-like genes were each found in 2 [20%] of the isolates). The recycled wash water sample tested positive for one extraintestinal pathogenic MDR Escherichia coli B2:ST131 harboring bla(CTX-M-27) and for one MDR E. coli A:ST88 containing bla(CTX-M-3). None of the sprout samples tested positive for ESBL-producing Enterobacteriaceae. Overall, the majority of the Enterobacteriaceae detected in Swiss RTE produce were environmental strains producing minor ESBLs. The detection of an isolate producing a clinically important ESBL in a single sample and of an international circulating pathogenic strain (B2:ST131) in recycled wash water highlights the importance of surveillance of fresh produce and of recycled wash water that will be reused for irrigation purposes.

Extended-Spectrum β-Lactamase (ESBL)-Producing Klebsiella pneumoniae in Bulk Tank Milk from Dairy Farms in Indonesia

Bulk tank milk from 80 dairy farms located in the West Java Region of Indonesia was analyzed for the presence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. Isolates from seven dairy farms were ESBL positive, and all were identified as Klebsiella pneumoniae. The isolates showed ESBL-characteristic antibiotic resistance patterns. Further analysis revealed that all K. pneumoniae isolates harbored the blaSHV gene, and two isolates were additionally positive for the blaTEM-1 and blaCTX-M-15 genes. Isolates from different farms were clonally diverse according to macrorestriction analysis. The results indicate that the relatively high frequency of ESBL-producing K. pneumoniae in bulk tank milk implies the risk that milk is both a source of local exposure and a vector contributing to the supraregional spread of antibiotic-resistant bacteria by trade.

Extended-spectrum-β-lactamase-producing Enterobacteriaceae isolated from vegetables imported from the Dominican Republic, India, Thailand, and Vietnam

To examine to what extent fresh vegetables imported into Switzerland represent carriers of extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae, 169 samples of different types of fresh vegetables imported into Switzerland from the Dominican Republic, India, Thailand, and Vietnam were analyzed. Overall, 25.4% of the vegetable samples yielded one or more ESBL-producing Enterobacteriaceae, 78.3% of which were multidrug resistant. Sixty isolates were obtained: Escherichia coli, 26; Klebsiella pneumoniae, 26; Enterobacter cloacae, 6; Enterobacter aerogenes, 1; and Cronobacter sakazakii, 1. We found 29 isolates producing CTX-M-15, 8 producing CTX-M-14, 7 producing CTX-M-55, 3 producing CTX-M-65, 1 each producing CTX-M-1, CTX-M-3, CTX-M-27, and CTX-M-63, 5 producing SHV-2, 3 producing SHV-12, and 1 producing SHV-2a. Four of the E. coli isolates belonged to epidemiologically important clones: CTX-M-15-producing B2:ST131 (1 isolate), D:ST405 (1 isolate), and D:ST38 (2 isolates). One of the D:ST38 isolates belonged to the extraintestinal enteroaggregative E. coli (EAEC) D:ST38 lineage. Two of the K. pneumoniae isolates belonged to the epidemic clones sequence type 15 (ST15) and ST147. The occurrence of antibiotic-resistant pathogenic and commensal Enterobacteriaceae in imported agricultural foodstuffs constitutes a source of ESBL genes and a concern for food safety.

Relationship between Antimicrobial Consumption and the Incidence of Antimicrobial Resistance in Escherichia coli and Klebsiella pneumoniae Isolates

INTRODUCTION

Gram negative organisms are one of the major causes of nosocomial diseases. Development of resistance to antibiotics by these organisms increases their risk in clinical treatment of patients. It also affects morbidity and mortality hence needs to be monitored and controlled.

AIM

The aim of the present study was to analyse the correlation between consumption of parenteral antibiotics and the rates of antimicrobial resistance among the Escherichia coli and Klebsiella pneumoniae isolates collected during Dec 2010 - Jun 2013 from JIPMER hospital.

MATERIALS AND METHODS

Consumption data of parenteral antibiotics in J01 category of Anatomical Therapeutic Chemical (ATC) in JIPMER was obtained and expressed in Defined Daily Doses (DDD) per 1000 inhabitants. Valid consumption and resistance data during the period Dec 2010 to Jun 2013 were obtained at 6 month intervals and were correlated to draw a relationship between antimicrobial consumption and its impact on drug resistance for Escherichia coli and Klebsiella pneumoniae.

RESULTS

Escherichia coli isolates showed high resistance for increased use of gentamycin and ciprofloxacin. Increase in antibiotic consumption increases the resistance for Escherichia coli except for amikacin. Among the Klebsiella isolates, meropenem and gentamycin showed high correlations followed by ceftazidime, amikacin, ceftriaxone and ciprofloxacin.

CONCLUSION

In summary, a statistically significant association was noticed between consumption of the studied antimicrobials and resistance of Escherichia coli isolates, except for amikacin and ceftazidime. In the case of Klebsiella pneumoniae, there was a statistically significant association between the resistance rates and consumption of gentamycin, ceftazidime and meropenem. Further, a linear relationship was noted between antimicrobial consumption and resistant isolates of Escherichia coli and Klebsiella pneumoniae, except for Escherichia coli resistance to amikacin.

Antibiotic resistance and genotype of beta-lactamase producing Escherichia coli in nosocomial infections in Cotonou, Benin

Background

Beta lactams are the most commonly used group of antimicrobials worldwide.

The presence of extended-spectrum lactamases (ESBL) affects significantly the treatment of infections due to multidrug resistant strains of gram-negative bacilli. The aim of this study was to characterize the beta-lactamase resistance genes in Escherichia coli isolated from nosocomial infections in Cotonou, Benin.

Methods

Escherichia coli strains were isolated from various biological samples such as urine, pus, vaginal swab, sperm, blood, spinal fluid and catheter. Isolated bacteria were submitted to eleven usual antibiotics, using disc diffusion method according to NCCLS criteria, for resistance analysis. Beta-lactamase production was determined by an acidimetric method with benzylpenicillin. Microbiological characterization of ESBL enzymes was done by double disc synergy test and the resistance genes TEM and SHV were screened by specific PCR.

Results

ESBL phenotype was detected in 29 isolates (35.5%). The most active antibiotic was imipenem (96.4% as susceptibility rate) followed by ceftriaxone (58.3%) and gentamicin (54.8%). High resistance rates were observed with amoxicillin (92.8%), ampicillin (94%) and trimethoprim/sulfamethoxazole (85.7%). The genotype TEM was predominant in ESBL and non ESBL isolates with respectively 72.4% and 80%. SHV-type beta-lactamase genes occurred in 24.1% ESBL strains and in 18.1% of non ESBL isolates.

Conclusion

This study revealed the presence of ESBL producing Eschericiha coli in Cotonou. It demonstrated also high resistance rate to antibiotics commonly used for infections treatment. Continuous monitoring and judicious antibiotic usage are required.

Replicon typing of plasmids carrying bla CTX-M-1 in Enterobacteriaceae of animal, environmental and human origin

OBJECTIVES

The aim of this work was to determine the plasmid replicon profiles of a collection of bla CTX-M-1-positive enterobacterial strains. The isolates originated from chicken in the production pyramid, healthy food-producing animals at slaughter (chicken, calves, and pigs), chicken retail meat, environmental isolates originating from water bodies, and isolates from humans. A selection of IncI and IncN plasmids were characterized by multilocus sequence typing in order to determine their epidemiological relatedness.

METHODS

Transconjugants of 74 bla CTX-M-1-positive isolates were analyzed by PCR-based replicon typing and by PCR-based plasmid multilocus sequence typing.

RESULTS

The incompatibility groups detected among the bla CTX-M-1-harboring plasmids included IncI1, IncN, IncHI1B, IncF, IncFIIS, IncFIB, and IncB/O, with plasmid lineage IncI1/ST3 predominating in isolates from chicken and from humans. Lineage IncN/ST1 was detected mainly in isolates from pigs. For the first time, bla CTX-M-1 genes encoded on IncHI1 plasmids were detected in isolates from cattle and from water bodies.

CONCLUSIONS

This study identifies plasmid lineages that are contributing to the dissemination of bla CTX-M-1 genes in the food chain, the environment, and humans.

Phenotypic and molecular characterization of extended-spectrum beta-lactamase-producing Escherichia coli in Bangladesh

Background

Resistance to cephalosporins in Enterobacteriaceae is mainly due to the production of extended-spectrum beta-lactamase (ESBL). Little is known about ESBL-producing bacteria in Bangladesh. Therefore, the study presents results of phenotypic and molecular characterization of ESBL-producing Escherichia coli from hospitals in Bangladesh.

Methods

A total of 339 E. coli isolated from patients with urinary tract and wound infections attending three different medical hospitals in urban and rural areas of Bangladesh between 2003–2007 were screened for ESBL-production by the double disk diffusion test. Isolates with ESBL-phenotype were further characterized by antibiotic susceptibility testing, PCR and sequencing of different β-lactamase and virulence genes, serotyping, and XbaI-macrorestriction followed by pulsed-field gel electrophoresis (PFGE).

Results

We identified 40 E. coli with ESBL phenotype. These isolates were resistant to ceftriaxone, ceftazidime, cefotaxime, aztreonam, cefepime, and nalidixic acid but remained susceptible to imipenem. All but one isolate were additionally resistant to ciprofloxacin, and 3 isolates were resistant to cefoxitin. ESBL genes of blaCTX-M-1-group were detected in all isolates; blaTEM-type and blaOXA-1-type genes were detected in 33 (82.5%) and 19 (47.5%) isolates, respectively. Virulence genes that are present in diarrhoeagenic E. coli were not found. Class-1 integron was present in 20 (50%) isolates. All the ESBL-producing E. coli isolates harbored plasmids ranging between 1.1 and 120 MDa. PFGE-typing revealed 26 different pulsotypes, but identical pulsotype showed 6 isolates of serotype O25:H4.

Conclusion

The prevalence of multidrug-resistant ESBL-producing E. coli isolates appears to be high and the majority of the isolates were positive for bla_CTX-M. Although there was genetic heterogeneity among isolates, presence of a cluster of isolates belonging to serotype O25:H4 indicates dissemination of the pandemic uropathogenic E. coli clone in Bangladesh.

Vertical transmission of highly similar bla CTX-M-1-harboring IncI1 plasmids in Escherichia coli with different MLST types in the poultry production pyramid

Objectives: The purpose of this study was to characterize sets of extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae collected longitudinally from different flocks of broiler breeders, meconium of 1-day-old broilers from theses breeder flocks, as well as from these broiler flocks before slaughter.

Methods: Five sets of ESBL-producing Escherichia coli were studied by multi-locus sequence typing (MLST), phylogenetic grouping, PCR-based replicon typing and resistance profiling. The bla_CTX-M-1-harboring plasmids of one set (pHV295.1, pHV114.1, and pHV292.1) were fully sequenced and subjected to comparative analysis.

Results: Eleven different MLST sequence types (ST) were identified with ST1056 the predominant one, isolated in all five sets either on the broiler breeder or meconium level. Plasmid sequencing revealed that bla_CTX-M-1 was carried by highly similar IncI1/ST3 plasmids that were 105 076 bp, 110 997 bp, and 117 269 bp in size, respectively.

Conclusions: The fact that genetically similar IncI1/ST3 plasmids were found in ESBL-producing E. coli of different MLST types isolated at the different levels in the broiler production pyramid provides strong evidence for a vertical transmission of these plasmids from a common source (nucleus poultry flocks).

Prevalence of two multidrug-resistant Klebsiella species in an Indian teaching hospital and adjoining community

BACKGROUND

The Gram-negative pathogenic bacteria Klebsiella oxytoca and Klebsiella pneumoniae produce the extended spectrum β-lactamase (ESBL) and cephalosporinase enzymes and are the major causes of hospital acquired (HA) infections and epidemics in non-hygienic communities in the majority of developing countries.

METHODS

The prevalence of multidrug resistance among 445 strains of K. oxytoca and K. pneumoniae isolated from clinical samples of patients with gastrointestinal infections over a period of 42 months in the hospital was recorded, along with the sensitivity patterns to 23 antibiotics, including third-generation cephalosporin and fluoroquinolone antibiotics, using the disk-diffusion method.

RESULTS

Of 175 K. oxytoca isolates, 143 were ESBL positive and 117 were fluoroquinolone resistant. Of 270 K. pneumoniae isolates, 200 were ESBL positive and 195 were independently fluoroquinolone resistant. The HA samples yielded more isolates than the community acquired (CA) samples for each species. The K. oxytoca strains were resistant to cefepime, gatifloxacin, ciprofloxacin, ceftazidime, levofloxacin and imipenem, whereas the K. pneumoniae strains were highly resistant to ampicillin, norfloxacin, ciprofloxacin, gatifloxacin, ofloxacin, amoxyclav, ceftazidime, cefepime, cefixime, piperacillin and imipenem. The ESBL-producing and fluoroquinolone-resistant K. pneumoniae strains were more prevalent than the K. oxytoca strains in the HA/CA samples. The minimum inhibitory concentration values of the third-generation cephalosporins: cefotaxime and ceftazidime and the fluoroquinolones: ciprofloxacin and levofloxacin against both species of Klebsiella confirmed the resistance in the current/coveted treatment options.

CONCLUSIONS

Patients with other bacterial infections had a relatively higher probability of infection with ESBL-producing and fluoroquinolone-resistant Klebsiella strains. The data presented here highlight the alarming state of Klebsiella infection dynamics in the hospital and adjoining communities.

Characterization and comparison of extended-spectrum β-lactamase (ESBL) resistance genotypes and population structure of Escherichia coli isolated from Franklin's gulls (Leucophaeus pipixcan) and humans in Chile

We investigated the general level of antibiotic resistance with further analysis of extended-spectrum beta-lactamase (ESBL) prevalence, as well as the population structure of E. coli in fecal flora of humans and Franklin’s gulls (Leucophaeus pipixcan) in central parts of Chile. We found a surprisingly high carriage rate of ESBL-producing E. coli among the gulls 112/372 (30.1%) as compared to the human population 6/49 (12.2%.) Several of the E. coli sequence types (STs) identified in birds have previously been reported as Multi Drug Resistant (MDR) human pathogens including the ability to produce ESBLs. This means that not only commensal flora is shared between birds and humans but also STs with pathogenic potential. Given the migratory behavior of Franklin’s gulls, they and other migratory species, may be a part of ESBL dissemination in the environment and over great geographic distances. Apart from keeping the antibiotic use low, breaking the transmission chains between the environment and humans must be a priority to hinder the dissemination of resistance.

Characteristics of enteroaggregative Escherichia coli isolated from healthy carriers and from patients with diarrhoea

The aim of this study was to compare the virulence characteristics and phylogenetic features of enteroaggregative Escherichia coli (EAEC) strains from adults with and without diarrhoea and to search for associations between the analysed genes and carrier or diarrhoeagenic strains, respectively. Faecal samples of 487 healthy humans were screened for EAEC strains and compared with isolates from diarrhoeal patients. Virulence and virulence-associated gene typing, serotyping, multilocus sequence typing and antibiotic susceptibility testing were performed for characterization of the isolates. Characteristics significantly linked to carrier strains or to diarrhoeagenic strains were determined. From 487 stool samples, 24 EAEC strains were obtained. Comparison with strains originating from diseased persons showed a statistically significant association of the genes sat (P = 0.002) and agg3C (P = 0.0139) with the carrier strains, and of pCVD432 (P = 0.0001), aap (P = 0.003), aggR (P = 0.0048) and air (P = 0.031) with the diarrhoeagenic strains. Our study indicates that a certain subset of EAEC is unrelated to diarrhoea, for which sat and agg3C may be markers. Our results further suggest that diarrhoeagenic EAEC strains are distinguishable from carrier strains and suggest that, in addition to well-established markers such as pCVD432 and aggR, aap and air may be useful additional markers to define EAEC as an aetiological agent of diarrhoea in adults.

Detection of new SHV-12, SHV-5 and SHV-2a variants of extended spectrum beta-lactamase in Klebsiella pneumoniae in Egypt

Background

Klebsiella pneumoniae outbreaks possessing extended-spectrum β-lactamase- (ESBL) mediated resistance to third-generation cephalosporins have increased significantly in hospital and community settings worldwide. The study objective was to characterize prevalent genetic determinants of TEM, SHV and CTX-M types ESBL activity in K. pneumoniae isolates from Egypt.

Methods

Sixty five ESBL-producing K. pneumoniae strains, isolated from nosocomial and community-acquired infections from 10 Egyptian University hospitals (2000–2003), were confirmed with double disc-synergy method and E-test. blaTEM, blaSHV and blaCTX-m genes were identified by PCR and DNA sequencing. Pulsed-field gel electrophoresis (PFGE) was conducted for genotyping.

Results

All isolates displayed ceftazidime and cefotaxime resistance. blaTEM and blaSHV genes were detected in 98% of the isolates’ genomes, while 11% carried blaCTX-m. DNA sequencing revealed plasmid-borne SHV-12,-5,-2a (17%), CTX-m-15 (11%), and TEM-1 (10%) prevalence. Among SHV-12 (n=8), one isolate displayed 100% blaSHV-12 amino acid identity, while others had various point mutations: T17G (Leu to Arg, position 6 of the enzyme: n=2); A8T and A10G (Tyr and Ile to Phe and Val, positions 3 and 4, respectively: n=4), and; A703G (Lys to Glu 235: n=1). SHV-5 and SHV-2a variants were identified in three isolates: T17G (n=1); A703G and G705A (Ser and Lys to Gly and Glu: n=1); multiple mutations at A8T, A10G, T17G, A703G and G705A (n=1). Remarkably, 57% of community-acquired isolates carried CTX-m-15. PFGE demonstrated four distinct genetic clusters, grouping strains of different genetic backgrounds.

Conclusions

This is the first study demonstrating the occurrence of SHV-12, SHV-5 and SHV-2a variants in Egypt, indicating the spread of class A ESBL in K. pneumoniae through different mechanisms.

Detection of antibiotic resistant enterococci and Escherichia coli in free range Iberian Lynx (Lynx pardinus)

Thirty fecal samples from wild specimens of Iberian lynx were collected and analyzed for Enterococcus spp. (27 isolates) and Escherichia coli (18 isolates) recovery. The 45 isolates obtained were tested for antimicrobial resistance, molecular mechanisms of resistance, and presence of virulence genes. Among the enterococci, Enterococcus faecium and Enterococcus hirae were the most prevalent species (11 isolates each), followed by Enterococcus faecalis (5 isolates). High percentages of resistance to tetracycline and erythromycin (33% and 30%, respectively) were detected among enterococcal isolates. The tet(M) and/or tet(L), erm(B), aac(6')-Ie-aph(2″)-Ia, ant(6)-Ia, or aph(3')-IIIa genes were detected among resistant enterococci. Virulence genes were detected in one E. faecalis isolate (cpd, cylB, and cylL) and one E. hirae isolate (cylL). High percentages of resistance were detected in E. coli isolates to tetracycline (33%), streptomycin (28%), nalidixic acid (28%), and sulfamethoxazole-trimethoprim (SXT, 22%). Additionally, the blaTEM, tet(A), aadA, cmlA, and different combinations of sul genes were detected among most ampicillin, tetracycline, streptomycin, chloramphenicol and SXT-resistant isolates, respectively. Two isolates contained a class 1 integron with the gene cassette arrays dfrA1 + aadA1 and dfrA12 + aadA2. The E. coli isolates were ascribed to phylo-groups A (n=5); B1 (n=4); B2 (n=6), and D (n=3), with the virulence gene fimA present in all E. coli isolates. This study found resistance genes in wild specimens of Iberian lynx. Thus, it is important to notice that multiresistant bacteria have reached species as rare and completely non-synanthropic as the Iberian lynx. Furthermore, the susceptibility of this endangered species to bacterial infection may be affected by the presence of these virulence and resistance genes.

Characterization of Salmonella enterica subsp. enterica serovar 4,[5],12:i:- clones isolated from human and other sources in Switzerland between 2007 and 2011

Salmonella enterica subsp. enterica serovar 4,[5],12:i:- is a monophasic variant of Salmonella Typhimurium. In this study, a total of 651 human and 107 food and environmental isolates of serovar 4,[5],12:i:- recovered from 2007 through 2011 in Switzerland were characterized by antibiotic resistance profiles and pulsed-field gel electrophoresis (PFGE). In addition, a selection of isolates belonging to the most frequent PFGE patterns was further subjected to multilocus variable-number tandem-repeat analysis (MLVA) and phage typing. Over the years 2007-2011, the reports of salmonellosis caused by Salmonella enterica serovar 4,[5],12:i:- significantly increased. A high prevalence of multidrug-resistant isolates, mainly showing an ampicillin-streptomycin-sulfonamide-tetracycline resistance pattern (ASSuT), was observed. In addition, four extended spectrum beta lactamase (ESBL) (CTX-M-55)-producing isolates were found. XbaI PFGE analysis of all isolates revealed over 150 different pulsotypes, and generally showed a considerable diversity within the monophasic isolates. Nevertheless, among these we identified seven dominant profiles, which encompassed 66% of all isolates tested. The PFGE type STYMXB.0131 dominated among human as well as food isolates. Multilocus variable-number tandem-repeat analysis profile 3-12-10-0-0211, which, in many cases, coincided with PFGE type STYMXB.0131 and phage type DT193 were the most prevalent types found for the isolates further characterized by these typing methods. Our data provide strong evidence for a spread of two specific Salmonella serovar 4,[5],12:i:- clones (PFGE pattern STYMXB.0131, resistance type ASSuT) and (PFGE pattern STYMXB.0131, resistance type SSuT). In contrast to the human isolates, the pork/poultry isolates expressed predominantly the SSuT resistance type.

Synergistic effect between colistin and bacteriocins in controlling Gram-negative pathogens and their potential to reduce antibiotic toxicity in mammalian epithelial cells

Pathogens resistant to most conventional antibiotics are a harbinger of the need to discover novel antimicrobials and anti-infective agents and develop innovative strategies to combat them. The aim of this study was to assess the in vitro activity of colistin alone or in combination with two bacteriocins, nisin A and pediocin PA-1/AcH, against Salmonella choleraesuis ATCC 14028, Pseudomonas aeruginosa ATCC 27853, Yersinia enterocolitica ATCC 9610, and Escherichia coli ATCC 35150 (O157:H7). The strain most sensitive to colistin was enterohemorrhagic E. coli O157:H7, which was inhibited at a concentration of about 0.12 μg/ml. When nisin A (1.70 μg/ml) or pediocin PA-1/AcH (1.56 μg/ml) was combined with colistin, the concentrations required to inhibit E. coli O157:H7 were 0.01 and 0.03 μg/ml, respectively. The in vitro antigenotoxic effect of colistin was determined by using the comet assay method to measure the level of DNA damage in freshly isolated human peripheral blood leukocytes (PBLs) incubated with colistin for 1 h at 37°C. Changes in the tail extents of PBLs of about 69.29 ± 0.08 μm were observed at a final colistin concentration of about 550 ng/ml. Besides the synergistic effect, the combination of colistin (1 mg/ml) and nisin (2 mg/ml) permitted us to re-evaluate the toxic effect of colistin on Vero (monkey kidney epithelial) cells.

Characteristics of extended-spectrum β-lactamase- and carbapenemase-producing Enterobacteriaceae Isolates from rivers and lakes in Switzerland

One of the currently most relevant resistance mechanisms in Enterobacteriaceae is the production of enzymes that lead to modern expanded-spectrum cephalosporin and even carbapenem resistance, mainly extended-spectrum β-lactamases (ESBLs) and carbapenemases. A worrisome aspect is the spread of ESBL and carbapenemase producers into the environment. The aim of the present study was to assess the occurrence of ESBL- and carbapenemase-producing Enterobacteriaceae and to further characterize ESBL- and carbapenemase-producing Enterobacteriaceae in rivers and lakes in Switzerland. ESBL-producing Enterobacteriaceae were detected in 21 (36.2%) of the 58 bodies of water sampled. One river sample tested positive for a carbapenemase-producing Klebsiella pneumoniae subsp. pneumoniae strain. Seventy-four individual strains expressing an ESBL phenotype were isolated. Species identification revealed 60 Escherichia coli strains, seven Klebsiella pneumoniae subsp. pneumoniae strains, five Raoultella planticola strains, one Enterobacter cloacae strain, and one Enterobacter amnigenus strain. Three strains were identified as SHV-12 ESBL producers, and 71 strains carried genes encoding CTX-M ESBLs. Of the 71 strains with CTX-M ESBL genes, 8 isolates expressed CTX-M-1, three produced CTX-M-3, 46 produced CTX-M-15, three produced CTX-M-55, one produced CTX-M-79, six produced CTX-M-14, and four produced CTX-M-27. Three of the four CTX-M-27 producers belonged to the multiresistant pandemic sequence type E. coli B2:ST131 that is strongly associated with potentially severe infections in humans and animals.

International dissemination of Escherichia coli strains with discrepant behaviour in phenotypic antimicrobial susceptibility tests

Preventing the dissemination of antimicrobial resistance depends on appropriate antibiotic stewardship and accurate antimicrobial susceptibility testing (AST). We report the international dissemination of Escherichia coli strains, showing discrepancies between reference methods when phenotypically tested for susceptibility to piperacillin/tazobactam (TZP). We demonstrate that these related strains are predisposed to problematic TZP AST interpretations.

High prevalence of antimicrobial-resistant Escherichia coli from animals at slaughter: a food safety risk

BACKGROUND

There has been concern about the increase of antimicrobial resistant bacteria and protection of animal and public health, along with food safety. In the present study, we evaluate the incidence of antimicrobial resistance among 192 strains of Escherichia coli isolated from faecal samples of healthy food-producing animals at slaughter in Portugal.

RESULTS

Ninety-seven % of the pig isolates, 74% from sheep and 55% from cattle were resistant to one or more antimicrobial agents, with the resistances to ampicillin, streptomycin, tetracycline and trimethoprim-sulfamethoxazole the most common phenotype detected. Genes encoding resistance to antimicrobial agents were detected in most of the resistant isolates. Ninety-three % of the resistant isolates were included in the A or B1 phylogenetic groups, and the virulence gene fimA (alone or in association with papC or aer genes) was detected in 137 of the resistant isolates. Five isolates from pigs belonging to phylogroup B2 and D were resistant to five different antimicrobial agents.

CONCLUSION

Our data shows a high percentage of antibiotic resistance in E. coli isolates from food animals, and raises important questions in the potential impact of antibiotic use in animals and the possible transmission of resistant bacteria to humans through the food chain.

ESBL-producing uropathogenic Escherichia coli isolated from dogs and cats in Switzerland

Extended-spectrum β-lactamase (ESBL)-producing Escherichia (E.) coli have emerged in human and veterinary medicine. The aim of this study was to investigate the presence of ESBL-producers among uropathogenic E. coli isolated from dogs and cats and to characterize detected ESBL-producing isolates by antibiotic susceptibility testing, identification of ESBL genes, multi-locus sequence typing (MLST), detection of putative virulence genes, and analysis of E. coli phylogroups. Among the 107 E. coli isolates derived from urinary samples (59 from dogs, 40 from cats), eight isolates from four different animals (two dogs, two cats) were found to be ESBL-producers. These isolates were of ST533/CTX-M-15/TEM/phylogroup B1 (four strains from one dog), ST410/CTX-M-15/TEM/phylogroup A (three strains, one from a dog and two from a cat), and ST648/CTX-M-15/phylogroup D (one strain from a cat). In terms of putative virulence factors, all isolates harbored lpfA, sat, and tsh, whereas iss was only detected in strains of ST533. Thus, ESBL-producers were detected among uropathogenic E. coli from Swiss companion animals and the eight CTX-M-15-producing isolates belonged to three sequence types (ST410, ST533, ST648) and three E. coli phylogroups (A, B1, D). For the first time, E. coli of ST533 carrying bla(CTX-M-15) were thereby detected in a dog.

Occurrence and characterization of multidrug-resistant New Delhi metallo-β-lactamase-1-producing bacteria isolated between 2003 and 2010 in Bangladesh

The purpose of this study was to screen for reduced susceptibility against imipenem and the presence of the New Delhi metallo-β-lactamase-1 (NDM-1) gene in a collection of Enterobacteriaceae (Escherichia coli, Shigella spp. and Klebsiella pneumoniae) from different surveillance studies between 2003 and 2010 at the International Centre for Diarrhoeal Disease Research, Bangladesh. None of the E. coli (n = 1789) and Shigella spp. (n = 90) isolated between 2009 and 2010 from stool samples was resistant or had intermediate susceptibility to imipenem. Among 127 extended-spectrum β-lactamase-producing strains isolated during 2003-2009, three Klebsiella pneumoniae isolates (2.4 %) were resistant to imipenem and were positive for bla(NDM-1). All these NDM-1-producing strains were isolated in 2008 and were resistant to all antibiotics tested except for tigecycline and colistin. All three isolates were positive for bla(OXA-1) group, bla(CTX-M-1) group (bla(CTX-M-15)) and bla(SHV) genes, whilst two isolates were positive for 16S rRNA methylase (armA) and qnr (qnrB) genes. One isolate was positive for the bla(CMY) gene and one for the rmtB gene. The bla(NDM-1) gene was located on a conjugative plasmid of ~23-24 MDa. The PFGE patterns of the isolates were different from each other. This study highlights the occurrence of NDM-1-producing organisms in Bangladesh in 2008. The clonal diversity of the isolates and the transferability of bla(NDM-1) plasmids suggest a wider distribution of NDM-1-producing bacteria in Bangladesh.

Analysis of β-lactamase phenotypes and carriage of selected β-lactamase genes among Escherichia coli strains obtained from Kenyan patients during an 18-year period

Background

Although β-lactam antibiotics are heavily used in many developing countries, the diversity of β-lactamase genes (bla) is poorly understood. We screened for major β-lactamase phenotypes and diversity of bla genes among 912 E. coli strains isolated from clinical samples obtained between 1992 and 2010 from hospitalized and non-hospitalized patients.

Results

None of the isolates was resistant to carbapenems but 30% of all isolates were susceptible to cefepime, cephamycins and piperacillin-tazobactam. Narrow spectrum β-lactamase (NSBL) phenotype was observed in 278 (30%) isolates that contained bla_TEM-1 (54%) or bla_SHV-1 (35%) or both (11%). Extended Spectrum β-lactamase (ESBL) phenotype was detected in 247 (27%) isolates which carried bla_CTX-M-14 (29%), bla_CTX-M-15 (24%), bla_CTX-M-9 (2%), bla_CTX-M-8 (4%), bla_CTX-M-3 (11%), bla_CTX-M-1 (6%), bla_SHV-5 (3%), bla_SHV-12 (5%), and bla_TEM-52 (16%). Complex Mutant TEM-like (CMT) phenotype was detected in 220 (24%) isolates which carried bla_TEM-125 (29%), while bla_TEM-50, bla_TEM-78, bla_TEM-109, bla_{TEM −152} and bla_TEM-158 were detected in lower frequencies of between 7% and 11%. Majority of isolates producing a combination of CTX-M-15 + OXA-1 + TEM-1 exhibited resistance phenotypes barely indistinguishable from those of CMT-producers. Although 73 (8%) isolates exhibited Inhibitor Resistant TEM-like (IRT) phenotype, bla_TEM-103 was the only true IRT-encoding gene identified in 18 (25%) of strains with this phenotype while the rest produced a combination of TEM-1 + OXA-1. The pAmpCs-like phenotype was observed in 94 (10%) isolates of which 77 (82%) carried bla_CMY-2 while 18% contained bla_CMY-1.

Isolates from urine accounted for 53%, 53%, 74% and 72% of strains exhibiting complex phenotypes such as IRT, ESBL, CMT or pAmpC respectively. On the contrary, 55% isolates from stool exhibited the relatively more susceptible NSBL-like phenotype. All the phenotypes, and majority of the bla genes, were detected both in isolates from hospitalized and non-hospitalized patients but complex phenotypes were particularly common among strains obtained between 2000 and 2010 from urine of hospitalized patients.

Conclusions

The phenotypes and diversity of bla genes in E. coli strains implicated in clinical infections in non-hospitalized and hospitalized patients in Kenya is worryingly high. In order to preserve the efficacy of β-lactam antibiotics, culture and susceptibility data should guide therapy and surveillance studies for β-lactamase-producers in developing countries should be launched.

In vitro activity of mastoparan-AF alone and in combination with clinically used antibiotics against multiple-antibiotic-resistant Escherichia coli isolates from animals

The in vitro activity of mastoparan-AF, an amphipathic antimicrobial peptide isolated from the hornet venom of Vespa affinis, alone and in combination with various clinically used antibiotics, was investigated against 21 Escherichia coli isolates/strains. Most E. coli isolates tested were detected containing multiple-antimicrobial resistance genes. Antimicrobial activity of mastoparan-AF was measured by MIC, MBC, time-kill kinetic assay and chequerboard titration method. Mastoparan-AF exhibited potent antimicrobial activity against most multiple-antibiotic-resistant E. coli isolates at the concentrations ranging from 4 to 16 μg/ml. Combination studies showed that mastoparan-AF acts synergistically with certain antibiotics, i.e., cephalothin or gentamicin, against some multiple-antibiotic-resistant E. coli isolates. In conclusion, mastoparan-AF alone or in combination with other antibiotics could be promising as alternatives for combating multiple-antibiotic-resistant E. coli in future clinical applications.

Occurrence and characteristics of extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae in food producing animals, minced meat and raw milk

Background

The impact of food animals as a possible reservoir for extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae, and the dissemination of such strains into the food production chain need to be assessed. In this study 334 fecal samples from pigs, cattle, chicken and sheep were investigated at slaughter. Additionally, 100 raw milk samples, representing bulk tank milk of 100 different dairy farms, 104 minced meat (pork and beef) samples and 67 E. coli isolates from cattle E. coli mastitis were analyzed.

Results

As many as 15.3% of the porcine, 13.7% of the bovine, 8.6% of the sheep and 63.4% of the chicken fecal samples yielded ESBL producers after an enrichment step. In contrast, none of the minced meat, none of the bulk tank milk samples and only one of the mastitis milk samples contained ESBL producing strains. Of the total of 91 isolates, 89 were E. coli, one was Citrobacter youngae and one was Enterobacter cloacae. PCR analysis revealed that 78 isolates (85.7%) produced CTX-M group 1 ESBLs while six isolates (6.6%) produced CTX-M group 9 enzymes. Five detected ESBLs (5.5%) belonged to the SHV group and 2 isolates (2.2%) contained a TEM-type enzyme. A total of 27 CTX-M producers were additionally PCR-positive for TEM-beta-lactamase. The ESBL-encoding genes of 53 isolates were sequenced of which 34 produced CTX-M-1, 6 produced CTX-M-14, 5 produced CTX-M-15 and also 5 produced SHV-12. Two isolates produced TEM-52 and one isolate expressed a novel CTX-M group 1 ESBL, CTX-M-117. One isolate--aside from a CTX-M ESBL-- contained an additional novel TEM-type broad-spectrum beta-lactamase, TEM-186.

Conclusions

The relatively high rates of ESBL producers in food animals and the high genetic diversity among these isolates are worrisome and indicate an established reservoir in farm animals.

Human-associated extended-spectrum β-lactamase in the Antarctic

Escherichia coli bacteria with extended-spectrum β-lactamase (ESBL) type CTX-M resistance were isolated from water samples collected close to research stations in Antarctica. The isolates had bla(CTX-M-1) and bla(CTX-M-15) genotypes and sequence types (ST) indicative of a human-associated origin. This is the first record of ESBL-producing enterobacteria from Antarctica.

Molecular identification of extended-spectrum-β-lactamase genes from Enterobacteriaceae isolated from healthy human carriers in Switzerland

In this study, fecal samples from 586 healthy humans were investigated to determine the occurrence of extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae in Swiss people. A total of 5.8% of the human fecal samples yielded ESBL producers, and all of the 34 isolated strains were Escherichia coli. PCR analysis revealed that 14 strains produced CTX-M-15, 10 produced CTX-M-1, 7 strains produced CTX-M-14, and 2 strains produced CTX-M-2 ESBLs. One strain produced SHV-12 ESBL. Of the 34 isolates, 15 produced additional TEM-1 broad-spectrum β-lactamases. By serotyping, a high degree of diversity among the strains was found.

Prevalence of plasmid-mediated quinolone resistance genes in uropathogenic Escherichia coli isolated in a teaching hospital of northern Italy

A retrospective study was conducted to determine the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants in uropathogenic Escherichia coli isolated from inpatients and outpatients in a teaching hospital of northern Italy. The presence of qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA was evaluated in 76 and 72 nalidixic acid-resistant E. coli, isolated in 2004 and 2006, respectively. Positivity for the aac(6')-Ib-cr gene was demonstrated in 3 of 76 (3.9%) and 8 of 72 (11%) isolates, respectively; no other PMQR determinant was found. All aac(6')-Ib-cr-positive strains also showed two point mutations in the gyrA and parC genes. Most aac(6')-Ib-cr-positive isolates demonstrated the contemporary presence of bla(CTX-M-15), bla(OXA-1/30), and bla(TEM-1) genes and 4/11 harbored a class 1 integron with a dfrA17-aadA5 gene cassette arrangement. Interestingly, all aac(6')-Ib-cr-positive isolates belonged to B2 phylogenetic group, O25b antigen type, multi locus sequence type 131, and to a cluster of approximately 70% similarity level by pulsed-field gel electrophoresis (PFGE). These findings suggest the circulation of the previously described intercontinentally spreading E. coli O25:H4-ST131 clone in our geographical area since 2004. Hybridization studies of the PFGE profiles showed the aac(6')-Ib-cr gene to be associated with different molecular weight bands (40-350 kb) and interestingly aac(6')-Ib-cr chromosomal integration was demonstrated in one strain by I-Ceu I method. This represents the first report to investigate the presence and diffusion of PMQR determinants in northern Italy and to describe aac(6')-Ib-cr chromosomal integration in E. coli.

Fecal carriage of extended-spectrum β-lactamase-producing Enterobacteriaceae in swine and cattle at slaughter in Switzerland

During the past decade, extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have become a matter of great concern in human medicine. ESBL-producing strains are found in the community, not just in hospital-associated patients, which raises a question about possible reservoirs. Recent studies describe the occurrence of ESBL-producing Enterobacteriaceae in meat, fish, and raw milk; therefore, the impact of food animals as reservoirs for and disseminators of such strains into the food production chain must be assessed. In this pilot study, fecal samples of 59 pigs and 64 cattle were investigated to determine the occurrence of ESBL-producing Enterobacteriaceae in farm animals at slaughter in Switzerland. Presumptive-positive colonies on Brilliance ESBL agar were subjected to identification and antibiotic susceptibility testing including the disc diffusion method and E-test ESBL strips. As many as 15.2% of the porcine and 17.1% of the bovine samples, predominantly from calves, yielded ESBL producers. Of the 21 isolated strains, 20 were Escherichia coli, and one was Citrobacter youngae. PCR analysis revealed that 18 strains including C. youngae produced CTX-M group 1 ESBLs, and three strains carried genes encoding for CTX-M group 9 enzymes. In addition, eight isolates were PCR positive for TEM β-lactamase, but no bla(SHV) genes were detected. Pulsed-field gel electrophoresis showed a high genetic diversity within the strains. The relatively high rates of occurrence of ESBLproducing strains in food animals and the high genetic diversity among these strains indicate that there is an established reservoir of these organisms in farm animals. Further studies are necessary to assess future trends.

Antimicrobial resistance in equine faecal Escherichia coli isolates from North West England

Background

Escherichia coli isolates of equine faecal origin were investigated for antibiotic resistance, resistance genes and their ability to perform horizontal transfer.

Methods

In total, 264 faecal samples were collected from 138 horses in hospital and community livery premises in northwest England, yielding 296 resistant E. coli isolates. Isolates were tested for susceptibility to antimicrobial drugs by disc diffusion and agar dilution methods in order to determine minimum inhibitory concentrations (MIC). PCR amplification was used to detect genes conferring resistance to: ampicillin (TEM and SHV beta-lactamase), chloramphenicol (catI, catII, catIII and cml), tetracycline (tetA, tetB, tetC, tetD, tet E and tetG), and trimethoprim (dfrA1, dfrA9, dfrA12, dfrA13, dfr7, and dfr17).

Results

The proportion of antibiotic resistant isolates, and multidrug resistant isolates (MDR) was significantly higher in hospital samples compared to livery samples (MDR: 48% of hospital isolates; 12% of livery isolates, p < 0.001). Resistance to ciprofloxacin and florfenicol were identified mostly within the MDR phenotypes. Resistance genes included dfr, TEM beta-lactamase, tet and cat, conferring resistance to trimethoprim, ampicillin, tetracycline and chloramphenicol, respectively. Within each antimicrobial resistance group, these genes occurred at frequencies of 93% (260/279), 91%, 86.8% and 73.5%, respectively; with 115/296 (38.8%) found to be MDR isolates. Conjugation experiments were performed on selected isolates and MDR phenotypes were readily transferred.

Conclusions

Our findings demonstrate that E. coli of equine faecal origin are commonly resistant to antibiotics used in human and veterinary medicine. Furthermore, our results suggest that most antibiotic resistance observed in equine E. coli is encoded by well-known and well-characterized resistant genes common to E. coli from man and domestic animals. These data support the ongoing concern about antimicrobial resistance, MDR, antimicrobial use in veterinary medicine and the zoonotic risk that horses could potentially pose to public health.

Antimicrobial resistance and phylogenetic groups in isolates of Escherichia coli from seagulls at the Berlengas nature reserve

Fifty-three faecal samples from yellow-legged gulls (Larus cachinnans) at the Berlengas nature reserve in Portugal were cultured on Levine agar plates not supplemented with antimicrobial agents, and one Escherichia coli colony was isolated and identified from each sample. The percentages of resistant isolates for each of the drugs were ampicillin (43.4 per cent), tetracycline (39.6 per cent), nalidixic acid (34.0 per cent), streptomycin (32.1 per cent), trimethoprim-sulfamethoxazole (SXT) (26.4 per cent), ciprofloxacin (18.9 per cent), chloramphenicol (18.9 per cent), gentamicin (7.5 per cent), tobramycin (7.5 per cent) amikacin (5.7 per cent) and amoxicillin-clavulanic acid (1.9 per cent). All the isolates were susceptible to cefoxitin, ceftazidime, cefotaxime, aztreonam and imipenem. The following resistance genes were detected: bla(TEM) (17 of 23 ampicillin-resistant isolates), tet(A) and/or tet(B) (18 of 21 tetracycline-resistant isolates), aadA (12 of 17 streptomycin-resistant isolates), cmlA (all chloramphenicol-resistant isolates), aac(3)-II with or without aac(3)-IV (all four gentamicin-resistant isolates), and sul1 and/or sul2 and/or sul3 (all 14 SXT-resistant isolates). The intI1 gene was detected in 10 of 14 SXT-resistant isolates, and three of them also contained class 2 integrons; four different gene cassette arrangements were identified among class 1 integrons (aadA, dfrA1+aadA1, dfrA12+orfF+aadA2 and sat+psp+aadA2) and one among the class 2 integrons (dfrA1+sat+aadA1). Ninety per cent of the isolates were included in the A or B1 phylogenetic groups.

Dissemination of Escherichia coli with CTX-M type ESBL between humans and yellow-legged gulls in the south of France

Extended Spectrum beta-Lactamase (ESBL) producing Enterobacteriaceae started to appear in the 1980s, and have since emerged as some of the most significant hospital-acquired infections with Escherichia coli and Klebsiella being main players. More than 100 different ESBL types have been described, the most widespread being the CTX-M beta-lactamase enzymes (bla(CTX-M) genes). This study focuses on the zoonotic dissemination of ESBL bacteria, mainly CTX-M type, in the southern coastal region of France. We found that the level of general antibiotic resistance in single randomly selected E. coli isolates from wild Yellow-legged Gulls in France was high. Nearly half the isolates (47.1%) carried resistance to one or more antibiotics (in a panel of six antibiotics), and resistance to tetracycline, ampicillin and streptomycin was most widespread. In an ESBL selective screen, 9.4% of the gulls carried ESBL producing bacteria and notably, 6% of the gulls carried bacteria harboring CTX-M-1 group of ESBL enzymes, a recently introduced and yet the most common clinical CTX-M group in France. Multi locus sequence type and phylogenetic group designations were established for the ESBL isolates, revealing that birds and humans share E. coli populations. Several ESBL producing E. coli isolated from birds were identical to or clustered with isolates with human origin. Hence, wild birds pick up E. coli of human origin, and with human resistance traits, and may accordingly also act as an environmental reservoir and melting pot of bacterial resistance with a potential to re-infect human populations.

Role of ampD homologs in overproduction of AmpC in clinical isolates of Pseudomonas aeruginosa

AmpD indirectly regulates the production of AmpC beta-lactamase via the cell wall recycling pathway. Recent publications have demonstrated the presence of multiple ampD genes in Pseudomonas aeruginosa and Escherichia coli. In the prototype P. aeruginosa strain, PAO1, the three ampD genes (ampD, ampDh2, and ampDh3) contribute to a stepwise regulation of ampC beta-lactamase and help explain the partial versus full derepression of ampC. In the present study, the roles of the three ampD homologs in nine clinical P. aeruginosa isolates with either partial or full derepression of ampC were evaluated. In eight of nine isolates, decreased RNA expression of the ampD genes was not associated with an increase in ampC expression. Sequence analyses revealed that every derepressed isolate carried mutations in ampD, and in two fully derepressed strains, only ampD was mutated. Furthermore, every ampDh2 gene was of the wild type, and in some fully derepressed isolates, ampDh3 was also of the wild type. Mutations in ampD and ampDh3 were tested for their effect on function by using a plasmid model system, and the observed mutations resulted in nonfunctional AmpD proteins. Therefore, although the sequential deletion of the ampD homologs of P. aeruginosa can explain partial and full derepression in PAO1, the same model does not explain the overproduction of AmpC observed in these clinical isolates. Overall, the findings of the present study indicate that there is still an unknown factor(s) that contributes to ampC regulation in P. aeruginosa.

Ulcer Infection by ESβL-Producing Proteus mirabilis: A Case Report

In this article, a case of decubitus ulcer infection caused by an extended-spectrum β-lactamase-producing Proteus mirabilis strain, successfully treated with oral amoxicillin-clavulanate (1-month therapy) is described. This article focuses on diffusion and clinical effect of extended-spectrum β-lactamases-producing Proteus mirabilis on treatment of gram negative lower extremity infections.

Incidence d'infections liées à Escherichia coli producteur de bêta lactamase à spectre élargi au Centre hospitalier départemental du Zou et Collines au Bénin

OBJECTIVES

Over a 6-month period, extended-spectrum betalactamase (ESBL)-producing isolates of Escherichia coli (EC) were collected from in-patients and their environment at the Zou-Collines Hospital Centre (CHDZ/C) in Benin. The aim of this study was to determine the incidence of ESBL and to describe their phenotypic susceptibility to antibiotics in a secondary hospital (500 beds) in Benin.

METHODS

From 15 May to 15 November 2005, clinical informations and samples were collected from patients suspected to have nosocomial infections. The isolates were identified, tested for antimicrobial susceptibility and analysed for the presence of ESBL genes blaTEM and blaSHV by PCR.

RESULTS

One hundred ninety-seven enterobacteria were isolated from the clinical samples of 342 patients, these isolates included 143 EC and 32/143 (22%) of these isolates produced ESBL. Forty-six EC were isolated from the environment and 7 (15%) of them produced ESBL. Except for Imipenem for which the difference was not significant, the isolates producing ESBL were more resistant to the other antibiotics (especially to third generation cephalosporins: Ceftriaxone, Cefotaxime, Ceftazidime (P<0.00001)) than non-ESBL producing isolates. Both ESBL genes blaSHV and blaTEM were identified in the EC ESBL strains from patient and from the environment.

CONCLUSION

This study shows the presence of ESBL genes among EC in various wards of the CHDZ/C hospital proving that there is a need to implement a strict hospital infection control program and a regular surveillance of resistance to antimicrobial agents.

Development and clinical validation of a molecular diagnostic assay to detect CTX-M-type beta-lactamases in Enterobacteriaceae

Enterobacterial isolates producing CTX-M beta-lactamases have recently emerged worldwide in the community and hospital settings. Because of the significant public health implications, the spread of organisms producing CTX-M enzymes merits close monitoring with enhanced surveillance efforts. A molecular diagnostic assay using two different sets of primers simultaneously for the detection of all bla(CTX-M)-like beta-lactamase genes was developed. This assay repeatedly demonstrated 100% sensitivity, specificity and positive and negative predictive values for detecting different CTX-M enzymes in well-characterised strains that included producers of VEB-, TEM- and SHV-type extended-spectrum beta-lactamases (ESBLs) and plasmid-mediated AmpC enzymes. The majority (132/240; 55%) of ESBL-producing enterobacterial isolates recovered in the Calgary Health Region during 2003 and 2004 were positive for bla(CTX-M) genes, including 81 (61%) positive for the CTX-M-9 group, 49 (37%) for the CTX-M-1 group, and two (2%) for the CTX-M-2 group. The CTX-M-specific PCR assay was reproducible and easy to use. It can be introduced in a clinical or reference laboratory to track and monitor the spread of organisms producing CTX-M enzymes in the community and hospital settings.

Molecular epidemiology of CTX-M-producing Escherichia coli in the Calgary Health Region: emergence of CTX-M-15-producing isolates

A study was designed to describe the molecular epidemiology of CTX-M-producing Escherichia coli over a 6-year period (2000 to 2005) in a large well-defined Canadian region with a centralized laboratory system. Molecular characterization was done by isoelectric focusing, PCR, and automated sequencing, while genetic relatedness was determined by pulsed-field gel electrophoresis with XbaI. Of the 552 viable extended-spectrum beta-lactamase-producing E. coli isolates isolated, 354 (64%) were positive for blaCTX-M genes associated with ISEcp1; 211 produced CTX-M-14, 128 produced CTX-M-15, 5 produced CTX-M-2, 4 produced CTX-M-3, 4 produced CTX-M-24, and 2 produced CTX-M-27. CTX-M-positive isolates were significantly more resistant to the fluoroquinolones than CTX-M-negative isolates, while CTX-M-15 producers were more likely to be resistant to gentamicin and tobramycin. There was a predominance of CTX-M-14 during the first 4 years of the study period, with community outbreaks associated with cluster 14A during 2000, 2001, and 2003. A substantial increase in CTX-M-15 producers occurred during the last 18 months and was due to clusters 15A and 15AR (where AR indicates related to A) in the hospital and nursing home sectors. Our results demonstrate that the persistence and dissemination of CTX-M genes among E. coli populations in larger geographic health care regions is dynamic, with the continuous emergence of clonally related CTX-M-15. This study illustrates the importance of molecular surveillance in tracking CTX-M-producing E. coli strains in the community and investigating their influx into hospitals.

Studies on the mechanisms of β-lactam resistance in Bordetella bronchiseptica

OBJECTIVES

Little is currently known about beta-lactam resistance in Bordetella bronchiseptica. So far, only a single beta-lactamase gene, bla(BOR-1), has been identified. In a previous study, high MICs of ampicillin, cefalotin and ceftiofur were determined among 349 porcine B. bronchiseptica isolates. The aim of this study was to identify genes associated with elevated MICs of beta-lactams and their transferability.

METHODS

Selected isolates were investigated by PCR for commonly found bla genes and class 1 integrons; selected amplicons were sequenced. Plasmid location of resistance genes was confirmed by conjugation. Beta-lactamases were characterized by SDS-PAGE and isoelectric focusing. The genomic relatedness of the isolates was investigated by XbaI macrorestriction analysis. Inhibition studies with efflux pump inhibitors were conducted. The permeability of cephalosporins into intact cells was measured exemplarily for one isolate.

RESULTS

Of the 349 B. bronchiseptica isolates, eight isolates carried a class 1 integron with a bla(OXA-2) cassette on a conjugative plasmid of ca. 50 kb. In addition, one plasmid-free isolate also carried this class 1 integron. Besides bla(BOR-1), no other beta-lactamase gene was detected in the remaining isolates with high MICs of ampicillin of >or= 32 mg/L. Inhibition experiments suggested that efflux does not play a role in beta-lactam resistance. Instead, membrane permeability for cephalosporins was reduced as shown for B. bronchiseptica isolate B543.

CONCLUSIONS

This is to the best of our knowledge the first report of a mobile bla gene in B. bronchiseptica. Reduced membrane permeability of B. bronchiseptica seems to decrease susceptibility against cephalosporins.

Model system to evaluate the effect of ampD mutations on AmpC-mediated beta-lactam resistance

Mutations within the structural gene of ampD can lead to AmpC overproduction and increases in beta-lactam MICs in organisms with an inducible ampC. However, identification of mutations alone cannot predict the impact that those mutations have on AmpD function. Therefore, a model system was designed to determine the effect of ampD mutations on ceftazidime MICs using an AmpD(-) mutant Escherichia coli strain which produced an inducible plasmid-encoded AmpC. ampD genes were amplified by PCR from strains of E. coli, Citrobacter freundii, and Pseudomonas aeruginosa. Also, carboxy-terminal truncations of C. freundii ampD genes were constructed representing deletions of 10, 21, or 25 codons. Amplified ampD products were cloned into pACYC184 containing inducible bla(ACT-1)-ampR. Plasmids were transformed into E. coli strains JRG582 (AmpD(-)) and K-12 259 (AmpD(+)). The strains were evaluated for a derepressed phenotype using ceftazidime MICs. Some mutated ampD genes, including the ampD gene of a derepressed C. freundii isolate, resulted in substantial decreases in ceftazidime MICs (from >256 microg/ml to 12 to 24 microg/ml) for the AmpD(-) strain, indicating no role for these mutations in derepressed phenotypes. However, ampD truncation products and ampD from a partially derepressed P. aeruginosa strain resulted in ceftazidime MICs of >256 microg/ml, indicating a role for these gene modifications in derepressed phenotypes. The use of this model system indicated that alternative mechanisms were involved in the derepressed phenotype observed in strains of C. freundii and P. aeruginosa. The alternative mechanism involved in the derepressed phenotype of the C. freundii isolate was downregulation of ampD transcription.