First description of CTX-M-15-producing Klebsiella pneumoniae in Portugal

D-Mannoside FimH Inhibitors as Non-Antibiotic Alternatives for Uropathogenic Escherichia coli

FimH is a type I fimbria of uropathogenic Escherichia coli (UPEC), recognized for its ability to adhere and infect epithelial urinary tissue. Due to its role in the virulence of UPEC, several therapeutic strategies have focused on the study of FimH, including vaccines, mannosides, and molecules that inhibit their assembly. This work has focused on the ability of a set of monosubstituted and disubstituted phenyl mannosides to inhibit FimH. To determine the 3D structure of FimH for our in silico studies, we obtained fifteen sequences by PCR amplification of the fimH gene from 102 UPEC isolates. The fimH sequences in BLAST had a high homology (97–100%) to our UPEC fimH sequences. A search for the three-dimensional crystallographic structure of FimH proteins in the PDB server showed that proteins 4X5P and 4XO9 were found in 10 of the 15 isolates, presenting a 67% influx among our UPEC isolates. We focused on these two proteins to study the stability, free energy, and the interactions with different mannoside ligands. We found that the interactions with the residues of aspartic acid (ASP 54) and glutamine (GLN 133) were significant to the binding stability. The ligands assessed demonstrated high binding affinity and stability with the lectin domain of FimH proteins during the molecular dynamic simulations, based on MM-PBSA analysis. Therefore, our results suggest the potential utility of phenyl mannoside derivatives as FimH inhibitors to mitigate urinary tract infections produced by UPEC; thus, decreasing colonization, disease burden, and the costs of medical care.

Multidrug-resistant Klebsiella pneumoniae harboring extended spectrum β-lactamase encoding genes isolated from human septicemias

Klebsiella pneumoniae is a major pathogen implicated in nosocomial infections. Extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae isolates are a public health concern. We aim to characterize the type of β-lactamases and the associated resistance mechanisms in ESBL-producing K. pneumoniae isolates obtained from blood cultures in a Portuguese hospital, as well as to determine the circulating clones. Twenty-two cefotaxime/ceftazidime-resistant (CTX/CAZ^R) K. pneumoniae isolates were included in the study. Identification was performed by MALDI-TOF MS and the antimicrobial susceptibility testing by disk-diffusion. The screening test for ESBL-production was performed and ESBL-producer isolates were further characterized. The presence of different beta-lactamase genes (bla_CTX-M, bla_SHV, bla_TEM, bla_KPC, bla_NDM,bla_VIM,bla_OXA-48,bla_CMY-2, bla_DHA-1,bla_FOX,bla_MOX, and bla_ACC) was analyzed by PCR/sequencing in ESBL-producer isolates, as well as the presence of other resistance genes (aac(6’)-Ib-cr, tetA/B, dfrA, qnrA/B/S, sul1/2/3) or integron-related genes (int1/2/3). Multilocus-sequence-typing (MLST) was performed for selected isolates. ESBL activity was detected in 12 of the 22 CTX/CAZ^RK. pneumoniae isolates and 11 of them carried the bla_CTX-M-15 gene (together with bla_TEM)_, and the remaining isolate carried the bla_SHV-106 gene. All the bla_CTX-M-15 harboring isolates also contained a bla_SHV gene (bla_SHV-1, bla_SHV-11 or bla_SHV-27 variants). Both bla_SHV-27 and bla_SHV-106 genes correspond to ESBL-variants. Two of the CTX-M-15 producing isolates carried a carbapenemase gene (bla_KPC2/3 and bla_OXA-48) and showed imipenem resistance. The majority of the ESBL-producing isolates carried the int1 gene, as well as sulphonamide-resistance genes (sul2 and/or sul3); the tetA gene was detected in all eight tetracycline-resistant isolates. Three different genetic lineages were found in selected isolates: ST348 (one CTX-M-15/TEM/SHV-27/KPC-2/3-producer isolate), ST11 (two CTX-M-15/TEM/SHV-1- and CTX-M-15-TEM-SHV-11-OXA-48-producer isolates) and ST15 (one SHV-106/TEM-producer isolate). ESBL enzymes of CTX-M-15 or SHV-type are detected among blood K. pneumoniae isolates, in some cases in association with carbapenemases of KPC or OXA-48 type.

An Update on Wastewater Multi-Resistant Bacteria: Identification of Clinical Pathogens Such as Escherichia coli O25b:H4-B2-ST131-Producing CTX-M-15 ESBL and KPC-3 Carbapenemase-Producing Klebsiella oxytoca

Wastewater treatment plants (WWTPs) are significant reservoirs of bacterial resistance. This work aims to identify the determinants of resistance produced by Gram-negative bacteria in the influent and effluent of two WWTPs in Portugal. A total of 96 wastewater samples were obtained between 2016 and 2019. The numbers of total aerobic and fecal contamination bacteria were evaluated, and genomic features were searched by polymerase chain reaction (PCR) and Next-Generation Sequencing (NGS). Enterobacteriaceae corresponded to 78.6% (n = 161) of the 205 isolates identified by 16sRNA. The most frequent isolates were Escherichia spp. (57.1%, n = 117), followed by Aeromonas spp. (16.1%, n = 33) and Klebsiella spp. (12.7%, n = 26). The remaining 29 isolates (14.1%) were distributed across 10 different genera. Among the 183 resistant genes detected, 54 isolates produced extended spectrum β-lactamases (ESBL), of which bla_CTX-M-15 was predominant (37 isolates; 68.5%). A KPC-3 carbapenemase-producing K. oxytoca was identified (n = 1), with bla_KPC-3 included in a transposon Tn4401 isoform b. A higher number of virulence genes (VG) (19 genes) was found in the E. coli 5301 (O25b-ST131-B2) isolate compared with a commensal E. coli 5281 (O25b-ST410-A) (six genes). Both shared five VG [Enterobactin; Aerobactin, CFA/1 (clade α); Type1 (clade γ1); Type IV]. In conclusion, this work highlights the role of relevant clinical bacteria in WWTPs, such as KPC-3-producing K. oxytoca, and, for the first time, a CTX-M-15-producing Ochromobactrum intermedium, a human opportunistic pathogen, and a SED-1-producing Citrobacter farmeri, an uncommon CTX-M-type extended-spectrum beta-lactamase.

Phylogenetic Classification, Biofilm-Forming Capacity, Virulence Factors, and Antimicrobial Resistance in Uropathogenic Escherichia coli (UPEC)

Uropathogenic Escherichia coli (UPEC) is the main cause of urinary tract infections; in recent years, its importance as a pathogen has increased due to the emergence of hypervirulent and multiresistant strains. In this study, 190 urinary isolates of E. coli were assigned into the seven phylogenetic groups A (11.1%), B1 (4.7%), B2 (46.8%), C (5.8%) D (25.3%) F (2.6%), and Clade I (2.1%), and various virulence genes were examined with polymerase chain reaction methods. All isolates had at least one virulence factor of the 9 analyzed fyuA (81.1%), fimH (96.8%), iutA (74.7%), ompT (66.8%), kpsMTII (66.8%), traT (58.9%), PAI (43.6%), PapAH (26.3%), and usp (3.2%). The results showed a direct relationship between the virulence factors and phylogenetic group A and B2. Further, virulence genetic profiles fimH, fyuA, ompT, traT, and kpsMTII correlated with the production of strong biofilm, multidrug resistance, and the production of moderate hemolysin. These results suggest that these strains may become reservoirs of genes that encode virulence factors, which could be transferred horizontally enhancing their genomic background and high possibility of acquiring new genetic information for possible dissemination. This study provides the first description of phylogroups in UPEC in the Colombian Caribbean and the association with virulence factor profile, antimicrobial susceptibility, and their possible role in the epidemiology in Colombia.

Intestinal carriage of extended-spectrum beta-lactamase-producing Enterobacteriaceae at admission in a Portuguese hospital

To evaluate the prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae fecal carriers at admission in a Portuguese hospital and to determine the epidemiology and antimicrobial resistance patterns of ESBL-producing isolates. During a 2-month period, rectal swabs were collected at hospital admission from 151 at-risk patients. In addition, 48 rectal swabs were obtained from weekly screenings of 37 patients hospitalized for > 48 h. All ESBL/carbapenemase-producing isolates were tested for antimicrobial susceptibility and characterized by PFGE and MLST. The prevalence of ESBL producers at hospital admission was 17% and 24% among at-risk patients hospitalized for > 48 h, while the prevalence of carbapenemase producers was 3% in both cases. Most of the isolates were Escherichia coli (54%) and Klebsiella pneumoniae (41%). The most common ESBL identified was CTX-M-15 (n = 17/34; 50%), followed by CTX-M-27 (n = 10; 29%), CTX-M-33 (n = 4; 12%), SHV-12 (n = 2), and CTX-M-55 (n = 1). The 20 E. coli isolates were distributed into 16 PFGE types and nine sequence types (ST), with 60% of the isolates belonging to ST131. The 15 K. pneumoniae were grouped into 12 PFGE types and nine STs, with three STs (ST17, ST449, ST147) corresponding to 60% of the isolates. A high proportion of isolates showed resistance to ciprofloxacin (86%), trimethoprim-sulfamethoxazole (68%), tobramycin (57%), and gentamicin (43%). All isolates remained susceptible to fosfomycin. A high prevalence of ESBL-producing Enterobacteriaceae was found at hospital admission among at-risk patients and > 50% of the isolates showed resistance to first-line antibiotics for the treatment of lower urinary tract infections, leaving fosfomycin as an alternative.

Whole-genome sequencing resolves a polyclonal outbreak by extended-spectrum beta-lactam and carbapenem-resistant Klebsiella pneumoniae in a Portuguese tertiary-care hospital

Klebsiella pneumoniae has emerged as an important nosocomial pathogen, with whole-genome sequencing (WGS) significantly improving our ability to characterize associated outbreaks. Our study sought to perform a genome-wide analysis of multiclonal K. pneumoniae isolates (n=39; 23 patients) producing extended spectrum beta-lactamases and/or carbapenemases sourced between 2011 and 2016 in a Portuguese tertiary-care hospital. All isolates showed resistance to third-generation cephalosporins and six isolates (five patients) were also carbapenem resistant. Genome-wide-based phylogenetic analysis revealed a topology representing ongoing dissemination of three main sequence-type (ST) clades (ST15, ST147 and ST307) and transmission across different wards, compatible with missing links that can take the form of undetected colonized patients. Two carbapenemase-coding genes were detected: blaKPC-3, located on a Tn4401d transposon, and blaGES-5 on a novel class 3 integron. Additionally, four genes coding for ESBLs (blaBEL-1, blaCTX-M-8, blaCTX-M-15 and blaCTX-M-32) were also detected. ESBL horizontal dissemination across five clades is highlighted by the similar genetic environments of blaCTX-M-15 gene upstream of ISEcp1 on a Tn3-like transposon. Overall, this study provides a high-resolution genome-wide perspective on the epidemiology of ESBL and carbapenemase-producing K. pneumoniae in a healthcare setting while contributing for the adoption of appropriate intervention and prevention strategies.

First Description of Colistin and Tigecycline-Resistant Acinetobacter baumannii Producing KPC-3 Carbapenemase in Portugal

Herein, we describe a case report of carbapenem-resistant Acinetobacter baumannii and Klebsiella pneumoniae isolates that were identified from the same patient at a Tertiary University Hospital Centre in Portugal. Antimicrobial susceptibility and the molecular characterization of resistance and virulence determinants were performed. PCR screening identified the presence of the resistance genes bla_KPC-3, bla_TEM-1 and bla_SHV-1 in both isolates. The KPC-3 K. pneumoniae isolate belonged to the ST-14 high risk clone and accumulated an uncommon resistance and virulence profile additional to a horizontal dissemination capacity. In conclusion, the molecular screening led to the first identification of the A. baumannii KPC-3 producer in Portugal with a full antimicrobial resistance profile including tigecycline and colistin.

Molecular Epidemiology of Colistin-Resistant, Carbapenemase-Producing Klebsiella pneumoniae in Serbia from 2013 to 2016

Twenty-seven colistin-resistant, carbapenemase-producing Klebsiella pneumoniae isolates were identified from hospitals in Serbia. All isolates were bla_CTX-M-15 positive; ST101, ST888, ST437, ST336, and ST307 were bla_OXA-48 positive; and ST340 was bla_NDM-1 positive. ST307 had an insertion, and ST336 had a premature stop codon in the mgrB gene. Amino acid substitutions were detected in PmrAB of isolates ST101, ST888, ST336, and ST307. The mcr-1 and mcr-2 were not detected. An increase in phoP, phoQ, and pmrK gene transcription was detected for all sequence types.

New Delhi metallo-β-lactamase and extended spectrum β-lactamases co-producing isolates are high in community-acquired urinary infections in Assam as detected by a novel multiplex polymerase chain reaction assay

BACKGROUND

The ability of microorganisms to evade antibiotic pressure is challenging in healthcare as patients have little or no drug treatment options. Detection of the prevalence of antibacterial resistance pattern helps towards improved antibiotic policy and empirical treatment.

OBJECTIVES

We carried out antibiogram profiling and documented the prevalence and co-prevalence of New Delhi metallo-β-lactamase (NDM) and extended spectrum β-lactamases (ESBL) encoding genes in urinary Escherichia coli and Klebsiella pneumonia isolates.

MATERIALS AND METHODS

Antibiotic susceptibilities were tested for 241 isolates of E. coli and K. pneumoniae from urine samples collected from out- and hospitalised patients. Polymerase chain reaction (PCR) was carried out on isolates tested positive for phenotypic production of metallo-β-lactamase and ESBL. A multiplex PCR assay was designed to detect the genes.

RESULTS

Multiplex PCR assay designed had a limit of detection of 10 3 CFU/mL in vitro. NDM detected was significantly higher among K. pneumoniae compared to E. coli (69.2% vs. 18.2%; P = 0.001). Of 17, 14 NDM positive isolates also harboured ESBL genes. The co-production of CTX-M + TEM + NDM (3/9; 33.3% and 5/8; 62.5%) was most common in K. pneumoniae and E. coli, respectively while CTX-M + TEM + SHV + NDM was found in one isolate. Of the 156 phenotypically ESBL producing isolates, CTX-M, TEM and SHV was detected by PCR in 85, 53 and 24 isolates, respectively.

CONCLUSION

NDM and ESBL co-producing isolates were both community (64.7%) and hospital (35.29%) acquired among E. coli. Antibiotic resistance can be effectively evaluated by a cost and time effective molecular method, such as the multiplex PCR used in this study, which complement culture and sensitivity tests.

Virulence and plasmidic resistance determinants of Escherichia coli isolated from municipal and hospital wastewater treatment plants

Escherichia coli is simultaneously an indicator of water contamination and a human pathogen. This study aimed to characterize the virulence and resistance of E. coli from municipal and hospital wastewater treatment plants (WWTPs) in central Portugal. From a total of 193 isolates showing reduced susceptibility to cefotaxime and/or nalidixic acid, 20 E. coli with genetically distinct fingerprint profiles were selected and characterized. Resistance to antimicrobials was determined using the disc diffusion method. Extended spectrum β-lactamase and plasmid-mediated quinolone resistance genes, phylogroups, pathogenicity islands (PAIs) and virulence genes were screened by polymerase chain reaction (PCR). CTX-M producers were typed by multilocus sequence typing. Resistance to beta-lactams was associated with the presence of bla(TEM), bla(SHV), bla(CTX-M-15) and bla(CTX-M-32). Plasmid-mediated quinolone resistance was associated with qnrA, qnrS and aac(6')-Ib-cr. Aminoglycoside resistance and multidrug-resistant phenotypes were also detected. PAI IV(536), PAI II(CFT073), PAI II(536) and PAI I(CFT073), and uropathogenic genes iutA, papAH and sfa/foc were detected. With regard to the clinical ST131 clone, it carried bla(CTX-M-15), blaTEM-type, qnrS and aac(6')-lb-cr; IncF and IncP plasmids, and virulence factors PAI IV(536), PAI I(CFT073), PAI II(CFT073), iutA, sfa/foc and papAH were identified in the effluent of a hospital plant. WWTPs contribute to the dissemination of virulent and resistant bacteria in water ecosystems, constituting an environmental and public health risk.

Molecular characterization of ESBL-producing Enterobacteriaceae in northern Portugal

Extended-spectrum β-lactamases (ESBLs) prevalence was studied in the north of Portugal, among 193 clinical isolates belonging to citizens in a district in the boundaries between this country and Spain from a total of 7529 clinical strains. In the present study we recovered some members of Enterobacteriaceae family, producing ESBL enzymes, including Escherichia coli (67.9%), Klebsiella pneumoniae (30.6%), Klebsiella oxytoca (0.5%), Enterobacter aerogenes (0.5%), and Citrobacter freundii (0.5%). β -lactamases genes blaTEM, blaSHV, and blaCTX-M were screened by polymerase chain reaction (PCR) and sequencing approaches. TEM enzymes were among the most prevalent types (40.9%) followed by CTX-M (37.3%) and SHV (23.3%). Among our sample of 193 ESBL-producing strains 99.0% were resistant to the fourth-generation cephalosporin cefepime. Of the 193 isolates 81.3% presented transferable plasmids harboring bla ESBL genes. Clonal studies were performed by PCR for the enterobacterial repetitive intragenic consensus (ERIC) sequences. This study reports a high diversity of genetic patterns. Ten clusters were found for E. coli isolates and five clusters for K. pneumoniae strains by means of ERIC analysis. In conclusion, in this country, the most prevalent type is still the TEM-type, but CTX-M is growing rapidly.

Prevalence and characterization of multidrug-resistant and extended-spectrum beta-lactamase-producing Escherichia coli from pediatric wards of a Malaysian hospital

The emergence of Escherichia coli resistant to extended-spectrum cephalosporins (ESCs) is of concern as ESC is often used to treat infections by Gram-negative bacteria. One-hundred and ten E. coli strains isolated in 2009-2010 from children warded in a Malaysian tertiary hospital were analyzed for their antibiograms, carriage of extended-spectrum beta-lactamase (ESBL) and AmpC genes, possible inclusion of the beta-lactamase genes on an integron platform, and their genetic relatedness. All E. coli strains were sensitive to carbapenems. About 46% of strains were multidrug resistant (MDR; i.e., resistant to ≥3 antibiotic classes) and almost half (45%) were nonsusceptible to ESCs. Among the MDR strains, high resistance rates were observed for ampicillin (98%), tetracycline (75%), and trimethoprim/sulfamethoxazole (73%). Out of 110 strains, bla(TEM-1) (49.1%), bla(CTX-M) (11.8%), and bla(CMY-2) (6.4%) were detected. Twenty-one strains were ESBL producers. CTX-M-15 was the predominant CTX-M variant found and this is the first report of a CTX-M-27-producing E. coli strain from Malaysia. Majority (3.1%) of the strains harbored class 1 integron-encoded integrases with a predominance of aadA and dfr genes within the integron variable region. No gene cassette encoding ESBL genes was found and integrons were not significantly associated with ESBL or non-ESBL producers. Possible clonal expansion was observed for few CTX-M-15-positive strains but the O25-ST131 E. coli clone known to harbor CTX-M-15 was not detected while CMY-2-positive strains were genetically diverse.

Persistence of uropathogenic Escherichia coli strains in the host for long periods of time: relationship between phylogenetic groups and virulence factors

Escherichia coli cause the majority of urinary tract infections (UTIs). Virulence plays an important role in the initial stages of interaction with the host, facilitating colonization of the urinary tract tissue. The purpose of this study was to assess whether there is a relationship between virulence and antibiotic resistance in the persistence of uropathogenic E. coli strains. This study included five patients with UTI between 2001 and 2009. The antibiotic resistance phenotype of 29 E. coli isolates was determined by the disk diffusion method. Clonal relationship was determined through M13 polymerase chain reaction (PCR) fingerprinting. Phylogeny, virulence factors, β-lactamases, and replicon typing were studied through PCR. Antibiogram profiles were found from different patients and corresponded to CTX-M-2, CTX-M-15, CTX-M-32, and TEM-52 enzymes. Plasmids belonged essentially to incompatibility group IncF. No clonal relationship was observed among isolates from different patients, except for patients 4 and 5. Phylogenetic group A was predominant. Our work showed that commensal group A possesses the same virulence factors as the pathogenic groups B1 and D. E. coli common pilus and type 1 fimbriae could play an important role in the persistence in the host and in symptomatic UTI, respectively, which, combined with extended-spectrum β-lactamases (ESBLs), are a cause of the dissemination of microorganisms in the hospital and the community.

Characterization of multidrug-resistant and extended-spectrum beta-lactamase-producing Klebsiella pneumoniae strains from Malaysian hospitals

The emergence of multidrug-resistant (MDR) and extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae poses a serious antibiotic management problem as resistance genes are easily transferred from one organism to another. Fifty-one strains of K. pneumoniae isolated from sporadic cases in various hospitals throughout Malaysia were analysed by antimicrobial susceptibility testing, PCR detection of ESBL-encoding genes and DNA fingerprinting. Although 27 of the 51 K. pneumoniae strains were MDR (i.e. resistant to three or more classes of antibiotics), the majority of the strains (98 %) were sensitive to imipenem. PCR detection using ESBL gene-specific primers showed that 46 of the K. pneumoniae strains harboured bla(SHV), 19 harboured bla(CTX-M), 5 harboured bla(OXA-1) and 4 harboured bla(TEM-1). Class 1 integron-encoded intI1 integrase was detected in 21 of the 51 K. pneumoniae strains and amplification of the integron 5'CS region showed the presence of several known antibiotic resistance gene cassettes of various sizes. Results of conjugation and transformation experiments indicated that some of the ESBL-encoding genes (i.e. bla(SHV), bla(CTX-M) and bla(TEM-1)) were transmissible and were likely plasmid-encoded. DNA fingerprinting using PFGE and PCR-based methods indicated that the 51 K. pneumoniae strains were genetically diverse and heterogeneous.

Virulence genotype and nematode-killing properties of extra-intestinal Escherichia coli producing CTX-M beta-lactamases

This study evaluated the virulence potential of Escherichia coli isolates producing CTX-M beta-lactamases. During a 24-month period, 33 extended-spectrum beta-lactamase (ESBL)-producing E. coli, including 14 CTX-M-producers, were isolated from urinary tract infections at Nîmes University Hospital, France. The prevalence of 14 major virulence factors (VFs) was investigated by PCR and compared with the prevalence in a group of 99 susceptible E. coli isolates. Ten VFs were less prevalent (p <0.05) in the ESBL isolates than the susceptible E. coli, while iutA and traT were more prevalent in ESBL isolates (p <0.05). Moreover, the CTX-M-producing isolates had significantly fewer VFs than TEM-producing isolates. A novel infection model using the nematode Caenorhabditis elegans was developed to assess the virulence properties of extra-intestinal pathogenic E. coli (ExPEC) strains in vivo. C. elegans infection assays, using 14 ESBL-producing E. coli and ten susceptible E. coli isolates, indicated that the ability to kill nematodes correlated with the presence of VFs, and that CTX-M-producing isolates had relatively low virulence in vivo. Overall, the results suggested that hospital-acquired CTX-M-producing E. coli, although adapted for survival in an antibiotic-rich environment such as the hospital milieu, have a relatively low intrinsic virulence potential.

Nosocomial outbreak of CTX-M-15-producing E. coli in Norway

Seven E. coli isolates expressing resistance to 3rd generation cephalosporins were recovered from blood (n=2), kidney and lung tissue (n=1), and urinary tract (n=4) samples from seven patients hospitalised or recently discharged from the Divisions of Geriatrics and Pulmonary Medicine, Central Hospital of Rogaland, between July and September 2004. All isolates expressed a typical ESBL-cefotaximase profile (cefotaxime MIC>ceftazidime MIC) with clavulanic acid synergy. A bla(CTX-M-15) genotype was confirmed in six strains that were coresistant to gentamicin, nitrofurantoin, trimethoprim-sulfamethoxazole and ciprofloxacin. A bla(CTX-M-3) genotype was detected in the last strain. XbaI-PFGE patterns of the six bla(CTX-M-15) isolates revealed a clonal relationship. Bla(CTX-M-15) strains were also positive for the ISEcp1-like insertion sequences that have been shown to be involved in the mobilization of bla(CTX-M.) Further analyses revealed two bla(CTX-M-15)-positive E. coli urinary isolates clonally related to the outbreak strain from two different patients at the same divisions in January and February 2004. These patients were later re-hospitalised and one had E. coli with an ESBL-cefotaximase profile in sputum and nasopharyngeal specimen during the outbreak period. Clinical evaluation suggests that the CTX-M-producing E. coli strains contributed to death in three patients due to delayed efficient antimicrobial therapy. The outbreak emphasises the epidemic potential of multiple-antibiotic-resistant CTX-M-15-producing E. coli also in a country with low antibiotic usage and low prevalence of antimicrobial resistance.

Spread of extended-spectrum beta-lactamase CTX-M-producing escherichia coli clinical isolates in community and nosocomial environments in Portugal

Of the 181 unduplicated Escherichia coli strains isolated in nine different hospitals in three Portuguese regions, 119 were extended-spectrum beta-lactamase (ESBL)-CTX-M producers and were selected for phenotype and genotype characterization. CTX-M producer strains were prevalent among community-acquired infections (56%), urinary tract infections (76%), and patients >/=60 years old (76%). In MIC tests, all strains were resistant to cefotaxime, 92% were resistant to ceftazidime, 93% were resistant to quinolones, 89% were resistant to aminoglycoside, and 26% were resistant to trimethoprim-sulfamethoxazole; all strains were sensitive to carbapenems, and 92% of the strains had a multidrug resistance phenotype. Molecular methods identified 109 isolates harboring a bla(CTX-M-15) gene, 1 harboring the bla(CTX-M-32) gene (first identification in the country), and 9 harboring the bla(CTX-M-14) gene. All isolates presented the ISEcp1 element upstream from the bla(CTX-M) genes; one presented the IS903 element (downstream of bla(CTX-M-14) gene), and none had the IS26 element; 85% carried bla(TEM-1B), and 84% also carried a bla(OXA-30). Genetic relatedness analysis based on pulsed-field gel electrophoresis defined five clusters and indicated that 76% of all isolates (from cluster IV) corresponded to a single epidemic strain. Of the 47 strains from one hospital, 41 belonged to cluster IV and were disseminated in three main wards. CTX-M-producing E. coli strains are currently a problem in Portugal, with CTX-M-15 particularly common. This study suggests that the horizontal transfer of bla(CTX-M) genes, mediated by plasmids and/or mobile elements, contributes to the dissemination of CTX-M enzymes to community and hospital environments. The use of extended-spectrum cephalosporins, quinolones, and aminoglycosides is compromised, leaving carbapenems as the therapeutic option for severe infections caused by ESBL producers.

A novel reverse-line hybridization assay for identifying genotypes of CTX-M-type extended-spectrum β-lactamases

OBJECTIVES

To develop a reverse-line hybridization assay to identify CTX-M genotypes, potentially useful for large-scale investigation of surveillance collections.

METHODS

Isolates carrying previously characterized bla(CTX-M) genes were used to develop the method. In addition, 334 isolates from five separate surveys were used to validate the method. CTX-M group was known from an independent multiplex PCR for 122 isolates and genotype was confirmed for 80 isolates by DNA sequencing. A multiplex PCR was designed to amplify a genotype-specific region within the bla(CTX-M) open-reading frame. Oligonucleotides were designed to hybridize to regions within each amplicon, covering mutations that distinguish among bla(CTX-M) genotypes.

RESULTS

CTX-M phylogenetic groups were identified by the multiplex PCR with 100% concordance. The reverse-line hybridization assay specifically identified commonly-reported variants within these groups (98.7% concordance).

CONCLUSIONS

The hybridization method enabled precise identification of CTX-M genes, rather than just to group level, without the need for DNA sequencing. In its present format, the method enables 43 isolates to be processed per membrane, giving results within one working day. It is a useful tool for the epidemiological investigation of bla(CTX-M) genes among survey collections of Enterobacteriaceae.

Caenorhabditis elegans : modèle d'étude in vivo de la virulence bactérienne

The nematode Caenorhabditis elegans presents many advantages as a model system. The worm has recently emerged as a potentially useful tool for the study of host-pathogen interactions. This paper presents advantages and inconveniences of this model, the variety of bacterial pathogens studied, and its use to monitor virulence of Extraintestinal Escherichia coli strains.

Survey of extended-spectrum β-lactamases in Escherichia coli isolates from a Portuguese hospital and characterisation of a novel class 1 integron (In60A) carrying the blaCTX-M-9 gene

Between November 2001 and November 2004, 231 Escherichia coli isolates resistant to beta-lactam antibiotics were identified. In 14 isolates, bla(TEM-24) (2 isolates), bla(TEM-52) (5 isolates) and bla(TEM-26) (7 isolates) were identified. In 145 E. coli isolates with the same M13 fingerprinting profile and the same resistance phenotype, the bla(CTX-M-15) gene was found in association with an insertion sequence ISEcp1. The bla(CTX-M-2) gene was identified in one E. coli isolate (290HSM), and in other E. coli isolate (246HSM) the bla(CTX-M-9) gene was contained in a new complex sul1-type class 1 integron (named In60A). This is the first report of three cefotaximases (CTX-M-15, CTX-M-2 and CTX-M-9) in E. coli isolates from a Portuguese hospital.

Virulence factors of Escherichia coli isolates that produce CTX-M-type extended-spectrum beta-lactamases

This study determined the phylogenetic groups and virulence factors of 37 Escherichia coli isolates producing types of CTX-M compared with those of 19 isolates producing different types of extended-spectrum beta-lactamases (ESBLs) in a well-defined North American population. Most CTX-M-14 producers (97%) were from phylogenic group D; 67% of the CTX-M-15 producers were from group B2. A single CTX-M-14-producing strain belonged to clonal group A. There were significant prevalence differences for individual virulence factors among CTX-M producers and nonproducers; however, aggregate virulence factor scores were similar. CTX-M producers more commonly caused repeat urinary tract infections. Our results indicate that CTX-M type predicts phylogenetic background, and the virulence potential of ESBL-producing E. coli isolates is a complex issue, requiring further study and ongoing surveillance.

CTX-M-15 extended-spectrum β-lactamase from Nigerian Klebsiella pneumoniae

OBJECTIVES

In this study, extended-spectrum beta-lactamases (ESBLs) were characterized from 30 selected multidrug-resistant Klebsiella pneumoniae strains isolated from patients with community-acquired urinary tract infections from Southwest Nigeria.

METHODS

The beta-lactamases were phenotypically characterized using isoelectric focusing, genotypically characterized using PCR assays and hybridization of the PCR products. Two of the bla(CTX-M) genes were completely sequenced. The location of the CTX-M-type genes was determined using transformation, DNA-DNA hybridization, PCR assays and hybridization of the PCR products from the Escherichia coli transformants.

RESULTS

All 30 isolates produced at least one beta-lactamase. Seventeen of the isolates were resistant to cefotaxime, and had > or =100-fold reduction in susceptibility with cefotaxime plus clavulanic acid (4 mg/L), indicating the presence of an ESBL. The 17 isolates were shown to have bla(CTX-M) genes that were associated with large plasmids (> or =58 kb), which also carried a tetracycline resistance gene, tet(A), and various aminoglycoside resistance genes. Two CTX-M-type genes were sequenced and had amino acid sequences indistinguishable from previously sequenced CTX-M-15 beta-lactamases. The ISEcp1 element was located upstream of bla(CTX-M-15) in the same position as previously described. In addition, 23 of the isolates produced TEM beta-lactamases, 27 produced SHV beta-lactamases and four produced AmpC beta-lactamases.

CONCLUSIONS

Thirty K. pneumoniae produced multiple beta-lactamases, with 57% producing CTX-M enzymes. This is the first characterization of CTX-M-15-positive K. pneumoniae in Western Africa.