Susana Correia

Potential impact of antimicrobial resistance in wildlife, environment and human health

Given the significant spatial and temporal heterogeneity in antimicrobial resistance distribution and the factors that affect its evolution, dissemination, and persistence, it is important to highlight that antimicrobial resistance must be viewed as an ecological problem. Monitoring the resistance prevalence of indicator bacteria such as Escherichia coli and enterococci in wild animals makes it possible to show that wildlife has the potential to serve as an environmental reservoir and melting pot of bacterial resistance. These researchers address the issue of antimicrobial-resistant microorganism proliferation in the environment and the related potential human health and environmental impact.

Vancomycin‐resistant enterococci from Portuguese wastewater treatment plants

The objective of this study was to evaluate the incidence of vancomycin resistant enterococci in sludge and sewage of urban and poultry‐slaughterhouse wastewater treatment plants. A total of 17 vancomycin resistant enterococci (eight vanA ‐containing Enterococcus faecium and nine vanC1/vanC2 ‐containing Enterococcus gallinarum/casseliflavus) were found among 499 isolates of sewage and sludge samples of 14 urban and nine poultry‐slaughterhouse wastewater treatment plants. These seventeen VRE isolates showed resistance to kanamycin (n = 8), tetracycline (n = 7), erythromycin (n = 7), ciprofloxacin (n = 7), ampicillin (n = 7), streptomycin (n = 6), and gentamicin (n = 2). The tetM gene, related with tetracycline resistance, was found in six of eight van A‐containing isolates, in all seven vanC‐1 isolates and in one of two vanC‐2 isolates. The ermB gene in seven erythromycin‐resistant isolates; and the aac6 ′‐aph2 ″ gene in the two high‐level‐gentamicin‐resistant isolates. Moreover, two vanA ‐containing E. faecium isolates harbored the hyl virulence gene, and three isolates the entA bacteriocin gene. The purK‐1 allele was detected in our urban vanA ‐containing E. faecium isolate, and we found as well the purK‐6 allele in one poultry‐slaughterhouse vanA ‐containing E. faecium isolate. This study suggests that the wastewater treatment plants might be an important source of dissemination of antibiotic‐resistant enterococci in Portugal. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Antimicrobial resistance in faecal enterococci and Escherichia coli isolates recovered from Iberian wolf.

The aim of this study was to report the antimicrobial resistance, the molecular mechanisms associated and the detection of virulence determinants within faecal Enterococcus spp. and Escherichia coli isolates of Iberian wolf. Enterococci (n = 227) and E. coli (n = 195) isolates were obtained from faecal samples of Iberian wolf (Canis lupus signatus). High rates of resistance were detected for tetracycline and erythromycin among the enterococci isolates, and most of resistant isolates harboured the tet(M) and/or tet(L) and erm(B) genes, respectively. The blaTEM, tet(A) and/or tet(B), and aadA or strA‐strB genes were detected among most ampicillin‐, tetracycline‐ or streptomycin‐resistant E. coli isolates, respectively. E. coli isolates were ascribed to phylogroups A (n = 56), B1 (91), B2 (13) and D (35). The occurrence of resistant enterococci and E. coli isolates in the faecal flora of Iberian wolf, including the presence of resistant genes in integrons, and virulence determinants was showed in this study. Iberian wolf might act as reservoir of certain resistance genes that could be spread throughout the environment.

On the performance of wavelets for handwritten numerals recognition

This paper validates a recognition system using bi-dimensional wavelet transforms as the feature extractor and investigates the relevance of each subband image in the recognition process. An experiment to verify the efficiency of the wavelets was performed omitting the feature extraction step. Results show that information about the relevant image features are evenly distributed in all subband images of wavelet coefficients and that wavelets are promising feature extractors. Numerals from the NIST database were used for evaluation of the systems tested.

Mechanisms of quinolone action and resistance: where do we stand?

Quinolone antibiotics represent one of the most important classes of anti-infective agents and, although still clinically valuable, their use has been compromised by the increasing emergence of resistant strains, which has become a prevalent clinical problem. Quinolones act by inhibiting the activity of DNA gyrase and topoisomerase IV - two essential bacterial enzymes that modulate the chromosomal supercoiling required for critical nucleic acid processes. The acquisition of quinolone resistance is recognized to be multifactorial and complex. The main resistance mechanism consists of one or a combination of target-site gene mutations that alter the drug-binding affinity of target enzymes. However, other mechanisms such as mutations that lead to reduced intracellular drug concentrations, by either decreased uptake or increased efflux, and plasmid-encoded resistance genes producing either target protection proteins, drug-modifying enzymes or multidrug efflux pumps are known to contribute additively to quinolone resistance. The understanding of these different resistance mechanisms has improved significantly in recent years; however, many details remain to be clarified and the contribution of less-studied mechanisms still needs to be better elucidated in order to fully understand this phenotype.

Optimizing the recognition rates of unconstrained handwritten numerals using biorthogonal spline wavelets

In this paper an approach for off-line recognition of unconstrained handwritten numerals is presented. This approach uses the Cohen-Daubechies-Feauveau (CDF) family of biorthogonal spline wavelets as a feature extractor for absorbing local variations in handwritten characters and a multilayer cluster neural network as classifier. Experiments with the bases CDF 2/2, CDF 2/4, CDF 3/3 and CDF 3/7 were performed using the handwritten numeral database of Concordia University of Canada. The results show that CDF biorthogonal wavelets yield a performance improvement of 2.4% in numeral recognition, compared to the results obtained with the Haar wavelets.

High prevalence of ESBL-producing Escherichia coli isolates among hemodialysis patients in Portugal: appearance of ST410 with the blaCTX-M-14 gene ☆

Ten extended-spectrum β-lactamase-producing Escherichia coli isolates were detected among 121 fecal samples (8.3%) recovered from hemodialysis patients in Portugal. The isolates harbored the bla(CTX-M-15), bla(CTX-M-14a), and/or bla(CTX-M-1) genes. A new sequence type, ST2229, was detected, and this study also reports, for the first time, ST410 CTX-M-14-producing isolates.

Vancomycin-resistant enterococci among haemodialysis patients in Portugal: Prevalence and molecular characterization of resistance, virulence and clonality

INTRODUCTION Vancomycin-resistant enterococci (VRE) among haemodialysis patients has increased rapidly and, to date, there is no report of this incidence in Portugal. METHODS A total of 121 faecal samples were collected from haemodialysis patients, and then tested for VRE. Antimicrobial resistance, virulence and multilocus sequence typing (MLST) were studied. RESULTS VRE prevalence was 3.3%. Three VRE isolates, Enterococcus faecium, Enterococcus faecalis and Enterococcus raffinosus, were multi-resistant and vanA-positive. E. faecium and E. faecalis belonged to CC17 and CC2, respectively. CONCLUSION Haemodialysis patients in Portugal are colonized with virulent, multi-resistant enterococci from high-risk clonal complexes, representing a public health concern.

Comparative subproteomic analysis of clinically acquired fluoroquinolone resistance and ciprofloxacin stress in Salmonella Typhimurium DT104B

Antimicrobial resistance is a worldwide public health threat and Salmonella enterica subsp. enterica serotype Typhimurium phage type DT104B multiresistant strains with additional quinolone resistance have been responsible for global outbreaks and high mortality. Quinolone resistance is known to be multifactorial but is still far from a complete understanding. To give new insights about the resistance mechanisms involved, this work aimed to evaluate subproteome changes between an S. Typhimurium DT104B clinical strain that acquired fluoroquinolone resistance after treatment (Se20) and its pretreatment parental strain (Se6), and also subproteome variations in Se20 under ciprofloxacin (CIP) stress (Se20+CIP).

Multiresistant extended-spectrum β-lactamase producing Escherichia coli in human urine samples in Portugal

The introduction of antimicrobial drugs in clinical practice is usually followed by the emergence of resistant strains. The inadequate use, auto-medication, exclusive use of extended-spectrum drugs, or the premature break of antimicrobial treatments are factors to take in consideration. Multiresistant extended-spectrum b-lactamase (ESBL) producing-Escherichia coli are among the top six most worrying human pathogens. This organism is a common inhabitant of the human intestinal tract but, in certain cases, it may cause infectious diseases, such as enteric, lung, nervous, and urinary tract infections. In recent years, E. coli strains have been developing resistance to some antimicrobial agents used to treat infections and are associated with therapeutic failure, causing great concern. Sixty-five ESBL-producing E. coli isolates, obtained from individual human urine samples,were selected for study. The isolates were obtained monthly from urine samples of patients at the Hospital Center of Trás-os-Montes and Alto Douro, fromNovember2009 to January 2011. Susceptibility to 16 antibiotics (ampicillin, amoxicillin þ clavulanic acid, cefoxitin, cefotaxime, ceftazidime, aztreonam, imipenem, gentamicin, amikacin, tobramycin, streptomycin, nalidixic acid, ciprofloxacin, sulfamethoxazole/trimethoprim, tetracyclineandchloramphenicol)was testedby thedisk-diffusion method in all recovered isolates and ESBL-phenotypic detection was confirmed out by double-disk test according to the CLSI criteria. The presence of resistance genes as well the classification in phylogenetic groups (A, B1, B2, or D) were performed by PCR (Table 1).