Carmen Torres

Mechanisms of Resistance in Multiple-Antibiotic-Resistant Escherichia coli Strains of Human, Animal, and Food Origins

ABSTRACT Seventeen multiple-antibiotic-resistant nonpathogenic Escherichia coli strains of human, animal, and food origins showed a wide variety of antibiotic resistance genes, many of them carried by class 1 and class 2 integrons. Amino acid changes in MarR and mutations in marO were identified for 15 and 14 E. coli strains, respectively.

Antibiotic Resistance in Campylobacter Strains Isolated from Animals, Foods, and Humans in Spain in 1997–1998

ABSTRACT Colonization by Campylobacter strains was investigated in human, broiler, and pig fecal samples from 1997- 1998, as well as in foods of animal origin, and antibiotic susceptibility testing was carried out for these strains. Campylobacter strains were isolated in the foods of animal origin (55 of 101 samples; 54.4%), intestinal samples from broilers (85 of 105; 81%), and pigs (40 of 45; 88.9%). A total of 641 Campylobacter strains were isolated from 8,636 human fecal samples of clinical origin (7.4%).Campylobacter jejuni was the most frequently isolated species from broilers (81%) and humans (84%), and Campylobacter coli was most frequently isolated from pigs (100%). An extremely high frequency of ciprofloxacin resistance was detected amongCampylobacter strains, particularly those isolated from broilers and pigs (99%), with a slightly lower result for humans (72%); cross-resistance with nalidixic acid was almost always observed. A higher frequency of resistance to erythromycin (81.1%), ampicillin (65.7%), gentamicin (22.2%), and amikacin (21.6%) was detected in C. coli strains isolated from pigs compared to those isolated from humans (34.5, 29.3, 8.6, and 0%, respectively). A low frequency of erythromycin resistance was found in C. jejuni or C. coli isolated from broilers. A greater resistance to ampicillin and gentamicin (47.4 and 11.9%, respectively) was detected in C. jejuni isolated from broilers than in human strains (38 and 0.4%, respectively). β-Lactamase production was found in 81% of the Campylobacter strains tested, although 44% of them were characterized as ampicillin susceptible. The increasing rates of Campylobacter resistance make advisable a more conservative policy for the use of antibiotics in farm animals.

Multilocus Sequence Typing Scheme for Enterococcus faecalis Reveals Hospital-Adapted Genetic Complexes in a Background of High Rates of Recombination

ABSTRACT A multilocus sequence typing (MLST) scheme based on seven housekeeping genes was used to investigate the epidemiology and population structure of Enterococcus faecalis. MLST of 110 isolates from different sources and geographic locations revealed 55 different sequence types that grouped into four major clonal complexes (CC2, CC9, CC10, and CC21) by use of eBURST. Two of these clonal complexes, CC2 and CC9, are particularly fit in the hospital environment, as CC2 includes the previously described BVE clonal complex identified by an alternative MLST scheme and CC9 includes exclusively isolates from hospitalized patients. Identical alleles were found in genetically diverse isolates with no linkage disequilibrium, while the different MLST loci gave incongruent phylogenetic trees. This demonstrates that recombination is an important mechanism driving genetic variation in E. faecalis and suggests an epidemic population structure for E. faecalis. Our novel MLST scheme provides an excellent tool for investigating local and short-term epidemiology as well as global epidemiology, population structure, and genetic evolution of E. faecalis.

β-Lactamases in Ampicillin-Resistant Escherichia coli Isolates from Foods, Humans, and Healthy Animals

ABSTRACT TEM-, SHV-, and OXA-type β-lactamases were studied by PCR with 124 ampicillin-resistant (AMPr) Escherichia coli isolates recovered from foods of animal origin (n = 20) and feces of humans (n = 49) and healthy animals (n = 55). PCR showed that 103 isolates were positive for TEM and negative for SHV and OXA. Three E. coli isolates showed a positive reaction for OXA, and one showed a positive reaction for SHV. The remaining 17 E. coli isolates were negative for the three enzymes by PCR. Fifty-seven of the 103 blaTEM amplicons were sequenced. Different molecular variants of blaTEM-1 were found in 52 isolates: blaTEM-1a (n = 9), blaTEM-1b (n = 36), blaTEM-1c (n = 6), and blaTEM-1f (n = 1). Four inhibitor-resistant TEM (IRT) β-lactamase-encoding genes were also detected: blaTEM-30c (IRT-2), blaTEM-34b (IRT-6), blaTEM-40b (IRT-11), and blaTEM-51a (IRT-15). A new blaTEM gene, named blaTEM-95b, which showed a mutation in amino acid 145 (P→A) was detected. It was found in a food isolate of chicken origin (AMPr, amoxicillin-clavulanic acid susceptible). The promoter region in 24 blaTEM amplicons was analyzed, and the weak P3 promoter was found in 23 of them (blaTEM-1 in 20 amplicons and blaTEM-51a, blaTEM-30c, and blaTEM-95b in 1 amplicon each). The strong Pa/Pb promoter was found only in the blaTEM-34b gene. No extended-spectrum β-lactamases were detected. Mutations at position −42 or −32 in the ampC gene promoter were demonstrated in 4 of 10 E. coli isolates for which the cefoxitin MIC was ≥16 μg/ml. Different variants of blaTEM-1 and IRT blaTEM genes were found among the AMPrE. coli isolates from foods and the feces of humans and healthy animals, and a new gene, blaTEM-95b (P3), was detected.

Detection of CMY-2, CTX-M-14, and SHV-12 β-Lactamases in Escherichia coli Fecal-Sample Isolates from Healthy Chickens

ABSTRACT Genes encoding the CMY-2, CTX-M-14, and SHV-12 β-lactamases were detected in three of five Escherichia coli isolates from fecal samples from healthy chickens which showed resistance or diminished susceptibility to extended-spectrum cephalosporins. A −42 mutation at the promoter region of the ampC gene was detected in the other two isolates.

Macrolide Resistance Genes in Enterococcus spp.

ABSTRACT Seventy-eight isolates of different Enterococcusspecies (E. faecalis, n = 27; E. faecium, n = 23; E. durans,n = 8; E. avium, n = 6;E. hirae, n = 9; E. gallinarum, n = 3; and E. casseliflavus, n = 2) with a variety of erythromycin resistance phenotypes were examined for the presence of macrolide resistance genes (ermA, ermB,ermC, ermTR, mefA/E, andmsrA). Positive PCR amplifications of ermB were obtained for 39 of 40 highly erythromycin-resistantEnterococcus isolates (MICs, >128 μg/ml) of different species; the remaining highly resistant E. faecium isolate was positive for PCR amplification of ermA but was negative for PCR amplification of the ermB and ermCgenes. For all enterococcal strains for which erythromycin MICs were ≤32 μg/ml PCRs were negative for erm methylase genes. For all E. faecium isolates PCR amplified products of the expected size of 400 bp were obtained when msrA primers were used, with the results being independent of the erythromycin resistance phenotype. All the other enterococcal species gave negative results by msrA PCRs. Sequencing of the msrAPCR products from either erythromycin-susceptible, low-level-resistant, or highly resistant E. faecium strains showed that the amplicons did not correspond to the msrA gene described forStaphylococcus epidermidis but corresponded to a new putative efflux determinant, which showed 62% identity with themsrA gene at the DNA level and 72% similarity at the amino acid level. This new gene was named msrC.

Antibiotic resistance in Escherichia coli isolates obtained from animals, foods and humans in Spain

Antibiotic resistance was investigated in 474 Escherichia coli isolates recovered from animal faeces (broilers, pigs, pets, bulls and horses), human faeces (patients and healthy volunteers) and food products of animal origin. E. coli isolates (3260) recovered from human significant infectious samples were also included. There was a high frequency of nalidixic acid, ciprofloxacin and gentamicin resistance in E. coli isolates from broilers (88, 38 and 40%, respectively), and from foods (53, 13 and 17%). High levels of resistance to trimethoprim-sulphamethoxazole and tetracycline have been found in E. coli isolates from broilers, pigs and foods. These data raise important questions about the potential impact of antibiotic use in animals and the possible entry of resistant pathogens into the food chain.

High tolerance of wild Lactobacillus plantarum and Oenococcus oeni strains to lyophilisation and stress environmental conditions of acid pH and ethanol

A total of 76 Lactobacillus plantarum and Oenococcus oeni wild strains were recovered from traditionally elaborated Spanish red wines and were investigated with respect to their response to acid pH, lyophilisation, temperature and ethanol concentrations which are normally lethal to lactic acid bacteria. Both L. plantarum and O. oeni strains were able to grow at pH 3.2, were highly resistant to lyophilisation treatment and proliferated in the presence of up to 13% ethanol at 18 degrees C. Therefore, it is shown that both species are highly tolerant to stress conditions and that similarly to O. oeni strains, L. plantarum strains are of interest in beverage biotechnology.

Monitoring and Characterization of Extended-Spectrum β-Lactamases in Escherichia coli Strains from Healthy and Sick Animals in Spain in 2003

ABSTRACT Genes encoding CTX-M-14, CTX-M-9, CTX-M-1, CTX-M-32, SHV-12, TEM-52, or CMY-2 β-lactamases were detected in 21 Escherichia coli strains recovered during 2003 from sick animals (11 of 459 [2.4%] strains) and healthy animals (10 of 158 [6.3%] strains) in Spain. Twelve of these strains harbored blaCTX-M genes and showed unrelated pulsed-field gel electrophoresis patterns.

Public Health Risks of Enterobacterial Isolates Producing Extended-Spectrum β-Lactamases or AmpC β-Lactamases in Food and Food-Producing Animals: An EU Perspective of Epidemiology, Analytical Methods, Risk Factors, and Control Options

The blaESBL and blaAmpC genes in Enterobacteriaceae are spread by plasmid-mediated integrons, insertion sequences, and transposons, some of which are homologous in bacteria from food animals, foods, and humans. These genes have been frequently identified in Escherichia coli and Salmonella from food animals, the most common being blaCTX-M-1, blaCTX-M-14, and blaCMY-2. Identification of risk factors for their occurrence in food animals is complex. In addition to generic antimicrobial use, cephalosporin usage is an important risk factor for selection and spread of these genes. Extensive international trade of animals is a further risk factor. There are no data on the effectiveness of individual control options in reducing public health risks. A highly effective option would be to stop or restrict cephalosporin usage in food animals. Decreasing total antimicrobial use is also of high priority. Implementation of measures to limit strain dissemination (increasing farm biosecurity, controls in animal trade, and other general postharvest controls) are also important.