Multidrug resistant, extended spectrum β-lactamase (ESBL)-producing Escherichia coli isolated from a dairy farm

Escherichia coli strains were isolated from a single dairy farm as a sentinel organism for the persistence of antibiotic resistance genes in the farm environment. Selective microbiological media were used to isolate 126 E. coli isolates from slurry and faeces samples from different farm areas. Antibiotic resistance profiling for 17 antibiotics (seven antibiotic classes), showed 57.9% of the isolates were resistant to between 3 and 15 antibiotics. The highest frequency of resistance was to ampicillin (56.3%), and the lowest to imipenem (1.6%), which appeared to be an unstable phenotype and was subsequently lost. Extended spectrum beta-lactamase resistance (ESBL) was detected in 53 isolates and blaCTX-M, blaTEM and blaOXA genes were detected by PCR in twelve, four and two strains, respectively. Phenotypically most isolates showing resistance to cephalosporins were AmpC rather than ESBL, a number of isolates having both activities. Phenotypic resistance patterns suggested co-acquisition of some resistance genes within subsets of the isolates. Genotyping using ERIC PCR demonstrated these were not clonal, and therefore co-resistance may be associated with mobile genetic elements. These data show a snapshot of diverse resistance genes present in the E. coli population reservoir, including resistance to historically used antibiotics as well as cephalosporins in contemporary use

Survival in amoeba: a major selection pressure on the presence of bacterial copper and zinc resistance determinants?: identification of a "copper pathogenicity island"

The presence of metal resistance determinants in bacteria usually is attributed to geological or anthropogenic metal contamination in different environments or associated with the use of antimicrobial metals in human healthcare or in agriculture. While this is certainly true, we hypothesize that protozoan predation and macrophage killing are also responsible for selection of copper/zinc resistance genes in bacteria. In this review, we outline evidence supporting this hypothesis, as well as highlight the correlation between metal resistance and pathogenicity in bacteria. In addition, we introduce and characterize the "copper pathogenicity island" identified in Escherichia coli and Salmonella strains isolated from copper- and zinc-fed Danish pigs

Response of Cupriavidus metallidurans CH34 to metals

Cupriavidus metallidurans CH34 displays resistance to a plethora of metals. Its response and underlying genetic determinants are dissected and detailed metal by metal (from arsenic to zinc). An important role for its megaplasmids pMOL28 and pMOL30 is shown, with high level resistance to cadmium, chromate, cobalt, copper, mercury, nickel, lead and zinc mediated by well-known genes for detoxification often accompanied by other functions linked to acute or chronic stress. Nevertheless, metal resistance determinants are also found on the chromid (e.g. to chromate, copper and zinc) as well as on a large genomic island integrated in the chromosome (e.g. to cadmium, lead and mercury), even the core genome participates in certain responses such as to gold or selenium. Next, we summarized the environmental applications, which were developed based on the knowledge gained by studying these different determinants, and in particular biosensors and soil and water bioremediation. Finally, the general transcriptional response of C. metallidurans to sixteen different metals supplied at different concentrations (including acute stress) is discussed within the framework of its intricate regulatory network