The project "Antibiotic resistance in bacteria of animal origin – II" (ARBAO-II) was funded by the European Union (FAIR5-QLK2-2002-01146) for the period 2003–2005, with the aim to establish a continuous monitoring of antimicrobial susceptibility among veterinary laboratories in European countries based on validated and harmonised methodologies. Available summary data of the susceptibility testing of the bacterial pathogens from the different laboratories were collected.

Objectives: The aim of this study was to investigate the genetic background for streptomycin resistance in Escherichia coli and perform analysis of the MICs in relation to genetic background. Methods: The 136 strains investigated, with streptomycin MICs of ≥16 mg/L, originated from meat and meat products and were collected within the frame of the Norwegian monitoring programme for antimicrobial resistance in bacteria from feed, food and animals (NORM-VET). PCR was carried out for detection of the streptomycin resistance genes strA-strB and the integron-associated aadA gene cassettes. Results: The strA-strB genes and/or an aadA gene cassette were detected in 110 of the 136 (80.9%) strains investigated. The strA-strB genes were the most prevalent, and were detected in 90 strains. The aadA gene cassettes were detected in 29 strains, and nine strains harboured both the strA-strB genes and an aadA gene cassette. The distribution of MICs differed considerably between isolates harbouring the strA-strB genes (solely) (MIC₅₀=128 mg/L) and isolates harbouring an aadA gene cassette (solely) (MIC₅₀=16 mg/L). Strains harbouring both the strA-strB genes and an aadA gene cassette had higher streptomycin MICs than those harbouring either alone. Conclusions: The distribution of streptomycin MICs in E. coli can be greatly influenced by the genes encoding resistance to streptomycin. The strA-strB genes are probably involved in conferring high-level resistance to streptomycin, whereas the opposite seems to be the case for the aadA gene cassettes. The low-level streptomycin resistance, caused by the presence of aadA gene cassettes in integrons, represents an obstacle in classifying E. coli as susceptible or resistant to streptomycin. Furthermore, the determination of an epidemiological cut-off value for surveillance purposes is also complicated by dissemination of integrons containing the aadA cassettes.

Objectives: To investigate the distribution of, associations between and the transferability of antimicrobial resistance genes in resistant Escherichia coli strains isolated from Norwegian meat and meat products. Methods: The 241 strains investigated were collected within the frame of the Norwegian monitoring programme for antimicrobial resistance in bacteria from feed, food and animals (NORM-VET) during the years 2000–2003. PCR was carried out for detection of resistance genes. Conjugation experiments were carried out with the resistant isolates from meat as donor strains and E. coli DH5α as the recipient strain. Statistical analyses were performed with the SAS-PC-System version 9.1 for Windows. Results: Resistance genes common in pathogenic E. coli were frequently found among the isolates investigated. Strains harbouring several genes encoding resistance to the same antimicrobial agent were significantly (P < 0.0001) more frequently multiresistant than others. Strong positive associations were found between the tet(A) determinant and the genetic elements sul1, dfrA1 and aadA1. Negative associations were found between resistance genes encoding resistance to the same antimicrobial agent: tet(A)/tet(B), sul1/sul2 and strA-strB/aadA1. The resistance genes were successfully transferred from 38% of the isolates. The transfer was more frequent from resistant isolates harbouring class 1 integrons (P < 0.001). Conclusions: Acquired resistance played a major role in conferring resistance among the isolates investigated. The possibility of transferring resistance increases both by increased multiresistance and by the presence of class 1 integrons. The conjugation experiments suggest that tet(A) and class 1 integrons are often located on the same conjugative plasmid.

Objectives: The aim of the study was to investigate the prevalence of integrons and to characterize inserted gene cassettes in Escherichia coli isolated from meat and meat products of Norwegian origin. Methods: The strains investigated (n = 241 resistant out of 944 investigated) were collected within the frame of the Norwegian monitoring programme for antimicrobial resistance in bacteria from feed, food and animals (NORM-VET) during the years 2000–2003. PCR and DNA sequencing were used for detection of the integrase genes and gene cassettes within the integrons. Results: Integrons were detected in 43 (18%) of the 241 resistant isolates. Class 1 integrons were detected in 29 (12%) strains and class 2 integrons were detected in 14 (6%) strains. Ten different gene cassettes were detected: dfrA1, dfr2a, dfrA12, aadA1, aadA2, catB2, oxa-30, sat, sat1 and orfF. The dfrA1 + aadA1 combination was the most prevalent cassette combination, detected in 12 of 29 class 1 integrons. Twelve (of 14) class 2 integrons contained a cassette area consistent with that on Tn7, the remaining two contained the cassettes sat + sat1 + aadA1. Nearly one-third of the class 1 integrons (9 of 29) lacked the sul1 gene. Ten gene cassettes (one dfr2a, two catB2 and seven aadA1) were expressed at levels below breakpoint values normally used to classify strains as resistant. Conclusions: Integrons of class 1 or 2 were present in ∼18% of the resistant E. coli strains investigated. Certain cassette combinations in class 1 integrons seem to be more widespread than others, like the dfrA1 + aadA1. Low-level expression of antimicrobial resistance, caused by the expression of certain gene cassettes in some integrons represents an obstacle in classifying strains as susceptible or resistant.

The aim of this study was to investigate the clonal epidemiology of methicillin-resistant Staphylococcus pseudintermedius (MRSP) isolates from dogs in Norway and to evaluate the antimicrobial resistance patterns and determine the biofilm-forming abilities of the isolates. All MRSP index isolates from each MRSP-positive dog detected in Norway until June 2011 were included (n = 23). The MICs of antimicrobial agents were determined by the VetMIC™ microdilution method. The genetic relationship between the isolates was investigated by multilocus sequence typing (MLST) and PFGE. The isolates' abilities to form biofilm on polystyrene were studied. The MRSP isolates investigated grouped into 11 different sequence types (STs); MRSP ST106 occurred most frequently. There were a relatively smaller number of isolates belonging to ST71, the largely predominant ST in Europe. Isolates belonging to ST71 had a significantly greater ability to produce biofilm compared with the other isolates, and especially compared with MRSP ST106. A heterogeneous clonal distribution was observed among MRSP from dogs in Norway. As opposed to previous findings in Europe, MRSP clones other than ST71 have spread in Norway, such as MRSP ST106. The results also show that MRSP ST71 is possibly a good biofilm producer, and this may in turn be a contributing factor to the nosocomial character of MRSP ST71.

The project "Antibiotic resistance in bacteria of animal origin – II" (ARBAO-II) was funded by the European Union (FAIR5-QLK2-2002-01146) for the period 2003–05. The aim of this project was to establish a program for the continuous monitoring of antimicrobial susceptibility of pathogenic and indicator bacteria from food animals using validated and harmonised methodologies. In this report the first data on the occurrence of antimicrobial resistance among bacteria causing infections in pigs are reported.