Longitudinal Farm Study of Extended-Spectrum β-Lactamase-Mediated Resistance

Abstract

Extended-spectrum ␤-lactamase (ESBL)-mediated resistance is of considerable importance in human medicine. Recently, such enzymes have been reported in bacteria from animals. We describe a longitudinal study of a dairy farm suffering calf scour with high mortality rates. In November 2004, two Escherichia coli isolates with resistance to a wide range of ␤-lactams (including amoxicillin-clavulanate and cefotaxime) were isolated from scouring calves. Testing by PCR and sequence analysis confirmed the isolates as being both bla CTX-M14/17 and bla TEM-35 (IRT-4) positive. They had indistinguishable plasmid and pulsed-field gel electrophoresis (PFGE) profiles. Transferability studies demonstrated that bla CTX-M was located on a conjugative 65-MDa IncK plasmid. Following a farm visit in December 2004, 31/48 calves and 2/60 cows were positive for E. coli with bla CTX-M . Also, 5/48 calf and 28/60 cow samples yielded bla CTX -and bla TEM -negative E. coli isolates that were resistant to cefotaxime, and sequence analysis confirmed that these presented mutations in the promoter region of the chromosomal ampC gene. Fingerprinting showed 11 different PFGE types (seven in bla CTX-Mpositive isolates). Six different PFGE clones conjugated the same bla CTX-M -positive IncK plasmid. One clone carried a different-sized, bla CTX-M -positive, transformable plasmid. This is the first report of bla CTX-M from livestock in the United Kingdom, and this report demonstrates the complexity of ESBL epidemiology. Results indicate that horizontal plasmid transfer between strains as well as horizontal gene transfer between plasmids have contributed to the spread of resistance. We have also shown that some clones can persist for months, suggesting that clonal spread also contributes to the perpetuation of resistance.Cefotaximases (CTX-M) are class A ␤-lactamases produced by a wide range of bacteria of clinical significance and in general present higher levels of hydrolytic activity against cefotaxime than against ceftazidime. CTX-M enzymes comprise a genetically diverse (five groups designated 1, 2, 8, 9, and 25 have been described) and rapidly growing family. These are the predominant extended-spectrum ␤-lactamases (ESBL) in human infections in parts of Eastern Europe, South America, and Japan. In the United Kingdom, the first report of a CTX-M enzyme was in a human clinical isolate of Klebsiella oxytoca with bla CTX-M9 in 2000 (1). Since then, CTX-M-producing Escherichia coli has emerged as a significant and developing problem, occurring in patients in the community as well as in those with recent hospital contact (16,19).In spite of this human situation, worldwide, there have been only a few recent reports of CTX-M-producing bacteria in animals (3,4,10,11,25,29). It is unclear whether it is primarily human or veterinary use of antibiotics that has provided the selective pressures necessary for this situation. In a recent letter, we described the first reported isolation of CTX-Mproducing E. coli from cattle in the United Kingdom. These resist...

Scientific Opinion on the public health risks of bacterial strains producing extended-spectrum β-lactamases and/or AmpC β-lactamases in food and food-producing animals

“…These plasmids can be considered as "epidemic associated with the emergence of specific ESBL or AmpC gene variants. For instance, the IncA/C plasmids were associated with the emergence of bla CMY-2 in the USA and UK Randall et al, 2011), the IncL/M plasmids were associated to the spread of bla CTX-M-3 in European Eastern countries (Golebiewski et al, 2007), while IncK plasmids carrying bla CTX-M-14 have become diffused in Spain and UK (Cottell et al, 2011;Liebana et al, 2006;Valverde et al, 2009). …”

Molecular characterization of extended-spectrum β-lactamase-producing Shigella isolates from humans in South Africa, 2003–2009

“…The majority of the ESBL-producing isolates harboured the bla CTX-M-15 gene, which is carried on plasmids and can be disseminated via horizontal gene transfer to other Gramnegative pathogens (Carattoli, 2009;Liebana et al, 2006). In the current study, a series of ESBL-producing Shigella isolates from South Africa have been identified, which, although comprising ,1 % of all the isolates obtained for surveillance, are clinically relevant as they represent a challenge in disease management and patient treatment.…”

“…ESBL (bla TEM , bla SHV and bla CTX-M ) and AmpC b-lactamase (bla CMY ) genotypes were determined using PCR as described previously (Essack et al, 2001;Liebana et al, 2006;Rankin et al, 2005). Positive controls for PCR included the following strains: Klebsiella pneumoniae ATCC 51503, K. pneumoniae ATCC 700603 and K. pneumoniae D-17.…”

Genetic heterogeneity of CTX-M type extended-spectrum β-lactamase producing Escherichia coli strains from diverse sources in Saudi Arabia

“…CTX-M-type ESBLs have also recently become predominant among ESBLs-positive E. coli [17,18]. Studies from USA, Europe and Asia have shown the recovery of bla CTX-M group from farm livestock with increasing frequency [19][20][21]. The ESBLs-CTX-M type was also reported in faecal samples of broilers [22], and healthy pets [23].…”