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Antimicrobial Usage and Bacterial Resistance in the UK: 2007

by 5m Editor
14 April 2010, at 12:00am

The amount of antimicrobials sold per tonne of live weight of animal slaughtered for food in the UK has fallen from 80g in 2004 to 60g in 2007. This is one of the findings in <em>Overview of Antimicrobial Usage and Bacterial Resistance in Selected Human and Animal Pathogens in the UK: 2007</em>, which has recently been published by the Veterinary Medicines Directorate (VMD) and a number of other UK agencies.


Antimicrobial Use

As shown in the previous report the most commonly prescribed classes of antimicrobial agents in humans were ß-lactams, followed by macrolides and tetracyclines, accounting for 90 per cent of antimicrobials prescribed. Compared to figures shown in the previous report, overall antimicrobial prescribing in the community seems to be on the increase again after a number of initiatives in the 1990s promoting prudent antimicrobial prescribing were successful in reducing the number of prescriptions. However, during the same period the population of the United Kingdom has also increased by 1.1 million (1.9%) people.

The most commonly prescribed classes of antimicrobial agents used in veterinary medicine were tetracyclines followed by sulphonomides/trimethoprim and β-lactams. These three classes of antimicrobials account for 82 per cent of all veterinary sales. Sales of veterinary medicines have fallen since the figures published for 2004. The amount of antimicrobials sold per tonne of live weight of animal slaughtered for food has fallen from 0.08kg in 2004 to 0.06kg in 2007.

Campylobacter

Compared to the figures published in the previous report the overall resistance to ciprofloxacin and erythromycin in Campylobacter jejuni and C. coli isolated from people has increased sharply. Because of the small number of isolates referred for testing in 2007 these increases may not be representative.

No monitoring of Campylobacter susceptibility has been undertaken in animals in the UK between publication of the report covering data for 2004 and the end of 2006. A three-year statistically-based survey of broilers for Campylobacter was carried out between 2007 and 2009 but these data were not available at the time of writing this report.

Enterococcus spp

The main interest in enterococci continues to focus on resistance to glycopeptides. In humans, vancomycin resistance was higher in Enterococcus faecium (five to 35 per cent) than in E. faecalis (zero to four per cent).

No testing of enterococci has been undertaken in animals in the UK since publication of the report covering data for 2004. Enterococci were formerly considered during programmed surveillance for various bacteria in animals at abattoirs. Instead, in more recent years, a number of EU initiatives have focussed resource on various studies considering specific pathogens.

Escherichia coli

Escherichia coli were the most common bacterial pathogen causing bacteraemia in humans in England, Wales and Northern Ireland in 2007. Over half of the isolates were resistant to ampicillin or amoxicillin and resistance to ciprofloxacin was a significant problem with up to 27 per cent of isolates resistant. Cephalosporin resistance in E. coli from bacteraemia has continued to increase since the last report.

Resistance of E. coli to cephalosporins from veterinary isolates remained low in all four countries compared with 2004 but resistance to tetracyclines in pigs across the UK remained high. Generally, a variable pattern of resistance was seen for all food animal species to most antimicrobials in all four countries.

Escherichia coli O157

As antimicrobial resistance was not considered to be of significance in cases of human infection systematic resistance screening of E. coli O157 has been discontinued.

A small number of VTEC O157 isolates were found from animals in 2007. All E. coli O157 isolates from goats and horses were fully susceptible to all of the antimicrobials tested. Resistance to tetracyclines, sulphonamides and streptomycin was found in cattle (33 per cent) and sheep (50 per cent) isolates but these are based on very small numbers of samples and so may not be reflective of the overall national situation.

Extended-Spectrum Beta-Lactams (ESBLs)

The number of reports of cephalosporin resistance in E. coli isolates from human blood culture has increased since 2004 and probably reflects the spread of extended-spectrum β-lactamase (ESBL)-producing strains. Approximately 12 per cent of E. coli isolates were cephalosporin resistant in 2007 (compared to six per cent in 2004), with more than 75 per cent of these isolates being ESBL-producers, the most common types being CTX-M.

Of the 2,134 E. coli isolates recovered from bovine clinical diagnostic material in England and Wales in 2007, 25 were confirmed as ESBL-producers. The enzymes were all members of the CTX-M family. No CTX-M ESBL-producing E. coli were identified from veterinary samples from Scotland or Northern Ireland in 2007.

Salmonella

Salmonella Enteritidis was the most common serovar in cases of human infection in England and Wales, Scotland and Northern Ireland with S. Typhimurium the second most common in 2007. Resistance to more than one antimicrobial drug is common in S. Typhimurium. S. Enteritidis, particularly phage type 1, commonly has resistance to nalidixic acid.

Salmonella is one of the bacterial organisms that can cause disease in both humans and animals and infected animals can provide a source of infection for humans via the food chain. There can be differences in the prevalence of Salmonella in food-produced within the UK and imported food; human infections can also be related to foreign travel or contact with other infected humans. Untreated human sewage can also provide a source of Salmonella infection for animals. There was no resistance detected to amikacin, cefotaxime or ceftazidime in Salmonella isolates of animal origin from England and Wales. Similarly, no resistance was detected to cefotaxime or ciprofloxacin in animal Salmonella isolates from Northern Ireland or Scotland.

Staphylococcus aureus

Staphylococcus aureus is a common pathogen of humans being one of the two most common causes of bacteraemia. Surveillance of S. aureus bacteraemia is mandatory in the UK as a result of the increased incidence of methicillin-resistant S. aureus (MRSA) bacteraemia throughout the 1990s. However, the proportion of bacteraemias due to MRSA continued to decrease over the last few years in England and Northern Ireland. There were no reports of vancomycin or teicoplanin resistance in 2007.

Isolates of S. aureus from clinical disease in animals remained relatively less resistant to antimicrobials than their human counterparts. For example, more than 50 per cent of S. aureus from England, Wales and Northern Ireland were susceptible to penicillin and/or ampicillin.

Context

One of the objectives of this report is to draw together available information on key pathogens affecting humans and animals to aid understanding of resistance issues in the medical and veterinary sectors. These data originate from a variety of sources. As a consequence, different methods or break-points to detect resistance were often used and the data were collected over several time-frames and may relate to different geographical regions. Thus, as mentioned above, overall comparisons with the 2004 report are difficult to draw. It is hoped that better harmonisation across the UK in the way antimicrobial resistance is monitored and reported will be stimulated.

Notwithstanding these factors, it appears that for a number of bacterial species, there have been only limited changes in the degree of antimicrobial resistance reported in this report and the original report covering 2004.

Further Reading

- You can view the full report by clicking here.

April 2010