E. van Duijkeren

Editorial: Assessing the antimicrobial susceptibility of bacteria obtained from animals

The accurate performance of antimicrobial susceptibility testing of bacteria from animal sources and the correct presentation of the results is a complex matter. A review of the published literature revealed a number of recurring errors with regard to methodology, quality control, appropriate interpretive criteria, and calculation of MIC(50) and MIC(90) values. Although more subjective, there is also no consensus regarding the definition of multiresistance. This Editorial is intended to provide guidance to authors on how to avoid these frequently detected shortcomings.

Occurrence and characteristics of extended-spectrum-β-lactamase- and AmpC-producing clinical isolates derived from companion animals and horses

OBJECTIVES To investigate the occurrence and characteristics of extended-spectrum β-lactamase (ESBL)- and AmpC-producing Enterobacteriaceae isolates in clinical samples of companion animals and horses and compare the results with ESBL/AmpC-producing isolates described in humans. METHODS Between October 2007 and August 2009, 2700 Enterobacteriaceae derived from clinical infections in companion animals and horses were collected. Isolates displaying inhibition zones of ≤ 25 mm for ceftiofur and/or cefquinome by disc diffusion were included. ESBL/AmpC production was confirmed by combination disc tests. The presence of resistance genes was identified by microarray, PCR and sequencing, Escherichia coli genotypes by multilocus sequence typing and antimicrobial susceptibility by broth microdilution. RESULTS Sixty-five isolates from dogs (n = 38), cats (n = 14), horses (n = 12) and a turtle were included. Six Enterobacteriaceae species were observed, mostly derived from urinary tract infections (n = 32). All except 10 isolates tested resistant to cefotaxime and ceftazidime by broth microdilution using clinical breakpoints. ESBL/AmpC genes observed were bla(CTX-M-1, -2, -9, -14, -15,) bla(TEM-52), bla(CMY-2) and bla(CMY-)(39). bla(CTX-M-1) was predominant (n = 17). bla(CTX-M-9) occurred in combination with qnrA1 in 3 of the 11 Enterobacter cloacae isolates. Twenty-eight different E. coli sequence types (STs) were found. E. coli carrying bla(CTX-M-1) belonged to 13 STs of which 3 were previously described in Dutch poultry and patients. CONCLUSIONS This is the first study among a large collection of Dutch companion animals and horses characterizing ESBL/AmpC-producing isolates. A similarity in resistance genes and E. coli STs among these isolates and isolates from Dutch poultry and humans may suggest exchange of resistance between different reservoirs.

Assessing the antimicrobial susceptibility of bacteria obtained from animals

In recent years, antimicrobial resistance in bacteria of animal origin, including food-producing animals, pet and companion animals, fish and other aquatic animals as well as wild animals, has gained particular attention. Consequently, an increasing number of studies that include antimicrobial susceptibility testing have been published. However, an analysis of recently published articles revealed a number of frequently occurring shortcomings, which may have an impact either directly on the quality of the results obtained or on the conclusions drawn. This editorial is intended to highlight the major pitfalls and provide guidance for authors, and reviewers on the correct performance of antimicrobial susceptibility testing as well as the presentation of the obtained results and the proper comparison of data from different studies.

Serotype and Phage Type Distribution of Salmonella Strains Isolated from Humans, Cattle, Pigs, and Chickens in The Netherlands from 1984 to 2001

ABSTRACT We studied serotypes and phage types of Salmonella strains isolated from humans and animals in The Netherlands over the period 1984 to 2001. All human strains (n = 59,168) were clinical isolates. The animal strains (n = 65,567) were from clinical and nonclinical infections. All isolates were serotyped, and Salmonella enterica serovar Typhimurium and serovar Enteritidis strains were further phage typed. The most prevalent serotypes were as follows: in humans, serovars Typhimurium and Enteritidis; in cattle, serovars Typhimurium and Dublin; in pigs, serovar Typhimurium; and in chickens, serovars Enteritidis, Infantis, and Typhimurium. Serovar Enteritidis phage type 4 (pt 4) was the most common phage type in humans and chickens. Serovar Typhimurium pt 510 was the most prevalent serovar Typhimurium phage type in humans and pigs, pt 200 was the most prevalent serovar Typhimurium phage type in cattle, and pt 150 was the most prevalent serovar Typhimurium phage type in chickens. Analysis of the distribution of sero- and phage types during the study period indicated that types shifted over time in humans and animals. Serovar Typhimurium DT 104 emerged in 1991 in humans, cattle, pigs, and chickens and became the most common serovar Typhimurium phage type in 2001. In general, similar sero- and phage types were found in humans and animals, although distinct types were more common in animals. Between the animal species, the sero- and phage type distributions varied considerably.

Transmission of methicillin-resistant Staphylococcus pseudintermedius between infected dogs and cats and contact pets, humans and the environment in households and veterinary clinics

The objective of this study was to investigate the prevalence of methicillin-resistant Staphylococcus pseudintermedius (MRSP) in people, pets and the environment in households with a pet with a clinical MRSP-infection within the past year. Personnel and the environment at veterinary clinics were also screened. Nasal swabs (humans), nasal and perineal swabs (pets) and environmental wipes were examined using selective culturing. Twenty households were enrolled; 10/20 index cases still had clinical signs of infection at the start of the study and all were MRSP-positive. Of the remaining 10 index cases five were MRSP-positive in nasal and/or perineal samples. Five of 14 (36%) contact dogs and four of 13 (31%) contact cats were found MRSP-positive. In the households with an index case with clinical signs of infection 6/7 (86%) contact animals were MRSP-positive. MRSP was cultured from 2/45 (4%) human nasal samples. Domestic contamination was widespread as positive samples were found in 70% of the households and 44% of all environmental samples were MRSP-positive. In all but one of these MRSP-positive households the index case was still MRSP positive. Among the personnel in veterinary clinics 4/141 (3%) were MRSP-positive. MRSP was cultured from 31/200 environmental samples in 7/13 clinics at the first sampling and in 3/6 clinics the environment remained MRSP-positive after cleaning and disinfection indicating that current cleaning procedures often were unable to eliminate MRSP. These results show that transmission of MRSP between infected or colonized dogs and cats and healthy people does occur but is relatively uncommon, while transmission to contact pets occurs frequently, especially when the index case still has clinical signs of MRSP-infection.

Antimicrobial Susceptibilities of Salmonella Strains Isolated from Humans, Cattle, Pigs, and Chickens in The Netherlands from 1984 to 2001

ABSTRACT We monitored antimicrobial susceptibility data for Salmonella strains isolated from humans, cattle, pigs, and chickens in The Netherlands from 1984 to 2001 in order to provide insight into the dynamics of resistance over time. The strains were tested for their susceptibilities to seven antimicrobial agents by the agar diffusion method. Resistance was most common in Salmonella enterica subsp. enterica serovar Typhimurium. Among the strains from humans, pigs, and chickens, it was found that the level of resistance of serovar Typhimurium strains to tetracycline, ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole increased from 1984 to 2001. This increase could be attributed to the emergence of multidrug-resistant serovar Typhimurium DT 104. Among the strains from cattle, it was found that the level of resistance of serovar Typhimurium strains, which was already very high in the 1980s, declined during the study period to the same levels as those for the strains from the other species from 1996 to 2001. Serovar Enteritidis isolates remained susceptible during the entire survey period. Among serovar Paratyphi B variation Java strains isolated from chickens, resistance to furazolidone, flumequine, trimethoprim-sulfamethoxazole, and ampicillin emerged, although furazolidone was not used after 1990. Together, the data indicate that the levels and patterns of resistance differed considerably between Salmonella serovars isolated from one host species.

Reflection paper on MRSA in food-producing and companion animals: epidemiology and control options for human and animal health

The scope of this reflection paper was to review the latest research on the risk of MRSA infection and colonization in animals. Attention focused on occurrence, risk factors for colonization and infection, and human contact hazard for livestock, horses, and companion animals. Whereas the clonal relationship between MRSA strains of CC398 is straightforward in livestock this is less obvious in horses. Small companion animals typically share MRSA strains that seem to exchange with a human reservoir. Management and therapeutic options have been suggested for livestock, horses, companion animals, as well as instructions on safety measures for persons in contact with animals. Conclusions were drawn with emphasis on future research activities, especially to confirm the apparent evolution of the organism and to demonstrate efficiency of control strategies.

Transmission of a Panton-Valentine Leucocidin-Positive, Methicillin-Resistant Staphylococcus aureus Strain between Humans and a Dog

ABSTRACT Panton-Valentine leucocidin-positive methicillin-resistant Staphylococcus aureus (MRSA) strains with identical resistance patterns were cultured from recurrent infections of a 51-year-old patient, her healthy husband, son, and dog, and pulsed-field gel electrophoresis showed that all MRSA strains were indistinguishable.

Multilocus Sequence Typing for Characterization of Staphylococcus pseudintermedius

ABSTRACT Staphylococcus pseudintermedius is an opportunistic pathogen in dogs. Four housekeeping genes with allelic polymorphisms were identified and used to develop an expanded multilocus sequence typing (MLST) scheme. The new seven-locus technique shows S. pseudintermedius to have greater genetic diversity than previous methods and discriminates more isolates based upon host origin.

Extended-spectrum and AmpC β-lactamase-producing Escherichia coli in broilers and people living and/or working on broiler farms: prevalence, risk factors and molecular characteristics

OBJECTIVES The objectives of this study were to: estimate the prevalence of extended-spectrum β-lactamase (ESBL)- and AmpC β-lactamase-producing Escherichia coli carriage among broiler farmers, their family members and employees; identify and quantify risk factors for carriage, with an emphasis on contact with live broilers; and compare isolates from humans and broilers within farms with respect to molecular characteristics to gain insight into transmission routes. METHODS A cross-sectional prevalence study was conducted on 50 randomly selected Dutch broiler farms. Cloacal swabs were taken from 20 randomly chosen broilers. Faecal swabs were returned by 141 individuals living and/or working on 47 farms. ESBL/AmpC-producing E. coli were isolated and, for selected isolates, phylogenetic groups, plasmids and sequence types were determined. Questionnaires were used for risk factor analysis. RESULTS All sampled farms were positive, with 96.4% positive pooled broiler samples. The human prevalence was 19.1%, with 14.3% and 27.1% among individuals having a low and a high degree of contact with live broilers, respectively. Five pairs of human-broiler isolates had identical genes, plasmid families and E. coli sequence types, showing clonal transmission. Furthermore, similar ESBL/AmpC genes on the same plasmid families in different E. coli sequence types in humans and broilers hinted at horizontal gene transfer. CONCLUSIONS The prevalence among people on broiler farms was higher than in previous studies involving patients and the general population. Furthermore, an increased risk of carriage was shown among individuals having a high degree of contact with live broilers. The (relative) contribution of transmission routes that might play a role in the dissemination of ESBL/AmpC-encoding resistance genes to humans on broiler farms should be pursued in future studies.