The BfT-GermVet monitoring program aims and basics

Transcription

1 Berl. Münch. Tierärztl. Wochenschr. 120, Heft 9/10, (2007) 357 Berl. Münch. Tierärztl. Wochenschr. 120, (2007) DOI / Schlütersche Verlagsgesellschaft mbh & Co. KG ISSN Korrespondierender Autor: Eingegangen: Angenommen: Institut für Tierzucht, Bundesforschungsanstalt für Landwirtschaft, Neustadt- Mariensee 2 Institut für Medizinische Mikrobiologie, Infektions- und Seuchenmedizin, Tierärztliche Fakultät, Ludwig-Maximilians-Universität München 3 Institut für Mikrobiologie und Tierseuchen, Fachbereich Veterinärmedizin, Freie Universität Berlin 4 Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL), Berlin The BfT-GermVet monitoring program aims and basics Das BfT-GermVet Monitoringprogramm Ziele und Grundlagen Stefan Schwarz 1, Eva Ales ík 2, Mirjam Grobbel 3, Antina Lübke-Becker 3, Jürgen Wallmann 4, Christiane Werckenthin 2, Lothar H. Wieler 3 Summary To determine the current status of antimicrobial susceptibility of bacterial pathogens from animals in Germany, the BfT-GermVet monitoring program was initiated as a complementary program to the German national monitoring program GERM-Vet conducted by the Federal Office of Consumer Protection and Food Safety (BVL). In the BfT-GermVet program, a total of 1,626 bacterial strains, obtained during a 27-month period (01/ /2006) from 31 indications, was screened for susceptibility against 22 antimicrobial agents and two combinations of antimicrobial agents. Selected bacteria were additionally tested for their susceptibility against additional three combinations of antimicrobial agents and the corresponding single substances. This paper describes the overall aims and the structure of the program with particular reference to the sampling strategy, the methodology for susceptibility testing and the interpretive criteria used for evaluation of the results. Keywords: in-vitro susceptibility testing, antimicrobial agents, sampling strategy, interpretive criteria Zusammenfassung Das Monitoringprogramm BfT-GermVet wurde als Komplementärprogramm zum Nationalen Resistenzmonitoringprogramm GERM-Vet des Bundesamts für Verbraucherschutz und Lebensmittelsicherheit (BVL) initiiert, um so den derzeitigen Empfindlichkeitsstatus bakterieller Infektionserreger von Tieren gegenüber antimikrobiellen Wirkstoffen in Deutschland möglichst umfassend zu dokumentieren. Im BfT-GermVet Programm wurden insgesamt 1626 Bakterienstämme, die in einem 27-monatigen Zeitraum (01/ /2006) in ganz Deutschland von 31 Indikationen gesammelt wurden, hinsichtlich ihrer Empfindlichkeit gegenüber 22 antimikrobiellen Wirkstoffen und zwei Wirkstoffkombinationen untersucht. Ausgewählte Erreger wurden zusätzlich gegenüber drei weiteren Wirkstoffkombinationen und den jeweiligen Einzelsubstanzen getestet. Diese Publikation beschreibt die Ziele und die Struktur des BfT-GermVet Programms, wobei Schwerpunkte auf die Darstellung der Probensammlung, die Methodik der Empfindlichkeitsprüfung sowie die angewendeten Grenzwerte zur Bewertung der ermittelten Empfindlichkeitsdaten gelegt wurden. Schlüsselwörter: In-vitro-Empfindlichkeitsbestimmung, Antibiotika, Probensammlungsplan, Grenzwerte U.S. Copyright Clearance Center Code Statement: /2007/ $15.00/0

2 358 Berl. Münch. Tierärztl. Wochenschr. 120, Heft 9/10, (2007) Project description and rationale In contrast to several other European countries, like Denmark, Sweden, and Norway, there was no national program for monitoring the in-vitro susceptibility of bacterial pathogens from animals against antimicrobial agents in Germany until the year In 2001, Germany started a pilot study (Wallmann et al., 2003) which quickly became the GERM-Vet program conducted by the Federal Office of Consumer Protection and Food Safety (Bundesamt für Verbraucherschutz und Lebensmittelsicherheit, BVL) in Berlin (Wallmann et al., 2004). In the GERM-Vet program, a wide variety of Gram-positive and Gram-negative bacterial pathogens isolated from different clinical presentations of infections of the food-producing animal species cattle, swine, and poultry are investigated for their in-vitro susceptibility to antimicrobial agents. The data obtained from this monitoring program are intended to provide a detailed description of the current susceptibility status of the respective bacterial pathogens in Germany. Over the years, this program will also provide data that may show potential temporal variations in the susceptibility status of the pathogens. In addition to the bacteria monitored in the GERM- Vet program, there are numerous bacterial pathogens from other indications and animal species for which data on the susceptibility status are required. Especially for bacteria causing infections in the animal species horse, dog and cat, reliable and representative susceptibility data are missing on the national level. Thus, the Federation for Animal Health (Bundesverband für Tiergesundheit e.v., BfT) decided to start a nation-wide monitoring program which should be a complement to the GERM- Vet program. For this, the same methodology for susceptibility testing and very similar criteria for probe sampling as used in the GERM-Vet program were applied. This second program, designated BfT-GermVet, was initiated in late 2003 and was realized as a joint effort involving the following four institutions: (i) the Institute of Animal Breeding, Federal Agricultural Research Centre (FAL) [Institut für Tierzucht der Bundesforschungsanstalt für Landwirtschaft (FAL)], (ii) the Institute of Microbiology and Epizootics, Free University Berlin [Institut für Mikrobiologie und Tierseuchen des Fachbereiches Veterinärmedizin der Freien Universität (FU) Berlin], (iii) Institute for Medical Microbiology, Infectious and Epidemic Diseases, Ludwig-Maximilians University, Munich [Institut für Medizinische Mikrobiologie, Infektions- und Seuchenmedizin der Tierärztlichen Fakultät der Ludwig-Maximilians-Universität (LMU) München], and (iv) the Federal Office of Consumer Protection and Food Safety, Berlin [Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL), Berlin]. In contrast to the GERM-Vet program, which runs on an annual basis, the BfT-GermVet program was designed as a single study with an extended sampling period of 27 months [January 2004 March 2006]. TABLE 1: Bacteria investigated in the BfT-GermVet program listed by animal species and indications. Animal species/indication Indication Bacteria investigated No. of strains Antibiotic pretreatment no. tested yes no unknown Cattle 85 urinary / genital tract 1 Escherichia coli Arcanobacterium pyogenes omphalitis / septicemia 3 Arcanobacterium pyogenes Swine 322 urinary / genital tract (incl. mastitis 4 Escherichia coli metritis agalactia syndrome) 5 coagulase-positive Staphylococcus spp (incl. Staphylococcus hyicus) 6 ß-haemolytic Streptococcus spp CNS / musculoskeletal system 7 Streptococcus suis Arcanobacterium pyogenes skin 9 coagulase-positive Staphylococcus spp (incl. Staphylococcus hyicus) skin / respiratory tract 10 Erysipelothrix rhusiopathiae 2 2 Horse 326 respiratory tract 11 Streptococcus equi Actinobacillus equuli genital tract 13 Escherichia coli Klebsiella spp ß-haemolytic Streptococcus spp Dog and Cat 893 respiratory tract 16 coagulase-positive Staphylococcus spp ß-haemolytic Streptococcus spp Pasteurella multocida Bordetella bronchiseptica Escherichia coli urinary / genital tract 21 Escherichia coli Klebsiella spp Proteus spp Pseudomonas aeruginosa ß-haemolytic Streptococcus spp skin / ear / mouth 26 coagulase-positive Staphylococcus spp ß-haemolytic Streptococcus spp Pasteurella multocida Proteus spp Pseudomonas aeruginosa gastrointestinal tract 31 Escherichia coli

3 Berl. Münch. Tierärztl. Wochenschr. 120, Heft 9/10, (2007) 359 Study design Bacteria and indications tested Bacteria from 31 indications were investigated for their in-vitro susceptibility (Tab. 1). The decision, which bacteria from which clinical presentations should be sampled, was mainly based on an estimate of the overall relevance of these bacteria/indications in veterinary routine diagnostics and the relevance of antimicrobial therapy in the control of the respective disease. Most of these indications were chosen from the three animal species horse, dog and cat. Selected relevant indications of the foodproducing animal species cattle and swine were also included as a complement to the GERM-Vet program. Sample size Currently, the total number of all bacterial pathogens from the 31 indications monitored in the BfT-GermVet program is a figure of unknown magnitude in the respective animal populations in Germany. Thus, representative samples must be collected in order to draw conclusions on the susceptibility status of the respective total bacterial entity. In this regard, the sample size is a critical parameter and has to be chosen with care. It must allow the detection of a certain resistance trait with a sufficiently high probability. The preciseness, by which the presence of a given resistance trait within a bacterial population can be estimated, depends strongly on the prevalence of this trait. As a consequence, the sample size required for a reliable detection of a certain resistance trait also depends mainly on the prevalence of this resistance trait in the entire population. The smaller the sample size, the larger will be the impreciseness of the approximation. The fact, that no reliable data on any resistance prevalence were available for virtually all bacteria and indications under investigation in the BfT-GermVet program, resulted in a certain imponderability in the estimation of the adequate sample sizes. Thus, an estimation of the sufficient sample size based on comparative data from other studies was not possible. Moreover, it was unknown by which frequency bacterial strains from the 31 indications were isolated at all during the course of routine diagnostics in Germany. During the planning phase, the members of the BfT- GermVet consortium agreed that a sample size with a significance level of M = 0.05 and a power of 1 N = 0.80 should be used. Based on sample size calculations previously done for the GERM-Vet program of the BVL (Wallmann et al., 2003), at least bacterial strains per indication/animal species should be isolated and included in the BfT-GermVet program during the entire sampling period. These bacterial strains should fulfil the quality control criteria as requested for strains to be included in the GERM-Vet program. Probe sampling plan and quality control criteria In agreement with the requirements for inclusion in the GERM-Vet program, all bacteria obtained from routine diagnostics and intended for inclusion in the BfT-Germ- Vet program should be available as pure cultures. Moreover, these bacteria should be differentiated to the species level. All background data concerning the animal source, geographical origin, organ system affected, antibiotic pre-treatment, etc. were recorded electronically and stored in a database. It would not have been possible to acquire a sufficiently high number of bacterial strains from the 31 indi- TABLE 2: Antimicrobial agents and combinations of antimicrobial agents tested. Class of antimicrobial Representatives of the Test range (µg/ml) Result applicable agents different classes also to the agents ß-Lactams (Penicillins) Penicillin G Benzathinpenicillin, Benzylpenicillin Procain, Benzylpenicillin Ampicillin Amoxicillin Oxacillin + 2% NaCl Cloxacillin, Nafcillin ß-Lactams (Penicillin + ß- Amoxicillin/clavulanic acid (2/1) 0.015/ /16 lactamase inhibitor) ß-Lactams Cephalothin Cephapirin, Cefadroxil, Cephalexin, Cefazolin, (Cephalosporins) Cephacetril Cefazolin [separate testing of Gram-negative bacteria recommended by CLSI] Cefoperazone Ceftiofur Cefquinom Tetracyclines Tetracycline Oxytetracycline, Chlortetracycline, Doxycycline Macrolides Erythromycin Tilmicosin Spiramycin Tylosin Tulathromycin Lincosamides Clindamycin Lincomycin Aminoglycosides Gentamicin Neomycin Framycetin Aminocyclitols Spectinomycin Phenicols Chloramphenicol Florfenicol Fluoroquinolones Enrofloxacin Marbofloxacin, Danofloxacin, Orbifloxacin, Difloxacin, Ibafloxacin Polypeptides Colistin Polymyxin B Sulfonamides Sulfamethoxazole Sulfadimidine, Sulfaclozine, Sulfadimethoxine, Sulfadiazine, Sulfamethoxypyridazin, Sulfamerizine, Sulfathiazole Potentiated sulfonamides Trimethoprim/sulfamethoxazole 0.015/0.3 32/608 Trimethoprim/sulfamerizine, (1/19) Trimethoprim/sulfadoxine, Trimethoprim/sulfadimidine

4 360 Berl. Münch. Tierärztl. Wochenschr. 120, Heft 9/10, (2007) cations within the given time frame without the substantial support provided by numerous diagnostic laboratories all over Germany, including university diagnostic laboratories, diagnostic laboratories of the various federal states in Germany, diagnostic laboratories associated with animal health agencies, as well as private diagnostic laboratories. To ensure that the bacterial strains were representative for the population, a probe sampling plan was sent to all those diagnostic laboratories which contributed strains to this program. This probe sampling plan clearly defined which strains should be provided: (i) Only bacterial strains from animals suffering from acute clinical infections should be included. (ii) Animals must not have been treated with antimicrobial agents in the four weeks prior to probe sampling. (iii) Not more than two bacterial strains of the same species from the same herd (as checked by farm no./bill no. for strains from cattle and swine or postal code of the city of origin for strains from dogs, cats or horses) were allowed. (iv) If more than one suitable isolate per herd was available, only the first isolate per calendar week should be selected. In some indications, a considerable number of bacterial strains with either unknown or positively confirmed pretreatment status were provided. In the latter case, reliable data on the antimicrobial agents applied were only available in rare cases. Such strains were also maintained in the BfT-GermVet collection and tested if necessary (see: Implementation of the BfT-GemVet project). Strain collection All bacterial strains were initially recorded, checked and stored in the Institute of Microbiology and Epizootics at the FU Berlin. A second copy of this strain collection was stored in the Institute of Animal Breeding (FAL) in Neustadt-Mariensee. An agreement was made between the three BfT-GermVet consortium partner institutions (FAL Neustadt-Mariensee, FU Berlin, and LMU Munich) which institution should test which bacteria from which indications. Accordingly, the respective strains were verified for their species assignment in the respective partner institution prior to susceptibility testing. In-vitro susceptibility testing Only antimicrobial agents, which are approved for veterinary use, were included in the microtitre panels used for in-vitro susceptibility testing. Since it is impossible and also not necessary from the scientific point of view to test all antimicrobial agents licensed for use in animals, a decision had to be made which antimicrobial agents should be tested in which concentration steps. The members of the BfT-GermVet consortium agreed to test 22 single substances and another two combinations of antimicrobial agents in 10 or 12 two-fold serial concentration steps. Table 2 lists the antimicrobial agents or combinations tested, the corresponding concentrations tested, and provides information about other antimicrobial agents for which the results obtained are also applicable. The selection of so-called representative substances was based on the recommendations given in the document M31-S1 of the Clinical and Laboratory Standards Institute (CLSI) (NCCLS, 2004) as well as on our TABLE 3: Additionally tested antimicrobial agents and combinations. Antimicrobial agent/combination Test range (µg/ml) Lincomycin Lincomycin/spectinomycin (1/2) 0.06/ /256 Spectinomycin Neomycin Penicillin G/neomycin (1/1) 0.015/ /32 Penicillin G Penicillin G/dihydrostreptomycin (1/1) 0.015/ /32 Dihydrostreptomycin * * The results for dihydrostreptomycin are also valid for streptomycin. knowledge about cross-resistance (Schwarz et al., 2006; Werckenthin et al., 2005). For practical reasons, all bacterial strains were tested in the BfT-GermVet program for their susceptibility against all 24 antimicrobial agents or combinations of agents. Thus, intrinsic insensitivities (e.g. insensitivity of Escherichia coli against penicillin G or erythromycin) and restrictions of approval (e.g. prohibition of chloramphenicol use in food-producing animals) have not been taken into account. In a separate side-project, strains of the species Escherichia coli, Pasteurella multocida, Mannheimia haemolytica, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus hyicus, Staphylococcus intermedius, Streptococcus suis, Arcanobacterium pyogenes as well as N-haemolytic streptococci were investigated for their susceptibility against the three combinations lincomycin/spectinomycin (1/2), penicillin G/neomycin (1/1), and penicillin G/dihydrostreptomycin (1/1). These combinations were tested side-by-side with corresponding single substances on the same microtitre plate.the test ranges used are listed in Table 3. For in-vitro susceptibility testing, the broth microdilution method (Schwarz et al., 2003) was used according to the recommendations given in the document M31-A2 (NCCLS, 2002) of the CLSI. For testing of Arcanobacterium pyogenes, the CLSI method had to be modified slightly. The corresponding modifications are given in detail in the respective publication (Werckenthin et al., 2007). Cation-adjusted Mueller-Hinton broth was used as test medium. For the testing of streptococci, 2 5 % (v/v) lysed horse blood (Oxoid, Wesel, Germany) was added. The inoculated microtitre plates were incubated aerobically for hours. The inoculum density was adjusted to 2 8 x 10 5 CFU/ml and checked regularly. Layouts which contained a maximum of eight different antimicrobial agents or combinations of agents were designed and the corresponding microtitre plates Sensititre were manufactured by Trek Diagnostik Systems (West Sussex, UK). The MIC results were read by visual inspection. For quality control purposes, the reference strains Staphylococcus aureus ATCC and Escherichia coli ATCC were tested together with the bacterial strains from the 31 indications. Breakpoints The clinical breakpoints given in the CLSI documents M31- S1 (NCCLS, 2004) and M100-S17 (CLSI, 2007) were used to assign the determined minimum inhibitory concentrations (MIC values) to the qualitative categories susceptible, intermediate (if available) or resistant. Although the CLSI document M31-S1 is the only internationally available document presenting veterinary-specific breakpoints, the majority of the breakpoints available in this

5 Berl. Münch. Tierärztl. Wochenschr. 120, Heft 9/10, (2007) 361 document in particular those for the older antimicrobial agents is adopted from human medicine. Moreover, it should be noted that even the veterinary-specific clinical breakpoints given in the CLSI document are only applicable to the combination(s) of bacteria/indication/animal species indicated in the CLSI document M31-S1.The use of these breakpoints for other combinations of bacteria/indication/animal species, which are not explicitly mentioned in this CLSI document, is not permitted. Therefore, in cases in which no approved breakpoints were available, categorization of the MIC values was not attempted. Instead, the distribution of MIC values was presented without giving percentages of resistant or susceptible strains. Regardless of the availability of approved clinical breakpoints, MIC 50 and MIC 90 values were calculated for all combinations of antimicrobial agents/bacteria/indication/animal species. The MIC 50 and MIC 90 values represent those MIC values at which at least 50 % or 90 % of the test population are inhibited by the respective antimicrobial agent or combination of agents (Schwarz et al., 2003). The following slight deviations from the CLSI document M31-S1 were accepted by the Subcommittee on Veterinary Antimicrobial Susceptibility Testing (VAST) of the CLSI and used for analysis of the MIC data in the BfT-GermVet program: (i) S. aureus-specific breakpoints for oxacillin as mentioned in the CLSI document M31-S1 are valid not only for S. aureus, but also for other coagulase-positive and coagulase-variable staphylococci. (ii) Since the CLSI document M31-S1 does not list tetracycline-specific breakpoints for streptococci, but only those for organisms other than streptococci and for Streptococcus pneumoniae, the categorization of the tetracycline MICs for streptococci is based on the breakpoints given in CLSI document M100-S17 (CLSI, 2007). (iii) In the CLSI document M31-S1, breakpoints for the trimethoprim/sulfonamide (1/19) combination are available only for organisms other than streptococci (s: 2/38 µg/ml; r: 4/76 µg/ml). However, it is also stated in the same document that a susceptibility breakpoint of 2/38 µg/ml is only applicable to bacterial strains from urinary tract infections whereas strains from systemic infections should be considered as susceptible when they exhibit MICs of 0.5/9.5 µg/ml. As recommended by CLSI, the following breakpoints were used for strains of organisms other than streptococci from systemic infections: s: 0.5/9.5 µg/ml; r: 1/19 µg/ml. (iv) For the indications (Tab. 1), the results obtained for strains from dogs and cats were pooled. Although there are enrofloxacin-specific clinical breakpoints in the CLSI document M31-S1 which are valid for canine bacteria (Enterobacteriaceae, Staphylococcus spp., other not further specified bacteria) from respiratory and urinary tract infections, the corresponding breakpoints are missing for bacterial pathogens of cats. Based on the considerable proportion of bacteria from cats, the MIC values of enrofloxacin determined for bacteria from these indications were not categorized unless the strains in question were from dogs. As an exception, feline strains exhibiting very high enrofloxacin MICs of 32 µg/ml were considered as resistant. (v) The veterinary-specific breakpoints for ceftiofur as listed in the CLSI document M31-S1 for Streptococcus equi subsp. zooepidemicus are also applicable to other subspecies of S. equi. (vi) The veterinary-specific breakpoint for gentamicin is only given for Enterobacteriaceae and Pseudomonas aeruginosa from dogs and horses (s: 2 µg/ml, i: 4 µg/ml, r: 8 µg/ml). For other not further specified bacteria and animal species, a breakpoint adopted from human medicine is given (s: 4 µg/ml, i: 8 µg/ml, r: 16 µg/ml). As no Enterobacteriaceae strains from cats exhibited MIC values of 4 or 8 µg/ml, the veterinary-specific breakpoints were also applied to strains from cats. Implementation of the BfT-GermVet project As shown in Table 1, a total of 1,626 bacterial strains of the 31 indications were investigated for their in-vitro susceptibility during the 27-month period. This total number of bacterial strains included 85 strains from cattle, 322 strains from swine, 326 strains from horses, and 893 strains from dogs/cats. For a number of indications, it proved difficult if not impossible to obtain the requested number of strains (Tab. 1).The reasons for this may have been the overall low isolation rates at the diagnostic laboratories and/or the quality control criteria applied. Moreover, practitioners did not request laboratory confirmation in cases of unambiguous clinical diagnostics (e.g. Erysipelothrix rhusiopathiae infections in pigs) and diagnostic laboratories did not attempt to isolate the respective pathogens when non-cultural detection systems (e.g. PCR-based diagnostics) were preferentially used. Thus, only very small numbers of current field strains could be acquired for some indications despite extensive attempts. In other indications in which the requested numbers of bacterial strains have not been available, all strains collected were tested independently of their pre-treatment status. The percentage of strains from animals that had received an antimicrobial pre-treatment and were included in the BfT-GermVet program was low at 0.9 % among equine strains, 1.2 % among bovine strains, and 1.6 % among porcine strains, but relatively high at 13.0 % among the canine/feline strains (Tab. 1). In indications in which more than 100 strains from non-treated animals were available, strains for inclusion in the BfT-GermVet program were chosen on the basis of their geographical origin to ensure a distribution as broad as possible. Numerous strains were not included in the BfT-Germ- Vet program since they did not at all fulfil the quality control criteria. In this regard, mainly bacteria from swine were excluded since they were isolated within short time periods from the same farm and, thus, were likely to represent copy strains. In a smaller number of cases, species identification could not be confirmed and such strains were also excluded. The results obtained in the BfT-GermVet program are presented in detail in separate publications of this journal issue. Based on the breakpoints applicable for the different groups of bacteria and for a better comparison of the data, these data are summarized separately for Escherichia coli (Grobbel et al., 2007a), Klebsiella spp. and Proteus spp. (Grobbel et al., 2007b), Arcanobacterium pyogenes and Pseudomonas aeruginosa (Werckenthin et al., 2007), Staphylococcus spp. (Schwarz et al., 2007c), Streptococcus spp. (Schwarz et al., 2007a), as well as Pasteurella

6 362 Berl. Münch. Tierärztl. Wochenschr. 120, Heft 9/10, (2007) multocida and Bordetella bronchiseptica (Schwarz et al., 2007b). Data obtained from testing of the two Erysipelothrix rhusiopathiae strains from swine, the nine Actinobacillus equuli strains from horses, and the seven E. coli strains from cattle were considered as not representative due to low strain numbers and consequently, were not presented. People interested in these data may request them from any of the BfT-GermVet consortium partners. The results obtained from the testing of the three combinations lincomycin/spectinomycin (1/2), penicillin G/neomycin (1/1), and penicillin G/dihydrostreptomycin (1/1) in comparison to the respective single substances are presented in a separate manuscript (Schwarz et al., 2007d). Conclusion The BfT-GermVet program represents a highly successful joint approach conducted by four research institutions in Germany. For most of the bacteria/indication/animal species combinations tested the susceptibility data obtained are the first reliable data world-wide that have been determined on a national level. Continuing this program after a suitable time span of months is requested to detect temporal changes in the susceptibility status of the respective pathogens. Acknowledgements We thank the Bundesverband für Tiergesundheit (BfT) for initiation and continuous support during the course of this study. Special acknowledgements are given to the various colleagues working in the diagnostic laboratories from which bacterial strains for the BfT-GermVet program were provided. References Clinical and Laboratory Standards Institute (CLSI) (2007): Performance standards for antimicrobial susceptibility testing; seventeenth informational supplement. CLSI document M100-S17. Clinical and Laboratory Standards Institute, Wayne, PA, U.S.A. Grobbel, M., A. Lübke-Becker, E. Ales ík, S. Schwarz, C.Werckenthin, J. Wallmann, L. H. Wieler (2007a): Antimicrobial susceptibility of Escherichia coli from swine, horses, dogs and cats as determined in the BfT-GermVet monitoring program Berl. Münch. Tierärztl. Wochenschr. 120, Grobbel, M., A. Lübke-Becker, E. Ales ík, S. Schwarz, C.Werckenthin, J. Wallmann, L. H. Wieler, (2007b): Antimicrobial susceptibility of Klebsiella spp. and Proteus spp. from various indications of horses, dogs and cats as determined in the BfT-GermVet monitoring program Berl. Münch. Tierärztl. Wochenschr. 120, National Committee for Clinical Laboratory Standards (NCCLS) (2002): Performance standards for antimicrobial disk and dilution susceptibility tests for bacteria isolated from animals; approved standard. 2nd Edition. NCCLS document M31-A2. National Committee for Clinical Laboratory Standards, Wayne, PA, U.S.A. National Committee for Clinical Laboratory Standards (NCCLS) (2004): Performance standards for antimicrobial disk and dilution susceptibility tests for bacteria isolated from animals; approved standard; Informational supplement (May 2004). NCCLS document M31-S1. National Committee for Clinical Laboratory Standards, Wayne, PA, U.S.A. Schwarz, S., E. Ales ík, M. Grobbel, A. Lübke-Becker, C. Werckenthin, L. H. Wieler, J. Wallmann (2007a): Antimicrobial susceptibility of streptococci from various indications of swine, horses, dogs and cats as determined in the BfT-GermVet monitoring program Berl. Münch. Tierärztl. Wochenschr. 120, Schwarz, S., E. Ales ík, M. Grobbel, A. Lübke-Becker, C. Werckenthin, L. H. Wieler, J. Wallmann (2007b): Antimicrobial susceptibility of Pasteurella multocida and Bordetella bronchiseptica from dogs and cats as determined in the BfT-GermVet monitoring program Berl. Münch. Tierärztl. Wochenschr. 120, Schwarz, S., E. Ales ík, C.Werckenthin, M. Grobbel, A. Lübke-Becker, L. H. Wieler, J. Wallmann (2007c): Antimicrobial susceptibility of coagulase-positive and coagulase-variable staphylococci from various indications of swine, dogs and cats as determined in the BfT-GermVet monitoring program Berl. Münch. Tierärztl. Wochenschr. 120, Schwarz, S., C. Werckenthin, E. Ales ík, L. H. Wieler, J. Wallmann (2007d): Susceptibility of bacterial pathogens against lincomycin/spectinomycin (1/2), penicillin G/neomycin (1/1), and penicillin G/dihydrostreptomycin (1/1) as determined in the BfT- GermVet monitoring program Berl. Münch. Tierärztl. Wochenschr. 120, Schwarz, S., A. Böttner, H. M. Hafez, C. Kehrenberg, M. Kietzmann, D. Klarmann, G. Klein, P. Krabisch, T. Kühn, G. Luhofer, A. Richter, W. Traeder, K.-H. Waldmann, J. Wallmann, C. Werckenthin (2003): Antimicrobial susceptibility testing of bacteria isolated from animals: methods for in-vitro susceptibility testing and their suitability with regard to the generation of the most useful data for therapeutic applications [article in German with English abstract]. Berl. Münch. Tierärztl. Wochenschr. 116, Schwarz, S., A. Cloeckaert, M. C. Roberts (2006): Mechanisms and spread of bacterial resistance to antimicrobial agents. p In F. M. Aarestrup (ed.) Antimicrobial resistance in bacteria of animal origin, ASM Press, Washington, DC, U.S.A. Wallmann, J., H. Kaspar, R. Kroker (2004): The prevalence of antimicrobial susceptibility of veterinary pathogens isolated from cattle and pigs: national antibiotic resistance monitoring 2002/2003 of the BVL [article in German with English abstract]. Berl. Münch. Tierärztl. Wochenschr. 117, Wallmann, J., K. Schröter, L. H.Wieler, R. Kroker (2003): National antibiotic resistance monitoring in veterinary pathogens from sick food-producing animals: the German programme and results from the 2001 pilot study. Int. J. Antimicrob. Agents 22, Werckenthin,C.,A.Böttner,H.M.Hafez,M.Kaske,C.Kehrenberg,M. Kietzmann, D. Klarmann, G. Klein, P. Krabisch, T. Kühn, G. Luhofer, A.Richter, S.Schwarz, C.Sigge,W.Traeder, K.-H.Waldmann, J.Wallmann (2005): Cross-resistance between antimicrobial agents used in veterinary medicine: molecular background and practical consequences for susceptibility testing [article in German with English abstract]. Berl. Münch. Tierärztl. Wochenschr. 118, Werckenthin, C., E. Ales ík, M. Grobbel, A. Lübke-Becker, S. Schwarz, L. H. Wieler, J. Wallmann (2007): Antimicrobial susceptibility of Pseudomonas aeruginosa from dogs and cats as well as Arcanobacterium pyogenes from cattle and swine as determined in the BfT-GermVet monitoring program Berl. Münch. Tierärztl. Wochenschr. 120, Corresponding author: Prof. Dr. Stefan Schwarz Institut für Tierzucht Bundesforschungsanstalt für Landwirtschaft (FAL) Höltystr. 10, Neustadt-Mariensee Tel , Fax: stefan.schwarz@fal.de