EPIDEMIOLOGY NEWS. Clin Microbiol Infect 2000: 6: 59 63

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1 EPIDEMIOLOGY NEWS Standardization and quality assurance for antimicrobial resistance surveillance of Streptococcus pneumoniae and Staphylococcus aureus within the European Antimicrobial Resistance Surveillance System (EARSS) W. Goettsch 1, S. L. A. M. Bronzwaer 1, A. J. de Neeling 1, M. C. J. Wale 2, H. Aubry-Damon 3, B. Olsson-Liljequist 4, M. J. W. Sprenger 1 and J. E. Degener 5 1 National Institute of Public Health and the Environment, Bilthoven, The Netherlands, 2 PHLS Antimicrobial Susceptibility Surveillance Unit (AmSSU), CDSC Trent Nottingham, UK, 3 Institut Pasteur, Centre National de Reference des Antibiotiques, Paris, France, 4 Swedish Institute for Infectious Disease Control, Stockholm, Sweden and 5 University Hospital Groningen, Groningen, The Netherlands Accepted 13 September 1999 Clin Microbiol Infect 2000: 6: INTRODUCTION From an epidemiological and methodological standpoint the comparison of antimicrobial resistance in different countries of the European Union (EU) is extremely difficult, since unbiased assessment is complicated. There are many reasons for these difficulties. Different antimicrobial agents are tested; different systems and different breakpoints for antimicrobial susceptibility testing are used; data from point-prevalence studies are used for longitudinal comparisons (e.g. studies on antibiotic resistance performed in 1970 and 1990), in spite of major differences in study conditions and methodology; frequently only resistant strains from selected materials are tested. Finally, differences between the prevalence of resistant strains from local practices and university hospitals are not taken into account. In order to obtain more comparable and reliable data, the European Commission has funded a European Antimicrobial Resistance Surveillance System (EARSS). This system, in which all member states of the European Union, plus Iceland and Norway participate, is co-ordinated by the National Institute of Public Health and the Environment of the Netherlands (RIVM). In Table 1 a number of European projects on antimicrobial resistance surveillance are listed. EARSS, which is financed by the EU, differs from other projects because it does not collect and test strains centrally but collects data from participating laboratories (Figure 1). It will be an ongoing surveillance system collecting and analyzing data at national and Corresponding author and reprint requests: S. L. A. M. Bronzwaer, Department of Infectious Diseases Epidemiology, National Institute of Public Health and the Environment, PO Box 1, 3720 BA Bilthoven, The Netherlands Tel: Fax: info.earss@rivm nl Web site: nl A list of participating countries, national co-ordinators and collaborators in EARSS is given in the Appendix. international level. EARSS intends to contribute to the quality of antimicrobial resistance surveillance in the local laboratories. More than 400 laboratories have agreed to participate in this European communicable disease network. In this paper the methodology used within EARSS is discussed, especially with regard to the epidemiological and microbiological difficulties already mentioned. STRUCTURE EARSS is an international network of national surveillance systems which aims to aggregate comparable and reliable antimicrobial resistance data for public health purposes in Europe. These national surveillance systems are based on output that can routinely be harvested from the diagnostic laboratory without changing the primary diagnostic process. All participating countries have appointed a national representative microbiologist and epidemiologist. They work together to use aggregated data sets for more complex epidemiological studies. One representative of each member state acts as national co-ordinator, whose main tasks are the co-ordination of participating laboratories, distribution and collection of the questionnaire on susceptibility testing and collecting and forwarding resistance data for international collation quarterly. Pilot-study On basis of criteria such as public health relevance, all present at the first EARSS meeting (18 20 May, 1998), agreed that Staphylococcus aureus and Streptococcus pneumoniae are the most relevant pathogens for the pilot phase in EARSS. In order to minimize sample bias, it was decided to test only Streptococcus pneumoniae isolates from blood and cerebrospinal fluid (CSF), and Staphylococcus aureus isolates from blood for antimicrobial resistance.

2 60 Clinical Microbiology and Infection, Volume 6 Number 2, February 2000 Table 1 Antimicrobial resistance surveillance projects in Europe Collection of Pathogens Funding strains data Remarks Alexander project Streptococcus pneumoniae, Pharmaceutical industry Yes No Collection of strains every year Haemophilus influenzae, Moraxella catarrhalis Artemis Study In relation to macrolide use Pharmaceutical industry Yes No World-wide EARSS Staphylococcus aureus a, EU (DG V) No Yes Determination of antimicrobial sus- Streptococcus pneumoniae a ceptibility in local laboratories Enter-net (Salmnet) Salmonella spp. EU (BIOMED) No Yes Determination of antimicrobial susceptibility in reference laboratories EuroTB Mycobacterium tuberculosis EU (DG V) No Yes Surveillance of resistance in start-up phase Harmony MRSA, VRE, EU (DG XII) No Yes Emphasis on molecular biology Clostridium difficile INSPEAR Staphylococcus aureus CDC/EMC No Yes Concerted action USA/EU Mystic In relation to meropenem use Pharmaceutical industry No Yes World-wide Resistance Web All relevant pathogens Pharmaceutical industry No Yes Electronic data collection and feedback SARISA Staphylococcus aureus Pharmaceutical industry Yes No Relation between resistance and usage is subject of research SENTRY (ENARE) Streptococcus pneumoniae, Pharmaceutical industry Yes No Emphasis on molecular biology H. influenzae, (ENARE was financed M. catarrhalis by the EU) TSN (MRL) All relevant pathogens Pharmaceutical industry No Yes Electronic data collection and feedback WARN Staphylococcus aureus, National government No Yes Starting with Czech Republic Streptococcus pneumoniae, Enterococcus spp. WHO/GASP Neisseria gonorrhoeae World Health Organization Emphasis on standardization and improvement of methodology WHO/IUATLD M. tuberculosis World Health Organization No Yes Status unknown a in the pilot-study. EU, European Union; CDC/EMC, Centre for Diseases Control/Emerging and other Communicable Diseases Surveillance and Control (WHO). Figure 1 Structure of the European Antimicrobial Resistance Surveillance System. PROTOCOLS FOR TESTING Staphylococcus aureus The objective is to study the methicillin-resistance of Staphylococcus aureus in blood isolates in hospitals in Europe using resistance data on the first isolate only of each strain from the blood of each patient ( patient-isolate ) with a hospital-acquired Staphylococcus aureus infection (confirmed by a coagulase test). The protocol is illustrated in Figure 2. Oxacillin screen plates (6 mg/l according to NCCLS) or oxacillin disks (1 mg or5mg) are used. When 1 mg oxacillin (NCCLS) is used, nonsusceptible isolates have a zone size of ¾10 mm. When 5 mg oxacillin (according to the French guide-

3 Epidemiology news 61 Figure 2 Protocol for testing susceptibility of Staphylococcus aureus. lines, SFM) is used, nonsusceptible isolates have a zone size of ¾19 mm. In the case of oxacillin-nonsusceptible Staphylococcus aureus, either the local participating laboratories or a reference laboratory additionally determine the minimum inhibitory concentrations (MICs) for oxacillin and vancomycin (range of dilutions: mg/l), specifying whether agar-dilution, microdilution or E-test are used, or the polymerase chain reaction (PCR) for the meca-gene. laboratories in each country, and the local situation regarding test procedures. A minimal set of reference strains is sent out from a central facility, and every participating laboratory must study them repeatedly, preferably every month under the same conditions as those used for their own strains. At this time point, the exact quality assurance scheme is discussed by the advisory board of EARSS. After consultation of the national co-ordinators, it will be implemented next year. More information is available on the web site. Streptococcus pneumoniae The objective is to study the penicillin resistance of Streptococcus pneumoniae blood and CSF isolates in Europe using resistance data on the first isolate only from the blood or CSF of each patient with a community acquired Streptococcus pneumoniae (indentification confirmed by optochin test) infection. The protocol is illustrated in Figure 3. For testing of Streptococcus pneumoniae oxacillin disks (1 mg, NCCLS or 5 mg, SFM) are used. Non-susceptible strains have a zone size of ¾20 mm for 1 mg and ³26 mm for 5 mg. In the case of oxacillin nonsusceptible Streptococcus pneumoniae, either the local participating laboratories or the reference laboratory additionally determine the MICs for penicillin, cefotaxime or ceftriaxone and ciprofloxacin (range of dilutions: mg/l (penicillin) or mg/l (cefotaxime/ceftriaxone and ciprofloxacin)), specifying whether agar-dilution, microdilution or E-test is used. QUALITY ASSURANCE A quality assurance scheme is essential so that a comparative evaluation can be performed within and between countries, taking into consideration the number of participating SELECTION OF PARTICIPATING LABORATORIES EARSS included sufficient laboratories to cover at least 20% of the total population or 20% of the total number of annual bed days for each country. With over 400 laboratories participating in EARSS, the coverage is well over 20% of the population in all participating countries. Most are first-line clinical laboratories in which both academic and nonacademic hospitals are represented and the patient spectrum ranges from nursing homes to tertiary referral hospitals. EPIDEMIOLOGICAL DATA EARSS collects the following information by means of isolate record forms and questionnaire. Isolate record form The following information is required: sex, month and year of birth, date of sample collection, name or code of hospital, hospital department, origin of patient, isolate sample number, laboratory code, and antibiotic susceptibility testing results. Other optional information is clinical diagnosis, and antibiotic susceptibility data for other antibiotics.

4 62 Clinical Microbiology and Infection, Volume 6 Number 2, February 2000 Figure 3 Protocol for testing susceptibility of Streptococcus pneumoniae. Questionnaire on susceptibility testing This questionnaire provides information on test methods used, and collects denominator data of the laboratory, and of the hospital(s) served by one laboratory. The hospital facilities (ICU, renal, transplant, cardiac surgery) are described. For community acquired pathogens the catchment population of the laboratory is denominator. For nosocomial pathogens the number of bed days is the denominator. Patient and isolate information can be related to laboratory and hospital information by means of the unique laboratory code on all isolate record forms and questionnaires. DISCUSSION EARSS is carefully designed in order to avoid the epidemiological and microbiological fallacies summarized in the introduction. Two pathogens only, Staphylococcus aureus and Streptococcus pneumoniae, are tested against a restricted set of specified antimicrobials. The choice of oxacillin, instead of methicillin, for determination of MRSA (ORSA) is determined by methicillin becoming unavailable. For Streptococcus pneumoniae, testing of oxacillin, as a first step, in combination with a penicillin MIC for nonsusceptibles is now generally accepted [1]. We believe that the introduction of a new generation of fluoroquinolones for the therapy of respiratory tract infections necessitates a follow-up of ciprofloxacin resistance in Streptococcus pneumoniae. The protocols for Streptococcus pneumoniae and Staphylococcus aureus are clearly defined. After simple first-line screening the MIC is determined. Such a protocol combines easy accessibility with careful quantitative examination of antimicrobial resistance. The disk diffusion test does not always lead to comparable results, because of differences in inoculum, medium, time of incubation and use of CO 2. Thus, it is important to know what are the test procedures in each individual participating laboratory, in order to check and account for these differences. For reliable detection of resistance to oxacillin in Staphylococcus aureus, oxacillin agar screen plates can be used [2,3], but results from the questionnaire show that they are only used in a few countries. For that reason, we accept data from the oxacillin disk diffusion test [3,4]. The standard for confirmation of a suspected MRSA is testing for the presence of the meca-gene. When a participating laboratory is not able to perform a PCR, determination of the oxacillin MIC is carried out for presumptive confirmation of the strain as an MRSA, and the strain may be sent to a reference laboratory for PCR. Vancomycin-intermediate MRSA (VISA) strains, which were first reported in Japan [5,6], are often heterogeneously resistant. The presence of these VISA can be missed when measuring an MIC under standard conditions, but there is no established protocol to test for them. In addition, the relevance of this intermediate resistance to vancomycin for vancomycin therapy of MRSA can be disputed. In case of vancomycin MIC testing in MRSA we prefer a standardized protocol which is also used for oxacillin MICs, realizing that some VISA strains might be missed. In case of using the E-test we recommend to follow the guidelines of the producer. If VISA strains are detected, further analysis (e.g. sequence analysis) will be performed. Breakpoints are defined in the two protocols, according to NCCLS or in some cases to SFM (French) or Swedish Reference Group for Antibiotics (SRGA) (Swedish) guidelines, but the validity of these breakpoints is checked by several procedures within the protocol. For all Streptococcus pneumoniae and Staphylococcus aureus isolates, participating laboratories

5 Epidemiology news 63 record (when possible) the inhibition zone (in case of the disk method). This will give more insight into the distribution of susceptible, low-level and high-level resistant Streptococcus pneumoniae or Staphylococcus aureus strains [7]. In addition, the distribution of zone diameters is used to study the quality of resistance data from different participating laboratories [8]. The second step, MIC testing, validates the categorization of the strains as susceptible or nonsusceptible, according to the SFM and the NCCLS guidelines, and corrects false positive (resistant) results. Monthly testing of quality control strains assesses correct use of breakpoints for the categorization of strains into susceptible and resistant. EARSS will collect data continuously with the purpose of performing longitudinal analysis on developments in antimicrobial resistance. It is necessary for the national co-ordinators to update their information regularly on the techniques used for antimicrobial susceptibility testing by the first-line laboratories, in order to detect any changes in techniques used for antimicrobial susceptibility testing. Resistance surveillance on the basis of the whole range of routine samples may overestimate the resistance problem [9,10]. The EARSS pilot-study is therefore restricted to invasive isolates, which are routinely tested for antimicrobial susceptibility. The participating laboratories, serving university hospitals, small regional hospitals and general practitioners, provide the national co-ordinators with information on the number of patient-days of every hospital they serve and the catchment population. The first result of EARSS is that the system has stimulated several countries to establish or to update their national resistance surveillance system in order to follow national resistance patterns and to compare these with developments in Europe. We believe that it can be a good framework in the European Union for monitoring antimicrobial resistance in the future. REFERENCES 1. Sinave C, Jette LP. Use of oxacillin disk screening test for detection of penicillin- and cefalosporin-resistant pneumococci. In: ICAAC, September, San Diego. 1998: Abstract D Frebourg NB, Nouet D, Lemee L, Martin E, Lemeland JF. Comparison of ATB Staph, Vitek, and E-test methods for detection of oxacillin heteroresistance in staphylococci possessing meca. J Clin Microbiol 1998; 36: Cormican MG, Wilke WW, Barrett MS, Pfaller MA, Jones RN. Phenotypic detection of meca-positive staphylococcal blood stream isolates: high accuracy of simple disk diffusion tests. Diagn Microbiol Infect Dis 1996; 25 (3): Ramotar K, Bobrowska M, Jessamine P, Toye B. Detection of methicillin resistance in coagulase-negative staphylococci initially reported as methicillin susceptible using automated methods. Diagn Microbiol Infect Dis 1998; 30 (4): Hiramitsu K, Hanaki H, Ino T, Yabuta K, Oguri T, Tenover FC. Methicillin-resistant Staphylococcus aureus clinical strain with reduced vancomycin susceptibility. J Antimicrob Chem 1997; 40: Hiramitsu K, Aritaka N, Hanaki H et al. Dissemination in Japanese hospitals of strains of Staphylococcus aureus heterogeneously resistant to vancomycin. Lancet 1997; 350: Ringertz S, Olsson Liljequist B, Kahlmeter G, Kronvall G. Antimicrobial susceptibility testing in Sweden II. Species-related zone diameter breakpoints to avoid interpretive errors and guard against unrecognized evolution of resistance. Scand J Infect Dis 1997; 105 (Suppl.) : Blanc DS, Petignat C, Moreillon P, Wenger A, Bille J, Francioli P. Quantitative antibiogram as a typing method for the prospective epidemiological surveillance and control of MRSA. Comparison with molecular typing. Infect Control Hosp Epidemiol 1996; 17: Neeling de AJ, Pelt van W, Hendrix MGR et al. Antibiotic resistance in the Netherlands. Part II. Gram-negative bacteria [NL]. Antibioticumresistentie in Nederland. Deel II. Gram-negatieve bacteriën. Infectieziekten Bull 1997; 8: Neeling AJ, Jong de J, Overbeek BP et al. Quantitative susceptibility research with intra- and extramural Escherichia coli isolates [NL]. Kwantitatief gevoeligheidsonderzoek met intra- en extramurale isolaten van Escherichia coli. RIVM report nr Biltnoven, RIVM, APPENDIX Participating countries, national co-ordinators and collaborators in EARSS Austria, H. Mittermayer/W. Koller; Belgium, H. Goossens/ F. van Loock; Denmark, T. Soerensen/D. Monnet; Finland, P. Huovinen/O. Lyytikäinen; France, P. Courvalin/H. Aubry- Damon; Germany, W. Witte/F. Tieman; Greece, N. Legakis/ A. Vatopoulos; Iceland, K. Kristinsson/H. Briem; Ireland, L. Fenelon/D. O Flanagan; Italy, G. Cornaglia/M.L. Moro; Luxembourg, R. Hemmer; Netherlands, H. de Neeling/ W. Goettsch; Norway, E. Hoiby/P. Aavitsland; Portugal, M. Caniça/M. Paixao; Spain, F. Baquero/J. Campos; Sweden, O. Cars/B. Olsson-Liljequist; United Kingdom, D. Livermore/ M. Wale; WHO, R.Williams/J. Stelling; ESCMID, I. Phillips/ M. Struelens.