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RIVM rapport:In dit rapport worden de resultaten samengevat van de resistentie surveillance bij Neisseria gonorrhoeae in 1992 en 1993. Uit de enquete bij de medische microbiologische laboratoria blijkt dat de landelijke frequentie van penicillinase vormende gonokokken (PVG) na een aanvankelijke daling weer is gestegen tot ruim 20% van alle gonokokken isolaten in 1993. Het onderzoek in het RIVM van een collectie aselect verzamelde N.gonorrhoeae isolaten uit 5 centra toont aan dat in de periode 1991-1993 resistentie tegen tetracycline zich bij non-PVG handhaaft op 6 a 7% en bij PVG op ruim 10%. Resistentie-ontwikkeling tegen cefalosporines is nog niet waargenomen, maar isolaten met verminderde gevoeligheid voor fluorchinolonen worden reeds met een frequentie van ca. 1% gevonden. Uit het auxo- en serotyperingsonderzoek blijkt dat zowel bij PVG als non-PVG een grote diversiteit van A/S klassen voorkomt, waarbij prototrofe stammen en IB-serovars overheersen. Het merendeel van de isolaten zijn overigens geclusterd in een beperkt aantal A/S klassen. In hoeverre de isolaten binnen eenzelfde A/S klasse identiek zijn zal m.b.v. DNA-typering worden onderzocht., Within the framework of a continuing surveillance of resistance in Neisseria gonorrhoeae in the Netherlands, the results are presented for the period 1992-1993. An inquiry among the laboratories for medical microbiology showed that, after a temporary decrease, the frequency of penicillinase producing strains (PPGN) among the isolated gonococci increased again to a level of more than 20% in 1993. Susceptibility testing in our laboratory of a random collection of N.gonorrhoeae isolates from 5 centres indicated that in the period 1991-1993 the frequency of resistance against tetracycline among non-PPNG is maintained at 6 a 7% and among PPNG at more than 10%. Development of resistance against cephalosporins has not been observed yet, but isolates showing a decreased susceptibility to fluoroquinolones were found in nearly 1% of the strains. Auxo- and serotyping revealed a great variety of A/S classes among PPNG and non-PPNG with a predominance of auxotrofic strains belonging to IB-serovars. However the majority of the isolates are clustered in a limited number of A/S classes. The identity (clonality) of isolates within clusters will be studied using DNA-typing methods.

RIVM rapport:De gevoeligheid voor antibiotica werd bepaald bij 192 coagulase-positieve en 259 coagulase-negatieve stafylokokken. De bacterien werden geisoleerd in drie regionale laboratoria en onderzocht met de microtiter-methode. De groei werd gemeten met een microtiterscanner en de resultaten werden verwerkt met een computerprogramma. De resistentie van Staphylococcus aureus tegen de onderzochte antibiotica was lager dan 5%, behalve dat 73% van de isolaten beta-lactamase vormde en dus resistent was tegen amoxicilline. Coagulase-negatieve stafylokokken waren vaker resistent, bijv. tegen clindamycine (21%), erytromycine (33%), fusidinezuur (14%), gentamicine (36%), doxycycline (12%), cotrimoxazol (27%) en ciprofloxacine (13%). Het percentage beta-lactamase vormers was 69%., The susceptibility to antibiotics was determined for 192 coagulase-positive and 259 coagulase-negative staphylococci. The isolates were obtained in three regional laboratories in the Netherlands and tested using the microdilution method. After incubation the turbidity was measured in a photometer and the results were analyzed using a computer program. Less than 5% of the isolates of Staphylococcus aureus were resistant to any of the antibiotics, except amoxycillin (73% beta-lactamase producers). The percentages resistance for coagulase-negative staphylococci were generally higher: clindamycin (21%), erythromycin (33%), fusidic acid (14%), gentamicin (36%), doxycycline (12%), cotrimoxazole (27%) and ciprofloxacin (13%). The percentage beta-lactamase producers was 69%.

RIVM rapport:As part of the continuing surveillance of resistance among gonococci in the Netherlands the PPNG prevalence was estimated by questionnaire as well as by the study of 535 random isolates from 5 centres in Amsterdam The Hague and Rotterdam. In 1991 18% of all isolates of N.gonorrhoeae were PPNG, as compared to 30% in 1990. The prevalence of tetracycline resistance (TRNG) among PPNG further decreased to 8% (was 12% in 1990 and 40% in 1989) and remained low among non-PPNG (3 a 4%). No signs of increasing resistance to cefalosporines and fluoroquinolones were found. Among PPNG and non-PPNG many auxotypes (serovar classes) were determined ; but only a limited number of mainly non-requiring IB serovars was predominant.

RIVM rapport:This report describes a study which was carried out to investigate an epidemic of gonococci with resistance to penicillin and tetracyclin (TRNG/PPNG). This study involved all PPNG-isolates which were sent in by five laboratories from Amsterdam, Rotterdam and The Hague in 1989-1990. The epidemic of TRNG/PPNG was found to be related mainly to three strains: NR/IB-6, PRO/IA-3, PRO/IA-6 with the plasmid pattern 3.2+25.2. The introduction of TRNG/PPNG presumably took place in The Hague in 1988. Independent risk factors of an infection due to TRNG/PPNG were for men: age above 40 years, and sexual contact with a prostitute (only for men in Rotterdam and The Hague). No relation with prostitution was found for men in Amsterdam. Independent risk factors were for women: age above 40 years and Turkish or Latin American nationality. Strains from The Hague were also independently correlated to TRNG/PPNG. Further spread of resistant strains seems to be related to prostitution, but only in Rotterdam and The Hague. The outbreak of TRNG/PPNG underlined the necessity for a continuous surveillance of resistance of gonococci including some background variables of patients.

RIVM rapport:The susceptibility to antibiotics of three respiratory pathogens, Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis, was determined. The isolates were obtainied in three regional laboratories in the Netherlands and tested using the microdilution method. After incubation the turbidity was measured in a fotometer and the results were analysed at the RIVM by a computer program. Not all isolates grew well in the broth medium chosen and the resistance of a small number of strains retested on agar, was not confirmed. So the broth medium still needs improvement and the method must be compared with the established agar-dilution technique. Nevertheless the results of the investigation confirmed those of earlier research. Most isolates were still sensitive to commonly used antibiotics. The known insensitivity of Haemophilus influenzae to erythromycin and the marginal susceptibility of Streptococcus pneumoniae to quinolones was confirmed. Resistance of Haemophilus influenzae to amoxycillin was found in 10% of the isolates, mostly due to beta-lactamase production. Reduced susceptibility of Streptococcus pneumoniae to penicillin was found in approximately 2% of the isolates.

RIVM rapport:Three Dutch laboratories for medical microbiology collected a total number of 1432 strains of Escherichia coli. Of these 995 were obtained from routine samples taken in clinic and policlinic, 290 had been sent spontaneously by general practitioners for microbiological examination and 147 had been isolated from the urine of out-patients who had not been treated with antibiotics for at least six months. The highest resistance percentages were found for the older orally administered antibiotics in the strains that had been sent spontaneously by general practitioners. Resistance percentages were lowest, but still considerable, in the isolates obtained from patients who had not been treated with antibiotics: amoxycillin 20%, doxycycline 23%, sulfamethoxazole 32%, trimethoprim 10% and cotrimoxazole 10%. The level of resistance in clinic and policlinic was in between the levels in the two categories obtained from general practitioners. The resistance percentages for the other investigated antibiotics (Augmentin, cefazolin, cefaclor, cefamandole, cefuroxime, ceftazidime, imipenem, gentamicin, pipemidic acid, norfloxacin and nitrofurantoin) were lower than 7%. An explanation for the high level of resistance in the strains sent spontaneously by general practitioners is that they generally request susceptibility testing only if previous antibiotic therapy has failed.

RIVM rapport:Teneinde ervaring op te doen met een kwantitatieve resistentiepeiling met geautomatiseerde data-verwerking werden in drie ziekenhuislaboratoria MRC bepalingen verricht met klinische isolaten op in het RIVM bereide antibioticareeksen in microtiterplaatjes. De uitslagen van in totaal 945 isolaten werden ter evaluatie op floppy disk naar het RIVM gezonden. Aangezien de verschillen tussen de resistentiepercentages in de drie ziekenhuizen gering waren werd samenvoeging van hun resultaten verantwoord geacht. De hoogste resistentiepercentages werden gevonden voor de oudere antibiotica, t.w. amoxicilline, tetracyclines en cotrimoxazol (b.v. voor E.coli resp. 33%, 27% en 19%). De prevalentie van resistentie tegen de overige onderzochte antibiotica, o.a. de aminoglycosiden en de nieuwe beta-lactam antibiotica, bij organismen die van nature gevoelig zijn voor deze middelen was laag. Geconstateerd werd dat bewaring van de microtiterreeksen bij -70 graden C noodzakelijk is gezien de relatieve instabiliteit van clavulaanzuur en imipenem bij -20 graden C. Het onderzoek heeft aangetoond dat deze wijze van gevoeligheidssurveillance goed mogelijk is. Met name kunnen hiermee naast resistentiepercentages verschuivingen in de normale MRC-verdelingen worden vastgesteld in de tijd. Een vervolgonderzoek wordt dan ook overwogen.