ACCEPTED. Extended-spectrum ß-lactamases of the CTX-M type now in. Switzerland

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1 AAC Accepts, published online ahead of print on 0 April 00 Antimicrob. Agents Chemother. doi:./aac.0-0 Copyright 00, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved Revised AAC -0 Extended-spectrum ß-lactamases of the CTX-M type now in Switzerland Marie-Frédérique Lartigue, 1ψ Catherine Zinsius, 1 Aline Wenger, Jacques Bille, Laurent Poirel, 1 and Patrice Nordmann 1* Service de Bactériologie-Virologie, Hôpital de Bicêtre, Assistance Publique/ Hôpitaux de Paris, Faculté de Médecine Paris-Sud, Université Paris Sud, K.-Bicêtre, France, 1 and Institut de Microbiologie, Centre Hospitalier Universitaire Vaudois, CH Lausanne, Switzerland. Keywords: Extended spectrum ß-lactamases, CTX-M, Switzerland 1 1 Running title: CTX-Ms in Switzerland * Corresponding author. Mailing address: Service de Bactériologie-Virologie, Hôpital de Bicêtre, rue du Général Leclerc, K.-Bicêtre, France. Phone: Fax: nordmann.patrice@bct.aphp.fr 1

2 ψ Present address: Service de Bactériologie-Hygiène, CHRU Trousseau, UFR Médecine, Université François-Rabelais de Tours, 000 Tours Cedex, France.

3 1 Epidemiology of clavulanic-acid inhibited extended-spectrum ß-lactamases (ESBL) was investigated among infection-associated enterobacterial isolates at the University Hospital in Lausanne, Switzerland from January 00 to June 00. Out of non repetitive ESBL producers (prevalence rate of 0.%), produced CTX-M-like ESBLs. CTX-Ms were mostly from clonally non-related Escherichia coli isolates, from urinary infections and community-acquired patients. Pediatric patients (0 out of ) accounted for a large number of CTX-M producers. CTX- M-1 was the most frequent CTX-M-type enzyme. The plasmid-located bla CTX-M genes were associated to either ISEcp1 or ISCR1 insertion sequences. This study is the first published report of CTX-M-type ß-lactamases in Switzerland.

4 Plasmid-mediated extended-spectrum ß-lactamases (ESBLs) were first identified in a Klebsiella pneumoniae isolate in Germany in 1 (1). Then, ESBL-positive Enterobacteriaceae have been isolated worldwide mostly from hospitalized patients (1). These enzymes hydrolyze significantly expanded-spectrum cephalosporins such as cefotaxime, and ceftazidime, and the monobactam aztreonam, sparing carbapenems. Their activity is inhibited in vitro by clavulanic acid. Until the 000 s, most of the ESBLs were structurally related to the narrow-spectrum TEM- and SHV-type ß- lactamases, with single to several amino acid substitutions surrounding their active site (1). Beginning late s, novel types of ESBLs, the CTX-M enzymes, have emerged worldwide, mostly from Escherichia coli. The CTX-Ms are mostly from community- acquired isolates (, ). The over fifty CTX-M enzymes so far reported may be grouped into five main subgroups according to amino acid sequence identity (CTX-M- 1, -M-, -M-, -M-, and -M-) (). Most of the CTX-Ms hydrolyze cefotaxime better than ceftazidime. However, several CTX-Ms including CTX-M-1 (, 1, ), which is now the most widespread CTX-M enzyme worldwide (), hydrolyze ceftazidime better than cefotaxime (). Since those CTX-Ms are reported increasingly in France (, 1, 1, ), Italy (, 0), and recently Austria (), it was interesting to search for those enzymes in Switzerland, a country known to have a tight policy of antibiotic prescription and to have an overall low level of multidrug resistance in bacteria (). The aim of the present study was to estimate the prevalence and the type of the ESBLs produced by enterobacterial isolates among non-repetitive clinical isolates over an 1-month period from January 00 to June 00 at the University hospital of Lausanne, Switzerland.

5 MATERIALS AND METHODS Bacterial isolates. ESBL-producing enterobacterial isolates resulted from the screening of, enterobacterial isolates obtained from infections samples that were sent to the Department of Microbiology of the Lausanne University Hospital, Switzerland, from January 00 to June 00. Isolates were first identified by using the Vitek system (biomérieux SA, Marcy-l Etoile, France). Electrocompetent E. coli TOP (Invitrogen, Cergy Pontoise, France) was used as a recipient strain in transformation experiments. E. coli NCTC 01, harboring 1-, -, -, and -kb plasmids, was used as a plasmid-containing reference strain (). Susceptibility testing and screening for ESBL-producing isolates. The antibiotic susceptibility of enterobacterial clinical isolates was determined by Vitek Advance Expert System (biomerieux) and by the disk diffusion method on Mueller- Hinton (MH) agar plates with ß-lactam and non-ß-lactam antibiotic-containing disks (Sanofi Diagnostics Pasteur, Marnes-La-Coquette, France), according to the Clinical and Laboratory Standards Institute guidelines (). The double-disk synergy test was performed with ceftriaxone, ceftazidime, aztreonam, cefpodoxime and amoxicillin- clavulanic acid disks using different disk spacings (0,, 0, and 0 mm) on MH agar plates, and the results were interpreted as described previously (). The Etest strips containing cefepime cefepime + clavulanic acid (AB Biodisk, Solna, Sweden) was also performed. Then, MICs were determined for selected ß-lactams by an agar dilution technique on MH agar with an inoculum of CFU per spot, as described previously (). MICs of several ß-lactams were determined alone or in combination with a fixed concentration of either clavulanic acid ( g/ml) or tazobactam ( g/ml). MIC values were interpreted according to the guidelines of the Clinical and Laboratory Standards Institute ().

6 PCR amplification for detection of ESBL genes, analysis of genetic their environment, and sequencing. Under standard PCR conditions (0), a series of primers was used for detection of several Ambler class A ß-lactamase genes (Table 1). Detection was performed for genes encoding TEM (PRETEM-1 and PRETEM-), SHV (OS- and OS-), and CTX-M (CTXM-A1 and CTXM-A) (, ). For each reaction, 0. µg of whole-cell DNA of the ESBL-possessing enterobacterial isolates or 0. µg of plasmid DNA from E. coli TOP electroporants was used. The genetic environment of the bla CTX-M genes was characterized by PCR (1) since different genetic elements are associated with the bla CTX-M genes such as ISEcp1- like insertion sequences and the ISCR1 element comprising orf1 which is embedded in a sul1-type integron (). Whole-cell DNA of the isolates was extracted as described previously (1). The regions located upstream of the bla CTX-M genes were amplified with primers annealing to ISEcp1, to orf1 of ISCR1 together with primers for the bla CTX-M genes (). The sequences located downstream to the bla CTX-M genes were studied by PCR experiments with the forward primer CTX-MA1 and the reverse primer CTX-M-preB or IS0Bint. When the orf1 gene was found upstream of bla CTX-M, a PCR experiment was performed with primer CTX-MA1 and reverse primer qaced-1b in order to search for a sul1-type integron structure as previously described with a duplication (even partial) of the ISCR1 element (1, ). For direct DNA sequencing, PCR products were purified using PCR purification columns (Qiagen, Courtaboeuf, France). The sizes of the sequenced bla SHV, bla TEM, bla CTX-M genes were -, 1-, -bp, respectively. Sequencing reactions were performed using specific primers and an automated sequencer (ABI ; Applied Biosystems, Foster City, Calif.). The nucleotide and deduced protein sequences were analyzed with software available over the Internet at the National Center of

7 Biotechnology Information website ( Plasmid transfer and analysis. Plasmid DNAs of enterobacterial isolates were extracted using the Kieser technique (1). They were then electroporated into E. coli TOP, and recombinant strains were selected onto cefotaxime-containing (1 µg/ml) Trypticase Soy agar plates. Plasmid DNAs of these transformants were detected by electrophoresis on a 0.% agarose gel. Hybridization. DNA-DNA hybridizations were performed as described with a Southern transfer of an agarose gel containing plasmid DNA from E. coli TOP electroporants (). The probes consisted in a ca. 00-bp PCR fragment generated from isolate producing CTX-M-1, isolate producing CTX-M-1, and isolate producing CTX-M-. They were internal to the bla CTX-M genes (1). Labeling of the probe and signal detection were carried out using a nonradioactive labeling and detection kit according to the manufacturer instructions (Amersham Pharmacia Biotech). PFGE. Whole-cell DNAs embedded in 1% agarose plugs (Bio-Rad) were digested with XbaI restriction enzyme (Amersham Pharmacia Biotech) and separated in a 1% pulsed-field-certified agarose gel (Bio-Rad) by using a CHEF DRII system (Bio- Rad), as described previously (). Pulsed field gel electrophoresis (PFGE) was run at 1 C, with a V/cm current, a switch angle of, and for E. coli, a run time of 1 h followed by a run time of 1 h, with two linear switch ramps of and 1 s and 1 to s, and for K. pneumoniae, switch times of to s for 0 h. After migration, gels were stained in a 0. mg/ml ethidium bromide solution, and PFGE results were analyzed according to the criteria of Tenover et al. (). RESULTS

8 Epidemiology and PCR detection of ß-lactamase genes. A total of nonrepetitive ESBL-positive isolates were collected from patients. The prevalence of ESBL producers was 0.%. Any enterobacterial isolate flagged as a possible ESBL producer by Vitek Advance Expert System was tested by the double-disk test and by the Etest strip containing cefepime/cefepime + clavulanic acid. They were E. coli (n = 1), Klebsiella pneumoniae (n = 1), and Enterobacter cloacae (n = ) Proteus mirabilis (n =), and Klebsiella oxytoca (n=1). The sex ratio of patients were /, female/man. The isolates were from hospitalized patients (/), outpatients (/), and significantly from the pediatrics (1/). Out of the hospitalized patients, isolates were obtained within the h of their hospitalization. Therefore, community- acquired isolates were from 0 patients ( hospitalized patients + outpatients). Three patients had two different ESBL (+) isolates (E. coli and K. pneumoniae in two cases, and E. coli and P. mirabilis in one case) that were collected at different periods of time. Moreover, a same ESBL (+) isolate was identified from an urinary sample of a woman and from the eyes of her twins. The ESBL (+) isolates were mostly from urine (%), from pus (%) but also from respiratory tract or blood. Most of the patients were treated successfully with a carbapenem-containing antibiotic regimen (data not shown). PCR experiments with primers specific for the bla CTX-M, bla TEM, and bla SHV genes yielded bla CTX-M -positive results for out of the isolates (Table ). A bla CTX-M -gene was identified in 1 out of the 0 community-acquired isolates. The bla TEM and bla SHV genes encoding ESBLs were identified in all the 1 bla CTX-M -negative isolates. A single isolate (E. coli 1) expressed two different ESBLs. Molecular identification of bla CTX-M, bla TEM, and bla SHV genes and genetic environment of bla CTX-M genes. Seventy nine per cent of ESBLs were CTX-M

9 enzymes (/) (Table ). Most of them (%, /) belonged to the CTX-M-1 group: CTX-M-1 being predominant (/). Twenty per cent of the CTX-Ms were CTX-M--like (/) being either CTX-M-1 or CTX-M-. A single isolate produced CTX-M-. A single E. coli isolate produced both CTX-M-1 and CTX-M-1. Sixty per cent of the CTX-M-producers isolates produced also the narrow-spectrum ß-lactamase TEM-1. E. coli was the main ESBL-producer. It was identified in % of the CTX-M- positive isolates and CTX-M enzymes accounted for 1% of the ESBLs in that species. The prevalence of CTX-M among ESBL types was also high in K. pneumoniae (%). Only one out of the six E. cloacae isolates produced a CTX-M enzyme. The other ESBLs were mostly of the SHV-type in E. cloacae and K. pneumoniae (Table ). The genetic structure surrounding the bla CTX-M genes was then determined. ISEcp1 was identified upstream of out of the bla CTX-M (+) genes (1%). The right boundary of ISEcp1 was located between to 0 bp upstream of the start codon of bla CTX-M genes. ISEcp1 was identified at 0 bp upstream of bla CTX-M-1 gene and at bp upstream of bla CTX-M-1 genes. A -bp region with an identical sequence was found between ISEcp1 and the start codon of bla CTX-M- -like genes (bla CTX-M-, and bla CTX-M- 1). Downstream of four out of six bla CTX-M-1 genes (1, 1,, and 1), an IS0-like element was found as already described for this gene (). ISEcp1 was not identified upstream of the bla CTX-M- and bla CTX-M- genes, as previously reported (1). ISCR1 was found in isolates harboring bla CTX-M- and bla CTX-M- genes (Figure). Antibiotic susceptibility results. The isolates were resistant to amino-, ureido-, and carboxy-penicillins, and clavulanic acid and tazobactam addition partially restored the activity of those antibiotics (Table ). Isolates producing CTX-Ms were resistant to cefotaxime whereas this was not always the case for TEM- and SHV producers. The

10 CTX-M-1 producers were resistant also to ceftazidime except two isolates (E. coli, and P. mirabilis ). Susceptibilities to cefepime and cefpirome varied whereas they were constant for carbapenems. Disk diffusion susceptibility testing indicated that overall resistance rate of ESBL producers were,, 0,, 0% for amikacin, sulfonamides, ciprofloxacin, tetracyclines and chloramphenicol, respectively, with no significant difference between CTX-M and non-ctx-m producers (data not shown). PFGE. Analysis of XbaI-restricted DNA of CTX-M-producing E. coli and K. pneumoniae isolates showed that the bla CTX-M -positive isolates were mostly non- clonally related. Only three E. coli isolates (isolates, 1, and ) were clonally related or identical. Those isolates produced CTX-M-1 and two of them (isolates and 1) were identified from patients hospitalized in the same ward. Analysis of the PFGE profiles of CTX-M-1-producing K. pneumoniae isolates showed that three isolates (0, 1, and ) were undistinguishable. They were from urine of a mother of premature twins and from conjonctivitis of her twins. Plasmid analysis and hybridization. Analysis of plasmid DNAs of the CTX-M- producing isolates were extracted and analyzed by gel electrophoresis. Their sizes ranged from to kb with one to five plasmids per isolate. The plasmid DNAs hybridized with any of the three internal probes for bla CTX-M-1-like, bla CTX-M-, and bla CTX- M--like (data not shown). A single hybridization signal was evidenced in each isolate, except for E. coli isolate 1 exhibiting two hybridization signals. These results showed that all except one CTX-M producers contained a single bla CTX-M gene. Those ß- lactamase genes were located on 0- and -kb plasmids. Four out of the seven bla CTX- M-1 genes were located on a similar-in-size plasmid (ca. 0 kb) although the CTX-M producers were not clonally related. The bla CTX-M-1 genes were located mostly on plasmids varying in size. The bla CTX-M-1 and bla CTX-M-1 genes of E. coli isolate 1 were

11 located on two different plasmids of 0-kb and 1-kb, respectively. These results indicated that the spread of bla CTX-M genes resulted from both clonal and plasmid spread. DISCUSSION The results of this work provided insights into the molecular epidemiology of the spread of ESBLs in enterobacterial isolates responsible for infections at a University hospital in Switzerland. The prevalence rate of ESBL producers was 0.% which is a very similar value to that reported in the nearby-located country Austria in 00 (). However this rate is lower than that reported in the Netherlands (.% in Amsterdam, 00 [1]), in France (.% at Bicetre hospital, 00, P Nordmann, personal data), Italy (1.%, 00) (), and the United States (.%, ) (1). Variable prevalence rates of ESBL producers may be related in part to differences in antibiotic policy (more quinolone used than ß-lactams for treating community patients in Switzerland []) but also to differences in urbanization sizes (Paris area or Amsterdam versus Lausanne for example). The bla CTX-M genes were widespread among ESBL producers in (% of ESBL-producers) which was a slightly higher value than that reported at Bicêtre hospital (%) (personal data), in Amsterdam (%) (1), and in Austria (%) (). A recent study performed in several Swiss laboratories between 001 and 00 identified.% of CTX-Ms among ESBLs producers (). ESBLs of E. coli were mostly CTX-Ms at Lausanne (1%), at Bicêtre (%, personal data), in Austria (%, []), in Amsterdam (%, [1]). Moreover, / of the CTX-M producers were E. coli. The prevalence of CTX-Ms among ESBL(+) K. pneumoniae was also high (%) as in Paris (%), whereas this value was much more lower in Austria (0%) and in Italy (1.%) (0).

12 Most of ESBL-producing E. coli isolates (%) have been isolated from urinary tract infections, as found in other studies (,, ). More than one-third of CTX-Mproducing isolates were from community-acquired infections, as reported from other European countries (,, ). Most of the CTX-Ms identified in Switzerland belonged to the CTX-M group 1 (CTX-M-1, ) as reported in France (Bicêtre hospital, [personal data], and Center and South of France [1]), in Austria (), and in Amsterdam (1). CTX-M-1 was the predominant CTX-M in Lausanne (%), as elsewhere in Western Europe (, 1, 0, ). Twenty per cent of the CTX-M enzymes were CTX-M--like in Lausanne, % in Austria, and only % in Bicêtre hospital. Moreover, CTX-M- and the genetically- related CTX-M-1 were the more prevalent CTX-M-types isolated from clinical samples in Spain until 00 (). PFGE analysis showed that the spread of bla CTX-M (+) E. coli and K. pneumoniae isolates was not related to spread of single clones whereas reported in several studies from other countries (UK, France, Italy, Spain) (, 0, 1, ). Concerning non ß-lactam antimicrobial susceptibility of CTX-M producers, high rates of resistance were observed especially for ciprofloxacin (0%), as described in other countries such as in Austria (% ), in Canada (% ), and in Italy (% 0). However, the resistance rate to ciprofloxacin of isolates from pediatric patients was lower (%) than that from isolates from adults (%) which is consistent with a low usage of fluoroquinolones in pediatrics. We identified here the spread of community-acquired CTX-M producers in Switzerland with CTX-M-1 being the most prevalent type as observed now in other European countries. One of the most interesting finding of this study would be the size of the reservoir of CTX-M producers in pediatrics. Finally, spread of CTX-M producers 1

13 in community-acquired E. coli in Switzerland in a similar manner as observed its neighbouring countries may indicate difficulty for controlling those emerging resistance determinants whatever the antibiotic policy is. 1

14 ACKNOWLEDGEMENTS This work was funded by a grant from the Ministère de l'education Nationale et de la Recherche (UPRES-EA), Université Paris XI, France, and by the European Community (th PCRD, LSHM-CT-00-0). L.P. is a researcher from the INSERM, France. We thank Dr Cristina BELLINI for help for the reviewing of the medical charts. 1

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20 TABLE 1. Sequences of primers used for detection of bla CTX-M genes and their genetic environment. Primer name Primer sequence Location CTX-MA1 '-scsatgtgcagyaccagtaa-' bla CTX-M gene CTX-MA '-ccg cra tat grt tgg tgg tg-' bla CTX-M gene, reverse primer CTXMA '-gcc gct caa tgt taa cgg-' bla CTX-M gene (CTX-M- group) bla CTX-M gene (CTX-M- group), CTXMB '-gaa acc gtg ggt tac gat-' reverse primer CTXMA '-ctg atg taa cac gga ttg ac-' bla CTX-M gene (CTX-M- group) bla CTX-M gene (CTX-M- group), CTXMC rev '-agc gcc cca tta ttg aga g-' reverse primer TOHOb rev '-tta cag ccc ttc ggc gat-' bla CTX-M gene (CTX-M- group), reverse primer CTXMpréB '-cac ttt gcc gtc gtc taa ggc g-' bla CTX-M gene (CTX-M-1 group), reverse primer ISEcpPROM+ '-tgc tct gtg gat aac ttg c -' ISEcpPROM- '-gca gtc taa att ctt cgt g-' ISEcp1 upstream of the promoter ISEcp1 downstream of the promoter IS0Bint '-gct ttt tga ctt tcc act cgc-' IS0B transposase, reverse primer Orf1-D '-ctc acg ccc tgg caa ggt tt-' Orf1 Orf1-D '-ctt ttg ccc tag ctg cgg t-' Orf1, reverse primer Orf1-'ext '-cag ctg gta gag cag cgt c-' -end of Orf 1, reverse primer OS '-tta tct ccc tgt tag cca cc-' bla SHV gene OS '-gat ttg ctg att tcg ccg g-' bla SHV gene, reverse primer PRETEM-1 '-gta tcc gct cat gag aca ata-' bla TEM gene '-tct aaa gta tat atg agt aaa ctt ggt PRETEM- ctg-' bla TEM gene, reverse primer 0

21 TABLE. Characterization of aquired ß-lactamases in ESBL (+) isolates ß-Lactamases a Isolate CTX-M type TEM type SHV type E. cloacae 1 CTX-M- E. cloacae TEM-1 SHV- E. cloacae SHV- E. cloacae SHV E. cloacae TEM-1 SHV- E. cloacae TEM-1 SHV- E. coli CTX-M-1 TEM-1 E. coli CTX-M-1 TEM-1 E. coli CTX-M-1 E. coli CTX-M-1 TEM-1 E. coli CTX-M-1 E. coli 1 CTX-M-1 E. coli 1 CTX-M-1 E. coli 1 CTX-M-1, CTX-M-1 TEM-1 E. coli 1 CTX-M-1 E. coli 1 CTX-M-1 TEM-1 E. coli 1 CTX-M-1 TEM-1 E. coli 1 CTX-M-1 TEM-1 E. coli 1 TEM- E. coli 0 CTX-M-1 TEM-1 E. coli 1 CTX-M-1 TEM-1 1

22 E. coli CTX-M-1 E. coli CTX-M-1 TEM-1 E. coli TEM-1 SHV- E. coli CTX-M- E. coli CTX-M-1 E. coli CTX-M-1 TEM-1 E. coli CTX-M-1 TEM-1 E. coli CTX-M-1 TEM-1 E. coli 0 CTX-M-1 E. coli 1 TEM- E. coli CTX-M-1 E. coli CTX-M-1 E. coli CTX-M-1 E. coli CTX-M-1 TEM-1 E. coli CTX-M-1 E. coli CTX-M-1 K. oxytoca CTX-M-1 TEM-1 K. pneumoniae CTX-M-1 TEM-1 K. pneumoniae 0 CTX-M- K. pneumoniae 1 TEM-1 SHV- K. pneumoniae TEM-1/TEM- SHV- K. pneumoniae SHV- K. pneumoniae CTX-M-1 TEM-1 K. pneumoniae SHV-a K. pneumoniae CTX-M-1

23 K. pneumoniae CTX-M-1 TEM-1 K. pneumoniae CTX-M-1 1 K. pneumoniae CTX-M-1 K. pneumoniae 0 CTX-M-1 TEM-1 K. pneumoniae 1 CTX-M-1 TEM-1 K. pneumoniae CTX-M-1 TEM-1 K. pneumoniae CTX-M-1 K. pneumoniae CTX-M-1 TEM-1 K. pneumoniae CTX-M-1 TEM-1 P. mirabilis CTX-M-1 TEM-1 P. mirabilis CTX-M-1 TEM-1 a The ESBL names are boldened.

24 TABLE. MICs of ß-lactams for ESBL (+) isolates. ß-Lactam(s) MIC (µg/ml : range) for isolates producing : CTX-M-1 CTX-M-1 CTX-M- CTX-M- CTX-M-1 TEM-ES SHV-ES Amoxicillin > > > > > > > Amoxicillin and clavulanic acid a 1 - -> Ticarcillin > > > > > > > Ticarcillin and clavulanic acid Piperacillin > > - > Piperacillin and tazobactam b Cephalotin > > > > > > Cefoxitin Ceftazidime - 1 -> Cefotaxime >

25 Cefepime Aztreonam Imipenem Ertapenem a Clavulanic acid was at a fixed concentration of µg/ml. b Tazobactam was at a fixed concentration of µg/ml.

26 FIG. Surrounding DNA sequences of the bla CTX-M genes for the forty two isolates. Row 1, E. coli 1, and 1; row, E. coli,,, 1, 1, 1, 1, 0,,,,,,,,,,,, K. oxytoca, K. pneumoniae,,,,,, 0, 1,,,,, P. mirabilis, and ; row, E. coli,, 1, 1, 1, 0, and P. mirabilis.

27 ISEcp1 tnpa ISEcp1 tnpa ISEcp1 tnpa IRR IRR 0-bp -bp IRR -bp bla CTX-M-1 bla CTX-M-1 bla CTX-M-1 IS0 IRL tnpa