Survey of bloodstream infection isolates: SENTRY Antimicrobial Surveillance Program in Buenos Aires, Argentina ( )

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1 Jordá Vrgs L, et l Survey of bloodstrem infection isoltes... rtículo originl/rtigo originl Survey of bloodstrem infection isoltes: SENTRY Antimicrobil Surveillnce Progrm in Buenos Aires, Argentin ( ) Vigilnci de bcteriemis: Progrm SENTRY de Vigilnci Antimicrobin en Buenos Aires, Argentin ( ) Lilin Jordá Vrgs 1 José Mrí Csells 2 An Gles 3 Gbriell Tomé 2 Helio S. Sder 4 Alejndr Lnz 1 Ronld N. Jones 4 Jorgelin Smyevsky 1 1 Clinicl Microbiologist, Biochemist. Lbortorio de Bcteriologí, Micologí y Prsitologí, CE (Centro de Educción Médic e Investigciones Clínics Norberto Quirno), Buenos Aires, Argentin. 2 Clinicl Microbiologist. Centro de Estudios Antimicrobinos, Sn Isidro, Buenos Aires, Argentin. 3 Clinicl Microbiologist, MD. Deprtmento de Medicin, Universidde Federl de So Pulo, SP, Brsil. 4 Clinicl Microbiologist, MD. JMI Lbortories, USA. Conflicto de interés: ninguno Rev Pnm Infectol 2006;8(3):11-17 Recibido el 23/3/2006. Aceptdo pr publicción el 19/9/2006. Abstrct Regionl ntimicrobil surveillnce progrms might help to guide empiric ntimicrobil therpy. This study reports the ntimicrobil susceptibility ptterns of 2198 isoltes from bloodstrem infections in period of 1997 to Susceptibility testing ws performed by broth microdilution methods. The most frequent orgnism ws Stphylococcus ureus (23.4%) with n oxcillin-resistnce rte of 41.8%. Extended Spectrum Bet Lctmses phenotype ws presented in 10.0% of Escherichi coli nd 49.4% in Klebsiell pneumonie isoltes. Imipenem nd meropenem were ctive ginst 74.3% nd 84.0% of Acinetobcter spp. nd Pseudomons eruginos, respectively. Bcteril resistnce continues to be gret problem in Argentinen medicl centers. Key words: Bloodstrem infections - ntimicrobil surveillnce. Resumen Los progrms de vigilnci ntimicrobin regionles podrín ser útiles en l elborción de guís de terpi ntimicrobin empíric. Nuestro trbjo document l sensibilidd ntimicrobin de 2198 isldos de bcteriemis en el período Los estudios de sensibilidd se relizron por el método de microdilución. El microorgnismo más frecuente fue Stphylococcus ureus (23,4%) con 41,8% de resistenci oxcilin. Se obtuvo fenotipo de productor de bet lctms de espectro extendido en el 10,0% de Escherichi coli y 49,4% de Klebsiell pneumonie. Imipenem y meropenem fueron ctivos contr 74,3% y 84,0% de Acinetobcter spp. y Pseudomons eruginos respectivmente. L resistenci ntimicrobin sigue siendo un problem en los centros médicos de Argentin. Plbrs clve: Bcteriemis - vigilnci ntimicrobin. Introduction Bloodstrem infections (BSI) cuse significnt morbidity nd mortlity worldwide (1). On the other hnd, the selective pressure 11

2 Rev Pnm Infectol 2006;8(3):11-17 Tble 1. Occurrence of the mjor pthogens isolted from BSI in Argentin (SENTRY Progrm, 1997 to 2002) Rnk ordering orgnisms N. % S. ureus CoNS E. coli K. pneumonie P. eruginos S. pneumonie Enterococcus spp Enterobcter spp Acinetobcter spp Proteus spp Viridns group estreptococci S. mltophili b hemolytic estreptococci Others Totl CoNS; cogulse-negtive stphylococci. produced by the use of ntimicrobils increses the ntimicrobil resistnce of nosocomil pthogens (2,3). The emergence nd dissemintion of resistnce mong grm-positive cocci hs been mjor problem in the United Sttes (US) nd Europe (4,5). In ddition, ntimicrobil resistnce mong grm-negtive bcilli hs lso incresed nd could hve serious consequences in other prts of the world, such s some Ltin Americn countries (6,7). The successful implementtion of n ntimicrobil surveillnce progrm fulfill the lck of long term dt relted to the ntimicrobil resistnce profiles in blood strem infection isoltes in Argentin (8,9). In this regrd we will be ble not only to know bout ntimicrobil resistnce existing in the country but lso to prevent over time the potentil emergence, contributing to the development of the proper empiricl therpy in hospitlized ptients. In this study, we report the frequencies of occurrence nd ntimicrobil susceptibility profiles of bloodstrem infections (BSI) isoltes from two medicl centers from Ciudd utónom de Buenos Aires Province, s well s from Rosrio, Snt Fé during These medicl centers were ttending severl medicl institutions nd prticipting in SENTRY Antimicrobil Surveillnce Progrm during the period. Mterils nd methods Lbortories prticipting in this study re two Argentinen sentinel hospitls included in the SENTRY Progrm. Bloodstrem infection isoltes (n = 2198) were collected from 1997 to All the isoltes were collected from hospitlized ptients from severl centers of Buenos Aires nd Snt Fe provinces in Argentin. Infections were mostly hospitl cquired excluding 30% of bcteremis due to Streptococcus pneumonie or Hemophilus influenze. Age rnge ws wide: >1-98y (medin 59y). Blood ws cultured either by uthomtized methods (bct/alert) or commercil bottles in erobic nd CO 2 tmosphere. Two bottles t lest were obtined for ech blood culture. These isoltes were identified by the routine methodology used t ech lbortory, nd were sent to the coordintor center in the USA. In the coordintor center, isoltes were subcultured onto blood gr to ensure vibility nd purity. Confirmtion of species identifiction ws performed with Vitek (biomerieux) or conventionl methods, s required. Antimicrobil susceptibility testing ws performed using the reference broth microdilution, s described by the Clinicl nd Lbortory Stndrd Institute (CLSI, formerly Ntionl Committee for Clinicl Lbortory Stndrds [NCCLS]) (10,11), using microdilution TREK pnels. Qulity controls were performed testing Escherichi coli ATCC 25922, Stphylococcus ureus ATCC 29213, Pseudomons eruginos ATCC 27853, Enterococcus feclis ATCC 29212, Hemophilus influenze ATCC 49247, nd Streptococcus pneumonie ATCC Escherichi coli nd Klebsiell spp. isoltes with incresed vlues (> 2 μg/ml) for ceftzidime nd/ or ceftrixone nd/or ztreonm were considered s screening criterion for detecting extended-spectrum b-lctmse (ESBL) producing phenotypes ccording to CLSI (11,12). ESBL phenotype ws confirmed using the ESBL E-test strips (AB BIODISK, Solm, Sweden (12) ) or disk pproximtion test (13), using cefotxime, ceftzidime or cefepime round moxicillin clvulnte disks ccording to CLSI M100-S15 recommendtions (11,13). Sttisticl nlysis ws performed using the X 2 test or the Fisher s exct test. A p<0.05 ws considered sttisticlly significnt (14). Results A totl of 2198 strins were obtined from BSI in the Argentinen medicl centers prticipting in the SENTRY Progrm over this six-yer period. Species distribution of the 13 mjor pthogens is summrized in tble 1. Grm-positive cocci represented 48% of the isoltes cusing BSI in this study. The most prevlent grm-positive orgnisms cusing BSI were S. ureus (23.4%), cogulse-negtive 12

3 Jordá Vrgs L, et l Survey of bloodstrem infection isoltes... Tble 2. Antimicrobil ctivity nd spectrum of drugs tested ginst grm-positive pthogens cusing bloodstrem infections in Argentin (SENTRY Progrm, 1997 to 2002). Antimicrobil clss/gent b-lctms S. ureus (n = 514) CoNS (n = 294) Enterococcus spp. (7 E. fecium; 88 E. feclis: 1 Enterococcus sp.) % Susc. 50/90 % Susc. 50/90 % Susc. Oxcillin 1/> /> c - c Ampicillin /> Ceftrixone 4/> b 16/> b - c - c Cefepime 4/> b 4/> b - c - c Mcrolide/Lincosmines Clindmycin 0.25/> /> c - c Erythromycin 0.50/> >8/> c - c Fluoroquinolones Ciprofloxcin 0.5/> /> /> Gtifloxcin 0.12/ / ,5/> Levofloxcin 0.25/ /> /> Aminoglycosides Gentmicin 2/> /> c - c Gentmicin (HL) d - c - c - c - c - d 76.8 Streptomycin (HL) d - c - c - c - c - d 75.8 Others Rifmpicin 0.25/> /> c - c Chlornphenicol 8/> /> c - c Trimethoprim/sulfmetoxzole <0.4/ <0.50/ c - c Tetrcycline 4/> /> >8/> Doxycycline 0.50/> / >4/> Vncomycin 1/ / / Teicoplnin 1/ / / Quinupristin/dlfopristin 0.25/ / />8 7.4 Linezolid 2/ / / CoNS: cogulse-negtive stphylococci; b susceptibility is predicted by the oxcillin result but lthough ctive this drugs re not indicted for treting infections cused by ORSA; c no brekpoint ; d HL: high level minoglycoside resistnce screening. stphylococci (CoNS) (13.4%), S. pneumonie (4.3%) nd Enterococcus spp. (4.3%). The ntimicrobil susceptibilities of these pthogens re shown in tbles 2 nd 3. Among S. ureus isoltes, 41.8% were resistnt to oxcillin (39.7%, 43.7%, 46.2%, 18.3%, 47.1%, nd 46.7% for 1997, 1998, 1999, 2000, 2001 nd 2002, respectively). Higher oxcillin resistnce rtes were observed mong CoNS (77.9%) overll. The most frequent non-b-lctm ntibiotic cross resistnces in oxcillin-resistnt S. ureus were gentmicin, erythromycin nd ciprofloxcin (figure 1). All stphylococcl isoltes were susceptible to vncomycin nd linezolid. However, there were stphylococcl isoltes with reduced susceptibility to teicoplnin or quinupristin/dlfopristin mong CoNS (tble 2). On the other hnd, vncomycin resistnce ws 5.3% mong enterococci, nd 23.2% of enterococcl strins showed high level resistnce to gentmicin. Among 95 isoltes of S. pneumonie from BSI, 80.0% were susceptible to penicillin ( < 0.06 μg/ ml), 9.5% showed intermedite resistnce (

4 Rev Pnm Infectol 2006;8(3):11-17 Figure 1. Resistnce rtes to non-b-lctm ntimicrobils mong oxcillin-resistnt Stphylococcus ureus from BSI in Argentin (SENTRY Progrm, ) SXT = Trimethoprim/sulfmetoxzole; CIP = Ciprofloxcin; GATI = Gtifloxcin; LEVO = Levofloxcin; GEN = Gentmicin; CLOR = Chlornphenicol; TETRA = Tetrcycline; ERITRO = Erythromycin; RIF = Rifmpicin Tble 3. Antimicrobil ctivity of selected prenterl nd orlly dministered drugs tested ginst Streptococcus pneumonie (n = 95) isolted from BSI in Argentin (SENTRY Progrm, 1997 to 2002) Antimicrobil gent % Susc. % I % R Penicillin Amoxicillin Ceftrixone Erythromycin < Clindmycin < Gtifloxcin Levofloxcin Trimethoprim/ sulfmetoxzole Quinupristin Dlfopristin Vncomycin Linezolid No brekpoint hs been estblished by the CLSI (10). 1 μg/ml), nd 10.5% were resistnt to penicillin ( > 2 μg/ml) (tble 3). Eighty percent of the ptients with BSI cused by S. pneumonie ws older thn 16 yers old. A higher penicillin resistnce rte ws observed in S. pneumonie in 1999 (tble 4). Erythromycin showed good in vitro ctivity ginst S. pneumonie ( 90, 2 μg/ml, 84.2% susceptibility), nd clindmycin resistnce ws low (6.3%). Only 67% of pneumococcl isoltes were susceptible to trimethoprim/sulfmethoxzole. Tble 5 summrizes the susceptibility ptterns of the five most frequently isolted grm-negtive bcilli. Cefepime ws the most ctive cephlosporin ginst E. coli (92.2%), nd imipenem showed 100.0% of susceptibility for Enterobctericee. The fluoroquinolones evluted showed similr in vitro ctivity ginst Enterobctericee, nd mikcin showed higher ctivity thn gentmicin ginst grmnegtive bcilli (tble 5). The frequency of isoltes with ESBL phenotype mong E. coli ws lower thn tht mong K. pneumonie (10.0 vs 49.4%) (p < 0.05) (tble 5). We found significnt increse in the frequency of ESBL-producing strins in 1998 nd 1999 (19.4 vs. 32.2%; p < 0.05) due to n increse of ESBL producing E. coli. The frequency of ESBL-phenotype in K. pneumonie nd E. coli ws 30.4, 29.4 nd 28.9% in 2000, 2001 nd 2002, respectively. Even not recommended by CLSI we tested ll isoltes of Slmonell spp for ESBL phenotypic production. We found 21.4% puttive ESBL producers in tht species. The Argentinin medicl centers prticipting in the SENTRY Progrm reported tht 8.8% of the isoltes from BSI corresponded to P. eruginos, with 29.9%, 16.0% nd 16.0% of ceftzidime, imipenem nd meropenem non-susceptible isoltes, respectively. Pipercillin/tzobctm ws ctive ginst 83.5% of the P. eruginos isoltes t the current susceptible brekpoint (tble 6). Acinetobcter spp. ws the fifth grm-negtive bcilli most frequently isolted. Imipenem nd mero- Tble 4. Evolution of penicillin resistnce in Streptococcus pneumonie (n = 95) isolted from BSI in Argentin (SENTRY Progrm, 1998 to 2002) Yer n % Susc. % I % R < < < < Totl

5 Jordá Vrgs L, et l Survey of bloodstrem infection isoltes... Tble 5. Antimicrobil ctivity nd spectrum of drugs tested ginst the most prevlent fermenting grm-negtive bcilli cusing BSI in Argentin (SENTRY Progrm ) Antimicrobil gents E. coli (n = 289) K. pneumonie (n = 259) Enterobcter spp. (n = 95) % S % S % S b Lctms Ampicillin >16/> Cefzolin 2/> >16/> Cefuroxime 4/> /> Cefoxitin 4/ / Ceftrixone 0,25/ <0,25/> /> Ceftzidime 0,25/ /> /> Cefepime 0,12/ /> /> Pipercilin/tzobctm 2/ /> /> Meropenem <0.06/<0, <0,06/0, <0.06/ Imipenem 0.12/ / />2 100 Fluoroquinolones Ciprofloxcin 0.25/> ,25/> /> Gtifloxcin <0.03/> ,06/> /> Levofloxcin 0.03/> /> /> Aminoglycosides Amikcin 2/ / /> Gentmicin 0,99/>8 87,7 2/> />8 60,6 ESBL phenotype 10.0% 49.4% ND b No brekpoint s hve been estblished by the CLSI (10) or the orgnism should be considered resistnt b ND; dt not vilble penem were ctive ginst 74.3% of the Acinetobcter spp. isoltes ( 90, > 8 μg/ml), while the remining ntimicrobil gents tested were ctive ginst less thn 60% of them (tble 6). Ampicillin/sulbctm ws not tested ginst Acinetobcter spp. nd polymixin B ws ctive ginst 100.0% of Acinetobcter spp. nd P. eruginos. Discussion Antimicrobil resistnce surveillnce progrms provide importnt informtion, both for the development of empiric ntimicrobil therpy recommendtions nd for the design of progrms to control ntimicrobil resistnce. Additionlly, the updting informtion bout ntimicrobil resistnce profiles my help infectious diseses nd other physicins to decide the wy to prevent or tret cliniclly importnt emerging resistnces. The SENTRY Progrm strted in Jnury 1997 nd ws designed to monitor ntimicrobil resistnce trends of both nosocomil nd community cquired pthogens over brod geogrphic re, using vlidted reference identifiction nd susceptibility testing methods t coordintor center. In Argentin, most surveillnce progrms does not focus on blood strem infections pthogens (8,9,15,16) or do not perform vlidted identifiction nd susceptibility testing t centrl lbortory for BSI isoltes. Given the high morbi-mortlity ssocited with BSI, it might be very useful to know the resistnce profiles involved in BSI-relted pthogens in Argentin. We therefore proposed to survey the ntimicrobil susceptibility of BSI pthogens reported by the Argentinin medicl centers prticipting in the SENTRY progrm in the period. In Argentin, S. ureus nd CoNS ccounted for 36% of ll BSI isoltes (SENTRY Progrm) during the periods. In this study, the prevlence of oxcillin resistnt S. ureus (ORSA) ws 41.8%, while ORSA rtes in the US nd Cnd were 30% nd 11.1% respectively (4,17). A Europen study of ntimicrobil resistnce reported n ORSA rte of 72% mong BSI isoltes (5). ORSA from BSI isoltes from Ltin-Americ hs been reported to be more resistnt to non-b-lctm ntimicrobil gents thn the ORSA isoltes from the US nd Cnd (4,17). Among non-b-lctm ntimicrobil gents herein tested, gentmicin, erythromycin, rifmpin nd fluoroquinolones showed limited ctivity ginst ORSA nd. However it must be considered tht ner 90% of the ORSA isoltes re presently susceptible to rifmpin (8,9). According to other ntionl reports, Argentin is one of the countries with reltively low penicillin-resistnce rtes mong S. pneumoni (8,9,15). 15

6 Rev Pnm Infectol 2006;8(3):11-17 Tble 6. Antimicrobil ctivity nd spectrum of drugs tested ginst P. eruginos nd A. bumnnii cusing BSI in Argentin (SENTRY Progrm ) Antimicrobil gents b Lctms P. eruginos (n = 194) A. bumnnii (n = 70) % S % S Ceftzidime 4/> >16/> Cefepime 4/ /> Pipercilin/tzobctm 8/> /> Meropenem 1/> /> Imipenem 1/ /> Fluoroquinolones Ciprofloxcin 0,25/> >2/> Gtifloxcin 1/> /> Levofloxcin 1/> >4/> Aminoglycosides Amikcin 4/> >32/> Gentmicin 2/> >8/> In contrst to the dt reported by the North Americn centers prticipting in the SENTRY Progrm, in Argentin, there ws smll higher prevlence of grm-negtive bcilli compred to grm-positive cocci mong isoltes from BSI. Our study grees with Ltin Americn reports of BSI isoltions (6,7,17,18). Emphsis should be lid on infections cused by phenotipiclly ESBL-producing Enterobctericee tht re usully resistnt to multiple ntimicrobils nd hydrolyze thirdnd fourth-genertion cephlosporins. Over the lst yers, the globl rte of ESBL-producing strins of E. coli nd Klebsiell spp. hs remined low in the US (6,17,18). In this study, however, high rte of ESBL-producing Enterobctericee (49.4% nd 10% for Klebsiell spp. nd E. coli, respectively) hs been reported, ccording to other studies in Ltin Americ (7,17,18). On the other hnd, lthough ESBL-producing Slmonell spp. hs not been reported in 2001 nd 2002, continuous ntimicrobil resistnce surveillnce is required to detect the emergence of this importnt mechnism of resistnce mong Enterobctericee species not commonly reported s phenotipiclly ESBL-producing (20). Since pressure produced by the use of ntimicrobil hs n impct on the emergence nd dissemintion extended spectrum ß-lctmses, ctive nd continuous ntimicrobil resistnce surveillnce is needed. The crbpenems represent the ltest options in ntimicrobil therpy for grm-negtive bcilli nosocomil infections (2,3). In this sense, crbpenem resistnce is surveyed by surveillnce progrms, such s the MYSTIC study, which involved 33 hospitl centers in Europe, Mexico nd Isrel. The 90 reported for Acinetobcter spp. nd P. eruginos were 8 nd 4-8 ug/ml respectively (21,22). In our study, 16.0% nd 25.7% of P. eruginos nd Acinetobcter spp., respectively, were not susceptible to either imipenem or meropenem. Other ntimicrobil gents herein tested were ctive ginst less thn 60% of Acinetobcter spp or P. eruginos. These dt differ from n epidemiologic study of Acinetobcter spp isolted from BSI in the US, where no imipenem resistnce ws reported (23). In Argentin, s in other Ltin Americ countries, grm-negtive bcilli in BSI isoltes re more prevlent nd show higher resistnce rtes thn the isoltes from Cnd, Europe, nd the US. Regionl differences in ntimicrobil resistnce remin for more importnt pthogens. Antimicrobil Surveillnce progrms re necessry for the development of updted therpy guidelines, screening methodologies to detect ntimicrobil resistnce mechnisms nd infection control mesures to void cross trnsmission of multi-drug resistnce orgnisms. References 1. Munson EL, Diekem DJ, Beekmnn SE, Chpin KC, Doern GV. Detection nd Tretment of Bloodstrem Infection: Lbortory Reporting nd Antimicrobil Mngement. J Clin Microbiol. 2003;41: Fridkin SK, Gynes RP. Antimicrobil Resistnce in Intensive Cre Units Clin Chest Med. 1999;20: Jones RN, Pfller MA. Bcteril resistnce: worldwide problem. Dign Microbiol Infect Dis. 1999;31: Pfller MA, Jones RN, Doern GV, Sder HS, Kugler KC, Bech ML. Survey of Blood Strem Infections ttributble to grm-positive cocci: frequency of occurrence nd ntimicrobil susceptibility of isoltes collected in 1997 in the United Sttes, Cnd, nd Ltin Americ from the SENTRY Antimicrobil Surveillnce Progrm. Dign Microbiol Infect Dis. 1999;33: Diekem DJ, Pfller MA, Schmitz FJ, Smyevsky J, Bell J, Jones RN, Bech M. Survey of infections due to Stphylococcus species: Frequency of occurrence nd ntimicrobil susceptibility of isoltes collected in the United Sttes, Cnd, Ltin Americ, Europe, nd the Western Pcific Region for the SENTRY Antimicrobil Surveillnce Progrm, Clin Infect Dis. 2001;32: Jones RN, Vrnm DJ. Antimicrobil ctivity of brod-spectrum gents tested ginst Grm-negtive bcilli resistnt to ceftzidime: report from the SENTRY Antimicrobil Surveillnce Progrm (North Americ, 2001). Dign Microbiol Infect Dis :

7 Jordá Vrgs L, et l Survey of bloodstrem infection isoltes Sder HS, Jones RN, Andrde BS, Biedenbch DJ. Four-yer evlution of frequency of occurrence nd ntimicrobil susceptibility ptterns of bcteri from bloodstrem infections in Ltin Americn medicl centers. Dign Microbiol Infect Dis. 2003;44: Bntr C, Fmiglietti A, Goldberg M. Three-yer surveillnce study of nosocomil bcteril resistnce in Argentin: the Antimicrobil Committee nd the Ntionl Surveillnce Progrm (SIR) Prticipnts Group. Int J Infect Dis. 2000;4: Bntr C, Fmiglietti A, Goldberg M, Rdice M, nd the Subcomisión de Antimicrobinos SADEBAC, Asocición Argentin de Microbiologí. (2000). SIR: Sistem Informático de Resistenci. Comprtive nlysis during two prevlence periods during 1999 in Bulletin 144. Asocición Argentin de Microbiologí, Buenos Aires, Argentin. 10. Clinicl nd Lbortory Stndrds Institute Performnce stndrds for ntmicrobil susceptibility testing, 15 th informtionl supplement. CLSI document M7-A6. Clinicl nd Lbortory Stndrds Institute, Wyne, PA. 11. Clinicl nd Lbortory Stndrds Institute Performnce stndrds for ntmicrobil susceptibility testing, 15 th informtionl supplement. CLSI document M100-S15. Clinicl nd Lbortory Stndrds Institute, Wyne, PA. 12. Cormicn MG, Mrshll SA, Jones RN. Detection of extended-spectrum b-lctmse (ESBL)-producing strins by Etest ESBL screen. J Clin Microbiol. 1996;34: Jrlier V, Nicols MH, Fournier G, Philippon A. Extended brod-spectrum bet-lctmses conferring trnsferble resistnce to newer bet-lctm gents in Enterobctericee: hospitl prevlence nd susceptibility ptterns. Rev Infect Dis. 1988;10: Pz J. Mnul de Bioestdístic. Ed. CE. Glván Buenos Aires. Argentin Rossi A, Tokumoto M, Gls M, Solog R, Corso A Monitoring ntimicrobil resistnce in Argentin: The WHONET progrm, Rev Pnm Slud Public. 1999;6: Csells JM, Tomé G, Bntr C, Bertolinie P, Blázquez N, Bord N et l Argentinen collbortive multicenter study on the in vitro comprtive ctivity of pipercillintzobctm ginst selected bcteril isoltes recovered from hospitlized ptients. Dign Microbiol Infect Dis. 2003;47: Diekem DJ, Pfller MA, Jones RN, Doern GV, Kugler KC, Bech ML et l Trends in ntimicrobil susceptibility of bcteril pthogens isolted from ptients with bloodstrem infections in the USA, Cnd nd Ltin Americ. Int J Antimicrob Agents. 1996;13: Diekem DJ, Pfller MA, Jones RN, Doern GV, Winokur PL, Gles AC et l. Survey of bloodstrem infections due to grm-negtive bcilli: frequency of occurrence nd ntimicrobil susceptibility of isoltes collected in the United Sttes, Cnd, nd Ltin Americ for the SENTRY Antimicrobil Surveillnce Progrm, Clin Infect. Dis. 1999;29: Jones RN, Biedenbch DJ, Gles AC. Sustined ctivity nd spectrum of selected extended-spectrum b-lctms (crbpenems nd cefepime) ginst Enterobcter spp. nd ESBL-producing Klebsiell spp.: report from the SENTRY ntimicrobil surveillnce progrm (USA, ). Int J Antimicrob Agents. 2003;21: Gles AC, Sder HS, Mendes RE, Jones RN. Slmonell spp. isoltes cusing bloodstrem infections in Ltin Americ: report of ntimicrobil ctivity from the SEN- TRY Antimicrobil Surveillnce Progrm ( ). Dign Microbiol Infect Dis. 2002;44: Pfller MA, Jones RN. MYSTIC (Meropenem Yerly Susceptibility Test Informtion Collection) results from the Americs: resistnce implictions in the tretment of serious infections. J Antimicrob Chemother. 2000;46: Pfller MA, Jones RN, Biedenbch DJ. Antimicrobil resistnce trends in medicl centers using crbpenems: resport of 1999 nd 2000 results from the MYSTIC Progrm (USA). Dign Microbiol Infect Dis. 2001;41: Wisplinghoff H, Edmond MB, Pfller MA, Jones RN, Wenzel RP, Seifert H. Nosocomil bloodstrem infections cused by Acinetobcter species in United Sttes hospitls: clinicl fetures, moleculr epidemiology, nd ntimicrobil susceptibility. Clin Infect Dis. 2000;31: Correspondenci: Dr. Lilin Jordá Vrgs CE. Lbortorio de Bcteriologí. Glván 4102 (1431). Ciudd Autónom de Buenos Aires, Argentin. e-mil: lijord@yhoo.com 17