antimicrobial resistance can also lead to a delay in the administration of appropriate drugs , and the drugs required to treat resistant pathogens can be toxic ( 2 ) .
antimicrobial resistance has become a worldwide problem with the exception of a few countries in northern europe ( 3 ) .
however , even in sweden , where resistant bacteria are rare , increases of ciprofloxacin- resistant escherichia coli and imipenem - resistant pseudomonas aeruginosa have been reported ( 4 ) .
the prevalence of resistant bacteria varies significantly in different countries as it is influenced by the amount of antimicrobial agents used .
the major reasons for performing surveillance are to determine the size of the problem , to see whether resistance is increasing or not , to detect any previously unknown types of resistance , and to determine whether any particular type of resistance is spreading or is associated with an outbreak ( 1 ) .
analysis of routine susceptibility data has some limitations , which include its inaccuracy , but it does not require much resource .
longitudinal studies of resistance trends are considered most beneficial for the detection of subtle changes in resistance ( 5 ) .
a previous nationwide surveillance in korea showed increasing resistance rates of enterococcus faecium to vancomycin , enterobacteriaceae to fluoroquinolones , the 3rd generation cephalosporins , cephamycins and fluoroquinolones , and p. aeruginosa and acinetobacters to carbapenems ( 6 ) .
it is hoped that the korean national health insurance program , which in 2001 abolished over - the - counter sales of antimicrobial agents and started to scrutinize proper use of antimicrobial agents at hospitals , has had some impact upon reducing resistant bacteria .
the aim of the surveillance in 2001was : to determine any changing trends in the above - mentioned serious resistances in particular , besides the common resistances at korean nationwide surveillance of antimicrobial resistance ( konsar ) hospitals in different locations , and to determine possible emergence of new resistances .
routine susceptibility test data for major aerobic pathogenic bacteria in 2001 were collected from 31 hospitals located in 8 cities / provinces in korea .
however , the data obtained from 30 hospitals were analyzed , excluding one hospital with poor performance versus the who / cdc quality control program . as did in the previous study ( 6 ) , less than 20 isolates of a species from a hospital
main methods of susceptibility testing used were , the nccls disk diffusion test ( 7 ) by 21 hospitals and commercial broth microdilution systems , i.e. , vitek ( biomerieux , marcy l'etoile , france ) or microscan ( dade microscan inc . , west sacramento , ca , u.s.a . ) by 9 hospitals .
methicillin - resistant staphylococci were tested using oxacillin , and penicillin g - nonsusceptible pneumococci were screened mainly by the oxacillin - disk method ( 7 ) .
hospitals were divided into three groups according to location and bed capacity ( 1,000 beds countrywide , < 1,000 beds in seoul , and < 1,000 beds in non - seoul ) . resistance rates did not include intermediates .
the mean resistance rate in each hospital group was calculated from the mean resistance rates at each hospital , to minimize the influence of a large number of isolates at some hospitals ( 8) .
the resistance rates of some important organisms to certain antimicrobial agents were compared to those of previous years .
however , the statistical significances of changes in resistance were not determined , because this depends on the statistical method used ( 8) , and because the purpose of surveillance includes the detection of outbreaks of resistant infections ( 9 ) .
routine susceptibility test data for major aerobic pathogenic bacteria in 2001 were collected from 31 hospitals located in 8 cities / provinces in korea .
however , the data obtained from 30 hospitals were analyzed , excluding one hospital with poor performance versus the who / cdc quality control program . as did in the previous study ( 6 ) , less than 20 isolates of a species from a hospital
main methods of susceptibility testing used were , the nccls disk diffusion test ( 7 ) by 21 hospitals and commercial broth microdilution systems , i.e. , vitek ( biomerieux , marcy l'etoile , france ) or microscan ( dade microscan inc . , west sacramento , ca , u.s.a . ) by 9 hospitals .
methicillin - resistant staphylococci were tested using oxacillin , and penicillin g - nonsusceptible pneumococci were screened mainly by the oxacillin - disk method ( 7 ) .
hospitals were divided into three groups according to location and bed capacity ( 1,000 beds countrywide , < 1,000 beds in seoul , and < 1,000 beds in non - seoul ) .
the mean resistance rate in each hospital group was calculated from the mean resistance rates at each hospital , to minimize the influence of a large number of isolates at some hospitals ( 8) .
the resistance rates of some important organisms to certain antimicrobial agents were compared to those of previous years .
however , the statistical significances of changes in resistance were not determined , because this depends on the statistical method used ( 8) , and because the purpose of surveillance includes the detection of outbreaks of resistant infections ( 9 ) .
the susceptibility data analyzed were of 169,032 isolates , which consisted of 79,167 ( 46.8% ) isolates of gram - positive cocci , and 89,865 ( 53.2% ) isolates of gram - negative bacilli .
proportions of the organisms were : staphylococcus aureus 24.1% , coagulase - negative staphylococci 11.1% , enterococcus faecalis 6.0% , e. faecium 3.8% , pneumococci 1.8% , e. coli 12.0% , klebsiella pneumoniae 7.0% , enterobacter cloacae 3.8% , serratia marcescens 3.4% , non - typhoidal salmonellae 0.6% , acinetobacters 9.4% , p. aeruginosa 16.5% , and haemophilus influenzae 0.4% .
those of s. aureus to oxacillin , erythromycin , and gentamicin were 70% , but the rates of coagulase - negative staphylococci to these antimicrobial agents were somewhat lower .
the resistance rates of s. aureus to cotrimoxazole were lower than that of coagulase - negative staphylococci ( 12% vs. 42% ) , but were higher to ciprofloxacin ( 64% vs. 34% ) and to tetracycline ( 63% vs. 43% ) .
the rate of penicillin - nonsusceptible pneumococci was 72% , and that of ciprofloxacin - resistance was 6% .
the resistance rates of e. faecium were much higher than those of e. faecalis to ampicillin ( 88% vs. 2% ) , and to ciprofloxacin ( 88% vs. 43% ) , but lower to tetracycline ( 23% vs. 81% ) .
the vancomycin resistance rates of e. faecium and e. faecalis were 16% and 1% , respectively .
resistance rate of e. coli to ampicillin was 75% , and to both piperacillin and cotrimoxazole 50% .
resistance rates to other antimicrobial agents were : 9% to ceftazidime , 11% to cefoxitin , 30% to gentamicin , and 28% to fluoroquinolone .
twenty - seven per cent and 20% of k. pneumoniae were resistant to ceftazidime and cefoxitin , respectively , and 12% were resistant to amikacin .
of the e. cloacae isolates , 40% were resistant to cefotaxime and ceftazidime , and 40% were to tobramycin .
imipenem resistance rates of e. cloacae and s. marcescens were 0.4% and 0.6% , respectively .
the resistance rates of s. marcescens to cefoperazone - sulbactam and amikacin , at 15% and 22% , respectively , were the highest among enterobacteriaceae species analyzed .
the resistance rates of p. aeruginosa to ceftazidime and cefotaxime were 21% and 57% , respectively .
the resistance rates to imipenem and amikacin 17% and 26% , respectively . of the acinetobacters , 65% were resistant to piperacillin , cefotaxime , ceftazidime , and aztreonam
. cefepime resistance rate of 52% was the highest among gram - negative bacilli . also , 61% of the isolates were resistant to aminoglycosides , fluoroquinolone and cotrimoxazole .
the imipenem resistance rate of all isolates was 6% . among the 990 isolates of non - typhoidal salmonellae , 35% were resistant to ampicillin , and 4% to cotrimoxazole , but none were resistant to fluoroquinolone . in the case of h. influenzae , some hospitals tested ampicillin susceptibility , while others tested -lactamase production , and still others tested both . among the 699 isolates of h. influenzae , 64% were ampicillin resistant and 66% were -lactamase producers . during the period 1997 - 2001 , the resistance rates of s. aureus to oxacillin and erythromycin remained similar ( fig .
penicillin - nonsusceptible pneumococci declined slightly from 75% to 72% , whereas ampicillin - resistant e. faecium increased steadily from 70% to 88% .
vancomycin - resistant e. faecium isolates increased at all hospital groups : from 2% to 16% at large hospital group , from 2% to 19% at the seoul medium hospital group , and from 7% to 13% at the non - seoul medium hospital group ( fig .
cefoxitin - resistant k. pneumoniae increased from 16% to 20% , and ampicillin - resistant h. influenzae from 58% to 64% ( fig .
the amikacin resistance rate of p. aeruginosa declined slightly from 33% to 26% , while that of acinetobacters gradually increased from 50% to 61% .
4 ) , while the rates to imipenem remained to be 5% to 6% ( fig .
3 ) . ceftazidime- and imipenem - resistant p. aeruginosa were present in all hospital groups ( fig .
the surveillance of resistance is an important part of modern clinical microbiology ( 5 ) , but surveillance methods are considered often inappropriate ( 1 ) .
the surveillance , which is based on collecting data from each laboratory has many problems due to the different methods used for species identification and for susceptibility testing .
more accurate results can be obtained if isolates are collected and tested at a central laboratory ( 5 ) , but this method is very expensive .
current konsar program consists of two different forms of surveillance : one is the analysis of routine susceptibility test data , which were determined by individual participating hospitals , i.e. , this study , and the other is the determination of the prevalence of certain resistances in isolates collected from participants , e.g. , the study on metallo--lactamase - producing strains ( 10 ) . both the necessity and the limitations of surveillance were discussed in a previous study ( 6 ) .
it is difficult to distinguish between community- and nosocomially - acquired pathogens , although their resistance rates differ markedly .
however , some organisms , such as methicillin - resistant staphylococci , vancomycin - resistant enterococci , p. aeruginosa and acinetobacters are typical nosocomial pathogens , while non - typhoidal salmonellae are mostly community - acquired pathogens .
the high proportion of s. aureus ( 24.1% ) among the isolates tested in the present study indicates its continued importance .
methicillin - resistant s. aureus ( mrsa ) is one of the typical nosocomial pathogens ( 11 ) .
the proportion of mrsa and methicillin - resistant coagulase - negative staphylococci , 70% and 69% , respectively , were similar to those reported for 1999 and 2000 ( fig .
surveillance in 1998 - 2000 in kinki , japan , showed the proportion of mrsa was approximately 60% ( 12 ) .
the more active drug against mrsa remained to be cotrimoxazole except for vancomycin , but the rate of 12% was much higher one than the 1% found in japan .
two isolates of true vancomycin - resistant s. aureus were reported in the united states in 2002 ( 13 , 14 ) .
the penicillin - nonsusceptible rate of pneumococci decreased slightly from 78% in 1999 to 72% in 2001 .
a reduction in penicillin - nonsusceptible isolates may be the result of the abolition of over - the - counter sales of common antimicrobial agents in 2001
in japan , the proportion of penicillin - nonsusceptible pneumococci , by the broth microdilution method , was 65% in 1998 and 81% in 2000 ( 12 ) .
we should know that the proportions were based on breakpoint for the treatment of meningitis ( 7 ) .
therefore , pneumonia caused by penicillin - intermediate isolates may respond to penicillin therapy ( 15 ) .
. the ampicillin - resistant rate of e. faecalis , 1% , was slightly lower than the 2% found in 2000 , though still higher than the < 1% found at the coordinating laboratory of the konsar program . it was considered that ampicillin - resistant e. faecalis was due to misidentification of the species ( 1 ) .
these indicate the need to retest the species when an e. faecalis isolate shows resistance to ampicillin .
vancomycin resistance rate of e. faecium in 2001 remained similar to those in 2000 at large- and medium - hospital groups in seoul .
although the rate at the non - seoul medium - hospital group declined from 24% in 2000 to 13% in 2001 ( fig .
2 ) , vancomycin - resistant e. faecium seemed to be established in all hospital groups , as was at the coordinating hospital ( 16 ) .
it is a concern that once a resistance gene has became accumulated to an environment , it is impossible to eliminate them ( 17 ) .
the ampicillin resistance rate of e. coli did increase further and that of h. influenzae increased only slightly .
ampicillin had been a commonly used drug because it was available without prescription , but currently no antimicrobial agent can be bought without a prescription since 2001 .
it is interesting to see the future surveillance could show a downward trend again . in the present study , 64% of the h. influenzae isolates
the proportion of -lactamase - producing isolates in the united states was 36% , while that was only 3% in japan . in a european study ( 18 ) , the prevalence of -lactamase producers varied from 8.1% to 34.8% depending on countries .
it is interesting that in japan 39.6% of the isolates were -lactamase - negative ampicillin - resistant ( blnar ) strains ( 19 ) .
the resistance rates of non - typhoidal salmonellae , i.e. , 35% to ampicillin , 4% to cotrimoxazole and none to ciprofloxacin , were similar to those reported in 2000 ( 6 ) . when empirical antimicrobial treatment of non - typhoidal salmonellae infection is required ( 20 ) ,
cotrimoxazole or ciprofloxacin should be appropriate first - line drugs in korea . in the present study ,
further study is required to determine whether extended - spectrum -lactamase ( esbl)-producing isolates are present . in a korean hospital ,
esbl - producing non - typhoidal salmonellae were detected as early as 1995 ( 21 ) .
fluoroquinolones are increasingly used , as they are one of the three major broad - spectrum classes of antimicrobial agents ( 22 ) .
fluoroquinolone resistance rate of e. coli gradually rose from 24% in 1997 to 28% in 2001 .
the rate of acinetobacters , 65% was only slightly lower than that of the 70% in 2000 ( 6 ) .
expanded - spectrum cephalosporins are ineffective for the treatment of infections caused by esbl - producing isolates of e. coli and k. pneumoniae , although they may be inhibited by low concentrations of these drugs ( 23 ) .
it was reported that bacteremic patients with esbl - producing k. pneumoniae had higher initial treatment failure rates than those with non - esbl - producing isolates ( 24 ) .
also , the cefoxitin resistance rate 20% of k. pneumoniae suggests plasmid - mediated ampc -lactamase production ( 25 ) .
therefore , ceftazidime resistance rates can not reflect the proportion of esbl producers , although high prevalence of esbl - producing k. pneumoniae has been reported in korea ( 26 ) .
cephamycins , such as cefoxitin , are active against esbl - producing isolates , but plasmid - mediated ampc -lactamase - producing isolates are resistant not only to all cephalosporins but also to cephamycins .
carbapenems are very useful drugs as they are stable to hydrolysis even to esbl- and ampc -lactamases ( 27 ) .
although vim-2 metallo--lactamase - producing s. marcescens and e. cloacae have been reported ( 28 , 29 ) , the imipenem resistance rates of e. cloacae and s. marcescens were low ( 0.4% and 0.6% , respectively ) , suggesting that carbapenem - resistant enterobacteriaceae are rare . the imipenem resistance rates of p. aeruginosa to ceftazidime and imipenem remained similar in all hospital groups ( fig .
about 9% of imipenemresistant p. aeruginosa were due to the production of acquired metallo--lactamases ( 30 ) .
29% of acinetobacters isolated in 1996 - 1998 were resistant to imipenem , though the hospital did not use imipenem at that time ( 31 ) . in our present study ,
however , the imipenem resistance rate rose to 13% in 2002 at the coordinating laboratory .
another study showed that approximately 11.4% and 14.2% of imipenem - nonsusceptible isolates possessed the vim-2 or the imp-1 metallo--lactamase gene ( 10 ) .
given the increase in the prevalence of resistant bacteria , the empirical selection of antimicrobial agents becomes increasingly difficult and rapid microbiological testing increasingly crucial .
as was found in the previous study , some laboratories tested susceptibility to too few antimicrobial classes ( data not shown ) .
diagnostic bacteriology results can not be obtained immediately , but clinical microbiologists should remember that early results only can aid the appropriate management of patients , and consequently reduce emergence and the spread of resistance . it was reported that early preliminary microbiology results of blood stream infection had a greater impact on antimicrobial management than susceptibility data ( 32 ) . in conclusion ,
methicillin - resistant staphylococci , penicillin - nonsusceptible pneumococci , ampicillin - resistant e. faecium and h. influenzae , and expanded - spectrum cephalosporin - resistant gram - negative bacilli remain prevalent .
vancomycin - resistant e. faecium , fluoroquinolone - resistant gram - negative bacilli , and imipenem - resistant p. aeruginosa are increasing at all groups of hospitals . given this increasing resistance , not only rapid and accurate routine susceptibility testing , but also the nationwide resistance surveillance become even more important for optimal patient management , the control of nosocomial infection , and eventually to conserve newer antimicrobial agents .
 the 5th year konsar surveillance in 2001 was based on routine test data at 30 participating hospitals . 
 it was of particular interest to find a trend in the resistances of enterococci to vancomycin , of enterobacteriaceae to the 3rd generation cephalosporin and fluoroquinolone , and of pseudomonas aeruginosa and acinetobacters to carbapenem . 
 resistance rates of gram - positive cocci were : 70% of staphylococcus aureus to oxacillin ; 88% and 16% of enterococcus faecium to ampicillin and vancomycin , respectively . 
 seventy - two percent of pneumococci were nonsusceptible to penicillin . 
 the resistance rates of enterobacteriaceae were : escherichia coli , 28% to fluoroquinolone ; klebsiella pneumoniae , 27% to ceftazidime , and 20% to cefoxitin ; and enterobacter cloacae , 40% to cefotaxime and ceftazidime . 
 the resistance rates of p. aeruginosa were 21% to ceftazidime , 17% to imipenem , and those of the acinetobacters were 61% to ceftazidime , aminoglycosides , fluoroquinolone and cotrimoxazole . 
 thirty - five percent of non - typhoidal salmonellae were ampicillin resistant , and 66% of haemophilus influenzae were -lactamase producers . 
 notable changes over the 1997 - 2001 period were : increases in vancomycin - resistant e. faecium , and amikacin- and fluoroquinolone - resistant acinetobacters . with the increasing prevalence of resistant bacteria , 
 nationwide surveillance has become more important for optimal patient management , for the control of nosocomial infection , and for the conservation of the newer antimicrobial agents . 
INTRODUCTION
MATERIALS AND METHODS
Data Collection
Data analysis
RESULTS
DISCUSSION