a packet was sent to the clinical microbiology laboratories of the 77 hospitals in the area . it included a letter describing the project , a questionnaire on hospital characteristics and laboratory testing methods , and a request for existing antibiograms from the most recent period for which completed data were available . the numbers of isolates tested and number of susceptible isolates were added for each antimicrobial agent from all hospitals for each region ( table a1 ) and for all regions combined . data from 10 hospitals were excluded , 7 because the aggregated antibiograms did not include the number of isolates tested and 3 because the antibiogram data predated january 2001 . thirty - one hospitals that were included in the final analysis represented the 4 regions as follows : 16 ( 42% ) of 38 hospitals in the central region , 6 ( 43% ) of 14 in the west , 4 ( 40% ) of 10 in the south , and 5 ( 33% ) of 15 in the southwest . of the hospitals included , 16% did not send a cumulative antibiogram but instead sent their data as a monthly report for a period from 3 months to 1 year . the proposed guidelines for analyzing and presenting cumulative antimicrobial susceptibility data were published by the clinical and laboratory standards institute ( formerly nccls ) in 2002 . the m39-a document provides a standardized means of data extraction for all drugs tested and outlines the most appropriate way to present the data ( 2 ) . in our discussions with laboratory personnel , we found that many laboratories are unaware of these guidelines , and laboratories that use the document find that adhering to all recommendations is difficult . many laboratories lack a microbiology supervisor with insight into the clinical relevance of the results they generate . for example , a laboratory reported 4% vancomycin resistance in streptococcus pneumoniae , but the laboratory staff was not able to explain this finding or recognize the clinical implications . also 2 of the hospitals reported 2 vancomycin - intermediate staphylococcus aureus in their antibiogram . however , the isolates were not available for verification , and the laboratory staff was not aware of the implications of this finding . the staff did not know that such findings should be reported to the illinois department of public health and the centers for disease control and prevention . in all regions , coagulase - negative staphylococci , pseudomonas aeruginosa , and enterococcus faecalis were among the 5 most frequently reported species ( tables a1 and a2 ) . the 10 most frequently reported species in our study are generally comparable to those found in the sentry survey conducted by pfaller et al . isolates tested in the central , west , south , and southwest regions , 27% , 53% , 34% , and 42% , respectively , were resistant to methicillin . of the hospitals that reported speciation of enterococci , e. faecalis was susceptible to vancomycin at 91%99% . however , hospitals from the southwest area reported enterococci other than e. faecalis as enterococcus spp . only . the unusually low susceptibility of e. faecium in our study may be attributed to specimen duplication . in the central illinois region , the susceptibility of s. pneumoniae to penicillin was 64%75% , and 52%77% of isolates were susceptible to erythromycin . the susceptibility of common gram - positive bacteria in our study appears to be lower than reported national averages ( 3 ) . although antibiogram surveillance and active surveillance yield comparable results ( 4 ) , national data may not be directly comparable to our findings because national data used for comparison results from active surveillance with different reporting periods . in spite of expertise and resources available in the united states , the use of antimicrobial drugs in day - to - day practice is suboptimal and directly responsible for multidrug resistance in a number of common pathogens . the factor that converts antimicrobial therapy from " empiric " to " rational " is in vitro susceptibility testing and reporting . however , if these tests are either not conducted or conducted poorly , they are not useful clinically and may create a false sense that therapy is rationally guided . given the differences and shortcomings we reported among laboratories in a region , national recommendations are either unknown or not followed . use of expertise , cooperation , and collaboration at the regional levels may be the simplest and most useful public health measures to optimize the usefulness of diagnostic microbiology in managing infectious diseases . antimicrobial drug use guidelines , if they are based on consistent , reproducible , and comparable data between different laboratories , will produce better outcomes . a master antibiogram for a region would allow a tertiary care institution to consider resistance patterns in hospitals referring patients and to select appropriate " presumptive " antimicrobial therapy or change drugs in nonresponding patients . we hope that the concept of " empiric antimicrobial therapy " would be changed to that of " presumptive antimicrobial therapy " based on host factors , common pathogens , and known susceptibility patterns in any given region . this study has helped us identify serious shortcomings in susceptibility testing methods and reporting , and we hope to address these issues through a regional advisory group . even if following all the recommendations in m39-a are not possible , the second best option may be to have all regional laboratories adhere to the same subset of recommendations . antimicrobial resistance data generated by this approach will have better day - to - day application than will data generated by large national databases . the data will also be useful in monitoring resistance trends in a region over time and assessing the effects of interventions to reduce antimicrobial resistance . we recognize the shortcomings of the data presented in this article but believe them to be the basis for improvement at a fundamental level .
we used hospital antibiograms to assess predominant pathogens and their patterns of in vitro antimicrobial resistance in central illinois , usa . 
 we found a lack of information about national guidelines for in vitro antimicrobial susceptibility testing and differences in interpretation among laboratories in the region .