  the population we tested included patients treated by physicians within the university of pennsylvania health system , which encompasses several philadelphia - area hospitals .
most isolates were from outpatients seen at the hospital of the university of pennsylvania or the presbyterian medical center ; both serve the university of pennsylvania community and populations living in west philadelphia .
stool samples were collected as part of the routine evaluation of patients with diarrheal illness and sent in cary - blair transport medium to the clinical microbiology laboratory at the hospital of the university of pennsylvania for processing .
campylobacter organisms were isolated and identified to species by using published methods ( 7 ) . only c. jejuni subsp .
each isolate tested represents a single patient .   from 1995 through 2001 , 404 patient isolates were obtained from routine stool cultures ; 297 ( 73.5% ) were available for susceptibility testing .
the age distribution was nearly identical for both sexes ( males : median 33 yrs , mean 35 yrs [ range 186 yrs ] ; females : medium 33 yrs ; mean 36 yrs [ range 895 yrs ] ) .
susceptibility to ciprofloxacin and erythromycin was determined with the e - test ( ab biodisk , solna , sweden ) method .
organisms were tested on mueller - hinton blood agar medium and incubated at 37c in microaerobic conditions .
the breakpoints used for resistance were 4 g / ml for ciprofloxacin and 8 g / ml for erythromycin ( 5 ) .
flagellin gene typing ( fla typing ) was performed by using modified consensus primers , described by wassenaar and newell ( 8) , and digested with ddei as previously described ( 9 ) .   as reported previously , fluoroquinolone - resistant c. jejuni
were not detected among 142 patient isolates tested from 1982 to 1992 at our institution ( 6 ) .
two hundred and ninety - seven patient isolates were tested between 1995 and 2001 for susceptibility to ciprofloxacin and erythromycin .
resistance rates ranged from as low as 8.3% in 1996 to 40.5% in 2001 ( figure 1 ) .
in contrast , erythromycin resistance fluctuated between 0% and 5% during the same period ; in 2001 erythromycin resistance was 3.5% .
when all isolates tested during the study period are considered , 28.9% of isolates were resistant in the first calendar year quarter , 19.7% in the second quarter , 20% in the third quarter , and 19.2% in the fourth quarter . however , resistance isolates were more frequent beginning in october 2000 and extending through april 2001 ( figure 2 ) .
number of isolates tested : 198292 ( n=142 ) , 1995 ( n=24 ) , 1996 ( n=48 ) , 1997 ( n=61 ) , 1998 ( n=37 ) , 1999 ( n=22 ) , 2000 ( n=48 ) , and 2001 ( n=47 ) .
number of isolates tested for each quarter : q1 : 13 , q2 : 13 , q3 : 22 , q4 : 10 , q5 : 16 , q6 : 15 , q7 : 12 , q8 : 14 .
a clear bimodal distribution of mics exists , with 96% of susceptible isolates with mics 0.5 g / ml ; except for one isolate , all resistant isolates had mics 32 g / ml . distribution of ciprofloxacin mics in campylobacter jejuni , 19952001 .  
we used molecular typing by restriction fragment length polymorphism analysis of campylobacter 
 flaa to determine whether certain fla types were associated with fluoroquinolone resistance .
there were at least four isolates represented in the type ( fla types 1 , 7 , 9 , 10 , 13 , 15 , 16 , 25 , 33 , 44 , 48 , 49 , 53 , 57 , 80 , 86 ) .
the proportion of resistant to susceptible isolates was no more than 0.25 and ranged from 0.07 to 0.25 .
  we have observed a dramatic increase in fluoroquinolone - resistant c. jejuni in patients treated within our health system from 1995 to 2001 with a resistance rate of 40.5% in 2001 .
in contrast , erythromycin - resistant c. jejuni has remained at a low rate ( < 5% ) for nearly 20 years . before 1992 , fluoroquinolone - resistant c. jejuni had not been detected at our institution ( 6 ) . whether fluoroquinolone resistance emerged during 19931994 is unknown because isolates from that period were not available .
similarly , a survey of isolates from 19 u.s . counties in 1989 and 1990 did not find any fluoroquinolone - resistant c. jejuni ( 1 ) . from 1997 through 2000 , narms reported 13% , 13% , 18 % , and 14% fluoroquinolone - resistant c. jejuni , respectively ( 5 ) .
erythromycin - resistant c. jejuni occurred in 8% , 3% , 2% , and 1% of isolates from 1997 to 2000 among isolates tested by narms ; our data parallels these national data ( 5 ) . the distribution of ciprofloxacin mics among c. jejuni from our survey also parallels narms data between 1997 and 2000 ( 5 ) .
fluoroquinolone - resistant isolates exhibited high - level resistance with mics > 32 g / ml .   the risk factors for acquiring fluoroquinolone - resistant c. jejuni in the united states have not been defined ; however , foreign travel was identified by smith and colleagues as an important risk factor ( for 75% of fluoroquinolone - resistant c. jejuni ) in minnesota residents ( 4 ) . other , unidentified factors were important , however , since the rest of infections were domestically acquired .
use of a fluoroquinolone within the month before the collection of the stool sample was also identified as a potential risk factor ( 4 ) .
the increase in fluoroquinolone - resistant c. jejuni from 1996 through 1998 was temporally associated with the licensure of fluroquinolones for use in poultry in the united states ( 4 ) .
several studies from european colleagues noted this temporal relationship between use of fluoroquinolones in animals and resistance among human isolates in the 1980s ( 3 ) .  
the reasons for such a dramatic increase in fluoroquinolone - resistant c. jejuni in our population are unknown .
we did observe increasing rates of resistance for several quarters during the last 2-year survey period . whether this increase is indicative of foreign travel patterns by our patients
future studies should focus on identifying the factors for acquisition of fluoroquinolone - resistant c. jejuni as well as the clinical implications of infection with such strains .
some evidence suggests that infection with fluoroquinolone - resistant c. jejuni results in prolonged illness .
the duration of diarrhea among patients treated with a fluoroquinolone in the minnesota study was significantly longer if the patient had a fluoroquinolone - resistant infection ( median 10 days ) versus a fluoroquinolone - susceptible infection ( median 7 days)(4 ) . based on national trends and our own local data
 fluoroquinolone - resistant campylobacter jejuni has been observed worldwide and is now being seen in the united states . among patients in our health - care system in pennsylvania , fluoroquinolone - resistant c. jejuni were not observed from 1982 to 1992 ; however , resistance increased to 40.5% in 2001 . 
 resistance to erythromycin remains at a low level ( < 5% ) . 
The Study
Conclusions