we reviewed the medical records of patients who had l. monocytogenes isolated from blood and body fluids from sterile sites during 19962008 at the national taiwan university hospital ( ntuh ) , a 2,500-bed hospital in taiwan .
we evaluated disease severity using modified acute physiology and chronic health evaluation ii scores ( 8) .
incidence of nontyphiodal salmonella bacteremia ( ntsb ) during 20002008 in ntuh was calculated for trend comparison of the 2 foodborne illnesses .
only 1 episode was calculated during the same admission for ntsb to avoid the influence of repetitive bacteremia .
isolates from patients with fetomaternal listeriosis ( i.e. , paired isolates from mother and neonate who had listeriosis ) were considered to be the same and only 1 of them was analyzed .
all isolates were analyzed for their serotype by pcr as described , and genetic relatedness was evaluated by pulsed - field gel electrophoresis ( pfge ) by using pulsenet standardized protocols and 2 restriction enzymes ( asci and apai ) ( 2,9 ) .
strains were considered to be of the same cluster if their bands had indistinguishable restriction patterns by both enzymes .
strains with pfge patterns with > 80% similarity by asci and apai profiles were considered to be closely related .
a forward stepwise model with a p value of 0.1 was used , and p<0.05 was considered statistically significant in the multivariate cox proportional hazards model . during the study period ,
listeriosis was diagnosed in 48 patients , and 46 nonduplicated isolates were obtained for further microbiological analysis .
average annual incidence increased from 0.0287 cases per 1,000 admissions during 19962004 to 0.118 cases per 1,000 admissions during 20052008 ( figure 1 ) .
the increase in annual incidence of listeriosis was significantly correlated with years ( p = 0.0045 ) .
the average annual incidences of ntsb were 1.189 and 1.118 per 1,000 admissions during 20002004 and 20052008 , respectively ; it was not significantly correlated with years ( p = 0.50 ) .
age - specific incidence of listeriosis increased at both extremes of age , but especially among patients > 80 years ( figure 2 ) .
all of the patients with listeriosis lived in northern taiwan , and no obvious geographic correlation was observed between listeriosis patients in each year .
incidence ( cases per 1,000 admissions ) of human listeriosis and serotype distribution of all isolates , national taiwan university hospital , taipei , taiwan , 19962008 .
forty - six isolates were available for analysis , including 2 serotype 4b isolates from fetomaternal transmission in 2005 and 2006 and 1 serotype 4b from a pediatric patient ( 2005 ) .
patient distribution and incidence of human listeriosis , by age group , national taiwan university hospital , taipei , taiwan , 19962008 .
all 43 patients had underlying predisposing conditions , and 18 ( 42% ) were > 65 years of age . of the 30 patients with malignancies , 23 ( 77% )
 one female patient had coexisting non - hodgkin lymphoma and colon cancer ; 1 male patient had coexisting non - hodgkin lymphoma , gastric cancer , and bladder cancer . 
initial modified acute physiology and chronic health evaluation ii score , mean  sd : 18.8  7.3 . among the 46 isolates ,
serotype 1/2b was identified most frequently ( 46% ) , followed by 1/2a ( 28% ) and 4b ( 26% ) .
all 46 isolates were susceptible to ampicillin , ertapenem , meropenem , and vancomycin ; 3 isolates were intermediately susceptible to trimethoprim / sulfamethoxazole ; and 4 isolates were nonsusceptible to linezolid ( 10 ) .
sixteen ( 37% ) patients received cephalosporin alone as initial treatment regimens and empirical treatment was effective for only 14 ( 33% ) .
the presence of solid - organ malignancies was a significant negative prognostic factor for 14-day mortality in the univariate analysis ( 95% confidence interval [ ci ] 1.16516.694 ; p = 0.029 ) but not in the multivariate analysis .
the results of the multivariate analysis for 14-day mortality showed that hepatic decompensation at disease onset was a significant negative prognostic factor ( hazard ratio 12.02 , 95% ci 1.84278.470 ; p = 0.009 ) and that the use of effective antimicrobial drugs after culture results were reported was a significant positive prognostic factor ( hazard ratio 0.014 , 95% ci 0.0020.131 ; p<0.001 ) .
log - rank tests performed to compare the difference in survival between patient groups for the 2 variables also had the same results ( p<0.001 ) .
we observed an upsurge of listeriosis beginning in 2005 in ntuh . the increase might not be attributable to common - source outbreaks because no clustering was detected .
the annual incidence of listeriosis has been on the rise in europe since 2000 ( 2,3,11 ) .
the reason is not clear because the increase could not be attributed to outbreak clusters and no increase in pregnancy - related listeriosis was observed ( 2,3 ) .
wong et al . found that l. monocytogenes was isolated in > 50% of pork samples and chicken carcasses ( 6 ) .
semiready foods ( dumplings and meatballs ) and frozen dim sum examined also carried the pathogen ( 34.0% and 4.4% , respectively ) , and > 60% of the isolates were serotype 1 or 4 ( 6 ) . if served undercooked , these foods could be potential transmission sources .
taiwan currently has no strict regulatory policy regarding listeriosis in the food industry and no disease surveillance system . in france ,
serotype 4b was the predominant serotype ( 42%56% ) , whereas serotype 1/2b was more common ( 46% ) in our study ( 2 ) .
none of the isolates were resistant to the tested agents , except for 4 isolates , which were resistant to linezolid .
the contributions of disease severity and antimicrobial drug treatment are difficult to evaluate in population - based studies ( 12 ) .
brouwer et al . reported that up to 30% of adults with l. monocytogenes meningitis did not receive initial adequate antimicrobial drug therapy , and they found no association between that variable and outcome ( 13 ) . a high proportion ( 37% ) of patients in our study
initial disease severity and initial adequate antimicrobial drug therapy was not associated with overall mortality .
we found that mortality was related to hepatic decompensation and effective antimicrobial drug therapy after culture results were reported .
therefore , the incidence of and risk factors for human listeriosis in taiwan could not be determined precisely , and potential outbreaks might have been overlooked .
the retrospective design of our study limited the possibility of identifying the potential vehicles and disease - acquiring behaviors .
an increase of listeriosis was noted since 2005 in our hospital , and all of the affected patients had predisposing factors that hampered their immunity .
dietary education and food management information should be provided to high - risk groups in taiwan .
food monitoring and human disease surveillance systems need to be established in taiwan to control this potentially fatal foodborne disease .
 during 19962008 , a total of 48 patients with listeriosis were identified at a taiwan hospital . 
 average annual incidence increased from 0.029 to 0.118 cases per 1,000 admissions before and after january 2005 . 
 serotype 1/2b predominated ; serotype 4b emerged since 2004 . 
 food monitoring and disease surveillance systems could help control listeriosis in taiwan . 
The Study
Conclusions