one fourth of the population lives in the capital , nuuk , while the rest live in 16 towns and several settlements ( the districts ) scattered around the island .
most persons ( 86% ) are native greenlanders ; the rest are caucasians , mostly danes .
the laboratory at queen ingrids hospital in nuuk is the only microbiologic laboratory in greenland . from laboratory files ,
we identified all bacterial isolates from invasive disease cases reported from january 1 , 1995 , though december 31 , 2004 . demographic information about patients was obtained from the civil registration system of greenland ( 6 ) .
the study was approved by the commission for scientific research in greenland and reported to the danish data protection agency .
positive blood cultures were detected by using manual readings of blood culture bottles from statens serum institut , copenhagen , denmark ; beginning in 1999 , the bactec / alert system ( organon teknika , turnhout , belgium ) was used . in this system , 2830 ml of blood
positive samples are characterized by gram stain and cultured on blood agar supplemented with 5% defibrinated horse blood .
antigen / antibody tests are carried out for s. pneumoniae , n. meningitidis , and h. influenzae ( the last 2 only on cerebrospinal fluid ) .
serotyping and group typing of s. pneumoniae and h. influenzae ( quellung method ) and n. meningitidis ( latex agglutination method ) are performed at statens serum institut . in total ,
281 unique bacterial isolates from 254 episodes of invasive disease among 242 patients were identified : 72% of isolates in blood , 18% in cerebrospinal fluid , and 10% in other samples .
of the 254 episodes , 47% occurred among patients from the districts and 53% in patients from nuuk . in 53% of episodes among patients from the districts ,
there were no differences in age , sex , ethnicity , underlying conditions , or mortality rates between district and nuuk patients , but greenlandic patients were younger ( median 46 years , 25%75% quartiles 1759 years ) than danish patients ( median 57 years , 25%75% quartiles 4462 years ) ( p = 0.07 ) .
twenty different bacterial species or groups were identified ( 22 isolates could not be characterized by species ) ; the most numerous were s. pneumoniae , staphylococci , and e. coli ( table ) . for most bacteria , the invasive disease incidence varied by age in a u - shaped fashion ( figure 1 ) .
most n. meningitidis cases ( 73% ) occurred in children < 10 years of age , the 4 cases of h. influenzae group b infection occurred in children < 1 year of age , and the youngest case - patient with gbs was 12 years of age . * per 100,000 population . 
most numerous serotypes were 12f ( 9 ) and 22f ( 5 ) ; 41 isolates not were serotyped .
# two isolates in group b , 4 in group c , and 9 not grouped .  * * s .
bacillus sp . ( 1 ) , corynebacterium ( 1 ) , clostridium perfringens ( 2 ) , listeria monocytogenes ( 1 ) , and propionebacterium sp .
incidence of invasive bacterial disease did not differ according to patient sex but did differ markedly according to ethnicity and region .
the age - adjusted rate ratio was 1.8 ( 95% confidence interval [ ci ] 1.12.9 ) for greenlanders compared with danes and 3.5 ( 95% ci 2.74.4 ) for persons living in nuuk compared with persons living in the districts , a rate ratio observed for almost all bacterial species .
the overall incidence of invasive bacterial isolates increased during the study period from 17.9/100,000 in 1995 to 79/100,000 in 2004 ; the most marked increase occurred in 19971998 , when incidence almost doubled .
the increase occurred mainly in blood culture samples ; cerebrospinal fluid samples remained constant over time .
the increase in isolates from blood cultures occurred equally in nuuk and in the districts and for most bacteria , although the incidence of n. meningitidis remained constant ( figure 2 ) .
h. influenzae group b isolates were not identified after 1998 ( childhood vaccination was introduced in 1997 ) ; the 5 gas isolates first appeared in 20012004 .
s. pneumoniae was the most commonly involved , confirming the importance of this pathogen in native populations in the arctic ( 13 ) .
however , the second and third most frequent invasive bacteria were e. coli and s. aureus , a finding which , to our knowledge , had not been described before in greenland .
in contrast , the 5 bacteria included in the circumpolar surveillance system accounted for only 47% of microorganisms ( 5 ) .
surveillance of these 5 bacteria is relevant , though , as they are all serious , potentially fatal diseases of infants or children and are associated with some form of preventive action ( either vaccines or prophylaxis ) .
s. aureus and e. coli are not amenable to simple specific public health actions , so surveillance for these infections is less useful .
evaluation of outcome and risk factors for s. aureus and e. coli in arctic areas may lead to potential preventive or clinical care options .
worldwide , microbiologic causes of bacteremia have shifted from gram - negative organisms being the most common in the 1970s to gram - positive organisms with coagulase - negative staphylococci , s. aureus , and enterococci being the most frequent in the last part of the 20th century ( 8) .
likewise , we found gram - positive bacteria in 67% of invasive disease cases and gram - negative bacteria ( mostly enterobacteriaceae ) in 33% and increasing incidence of both gram - positive and gram - negative bacteria over the study period .
the overall incidence of invasive bacterial disease was 3.5-fold higher among nuuk patients than among district patients .
most likely this finding represents sampling bias ; microorganisms sent from the districts are less likely to survive than samples taken in nuuk , and district doctors may be less likely to submit samples than nuuk doctors , given the longer time to receive test results .
however , we can not confirm this explanation because of lack of information on the total number of submitted samples .
furthermore , the 39% higher average income in nuuk compared with the rest of greenland makes a nuuk / district invasive disease incidence rate ratio of 3.5:1 less likely ( 7 ) .
the difference suggests that the true invasive disease rates in greenland may be much higher than those found in this study or reported to ics .
a clear recommendation from this study is to develop a more accessible , rapid , and reliable diagnostic system for districts outside of nuuk .
the lower age - adjusted invasive bacterial disease incidence in danes than greenlanders may be explained by the  healthy worker effect .
 danes in general come to greenland to work and belong to higher social classes and live in better housing conditions than the general population of greenland , factors that may reduce the risk for infection ( 9 ) .
hence , although genetic factors may account for some of the difference , the difference is probably confounded by environmental and social factors .
the increase in invasive bacterial isolates during the study period most likely represents changes in submission or detection practices .
the increase occurred almost exclusively in blood cultures , and a new blood culture detection system was introduced in 1999 .
 invasive bacterial disease occurs frequently among native populations in the arctic . 
 although a variety of bacteria are involved in invasive bacterial disease in greenland , streptococcus pneumoniae , escherichia coli , staphylococcus aureus , and other staphylococci are responsible for most cases ( 69% ) ; incidence varies according to region and ethnicity . 
The Study
Conclusions