You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
during january 2009december 2014 , we isolated 608 s. pneumoniae clinical strains at a 698-bed , university - affiliated hospital in south korea .
we determined mics by using the broth microdilution method according to clinical and laboratory standards institute guidelines ( 5 ) .
we performed antimicrobial resistance tests for levofloxacin , ofloxacin , ciprofloxacin , penicillin , amoxicillin , ceftriaxone , meropenem , erythromycin , clindamycin , vancomycin , linezolid , tetracycline , and tigecycline .
we determined serotypes by using the multiplex pcr assay recommended by the centers for disease control and prevention ( http://www.cdc.gov/ncidod/biotech/strep/pcr.htm ) .
reactions also included an internal positive control targeting all known pneumococcal cpsa regions ( 6 ) .
we sequenced qrdrs of the gyra , gyrb , parc , and pare genes in each isolate ( 7 ) .
we performed multilocus sequence typing to investigate the genetic backgrounds of fluoroquinolone - resistant pneumococci ( 8) and assigned allele numbers and sts by using the pubmlst database ( http://pubmlst.org/spneumoniae ) .
of the 608 clinical s. pneumoniae isolates , 16 ( 2.6% ) were levofloxacin resistant ( mic > 8 g / ml ) .
we collected 1 resistant isolate in 2009 , 3 in 2012 , 5 in 2013 , and 7 in 2014 .
the mean age of patients was 71 years ; 14 were male , and 2 were female .
serotype 11a ( n = 9 ) was most common among the levofloxacin - resistant isolates , followed by serotypes 13 ( n = 2 ) , 19f ( n = 2 ) , 23f ( n = 2 ) , and 6b ( n = 1 ) ( table 1 ) .
the most common sts were st9875 ( n = 5 ) , st8279 ( n = 3 ) , and st9876 ( n = 3 ) , which together accounted for 11 of the 16 levofloxacin - resistant isolates .
nine isolates of st9875 , st9876 , and st10300 were novel sts and had not been identified before this study .   * als , amyotrophic lateral sclerosis ; bl , bronchial lavage ; copd , chronic obstructive pulmonary disorder ; cva , cerebrovascular accident . 
among the 16 isolates , 1 ( hm-646 ) was collected in 2009 ; 3 ( hm-669 , hm-683 , and hm-688 ) in 2012 ; 5 ( hm-730 , hm-762 , hm-781 , hm-787 , and hm-809 ) in 2013 ; and 7 ( hm-854 , hm-878 , hm-953 , hm-970 , hm-1017 , hm-1050 , and hm-1055 ) in 2014 . 
all 16 levofloxacin - resistant isolates contained at least 2 amino acid alterations in the qrdrs of the gyra , parc , and pare genes .
four qrdr mutations occurred with high frequency : ser81phe in gyra was present in all 16 isolates ; ser79phe and lys137asn in parc were present in 14 and 11 isolates , respectively ; and ile460val in pare was found in 15 isolates .
however , lys137asn in parc and asp435val and ile460val in pare are mutations not involved in resistance , according to previous reports ( 9,10 ) .
isolate hm-854 , which was penicillin susceptible , had ser81phe in gyra and asp79asn in parc mutations .
isolate hm-1017 ( serotype 11a , st-8279 ) had 7 qrdr mutations and exhibited the highest resistance against all antimicrobial agents , including levofloxacin ( mic  64 g / ml ) .
st-8279 was associated with 2 different serotypes , 11a ( n = 2 ) and 13 ( n = 1 ) .
the 3 isolates of novel st-9876 had the same qrdr amino acid changes but had different serotypes , 19f ( n = 2 ) and 23f ( n = 1 ) .
the 16 levofloxacin - resistant isolates were also resistant to ofloxacin ( mic > 8 g / ml ) and ciprofloxacin ( mic > 8 g / ml ) ( table 2 ) .
all isolates except 3 had mics > 16 g / ml against amoxicillin and ceftriaxone .
fourteen isolates were meropenem - resistant ( mic > 1 g / ml ) ; all these isolates were susceptible to vancomycin and linezolid .
only 3 sts ( st-99 , st-189 , and st-3173 ) exhibited the lowest levofloxacin mic ( 8 g / ml ) ; all these isolates were susceptible to amoxicillin ( mic < 2 g / ml ) .
* amx , amoxicillin ; cip , ciprofloxacin ; cli , clindamycin ; cro , ceftriaxone ; ery , erythromycin ; i , intermediate ; lev , levofloxacin ; lzd , linezolid ; mer , meropenem ; ofl , ofloxacin ; pen , penicillin ; r , resistant ; s , susceptible ; tet , tetracycline ; tig , tigecycline ; van , vancomycin . 
most of the 16 isolates in our study were of serotype 11a ( n = 9 ) : 5 isolates of st-9875 , 2 of st-8279 , and 1 each of st-10300 and st-99 .
an xdr st-8279 ( serotype 13 ) clone described in 2014 ( 2 ) was closely related to the 9 serotype 11a isolates in our study .
st-8279 is a double - locus ( aroe and xpt ) variant of st-156 , which is closely related to global clone spain9v-3 ( 2 ) .
spain9v-3 is related to 3 st-3642 isolates ( serotype 11a ) reported in taiwan in 2010 ( 11 ) and to 3 mdr st-166 isolates ( serotype 11a ) reported in south korea in 2013 ( 12 ) . in our study , 3 novel sts of mdr s. pneumoniae were identified ( st-9875 , st-9876 , and st-10300 ) .
all the st-8279 , st-9875 , and st-10300 isolates in our study were serotype 11a , with the exception of 1 of the st-8279 isolates .
the st-9875 and st-10300 isolates were single - locus variants ( in the spi and gki genes , respectively ) of st-8279 .
st-9876 is a 1-locus ( aroe ) variant of an st-3384 ( serotype 9v ) clone registered in the pubmlst database .
serotypes 19f and 23f are included in the 13-valent pneumococcal conjugated vaccine ( pcv13 ) , but serotype 11a is not included in pcv13 .
serotype 11a is , however , included in the 23-valent pneumococcal polysaccharide vaccine ( ppsv23 ) .
the us cdc currently recommends the ppsv23 for all adults > 65 years of age and all persons 264 years of age who are at high risk for pneumococcal disease ( 13 ) . through national vaccine programs in south korea , since 2013 , ppsv23 has been provided to all adults > 65 years of age , and since 2014 , 10-valent pneumococcal conjugated vaccine or pcv13 have been provided to young children free of charge ( 14 ) .
in south korea , serotype 11a was the most predominant serotype of the 16 levofloxacin - resistant and xdr s. pneumoniae isolates we found .
seven levofloxacin - resistant s. pneumoniae strains were isolated in 2014 alone ; the dominant serotype was again 11a ( n = 5 ) .
all except 1 of these 7 serotype 11a isolates were resistant to the 9 different antimicrobial agents tested .
s. pneumoniae serotype 11a isolates with novel sts require careful monitoring to combat the increasing prevalence and diversification of mdr pneumococcal strains , especially those with resistance to fluoroquinolones , -lactams , and third - generation cephalosporins .
of 608 streptococcus pneumoniae clinical strains isolated at a hospital in south korea during 20092014 , sixteen ( 2.6% ) were identified as levofloxacin resistant . 
 the predominant serotype was 11a ( 9 isolates ) . 
 two novel sequence types of multidrug - resistant s. pneumoniae with serotype 11a were identified , indicating continuous diversification of resistant strains .