TABLE 1

Number of nymph-derived spirochete isolates used for each of the 22 combinations of Borrelia species and yeara

YrNo. of nymph-derived isolates tested (total no.)
B. afzeliiB. garinii
Infected nymphsUninfected nymphsInfected nymphsUninfected nymphs
200020 (51)b234 (599)c20 (41)297 (609)
200117 (37)d295 (643)18 (37)312 (643)
200216 (69)153 (661)19 (39)336 (691)
200312 (21)261 (458)14 (19)338 (460)
200413 (21)298 (448)14 (16)396 (453)
200519 (88)104 (459)19 (29)339 (518)
200620 (57)171 (490)15 (33)249 (514)
200720 (41)275 (564)20 (62)175 (543)
200818 (31)347 (598)20 (54)212 (575)
200920 (51)211 (540)13 (14)535 (577)
201018 (58)156 (503)18 (32)297 (529)
  • a We randomly selected a maximum of 20 nymph-derived isolates for NGS (the total number of infected nymphs is shown in parentheses) for each combination of Borrelia species and year. To calculate the absolute frequency of each strain (F3 in Tables 2 and 3), we used a subsample of uninfected nymphs (the total number of uninfected nymphs is shown in parentheses) for each combination of Borrelia species and year. This subsample of uninfected nymphs is proportional to the subsample of infected nymphs.

  • b In the year 2000, 51 nymph-derived cultures tested positive for B. afzelii. We randomly selected 20 of these 51 isolates of B. afzelii and determined the community of ospC strains using NGS.

  • c In the year 2000, 599 nymph-derived cultures did not test positive for B. afzelii. We calculated the absolute frequencies of the B. afzelii ospC strains (F3 in Tables 2 and 3), using a subsample of 234 cultures [(20/51) × 599 = 234] not infected with B. afzelii.

  • d In the year 2001, 37 nymph-derived cultures tested positive for B. afzelii, but only 17 of these 37 isolates of B. afzelii had sufficient material for NGS.