Almost 30.4% isolates expressed both the ermB and mef genes, whereas 69.6%
were positive for the ermB gene but negative for the mef gene. The resistant isolates had no different carrying proportions of both the ermB and mef genes, as well as only ermB, between the two aforementioned Sorafenib pediatric age groups (P > 0.05) (Table 2). All mef-positive isolates carried the mefE gene. Among the erythromycin-resistant pneumococcal isolates, all the 123 tetracycline-resistant and intermediate isolates carried the tetM gene. However, eight of the 12 tetracycline-susceptible isolates carried the tetM gene. Up to 98.5% (133/135) of the resistant isolates exhibited the cMLSB phenotype, but only two isolates expressed the M phenotype. No iMLSB phenotype was found among the resistant isolates. Table 2 Detection of erythromycin-resistance genes for 135 erythromycin-resistant Raf inhibitor pneumococcal isolates Macrolide-resistance genes No. (%) Age group MICs (μg/mL) distribution (No.) MIC range (μg/mL) ermB mef 0 to 2 years 2 to 5 years 3 12 >256 + + 41 (30.4%) 18 (13.3%) 23 (17.1%) 1 1 39 3- > 256 + – 94 (69.6%) 36 (26.7%) 58 (42.9%) 94 >256 Transposon distribution Among the 135 erythromycin-resistant pneumococci, 76 isolates (56.3%) contained ermB, tetM, int, and xis genes related to Tn6002. 39 isolates (28.9%) were detected for
the presence of ermB, tetM, int, xis, and mefE genes, carrying the transposon of Tn2010. Seven isolates (5.2%) were positive for the ermB, tetM, tnpA, and tnpR genes related to Tn3872. Eight isolates (5.9%) containing the ermB, tetM, int, RVX-208 and xis genes were also positive for the promoter of the aph3’-III gene related to Tn1545/6003 via PCR, of which only two isolates had the mefE gene. The int, xis, tnpA, tnpR, aph3’-III, and mefE genes were not detected in the remaining five isolates (3.7%) (Figure 1). Figure 1 Distribution of Tn 916 – and Tn 917 -related transposons in
the 135 erythromycin-resistant pneumococcal isolates. Multi locus sequence typing A total of 62 STs were found in the erythromycin-resistant S. pneumoniae, of which 28 STs were newly assigned, via MLST analysis. Of the new STs, 19 types were novel combinations of known alleles (ST6875, ST6946, and ST7746 to ST7762). Up to 9 profiles (ST7763 to ST7770 and ST7869) contained 10 new alleles, namely, aroE236, gdh353, gki353, gki354, gki355, recP207, recP208, spi332, spi338, and ddl512. The four predominant STs of all resistant pneumococci were ST271 (11.9%, 16/135), ST81 (8.9%, 12/135), ST876 (8.9%, 12/135), and ST320 (6.7%, 9/135) (Figure 2). Of the common STs, the proportion of ST320 was higher among children aged 0 to 2 years than that of the other age group (P < 0.05). However, the percentage of the other STs, such as ST81, ST236, ST271, ST876, ST386, and ST2572, did not show any difference between the two age groups (P > 0.05).