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Background  In 2013, the Clinical and Laboratory Standards Institute recommended inducible clindamycin resistance (ICR) testing on macrolide-resistant  Streptococcus pneumoniae  isolates, which arises due to the  erm B gene. Ribosomal methylation by  erm B confers resistance to macrolides (high-level resistance), lincosamides and streptogramin B. The goal of our study is to characterize the prevalence of ICR among pediatric pneumococcal isolates.    Methods  We identified erythromycin-resistant(R) (minimum inhibitory concentration [MIC] ≥ 1 µg/mL) and clindamycin-susceptible(S) (MIC ≤ 0.25 µg/mL) pneumococcal isolates from pediatric patients seen at Children’s Mercy Hospital from 2007 to 2017. Determination of ICR was achieved via disk approximation (D-zone test) with standard erythromycin (15 µg) and clindamycin (2 µg) disks. Isolates with high-level erythromycin resistance (MIC ≥ 32µg/mL) were also tested for  erm B gene by PCR. Positive and negative controls were used for D-zone test and  erm B PCR.    Results  We identified 289 erythromycin-R pneumococcal isolates; of those 194 (67.1%) were clindamycin-S ( Figure 1 ). One-hundred and sixty-nine isolates were available for ICR testing, 166 (98%) isolates represented non-invasive disease samples. Median age of patients with erythromycin-R and clindamycin-S isolates was 19 (range 0.1 – 180) months. None of the isolates expressed ICR based on the D-zone test. Thirteen of those isolates (7.7%) expressed high-level erythromycin-R (MIC range 32-128 µg/mL); all were negative for  erm B. The most common serotypes/serogroups among erythromycin-R and clindamycin-S isolates were: 15 (n=22), 35B (n=19), 11 (n=16), 6 (n=16), 19A (n=14) and 33 (n=12).Conclusion  Erythromycin-R and clindamycin-S pneumococcal isolates did not express ICR and isolates with high-level erythromycin-R did not carry  erm B. Multicenter studies are needed to determine if ICR testing is required for macrolide-resistant pneumococcal isolates in the PCV13 era.    Disclosures    Liset Olarte, MD, MSc ,  GSK  (Research Grant or Support) Merck  (Research Grant or Support) Pfizer  (Research Grant or Support) Sanofi  (Research Grant or Support)  Douglas S. Swanson, MD ,  Merck  (Research Grant or Support) Pfizer  (Research Grant or Support) Sanofi  (Research Grant or Support)

184. Inducible Clindamycin Resistance Testing on Pediatric Streptococcus pneumoniae Isolates