Continued Presence of Multi-resistant (Non-vaccine) Serotype 15A in Both Invasive and Respiratory Streptococcus pneumoniae Infections in the UK and Ireland

Background: Invasive pneumococcal disease declined after adding conjugate vaccine to infant UK immunization schedules - PCV7 in Sept 2006 and PCV13 in April 2010. The BSAC Resistance Surveillance Project tracked concurrent changes in serotypes and antimicrobial resistance (R) and non-susceptibility (NS) in S. pneumoniaefrom bacteremia and community-onset lower respiratory infections (LRTI).

Methods:40 clinical laboratories in the UK and Ireland collected isolates each year. MICs were measured centrally by BSAC agar dilution and interpreted by BSAC/EUCAST breakpoints. Multiple resistance (MULTI-R) was three or more of: PEN-NS (penicillin-NS); TET-R (tetracycline-R); ERY-R (erythromycin-R); FQ-R (ciprofloxacin MIC>8 mg/L).

Results: In the last two years, PCV13 serotypes stabilised at 21-23% in bacteremia and 16-17% in LRTI (table). In the last seasons, PCV13 types were not among the top-3 serotypes in either bacteraemia or LRTI (see table). Serotype 15A increased in LRTI and topped the ranking in LRTI in the last two years, but fluctuated in bacteraemia (table). Serotype 8 ranked top among 2015 blood isolates at 14% (17% in 2014, 15% in 2013) but only 19^th and 20^thin LRTI at 3% in 2013-14 and 2014-15, respectively. PEN-NS (almost always intermediate), ERY-R, TET-R and MULTI-R all rose in LRTI but not bacteraemia; FQ-R was always rare (<1%). The proportion of MULTI-R isolates was stable at 3% in blood but rose 7% to 12% in LRTI (table). Almost half of these isolates were serotype 15A: 4/8 and 3/7 in blood in 2014 and 2015, respectively; 13/27 and 22/50 in LRTI in 2013-14 and 2014-15, respectively.

Conclusion:Resistance has increased in the last two years in LRTI but not in bacteremia. Non-vaccine serotype 15A contributed substantially to the totality of multiresistance.

S. pneumoniae UK & Ireland Number and %	Bacteremia		Lower Respiratory Infection
	Jan-Dec’14	Most recent Jan-Dec’15	Oct’13-Sep’14	Most recent Oct’14-Sep’15
N of isolates	247	244	376	430
PCV13 types	52 21%	56 23%	63 17%	68 16%
Top 3 serotypes: type and (%)	8 (17%) 22F (9%) 12F (8%)	8 (14%) 22F (11%) 12F (9%)	15A (9%) 23B (7%) 3 (6%)	15A (11%) 11A (8%) 23A (7%)
serotype 15A	18 7%	9 4%	34 9%	46 11%
PEN-NS	17 7%	14 6%	47 13%	71 17%
ERY-R	21 9%	12 5%	64 17%	92 21%
TET-R	20 8%	13 5%	52 14%	81 19%
MULTI-R	8 3%	7 3%	27 7%	50 12%