Antibiotic Susceptibility of Streptococcus pneumoniae To The Most Frequently Prescribed Antibiotics By Region In The USA in 2014

Background: 

Streptococcus pneumoniae is the most common cause of community-acquired bacterial pneumonia (CABP). Resistance to empirically prescribed antibiotics is a continuing major issue. 

Methods:

715 isolates of Streptococcus pneumoniaewere collected from laboratories across the 9 CDC Census regions of the USA in 2014. Susceptibility to the antibiotics listed in the table below was tested according to CLSI M-24.

Results: 

715 isolates were collected in 2014. Rates of resistance ranged from 48.8% in the case of azithromycin, 24.1% with tetracycline and 7.3% in the case of ceftriaxone. All isolates had a MIC to solithromycin of ≤0.25mg/l. Additionally resistance rates by drug by region were also reported.

 

Antimicrobial Agent	MIC50	MIC90	Range	CLSIa
				%S	%I	%R
Solithromycin	0.008	0.25	0.002 — 1	-	-	-
Azithromycin	0.25	>32	0.03 — >32	51.3	0.3	48.4
Ceftriaxone	≤0.06	1	≤0.06 — 8	80.8	11.9	7.3c
				92.7	6.0	1.3b
Penicillin	≤0.06	2	≤0.06 — 8	57.2	29.5	13.3d
				57.2	-	42.8e
				92.7	6.3	1.0f
Tetracycline	≤0.5	>8	≤0.5 — >8	75.2	0.7	24.1
Trimethoprim-Sulfamethoxazole	≤0.5	>4	≤0.5 — >4	69.1	12.2	18.7

 

^aCLSI 2015 criteria; ^bUsing non-meningitis breakpoints; ^cUsing meningitis breakpoints; ^dUsing Oral breakpoints; ^eUsing parenteral meningitis breakpoints; ^fUsing parenteral non-meningitis breakpoints

Conclusion: 

Although current guidelines recommend macrolides and tetracyclines as empiric options for the treatment of out-patient, low risk CABP, almost half of all Streptococcus pneumoniaestrains in the USA are resistant to currently approved macrolides. Resistance and drug-related factors such as tolerability should be considered during empiric selection of antibiotics for CABP.