Resumen

CASELLAS, José María et al. In vitro activity at serum and urinary levels of amoxicillin and amoxicillin-sulbactam against 820 Escherichia coli strains isolated from community acquired urinary tract infections: South American collaborative study. Rev. chil. infectol. [online]. 2003, vol.20, n.1, pp.11-18. ISSN 0716-1018.  http://dx.doi.org/10.4067/S0716-10182003000100002.

We previously showed urinary activity against Escherichia coli both after oral amoxicillin-sulbactam and sulbactam alone. A study was performed in 10 laboratories from 8 countries to determine the etiology of community acquired lower urinary tract infections (CALUTI) in patients aged 3-to 7 years in South America. Each laboratory sent data from 100 consecutive isolates including susceptibility to amoxicillin and amoxicillin-sulbactam by agar diffusion and also sent 20 consecutive E. coli isolates resistant (R) to amoxicillin-sulbactam to CEA reference laboratory, were MICs were determined for amoxicillin, amoxicillin-sulbactam (2/1) and sulbactam. Urines from 12 volunteers who received a single oral dose 500/500 mg amoxicillin-sulbactam were collected at 0-2; 2-4 and 4-6 h and urinary inhibitory titers (UIT) were determined against 5 R and 1 susceptible (S) isolates from each center. Levels of amoxicillin and sulbactam were determined. Results: Etiology: E. coli 820/1000 (82%) was prevalent; P. mirabilis and K. pneumoniae (4,3% each), S. saprophyticus 4,1% other 5,3%. Diffusion test: 59,4% E. coli were R to amoxicillin, 16,9 intermediate (I) and 23,7 S whereas results for amoxicillin-sulbactam were 28% R; 19,2 I and 52,8 S. MICs: 102 E. coli R to amoxicillin-sulbactam were studied; MIC90s (µg/ml) were the following: amoxicillin > 2.048; amoxicillin-sulbactam 256/128 and sulbactam alone 128. UITs: ranged from > 1/32 at 2 h dose; 1/16-1/4 h and 1/4-1/2 at 6 h against all the isolates. Antibacterial urine levels (µg/ml) obtained for amoxicillin and sulbactam respectively were at 2 h 1.414 and 1.904; at 4 h 691 and 1.257 and at 6 h 462 and 641. Our results confirm the prevalence of E. coli and explain discrepancies between resistance shown by agar diffusion test and clinical success observed in the treatment of CALUTI.

Palabras clave : Urinary tract infections; amoxicillin-sulbactam; Latin America.

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