An exception to the rule “no association between antibiotic resistance and decreased microbicidal efficacy of disinfectants”: Orthophthalaldehyde (OPA) and Pseudomonas aeruginosa isolated from ICU patients.


P. aeruginosa



Antibiotic resistance and decreased susceptibility to disinfectants is no associated in divers microorganisms, but we have find an exception a this rule:   P. aeruginosa  vs orthophthalaldehyde (OPA).


 Bactericidal effect of OPA at 10 minutes upon endodoncy files contaminated with an ATCC strain (control) and 206 strains of P. aeruginosa recently isolated from 206 ICU and paraplegic patients, of a tertiary university hospital, in two years.

 Results and Discussion:

Differences in bactericidal effect of OPA were found between the strains isolated in each period (decreased susceptibility in the first year), but in each year the statistical differences (p<0.05) were maintained according to whether the strains were susceptible to antibiotics, resistant (one family of antibiotics) or multi‑resistant (more than one family). By contrast, there were no differences depending on the type of sample (as sputum, urine, feces, pharynx) or the type of ICU (as adults, newborns, burn patients). OPA against the 15 strains with an effect of less than 3.5 log in 10 minutes, showed a total bactericidal effect in 15 minutes.

In conclusion, an association exists between antibiotic resistance and decreased susceptibility to OPA. Normally, does not imply an increase in disinfection time, but it must be considered in endoscope disinfection.



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