Simple screening method for gram-positive bacterial XXXX antibiotic tolerance on routine laboratory Bauer-Kirby antibiogram plates.

@entity2176 @entity3405 @entity17286 @entity3401 @entity794 @entity5125 @entity798 @entity5821 @entity16611 @entity3524 @entity8912 @entity3398 @entity3397 @entity3400 @entity869 @entity7100
A simple screening method served to detect @entity3405 antibiotic-tolerant variants of clinical isolates and laboratory control strains of @entity794 , S. epidermis, group B beta-hemolytic streptococci, and @entity5125 . The beta-lactamase(s) of a multiple drug-resistant strain of @entity7100 (isolate No. 19) yielded most consistent results as compared with several other beta-lactamase producers; the @entity7100 beta-lactamase(s) was neutralized by @entity798 . Spot inocula of @entity7100 isolate No. 19, following overnight "induction" with 1 microgram/ml of @entity869 and 3 microgram/ml of @entity5821 in tryptic soya broth, were applied centrally to @entity3405 antibiotic inhibition zones of Bauer-Kirby antibiogram plates (Mueller-Hinton agar, @entity16611 , and diagnostic sensitivity test agar, DSTA) following removal of the appropriate disks. The spot-inoculated plates were incubated overnight at 35 degrees C and inspected for satellite growths of tolerant variants around the @entity7100 spot inocula. Satellite growths of less than or equal to 10 colonies were interpreted to indicate tolerance of the relevant cell wall synthesis inhibitor. The method readily permitted detection of variants tolerant for @entity869 , @entity5821 , @entity3397 , @entity3400 , @entity17286 , and @entity3401 . However, strains documented by minimal inhibitory and minimal bactericidal concentrations to be tolerant for @entity3524 , @entity3398 , @entity8912 , and @entity2176 only rarely gave rise to respective satellite growths. DSTA proved superior to @entity16611 with respect to "rescue" of inhibited tolerant staphylococcal variants; furthermore, the diameters of inhibition zones obtained on DSTA correlated well with those on @entity16611 . Therefore, DSTA was adopted as the routine test medium for clinical staphylococcal isolates.
