The National Committee for Clinical Laboratory Standards recommends the use of lysed horse blood-supplemented Mueller-Hinton broth for determining the quantitative antimicrobial susceptibility of Streptococcus pneumoniae. This procedure may be difficult for laboratories using previously prepared or commercial MIC systems. Therefore, a study was undertaken to determine whether previously prepared microdilution trays containing Mueller-Hinton broth without blood could be used for determining the antimicrobial susceptibility of S. pneumoniae by adding whole defibrinated sheep blood to the bacterial suspension used to inoculate the trays. The presence of alpha-hemolysis was used as an indicator of bacterial growth. One hundred isolates of S. pneumoniae selected to represent a distribution of susceptibility patterns were tested by the National Committee for Clinical Laboratory Standards method and the sheep blood-supplemented-inoculum method. Greater than 94% agreement between the two methods was achieved. The sheep-blood-supplemented-inoculum procedure was highly reproducible and easy to perform and provides an acceptable alternative for determining the MICs for S. pneumoniae for laboratories using previously prepared or commercial microdilution systems.

suMMxRY Efficacy of single-dose spectinomycin (TRO: 2 g intramuscularly) was compared with that ofaqueous procaine penicillin G (APPG: 4.8 x 106 units) plus 1 g ofprobenecid for treatment of gonococcal urethritis and cervicitis. Cure rates ofthe 210 patients who received TRO and 190 patients who received APPG were 97-6% and 91 1%, respectively. MICs of antibiotics were determined using the agar dilution method. Those isolates with MICs of APPG of < 1.0 ug/ml had low failure rates (2.9%), while strains with increased resistance to APPG (MICs > 1.0 pg/ml) had higher failure rates (24%). Treatment failures seen with TRO were not correlated to isolates with the higher MICs. Clinical results suggest TRO could be given for treatment ofgenital gonorrhoea in Puerto Rico due to the high prevalence of both chromosomally-mediated penicillin-resistant Neisseria gonorrhoeae (20%) and penicillinase-producing Neisseria gonorrhoeae (7.5%) strains and the high rate of failure seen with the use of APPG. The failure ofpenicillin and spectinomycin regimens in the clinical setting are known to vary according to geographic location.'`3 The reports of significant spatial and prevalence variation in the distribution of penicillinase-producing Neisseria gonorrhoeae (PPNG),' chromosomally mediated penicillin-resistant Neisseria gonorrhoeae (CMRNG) strains,9" and spectinomycin-resistant isolates'2-'5 are causes for concern among health-care practitioners world-wide.

S28 Objectives To compare the influence of the amount of in vivo shaped root canals (RC) in static cyclic fatigue (CF) resistance in ProTaper Universal (PTU) S1 instruments at different points of curvature.