Performance Information Vet use only Performance of plates read manually was measured in three sites. Each centre tested Enterobacteriaceae, streptococci, staphylococci and pseudomonas-like organisms. 93.9% of manually read MIC s were within +/- 1 log dilution of the reference microdilution panel MIC. Only rare (0.6%) very major errors were observed. Performance of automated read plates was measured in three sites (13,15). Among the isolates of gram-negative bacilli tested against 17 antimicrobial agents, automated MIC s were within +/- 1 twofold dilution of the manually read MIC in 95.3% of instances. One half of the discrepancies were with Proteus mirabilis ß-lactamase combinations, a problem that was resolved when the inoculum was dropped to 1x10 4 cfu/ml. Among the isolates of gram-positive bacilli tested against 11 antimicrobial agents, automated MIC s were within +/- 1 twofold dilution of the manually read MIC in 93.5% of instances Performance of breakpoint plates read manually was measured in one site (4) and compared to a standardized disk diffusion procedure. Enterobacteriaceae, pseudomonads and other Gram negative non-fermenting organisms, Staphylococcal species including MRSA and Streptococci and Enterococci were tested. Concordance was observed in 88.1% of cases. There were 9.6% minor discrepancies, 1.0% major errors and 1.3% very major errors. Arbitration of major and very major errors with a full range MIC procedure confirmed the Sensititre results in 53.4% of cases. A single organism/antimicrobial combination, the non-enterococcal Streptococci tested against aminoglycosides yielded a significant number of very major errors with the Sensititre System. These errors were probably due to poor organism growth in the Mueller-Hinton broth. The performance of automated reading of breakpoint plates was evaluated in a three centre trial (30). 6086 different organism-antimicrobial agent comparisons were made with Enterobacteriacae isolates against 17 antibiotics. Concordance between the automated read and manual read was noted in 97.2% of cases with 0.8% of very major errors, 0.4% major errors and 1.6% minor errors. 1377 different organism-antimicrobial agent comparisons were made with P. aeruginosa isolates against 17 antibiotics. Concordance between the automated read and manual read was noted in 92.2% of cases with 1.8% of very major errors, 0.07% major errors and 5.9% minor errors. A study conducted by the CDC (6), resistant strains of Enterococcus spp were tested with Sensititre plates read manually and compared to frozen panels prepared according to CLSI (NCCLS) requirements. In summary, there was 100% essential and category agreement for ampicillin; 91% essential, 94% absolute category agreement (category agreement regardless if within +/-1 dilutions from reference), and 96% category agreement for vancomycin. Performance of manually read MIC plates against S. pneumoniae isolates against 6 antimicrobics was measured at CDC and compared to CLSI (NCCLS) broth microdilution test procedure (8). MIC s were within +/- doubling dilution in 98.8% cases of organism antibiotic combination. for individual antibiotics ranged from 96.8% to 100%. Manually read MIC s were within +/- 1 doubling dilution of MIC s from CLSI (NCCLS) reference broth microdilution procedure in 100% of cases (7) for well characterised S. pneumoniae isolates with decreased susceptibility to penicillin. PERFORMANCE CHARACTERISTICS The agreement rates listed below reflect the18 hour fluorogenic autoread results compared to the same plate read visually at 18 hour. Data was determined to be in essential agreement if the MIC agreed with the reference result +/- 1 dilution. These results were interpreted to be in categorical agreement if they agreed qualitatively (S, I, R) according to the MIC interpretive categories in NCCLS M100 (27) and M31 (28). For trial sites, the overall essential agreement rate for Gram negatives was 95.6-99.7% and the overall categorical agreement was 95.8-99.8%.The overall essential agreement rates for the Gram positive organism data sets tested was 93.0-100%. The categorical agreement is 93.6 100%.
TABLE 1 18 HOUR AUTOREADER BREAKPOINT AGREEMENT RATES Breakpoints * +/- 1 dilution Breakpoints * +/- 1 dilution AMIKACIN 16, 32 99.2% 99.8% AMPICILLIN 8, 16 98.4% 98.9% 8 99.2% 99.2% APRAMYCIN 16 100% - BACITRACIN 2 99.0% - CARBENICILLIN 16, 32 98.6% 98.8% 16 85.0% - CEFAZOLIN 8, 16 97.6% 98.0% CEFOTAXIME 8, 32 96.7% 99.2% CEFOXITIN 8, 16 98.9% 99.4% CEFTAZIDIME 8, 16 98.9% 99.5% CEFTIOFUR 1. 2 96.0% - 1, 2 99.0% - CEFTIZOXIME 8, 32 98.5% 99.6% CEFTRIAXONE 8, 32 96.5% 99.0% CEFUROXIME 8, 16 97.6% 98.3% CEPHALOTHIN 8, 16 99.3% 99.6% 8, 16 98.4% 99.7% CHLORAMPHENICOL 8, 16 95.2% 99.4% 8, 16 93.5% 98.7% CIPROFLOXACIN 1, 2 99.6% 99.7% 1, 2 98.5% 99.3% CLINDAMYCIN 0.5, 2 97.6% 98.7% ENROFLOXACIN 1, 2 100% - 1, 2 90.0% - ERYTHROMYCIN 0.5, 4 97.2% 99.6% GENTAMICIN 4, 8 99.0% 99.5% 4, 8 96.8% 98.5% IMIPENEM 4, 8 97.2% 98.9% 4, 8 99.2% 99.2% NALADIXIC 8 98.0% - NETILMICIN 8, 16 99.0% 99.6% NEOMYCIN 8 93.0% - 8 99.0% - NORFLOXACIN 4, 8 98.4% 99.2% NOVOBIOCIN 4 98.0% - 4 99.0% - ORBIFLOXACIN 8 94.0% - 8 91.0% - OXACILLIN + 2% NaCl 0.5, 2 99.4% 99.8% PENICILLIN (Staphylococci only) 0.03, 0.12 99.7% 99.7% PIPERACILLIN 16, 64 98.1% 99.0% POLYMIXIN B 0.5-2 100% - 0.5-2 96.3% RIFAMPIN 1, 2 93.1% 97.8% SPECTINOMYCIN 8, 16 93.0% - 8, 16 100% - SULFISOXAZOLE 128 96.0% - - SULPHACHLOROPYRIDAZINE 20, 40 95.0% - - SULPHADIMETHOXINE 20, 40 92.0% - 20, 40 81.0% - SULPHATHIAZOLE - 256 89.0% - TIAMULIN 8, 16 99.0% - 8, 16 100% - TICARCILLIN 16, 64 96.6% 97.3% 97.3% TICARCILLIN / CLAVULANIC 99.6% 16/2,64/2 98.0% 99.6% TOBRAMYCIN 4, 8 99.6% 99.8% 99.8% TRIMETHOPRIM / 2/38 96.8% 99.1% 2/38 93.7% 94.2% SULPHAMETHOXAZOLE TYLOSIN TARTRATE 5, 10 98.0% - 5 96.0% -
18 HOUR AUTOREADER MIC AGREEMENT RATES FOR NON-FASTIDIOUS GRAM NEGATIVE AND GRAM POSITIVE ORGANISMS AMIKACIN 99.7% 99.7% AMOXICILLIN 99% NA NA NA AMOXICILLIN / CLAVULANIC 98.8% 100% 96.2% 99.4% AMPICILLIN 99.5% 99.8% 98.2% 99.5% APRAMYCIN 100% NA 100% NA AZITHROMYCIN 100% NA CARBENICILLIN 98.3% 99.0% CEFDINIR 99.5% 99.5% CEFOTAXIME 95.6% 95.8% CEFOVECIN 99.4% 100% 97.3% 98.6% CEFOXITIN 99.5% 99.6% CEFQUINOME 100% 100% CEFTAZIDIME 98.7% 99.3% CEFTIOFUR 99.5% 99.5% 97.2% NA CEFTIZOXIME 98.5% 98.9% CEFTRIAXONE 98.9% 99.6% CEFUROXIME 97.7% 98.5% CEPHALEXIN 98.8% NA CEPHALOTHIN 98.8% 99.9% 98.5% 99.2% CEPHAPIRIN 99.5% 99.5% CHLORAMPHENICOL 99.8% 99.8% 99.9% 99.9% CIPROFLOXACIN 99.2% 99.7% 99.1% 99.1% CHLORTETRACYCLINE 98.4% NA 100% NA CLINDAMYCIN 98.8% 98.8% COLISTIN 94.9% NA DANOFLOXACIN 99% NA 98.7% NA DIFLOXACIN 99% NA ENROFLOXACIN 97.7% NA 97.7% NA ERYTHROMYCIN 98.2% 99.2% FLORFENICOL 98.9% NA 96.5% NA GENTAMICIN 99.5% 99.8% 97.7% 99.2% IMIPENEM 97.3% 98.2% 97.6% 98.3% KANAMYCIN 94% NA MARBOFLOXACIN 100% 100% NALIDIXIC 100% 100% NEOMYCIN 93.6% NA 93.6% NA NETILMICIN 99.0% 99.0% NITROFURANTOIN 98.4% 98.4% NOVOBIOCIN 100% NA ORBIFLOXACIN 99.5% NA 96.5% NA OXACILLIN + 2% NaCl 96.2% 99.3% OXYTETRACYCLINE 95.6% NA 95.6% NA PENICILLIN 99.0% 99.6% PENICILLIN / NOVOBIOCIN 98.4% NA 100% NA PIPERACILLIN 99.8% 99.9% PIRLIMYCIN 100% NA POLYMIXIN B 97% NA 97% NA QUINUPRISTIN / DALFOPRISTIN 92.3% 99.1% RIFAMPIN 98.2% 98.2% SARAFLOXACIN 97.8% NA 97.7% NA SPARFLOXACIN 95.6% 99.0% SPECTINOMYCIN 97.4% NA 97.4% NA SULPHACHLOROPYRIDAZINE 98.4% NA 100% NA SULPHADIMETHOXINE 100% NA 98.6% NA SULPHATHIAZOLE 96.2% NA 95.6% NA
TETRACYCLINE 98.7% 99.0% 99.5% 99.9% TICARCILLIN 98.1% 98.9% TICARCILLIN/CLAVULANIC 97.9% 98.1% TIAMULIN 100% NA TILMICOSIN 96% 98.4% TOBRAMYCIN 99.6% 99.6% TYLOSIN 100% 100% 100% NA 99.7% 99.7% 93.0% 93.6% SULFAMETHOXAZOLE VANCOMYCIN 98.6% 99.3% CEFOXITIN SCREEN Staphylococcus aureus AUTOREAD Antimicrobial agent Total # R/S Overall % agreement Sensitivity Specificity Cefoxitin Screen 119/88 99.5% 100% 99.3% CEFOXITIN SCREEN Staphylococcus aureus MANUAL READ Antimicrobial agent Total # R/S Overall % agreement Sensitivity Specificity Cefoxitin Screen 119/88 99.0% 100% 99.6% TABLE 2 18 HOUR AUTOREADER AGREEMENT RATES FOR ENTEROCOCCAL SPECIES Data was collected on fresh clinical at two sites in the USA. Number tested % Minor Errors % Major Errors % Very Major Errors AMPICILLIN 187 98.2 99.5 0.1 0.3 0 AMPICILLIN/ 65 99.3 99.3 0.4 0.4 0 SULBACTAM CEPHALOTHIN 187 98.9 98.9 0.4 0.1 0.3 CHLORAMPHENICOL 187 99.9 99.9 0.1 0 0 CIPROFLOXACIN 122 98.4 98.4 1.6 0 0 CLINDAMYCIN 187 97.9 97.9 1.1 0 1.1 ERYTHROMYCIN 187 100 100 0 0 0 GENTAMCIN 187 98.9 98.9 1.1 0 0 IMIPENEM 122 99.2 99.2 0 0.8 0 OXACILLIN 187 98.4 98.9 0 1.1 0 PENICILLIN 187 98.9 100 0 0 0 RIFAMPIN 187 96.3 96.3 2.1 0.5 1.1 TETRACYCLINE 187 98.4 99.5 0.5 0 0 0 0 4.3* 187 97.9 97.9 SULPHAMETHOXAZOLE VANCOMYCIN 187 97.9 97.9 2.1 0 0 *Note, higher very major error rate attributed to difficulties in reading manual trailing end point. The ability of the Sensititre system to automatically read fresh veterinary Enterococcal isolates was checked on 176 fresh sequential isolates passing through a laboratory. All gave adequate signal generation.
TABLE 3: 18 HOUR AUTOREADER MIC AGREEMENT RATES FOR FASTIDIOUS GRAM NEGATIVE AND GRAM POSITIVE ORGANISMS H.somni A.pleuropneumoniae M. haemolytica Pasteurella spp B.bronchiseptica Y.enterocolitica Staphylococcus spp A AMPICILLIN 100% 100% 100% 100% 100% 100% 93% CEFOTETAN - - - 100% - - 100% CEFTIOFUR 100% 95% 97% 97% - - 100% CEPHALOTHIN 100% - 100% 100% - - 100% CHLORTETRACYCLINE 100% 100% 100% 100% - - - CLINDAMYCIN - - - - - - 100% DANOFLOXACIN - - 94% 100% - - - ENROFLOXACIN 100% 100% 100% 98% - - 100% ERYTHROMYCIN 100% 100% 100% 100% - - 100% FLORFENICOL 100% 100% 94% 100% - - - GENTAMICIN 100% 100% 100% 100% - - - MARBOFLOXACIN - - 94% 100% - - - NEOMYCIN - 100% - - - - - OXYTETRACYCLINE 100% 100% 100% 100% - - - PENICILLIN 100% 100% 100% 98% - - 100% SPECTINOMYCIN 100% 100% 100% 100% - - - SULPHACHLOROPYRIDAZINE 100% 100% 100% 100% - - - SULPHADIMETHOXINE 100% 100% 88% 97% - - - SULPHATHIAZOLE 100% 91% 94% 93% - - - TETRACYCLINE 100% 100% 100% 100% 100% 100% - TIAMULIN - 100% - - - - - TILMICOSIN 100% 100% 100% 100% - - - SULFAMETHOXAZOLE 100% 100% 94% 100% 94% 100% TULATHROMYCIN - - 100% 95.9% - - - TYLOSIN 100% 100% 100% 100% - - - No isolates tested 10 26 18 36 18 10 15 Note A Comprises S. intermedius and S.hyicus Note B 24 isolates tested REPRODUCIBILITY Reproducibility of automated reading was measured in 3 centres on 5 cultures against 11-12 antibiotics (14). Each assay was repeated 8 to 25 times. The percentage of readings that fell within +/- 1 doubling dilution of the medium MIC ranged from 93% to 100% depending on the strain. This was comparable to the reproducibility of reading panels manually. Reproducibility of MIC tests for each antibiotic has been measured on 4-5 organisms tested 12-25 times for all drugs. Reproducibility of manually and automatic reads was calculated as the percent of MIC s within plus or minus one dilution of the median value. Overall all results were >90% except Sulfisoxazole with Gram positive isolates. VET- PERFORMANCE TABLE V1.2