The performances of three blood culture systems, Hémoline performance diphasic medium (bioMérieux, Marcy l'Etoile, France), Bactec Plus Aerobic/F* (Becton Dickinson, Paramus, N.J.), and Vital Aer (bi-oMérieux), were compared for the diagnosis of 17 cases of brucellosis. By using a 5-day incubation protocol, positive results were 52.9, 82.4, and 11.8%, respectively. When the protocol was extended to 7 days, the results were 76.5, 94.1, and 47.1%, respectively. Bactec was the fastest system (P < 0.05).

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A comparative study was carried out to evaluate the performances of different culture media for the recovery of Salmonella spp. from 1,000 routine samples of human stools. By direct plating we tested Salmonella-Shigella agar (SS), Hektoen enteric agar (HE), bismuth sulfite agar (BS), novobiocin-brilliant green-glycerol-lactose agar (NBGL) and SM-ID medium (SM), and after selenite enrichment, we tested all of the media except HE. C 8-esterase and oxidase tests were used for the screening of Salmonella spp. on SS and HE. The total number of Salmonella isolates from direct culture was 74, with respective sensitivities and positive predictive values (PPVs) of 78.4 and 61%, 64.9 and 18.7%, 36.5 and 34.2%, 55.4 and 20.7%, and 39.2 and 43.9% for NBGL, SS, HE, BS, and SMID, respectively. After enrichment, the total number of Salmonella isolates was 88. The respective sensitivities and PPVs obtained were 90.9 and 62.5%, 92 and 17%, 90.9 and 32% and 93.2 and 71.3% for NBGL, SS, BS, and SM, respectively. According to our results, NBGL in direct plating was the medium with the highest sensitivity with respect to the sensitivities of the other media, with significant statistical differences (P < 0.05). Likewise, the PPV for NBGL was also the highest (61%). After enrichment in selenite broth, the sensitivities of the four media tested were similar, with the best PPV obtained with SM (71.3%); this was followed by NBGL (62.5%). When C 8-esterase was used on SS or HE, the PPVs improved from less than 40% to about 100%.

The relative performance of five plating media [Rambach agar; salmonella-shigella (SS) agar, novobiocin-brilliant green-glycerol-lactose (NBGL), modified semisolid Rappaport-Vassiliadis medium (MSRV), and Salmonella Detection and Identification-2 (SM2)] and selenite broth (SB) subcultured in SS agar in the recovery of Salmonella spp. from 500 human stool specimens was evaluated. On Rambach agar and SS agar, the C8-esterase test was also used for selection of suspicious colonies. Eighty-one samples were positive for salmonellae on at least one of the six media. Sensitivities and specificities of MSRV, SB, NBGL, SS, Rambach agar, and SM2 were 95.1 and 98.1%, 87.6 and 99.8%, 79 and 91.9%, 69.1 and 99.3%, 56.8 and 96.9%, and 54.3 and 92.4%, respectively. There were statistically significant differences between MSRV and NBGL, Rambach agar, SS agar, and SM2 (p < 0.005), between SB and SS agar, Rambach agar, and SM2 (p < 0.05), and between NBGL and SM2 and Rambach agar (p < 0.005). The greatest number of isolates was recovered with MSRV, whose performance surpassed that of enrichment in selenite broth, probably because the subcultures were not repeated on MSRV. This hypothesis is now under investigation. The specificity of each of the five solid media was greater than 90%.

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