Shawar R M, Moore D G, LaRocco M T
Department of Pathology and Laboratory Medicine, University of Texas Medical School, Houston 77030.
J Clin Microbiol. 1990 Mar;28(3):508-12. doi: 10.1128/jcm.28.3.508-512.1990.
Isolation of Nocardia spp. from clinical specimens can be enhanced by the use of paraffin baiting, which relies on the selective ability of the organism to metabolize paraffin. We evaluated 44 Nocardia isolates, 18 group IV mycobacterial isolates, and 4 Streptomyces isolates for growth on blood agar (BA) and on carbon-free agar containing single or double substrates as follows: paraffin agar (PA), gelatin agar (GA), urea agar (UA), PA-gelatin (PG), and PA-urea (PU). The growth rates of Nocardia spp. on BA, PA, PU, and PG were similar; but 3-day-old colonies were larger on BA for 20 (45%) isolates. After longer incubations (7 to 14 days), some Nocardia colonies were larger on PA, PG and PU than they were on BA. Despite variable morphologies on BA, colonies on PA, PG, and PU were consistently smooth, creamy, and raised. Compared with growth on BA, the growth of mycobacteria was much slower on PA, PG, and PU, with poor growth on UA and GA. The growth of Streptomyces spp. was greatly enhanced on GA, PG, UA, and PU and was poorest on PA. Twelve sputum specimens seeded with Nocardia asteroides (10(4) CFU/ml) were inoculated onto BA and all chemically defined media. Nocardiae were recovered from 6 to 12 specimens grown on BA, GA, and UA; 11 of 12 specimens grown on PG; and 12 of 12 specimens grown on PA and PU. Only PA was able to suppress the growth of other microorganisms that were present in sputum specimens. These results suggest that chemically defined media containing PA may be useful for the selective isolation of Nocardia spp. from contaminated clinical specimens.
使用石蜡诱饵法可提高从临床标本中分离诺卡氏菌属的效率，该方法依赖于该菌代谢石蜡的选择能力。我们评估了44株诺卡氏菌分离株、18株IV组分枝杆菌分离株和4株链霉菌分离株在血琼脂（BA）以及含单一或双底物的无碳琼脂上的生长情况，这些底物如下：石蜡琼脂（PA）、明胶琼脂（GA）、尿素琼脂（UA）、PA-明胶（PG）和PA-尿素（PU）。诺卡氏菌属在BA、PA、PU和PG上的生长速率相似；但对于20株（45%）分离株，3日龄菌落在BA上更大。经过更长时间培养（7至14天）后，一些诺卡氏菌落在PA、PG和PU上比在BA上更大。尽管在BA上形态各异，但在PA、PG和PU上的菌落始终光滑、呈奶油色且凸起。与在BA上生长相比，分枝杆菌在PA、PG和PU上的生长要慢得多，在UA和GA上生长较差。链霉菌属在GA、PG、UA和PU上生长显著增强，在PA上生长最差。将接种了星形诺卡氏菌（10(4) CFU/ml）的12份痰标本接种到BA和所有化学成分明确的培养基上。从在BA、GA和UA上生长的6至12份标本中回收了诺卡氏菌；在PG上生长的12份标本中有11份；在PA和PU上生长的12份标本中均有12份。只有PA能够抑制痰标本中存在 的其他微生物的生长。这些结果表明，含PA的化学成分明确的培养基可能有助于从受污染的临床标本中选择性分离诺卡氏菌属。
