ABSTRACT
Several Bursaphelenchus spp. have been detected in declining pine trees in Europe during intensive monitoring for the pine wood nematode B. xylophilus. We investigated the pathogenicity of B. vallesianus and B. mucronatus, isolated from declining Scots pine (Pinus sylvestris) forests in Valais (Switzerland), in relation to drought stress. Four isolates of B. vallesianus and two isolates of B. mucronatus were inoculated into 3-year-old P. sylvestris trees, which were subjected to different watering treatments (50, 100, 150, and 250 ml of water per pot, biweekly). Disease symptoms, plant mortality, nematode population density, and nematode distribution in dead plants were assessed. Both Bursaphelenchus spp. proved highly pathogenic to the seedlings and watering treatment affected disease development in the inoculated pine trees. With decreasing water supply, we observed faster disease progress and higher pine mortality for both Bursaphelenchus spp. The overall mortality 70 days after inoculation was 60, 92, 95, and 100% for B. vallesianus and 40, 95, 100, and 100% for B. mucronatus in the 250-, 150-, 100-, and 50-ml watering treatments, respectively. Both nematode species multiplied in the inoculated plants; however, B. mucronatus had higher population densities than B. vallesianus in all watering treatments (on average, 33,159 versus 14,702 nematodes/dead plant compared with the initial inoculum density of 6,000 nematodes/plant). The highest nematode density was found in the lower part of the stem. About 7 to 16% of the nematodes were extracted from the roots. This study demonstrated that B. vallesianus has a pathogenicity potential comparable with that of B. mucronatus and provided experimental evidence that drought stress can result in increased symptoms caused by either Bursaphelenchus sp.
ABSTRACT
Frozen microtitration trays manufactured by Micro-Media Systems (MMS) for antimicrobial testing of anaerobic bacteria were evaluated and compared with the broth disk elution method of Virginia Polytechnic Institute (VPI) described by Wilkins and Thiel. A total of 224 clinical anaerobic isolates were tested. Susceptibility results were compared for carbenicillin, cefoxitin, chloramphenicol, clindamycin, penicillin, and tetracycline. Published procedures for the MMS and VPI methods were followed using aerobic inoculation. Growth performance in the MMS method was 74% compared with 89% in the VPI method. For each antibiotic, the MMS minimum inhibitory concentration was compared with the VPI test concentration. Of the 972 drug-organism combinations, 2.9% of the results were discrepant. Clindamycin and tetracycline accounted for 82% of the discrepancies. The MMS anaerobe susceptibility panels were easy to inoculate and interpret and compared well with the VPI broth disk susceptibility method.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacteria/drug effects , Microbial Sensitivity Tests , AnaerobiosisABSTRACT
The direct inoculation of the Minitek anaerobe identification system (BBL Microbiology Systems, Cockeysville, Md.) from positive blood cultures was compared with subculture and Minitek results obtained using the manufacturer's recommended procedures. A total of 40 clinical anaerobic blood cultures were processed for rapid identification utilizing bacterial pellets obtained by centrifugation. Of these cultures, 30 yielded pure isolates of anaerobic rods that were used for comparison. In 87% of the pure cultures, identification from the direct inoculum method was identical to the routine procedure using Minitek biochemicals. When the additional test for lecithinase and lipase production was included, the identification agreement was 97%. Direct identification of anaerobic rods from blood cultures utilizing the Minitek system is reliable, easy to perform, and can provide a complete identification in 24 h from the time a blood culture showed growth.
