Previous studies of the antibiotic susceptibility of Streptococcus milleri group organisms have distinguished among species by using phenotypic techniques. Using 44 isolates that were speciated by 16S rRNA gene sequencing, we studied the MICs and minimum bactericidal concentrations of penicillin, ampicillin, ceftriaxone, and clindamycin for Streptococcus intermedius, Streptococcus constellatus, and Streptococcus anginosus. None of the organisms was resistant to beta-lactam antibiotics, although a few isolates were intermediately resistant; one strain of S. anginosus was tolerant to ampicillin, and another was tolerant to ceftriaxone. Six isolates were resistant to clindamycin, with representation from each of the three species. Relatively small differences in antibiotic susceptibilities among species of the S. milleri group show that speciation is unlikely to be important in selecting an antibiotic to treat infection caused by one of these isolates.Three species compose the Streptococcus milleri group: Streptococcus intermedius, Streptococcus constellatus, and Streptococcus anginosus (5,12,13). Investigators who have used phenotypically differentiated strains within the S. milleri group have suggested that these three species have similar antibiotic susceptibilities (1,4,7,8). Phenotypic identification to the species level, however, has been shown to be difficult and at times unreliable (3,6,9). In order to compare the antibiotic susceptibilities of species within the S. milleri group, we determined the MICs and minimum bactericidal concentrations (MBCs) of four clinically relevant antibiotics for 44 genotypically characterized strains of the S. milleri group. MATERIALS AND METHODSBacteria. Forty-four clinically significant isolates of the S. milleri group that had been isolated from different patients between 1985 and 2000 were studied. All had been implicated as the causative organisms in infection (2). Their sources of isolation are summarized in Table 1. These strains were assigned to the S. milleri group based on the results of API 20 Strep system (bioMérieux Vitek, Hazelton, Mo.) tests and were further speciated by PCR amplification and sequence analysis of a segment of the 16S rRNA gene (3). They were stored at Ϫ70°C after having been passaged no more than two or three times. In addition to two well-characterized strains of Streptococcus pneumoniae that have been studied repeatedly in our laboratory, the following American Type Culture Collection (ATCC) strains were included as reference strains: ATCC 27335 (S. intermedius), ATCC 9895 and ATCC 33397 (S. anginosus), and ATCC 29213 (Staphylococcus aureus).MIC and MBC testing. Todd-Hewitt broth (Difco, Detroit, Mich.) containing 0.5% yeast extract (Difco) (THY), a broth medium previously shown by our laboratory to be optimal for testing the MICs of S. pneumoniae (10), was used in this study. Preliminary studies showed that this medium supported the growth of S. milleri group isolates more reliably than Mueller-Hinton or tryptic soy broth. Penicillin G (Sigma...

This paper summarizes the theory used in a system that identifies foreign body impact on a composite plate using built-in strain sensors. The identification system consists of a model of the composite plate and an identification algorithm. The algorithm compares the measured response of the plate to the model response and estimates the impact location and force time history. The solution, which uses a smoother/filter optimization, includes a new computational algorithm that saves considerable computation time for systems with many degrees of freedom.

This paper presents a computer code, IDIMPACT, based on a proposed impact load identification method for identifying both the amount of the impact load and its location in composite plates from distributed built-in piezoelectric sensor measurements.The proposed method consists of a system model characterizing the dynamic response of composite plates and of a response comparator estimating the impact location and force history by comparing the sensor measurements with the simulated ones.To verify the computer code and the proposed method, instrumented hammer impact tests were conducted on a 36-inch-by-30-inch composite plate with distributed surface-mounted piezoceramic sensors. The computer code was implemented in a PC with data acquisition boards to digitize the sensor measurements. The code would automatically run and graphically display the predicted location and impact force-time history from a monitor. The code has reliably with high accuracy predicted the force and location of every impact event that was tested.

This paper summarizes the implementation of an impact identification system on a composite plate. The impact, normal to the surface of the plate, generates a traveling wave that is measured by surface mounted sensors. The identification system compares the measured response of the plate to the model response and estimates the impact location and force time history. The accuracy and reliability of the system was tested using many impacts distributed across the plate and the robustness of the system was tested by adding simulated noise to the data. The system was tested on the composite plate with free boundaries and clamped boundaries. The system proved to be accurate with an average location error ranging from .39 inches for the free boundary case to .49 inches for the clamped plate with noise. The area monitored by the 13 sensor array was 20 inches by 20 inches.

No abstract