In recent years, matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) has become the standard for routine bacterial species identification due to its rapidity and low costs for consumables compared to those of traditional DNA-based methods. However, it has been observed that strains of some bacterial species, such as Acinetobacter baumannii strains, cannot be reliably identified using mass spectrometry (MS). Raman spectroscopy is a rapid technique, as fast as MALDI-TOF, and has been shown to accurately identify bacterial strains and species. In this study, we compared hierarchical clustering results for MS, genomic, and antimicrobial susceptibility test data to hierarchical clustering results from Raman spectroscopic data for 31 A. baumannii clinical isolates labeled according to their pulsed-field gel electrophoresis data for strain differentiation. In addition to performing hierarchical cluster analysis (HCA), multiple chemometric methods of analysis, including principal-component analysis (PCA) and partial least-squares discriminant analysis (PLSDA), were performed on the MS and Raman spectral data, along with a variety of spectral preprocessing techniques for best discriminative results. Finally, simple HCA algorithms were performed on all of the data sets to explore the relationships between, and natural groupings of, the strains and to compare results for the four data sets. To obtain numerical comparison values of the clustering results, the external cluster evaluation criteria of the Rand index of the HCA dendrograms were calculated. With a Rand index value of 0.88, Raman spectroscopy outperformed the other techniques, including MS (with a Rand index value of 0.58).
The specific pathogenicity of Enterococcus relative to other pathogens in polymicrobial wounds is unknown. Identifying strain-specific outcomes and investigating the interactions of Enterococcus strains with other wound pathogens could provide additional tools and strategies for infection mitigation in combat-related wounds.
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Maggot debridement therapy (MDT), despite its long history and safety profile, finds limited use in the military health care system. Although new methods are continually being investigated to debride wounds more quickly and effectively, MDT remains largely a therapy of last resort. We evaluated the frequency of MDT in the Army sector of the MHS and the decision-making process surrounding its use. A 22 question survey of Army physicians was prepared and distributed through select Medical Corps Consultants in specialties likely to practice debridement. 83% of respondents were familiar with MDT, and of those familiar, 63% were aware of FDA approval for the product and 10% had used the product themselves. The three most frequently cited reasons for not using the therapy were no need (52%), no access (23%), and insufficient experience (19%). Informing the 37% of physicians who are not aware of FDA approval is an obvious target for program improvement. However, as many do not find a need for MDT, targeted improvements to MDT access and education for those physicians who encounter indications for MDT would permit them to apply MDT where there is an unmet need.
Acinetobacter baumannii is a nosocomial species frequently isolated from the traumatic wounds of injured military personnel and increasingly detected in civilian healthcare facilities. Many clinical isolates of A. baumannii are drug resistant, so new treatments are needed for infections. Recently, the ability of strains of conspecific bacteria to inhibit the growth of other strains has been observed in increasing numbers of species. We previously reported on intraspecific semisolid-phase growth inhibition (antagonism) among 94 clinical isolates of A. baumannii. These antagonistic interactions may be the result of genetically-encoded molecules, so more closely related isolates would be expected to produce similar patterns of interactions caused by identically active gene products. However, the phylogeny of clinical A. baumannii below the species level has not been established for this set of isolates.In this study, we used Phylomark to identify three genetic loci that recapitulated a whole-genome phylogeny of published A. baumannii genomes and we created a parsimony-based phylogeny from the 1.2 kilobase concatenated sequences. One clade appeared to exhibit the highest incidence of antagonistic interactions against all other isolates screened, except for itself and one relatively distant clade. This clade's nearest neighbor was susceptible to the most consistent antagonistic activity by the first clade; both of these clades appear to belong to MLST ST1 with reference strain AYE. Other isolates with high rates of antagonistic activity fall outside of ST1. Future studies aim to elucidate the genetic basis of the antagonism phenotype in clinical Acinetobacter, particularly in the most antagonistic isolates. The next step will be to mine these interactions to identify expressed antimicrobial molecules with potential for drug therapy.
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