Bacterial resistances against antibiotics are increasingly problematic for medical treatment of pathogenic bacteria, e.g., in hospitals. Resistances are, among other genes, often encoded on plasmids which can be transmitted between bacteria not only within one species, but also between different species, genera, and families. The plasmid pDrive is transformed into bacteria of the model strain Escherichia coli DH5α. Within this investigation, we applied micro-Raman spectroscopy with two different excitation wavelengths in combination with support vector machine (SVM) and linear discriminant analysis (LDA) to differentiate between bacterial cultures according to their cultural plasmid content. Recognition rates of about 92% and 90% are achieved by Raman excitation at 532 and 244 nm, respectively. The SVM loadings reveal that the pDrive transformed bacterial cultures exhibit a higher DNA content compared to the untransformed cultures. To elucidate the influence of the antibiotic, ampicillin-treated cultures are also comprised within this study and are classified with rates of about 97% and 100% for 532 and 244 nm Raman excitation, respectively. The Raman spectra recorded with 532 nm excitation wavelength show differences of the secondary protein structure and enhanced stress-related respiration rates for the ampicillin-treated cultures. Independent cultural replicates of either ampicillin-challenged or non-challenged cultures are successfully identified with identification rates of over 90%.

Classification of Raman spectra recorded from single cells is commonly applied to bacteria that exhibit small sizes of approximately 1 to 2 μm. Here, we study the possibility to adopt this classification approach to filamentous bacteria of the genus Streptomyces. The hyphae can reach extensive lengths of up to 35 μm, which can correspond to a single cell identified in light microscopy. The classification of Raman bulk spectra will be demonstrated. Here, ultraviolet resonance Raman (UV RR) spectroscopy is chosen to classify six Streptomyces species by the application of a tree-like classifier. For each knot of the hierarchical classifier, estimated classification accuracies of over 94% are accomplished. In contrast to the classification of bulk spectra, the classification of single-cell spectra requires a homogenous substance distribution within the cell. Consequently, the bacterial cell chemistry can be represented by one individual spectrum. This requirement is not fulfilled when different spectra are processed from different locations within the cell. Bacteria of the investigated genus Streptomyces exhibit, besides the normal bacterial spectra, lipid-rich spectra. The occurrence of lipid enrichment depends on culture age and nutrition availability. With this study, we investigate the cell substance distribution, especially of lipid-rich fractions. The classification utilizing a tree-like classifier is also applied to the Streptomyces single-cell spectra, resulting in classification accuracies between 80 and 93% for the investigated Streptomyces species.

Heavy metal contamination of soil has an immense impact on the surrounding environment, such as the ground water, and hence, has become an important issue within bioremediation. Therefore, heavy metal contamination has to be determined preferably cost‐efficiently, rapidly, and reliably. Here, soil bacteria of the genus Streptomyces are used as bioindicators for heavy metal contamination investigated via micro‐Raman spectroscopy. A single cell approach is studied to avoid time‐consuming culturing and plate counting. Bacteria of Streptomyces galilaeus were incubated in Ni2+ enriched media and single cell spectra were recorded. Supervised statistics linear discriminant analysis was used to evaluate the influence of the culture age and the anion on bacterial cells, which has been determined to be minor compared with the spectral impact of Ni2+. The identification of the Raman spectra according to different Ni2+ concentration ranges is accomplished with a prediction accuracy of about 88%. Therefore, we conclude that Streptomyces can be used as a bioindicator to predict Ni2+ concentrations in the micromolar range. Copyright © 2011 John Wiley & Sons, Ltd.

The prevalence of multidrug resistant, extended spectrum β-lactamase (ESBL)-producing Enterobacteriaceae is increasing worldwide. The present study aimed to provide an overview of the multidrug resistance phenotype and genotype of ESBL-producing Escherichia coli (E. coli) isolates of livestock and wild bird origin in Greece. Nineteen phenotypically confirmed ESBL-producing E. coli strains isolated from fecal samples of cattle (n = 7), pigs (n = 11) and a Eurasian magpie that presented resistance to at least one class of non β-lactam antibiotics, were selected and genotypically characterized. A DNA-microarray based assay was used, which allows the detection of various genes associated with antimicrobial resistance. All isolates harbored blaCTX-M-1/15, while blaTEM was co-detected in 13 of them. The AmpC gene blaMIR was additionally detected in one strain. Resistance genes were also reported for aminoglycosides in all 19 isolates, for quinolones in 6, for sulfonamides in 17, for trimethoprim in 14, and for macrolides in 8. The intI1 and/or tnpISEcp1 genes, associated with mobile genetic elements, were identified in all but two isolates. This report describes the first detection of multidrug resistance genes among ESBL-producing E. coli strains retrieved from feces of cattle, pigs, and a wild bird in Greece, underlining their dissemination in diverse ecosystems and emphasizing the need for a One-Health approach when addressing the issue of antimicrobial resistance.