Rapid identification of non-sporing anaerobes using nuclear magnetic resonance spectroscopy and an identification strategy

An Escherichia coli strain, PGB01, isolated from feral pigeon Faeces, thermally fit to survive in pigeon, shows high level resistance to trimethoprim

In this study, of the hundred Escherichia coli strains isolated from feral Pigeon faeces, eighty five strains were resistant to one or more antibiotics and fifteen sensitive to all the antibiotics tested. The only strain (among all antibiotic-resistant E. coli isolates) that possessed class 1 integron was PGB01. The dihydrofolate reductase gene of the said integron was cloned, sequenced and expressed in E. coli JM109. Since PGB01 was native to pigeon's gut, we have compared the growth of PGB01 at two different temperatures, 42°C (normal body temperature of pigeon) and 37°C (optimal growth temperature of E. coli; also the human body temperature), with E. coli K12. It was found that PGB01 grew better than the laboratory strain E. coli K12 at 37°C as well as at 42°C. In the thermal fitness assay, it was observed that the cells of PGB01 were better adapted to 42°C, resembling the average body temperature of pigeon. The strain PGB01 also sustained more microwave mediated thermal stress than E. coli K12 cells. The NMR spectra of the whole cells of PGB01 varied from E. coli K12 in several spectral peaks relating some metabolic adaptation to thermotolerance. On elevating the growth temperature from 37°C to 42°C, susceptibility to kanamycin (both strains were sensitive to it) of E. coli K12 was increased, but in case of PGB01 no change in susceptibility took place. We have also attempted to reveal the basis of trimethoprim resistance phenotype conferred by the dfrA7 gene homologue of PGB01. Molecular Dynamics (MD) simulation study of docked complexes, PGB01-DfrA7 and E. coli TMP-sensitive-Dfr with trimethoprim (TMP) showed loss of some of the hydrogen and hydrophobic interaction between TMP and mutated residues in PGB01-DfrA7-TMP complex compared to TMP-sensitive-Dfr-TMP complex. This loss of interaction entails decrease in affinity of TMP for PGB01-DfrA7 compared to TMP-sensitive-Dfr.

Staphylococcus epidermidis in the human skin microbiome mediates fermentation to inhibit the growth of Propionibacterium acnes: implications of probiotics in acne vulgaris

Increasing evidence demonstrates that commensal microorganisms in the human skin microbiome help fight pathogens and maintain homeostasis of the microbiome. However, it is unclear how these microorganisms maintain biological balance when one of them overgrows. The overgrowth of Propionibacterium acnes (P. acnes), a commensal skin bacterium, has been associated with the progression of acne vulgaris. Our results demonstrate that skin microorganisms can mediate fermentation of glycerol, which is naturally produced in skin, to enhance their inhibitory effects on P. acnes growth. The skin microorganisms, most of which have been identified as Staphylococcus epidermidis (S. epidermidis), in the microbiome of human fingerprints can ferment glycerol and create inhibition zones to repel a colony of overgrown P. acnes. Succinic acid, one of four short-chain fatty acids (SCFAs) detected in fermented media by nuclear magnetic resonance (NMR) analysis, effectively inhibits the growth of P. acnes in vitro and in vivo. Both intralesional injection and topical application of succinic acid to P. acnes-induced lesions markedly suppress the P. acnes-induced inflammation in mice. We demonstrate for the first time that bacterial members in the skin microbiome can undergo fermentation to rein in the overgrowth of P. acnes. The concept of bacterial interference between P. acnes and S. epidermidis via fermentation can be applied to develop probiotics against acne vulgaris and other skin diseases. In addition, it will open up an entirely new area of study for the biological function of the skin microbiome in promoting human health.

Microbiological spectrum of brain abscess at a tertiary care hospital in South India: 24-year data and review

Intracranial abscesses are life-threatening infections that pose a diagnostic challenge not only to the neurosurgeon but also to the microbiologists. Detailed studies documenting the spectrum of infecting agents involved in brain abscesses are limited from India. Materials and Methods. This is a retrospective analysis of 352 samples from 1987 to 2010 analyzed at a tertiary care hospital in South India from 1987 to 2010, to document the changing trends with time. Results. The age of the patients ranged from 2 to 80 years, a larger number of males being affected. Otogenic infections were the most common cause while cryptogenic abscesses were 20%. Gram stain and culture positivity were 78% each. Gram-positive and negative facultative aerobes and obligate anaerobes were also on the rise. Unusual organisms, like Burkholderia pseudomallei, Salmonella typhi, Nocardia species, Cladosporium bantiana, Fonsecaea pedrosoi, Entamoeba histolytica, and Acanthamoeba were also isolated and/or detected from the brain abscesses aspirate or resected tissue. Summary. New and emerging pathogens associated with brain abscess, especially in immunosuppressed individuals, have renewed the necessity of an early detection, and it will be of great value in appropriate management of patients with brain abscess.

New insights into Prevotella diversity and medical microbiology

In light of recent studies based on cultivation-independent methods, it appears that the diversity of Prevotella in human microbiota is greater than was previously assumed from cultivation-based studies, and that the implication of these bacteria in several human diseases was unrecognized. While some Prevotella taxa were found during opportunistic infections, changes in Prevotella abundance and diversity were discovered during dysbiosis-associated diseases. As member of the microbiota, Prevotella may also be considered as a reservoir for resistance genes. Greater knowledge on Prevotella diversity, as well as new insights into its pathogenic potential and implication in dysbiosis are expected from the use of human microbe identification microarrays, from whole-genome sequence analyse, and from the NIH Human Microbiome Project data. New approaches, including molecular-based methods, could contribute to improve the diagnosis of Prevotella infections.