Pseudomonas aeruginosa

Meticulous drug management programs can have a positive effect on drug-resistant infections, finds a new report published in the Journal of Clinical Microbiology. A team of clinical scientists led by Larissa Matukas studied the effect of antibiotic stewardship surrounding the use of ciprofloxacin to treat bacterial infections caused by Escherichia coli or Pseudomonas aeruginosa. Using a stewardship program that involved reporting ciprofloxacin susceptibility only if no other susceptibilities were found when testing isolates against a multidrug panel, the team observed a strong reduction in the use of this particular antibiotic, which correlated with a trend toward increasing susceptibility in E. coli isolates. The study demonstrates that, while small, antibiotic stewardship programs may help prolong the efficacy of antibiotic arsenals.

“Although several factors could theoretically contribute to a microorganism's ability to colonize the intestinal ecosystem, effective completion for nutrients is paramount to success.” So the editors reference researcher Rolf Freter in their introduction to this new, integrative text. This volume highlights this truth with a biochemical focus on bacterial pathogens and the human host. This includes chapters on enteric, respiratory, urinary tract, and intracellular pathogens. Some chapters also focus attention on the role of commensal communities, such as in dental plaque or in the gut through interaction with host immunity. More species-specific topics include central carbon metabolism by Borrelia burgdorferi, regulation of Escherichia coli fimbriae by host sialic acid, and Pseudomonas aeruginosa metabolism during infection of cystic fibrosis patients. Though it is sparse in its figures, this is a timely and information-rich collection that should be a welcome resource for many microbiologists.

Scientists at the Institut Pasteur in Paris, France, were surprised to discover that an airborne volatile compound released by the bacterium Pseudomonas aeruginosa can promote growth of the fungus Aspergillus fumagatus. First author Benoit Briard, working with senior scientist Jean-Paul Latgé, made the discovery. “That microbes ‘smell’ other microbes is not new,” says Latgé. “But that one species of bacteria is stimulating the growth of a fungus by ‘smell’—this is totally new.” The compound, identified as dimethyl sulfoxide by mass spectroscopy, contains sulfur, which the fungus can use to grow. The findings will be useful when studying coinfections of the lung, where both P. aeruginosa and A. fumagatus can cause disease.

In the summer of 2013, a patient arrived in our emergency department with complaints of high fever and abdominal pain. She came to us straight from the airport following her return from a 3-month visit to India. Identified as septic, she was “pan-cultured,” meaning readily obtained fluids and substances were sent immediately to begin cultures. Due to concerns for bacterial gastroenteritis, she received ceftriaxone in the emergency department and ciprofloxacin after admission. Fevers continued and blood cultures yielded Escherichia coli, which was phenotypically resistant to most antibiotics, including ceftriaxone and ciprofloxacin, but susceptible to “last-resort” carbapenems, which were then used to treat her.

Pseudomonas aeruginosa motility is inversely related to its ability to form biofilms. New research from Boston Children's Hospital shows that this relationship is at least partially reciprocally regulated. Scientists working with Simon Dove identified an operon encoding a σ factor and its anti-σ factor, which they named sbrI and sbrR, respectively. They found that the ΔsbrR mutant strain exhibited extremely reduced swarming motility but formed more robust biofilms than the wild type. This was pinpointed to hyperactivity of the SbrI σ factor in the ΔsbrR strain, which increased muiA transcription 100-fold. Overexpression of muiA in a wild-type strain was sufficient to suppress swarming, demonstrating the mechanistic importance of this transcript. While the exact function of MuiA remains to be uncovered, its regulation by SbrI and SbrR are clear. This may help scientists manipulate biofilm formation, a common state of many P. aeruginosa infections.

When encapsulated in silica nanoparticles, peppermint oil and cinnamaldehyde, which gives cinnamon its characteristic flavor, penetrate biofilms and potently kill drug-resistant pathogens within them, according to Vincent Rotello at the University of Massachusetts, Amherst, and his collaborators. These nanocapsules also promote fibroblast growth, which helps wounds to heal, they say, leading them to call these flavor-loaded nanoparticles a “promising natural disinfectant and wound cleanser.” Details appeared 17 June 2015 in ACS Nano (doi:10.1021/acsnano.5b01696).

Spices such as ginger and cinnamon as well as other natural products have potent antimicrobial activities against methicillin-resistant Staphylococcus aureus (MRSA), various strains of Pseudomonas aeruginosa, and other pathogens, including those that form biofilms, according to several researchers who presented findings during the 2015 ASM General Meeting, held in New Orleans, La., last May. If they prove safe and effective, these natural products or derivatives based on them could lead to new treatment strategies for infections caused by these clinically challenging bacterial strains, the researchers say.

The purpose of this essay is threefold: to give an outline of the life and the various achievements of Theodor Escherich, to provide a background to his discovery of what he called Bacterium coli commune (now Escherichia coli), and to indicate the enormous impact of studies with this organism, long before it became the cornerstone of research in bacteriology and in molecular biology.

As biological sequence data are generated at an ever increasing rate, the role of bioinformatics in biological research also grows. Students must be trained to complete and interpret bioinformatic searches to enable them to effectively utilize the trove of sequence data available. A key bioinformatic tool for sequence comparison and genome database searching is BLAST (Basic Local Alignment Search Tool). BLAST identifies sequences in a database that are similar to the entered query sequence, and ranks them based on the length and quality of the alignment. Our goal was to introduce sophomore and junior level undergraduate students to the basic functions and uses of BLAST with a small group activity lasting a single class period. The activity provides students an opportunity to perform a BLAST search, interpret the data output, and use the data to make inferences about bacterial cell envelope structure. The activity consists of two parts. Part 1 is a handout to be completed prior to class, complete with video tutorial, that reviews cell envelope structure, introduces key terms, and allows students to familiarize themselves with the mechanics of a BLAST search. Part 2 consists of a hands-on, web-based small group activity to be completed during the class period. Evaluation of the activity through student performance assessments suggests that students who complete the activity can better interpret the BLAST output parameters % query coverage and % max identity. While the topic of the activity is bacterial cell wall structure, it could be adapted to address other biological concepts.

This chapter explores the data collected on the importance of bacteriophages to the ecology of the earth's polar regions. It examines the numbers of phage-like particles that have been observed in the ecosystems and their importance in regulating bacterial numbers and the food chain of the extreme oligotrophic environments. To understand the potential impact of bacteriophages on polar ecosystems, it is first necessary to understand the different life choices of phages and how environmental factors are known to affect them. Perhaps not surprisingly, these data suggest that bacteriophages are an important shunt in carbon cycling in the Antarctic regions as well as in the Arctic. Unlike many other studies, the authors conclude that neither bacteriovores nor bacteriophages are important regulators of bacterial numbers but that numbers are regulated by algae blooms and other factors that affect bacterial growth. Pseudolysogeny was first defined by Baess in 1971. In his review, pseudolysogeny was identified as a phage-host interaction in which the phage, following infection of the host, elicits an unstable, nonproductive response. Thus any study that enumerates total virus-like particles (VLPs) must be tempered with the understanding that not all will be infective. The data obtained in this study support the hypothesis that bacteriophages are of quantifiable significance in the carbon-flow cycle of Antarctic oligotrophic lakes. Few researchers have investigated bacteriophages in both the Arctic and Antarctic in the same study. Phylogenetic analysis of their data revealed five previously uncharacterized subgroups of T4-like bacteriophages in many environments, including the Arctic samples.