To make or take: bacterial lipid homeostasis during Infection

Bacterial fatty acids are critical components of the cellular membrane. A shift in environmental conditions or in the bacterium’s lifestyle may result in the requirement for a distinct pool of fatty acids with unique biophysical properties. This can be achieved by the modification of existing fatty acids or via de novo synthesis. Furthermore, bacteria have evolved efficient means to acquire these energy-rich molecules from their environment. However, the balance between de novo fatty acid synthesis and exogenous acquisition during pathogenesis is poorly understood. Here, we studied the mouse fatty acid landscape prior to and after infection with Acinetobacter baumannii, a Gram-negative, opportunistic human pathogen. The lipid fluxes observed following infection revealed fatty acid- and niche-specific changes. Lipidomic profiling of A. baumannii isolated from the pleural cavity of mice identified novel A. baumannii membrane phospholipid species and an overall increased abundance of unsaturated fatty acid species. Importantly, we found that A. baumannii relies largely upon fatty acid acquisition in all but one of the studied niches, the blood, where the pathogen biosynthesizes its own fatty acids. This work is the first to reveal the significance of balancing the making and taking of fatty acids in a Gram-negative bacterium during infection, which provides new insights into the validity of targeting fatty acid synthesis as a treatment strategy.Felise G. Adams, Claudia Trappetti, Jack K. Waters, Maoge Zang, Erin B. Brazel, James C. Paton, Marten F. Snel, Bart A. Eijkelkam

Uncovering the link between the SpnIII restriction modification system and LuxS in Streptococcus pneumoniae meningitis isolates

Streptococcus pneumoniae is capable of randomly switching their genomic DNA methylation pattern between six distinct bacterial subpopulations (A-F) via recombination of a type 1 restriction-modification locus, spnIII. These pneumococcal subpopulations exhibit phenotypic changes which favor carriage or invasive disease. In particular, the spnIIIB allele has been associated with increased nasopharyngeal carriage and the downregulation of the luxS gene. The LuxS/AI-2 QS system represent a universal language for bacteria and has been linked to virulence and biofilm formation in S. pneumoniae. In this work, we have explored the link between spnIII alleles, the luxS gene and virulence in two clinical pneumococcal isolates from the blood and cerebrospinal fluid (CSF) of one pediatric meningitis patient. The blood and CSF strains showed different virulence profiles in mice. Analysis of the spnIII system of these strains recovered from the murine nasopharynx showed that the system switched to different alleles commensurate with the initial source of the isolate. Of note, the blood strain showed high expression of spnIIIB allele, previously linked with less LuxS protein production. Importantly, strains with deleted luxS displayed different phenotypic profiles compared to the wildtype, but similar to the strains recovered from the nasopharynx of infected mice. This study used clinically relevant S. pneumoniae strains to demonstrate that the regulatory network between luxS and the type 1 restriction-modification system play a key role in infections and may support different adaptation to specific host niches.Hannah N. Agnew, John M. Atack, Ann R.D. Fernando, Sophie N. Waters, Mark van der Linden, Erin Smith, Andrew D. Abell, Erin B. Brazel, James C. Paton, and Claudia Trappett

Parental knowledge, beliefs and behaviours for oral health of toddlers residing in rural Victoria

Background: Little is known about the oral health of children under the age of four years. The determinants of early childhood caries (ECC) in this young age group are also not well understood despite a growing recognition that early interventions may deliver the greatest benefits. The aim of this study was to examine the oral health‐related knowledge, attitudes and reported behaviours of parents of children aged 12–24 months living in rural areas of Victoria, Australia. Methods: A robust theoretical model was utilized to identify oral health‐related behaviours and their antecedent and reinforcing conditions within the context of this specific population group. Two hundred and ninety‐four parent/child dyads were recruited through their maternal and child health nurses as part of a larger intervention trial. Parents completed a self‐report questionnaire. Results: Knowledge regarding risk and protective factors amongst parents was variable and sometimes at odds with contemporary evidence. Knowledge of the role of early infection with S. mutans was very low, with high levels of behaviours that may promote early transmission reported. Tooth cleaning was reported by most parents at least sometimes, however a large proportion lacked confidence and this was significantly related to the frequency of the cleaning. Parents were confused about the fluoride status of their water supplies. Most parents believed fluoride toothpaste reduced the risk of ECC but did not know whether it should be used with toddlers. Conclusions: The results of this study have implications for efforts to prevent dental decay in this very young age group. Health care professionals other than dentists need support to provide information and promote confidence with regard to optimal fluoride exposure. Attention should also be given to the contribution of early contact with particular bacteria in oral health education and promotion programmes

Comparing production-biomass ratios of benthos and suprabenthos in macrofaunal marine crustaceans

Using available data from the literature, we compared the productionbiomass ratios (P/B) between the suprabenthic (= hyperbenthic) and the benthic (infaunaepifauna) species within the group of the macrofaunal marine crustaceans. This data set consists of 91 P/B estimates (26 for suprabenthos and 65 for infaunaepifauna) for 49 different species. Suprabenthic crustacean P/B was significantly higher than P/B of benthic crustacean (post-hoc Scheffé test; one-way analysis of covariance, ANCOVA; p < 103) and also of other (noncrustacean) benthic invertebrate (p < 104). Predictive multilinear regression (MLR) analysis for macrofaunal marine crustaceans showed P/B to depend significantly on mean annual temperature (T) and mean individual weight (W) (R2 = 0.367). Adding the variable swimming capacity increased goodness-of-fit to R2 = 0.528. The higher P/B of suprabenthic (= swimming) macrofauna in comparison with that of the benthic compartment seems to be related to the most apparent feature of the suprabenthos, its swimming capacity. The high P/Bs reported for suprabenthic species indicate how a nontrivial part of benthic production can be ignored if suprabenthos is not well sampled, therefore biasing the models of energy flow generated for trophic webs

The membrane composition defines the spatial organization and function of a major Acinetobacter baumannii drug efflux system

Acinetobacter baumannii is one of the world’s most problematic nosocomial pathogens. The combination of its intrinsic resistance and ability to acquire resistance markers allow this organism to adjust to antibiotic treatment. Despite being the primary barrier against antibiotic stress, our understanding of the A. baumannii membrane composition and its impact on resistance remains limited. In this study, we explored how the incorporation of host-derived polyunsaturated fatty acids (PUFAs) is associated with increased antibiotic susceptibility. Functional analyses of primary A. baumannii efflux systems indicated that AdeB-mediated antibiotic resistance was impacted by PUFA treatment. Molecular dynamics simulations of AdeB identified a specific morphological disruption of AdeB when positioned in the PUFA-enriched membrane. Collectively, we have shown that PUFAs can impact antibiotic efficacy via a vital relationship with antibiotic efflux pumps. Furthermore, this work has revealed that A. baumannii’s unconditional desire for fatty acids may present a possible weakness in its multidrug resistance capacity. Importance: Antimicrobial resistance is an emerging global health crisis. Consequently, we have a critical need to prolong our current arsenal of antibiotics, in addition to the development of novel treatment options. Due to their relatively high abundance at the host-pathogen interface, PUFAs and other fatty acid species not commonly synthesized by A. baumannii may be actively acquired by A. baumannii during infection and change the biophysical properties of the membrane beyond that studied in standard laboratory culturing media. Our work illustrates how the membrane phospholipid composition impacts membrane protein function, which includes an important multidrug efflux system in extensively-drug-resistant A. baumannii. This work emphasizes the need to consider including host-derived fatty acids in in vitro analyses of A. baumannii. On a broader scope, this study presents new findings on the potential health benefits of PUFA in individuals at risk of contracting A. baumannii infections or those undergoing antibiotic treatment.Maoge Zang, Hugo MacDermott-Opeskin, Felise G. Adams, Varsha Naidu, Jack K. Waters, Ashley B. Carey, Alex Ashenden, Kimberley T. McLean, Erin B. Brazel, Jhih-Hang Jiang, Alessandra Panizza, Claudia Trappetti, James C. Paton, Anton Y. Peleg, Ingo Köper, Ian T. Paulsen, Karl A. Hassan, Megan L. O’Mara, Bart A. Eijkelkam