Surface disinfection challenges for Candida auris: an in-vitro study

The emerging pathogenic multidrug-resistant yeast Candida auris is an important source of healthcare-associated infections and of growing global clinical concern. The ability of this organism to survive on surfaces and withstand environmental stressors creates a challenge for eradicating it from hospitals. A panel of C. auris clinical isolates was evaluated on different surface environments against the standard disinfectant sodium hypochlorite and high-level disinfectant peracetic acid. C. auris was shown to selectively tolerate clinically relevant concentrations of sodium hypochlorite and peracetic acid in a surface-dependent manner, which may explain its ability to successfully persist within the hospital environment

Drivers of Clostridioides difficile hypervirulent ribotype 027 spore germination, vegetative cell growth and toxin production in vitro

Objectives: Clostridioides difficile infection (CDI) is a considerable healthcare and economic burden worldwide. Faecal microbial transplant remains the most effective treatment for CDI, but is not at the present time the recommended standard of care. We hereby investigate which factors derived from a healthy gut microbiome might constitute the colonisation resistance barrier (CRB) in the gut, inhibiting CDI. Method: CRB drivers pH, short chain fatty acid (SCFA), and oxidation-reduction potential (ORP) were investigated in vitro using C. difficile NAP1/BI/027. Readouts for inhibitory mechanisms included germination, growth, toxin production and virulence gene expression. pH ranges (3 – 7.6), SCFA concentrations (25 – 200mM) and ORP (-300 - +200mV) were manipulated in brain heart infusion broth cultures under anaerobic conditions to assess the inhibitory action of these mechanisms. Results: <pH 5.3 completely inhibited C. difficile growth to OD of 0.019 vs. 1.19 for control pH 7.5. Toxin production was reduced to 25 units vs 3125 units for pH 7.6 (1 in 5 dilutions). Virulence gene expression reduced by 150 fold compared with pH 7.6 (p<0.05). Germination and proliferation of spores below pH 6.13 yielded an average OD of 0.006 vs. 0.99 for control. SCFA were potent regulators of toxin production at 25mM and above (p<0.05). Acetate significantly inhibited toxin production to 25 units independent of OD (0.8733) vs. control (OD 0.6 and toxin titer 3125) (p<0.05). ORP did not impact C. difficile growth. Conclusion: This study highlights the critical role that pH has in the CRB, regulating CDI in vitro and that SCFA can regulate C. difficile function independent of pH

Estimation of genetic variation in residual variance in female and male broiler chickens

In breeding programs, robustness of animals and uniformity of end product can be improved by exploiting genetic variation in residual variance. Residual variance can be defined as environmental variance after accounting for all identifiable effects. The aims of this study were to estimate genetic variance in residual variance of body weight, and to estimate genetic correlations between body weight itself and its residual variance and between female and male residual variance for broilers. The data sets comprised 26 972 female and 24 407 male body weight records. Variance components were estimated with ASREML. Estimates of the heritability of residual variance were in the range 0.029 (s.e.50.003) to 0.047 (s.e.50.004). The genetic coefficients of variation were high, between 0.35 and 0.57. Heritabilities were higher in females than in males. Accounting for heterogeneous residual variance increased the heritabilities for body weight as well. Genetic correlations between body weight and its residual variance were 20.41 (s.e.50.032) and 20.45 (s.e.50.040), respectively, in females and males. The genetic correlation between female and male residual variance was 0.11 (s.e.50.089), indicating that female and male residual variance are different traits. Results indicate good opportunities to simultaneously increase the mean and improve uniformity of body weight of broilers by selection

Venetoclax causes metabolic reprogramming independent of BCL-2 inhibition

BH3-mimetics are a new class of anti-cancer drugs that inhibit anti-apoptotic Bcl-2 proteins. In doing so, BH3-mimetics sensitise to cell death. Venetoclax is a potent, BCL-2 selective BH3-mimetic that is clinically approved for use in chronic lymphocytic leukaemia. Venetoclax has also been shown to inhibit mitochondrial metabolism, this is consistent with a proposed role for BCL-2 in metabolic regulation. We used venetoclax to understand BCL-2 metabolic function. Similar to others, we found that venetoclax inhibited mitochondrial respiration. In addition, we also found that venetoclax impairs TCA cycle activity leading to activation of reductive carboxylation. Importantly, the metabolic effects of venetoclax were independent of cell death because they were also observed in apoptosis-resistant BAX/BAK-deficient cells. However, unlike venetoclax treatment, inhibiting BCL-2 expression had no effect on mitochondrial respiration. Unexpectedly, we found that venetoclax also inhibited mitochondrial respiration and the TCA cycle in BCL-2 deficient cells and in cells lacking all anti-apoptotic BCL-2 family members. Investigating the basis of this off-target effect, we found that venetoclax-induced metabolic reprogramming was dependent upon the integrated stress response and ATF4 transcription factor. These data demonstrate that venetoclax affects cellular metabolism independent of BCL-2 inhibition. This off-target metabolic effect has potential to modulate venetoclax cytotoxicity

'Secondary biofilms' could cause failure of peracetic acid high-level disinfection of endoscopes

The reduced susceptibility of biofilm to disinfectants presents a challenge to the successful reprocessing of medical equipment. This study examined the effect of residual biomass remaining after previous PAA disinfection on tolerance of subsequent mature P. aeruginosa biofilms to PAA. The effect of enzymatic degradation of specific components of P. aeruginosa biofilm EPS on the effectiveness of PAA disinfection was also evaluated. The presence of residual biomass from previously disinfected biofilms significantly enhanced the tolerance of a subsequent biofilms. A 96hr old “secondary biofilm” formed on disinfected biomass survived PAA concentrations of 4000 ppm, which exceeds the concentrations used in practice for high-level disinfection. These observations indicate that, under certain circumstances recolonisation of residual EPS can cause failure of disinfection of medical equipment such as endoscopes and emphasises the importance of cleaning of endoscopes prior to disinfection