Dusp3 and Psme3 are associated with murine susceptibility to Staphylococcus aureus infection and human sepsis.

Using A/J mice, which are susceptible to Staphylococcus aureus, we sought to identify genetic determinants of susceptibility to S. aureus, and evaluate their function with regard to S. aureus infection. One QTL region on chromosome 11 containing 422 genes was found to be significantly associated with susceptibility to S. aureus infection. Of these 422 genes, whole genome transcription profiling identified five genes (Dcaf7, Dusp3, Fam134c, Psme3, and Slc4a1) that were significantly differentially expressed in a) S. aureus -infected susceptible (A/J) vs. resistant (C57BL/6J) mice and b) humans with S. aureus blood stream infection vs. healthy subjects. Three of these genes (Dcaf7, Dusp3, and Psme3) were down-regulated in susceptible vs. resistant mice at both pre- and post-infection time points by qPCR. siRNA-mediated knockdown of Dusp3 and Psme3 induced significant increases of cytokine production in S. aureus-challenged RAW264.7 macrophages and bone marrow derived macrophages (BMDMs) through enhancing NF-κB signaling activity. Similar increases in cytokine production and NF-κB activity were also seen in BMDMs from CSS11 (C57BL/6J background with chromosome 11 from A/J), but not C57BL/6J. These findings suggest that Dusp3 and Psme3 contribute to S. aureus infection susceptibility in A/J mice and play a role in human S. aureus infection

The Antimicrobial Scrub Contamination and Transmission (ASCOT) Trial: A Three-Arm, Blinded, Randomized Controlled Trial With Crossover Design to Determine the Efficacy of Antimicrobial-Impregnated Scrubs in Preventing Healthcare Provider Contamination

OBJECTIVE To determine whether antimicrobial-impregnated textiles decrease the acquisition of pathogens by healthcare provider (HCP) clothing. DESIGN We completed a 3-arm randomized controlled trial to test the efficacy of 2 types of antimicrobial-impregnated clothing compared to standard HCP clothing. Cultures were obtained from each nurse participant, the healthcare environment, and patients during each shift. The primary outcome was the change in total contamination on nurse scrubs, measured as the sum of colony-forming units (CFU) of bacteria. PARTICIPANTS AND SETTING Nurses working in medical and surgical ICUs in a 936-bed tertiary-care hospital. INTERVENTION Nurse subjects wore standard cotton-polyester surgical scrubs (control), scrubs that contained a complex element compound with a silver-alloy embedded in its fibers (Scrub 1), or scrubs impregnated with an organosilane-based quaternary ammonium and a hydrophobic fluoroacrylate copolymer emulsion (Scrub 2). Nurse participants were blinded to scrub type and randomly participated in all 3 arms during 3 consecutive 12-hour shifts in the intensive care unit. RESULTS In total, 40 nurses were enrolled and completed 3 shifts. Analyses of 2,919 cultures from the environment and 2,185 from HCP clothing showed that scrub type was not associated with a change in HCP clothing contamination ( P =.70). Mean difference estimates were 0.118 for the Scrub 1 arm (95% confidence interval [CI], −0.206 to 0.441; P =.48) and 0.009 for the Scrub 2 rm (95% CI, −0.323 to 0.342; P =.96) compared to the control. HCP became newly contaminated with important pathogens during 19 of the 120 shifts (16%). CONCLUSIONS Antimicrobial-impregnated scrubs were not effective at reducing HCP contamination. However, the environment is an important source of HCP clothing contamination. TRIAL REGISTRATION Clinicaltrials.gov Identifier: NCT 02645214 Infect Control Hosp Epidemiol 2017;38:1147–115

Panton-Valentine Leukocidin Is Not the Primary Determinant of Outcome for Staphylococcus aureus Skin Infections: Evaluation from the CANVAS Studies

The impact of Panton-Valentine leukocidin (PVL) on the severity of complicated skin and skin structure infections (cSSSI) caused by Staphylococcus aureus is controversial. We evaluated potential associations between clinical outcome and PVL presence in both methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) isolates from patients enrolled in two large, multinational phase three clinical trials assessing ceftaroline fosamil for the treatment of cSSSI (the CANVAS 1 and 2 programs). Isolates from all microbiologically evaluable patients with monomicrobial MRSA or MSSA infections (n = 473) were genotyped by PCR for pvl and underwent pulsed-field gel electrophoresis (PFGE). Genes encoding pvl were present in 266/473 (56.2%) isolates. Infections caused by pvl-positive S. aureus were associated with younger patient age, North American acquisition, and presence of major abscesses (P<0.001 for each). Cure rates of patients infected with pvl-positive and pvl-negative S. aureus were similar overall (93.6% versus 92.8%; P = 0.72), and within MRSA-infected (94.5% vs. 93.1%; P = 0.67) and MSSA-infected patients (92.2% vs. 92.7%; P = 1.00). This finding persisted after adjustment for multiple patient characteristics. Outcomes were also similar when USA300 PVL+ and non-USA300 PVL+ infections were compared. The results of this contemporary, international study suggest that pvl presence was not the primary determinant of outcome in patients with cSSSI due to either MRSA or MSSA

Two Genes on A/J Chromosome 18 Are Associated with Susceptibility to Staphylococcus aureus Infection by Combined Microarray and QTL Analyses

Although it has recently been shown that A/J mice are highly susceptible to Staphylococcus aureus sepsis as compared to C57BL/6J, the specific genes responsible for this differential phenotype are unknown. Using chromosome substitution strains (CSS), we found that loci on chromosomes 8, 11, and 18 influence susceptibility to S. aureus sepsis in A/J mice. We then used two candidate gene selection strategies to identify genes on these three chromosomes associated with S. aureus susceptibility, and targeted genes identified by both gene selection strategies. First, we used whole genome transcription profiling to identify 191 (56 on chr. 8, 100 on chr. 11, and 35 on chr. 18) genes on our three chromosomes of interest that are differentially expressed between S. aureus-infected A/J and C57BL/6J. Second, we identified two significant quantitative trait loci (QTL) for survival post-infection on chr. 18 using N2 backcross mice (F1 [C18A]×C57BL/6J). Ten genes on chr. 18 (March3, Cep120, Chmp1b, Dcp2, Dtwd2, Isoc1, Lman1, Spire1, Tnfaip8, and Seh1l) mapped to the two significant QTL regions and were also identified by the expression array selection strategy. Using real-time PCR, 6 of these 10 genes (Chmp1b, Dtwd2, Isoc1, Lman1, Tnfaip8, and Seh1l) showed significantly different expression levels between S. aureus-infected A/J and C57BL/6J. For two (Tnfaip8 and Seh1l) of these 6 genes, siRNA-mediated knockdown of gene expression in S. aureus–challenged RAW264.7 macrophages induced significant changes in the cytokine response (IL-1 β and GM-CSF) compared to negative controls. These cytokine response changes were consistent with those seen in S. aureus-challenged peritoneal macrophages from CSS 18 mice (which contain A/J chromosome 18 but are otherwise C57BL/6J), but not C57BL/6J mice. These findings suggest that two genes, Tnfaip8 and Seh1l, may contribute to susceptibility to S. aureus in A/J mice, and represent promising candidates for human genetic susceptibility studies

Host gene expression profiling and in vivo cytokine studies to characterize the role of linezolid and vancomycin in methicillin-resistant Staphylococcus aureus (MRSA) murine sepsis model.

Linezolid (L), a potent antibiotic for Methicillin Resistant Staphylococcus aureus (MRSA), inhibits bacterial protein synthesis. By contrast, vancomycin (V) is a cell wall active agent. Here, we used a murine sepsis model to test the hypothesis that L treatment is associated with differences in bacterial and host characteristics as compared to V. Mice were injected with S. aureus USA300, and then intravenously treated with 25 mg/kg of either L or V at 2 hours post infection (hpi). In vivo alpha-hemolysin production was reduced in both L and V-treated mice compared to untreated mice but the reduction did not reach the statistical significance [P = 0.12 for L; P = 0.70 for V). PVL was significantly reduced in L-treated mice compared to untreated mice (P = 0.02). However the reduction of in vivo PVL did not reach the statistical significance in V- treated mice compared to untreated mice (P = 0.27). Both antibiotics significantly reduced IL-1β production [P = 0.001 for L; P = 0.006 for V]. IL-6 was significantly reduced with L but not V antibiotic treatment [P<0.001 for L; P = 0.11 for V]. Neither treatment significantly reduced production of TNF-α. Whole-blood gene expression profiling showed no significant effect of L and V on uninfected mice. In S. aureus-infected mice, L altered the expression of a greater number of genes than V (95 vs. 42; P = 0.001). Pathway analysis for the differentially expressed genes identified toll-like receptor signaling pathway to be common to each S. aureus-infected comparison. Expression of immunomodulatory genes like Cxcl9, Cxcl10, Il1r2, Cd14 and Nfkbia was different among the treatment groups. Glycerolipid metabolism pathway was uniquely associated with L treatment in S. aureus infection. This study demonstrates that, as compared to V, treatment with L is associated with reduced levels of toxin production, differences in host inflammatory response, and distinct host gene expression characteristics in MRSA sepsis

Evidence for genetic variation and <i>Staphylococcus aureus</i> infection.

<p>Evidence for genetic variation and <i>Staphylococcus aureus</i> infection.</p

The Staphylococcus aureus LytSR Two-Component Regulatory System Affects Biofilm Formation▿ †

Studies of the Staphylococcus aureus LytSR two-component regulatory system have led to the identification of the cid and lrg operons, which affect murein hydrolase activity, stationary-phase survival, antibiotic tolerance, and biofilm formation. The cid gene products enhance murein hydrolase activity and antibiotic tolerance whereas the lrg gene products inhibit these processes in a manner believed to be analogous to bacteriophage-encoded holins and antiholins, respectively. Importantly, these operons have been shown to play significant roles in biofilm development by controlling the release of genomic DNA, which then becomes an important structural component of the biofilm matrix. To determine the role of LytSR in biofilm development, a lytS knockout mutant was generated from a clinical S. aureus isolate (UAMS-1) and the effects on gene expression and biofilm formation were examined. As observed in laboratory isolates, LytSR was found to be required for lrgAB expression. Furthermore, the lytS mutant formed a more adherent biofilm than the wild-type and complemented strains. Consistent with previous findings, the increased adherence of the mutant was attributed to the increased prevalence of matrix-associated eDNA. Transcription profiling studies indicated that the lrgAB operon is the primary target of LytSR-mediated regulation but that this regulatory system also impacts expression of a wide variety of genes involved in basic metabolism. Overall, the results of these studies demonstrate that the LytSR two-component regulatory system plays an important role in S. aureus biofilm development, likely as a result of its direct influence on lrgAB expression

Effect of antibiotics on bacterial load in A/J mice.

<p>The bacterial loads in the (A) Kidney and (B) Blood from A/J mice after intraperitoneal infection with <i>S. aureus</i> (6×10⁶ CFU/g, strain USA300), and treatment with linezolid (L) or vancomycin (V) (25 mg/kg). Infected mice were sacrificed as follows: 2 hpi <i>S. aureus</i>; 24 hpi <i>S. aureus</i>; 24 hpi <i>S. aureus</i> with linezolid or vancomycin. Each symbol represents one mouse. <i>P-</i>values were obtained by F-test. The error bars correspond to the standard error of mean (SEM) and the dashed line correspond to the mean value. Values of <i>P</i><0.05 were considered significant.</p