Enterococcus faecium, a commensal of the human intestine, has emerged as a hospital-adapted, multi-drug resistant (MDR) pathogen. Bacteriophages (phages), natural predators of bacteria, have regained attention as therapeutics to stem the rise of MDR bacteria. Despite their potential to curtail MDR E. faecium infections, the molecular events governing E. faecium-phage interactions remain largely unknown. Such interactions are important to delineate because phage selective pressure imposed on E. faecium will undoubtedly result in phage resistance phenotypes that could threaten the efficacy of phage therapy. In an effort to understand the emergence of phage resistance in E. faecium, three newly isolated lytic phages were used to demonstrate that E. faecium phage resistance is conferred through an array of cell wall-associated molecules, including secreted antigen A (SagA), enterococcal polysaccharide antigen (Epa), wall teichoic acids, capsule, and an arginine-aspartate-aspartate (RDD) protein of unknown function. We find that capsule and Epa are important for robust phage adsorption and that phage resistance mutations in sagA, epaR, and epaX enhance E. faecium susceptibility to ceftriaxone, an antibiotic normally ineffective due to its low affinity for enterococcal penicillin binding proteins. Consistent with these findings, we provide evidence that phages potently synergize with cell wall (ceftriaxone and ampicillin) and membrane-acting (daptomycin) antimicrobials to slow or completely inhibit the growth of E. faecium. Our work demonstrates that the evolution of phage resistance comes with fitness defects resulting in drug sensitization and that lytic phages could serve as effective antimicrobials for the treatment of E. faecium infections.

Pathogen evolution and subsequent phenotypic heterogeneity during chronic infection are proposed to enhance Staphylococcus aureus survival during human infection. We tested this theory by genetically and phenotypically characterizing strains with mutations constructed in the mismatch repair (MMR) and oxidized guanine (GO) system, termed mutators, which exhibit increased spontaneous-mutation frequencies. Analysis of these mutators revealed not only strain-dependent increases in the spontaneous-mutation frequency but also shifts in mutational type and hot spots consistent with loss of GO or MMR functions. Although the GO and MMR systems are relied upon in some bacterial species to prevent reactive oxygen species-induced DNA damage, no deficit in hydrogen peroxide sensitivity was found when either of these DNA repair pathways was lost in S. aureus. To gain insight into the contribution of increased mutation supply to S. aureus pathoadaptation, we measured the rate of ␣-hemolysin and staphyloxanthin inactivation during serial passage. Detection of increased rates of ␣-hemolysin and staphyloxanthin inactivation in GO and MMR mutants suggests that these strains are capable of modifying virulence phenotypes implicated in mediating infection. Accelerated derivation of altered virulence phenotypes, combined with the absence of increased ROS sensitivity, highlights the potential of mutators to drive pathoadaptation in the host and serve as catalysts for persistent infections.

Concerns regarding increased prevalence of daptomycin (DAP)-resistant strains necessitate novel therapies for Enterococcus faecium infections. Obligately lytic bacteriophages are viruses that target, infect, and kill bacterial cells. Limited studies have evaluated phage-antibiotic combinations against E. faecium. Following an initial screen of eight E. faecium strains, three strains with varying DAP/phage susceptibility were selected for further experiments. Phage-to-strain specificity contributed to synergy with antibiotics by time-kill analyses and was associated with lower development of phage resistance.

Staphylococcus aureus CC30 is distinguished by its ability initiate complicated infections. This ability is due to acquisition of unique genes, SNPs and metabolic changes that attenuate virulence until the conditions become favorable for bacteremia and subsequent hematogenous seeding.

Cryptococcal meningitis (CM) is an opportunistic fungal infection associated with human immunodeficiency virus (HIV) and other forms of immunosuppression. We lack a clear understanding of CM associated mortality among HIV-negative, non-transplant patients in the United States (US). This article compares clinical features and outcomes across HIV status in patients with laboratory-confirmed CM. Methods: A retrospective cohort study was performed that included adult patients with laboratory-confirmed CM treated at an academic tertiary hospital between January 2000 and September 2018. Those with a history of organ transplant or non-meningeal infections were excluded. Data were gathered on demographics, HIV status, clinical presentation, cerebrospinal fluid (CSF) profiles, neurological outcomes, hospital course, and mortality. Results: A total of 70 patients with cryptococcal disease were identified. Our final sample included 36 CM patients, mean age was 48.8 ± 13.2 years; of this group, 66.7% ( n = 24) had HIV. Median [interquartile range (IQR)] absolute CD4 count for the HIV group was 35 cells/μl (10–80 cells/μl). Non-HIV/non-transplant patients were significantly older ( p < 0.001) and had higher rates of altered mental status (AMS) on presentation (58.3% versus 25%, p = 0.05). Non-HIV patients/non-transplant patients had significantly higher CSF white blood cell (WBC) count ( p = 0.02), lower CSF glucose ( p = 0.005), and higher CSF protein ( p < 0.001) compared with HIV patients. There was no significant variation in temperature, blood pressure, WBC count, serum sodium, CSF opening pressure, length of stay, intensive care unit admission, or neurological outcomes. Overall, 90-day all-cause mortality was 19.4%: mortality rates were significantly higher in non-HIV/non-transplant patients at both 90 days (41.7% versus 8.3%, p = 0.017) and 1 year (41.7% versus 12.5%, p = 0.047). Conclusion: Compared with HIV-infected individuals, non-HIV/non-transplant CM patients have a higher CSF WBC count at the time of diagnosis, higher rates of AMS on presentation, and higher rates of 90-day and 1-year all-cause mortality. Further prospective research is needed to identify the hallmarks of CM in non-HIV/non-transplant patients to facilitate early identification and intervention.