Kinetics of <i>Candida albicans</i>and <i>Staphylococcus aureus</i>Biofilm Initiation on Herpes Simplex Virus (HSV-1 and HSV-2) Infected Cells

This study examines the kinetics of S. aureus and C. albicans adherence as it relates to HSV replication and corresponding dynamic display of shared receptors. HeLa cells infected for various times with HSV-1 gL86 or HSV-2 333gJ-(MOI 50) were incubated with S. aureus ATCC 25923 or C. albicans yeast and CFU measured. Over time, S. aureus adherence to HSV-1 infected cells was relatively stable for 45 min then decreased to 0.8 of virus-free control, before cycling at 15-to-30 min intervals. In contrast, staphylococcal adherence to HSV-2 infected cells proceeded at a more gradual rate, increasing to control levels at ~105 min before decreasing to a nadir at 165 min. Yeast adherence to HSV-1 infected cells remained relatively unchanged for the first 75 min then increased 2-fold before returning to its original level. This pattern is repeated over the next 90 min. While a similar pattern with C. albicans and HSV-2 was measured, it occurred more rapidly. Our model shows that while the interaction of both HSV-1 and HSV-2 with S. aureus is both dynamic and inhibitory, C. albicans interaction with HSV-2 is more permissive than HSV-1. However, the interaction of both microbes with HSV-infected cells in this model system appears to be independent of α5B1, CD36 and HSP60 viral-regulated receptor expression. These findings indicate that microbiome interactions across taxonomic kingdoms are more complex than previously thought.

Menaquinone (Vitamin K2) Enhancement of <i>Staphylococcus aureus</i>Biofilm Formation

During infection, Staphylococcus aureus is exposed to exogenous menaquinone which is essential for the human blood clotting cascade. The effect of exogenous menaquinone on S. aureus phenotypic expression is not known. To test whether menaquinone affects expression of virulence-associated phenotypes, methicillin-sensitive (MSSA) and -resistant (MRSA) S. aureus strains (n = 8) were grown in the presence of menaquinone (0.001 - 12 μg/ml). Capsule production, biofilm formation (plastic and fibronectin-coated microtiter plates) and carotenoid levels were determined spectrophotometrically after growth in Mueller Hinton broth (MH;24-hr, 37°C). All experiments were, at minimum, done in triplicate and repeated twice. Menaquinone at physiologic levels (0.01 μg/ml MH) significantly increased (p 0.05) biofilm formation on plastic in a manner that was bacterial population size dependent. In addition, menaquinone (0.05 - 4 μg/ml) significantly increased (p 0.05) biofilm formation on fibronectin-coated surfaces for four MSSA strains and one MRSA strain by two to six-fold as compared to medium controls. However, menaquinone had no effect on capsule production or cell-associated carotenoid levels. Menaquinone’s effect on biofilm formation on fibronectin-coated surfaces appears to be regulated by sarA. These findings are the first to demonstrate that a vitamin at concentrations reported in humans affects S. aureus virulence-associated phenotypes.

Antimicrobial Susceptibility and Sub-MIC Biofilm Formation of <i>Moraxella catarrhalis</i>Clinical Isolates under Anaerobic Conditions

A medium was developed to support the anaerobic growth and antimicrobial susceptibility testing of clinical Moraxella catarrhalis isolates. The MICs of clinical Moraxella catarrhalis isolates under anaerobic conditions were, in general, decreased as compared to atmospheric or capnophilic conditions, while the MBCs for all conditions were within a 2 fold concentration dilution. Biofilm formation was affected by the presence of sub-MIC concentrations of azithromycin and the tested quinolones with the exception of levofloxacin.

Semi-Automated Method for Multi-Tasking Measurement of Microbial Growth, Capsule, and Biofilm Formation

The majority of bacterial infections involve the formation of biofilms. Biofilm formation is nutrient and growth dependent. Determination of the effects of nutrients on exopolysaccharide production and bacterial growth is labor and time intensive. We tested whether the Bioscreen C (Growth Curves, Inc.) would have utility as a high-throughput tool in the measurement of fundamental phenotype expression, as it relates to growth conditions. Within 48 - 72 hr, reproduceble, statistically significant data on the affects of growth conditions on generation time, capsule production and biofilm formation (maximally for 25 different conditions per 24 hr run cycle;n = 4) were obtained. Although all S. aureus strains produced similar amounts of capsule, sarA– and agr– strains grew significantly slower than parent strain (1.6 fold slower) and produced significantly (p 0.05) less biofilm (~2 fold). E. coli growth rate, biofilm and capsule production in simulated nephropathic urine medium was similar for urine with insulin (20 μU). Addition of insulin to urine medium with proline increased generation time, capsule and biofilm production. Findings from this study show that the Bioscreen C is a rapid, reproducible, and easily manipulated system to concurrently measure bacterial growth, biofilm formation, and capsule production. In addition, there is the potential for further applications of this system by expanding the types of detector dyes used.

Effect of Human Insulin on the Formation of Catheter-Associated <i>E. coli</i>Biofilms

Biofilm formation is essential for the survival and growth of Escherichia coli?in catheter-associated infections. Individuals with type 2 diabetes mellitus can excrete insulin and/or glucose in their urine. This population also has an increased incidence of urinary tract infections. The focus of this study was to determine if the composition of Foley catheter material affects biofilm formation by E. coli in a model system for type 2 diabetes mellitus. Rubber (lubricious-coated), silicon-coated, silver-coated and nitrofurazone-coated catheter segments (5 mm;n = 6) were tested. Catheter segments were added to E. coli ATCC25922 (104 CFU/ml, final concentration) in artificial urine alone, or with insulin (40 μU/ml) and/or glucose (0.1%). After incubation (18 h, 37?C, in air and anaerobically) the level of catheter-associated biofilm was determined by crystal violet staining (Abs550nm). Statistical analysis was done by ANOVA with post-hoc analysis (Tukey). Neither nitrofurazone-coated nor silver-coated catheters supported the formation of E. coli biofilm, regardless of growth condition tested. In contrast, under aerobic biofilm formation on silicon catheters was significantly higher (p E. coli controls. Biofilm formation was also significantly increased