The Compatibility of Chlorhexidine and a Skin Care Product Line: A Real-World Analysis of Hospital-Acquired Infection Rates.

Chlorhexidine gluconate (CHG) use helps reduce hospital-acquired infections (HAIs). Chlorhexidine gluconate effectiveness can be reduced by use of skin care products. Although laboratory work can be performed to prove compatibility, such work has limitations. The purpose of this study was to compare HAI rates when CHG antiseptic wipes were used in conjunction with a silicone- and micronutrient-based skin care product line (SMSP) and when CHG wipes were used without the SMSP. Using commercial distribution data, 17 hospitals that purchased both CHG wipes and SMSP were identified. Hospital-acquired infection rates from this group were compared with HAI rates from 18 hospitals that used CHG wipes, but not SMSP. Hospital-acquired infection information was obtained from the Leapfrog Group (www.hospitalsafetyscore.org/). Four infection rates were compared: (1) infection in the blood during an intensive care unit stay, (2) infection in the urinary tract during an intensive care unit stay, (3) surgical site infection after colon surgery, and (4) average infection rate from 1 to 3. There was no significant difference between the infection rates of the two groups (Ps ranged from .285 to .983). There was also no statistically significant association between hospital grade and product use (P = .194). When considering publicly available data on HAI, there was no measurable difference in HAI rates between facilities that use CHG wipes with or without an SMSP. The SMSP does not impact the efficacy of CHG wipes.

Antimicrobial dressing efficacy against mature Pseudomonas aeruginosa biofilm on porcine skin explants.

An ex vivo porcine skin explant biofilm model that preserves key properties of biofilm attached to skin at different levels of maturity (0-3 days) was used to assess the efficacy of commercially available antimicrobial dressings and topical treatments. Assays were also performed on the subpopulation of antibiotic tolerant biofilm generated by 24 hours of pre-treatment with gentamicin (120× minimal inhibitory concentration) prior to agent exposure. Five types of antimicrobial agents (iodine, silver, polyhexamethylene biguanide, honey and ethanol) and four types of moisture dressings (cotton gauze, sodium carboxymethylcellulose fibre, calcium alginate fibre and cadexomer beads) were assessed. Time-release silver gel and cadexomer iodine dressings were the most effective in reducing mature biofilm [between 5 and 7 logarithmic (log) of 7-log total], whereas all other dressing formulations reduced biofilm between 0·3 and 2 log in 24 or 72 hours with a single exposure. Similar results were found after 24-hour exposure to silver release dressings using an in vivo pig burn wound model, demonstrating correlation between the ex vivo and in vivo models. Results of this study indicate that commonly used microbicidal wound dressings vary widely in their ability to kill mature biofilm and the efficacy is influenced by time of exposure, number of applications, moisture level and agent formulation (sustained release).

Development of a novel ex vivo porcine skin explant model for the assessment of mature bacterial biofilms.

Bacterial biofilms have been proposed to be a major factor contributing to the failure of chronic wounds to heal because of their increased tolerance to antimicrobial agents and the prolonged inflammation they cause. Phenotypic characteristics of bacterial biofilms vary depending on the substratum to which they attach, the nutritional environment, and the microorganisms within the biofilm community. To develop an ex vivo biofilm model that more closely mimics biofilms in chronic skin wounds, we developed an optimal procedure to grow mature biofilms on a central partial-thickness wound in 12-mm porcine skin explants. Chlorine gas produced optimal sterilization of explants while preserving histological properties of the epidermis and dermis. Pseudomonas aeruginosa and Staphylococcus aureus developed mature biofilms after 3 days that had dramatically increased tolerance to gentamicin and oxacillin (∼100× and 8,000× minimal inhibitory concentration, respectively) and to sodium hypochlorite (0.6% active chlorine). Scanning electron microscopy and confocal microscopy verified extensive exopolymeric biofilm structures on the explants. Despite a significant delay, a ΔlasI quorum-sensing mutant of P. aeruginosa developed biofilm as antibiotic-tolerant as wild-type after 3 days. This ex vivo model simulates growth of biofilms on skin wounds and provides an accurate model to assess effects of antimicrobial agents on mature biofilms.

The effect of negative pressure wound therapy with periodic instillation using antimicrobial solutions on Pseudomonas aeruginosa biofilm on porcine skin explants.

Negative pressure wound therapy with instillation (NPWTi) is increasingly used as an adjunct therapy for a wide variety of infected wounds. However, the effect of NPWTi on mature biofilm in wounds has not been determined. This study assessed the effects of NPWTi using saline or various antimicrobial solutions on mature Pseudomonas aeruginosa biofilm using an ex vivo porcine skin explant biofilm model. Treatment consisted of six cycles with 10-minute exposure to instillation solution followed by 4 hours of negative pressure at -125 mm Hg over a 24-hour period. NPWTi using saline reduced bacterial levels by 1-log (logarithmic) of 7-log total colony-forming units (CFUs). In contrast, instillation of 1% povidone iodine (2-log), L-solution (3-log), 0·05% chlorhexidine gluconate (3-log), 0·1% polyhexamethylene biguanide (4-log), 0·2% polydiallyldimethylammonium chloride (4-log) and 10% povidone iodine (5-log), all significantly reduced (P < 0·001) total CFUs. Scanning electron micrographs showed disrupted exopolymeric matrix of biofilms and damaged bacterial cells that correlated with CFU levels. Compared with previous studies assessing microbicidal effects of topical antimicrobial dressings on biofilms cultured on porcine skin explants, these ex vivo model data suggest that NPWTi with delivery of active antimicrobial agents enhances the reduction of CFUs by increasing destruction and removal of biofilm bacteria. These results must be confirmed in human studies.

Differential affinity chromatography reveals a link between Porphyromonas gingivalis-induced changes in vascular smooth muscle cell differentiation and the type 9 secretion system.

Porphyromonas gingivalis is implicated in adverse pregnancy outcome. We previously demonstrated that intrauterine infection with various strains of P. gingivalis impairs the physiologic remodeling of the uterine spiral arteries (IRSA) during pregnancy, which underlies the major obstetrical syndromes. Women diagnosed with IRSA also have a greater risk for premature cardiovascular disease in later life. The dysregulated plasticity of vascular smooth muscle cells (VSMCs) is present in both IRSA and premature cardiovascular events. We hypothesized that VSMCs could serve as a bait to identify P. gingivalis proteins associated with dysregulated VSMC plasticity as seen in IRSA. We first confirmed that dams with P. gingivalis A7UF-induced IRSA also show perturbed aortic smooth muscle cell (AoSMC) plasticity along with the P. gingivalis colonization of the tissue. The in vitro infection of AoSMCs with IRSA-inducing strain A7UF also perturbed AoSMC plasticity that did not occur with infection by non-IRSA-inducing strain W83. Far-Western blotting with strain W83 and strain A7UF showed a differential binding pattern to the rat aorta and primary rat AoSMCs. The affinity chromatography/pull-down assay combined with mass spectrometry was used to identify P. gingivalis/AoSMC protein interactions specific to IRSA. Membrane proteins with a high binding affinity to AoSMCs were identified in the A7UF pull-down but not in the W83 pull-down, most of which were the outer membrane components of the Type 9 secretion system (T9SS) and T9SS cargo proteins. Additional T9SS cargo proteins were detected in greater abundance in the A7UF pull-down eluate compared to W83. None of the proteins enriched in the W83 eluate were T9SS components nor T9SS cargo proteins despite their presence in the prey preparations used in the pull-down assay. In summary, differential affinity chromatography established that the components of IRSA-inducing P. gingivalis T9SS as well as its cargo directly interact with AoSMCs, which may play a role in the infection-induced dysregulation of VSMC plasticity. The possibility that the T9SS is involved in the microbial manipulation of host cell events important for cell differentiation and tissue remodeling would constitute a new virulence function for this system.

Fetal growth restriction is a host specific response to infection with an impaired spiral artery remodeling-inducing strain of Porphyromonas gingivalis.

Porphyromonas gingivalis is a periodontal pathogen implicated in a range of pregnancy disorders that involve impaired spiral artery remodeling (ISAR) with or without fetal growth restriction (FGR). Using a rodent periodontitis model, we assessed the ability of P. gingivalis to produce ISAR and FGR in Sprague Dawley (SD) and Wistar (WIS) rats. Both infected SD and WIS rats developed ISAR, but only WIS rats developed FGR despite both rat strains having equivalent microbial loads within the placenta. Neither maternal systemic inflammation nor placental (fetal) inflammation was a feature of FGR in WIS rats. Unique to infected WIS rats, was loss of trophoblast cell density within the junctional zone of the placenta that was not present in SD tissues. In addition, infected WIS rats had a higher proportion of junctional zone trophoblast cells positive for cytoplasmic high temperature requirement A1 (Htra1), a marker of cellular oxidative stress. Our results show a novel phenomenon present in P. gingivalis-induced FGR, with relevance to human disease since dysregulation of placental Htra1 and placental oxidative stress are features of preeclamptic placentas and preeclampsia with FGR.

A Uniquely Altered Oral Microbiome Composition Was Observed in Pregnant Rats With Porphyromonas gingivalis Induced Periodontal Disease.

Porphyromonas gingivalis is an anaerobic bacterium commonly found in the oral cavity and associated with the development of periodontal disease. P. gingivalis has also been linked to several systemic vascular and inflammatory diseases including poor pregnancy outcomes. Little is known about the changes in the oral flora during pregnancy in connection to P. gingivalis infection. This pilot study aims to explore changes in the oral microbiome due to P. gingivalis inoculation and pregnancy in an in vivo rat model of periodontal disease. A metagenomic sequencing analysis targeting seven of the 16S rRNA gene variable regions was performed for oral samples collected at the following time points: baseline control (week 0), P. gingivalis inoculated (week 11), P. gingivalis inoculated and pregnant rat at necropsy (week 16). A second set of animals were also sampled to generate a sham-inoculated (week 11) control group. We found that the rat oral microbiome profiles were more similar to that of the human oral cavity compared to previous reports targeting one or two 16S variable regions. Overall, there appears to be a relatively stable core microbiome in the oral cavity. As expected, P. gingivalis induced periodontal disease resulted in oral microbiome dysbiosis. During pregnancy, some aspects of the oral microbiome shifted toward a more baseline-like profile. However, population analyses in terms of dissimilarity measures and especially metagenomic based predictions of select characteristics such as cell morphology, oxygen requirement, and major metabolite synthesis showed that pregnancy did not restore the composition of the oral microbiome. Rather, a uniquely altered oral microbiome composition was observed in pregnant rats with pre-established periodontal disease.

Deletion of a conserved transcript PG_RS02100 expressed during logarithmic growth in Porphyromonas gingivalis results in hyperpigmentation and increased tolerance to oxidative stress.

The oral obligate anaerobe Porphyromonas gingivalis possesses a small conserved transcript PG_RS02100 of unknown function we previously identified using small RNA-seq analysis as expressed during logarithmic growth. In this study, we sought to determine if PG_RS02100 plays a role in P. gingivalis growth or stress response. We show that a PG_RS02100 deletion mutant's (W83Δ514) ability to grow under anaerobic conditions was no different than wildtype (W83), but it was better able to survive hydrogen peroxide exposure when cultured under heme limiting growth conditions, and was more aerotolerant when plated on enriched whole blood agar and exposed to atmospheric oxygen. Together, these results indicate that PG_RS02100 plays a role in surviving oxidative stress in actively growing P. gingivalis and that P. gingivalis' response to exogenous hydrogen peroxide stress is linked to heme availability. Relative qRT-PCR expression analysis of oxyR, trx-1, tpx, sodB, ahpC, dinF, cydB, and frd, in W83Δ514 and W83 in response to 1 h exogenous dioxygen or hydrogen peroxide exposure, when cultured with varying heme availability, support our phenotypic evidence that W83Δ514 has a more highly primed defense system against exogenous peroxide, dioxygen, and heme generated ROS. Interestingly, W83Δ514 turned black faster than W83 when cultured on whole blood agar, suggesting it was able to accumulate heme more rapidly. The mechanism of increased heme acquisition observed in W83Δ514 is not yet known. However, it is clear that PG_RS02100 is involved in modulating the P. gingivalis cell surface in a manner related to survival, particularly against oxidative stress.

Molecular Mechanisms of Biofilm Infection: Biofilm Virulence Factors.

BACKGROUND: Numerous planktonic virulence factors have been identified that enable bacteria to successfully produce acute infections in tissues. In contrast, very little is known about biofilm virulence factors that enhance the establishment and long-term survival of biofilms in tissues. THE PROBLEM: There is a need to identify the genes that encode biofilm virulence factors and understand how these factors function to enable bacteria to successfully establish chronic biofilm infections in tissues. BASIC SCIENCE ADVANCES: A methodology was developed to screen 6,912 Pseudomonas aeruginosa loss-of-function mutants in a murine model of airway infection to determine which genes were crucial for establishing chronic lung infections in mice. Genetic analysis of 16 bacterial mutants isolated using this methodology identified 15 separate biofilm virulence factor genes whose loss-of-function increased biofilm survival. Sequence analysis of clinical Isolates obtained from seven cystic fibrosis (CF) patients with chronic infections that were collected over 16.3 years identified loss-of-function mutants for 7 of these 15 genes. CLINICAL CARE RELEVANCE: Identifying biofilm virulence factor genes further defines the molecular mechanisms of establishing chronic biofilm infection and should lead to more effective and specific treatments to prevent biofilm formation and/or improve clearance of chronic biofilms in patients. CONCLUSION: Biofilm virulence factor genes were identified in P. aeruginosa using an animal model of chronic lung infection for mutant screening and from infected CF patient isolates. In many cases they were inactivated planktonic virulence factor genes. These results further demonstrate the opposing patterns of gene expression between acute planktonic bacterial infections and chronic biofilm infections.