Production of biofilm by Staphylococcus aureus: Association with infective endocarditis?

OBJECTIVES: Staphylococcus aureus is a well-known biofilm-producing pathogen that is capable of causing chronic infections owing to its ability to resist antibiotic treatment and obstruct the immune response. However, the possible association between high biofilm production and infective endocarditis (IE) has not been assessed. Our objective was to compare production of biofilm by S. aureus strains isolated from patients with bacteremia and IE, catheter-related bloodstream infection (C-RBSI), or non-device associated bacteremia. METHODS: We isolated 260 S. aureus strains from the blood of patients with bacteremia who were diagnosed during hospital admission between 2012 and 2015. Patients were divided into 3 groups according to whether they had IE, C-RBSI, or non-device associated bacteremia. Biofilm production was measured in terms of biomass and metabolic activity using the crystal violet and XTT assays, respectively. High biomass and metabolic activity rates (based on tertile ranks classification) were compared between the 3 groups. RESULTS: The high biomass and metabolic activity rates of each group were 41.9% and 37.2% for IE, 32.5% and 35.0%, for C-RBSI, and 29.0% and 33.3% for non-device associated bacteremia (p=0.325 and p=0.885, respectively). CONCLUSIONS: High biomass and metabolic activity levels for S. aureus isolates from IE were similar to those of S. aureus isolates from C-RBSI or non-device associated bacteremia.

The classification of Staphylococcus aureus strains by biofilm production differs depending on the method used.

INTRODUCTION: Strains can be classified in terms of biofilm production from quantitative absorbance values collectively by dividing strains into tertile ranks or individually by calculating the optical density for the negative control. However, these methods have not been compared in a large sample of Staphylococcus aureus strains. Therefore, our objective was to analyze the agreement between both methods in terms of biomass production and metabolic activity of their biofilm. METHODS: We classified 233 S. aureus strains by biomass production and metabolic activity using the crystal violet and XTT assays, respectively. Strains were classified as low, moderate, or high biofilm producers according to tertile or optical density. RESULTS: We found no agreement between both methods (p<0.001 and p=0.028, respectively). CONCLUSIONS: We consider strains' biofilm classification by optical density to be a more reliable method, as it depends on the individual absorbance of each strain.

The role of biofilm production in Cutibacterium acnes strains isolated from breast implants.

The role of C. acnes biofilm production in the pathogenesis of breast implants infections has not been deeply assessed. We analyze biofilm production (in terms of biomass and metabolic activity) between 40 Cutibacterium acnes strains isolated from breast implants and 32 from other sites. C. acnes strains isolated from breast implants showed higher metabolic activity than those isolated from other-locations and, especially, those from patients with capsular contracture .

Production of biofilm by Staphylococcus aureus: Association with infective endocarditis?

OBJECTIVES: Staphylococcus aureus is a well-known biofilm-producing pathogen that is capable of causing chronic infections owing to its ability to resist antibiotic treatment and obstruct the immune response. However, the possible association between high biofilm production and infective endocarditis (IE) has not been assessed. Our objective was to compare production of biofilm by S. aureus strains isolated from patients with bacteremia and IE, catheter-related bloodstream infection (C-RBSI), or non-device associated bacteremia. METHODS: We isolated 260 S. aureus strains from the blood of patients with bacteremia who were diagnosed during hospital admission between 2012 and 2015. Patients were divided into 3 groups according to whether they had IE, C-RBSI, or non-device associated bacteremia. Biofilm production was measured in terms of biomass and metabolic activity using the crystal violet and XTT assays, respectively. High biomass and metabolic activity rates (based on tertile ranks classification) were compared between the 3 groups. RESULTS: The high biomass and metabolic activity rates of each group were 41.9% and 37.2% for IE, 32.5% and 35.0%, for C-RBSI, and 29.0% and 33.3% for non-device associated bacteremia (p=0.325 and p=0.885, respectively). CONCLUSIONS: High biomass and metabolic activity levels for S. aureus isolates from IE were similar to those of S. aureus isolates from C-RBSI or non-device associated bacteremia.

Endotracheal tubes coated with a broad-spectrum antibacterial ceragenin reduce bacterial biofilm in an in vitro bench top model.

BACKGROUND: Ventilator-associated pneumonia is one of the most common nosocomial infections, caused mainly by bacterial/fungal biofilm. Therefore, it is necessary to develop preventive strategies to avoid biofilm formation based on new compounds. OBJECTIVES: We performed an in vitro study to compare the efficacy of endotracheal tubes (ETTs) coated with the ceragenin CSA-131 and that of uncoated ETTs against the biofilm of clinical strains of Pseudomonas aeruginosa (PA), Escherichia coli (EC) and Staphylococcus aureus (SA). METHODS: We applied an in vitro bench top model using coated and uncoated ETTs that were treated with three different clinical strains of PA, EC and SA for 5 days. After exposure to biofilm, ETTs were analysed for cfu count by culture of sonicate and total number of cells by confocal laser scanning microscopy. RESULTS: The median (IQR) cfu/mL counts of PA, EC and SA in coated and uncoated ETTs were, respectively, as follows: 1.00 × 101 (0.0-3.3 × 102) versus 3.32 × 109 (6.6 × 108-3.8 × 109), P < 0.001; 0.0 (0.0-5.4 × 103) versus 1.32 × 106 (2.3 × 103-5.0 × 107), P < 0.001; and 8.1 × 105 (8.5 × 101-1.4 × 109) versus 2.7 × 108 (8.6 × 106-1.6 × 1011), P = 0.058. The median (IQR) total number of cells of PA, EC and SA in coated and non-coated ETTs were, respectively, as follows: 11.0 [5.5-not applicable (NA)] versus 87.9 (60.5-NA), P = 0.05; 9.1 (6.7-NA) versus 62.6 (42.0-NA), P = 0.05; and 97.7 (94.6-NA) versus 187.3 (43.9-NA), P = 0.827. CONCLUSIONS: We demonstrated significantly reduced biofilm formation in coated ETTs. However, the difference for SA was not statistically significant. Future clinical studies are needed to support our findings.

The classification of Staphylococcus aureus strains by biofilm production differs depending on the method used.

INTRODUCTION: Strains can be classified in terms of biofilm production from quantitative absorbance values collectively by dividing strains into tertile ranks or individually by calculating the optical density for the negative control. However, these methods have not been compared in a large sample of Staphylococcus aureus strains. Therefore, our objective was to analyze the agreement between both methods in terms of biomass production and metabolic activity of their biofilm. METHODS: We classified 233 S. aureus strains by biomass production and metabolic activity using the crystal violet and XTT assays, respectively. Strains were classified as low, moderate, or high biofilm producers according to tertile or optical density. RESULTS: We found no agreement between both methods (p<0.001 and p=0.028, respectively). CONCLUSIONS: We consider strains' biofilm classification by optical density to be a more reliable method, as it depends on the individual absorbance of each strain.

Selective digestive decontamination solution used as "lock therapy" prevents and eradicates bacterial biofilm in an in vitro bench-top model.

BACKGROUND: Most preventing measures for reducing ventilator-associated pneumonia (VAP) are based mainly on the decolonization of the internal surface of the endotracheal tubes (ETTs). However, it has been demonstrated that bacterial biofilm can also be formed on the external surface of ETTs. Our objective was to test in vitro the efficacy of selective digestive decontamination solution (SDDs) onto ETT to prevent biofilm formation and eradicate preformed biofilms of three different microorganisms of VAP. METHODS: We used an in vitro model in which we applied, at the subglottic space of ETT, biofilms of either P. aeruginosa ATCC 15442, or E. coli ATCC 25922, or S. aureus ATCC 29213, and the SDDs at the same time (prophylaxis) or after 72 h of biofilm forming (treatment). ETT were incubated during 5 days with a regimen of 2 h-locks. ETT fragments were analyzed by sonication and confocal laser scanning microscopy to calculate the percentage reduction of cfu and viable cells, respectively. RESULTS: Median (IQR) percentage reduction of live cells and cfu/ml counts after treatment were, respectively, 53.2% (39.4%-64.1%) and 100% (100%-100.0%) for P. aeruginosa, and 67.9% (46.7%-78.7%) and 100% (100%-100.0%) for E. coli. S. aureus presented a complete eradication by both methods. After prophylaxis, there were absence of live cells and cfu/ml counts for all microorganisms. CONCLUSIONS: SDDs used as "lock therapy" in the subglottic space is a promising prophylactic approach that could be used in combination with the oro-digestive decontamination procedure in the prevention of VAP.

Correction: Is heparinized 40% ethanol lock solution efficient for reducing bacterial and fungal biofilms in an in vitro model?

[This corrects the article DOI: 10.1371/journal.pone.0219098.].

Is heparinized 40% ethanol lock solution efficient for reducing bacterial and fungal biofilms in an in vitro model?

BACKGROUND: We applied an in vitro model to evaluate the efficacy of a heparinized 40% ethanol-based lock solution in a wide variety of clinical isolates causing C-RBSI. METHODS: A total of 100 clinical strains were collected retrospectively from the blood of patients with C-RBSI. The reduction in biomass and metabolic activity of biofilms was measured using the crystal violet (CV) assay and XTT assay, respectively. Regrowth inhibition (RI) was measured within 24 hours and 72 hours of ethanol lock therapy. Percentage reduction of ≥ 85% in RI was considered to be successful. RESULTS: Ethanol lock was more effective in reducing metabolic activity than in reducing biomass (83% vs. 50%, respectively). Percentages of RI diminished as regrowth was prolonged (57% for 24 hours and 17% for 72 hours of regrowth). No statistically significant intraspecies differences were found in biofilm reduction or in RI (p>0.05). CONCLUSIONS: The use of heparinized 40% ethanol lock solution for 72 hours significantly reduced biomass and metabolic activity in clinical isolates from patients with C-RBSI. However, as biofilm has an important regrowth rate, 40% ethanol solution was not able to fully eradicate biofilm in vitro.

Evaluation of the Alfred™ turbidity monitoring system (Alifax®) following sonication in the diagnosis of central venous catheter colonization.

The conventional diagnostic techniques for catheter colonization (CC) take at least 48 h to yield results. Therefore, new diagnostic procedures that speed up the time necessary for results are needed. Our main objective was to assess the efficacy of the combination of sonication, turbidity monitoring, and MALDI-TOF to detect CC and catheter-related bloodstream infection (C-RBSI). For 1 year, we assessed central venous catheter (CVC) tips that arrived at the microbiology laboratory from adult patients admitted to our institution. CVC tips were cut, inoculated into 2.5 ml of BHI, and sonicated for 1 min. The suspension was then processed using Gram stain, quantitative culture (gold standard), and preincubation on the Alfred™ system. We analyzed the validity values of our new diagnostic approach for prediction of CC and C-RBSI and compared them with those of the gold standard. We collected a total of 167 catheters, 33 (19.8%) of which were colonized. We confirmed 21 episodes of C-RBSI. The distribution of microorganisms in colonized CVCs was as follows: Gram-positive, 68.4%; Gram-negative, 5.3%; and yeasts, 26.3%. The validity values for CC and C-RBSI using the new procedure were as follows: S, 39.4%/61.9%; Sp, 100%/100%; PPV, 100%/100%; and NPV, 87.0%/94.8%. The combination of sonication with a pre-incubation period based on turbidity monitoring using the Alfred™ system followed by MALDI-TOF proved to be a useful tool that was faster than conventional culture for ruling out C-RBSI. Future studies are needed to assess the clinical and economic impact of this diagnostic approach.

Eradication of P. aeruginosa biofilm in endotracheal tubes based on lock therapy: results from an in vitro study.

BACKGROUND: Despite the several strategies available for the management of biofilm-associated ventilator-associated pneumonia, data regarding the efficacy of applying antibiotics to the subglottic space (SS) are scarce. We created an in vitro model to assess the efficacy of antibiotic lock therapy (ALT) applied in the SS for eradication of Pseudomonas aeruginosa biofilm in endotracheal tubes (ETTs). METHODS: We applied 2 h of ALT to a P. aeruginosa biofilm in ETTs using a single dose (SD) and a 5-day therapy model (5D). We used sterile saline lock therapy (SLT) as the positive control. We compared colony count and the percentage of live cells between both models. RESULTS: The median (IQR) cfu counts/ml and percentage of live cells in the SD-ALT and SD-SLT groups were, respectively, 3.12 × 105 (9.7 × 104-0) vs. 8.16 × 107 (7.0 × 107-0) (p = 0.05) and 53.2% (50.9%-57.2%) vs. 91.5% (87.3%-93.9%) (p < 0.001). The median (IQR) cfu counts/ml and percentage of live cells in the 5D-ALT and 5D-SLT groups were, respectively, 0 (0-0) vs. 3.2 × 107 (2.32 × 107-0) (p = 0.03) and 40.6% (36.6%-60.0%) vs. 90.3% (84.8%-93.9%) (p < 0.001). CONCLUSION: We demonstrated a statistically significant decrease in the viability of P. aeruginosa biofilm after application of 5D-ALT in the SS. Future clinical studies to assess ALT in patients under mechanical ventilation are needed.