Comparison of two in vivo and two ex vivo tests to assess the antibacterial activity of several antiseptics

Evaluating the antimicrobial efficacy of long-lasting hand sanitizers on skin

BACKGROUND

The microbicidal efficacy of hand sanitizer formulations is usually measured through standardized quantitative suspension tests and fingerpad tests; these cannot evaluate long-lasting formulations or are impractical due to biological risks, high cost, or time required for testing. With increased numbers of long-lasting microbicidal activity claims of commercially available hand sanitizers, alternative testing strategies are required.

AIM

To explore the use of a standardized ex-vivo pig skin model to reproducibly measure long-lasting efficacy of an alcohol-free hand sanitizer formulation.

METHODS

The microbicidal efficacy of an alcohol-free hand sanitizer was tested against Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae, and the enveloped virus SARS-CoV-2 with quantitative suspension tests (EN13727 and EN14476) with a contact time of 5 min. The product was then tested over a 6 h period using an ex-vivo pig skin model with a modified version of PAS 2424 to simulate the impact of skin abrasion.

FINDINGS

Quantitative suspension tests yielded a >5 log10 reduction for all organisms tested within a 5 min contact time. Pig skin tests showed reduced but consistent efficacy at all time points and indicated no significant impact of abrasion on efficacy.

CONCLUSION

The use of the ex-vivo pig skin model provides a potentially viable and convenient model system to test long-lasting hand sanitizer formulations, providing a path for sustainable hand sanitizer formulation claims of activity on skin.

Successful treatment for acute prosthetic joint infection due to MRSA and Candida albicans: a case report and literature review

Methicillin-resistant Staphylococcus aureus (MRSA) and Candidal prosthetic joint infections (PJIs) are very rare, and the optimal management for these patients is still unknown. A 54-year-old man with traumatic arthritis due to previous electric injury successfully retained the implant despite the successive infection with MRSA and Candida albicans after total knee arthroplasty (TKA). Continuous lavage with vancomycin was used to control MRSA infection and repeated local washout plus oral swallow with voriconazole tablet were administered to eradicate C. albicans. Additional three reported cases were identified by the criteria of selecting patients with concomitant and/or successive MRSA and Candidal PJIs. Different methods were applied with variable outcomes. Therefore, several risk factors such as intra-articular corticosteroid injection, high frequency of door openings in the operating room, excessive blood loss and allogeneic red blood cell transfusions should be avoided. Debridement, antibiotics and implant retention (DAIR) can be an alternative in dedicated patients to control acute MRSA and Candidal PJIs. Particularly, repeated intra-articular washout with susceptible drugs and a prolonged duration of oral antibiotics was essential for microbial control.

Continuous betadine-bacitracin irrigation for vascular graft infections: A case series

The aim of the study was to conduct a retrospective chart review of patients who underwent betadine/bacitracin continuous irrigation (BBCI) for vascular graft infections (VGIs) to review its use as a treatment option. A retrospective chart review from 2013 to 2017 was conducted of patients with VGIs that were treated with BBCI postremoval of the infected graft. The BBCI is a continuous infusion of 0.25% betadine in normal saline at 0.3 mL/kg/h for 48 hours then followed by bacitracin infusion with a concentration of 50,000 units bacitracin/per liter normal saline at 0.3 mL/kg/h for 72 hours. Descriptive statistics were used to describe the sample. The nine adult patients who received postoperative BBCI had an age range of 30-81 years, with average age of 58.8 years. Five of the subjects were females with four males. A total of nine patients with groin infections were identified, with two aortobifemoral bypasses, two axillofemoral bypasses, three femoral-femoral bypasses, one femoral artery pseudoaneurysm repair with Dacron patch, and one common femoral endarterectomy with Dacron patch. VGIs were identified from 10 days up to 72 months from the original vascular procedure. Six patients had negative wound cultures, while two had wound cultures positive for methicillin-resistant Staphylococcus aureus and one patient had positive culture for Escherichia coli. The length of time of BBCI ranged from 48 to 84 hours with average of 57.6 hours (standard deviation [SD] = 12.7 hours). The length of time of the bacitracin irrigation ranged from 30 to 72 hours with average of 48.4 hours (SD = 14.9 hours). All patients healed their groin wounds except for an 81-year-old patient with aortobifemoral bypass graft who developed ischemic bowel and expired. Patients received at least 6 weeks of intravenous antibiotics followed by oral antibiotic suppression therapy for life. VGIs are a devastating complication associated with a high morbidity. BBCI provides an option for antiseptic irrigation of the vascular graft site postgraft removal to promote wound closure.

Quantitative evaluation of dermatological antiseptics

Topical antiseptics are frequently used in dermatological management, yet evidence for the efficacy of traditional generic formulations is often largely anecdotal. We tested the in vitro bactericidal activity of four commonly used topical antiseptics against Staphylococcus aureus, using a modified version of the European Standard EN 1276, a quantitative suspension test for evaluation of the bactericidal activity of chemical disinfectants and antiseptics. To meet the standard for antiseptic effectiveness of EN 1276, at least a 5 log10 reduction in bacterial count within 5 minutes of exposure is required. While 1% benzalkonium chloride and 6% hydrogen peroxide both achieved a 5 log10 reduction in S. aureus count, neither 2% aqueous eosin nor 1 : 10 000 potassium permanganate showed significant bactericidal activity compared with control at exposure periods of up to 1 h. Aqueous eosin and potassium permanganate may have desirable astringent properties, but these results suggest they lack effective antiseptic activity, at least against S. aureus.

Evaluation of an Alcohol-Based Surgical Hand Disinfectant Containing a Synergistic Combination of Farnesol and Benzethonium Chloride for Immediate and Persistent Activity Against Resident Hand Flora of Volunteers and With a Novel In Vitro Pig Skin Model

Objective.

To evaluate the immediate, persistent and sustained in vivo activity of an alcohol-based surgical hand disinfectant, consisting of a zinc gel and a preservative system containing a synergistic combination of farnesol and benzethonium chloride (ZBF disinfectant), and to develop a pig skin model for in vitro evaluation of the immediate and persistent efficacy of alcohol-based surgical hand disinfectants against resident hand flora.

Design.

The in vivo immediate, persistent, and sustained activity of ZBF disinfectant was evaluated using human volunteers and the “glove-juice” method described in the US Food and Drug Administration's Tentative Final Monograph (FDA-TFM) for Healthcare Antiseptic Products. A novel in vitro pig skin model was developed to compare the immediate and persistent activity of alcohol-based surgical hand disinfectants against resident flora usingStaphylococcus epidermidisas the test organism. Four alcohol-based surgical hand disinfectants were evaluated using this model.

Results.

The results for the ZBF disinfectant exceed the FDA-TFM criteria for immediate, persistent, and sustained activity required for surgical hand disinfectants. The reduction factors for the 4 hand disinfectants obtained using the pig skin model show good agreement with the log10reductions in concentrations of hand flora obtained using human volunteers to test for immediate and persistent activity.

Conclusion.

The ZBF disinfectant we evaluated met the FDA-TFM criteria for surgical hand disinfectants. The immediate and persistent efficacy of the surgical hand disinfectants evaluated with the novel pig skin model described in this study shows good agreement with the results obtained in vivo.

Management of non-healable or maintenance wounds with topical povidone iodine

Although complete healing may appear to be the logical goal for most patients and clinicians, some wounds do not have the potential to heal due to a number of factors such as inadequate vasculature, coexisting medical conditions and medications that prohibit the healing process. Local management of wounds that are considered to have poor potential for healing remains elusive. The purpose of this article is to review the evidence that supports the use of topical antiseptic agents in non-healable wounds. Retrospective chart audit was conducted to evaluate the use of povidone iodine in the management of wounds that were deemed to have poor healing potential.

Decolonisation of MRSA, S. aureus and E. coli by cold-atmospheric plasma using a porcine skin model in vitro

In the last twenty years new antibacterial agents approved by the U.S. FDA decreased whereas in parallel the resistance situation of multi-resistant bacteria increased. Thus, community and nosocomial acquired infections of resistant bacteria led to a decrease in the efficacy of standard therapy, prolonging treatment time and increasing healthcare costs. Therefore, the aim of this work was to demonstrate the applicability of cold atmospheric plasma for decolonisation of Gram-positive (Methicillin-resistant Staphylococcus aureus (MRSA), Methicillin-sensitive Staphylococcus aureus) and Gram-negative bacteria (E. coli) using an ex vivo pig skin model. Freshly excised skin samples were taken from six month old female pigs (breed: Pietrain). After application of pure bacteria on the surface of the explants these were treated with cold atmospheric plasma for up to 15 min. Two different plasma devices were evaluated. A decolonisation efficacy of 3 log₁₀ steps was achieved already after 6 min of plasma treatment. Longer plasma treatment times achieved a killing rate of 5 log₁₀ steps independently from the applied bacteria strains. Histological evaluations of untreated and treated skin areas upon cold atmospheric plasma treatment within 24 h showed no morphological changes as well as no significant degree of necrosis or apoptosis determined by the TUNEL-assay indicating that the porcine skin is still vital. This study demonstrates for the first time that cold atmospheric plasma is able to very efficiently kill bacteria applied to an intact skin surface using an ex vivo porcine skin model. The results emphasize the potential of cold atmospheric plasma as a new possible treatment option for decolonisation of human skin from bacteria in patients in the future without harming the surrounding tissue.

Antimicrobial activity of a chlorhexidine intravascular catheter site gel dressing

OBJECTIVES

The antimicrobial efficacy of a chlorhexidine gluconate (CHG) intravascular catheter gel dressing was evaluated against methicillin-resistant Staphylococcus aureus (MRSA) and an extended-spectrum β-lactamase (ESBL)-producing Escherichia coli. Chlorhexidine deposition on the skin surface and release from the gel were determined.

METHODS

The antimicrobial efficacy was evaluated in in vitro studies following microbial inoculation of the dressing and application of the dressing on the inoculated surface of a silicone membrane and donor skin [with and without a catheter segment and/or 10% (v/v) serum] on diffusion cells. Antimicrobial activity was evaluated for up to 7 days. Chlorhexidine skin surface deposition and release were also determined.

RESULTS

MRSA and E. coli were not detectable within 5 min following direct inoculation onto the CHG gel dressing. On the silicone membrane, 3 log and 6 log inocula of MRSA were eradicated within 5 min and 1 h, respectively. Time to kill was prolonged in the presence of serum and a catheter segment. Following inoculation of donor skin with 6 log cfu of MRSA, none was detected after 24 h. Chlorhexidine was released from the gel after a lag time of 30 min and increasing amounts were detected on the donor skin surface over the 48 h test period. The CHG gel dressing retained its antimicrobial activity on the artificial skin for 7 days.

CONCLUSIONS

The CHG intravascular catheter site gel dressing had detectable antimicrobial activity for up to 7 days, which should suppress bacterial growth on the skin at the catheter insertion site, thereby reducing the risk of infection.

Clostridium difficile colitis: a retrospective study of incidence and severity before and after institution of an alcohol-based hand rub policy

BACKGROUND

Clostridium difficile-associated diarrhea is a leading cause of hospital-acquired diarrhea. We sought to determine whether the institution of a hospital-wide alcohol-based hand rub (ABHR) policy was associated with an increase in the incidence and/or severity of health care facility-onset, health care facility-associated C difficile diarrhea (CDAD).

METHODS

We used a retrospective chart review analysis to compare incidence rates of CDAD before and after implementation of the ABHR policy. We also compared rates of sepsis, colectomy, and death in patients with CDAD before and after implementation of the ABHR policy.

RESULTS

The incidence rate of CDAD was 3.98 per 10,000 patient-days after implementation of the ABHR policy, compared with 4.96 per 10,000 patient-days before implementation (P = .0036). The crude mortality rate in patients diagnosed with CDAD was 10.7% after implementation, compared with 13.3% before implementation (P = .275). The rate of sepsis in patients diagnosed with CDAD was 19.6% after implementation, compared with 5.2% before implementation (P < .0001).

CONCLUSION

Our data provide no evidence of an increased CDAD rate after implementation of an ABHR policy at our institution. The rate of sepsis in patients diagnosed with CDAD did rise, indicating increased severity of illness in patients with C difficile infection.

Evaluation of the bactericidal efficacy of three different alcohol hand rubs against 57 clinical isolates of S. aureus

We tested the efficacy of three alcohol hand rubs (AHRs) used in two local Welsh intensive therapy units (ITUs) against Staphylococcus aureus. The test protocol was based on a carrier test and parameters (concentration, contact time) were chosen following observation of hand-sanitising practices in the ITUs. Following AHR exposure, surviving bacteria were enumerated using a standard plate count method plus a Bioscreen C Microbial Growth Analyser. The AHRs demonstrated variable efficacy against the clinical isolates: the mean log(10) reduction after 10 s exposure to Soft Care Med H5, Cutan and Guest Medical AHRs was 2.67, 0.696 and 1.96, respectively, and after 30 s exposure was 4.58, 1.74 and 3.60, respectively. Since the average time taken by healthcare workers (HCWs) to rub AHR onto their hands was 11 s and 15 s at the two hospitals, the efficacy of these AHRs may be significantly limited against the S. aureus isolates under the conditions observed in practice. In addition, differences observed in log(10) reduction in bacterial number post-exposure using the Bioscreen compared to the plate count method provided evidence that S. aureus may be able to recover following Guest Medical AHR treatment within 2 min exposure, whereas after 5 min exposure bacterial damage caused by the AHR was irreversible. Although the introduction of AHRs improved hand hygiene compliance among HCWs, our observations highlighted that contact time is an important factor to ensure the efficacy of these products.

Determination of the antibacterial efficacy of a new porphyrin-based photosensitizer against MRSA ex vivo

Following extensive in vitro screening of new photosensitizers the purpose of the present study was to examine penetration as well as antibacterial efficacy of a lead photosensitizer against MRSA using an ex vivo porcine skin model. Two different applications were performed: (i) preincubation of bacteria in solution with a porphyrin-based photosensitizer XF73 and subsequent application on the ex vivo porcine skin; (ii) application of pure bacteria on the explants followed by an incubation with XF73 in a water-ethanol formulation for up to 60 min under occlusion. The localisation of XF73 was restricted to the stratum corneum. Different concentrations (0-10 microM) of XF73 and different incubation times (5-60 min) were used to determine phototoxicity against methicillin-resistant and methicillin-sensitive S. aureus, which was applied on the explants. Preincubation of S. aureus with 0.1 microM XF73 in solution prior to the application of these XF73-incubated bacteria on the skin demonstrates a higher efficacy (>3 log10) after irradiation. Antibacterial photodynamic inactivation resulted in a approximately 1 log10 (0.1 microM)-3.64+/-0.035 (10 microM) log10 growth reduction independently of the antibiotic resistance pattern of used S. aureus strains. Irradiation of applied bacteria without photosensitizer incubation did not show any marked decrease (<1 log10) of bacteria cell number, indicating a significant phototoxicity of the XF73. Histological evaluations of untreated and treated skin areas upon irradiation within 24 h showed no significant degree of necrosis or apoptosis determined by TUNEL-assay indicating that the porcine skin is still vital. This study demonstrates that this XF73 porphyrin-based photosensitizer had concentration-dependent differences in killing efficacy of MRSA in comparison to skin cells using an ex vivo porcine skin model. The results described here imply that topical delivery of XF73 may be considered as a possible treatment in patients with superficial infections of the skin.

Evaluation of povidone-iodine as a disinfectant solution for contact lenses: Antimicrobial activity and cytotoxicity for corneal epithelial cells

Povidone-iodine (PVP-I) possesses broad-spectrum antimicrobial activity and is used clinically as a disinfectant. We evaluated the disinfectant properties and safety of PVP-I for use as a contact lens solution. The concentrations of PVP-I required to reduce the number of Staphylococcus aureus or Candida albicans by 3 log units were lower than were those of hydrogen peroxide, polyhexamethylene biguanide (PHMB), and benzalkonium chloride (BAK). The cytotoxicity of PVP-I for cultured human corneal epithelial (HCE) cells was less than that of the other three agents. The safety margin for PVP-I was thus greatest among the tested compounds. PVP-I appears suited for use as a contact lens disinfectant.

Evidence-Based Practice in the Management of Vascular Access Devices for Home Parenteral Nutrition Therapy

Catheter-related bloodstream infection and catheter occlusion are potential significant complications of parenteral nutrition therapy. The increased incidence and associated morbidity, mortality, increased costs, and quality-of-life issues experienced with these adverse events necessitate specialized management of vascular access devices. The host coagulation response to biomaterials and the associated development of biofilm on vascular devices are complex phenomena. Multiple interventions are required to prevent access of bacteria to both intraluminal and extraluminal catheter surfaces, and the occurrence of catheter occlusion. The discovery of the biofilm form of microbial life and the associated recalcitrance of biofilm bacteria to antimicrobials has provided insight into the failure of current prevention, diagnostic, and treatment protocols. Critical interventions are presented correlating current evidence with new discoveries in pathogenesis.

Effectiveness of hand-cleansing formulations containing tea tree oil assessed ex vivo on human skin and in vivo with volunteers using European standard EN 1499

The efficacy of formulations containing tea tree oil (TTO) has been assessed in vitro in previous studies. Products that passed the European suspension test guidelines were investigated further in this study, in vivo with volunteers using the European handwashing method (EN 1499) and ex vivo using freshly excised human skin samples. The activity of 5% TTO in 0.001% Tween 80, in a hygienic skin wash (HSW) and in an alcoholic hygienic skin wash (AHSW) was investigated and compared with that of a non-medicated soft soap (SS, control). These formulations were assessed against Escherichia coli K12 as recommended by the European standard. In-vivo results showed that 5% TTO in Tween 80 and the AHSW were significantly more active than the SS after 1 min of handwashing. When assessed ex vivo, these two products were also significantly more active than the reference soap after 1 min of rubbing. Both methods showed that 5% TTO in Tween 80 was generally, although not always, more active than a handwash formulation, and that the AHSW was generally more active than the HSW, although this difference was not significant. The formulations tested, as well as the SS, were more active when assessed in vivo than ex-vivo against E. coli, although only the SS and the HSW were significantly more active in vivo. There appeared to be a pattern in the comparison between ex vivo and in vivo results. The antiseptics tested were, on average, 1.28+/-0.06 times more active when assessed in-vivo than when assessed ex vivo. Nevertheless, the main outcome of the European handwashing method is for the formulation tested to be significantly more active than the SS; both 5% TTO in Tween 80 and the AHSW achieved this both in-vivo and ex-vivo. TTO in Tween 80 and in formulations met the European in-vivo method requirements.