ISSN Staphylococcus aureus is a common pathogen associated with serious community and hospital-acquired diseases and has long been considered as a major problem of public health. This potent Gram-positive bacterium is able to bypass all barriers of the host defense system as it possesses a wide spectrum of virulence factors. S. aureus is also one of the prominent pathogens in biofilm-related infections of indwelling medical devices, which are responsible for billions in healthcare cost each year in the United States. S. aureus expresses a large number of virulence factors that are implicated in their pathogenesis. Methicillin-resistant S. aureus infections have reached epidemic levels in many parts of the world. This review describes the virulence factors, pathogenesis, and antibiotic resistance in S. aureus. Copyright 2016 Wolters Kluwer Health, Inc. All rights reserved.

A review of virulence factors, pathogenesis, and antibiotic resistance in Staphylococcus aureus

Background: Staphylococcus aureus is a bacterial pathogen that can cause a wide range of nosocomial infections. Nasal colonization by S. aureus plays an important role both in the epidemiology and pathogenesis of infection. Objectives: This study aimed at detecting the biofilm-forming capacity of clinical isolates and detection of icaA and agr genes. Methods: A total of 150 clinical specimens was collected from patients in different hospitals in Baghdad. The clinical samples included wounds, abscess, sputum, and ear infections. The suspected isolates were cultured for one day at 37 °C on mannitol salt agar in an aerobic environment. Results: The results showed that of 150 samples, 44 isolates were S. aureus (29.3%), of wounds samples, 22 isolates (45.83%) were S. aureus, 13 (37.14%) were from abscess, 7 (17.95%) from sputum, and 2 isolates (7.14%) from ear samples. This study found that most isolates formed biofilm, but the levels of biofilm were distributed across three ranges. The results also indicated that 47.7% of the isolates produced a strong biofilm, as well as 38.6 and 13.6% produced moderate and weak biofilms, respectively. The present molecular results showed that S. aureus from different samples were 13 (59.1%), 4 (30.77%), 3 (42.85%), 0 (0%) from wounds, abscess, sputum, ear, respectively, were positive for agr gene. While the results showed 18 (81.8%), 10 (76.9%), 5 (71.4%), 1 (50%), respectively, were positive for icaA gene. Conclusions: Most S. aureus isolates isolated from wound were biofilm positive. These isolates bore icaA and agr genes in a high quantity.

Phenotypic and Genotypic Characterization of Antibiotic Resistance in Staphylococcus aureus Isolated from Different Sources

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Effective biofilm removal and changes in bacterial biofilm building capacity after wound debridement with low-frequency ultrasound as part of wound bed preparation before skin grafting

The aim of the present study was to assess the ability of predominantly used probiotic strain Lactobacillus acidophilus La-5 to inhibit the growth and biofilm formation by Methicillin Resistant clinical isolates of S. aureus. A total of 41 clinical isolates of S. aureus were collected from wound samples of patients. Biofilm formation assay was performed using microtiter plate. At 24h incubation, 13 (31.70%, P<0.5) of the clinical isolates were strongly adherent, 25 (60.97%, P<0.5) were moderately adherent and only 3 (7.31%, P<0.5) were weakly adherent. Agar overlay interference test was employed to study the ability of L. acidophilus La-5 to inhibit the growth of S. aureus. The growth was completely inhibited at higher cell concentrations of L. acidophilus (107- 109). The inhibitory effects declined with lowering of cell concentration. The assay to study the inhibition of biofilm formation was conducted using microtiter plate and staining with crystal violet. Only 5 of the 13 strong biofilm producers were able to form biofilm upon introduction of probiotic strain. There were only 6 out of 25 moderate biofilm producers and none of the three weak biofilm formers were able to form biofilm upon co-inoculation with L. acidophilus La-5.

Lactobacillus Acidophilus la-5 Inhibits Growth and Biofilm Formationof Methicillin Resistant Staphylococcus aureus Isolated from Wounds ofHospitalized Patients

Introduction: Periprosthetic joint infections (PJI) are increasing as a result of increased major joint arthroplasty (MJA). Classical treatment of PJI is a two-stage revision. However, this approach results in morbidity and is not cost effective. We investigated whether covering of the implants with bone cement is sufficient for eradication of microorganism on biofilm.
Materials and Methods: 24 plates were infected by Methicillin-resistant S. aureus (MRSA) in tryptic soy broth (TSB) for biofilm formation for 48 h. They are divided into four groups. Biofilm and living bacteria were shown in first and second groups. Infected implants were covered with bone cement to show eradication of biofilm in third and fourth groups. After implants were covered with bone cement, the bone cement was broken 24 h later, in sterile conditions. Implants were evaluated in terms of bacteria colonies by using the dilutions method.
Results: The biofilm was shown in group I by using scanning electron microscopy (SEM). Bacteria colonies were very high in number in group II (3.1 ± 0.3. Mean cfu × 108 ± SEM). Bacteria colonies weren’t identified in groups III and IV (0 ± 0 Mean cfu × 108 ± SEM). There were statistical differences between the group II and group III-IV (P 0.05).
Conclusion: This study shows that, Staphylococci biofilm formation on orthopaedic implants can be eradicated completely by covering the implants with bone cement. PJI may be treated by covered with bone cement without removed implants.

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Can the biofilm produced by Staphylococcus aureus on implant be eradicated by covered with bone cement? in vitro study

Introduction: Staphylococcus aureus is frequently found in chronic wounds. Bacterial biofilms within chronic wounds impact on the surgical closure of the wounds with skin grafting. Methods of wound bed preparation (WBP) influence the microorganisms within the biofilm. We used in vitro monitoring to analyse the possible influence of WBP methods on the in vivo formation of biofilms. Aim: To conduct a comparative analysis of the impact of WBP treatment methods on the capacity of S. aureus isolated from chronic wounds to form biofilms in vitro. Methods: We modeled S. aureus biofilm formation in 96-well plates. We assayed the capacity of bacteria isolated from chronic wounds to form biofilms at the time of patient admission and after treatment with either ultrasound debridement (UD) and topical negative pressure (TNP; Main Group) or standard dressings (Control Group). We also compared biofilm formation by bacteria from patients with different grafting outcomes. Results: The treatment of chronic wounds with UD and TNP reduced the capacity of S. aureus to synthesise a major biofilm substance. S. aureus isolates from patients with favourable skin-grafting results had a lower capacity to form biofilms in vitro compared with isolates from patients with poor skin-grafting results. The use of UD and TNP for surgical closure reduced the length of the skin-graft healing process compared with the use of standard bandages. Conclusion: The isolation from chronic wounds of significant titers of S. aureus strains with a high capacity to form biofilms within 2 to 6 hours of incubation in vitro highlights the advantage of using hardware methods (UD and TNP) for WBP for surgical closure.

Leonid Rubanov

Papers

The Biofilm-forming capacity of staphylococcus aureus from chronic wounds can be useful for determining Wound-Bed Preparation methods