Effect of Different Incubation Atmospheres on the Production of Biofilm in Methicillin-Resistant Staphylococcus aureus (MRSA) Grown in Nutrient-Limited Medium

Bacterial Adaptive Memory in Methicillin-Resistant Staphylococcus aureus from Endotracheal Tubes

OBJECTIVES

To evaluate the expression dynamics of biofilm genes in methicillin-resistant Staphylococcus aureus (MRSA) retrieved from endotracheal tubes (ETT) and to determine how gene regulation is attenuated in vitro where host-environmental factors are no longer present.

METHODS

Biofilm was grown (24 h) in tryptic broth soy plus 0.25% glucose for a clinical MRSA isolate in planktonic state and after sessile growth named ETT-MRSA (S2, S3, S4, S5, S6, S7). Gene expression of five biofilm-related genes (icaC, clfB, ebps, fnbB, and RNA III) was assessed consecutively from day 1 to day 4 after ETT growth through real-time PCR. 16S rRNA was used as a control.

RESULTS

The MRSA isolates retrieved from ETT were capable of producing biofilms dependent on ica. The gene expression dynamics of ETT-MRSA changed progressively compared to planktonic MRSA gene expression under both ambient air (p < 0.001) and ambient air with 5% CO2 (p < 0.001). Dynamic assessment of icaC expression in both atmospheric conditions showed progressive downregulation in vitro compared to in vivo ETT biofilms. The expression patterns of clfB and ebps genes were similar to icaC. In contrast, the expression of the RNA III gene showed progressive upregulation from day 1 to day 4 (p < 0.001).

CONCLUSIONS

MRSA loses its biofilm gene expression in vitro, by adaptive features across multiple generations, as evidenced by the progressive downregulation of icaC and upregulation of RNA III. These findings underscore the significance of host-environment dependence in regulating bacterial biofilm genes, highlighting its importance in diagnostics. Bacterial strains lose their host-specific characteristics as they are cultured in vitro.

Current therapies and challenges for the treatment of Staphylococcus aureus biofilm-related infections

Staphylococcus aureus is a major cause of nosocomial and community-acquired infections and contributes to significant increase in morbidity and mortality especially when associated with medical devices and in biofilm form. Biofilm structure provides a pathway for the enrichment of resistant and persistent phenotypes of S. aureus leading to relapse and recurrence of infection. Minimal diffusion of antibiotics inside biofilm structure leads to heterogeneity and distinct physiological activity. Additionally, horizontal gene transfer between cells in proximity adds to the challenges associated with eradication of biofilms. This narrative review focuses on biofilm-associated infections caused by S. aureus, the impact of environmental conditions on biofilm formation, interactions inside biofilm communities, and the clinical challenges that they present. Conclusively, potential solutions, novel treatment strategies, combination therapies, and reported alternatives are discussed.

Stress Response of Vibrio parahaemolyticus and Listeria monocytogenes Biofilms to Different Modified Atmospheres

The sessile biofilms of Vibrio parahaemolyticus and Listeria monocytogenes have increasingly become a critical threat in seafood safety. This study aimed to evaluate the effects of modified atmospheres on the formation ability of V. parahaemolyticus and L. monocytogenes biofilms. The stress responses of bacterial biofilm formation to modified atmospheres including anaerobiosis (20% carbon dioxide, 80% nitrogen), micro-aerobiosis (20% oxygen, 80% nitrogen), and aerobiosis (60% oxygen, 40% nitrogen) were illuminated by determining the live cells, chemical composition analysis, textural parameter changes, expression of regulatory genes, etc. Results showed that the biofilm formation ability of V. parahaemolyticus was efficiently decreased, supported by the fact that the modified atmospheres significantly reduced the key chemical composition [extracellular DNA (eDNA) and extracellular proteins] of the extracellular polymeric substance (EPS) and negatively altered the textural parameters (biovolume, thickness, and bio-roughness) of biofilms during the physiological conversion from anaerobiosis to aerobiosis, while the modified atmosphere treatment increased the key chemical composition of EPS and the textural parameters of L. monocytogenes biofilms from anaerobiosis to aerobiosis. Meanwhile, the expression of biofilm formation genes (luxS, aphA, mshA, oxyR, and opaR), EPS production genes (cpsA, cpsC, and cpsR), and virulence genes (vopS, vopD1, vcrD1, vopP2β, and vcrD2β) of V. parahaemolyticus was downregulated. For the L. monocytogenes cells, the expression of biofilm formation genes (flgA, flgU, and degU), EPS production genes (Imo2554, Imo2504, inlA, rmlB), and virulence genes (vopS, vopD1, vcrD1, vopP2β, and vcrD2β) was upregulated during the physiological conversion. All these results indicated that the modified atmospheres possessed significantly different regulation on the biofilm formation of Gram-negative V. parahaemolyticus and Gram-positive L. monocytogenes, which will provide a novel insight to unlock the efficient control of Gram-negative and Gram-positive bacteria in modified-atmosphere packaged food.

Prevalence and antibiotic resistance profiles of Staphylococcus sp. isolated from food, food contact surfaces and food handlers in a Moroccan hospital kitchen

Food poisoning risk related to the consumption of contaminated food with known foodborne pathogens or antibiotic-resistant bacteria is currently a serious threat for public health. Thus, pathogenic methicillin-resistant Staphylococcus strains are considered as one of the major cause of foodborne diseases in hospitals. The present study aims to determine the prevalence and the antibiotic resistance patterns of Staphylococcus in various types of hospital food samples, work surfaces and its carriage by food handlers. A total of 608 collected samples including 300 food samples, 238 food contact surfaces and 70 nasal and hand samples were tested. The identified Staphylococcus and their antibiotic resistance patterns were analysed using the agar disk-diffusion and PCR method was used for mecA resistance gene amplification. The prevalence of S. aureus and the coagulase-negative staphylococci were 17·33 and 23·33%, respectively. The antibiotic resistance reached 100% towards oxacillin and Penicillin G for both S. aureus and CoNs. The mecA gene was detected in 5·71% (4/70) and 7·69% (4/52) of S. aureus and CoNs strains, respectively. The outcome of this study enlightens isolation of MRSA strains and resistant CoNs from food, food contact surfaces and food handlers. The presence of this resistant species in this critical setting, where products were intended to vulnerable and immunocompromised patients, represents a serious threat to this community. It can be a source of nosocomial infection and more precautions must be taken to prevent staphylococci food contamination mainly in hospitals. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study describing the antibiotic resistance patterns of Staphylococcus aureus and coagulase-negative Staphylococcus isolated from hospital food, food contact surfaces and food handlers samples in a Moroccan hospital kitchen. High levels of multi-resistance were reported. The alarming outcome of this study emphasizes the crucial need of implementing an approach to fight multidrug-resistant staphylococci mainly in healthcare settings, where the community have already compromised health issues.

Environmental factors modulate biofilm formation by Staphylococcus aureus

Biofilm formation on indwelling medical devices represents an exclusive evasion mechanism for many pathogenic bacteria to establish chronic infections. Staphylococcus aureus is one of the major bacterial pathogens that are able to induce both animal and human infections. The continued emergence of multiple drug-resistant S. aureus, especially methicillin-resistant S. aureus, is problematic due to limited treatment options. Biofilm formation by S. aureus complicates the treatment of methicillin-resistant S. aureus infections. Therefore, elucidating the mechanisms of biofilm formation in this pathogen is important for the development of alternative therapeutic strategies. Various environmental and genetic factors contribute to biofilm formation. In this review, we address the environmental factors and discuss how they affect biofilm formation by S. aureus.

Adhesion and biofilm formation by Staphylococcus aureus clinical isolates under conditions relevant to the host: relationship with macrolide resistance and clonal lineages

PURPOSE

Staphylococcus aureus isolates, collected from various clinical samples, were analysed to evaluate the contribution of the genetic background of both erythromycin-resistant (ERSA) and -susceptible (ESSA) S. aureus strains to biofilm formation.

METHODS

A total of 66 ESSA and 43 ERSA clinical isolates were studied for adhesiveness and biofilm formation under different atmospheres. All isolates were evaluated for phenotypic and genotypic macrolide resistance, and for clonal relatedness by pulsed-field gel electrophoresis (PFGE), and by spa typing on representative isolates.

RESULTS

A high genetic heterogeneity was encountered, although 10 major PFGE types accounted for 86 % with a few small spatially and temporally related clusters. Overall, biofilm formation under anoxia was significantly lower than under oxic and micro-aerophilic atmospheres. Biofilm formation by ESSA was significantly higher compared to ERSA under oxic and micro-aerophilic conditions. Adhesiveness to plastic was significantly higher among respiratory tract infection isolates under micro-aerophilic conditions, while surgical site infection isolates formed significantly higher biomass of biofilm under oxic and micro-aerophilic atmospheres compared to anoxia. Pulsotype 2 and 4 strains formed significantly higher biofilm biomass than pulsotype 1, with strains belonging to CC8 forming significantly more compared to those belonging to CC5, under both oxic and micro-aerophilic atmospheres.

CONCLUSIONS

S. aureus biofilm formation appears to be more efficient in ESSA than ERSA, associated with specific S. aureus lineages, mainly CC8 and CC15, and affected by atmosphere. Further studies investigating the relationship between antibiotic resistance and biofilm formation could prove useful in the development of new strategies for the management of S. aureus infections.

Characterization of Biofilms Formed by Foodborne Methicillin-Resistant Staphylococcus aureus

The objective of this study was to evaluate the capacity of 49 methicillin resistant Staphylococcus aureus (MRSA) from foods of animal origin (42 from dairy products and 7 from meat and meat products) to form biofilms. Overall, a higher biofilm biomass was observed for those MRSA strains harboring SCCmec type IV, while 8 MRSA strains (5 from dairy products and 3 from meat and meat products) were classified as strong biofilm formers in standard Tryptic Soy Broth medium. When a prolonged incubation period (48 h) was applied for those 8 MRSA strains, an increased biofilm biomass accumulation was observed during the time course, whereas the number of viable cells within the biofilms decreased as the biomass increased. The capacity of biofilm production correlated pretty well between the experiments using polystyrene microtiter plates and stainless steel micro-well plates, and significant higher values were observed in stainless steel when glucose was added to TSB during the enrichment. Biofilms were further characterized by confocal laser scanning microscope (CLSM), confirming that proteins and α-polysaccharides were the predominant components inside the extracellular polymeric matrix of biofilms formed by MRSA strains. In conclusion, our results confirm that MRSA isolates from foods of animal origin have significant capacity for forming biofilms with a high protein content, which can play a key role for the successful dissemination of MRSA lineages via food. Knowledge of the capacity of MRSA strains to produce biofilms, as well as characterization of the main MRSA biofilms matrix components, can help both to counteract the mechanisms involved in biofilm formation and resistance and to define more rational control strategies by using tailor-made cleaning agents.

Bone Environment Influences Irreversible Adhesion of a Methicillin-Susceptible Staphylococcus aureus Strain

Prosthesis and joint infections are an important threat in public health, especially due to the development of bacterial biofilms and their high resistance to antimicrobials. Biofilm-associated infections increase mortality and morbidity rates as well as hospitalization costs. Prevention is the best strategy for this serious issue, so there is an urgent need to understand the signals that could induce irreversible bacterial adhesion on a prosthesis. In this context, we investigated the influence of the bone environment on surface adhesion by a methicillin-susceptible Staphylococcus aureus strain. Using static and dynamic biofilm models, we tested various bone environment factors and showed that the presence of Mg²⁺, lack of oxygen, and starvation each increased bacterial adhesion. It was observed that human osteoblast-like cell culture supernatants, which contain secreted components that would be found in the bone environment, increased bacterial adhesion capacity by 2-fold (p = 0.015) compared to the medium control. Moreover, supernatants from osteoblast-like cells stimulated with TNF-α to mimic inflammatory conditions increased bacterial adhesion by almost 5-fold (p = 0.003) without impacting on the overall biomass. Interestingly, the effect of osteoblast-like cell supernatants on bacterial adhesion could be counteracted by the activity of synthetic antibiofilm peptides. Overall, the results of this study demonstrate that factors within the bone environment and products of osteoblast-like cells directly influence S. aureus adhesion and could contribute to biofilm initiation on bone and/or prosthetics implants.

Assessment of in vivo versus in vitro biofilm formation of clinical methicillin-resistant Staphylococcus aureus isolates from endotracheal tubes

Our aim was to demonstrate that biofilm formation in a clinical strain of methicillin-resistant Staphylococcus aureus (MRSA) can be enhanced by environment exposure in an endotracheal tube (ETT) and to determine how it is affected by systemic treatment and atmospheric conditions. Second, we aimed to assess biofilm production dynamics after extubation. We prospectively analyzed 70 ETT samples obtained from pigs randomized to be untreated (controls, n = 20), or treated with vancomycin (n = 32) or linezolid (n = 18). A clinical MRSA strain (MRSA-in) was inoculated in pigs to create a pneumonia model, before treating with antibiotics. Tracheally intubated pigs with MRSA severe pneumonia, were mechanically ventilated for 69 ± 16 hours. All MRSA isolates retrieved from ETTs (ETT-MRSA) were tested for their in vitro biofilm production by microtiter plate assay. In vitro biofilm production of MRSA isolates was sequentially studied over the next 8 days post-extubation to assess biofilm capability dynamics over time. All experiments were performed under ambient air (O₂) or ambient air supplemented with 5% CO₂. We collected 52 ETT-MRSA isolates (placebo N = 19, linezolid N = 11, and vancomycin N = 22) that were clonally identical to the MRSA-in. Among the ETT-MRSA isolates, biofilm production more than doubled after extubation in 40% and 50% under 5% CO₂ and O₂, respectively. Systemic antibiotic treatment during intubation did not affect this outcome. Under both atmospheric conditions, biofilm production for MRSA-in was at least doubled for 9 ETT-MRSA isolates, and assessment of these showed that biofilm production decreased progressively over a 4-day period after extubation. In conclusion, a weak biofilm producer MRSA strain significantly enhances its biofilm production within an ETT, but it is influenced by the ETT environment rather than by the systemic treatment used during intubation or by the atmospheric conditions used for bacterial growth.

The potential of bacteriophage cocktail in eliminating Methicillin-resistant Staphylococcus aureus biofilms in terms of different extracellular matrices expressed by PIA, ciaA-D and FnBPA genes

Background

This study assessed novel approach of using highly lytic phages against methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) biofilms with and without biofilm extracellular matrix- disrupting chemical.

Method

The resultant phage-based control was assessed in relation to the type of biofilm extracellular matrix namely, polysaccharide intercellular adhesion (PIA) or proteinacious fibronectin-binding protein A (FnBPA). The biofilms were formed in vitro by 24 h incubation of bacteria in 96 wells microtiter plates at room temperature. The formed biofilms were assessed by tissue culture plate (TCP). Moreover, the nature of the biofilm was assessed by scanning electron microscopy (SEM) and PCR assay for detecting PIA genes, ciaA-D and FnBPA genes.

Results

this study showed that applied phages with 0.08 % benezenthonium chloride, for PIA biofilms, and 0.06 % ethanol, for proteinacious FnBPA biofilms, exerted 100 % eradication for MSSA biofilms and about 78 % of MRSA biofilms. The phage-based control of biofilms with chemical adjuvant showed significantly higher efficiency than that without adjuvant (P < 0.05). Moreover, FnBPA biofilms were more common in MRSA than in MSSA while PIA biofilms were more common in MSSA than in MRSA. And the most resistant type of biofilms to phage-based control was FnBPA in MRSA where 50 % of biofilms were reduced but not eradicated completely.

Conclusions

It is concluded that PIA-disturbing agent and protein denaturing alcohol can increase the efficiency of attacking phages in accessing host cell walls and lysing them which in turn lead to much more efficient MRSA and MSSA biofilm treatment and prevention.

Effect of incubation atmosphere on the production and composition of staphylococcal biofilms

Staphylococcus aureus and Staphylococcus epidermidis are pathogenic bacteria that often cause invasive infections in humans. In this study, we characterized the composition and growth characteristics of staphylococcal biofilms under various incubation atmospheres. We assessed the effect of incubation atmosphere (aerobic, 5% CO2, anaerobic, and microaerobic) on the biofilm production capabilities of S. aureus strains isolated from healthy volunteers and from patients with catheter-related bloodstream infection. In addition, the composition of S. aureus and S. epidermidis biofilms was determined by assessment of biofilm degradation after treatment with DNase I, proteinase K, and dispersin B. The strains obtained from healthy volunteers and patients showed similar biofilm formation capabilities. Biofilms of S. aureus were rich in proteins when developed under ambient atmospheric conditions, 5% CO2, and microaerobic condition, whereas S. epidermidis biofilms contained large amounts of poly-β (1, 6)-N-acetyl-D-glucosamine when developed under ambient atmospheric conditions and microaerobic condition. The biofilm-producing capability of S. epidermidis was considerably higher than that of S. aureus under aerobic condition. Staphylococcal isolates obtained from healthy individuals and patients with catheter-related infections have similar biofilm-forming capabilities. Under microaerobic conditions, S. aureus and S. epidermidis form protein-rich and poly-β (1, 6)-N-acetyl-D-glucosamine-rich biofilms, respectively. These components may play an important role in the development of biofilms inside the body and may be the target molecules to prevent catheter-related infections caused by these organisms.

Anoxia inhibits biofilm development and modulates antibiotic activity

BACKGROUND

Many infections involve bacterial biofilms that are notoriously antibiotic resistant. Unfortunately, the mechanism for this resistance is unclear. We tested the effect of oxygen concentration on development of Staphylococcus aureus biofilms, and on the ability of gentamicin and vancomycin to inhibit biofilm development.

MATERIALS AND METHODS

To mimic catheter-associated biofilms, silastic coupons were inoculated with 10(7)S aureus and incubated either aerobically (∼21% O2) or anaerobically (10% CO2, 5% H2, 85% N2) for 16 h at 37°C with varying concentrations of gentamicin and vancomycin. Viable colony-forming units were quantified from sonicated biofilms, and the crystal violet assay quantified biofilm biomass. Metabolomic profiles probed biochemical differences between aerobic and anaerobic biofilms.

RESULTS

Control biofilms (no antibiotic) cultivated aerobically contained 8.1-8.6 log10S aureus. Anaerobiasis inhibited biofilm development, quantified by viable bacterial numbers and biomass (P < 0.05). Bactericidal concentrations of gentamicin inhibited biofilm development in normoxia but not anoxia, likely because bacterial uptake of gentamicin is oxygen dependent. The inhibitory effect of vancomycin was more uniform aerobically and anaerobically, although at high bactericidal concentrations, vancomycin effectiveness was decreased under anoxia. There were notable differences in the metabolomic profiles of biofilms cultivated under normoxia versus anoxia.

CONCLUSIONS

Compared with aerobic incubation, anaerobiasis resulted in decreased biofilm development, and metabolomics is a promising tool to identify key compounds involved in biofilm formation. The effectiveness of a specific antibiotic depended on its mode of action, as well as on the oxygen concentration in the environment.

Control of methicillin-resistant Staphylococcus aureus in planktonic form and biofilms: a biocidal efficacy study of nonthermal dielectric-barrier discharge plasma

BACKGROUND

Bacterial contamination of surfaces with methicillin-resistant Staphylococcus aureus (MRSA) is a serious problem in the hospital environment and is responsible for significant nosocomial infections. The pathogenic contaminants form biofilms, which are difficult to treat with routine biocides. Thus, a continuous search for novel disinfection methods is essential for effective infection control measures. This demonstration of a novel technique for the control of virulent pathogens in planktonic form as well as in established biofilms may provide a progressive alternative to standard methodology.

METHODS

We evaluated a novel technique of normal atmospheric nonthermal plasma known as floating-electrode dielectric-barrier discharge (FE-DBD) plasma against a control of planktonic and biofilm forms of Escherichia coli, S aureus, multidrug-resistant methicillin-resistant S aureus (MRSA) -95 (clinical isolate), -USA300, and -USA400, using widely accepted techniques such as colony count assay, LIVE/DEAD BacLight Bacterial Viability assay, and XTT (2,3-Bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) assay.

RESULTS

Exposure of free living planktonic forms of E coli, S aureus, and MRSA were rapidly inactivated by DBD plasma. Approximately 10(7) bacterial cells were completely (100%) killed, whereas 10(8) and 10(9) were reduced by approximately 90% to 95% and 40% to 45%, respectively, in less than 60 seconds (7.8 J/cm(2)) and completely disinfected in < or =120 seconds. In established biofilms, the susceptibility of MRSA USA400 was comparable with USA300 but less susceptible than MRSA95 (clinical isolate), S aureus, and E coli (P < .05) to FE-DBD plasma, and plasma was able to kill MRSA more than 60% within 15 seconds (1.95 J/cm(2)). The killing responses were plasma exposure-time dependent, and cell density dependent. The plasma was able disinfect surfaces in a less than 120 seconds.

CONCLUSION

Application of DBD plasma can be a valuable decontamination technique for the removal of planktonic and biofilm-embedded bacteria such as MRSA -USA 300, -USA 400, methicillin-sensitive S aureus (MSSA), and E coli, the more common hospital contaminants. Of interest, E coli was more resistant than S aureus phenotypes.