Significant Difference In Biofilm Formation Research Articles

Enhancing bactericidal activities of ciprofloxacin by targeting the trans-translation system that is involved in stress responses in Klebsiella pneumoniae.

Although the trans-translation system is a promising target for antcibiotic development, its antibacterial mechanism in Klebsiella pneumoniae (KP) is unclear. Considering that tmRNA was the core component of trans-translation, this study firstly investigated phenotypic changes caused by various environmental stresses in KP lacking trans-translation activities (tmRNA-deleted), and then aimed to evaluate antibacterial activities of the trans-translation-targeting antibiotic combination (tobramycin/ciprofloxacin) in clinical KP isolates based on inhibition activities of aminoglycosides against trans-translation. We found that the tmRNA-deleted strain P4325/ΔssrA was significantly more susceptible than the wild-type KP strain P4325 under environments with hypertonicity (0.5 and 1M NaCl), hydrogen peroxide (40mM), and UV irradiation. No significant differences in biofilm formation and survivals under human serum were observed between P4325/ΔssrA and P4325. tmRNA deletion caused twofold lower MIC values for aminoglycosides. As for the membrane permeability, tmRNA deletion increased ethidium bromide (EtBr) uptake of KP in the presence or absence of verapamil and carbonyl cyanide-m-chlorophenylhydrazone (CCCP), decreased EtBr uptake in presence of reserpine in P4325/ΔssrA, and reduced EtBr efflux in P4325/ΔssrA in the presence of CCCP. The time-kill curve and in vitro experiments revealed significant bactericidal activities of the tmRNA-targeting aminoglycoside-based antibiotic combination (tobramycin/ciprofloxacin). Thus, the corresponding tmRNA-targeting antibiotic combinations (aminoglycoside-based) might be effective and promising treatment options against multi-drug resistant KP.

Genotypic characterization of bacterial isolates causing urinary tract infections among adults at Kiambu Level 5 Hospital, Kenya: selected extended-spectrum β-lactamase genes and biofilm formation.

The menace of antimicrobial resistance affecting public health is rising globally. Many pathogenic bacteria use mechanisms such as mutations and biofilm formation, significantly reducing the efficacy of antimicrobial agents. In this cross-sectional study, we aimed to determine the prevalence of selected extended-spectrum β-lactamase (ESβL) genes and analyse the biofilm formation abilities of the isolated bacteria causing urinary tract infection among adult patients seeking Medicare at Kiambu Level 5 Hospital, Kenya. The double-disc synergy test was used for phenotypic identification of ESβL-producing isolates, while microtitre plate assays with some modifications were used for the biofilm formation test. Ten isolates were bioassayed for ESβL genes out of 57 bacterial isolates obtained from urine samples. This study found the bla TEM genes to be the most prevalent ESβL type [10/10 (100 %)], followed by blaOXA and blaSHV genes at 4/10 (40 %) and 3/10 (30 %), respectively. In addition, co-carriage of blaTEM and blaSHV was 50 % lower than that of blaTEM+bla OXA genes at 66.7 % among Escherichia coli isolates studied. Biofilm formation was positive in 36/57 (63.2 %) of the isolates tested, with most being Gram-negative [25/36 (69.4 %)]. Escherichia coli [15/36 (41.7 %)], Klebsiella species [7/36 (19.4 %)] and Staphylococcus aureus [7/36 (19.4 %)] were the dominant biofilm formers. However, there was no significant difference in biofilm formation among all tested isolates, with all isolates recording P-values >0.05. In light of these findings, biofilm formation potential coupled with antimicrobial resistance genes in urinary tract infection isolates may lead to difficult-to-treat infections.

Influence of the orthodontic bonding procedure on biofilm formation.

In orthodontics, white spot lesions are a persistent and widespread problem caused by the demineralization of buccal tooth surfaces around bonded brackets. The remaining adhesive around the brackets leads to surface roughness, which might contribute to demineralization. The present in vitro study aimed to compare a conventional and a modern adhesive system (APC Flash-Free technology) for orthodontic brackets with regard to the adhesion of Streptococcus sobrinus, a leading caries pathogen. This in vitro study included 20 premolar teeth and compared 10 APC Flash-Free adhesive-coated ceramic brackets (FF)with 10 conventionally bonded (CB) ceramic clarity brackets. Specimens were incubated in an S. sobrinus suspension for 3 h. To evaluate the bacterial formation, samples were analysed with a scanning electron microscope (SEM). Imaging software was used to quantify and statistically compare percentage values of colonization (PVC) in both groups' adhesion and transition areas. We found a significant difference in biofilm formation between the groups for the adhesive and transition areas. PVC in the adhesive area was approximately 10.3-fold greater for the CB group compared with the FF group (median: 3.2 vs 0.31; P < 0.0001). For the transition area, median PVC was approximately 2.4-fold greater for the CB group compared with the FF group (median: 53.17 vs 22.11; P < 0.01). There was a significantly lower level of S. sobrinus formation around the FF bracket system than there was surrounding the conventionally bonded group. This study suggests that the FF adhesive bracket system can help reduce the occurrence of bacterial growth around orthodontic brackets.

PilA Gene Contributes to Virulence, Motility, Biofilm Formation, and Interspecific Competition of Bacteria in Acidovorax citrulli.

Acidovorax citrulli, the causative agent of bacterial fruit blotch, can be divided into two main groups based on factors such as pathogenicity and host species preference. PilA is an important structural and functional component of type IV pili (T4P). Previous studies have found significant differences in pilA DNA sequences between group I and group II strains of A. citrulli. In this study, we characterized pilA in the group I strain pslb65 and the group II strain Aac5. pilA mutants, complementation strains, and cross-complementation strains were generated, and their biological phenotypes were analyzed to identify functional differences between pilA in the two groups. pilA deletion mutants (pslb65-ΔpilA and Aac5-ΔpilA) showed significantly reduced pathogenicity compared with the wild-type (WT) strains; pslb65-ΔpilA also completely lost twitching motility, whereas Aac5-ΔpilA only partially lost motility. In King's B medium, there were no significant differences in biofilm formation between pslb65-ΔpilA and WT pslb65, but Aac5-ΔpilA showed significantly reduced biofilm formation compared to WT Aac5. In M9 minimal medium, both mutants showed significantly lower biofilm formation compared to the corresponding WT strains, although biofilm formation was recovered in the complementation strains. The biofilm formation capacity was somewhat recovered in the cross-complementation strains but remained significantly lower than in the WT strains. The interspecies competitive abilities of pslb65-ΔpilA and Aac5-ΔpilA were significantly lower than in the WT strains; Aac5-ΔpilA was more strongly competitive than pslb65-ΔpilA, and the complementation strains recovered competitiveness to WT levels. Furthermore, the cross-complementation strains showed stronger competitive abilities than the corresponding WT strains. The relative expression levels of genes related to T4P and the type VI secretion system were then assessed in the pilA mutants via quantitative PCR. The results showed significant differences in the relative expression levels of multiple genes in pslb65-ΔpilA and Aac5-ΔpilA compared to the corresponding WT stains. This indicated the presence of specific differences in pilA function between the two A. citrulli groups, but the regulatory mechanisms involved require further study.

Effects of pH, sodium chloride, and temperature on the growth of Listeria monocytogenes biofilms

AbstractListeria monocytogenes is able to form biofilms on food contact surfaces. Effectiveness of salt concentration, pH, and temperature on the formation of L. monocytogenes biofilms was evaluated individually and in combinations using microtiter plate assay by measuring the optical density. The tested strains differed in their biofilm formation (low, moderate, and strong) ability. At 37 °C, decreasing amounts of biofilms was observed in almost all L. monocytogenes strains when the NaCl concentration increased from 0.05 to 15%, but all strains were able to form biofilm even at 1 °C. There was no significant difference in biofilm formation between pH 4, 5, and 6, except for some strains. When stress conditions were tested in combination, the addition of 15% NaCl significantly inhibited the growth of L. monocytogenes at 1 °C and 4 °C, and the weak biofilm-forming strains were less sensitive to the temperature and to NaCl treatments than the strong biofilm-forming strains. These results enhance our knowledge of the application of NaCl, temperature, and pH stresses in the food industry and provide basis to develop new strategies for control of biofilm formation of this pathogen.

Clonal Spreading of ST42 Staphylococcus haemolyticus Strains Occurs Possibly Due to fusB and tetK Resistant Genes and Capsule-Related Genes.

Multi-drug resistant Staphylococcus haemolyticus is a frequent nosocomial invasive bacteremia pathogen in hospitals. Our previous analysis showed one of the predominant strains, ST42 originated from ST3, had only one multilocus sequence typing (MLST) variation among seven loci in SH1431; yet no significant differences in biofilm formation observed between ST42 and ST3, suggesting that other factors influence clonal lineage change. Whole genome sequencing was conducted on two isolates from ST42 and ST3 to find phenotypic and genotypic variations, and these variations were further validated in 140 clinical isolates. The fusidic acid- and tetracycline-resistant genes (fusB and tetK) were found only in CGMH-SH51 (ST42). Further investigation revealed consistent resistant genotypes in all isolates, with 46% and 70% of ST42 containing fusB and tetK, respectively. In contrast, only 23% and 4.2% ST3 contained these two genes, respectively. The phenotypic analysis also showed that ST42 isolates were highly resistant to fusidic acid (47%) and tetracycline (70%), compared with ST3 (23% and 4%, respectively). Along with drug-resistant genes, three capsule-related genes were found in higher percentage distributions in ST42 than in ST3 isolates. Our findings indicate that ST42 could become endemic in Taiwan, further constitutive surveillance is required to prevent the spread of this bacterium.

Differences in Candida Albicans hydrophobicity and biofilm formation between thermoplastic nylon and polyether-ether-ketone denture base materials

Polyetheretherketone (PEEK) and thermoplastics nylon are extensively composed as an alternative material for removable denture base. The primary difference between the two materials is associated with water absorption properties. The two materials interact with saliva and microorganisms during application in the oral cavity. Candida is predominantly reported in the cavity. The microorganism is distinguished by its hydrophobicity and ability to form biofilms. The objective of this study was to determine the differences between thermoplastic nylon and polyether-ether-ketone as removable denture materials in terms of hydrophobicity and Candida albicans biofilms. It is a laboratory experiment using 20 5 x 2 mm samples for the hydrophobicity test and Candida albicans biofilm. The hydrophobicity test was performed by determining the contact angle with a Goniometer and the WinDrop++ software. The biofilm test samples were divided into 4 groups, encompassing PEG 5% (negative control), PEEK treatment, thermoplastics nylon, and 0.12% chlorhexidine (control positive). The microdilution method was employed to examine biofilm formation. The results of the study were interpreted, and the data were analyzed by employing the t test. The research discovered significant differences in biofilm formation, large contact angle on PEEK and thermoplastics nylon (p &lt; 0.05). Biofilm formation on thermoplastics is significantly larger than PEEK (p &lt; 0.05). In conclusion, the contact angles of PEEK and thermoplastic nylon are incorporated in the partially wetted. Polyetheretherketone is involved in the non-producers of biofilms while thermoplastic nylon is categorized in of weak biofilm formers.

Biofilms as a microbial hazard in the food industry: A scoping review.

Biofilms pose a serious public health hazard with a significant economic impact on the food industry. The present scoping review is designed to analyse the literature published during 2001-2020 on biofilm formation of microbes, their detection methods, and association with antimicrobial resistance (if any). The peer-reviewed articles retrieved from 04 electronic databases were assessed using PRISMA-ScR guidelines. From the 978 preliminary search results, a total of 88 publications were included in the study. On analysis, the commonly isolated pathogens were Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., Escherichia coli, Bacillus spp., Vibrio spp., Campylobacter jejuni and Clostridium perfringens. The biofilm-forming ability of microbes was found to be influenced by various factors such as attachment surfaces, temperature, presence of other species, nutrient availability etc. A total of 18 studies characterized the biofilm-forming genes, particularly for S. aureus, Salmonella spp., and E. coli. In most studies, polystyrene plate and/or stainless-steel coupons were used for biofilm formation, and the detection was carried out by crystal violet assays and/or by plate counting method. The strain-specific significant differences in biofilm formation were observed in many studies, and few studies carried out analysis of multi-species biofilms. The association between biofilm formation and antimicrobial resistance was not clearly defined. Further, viable but non-culturable form of the foodborne pathogens is posing an unseen (by conventional cultivation techniques) but potent threat to the food safety. The present review recommends the need for carrying out systematic surveys and risk analysis of biofilms in food chain to highlight the evidence-based public health concerns, especially in regions where microbiological food hazards are quite prevalent.

P373 Does biofilm forming capacity of Candida tropicalis vary with echinocandin susceptibility?

Poster session 3, September 23, 2022, 12:30 PM - 1:30 PMObjectives Candida tropicalis is a common cause of nosocomial candidemia and candiduria. The role of biofilm formation in virulence and antimicrobial resistance in C. tropicalis remains under-investigated. We aimed to evaluate the biofilm-forming capacity of C. tropicalis isolates exhibiting resistance, borderline resistance, and sensitivity to echinocandins.MethodsThe echinocandin resistant, borderline resistant, and susceptible isolates of C. tropicalis were collected based on their minimum inhibitory concentration (MIC) values according to Clinical and Laboratory Standard Institute (CLSI) broth microdilution guidelines. The isolates were subjected to FKS1 gene sequencing. To estimate biofilm production, echinocandin resistant (n = 2), borderline resistant (n = 5), and susceptible isolates (n = 3) were seeded at the cell concentration of 1 × 10⁶ cells/mL in RPMI-1640 with 0.165 M MOPS in polystyrene 96-well microtiter plates and incubated for 24 and 48 h at 37°C. The biofilm was quantified by crystal violet/safranin-based spectrophotometric method and XTT (2,3-Bis-(2-Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide) reduction assay. Statistical analysis was performed using one-way ANOVA with Bonferroni's post-hoc test for multiple comparisons among the groups.ResultsFKS1 sequencing analysis revealed S654P mutation in HS1 in both resistant isolates while isolates exhibiting borderline MIC to echinocandins carried wild-type FKS1 gene. Biofilm formation in borderline echinocandin-resistant C. tropicalis isolates was significantly (P <.005) higher compared with resistant and susceptible isolates. However, no significant difference in biofilm formation was noted among resistant and susceptible isolates.ConclusionThis study suggests differential biofilm-formation capacity among C. tropicalis isolates with reduced susceptibility to echinocandins. However, this warrants further studies before any definitive inference can be made.

Biofilm Formation on Central Venous Catheters: A Pilot Study

IntroductionCentral line–associated bloodstream infection is a complication with serious consequences and biofilm development is thought to play a role. This study evaluated the impact of sterilization technique on central venous catheter (CVC) biofilm formation. Materials and methodsThis pilot study was conducted in the surgical intensive care unit of a tertiary care facility. All CVCs were inserted with chlorhexidine preparation (CHG). CHG-only CVCs were compared to the use of CHG with chlorhexidine gluconate–impregnated sponge (CHGIS). After removal, a punch biopsy of the CVC was taken at the noted skin level. Scanning electron microscopy identified the stage of biofilm. Confocal laser scanning microscopy with SYPRO stain confirmed the presence of glycocalyx and a volumetric analysis was completed. ResultsTwenty four CVCs were collected. Indications for line placement were similar, with 42% placed for sepsis in the CHGIS group and 33% in the CHG group. There were no positive line cultures or bacteremia and 2/12 CHGIS patients had candidemia. CHGIS lines were in place for a mean of 91 h, compared to 60 h with CHG alone (P = 0.19). The interior of CVCs had lower stage biofilms than the exterior and lacked stage 4 biofilms. Stage 4 biofilms were present externally on 50% of CVCs (8/12 CHG and 4/12 CHGIS). Stage 3 biofilms were present on 7/12 CHG and 6/12 CHGIS interior samples. Volume analysis found an increase in biofilm and glycocalyx in CHGIS compared to CHG samples. ConclusionsThis study identified biofilms on both surfaces of CVCs. No significant difference in biofilm formation was found based on a sterilization technique.

Changes in clinical periodontal parameters after removal of fixed orthodontic appliances

The placement of orthodontic appliances influences plaque growth and maturation. Significant differences in biofilm formation and periodontal reaction between different bracket types and between bonded teeth compared with control teeth have been reported, however, have reported significant attachment loss during orthodontic treatment.In patients with a history of periodontitis resulting in displaced teeth, possible orthodontic tooth movements include changes in alignment, space redistribution, and intrusion.To see the changes in clinical periodontal parameters after removal of fixed orthodontic appliancesAfter debonding of braket at dental clinic and before final polishing, probing depth (PD), plaque index (PI), gingival index (GI) and bleeding on probing (BOP) were assessed on the first molars and central incisors of both arches.Probing depth decreased in the right maxillary first molar. Plaque index and gingival index also got deceased. Bleeding on Probing reduced significantly.Buccal probing depth returned to &amp;#60; 3 mm in the first month and interproximal depth in the second month. The mean gingival index was 0.5 after 2 months. Bleeding on probing in half of the teeth was negative after the first month and in other half in the second month.

Effect of Surface Tooling Techniques of Medical Titanium Implants on Bacterial Biofilm Formation In Vitro.

The aim of this study was to assess the biofilm formation of Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli on titanium implants with CAD-CAM tooling techniques. Twenty specimens of titanium were studied: Titanium grade 2 tooled with a Planmeca CAD-CAM milling device (TiGrade 2), Ti6Al4V grade 5 as it comes from CAD-DMLS device (computer aided design-direct metal laser sintering device) (TiGrade 5), Ti6Al4V grade 23 as it comes from a CAD-CAM milling device (TiGrade 23), and CAD-DMLS TiGrade 5 polished with an abrasive disc (TiGrade 5 polished). Bacterial adhesion on the implants was completed with and without saliva treatment to mimic both extraoral and intraoral surgical methods of implant placement. Five specimens/implant types were used in the bacterial adhesion experiments. Autoclaved implant specimens were placed in petri plates and immersed in saliva solution for 30 min at room temperature and then washed 3× with 1× PBS. Bacterial suspensions of each strain were made and added to the specimens after saliva treatment. Biofilm was allowed to form for 24 h at 37 °C and the adhered bacteria was calculated. Tooling techniques had an insignificant effect on the bacterial adhesion by all the bacterial strains studied. However, there was a significant difference in biofilm formation between the saliva-treated and non-saliva-treated implants. Saliva contamination enhanced S. mutans, S. aureus, and E. faecalis adhesion in all material types studied. S. aureus was found to be the most adherent strain in the saliva-treated group, whereas E. coli was the most adherent strain in the non-saliva-treated group. In conclusion, CAD-CAM tooling techniques have little effect on bacterial adhesion. Saliva coating enhances the biofilm formation; therefore, saliva contamination of the implant must be minimized during implant placement. Further extensive studies are needed to evaluate the effects of surface treatments of the titanium implant on soft tissue response and to prevent the factors causing implant infection and failure.

No Correlation between Biofilm-Forming Capacity and Antibiotic Resistance in Environmental Staphylococcus spp.: In Vitro Results.

The production of biofilms is a critical factor in facilitating the survival of Staphylococcus spp. in vivo and in protecting against various environmental noxa. The possible relationship between the antibiotic-resistant phenotype and biofilm-forming capacity has raised considerable interest. The purpose of the study was to assess the interdependence between biofilm-forming capacity and the antibiotic-resistant phenotype in 299 Staphylococcus spp. (S. aureus n = 143, non-aureus staphylococci [NAS] n = 156) of environmental origin. Antimicrobial susceptibility testing and detection of methicillin resistance (MR) was performed. The capacity of isolates to produce biofilms was assessed using Congo red agar (CRA) plates and a crystal violet microtiter-plate-based (CV-MTP) method. MR was identified in 46.9% of S. aureus and 53.8% of NAS isolates (p > 0.05), with resistance to most commonly used drugs being significantly higher in MR isolates compared to methicillin-susceptible isolates. Resistance rates were highest for clindamycin (57.9%), erythromycin (52.2%) and trimethoprim-sulfamethoxazole (51.1%), while susceptibility was retained for most last-resort drugs. Based on the CRA plates, biofilm was produced by 30.8% of S. aureus and 44.9% of NAS (p = 0.014), while based on the CV-MTP method, 51.7% of S. aureus and 62.8% of NAS were identified as strong biofilm producers, respectively (mean OD570 values: S. aureus: 0.779±0.471 vs. NAS: 1.053±0.551; p < 0.001). No significant differences in biofilm formation were observed based on MR (susceptible: 0.824 ± 0.325 vs. resistant: 0.896 ± 0.367; p = 0.101). However, pronounced differences in biofilm formation were identified based on rifampicin susceptibility (S: 0.784 ± 0.281 vs. R: 1.239 ± 0.286; p = 0.011). The mechanistic understanding of the mechanisms Staphylococcus spp. use to withstand harsh environmental and in vivo conditions is crucial to appropriately address the therapy and eradication of these pathogens.

Silicon breast implants’ texture affecting bacterial biofilm formation

Introduction/Objective. The most important etiologic factors for both, capsular contracture (CC) and breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) is subclinical infection, defined as a response of an organism on presence of biofilm on the implant surface. The aim of this research was to examine the possibility of biofilm formation of four different bacteria (Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Ralstonia picketti) on three differently textured silicone breast implants (Siltex, Mentor, pore size 70?150 ?m; MESMORsensitive, Polytech, pore size 50?900 ?m; and SilkSurface, Motiva pores 13 ?m) in vitro. Methods. Samples of silicone breast implant capsules (sized 1 ? 1 cm) were divided into three groups according to texture. After sterilization, 30 samples in every group were contaminated with 100 ?l of examined bacterial broth, followed by incubation which led to biofilm formation. For testing the capability of biofilm formation, modified technique with microtitar plates described by Stepanovic? was used. Results. All four examined bacteria (Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Ralstonia picketti) form more biofilm on implants with pore sizes 50?900 ?m compared to implants with pore size 70?150 ?m and those with 13 ?m. Statistical significance was found in biofilm formation on implants with pores 70?150 ?m compared to implants with pores 13 ?m. The only exception was P. aeuruginosa which did not show significant difference in biofilm formation on implants 70?150 ?m and 13 ?m. Conclusion. Silicone breast implants with micro and nanotexture should be chosen in order to prevent biofilm formation and possible consequent complications.

Evaluation of biofilm formation on different clear orthodontic retainer materials.

Aim:To assess the chemical composition and oral biofilm formation on different types of commercially available clear orthodontic retainer materials (CORM).Materials and Methods:Four types of CORM commercially available were used (Clear advantage series I (CAS1), Clear advantage series II (CAS2), Endure (ES), and CENTRI FORM-clear rigid material (CFCRM)). Circular samples (12 mm diameter) of each CORM were prepared for (n = 40). Unstimulated saliva from twenty volunteers was collected. Fourier Transformation Infrared Spectroscopy (FTIR) was used for the evaluation of the chemical composition of CORM. For the quantitative assessment of oral biofilm formation, samples of each CORM were incubated for twenty-four hours, and crystal violet assay (CVA) was utilized. The degree of absorbance was measured using a spectrophotometer at 570 nm. For qualitative evaluation of oral formation, the samples of each CORM were incubated for 24 hours, and viable biofilm cells stained by acridine orange were examined under a fluorescent microscope.Results:FTIR findings showed that CAS2 was made of polypropylene and ES is made of polyvinyl chloride, while others were made of co-polyester. CVA results confirmed that CAS2 showed the lowest biofilm formation, which differs significantly compared to CAS1, CFCRM, and ES. No significant difference in biofilm formation was detected between CAS1, CFCRM, and ES. Viable biofilm cells staining by acridine orange showed that CAS2 demonstrated smaller microcolonies of viable biofilm cells compared with CAS1, CFCRM, and ES, which confirmed the result obtained by CVA.Conclusions:CAS2 showed anti-microbial activities with a decrease the in vitro biofilm formation, which may be related to its chemical composition.

Increased biofilm formation by Staphylococcus aureus clinical isolates on surfaces covered with plasma proteins.

Introduction. Biofilm formation is a major virulence factor associated with Staphylococcus aureus infections. However, the influence of plasma proteins on biofilm formation of clinical isolates in vitro remains unclear.Hypotheses. We hypothesized that coating surfaces with plasma proteins might induce biofilm formation by S. aureus of different clonal lineages.Aim. To evaluate biofilm production by clinical S. aureus isolates of different clonal lineages isolated in Rio de Janeiro hospitals and investigated the presence of biofilm-associated genes.Methodology. This study assessed biofilm production of 60 S. aureus isolates in polystyrene microtitre plates with and without fibrinogen or fibronectin. The biochemical composition of the biofilm matrices was determined and the biofilm formation on fibrinogen-coated surfaces was also evaluated by confocal laser scanning microscopy. The presence of biofilm-related genes was detected by PCR, and the typing and functionality of agr operon was also evaluated.Results. Most of the isolates (45 %) were weak biofilm producers or non-producers. However, most of them presented a significant increase in biofilm production on plates covered with plasma proteins. There was no significant difference in biofilm formation between methicillin-resistant and -susceptible S. aureus isolates, or between different clonal lineages, except for ST30-IV (weak producers) and ST239-III (strong producers). The fnbB gene was associated with higher biofilm production.Conclusion. An increase in biofilm production in the presence of plasma proteins highlights the importance of investigating biofilm formation by S. aureus clinical isolates under different conditions since this virulence factor contributes to persistent infections and increased resistance to antimicrobials.

The effect of ligation methods on biofilm formation in patients undergoing multi-bracketed fixed orthodontic therapy - A systematic review.

Many modifications to fixed orthodontic appliances have been introduced to manage biofilm formation. The aim of this review was to investigate elastomeric ligation in comparison with stainless steel ligation and self-ligation with regard to microbiological and clinical indicators of biofilm formation in patients wearing multi-bracketed fixed orthodontic appliances. The MEDLINE and the EMBASE databases were searched up to February 2021 and supplemented by additional manual searches of bibliographies. Parallel-group and split-mouth randomized controlled trials (RCTs) comparing different ligation methods were identified. The Cochrane Risk of Bias-2 tool was applied to assess the quality of evidence. A total of 11 RCTs were included in this review. Nine RCTs compared self-ligation and elastomeric ligation; two compared elastomeric ligation and stainless steel ligation. The included studies had either some concerns or were at a high risk of bias. Qualitative assessment of the studies identified that there were no significant differences in biofilm formation between elastomeric ligation and self-ligation, but that stainless steel ligation was less susceptible to biofilm formation than elastomeric ligation. There were no significant differences between self-ligation and elastomeric ligation for biofilm formation in patients wearing multi-bracketed fixed orthodontic appliances. Stainless steel ligation may accumulate less biofilm than elastomeric ligation; however, the clinical significance of the difference could not be evaluated. Further high-quality studies are required in order to determine which ligation method is better for managing biofilm formation in patients wearing multi-bracketed fixed orthodontic appliances.

Biofilm formation, icaABCD genes and agr genotyping of Staphylococcus aureus from fish and ground beef

AbstractA total of 46 Staphylococcus aureus isolates from fish and ground beef were tested for the agr types, icaABCD genes, and biofilm formation at 12, 25 and 37 °C by the microtiter plate and the MTT assays. All isolates were positive for the icaABD genes, while 97.8% were positive for the icaC. All isolates produced biofilms at 37 and 25 °C, but 93.5% of them were also biofilm producers at 12 °C. There was no significant difference in biofilm formation between 25 and 37 °C using the crystal violet assay (P &gt; 0.05). However, statistically significant differences were detected between 12 and 25 °C as well as 12 and 37 °C (P &lt; 0.05). All isolates were significantly different in biofilm production by the MTT assay at all tested temperatures. Furthermore, a relationship between the presence of the icaABCD genes and biofilm formation was observed. The agr type I was the most prevalent (54.4%) among the isolates, followed by agr type II (41.3%) and agr type III (9.6%). In this study, the S. aureus isolates exhibited biofilm formation ability responsible for persistence of bacteria in foods, which may lead to food spoilage and human health problems.

Temperature Effect on Listeria Monocytogenes Planktonic Growth and Biofilm-Forming Ability

Listeria Monocytogenes is an important foodborne pathogen with the capacity to grow at low temperatures and the ability to form biofilms. These features are particularly significant to food business operators producing readyto-eat foods with a long refrigerated shelf-life not undergoing any listericidal treatment before consumption. Objectives: This work aims to assess the temperature effect on L. monocytogenes growth in planktonic suspension and in mono-species biofilms. Methods and results: Isothermal planktonic growth at 12o C and 37o C was assayed using viable cell counts and optical density measurements that revealed a strong positive correlation, confirming the reliability of combining both methods to estimate L. monocytogenes concentration. Experimental data were then fitted to Baranyi and Roberts primary predictive model and the estimated growth parameters confirmed that μmax at 37o C (0.375 ± 0.072 log Cfu/ ml/h) was higher than at 120 C (0.054 ± 0.001 log Cfu/ml/h), with identical L. monocytogenes final concentrations which emphasizes its ability to grow at refrigerated temperatures. Experimental results from the isothermal growth assay and ComBase Predictor growth model were similar, with slightly higher estimated μmax (37o C: 0.480 log Cfu/ml/h; 12o C: 0.068 log Cfu/ml/h) in the predictor growth model. The studied strains demonstrated biofilm-forming ability at 12o C, 20o C and 300 C after 5 days of growth. No significant differences in biofilm formation at different temperatures were detected considering viable cell counts values, but when using crystal violet staining optical density results significant differences were found, with the highest formation occurring at 30ºC. A positive strong correlation was found between viable cell counts and crystal violet staining optical density results. In fact, both methods complement each other, because while viable cell counts measures viable cells, crystal violet staining optical density considers total biomass (viable and non-viable cells and extracellular matrix components). Nevertheless, in this work all L. monocytogenes strains revealed to be weak biofilm producers. Conclusion: Overall, this studys results contribute with important initial information on L. monocytogenes growth and biofilm formation to further assist predictive growth modeling in food matrices and environments, also enabling subsequent quantitative microbial risk assessment, to improve pathogen’s control.

Mutations at Novel Sites in pmrA/B and lpxA/D Genes and Absence of Reduced Fitness in Colistin-Resistant Acinetobacter baumannii from a Tertiary Care Hospital, India.

Background: Colistin resistance in Acinetobacter baumannii, the last resort drug for serious infections, is emerging worldwide. There has been paucity of data on this aspect from India, which is one of the largest producers of colistin. We studied colistin resistance in A. baumannii and characterized the isolates with respect to resistance mechanisms and virulence. Methods: A total of 365 A. baumannii isolates were studied. Antimicrobial susceptibility testing was performed as per standards. Colistin resistance mechanisms were studied by mutation detection in pmrA/B and lpxA/C/D genes, phenotypic loss of lipopolysaccharide, presence of mcr1-5 genes, and carbonyl cyanide 3-chlorophenylhydrazone (CCCP) effects. Biofilm formation, desiccation survival, and growth kinetics were studied and statistically analyzed for colistin-resistant and colistin-susceptible isolates. Results: All the colistin-resistant isolates (9, 2.5%) showed multiple mutations at novel sites in pmrA/B and/or lpxA/D genes with reversion of resistance with CCCP. Majority of these isolates (6, 66.6%) were from patients without prior colistin therapy. All received prior carbapenems. The resistant isolates demonstrated no significant difference in biofilm formation and desiccation survival but were slow growers. Conclusion: Mutations in pmrA/B and/or lpxA/D genes were the main resistance mechanism in these colistin-resistant isolates that showed no reduction in fitness.