High vancomycin resistance among biofilms produced by Staphylococcus species isolated from central venous catheters

Staphylococcus capitis: insights into epidemiology, virulence, and antimicrobial resistance of a clinically relevant bacterial species

SUMMARYStaphylococcus capitis is divided into two subspecies, S. capitis subsp. ureolyticus (renamed urealyticus in 1992; ATCC 49326) and S. capitis subsp. capitis (ATCC 27840), and fits with the archetype of clinically relevant coagulase-negative staphylococci (CoNS). S. capitis is a commensal bacterium of the skin in humans, which must be considered an opportunistic pathogen of interest particularly as soon as it is identified in a clinically relevant specimen from an immunocompromised patient. Several studies have highlighted the potential determinants underlying S. capitis pathogenicity, resistance profiles, and virulence factors. In addition, mobile genetic element acquisitions and mutations contribute to S. capitis genome adaptation to its environment. Over the past decades, antibiotic resistance has been identified for S. capitis in almost all the families of the currently available antibiotics and is related to the emergence of multidrug-resistant clones of high clinical significance. The present review summarizes the current knowledge concerning the taxonomic position of S. capitis among staphylococci, the involvement of this species in human colonization and diseases, the virulence factors supporting its pathogenicity, and the phenotypic and genomic antimicrobial resistance profiles of this species.

Effects of Vancomycin Subtherapeutic Concentration on Staphylococcus aureus Isolated from Hemodialysis Patients with Low Serum Trough Concentrations

Blood bactericidal activity and antimicrobial therapy are crucial against catheter-related infection in patients undergoing hemodialysis (HD). It is well-known that catheters colonized by biofilm-producing bacteria are a risk factor for bacteremia in HD-patients. Methicillin-resistant S. aureus bacteremia in HD-patients justify the use of vancomycin as empiric therapy. The recommended vancomycin target for therapeutic efficacy is a minimum serum concentration of 10 µg mL-1 to avoid resistance. However, subtherapeutic concentrations of vancomycin have frequently occurred in HD-patients. Thus, we aim to investigate the effect of subtherapeutic vancomycin concentration on S. aureus growth, susceptibility to antimicrobials, resistance to whole blood activity, and biofilm formation. Seventeen S. aureus strains isolated from bacteremia in HD-patients and two reference strains were exposed to a vancomycin-gradient (0-10 µg mL-1) for five consecutive days to mimic the dosing interval of vancomycin in HD-patients. After that, we observed the following: no effect on growth curve; decreased susceptibility to vancomycin and daptomycin; increased S. aureus survival to whole blood bactericidal action; and a strain-dependent biofilm production after drug exposure. In conclusion, our findings suggest that the subtherapeutic concentration of vancomycin decrease S. aureus susceptibility to vancomycin and daptomycin and increases its survival to whole blood bactericidal action.

A Narrative Review on the Role of Dalbavancin in the Treatment of Bone and Joint Infections

Bone and joint infections (BJI) require prolonged antimicrobial treatment, leading to lengthy hospitalizations, high costs, the risk of nosocomial infections, and the development of antimicrobial resistance. Dalbavancin is a novel semisynthetic lipoglycopeptide approved for the treatment of adults and children with acute bacterial skin and skin structure infections. This narrative review aims to summarize the characteristics of dalbavancin and the current scientific evidence regarding its clinical efficacy and safety in the treatment of BJI. A literature search until June 2023 was performed to identify all published research about the role of dalbavancin in the management of BJI. Due to its unique pharmacokinetics characterized by prolonged half-life, high bactericidal activity against most Gram-positive bacteria, a good safety profile, and high tissue penetration, dalbavancin can be a valuable alternative to the treatment of BJI. Clinical studies have shown its non-inferiority compared to conventional therapies in BJI, offering potent activity against key pathogens and an extended dosing interval that may shorten hospitalization. In conclusion, dalbavancin represents a promising treatment option for BJI with a favorable safety profile, but further research in both adults and particularly children, who are ideal candidates for long-acting antibiotics, is necessary to evaluate the role of dalbavancin in BJI.

Phenotypic detection of methicillin resistance, biofilm production, and inducible clindamycin resistance in Staphylococcus aureus clinical isolates in Kathmandu, Nepal

INTRODUCTION

Methicillin resistance, inducible clindamycin resistance (ICR), biofilm production, and increased minimum inhibitory concentration (MIC) of vancomycin in Staphylococcus aureus are major causes of antibiotic treatment failure and increased morbidity and mortality. The surveillance of such isolates and the study of their antimicrobial pattern are essential in managing the infections caused by these isolates. This study aimed to determine methicillin resistance, biofilm production, and ICR in S. aureus isolates from a tertiary care hospital in Kathmandu, Nepal.

MATERIALS AND METHODS

A total of 217 S. aureus isolated from different samples were processed following standard laboratory procedures. Antibiotic susceptibility testing was performed by the Kirby-Bauer disk diffusion technique. Methicillin-resistant S. aureus (MRSA) were identified by the cefoxitin disk diffusion test, and biofilm producers were examined using the microtiter plate technique. D-test and E-test were performed to determine inducible clindamycin resistance and minimum inhibitory concentration of vancomycin, respectively.

RESULTS

Among the 217 S. aureus isolates, 78.3% were multidrug-resistant (MDR), 47.0% were MRSA, 62.2% were biofilm producers, and 50.7% showed ICR. All MRSA isolates exhibited MIC levels of vancomycin within the susceptible range. Biofilm producers and MRSA isolates showed elevated antimicrobial resistance. MRSA was significantly associated with MDR. Biofilm-producing and multidrug-resistant MRSA isolates showed significantly higher MIC levels of vancomycin (p = 0.0013 and < 0.0001, respectively), while ICR was significantly higher in MDR (p = 0.0001) isolates.

CONCLUSION

High multidrug resistance, MRSA, and ICR in this study call for routine evaluation of antibiotic susceptibility patterns of S. aureus. Vancomycin can be used to treat serious staphylococcal infections. Clindamycin should be prescribed only after performing the D-test. Drugs like teicoplanin, chloramphenicol, doxycycline, amikacin, and levofloxacin can treat MRSA infections.

Evidence of cross-contamination of waste workers and transmission of antimicrobial resistance genes by coagulase-negative Staphylococcus isolated from dental solid waste: an intriguing study

The aim of this study was to phenotypically and genotypically identify coagulase-negative Staphylococcus (CoNS) recovered from the nostrils of waste workers and from dental waste; 135 strains were recovered and S. epidermidis was the prevailing species. Genetic similarity (100%) was observed between the two S. epidermidis isolated from different employees on the same shift and 85% similarity between the S. epidermidis recovered from an employee's nostril and from waste. The mecA gene was found in 20 CoNS, and 20% were also found to possess the vanA gene. The blaZ gene was detected in 46.7%, and the icaA (34.8%), B and C genes (11.8% each). Our findings emphasized the biological risk to which waste workers are exposed and unprecedently confirms that it was possible to recover genetically identical bacterial species from waste and from workers' nostrils. It is important to highlight that this risk is raised by the detection of relevant antimicrobial resistance genes. The results also suggest that effective measures to correctly manage waste and promote the rational use of antimicrobials should be adopted.

Biofilm Formation by Pathogenic Bacteria: Applying a Staphylococcus aureus Model to Appraise Potential Targets for Therapeutic Intervention

Carried in the nasal passages by up to 30% of humans, Staphylococcus aureus is recognized to be a successful opportunistic pathogen. It is a frequent cause of infections of the upper respiratory tract, including sinusitis, and of the skin, typically abscesses, as well as of food poisoning and medical device contamination. The antimicrobial resistance of such, often chronic, health conditions is underpinned by the unique structure of bacterial biofilm, which is the focus of increasing research to try to overcome this serious public health challenge. Due to the protective barrier of an exopolysaccharide matrix, bacteria that are embedded within biofilm are highly resistant both to an infected individual’s immune response and to any treating antibiotics. An in-depth appraisal of the stepwise progression of biofilm formation by S. aureus, used as a model infection for all cases of bacterial antibiotic resistance, has enhanced understanding of this complicated microscopic structure and served to highlight possible intervention targets for both patient cure and community infection control. While antibiotic therapy offers a practical means of treatment and prevention, the most favorable results are achieved in combination with other methods. This review provides an overview of S. aureus biofilm development, outlines the current range of anti-biofilm agents that are used against each stage and summarizes their relative merits.

New update on molecular diversity of clinical Staphylococcus aureus isolates in Iran: antimicrobial resistance, adhesion and virulence factors, biofilm formation and SCCmec typing

BACKGROUND

Staphylococcus aureus is often considered as a potential pathogen and resistant to a wide range of antibiotics. The pathogenicity of this bacterium is due to the presence of multiple virulence factors and the ability to form biofilm. SCCmec types I, II and III are mainly attributed to HA-MRSA, while SCCmec types IV and V have usually been reported in CA-MRSA infections.

METHODS AND RESULTS

In this study, we performed a cross-sectional study to determine the antimicrobial resistance, adhesion and virulence factors, biofilm formation and SCCmec typing of clinical S. aureus isolates in Iran. S. aureus isolates were identified using microbiological standard methods and antibiotic susceptibility tests were performed as described by the Clinical and Laboratory Standards Institute (CLSI) guidelines. Inducible resistance phenotype and biofilm formation were determined using D-test and tissue culture plate methods, respectively. Multiplex-PCRs were performed to detect adhesion and virulence factors, antibiotic resistance genes, biofilm formation and SCCmec typing by specific primers. Among 143 clinical samples, 67.8% were identified as MRSA. All isolates were susceptible to vancomycin. The prevalence of cMLS_B, iMLS_B and MS phenotypes were 61.1%, 22.2% and 14.8%, respectively. The TCP method revealed that 71.3% of isolates were able to form biofilm. The predominant virulence and inducible resistance genes in both MRSA and MSSA isolates were related to sea and ermC respectively. SCCmec type III was the predominant type.

CONCLUSIONS

Data show the high prevalence rates of virulence elements among S. aureus isolates, especially MRSA strains. This result might be attributed to antibiotic pressure, facilitating clonal selection.

Milieu matters: An in vitro wound milieu to recapitulate key features of, and probe new insights into, mixed-species bacterial biofilms

Bacterial biofilms are a major cause of delayed wound healing. Consequently, the study of wound biofilms, particularly in host-relevant conditions, has gained importance. Most in vitro studies employ refined laboratory media to study biofilms, representing conditions that are not relevant to the infection state. To mimic the wound milieu, in vitro biofilm studies often incorporate serum or plasma in growth conditions, or employ clot or matrix-based biofilm models. While incorporating serum or plasma alone is a minimalistic approach, the more complex in vitro wound models are technically demanding, and poorly compatible with standard biofilm assays. Based on previous reports of clinical wound fluid composition, we have developed an in vitro wound milieu (IVWM) that includes, in addition to serum (to recapitulate wound fluid), matrix elements and biochemical factors. With Luria-Bertani broth and Fetal Bovine Serum (FBS) for comparison, the IVWM was used to study planktonic growth, biofilm features, and interspecies interactions, of common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. We demonstrate that the IVWM recapitulates widely reported in vivo biofilm features such as biomass formation, metabolic activity, increased antibiotic tolerance, 3D structure, and interspecies interactions for monospecies and mixed-species biofilms. Further, the IVWM is simple to formulate, uses laboratory-grade components, and is compatible with standard biofilm assays. Given this, it holds potential as a tractable approach to study wound biofilms under host-relevant conditions.

Pharmacokinetics of Azalomycin F, a Natural Macrolide Produced by Streptomycete Strains, in Rats

As antimicrobial resistance has been increasing, new antimicrobial agents are desperately needed. Azalomycin F, a natural polyhydroxy macrolide, presents remarkable antimicrobial activities. To investigate its pharmacokinetic characteristics in rats, the concentrations of azalomycin F contained in biological samples, in vitro, were determined using a validated high-performance liquid chromatography–ultraviolet (HPLC-UV) method, and, in vivo, samples were assayed by an ultra-high performance liquid chromatography–tandem mass spectrometric (UPLC–MS/MS) method. Based on these methods, the pharmacokinetics of azalomycin F were first investigated. Its plasma concentration-time courses and pharmacokinetic parameters in rats were obtained by a non-compartment model for oral (26.4 mg/kg) and intravenous (2.2 mg/kg) administrations. The results indicate that the oral absolute bioavailability of azalomycin F is very low (2.39 ± 1.28%). From combinational analyses of these pharmacokinetic parameters, and of the results of the in-vitro absorption and metabolism experiments, we conclude that azalomycin F is absorbed relatively slowly and with difficulty by the intestinal tract, and subsequently can be rapidly distributed into the tissues and/or intracellular f of rats. Azalomycin F is stable in plasma, whole blood, and the liver, and presents plasma protein binding ratios of more than 90%. Moreover, one of the major elimination routes of azalomycin F is its excretion through bile and feces. Together, the above indicate that azalomycin F is suitable for administration by intravenous injection when used for systemic diseases, while, by oral administration, it can be used in the treatment of diseases of the gastrointestinal tract.

Influence of biofilm growth age, media, antibiotic concentration and exposure time on Staphylococcus aureus and Pseudomonas aeruginosa biofilm removal in vitro

BACKGROUND

Biofilm is known to be tolerant towards antibiotics and difficult to eradicate. Numerous studies have reported minimum biofilm eradication concentration (MBEC) values of antibiotics for many known biofilm pathogens. However, the experimental parameters applied in these studies differ considerably, and often the rationale behind the experimental design are not well described. This makes it difficult to compare the findings. To demonstrate the importance of experimental parameters, we investigated the influence of biofilm growth age, antibiotic concentration and treatment duration, and growth media on biofilm eradication. Additionally, OSTEOmycin™, a clinically used antibiotic containing allograft bone product, was tested for antibiofilm efficacy.

RESULTS

The commonly used Calgary biofilm device was used to grow 24 h and 72 h biofilms of Staphylococcus aureus and Pseudomonas aeruginosa, which were treated with time-dependent vancomycin (up to 3000 mg L- 1) and concentration-dependent tobramycin (up to 80 mg L- 1), respectively. Two common bacteriological growth media, tryptic soy broth (TSB) and cation-adjusted Mueller Hinton broth (CaMHB), were tested. We found for both species that biofilms were more difficult to kill in TSB than in CaMHB. Furthermore, young biofilms (24 h) were easier to eradicate than old biofilms (72 h). In agreement with vancomycin being time-dependent, extension of the vancomycin exposure increased killing of S. aureus biofilms. Tobramycin treatment of 24 h P. aeruginosa biofilms was found concentration-dependent and time-independent, however, increasing killing was indicated for 72 h P. aeruginosa biofilms. Treatment with tobramycin containing OSTEOmycin T™ removed 72 h and 168 h P. aeruginosa biofilms after 1 day treatment, while few 72 h S. aureus biofilms survived after 2 days treatment with vancomycin containing OSTEOmycin V™.

CONCLUSIONS

This study demonstrated biofilm removal efficacy was influenced by media, biofilm age and antibiotic concentration and treatment duration. It is therefore necessary to taking these parameters into consideration when designing experiments. The results of OSTEOmycin™ products indicated that simple in vitro biofilm test could be used for initial screening of antibiofilm products. For clinical application, a more clinically relevant biofilm model for the specific biofilm infection in question should be developed to guide the amount of antibiotics used for local antibiofilm treatment.

Azalomycin F5a Eradicates Staphylococcus aureus Biofilm by Rapidly Penetrating and Subsequently Inducing Cell Lysis

Antimicrobial resistance has emerged as a serious threat to public health. Bacterial biofilm, as a natural lifestyle, is a major contributor to resistance to antimicrobials. Azalomycin F_5a, a natural guanidine-containing polyhydroxy macrolide, has remarkable activities against Gram-positive bacteria, including Staphylococcus aureus, a major causative agent of hospital-acquired infections. To further evaluate its potential to be developed as a new antimicrobial agent, its influence on S. aureus biofilm formation was evaluated using the crystal violet method, and then its eradication effect against mature biofilms was determined by confocal laser scanning microscopy, the drop plate method, and regrowth experiments. The results showed that azalomycin F_5a could significantly inhibit S. aureus biofilm formation, and such effects were concentration dependent. In addition, it can also eradicate S. aureus mature biofilms with the minimum biofilm eradication concentration of 32.0 μg/mL. As extracellular deoxyribonucleic acid (eDNA) plays important roles in the structural integrity of bacterial biofilm, its influence on the eDNA release in S. aureus biofilm was further analyzed using gel electrophoresis. Combined with our previous works, these results indicate that azalomycin F_5a could rapidly penetrate biofilm and causes damages to the cell membrane, leading to an increase in DNase release and eventually eradicating S. aureus biofilm.

Balancing Physicochemical Properties of Phenylthiazole Compounds with Antibacterial Potency by Modifying the Lipophilic Side Chain

Bacterial resistance to antibiotics is presently one of the most pressing healthcare challenges and necessitates the discovery of new antibacterials with unique chemical scaffolds. However, the determination of the optimal balance between structural requirements for pharmacological action and pharmacokinetic properties of novel antibacterial compounds is a significant challenge in drug development. The incorporation of lipophilic moieties within a compound's core structure can enhance biological activity but have a deleterious effect on drug-like properties. In this Article, the lipophilicity of alkynylphenylthiazoles, previously identified as novel antibacterial agents, was reduced by introducing cyclic amines to the lipophilic side chain. In this regard, substitution with methylpiperidine (compounds 14-16) and thiomorpholine (compound 19) substituents significantly enhanced the aqueous solubility profile of the new compounds more than 150-fold compared to the first-generation lead compound 1b. Consequently, the pharmacokinetic profile of compound 15 was significantly enhanced with a notable improvement in both half-life and the time the compound's plasma concentration remained above its minimum inhibitory concentration (MIC) against methicillin-resistant Staphylococcus aureus (MRSA). In addition, compounds 14-16 and 19 were found to exert a bactericidal mode of action against MRSA and were not susceptible to resistance formation after 14 serial passages. Moreover, these compounds (at 2× MIC) were superior to the antibiotic vancomycin in the disruption of the mature MRSA biofilm. The modifications to the alkynylphenylthiazoles reported herein successfully improved the pharmacokinetic profile of this new series while maintaining the compounds' biological activity against MRSA.

Biofilm production by coagulase-negative Staphylococcus: a review

ABSTRACT: This review aimed to describe the biofilm formation ability of coagulase-negative Staphylococcus, addressing its impact to the food industry. Coagulase-negative Staphylococcus have the ability to produce enterotoxins in food, making it an important line of study, as it constitutes a risk to public health. The biofilm formation by these microorganisms requires physicochemical processes, such as hydrophobic forces, which are essential for the first phase of fixing the biofilm on the surface. In industrial facilities, stainless steel equipment is the most associated with the formation of biofilms, due to the presence grooves and cracks. Many species of coagulase-negative Staphylococcus produce biofilm, but the most studied is S. epidermidis, as it is the most frequently isolated from food. Coagulase-negative Staphylococcus form biofilm on different surfaces in the food industry, and can become a source of permanent contamination, that can be present in the final product, intended for human consumption. Among other alternatives to combat the formation of biofilm in industrial food facilities, there is the implementation of Good Manufacturing Practices, which is effective in preventing bacterial adhesion, and therefore, the formation of biofilm. However, further studies are needed in order to quantify the occurrence of coagulase-negative Staphylococcus biofilms in the food industry.

Synthesis and antimicrobial evaluation of new halogenated 1,3-Thiazolidin-4-ones

The ongoing prevalence of multidrug-resistant bacterial pathogens requires the development of new effective antibacterial agents. In this study, two series of halogenated 1,3-thiazolidin-4-ones were synthesized and characterized. All the synthesized thiazolidinone derivatives were evaluated for their antimicrobial activity. Biological screening of the tested compounds revealed the antibacterial activity of the chlorinated thiazolidinones 4a, 4b and 4c against Escherichia coli TolC-mutant, with MIC values of 16 µg/mL. A combination of a sub-inhibitory concentration of colistin (0.25 × MIC) with compounds 4a, 4b or 4c showed antibacterial activity against different Gram-negative bacteria (MICs = 4-16 µg/mL). Interestingly, compounds 4a, 4b and 4c were not cytotoxic to murine fibroblasts and Caco-2 cells. The chlorinated thiazolidinone derivative 16d demonstrated a bacteriostatic activity against a panel of pathogenic Gram-positive bacteria, including clinical isolates of methicillin and vancomycin-resistant Staphylococcus aureus, Listeria monocytogenes and multidrug-resistant Staphylococcus epidermidis (MICs = 8 - 64 µg/mL), with no cytotoxicity against both Caco-2 and L929 cells. Compound 16d was superior to vancomycin in disruption of the pre-formed MRSA biofilm. Furthermore, the three fluorinated thiazolidinone derivatives 26c, 30c and 33c showed a hindrance to hemolysin activity, without cytotoxicity against L929 cells.

Phenylthiazoles with nitrogenous side chain: An approach to overcome molecular obesity

A novel series of phenylthiazoles bearing cyclic amines at the phenyl-4 position was prepared with the objective of decreasing lipophilicity and improving the overall physicochemical properties and pharmacokinetic profile of the compounds. Briefly, the piperidine ring (compounds 10 and 12) provided the best ring size in terms of antibacterial activity when tested against 16 multidrug-resistant clinical isolates. Both compounds were superior to vancomycin in the ability to eliminate methicillin-resistant Staphylococcus aureus (MRSA), residing within infected macrophages and to disrupt mature MRSA biofilm. Additionally, compounds 10 and 12 exhibited a fast-bactericidal mode of action in vitro. Furthermore, the new derivatives were 160-times more soluble in water than the previous lead compound 1b. Consequently, compound 10 was orally bioavailable with a highly-acceptable pharmacokinetic profile in vivo that exhibited a half-life of 4 h and achieved a maximum plasma concentration that exceeded the minimum inhibitory concentration (MIC) values against all tested bacterial isolates.

In vitro comparison of efficacy of catheter locks in the treatment of catheter related blood stream infection

BACKGROUND & AIMS

Venous access used for parenteral nutrition (PN) application is extremely important for patients with intestinal failure. Potential loss of venous access might be a catastrophy for the patient. Catheter infections are a serious complication of PN application. Systemic administration of antibiotics as well as local antibiotic locks into the catheter to sterilize the catheter are used to treat catheter infections. However, there is no clear recommendation applying use of antibiotic locks, that would specify the type and concentration of antimicrobial medication. Our objective were to compare the efficacy of different types of antimicrobial lock therapy (especially taurolidine) and their concentrations to eradicate infectious agents.

METHODS

Bacterial strains of microorganisms (Staphylococcus epidermidis, Staphylococcus aureus, methicillin resistant S. aureus (MRSA), Pseudomonas aeruginosa, multidrug-resistant P. aeruginosa, Candida albicans) were used. Subsequently, the catheter was exposed to the microbes and then was incubated with a specific lock for 2 or 24 h at 37 °C. We used these locks: ethanol 70%, taurolidine, gentamicine in concentrations 0,5, 1 and 10 mg/ml and vancomycine in concentrations 1, 5, and 10 mg/ml. The number of remaining CFU (colony forming units) was compared after incubation.

RESULTS

70% ethanol and taurolidine were most effective for all studied microorganisms. Gentamicine was more effective than vancomycine.

CONCLUSIONS

The most effective antimicrobial lock solutions to eradicate selected pathogenic agents were ethanol and taurolidine. Use of antibiotics is often effective after many hours of treatment and there is a risk of inadequate therapy.

Naphthylthiazoles: Targeting Multidrug-Resistant and Intracellular Staphylococcus aureus with Biofilm Disruption Activity

Thirty-two new naphthylthiazole derivatives were synthesized with the aim of exploring their antimicrobial effect on multidrug-resistant Gram-positive bacteria. Compounds 25 and 32, with ethylenediamine and methylguanidine side chains, represent the most promising derivatives, as their antibacterial spectrum includes activity against multidrug-resistant staphylococcal and enterococcal strains. Moreover, the new derivatives are highly advantageous over the existing frontline therapeutics for the treatment of multidrug-resistant Gram-positive bacteria. In this vein, compound 25 possesses three attributes: no bacterial resistance was developed against it even after 15 passages, it was very efficient in targeting intracellular pathogens, and it exhibited a concentration-dependent ability to disrupt the preformed bacterial biofilm.

Carbapenem-resistant Pseudomonas aeruginosa: association with virulence genes and biofilm formation

Pseudomonas aeruginosa is an opportunistic pathogen that causes frequently nosocomial infections, currently becoming more difficult to treat due to the various resistance mechanisms and different virulence factors. The purpose of this study was to determine the risk factors independently associated with the development of bacteremia by carbapenem-resistant P. aeruginosa, the frequency of virulence genes in metallo-β-lactamases producers and to evaluate their ability to produce biofilm. We conducted a case–control study in the Uberlândia Federal University – Hospital Clinic, Brazil. Polymerase Chain Reaction was performed for metallo-β-lactamases and virulence genes. Adhesion and biofilm assays were done by quantitative tests. Among the 157 strains analyzed, 73.9% were multidrug-resistant, 43.9% were resistant to carbapenems, 16.1% were phenotypically positive for metallo-β-lactamases, and of these, 10.7% were positive for bla_SPM gene and 5.3% positive for bla_VIM. The multivariable analysis showed that mechanical ventilation, enteral/nasogastric tubes, primary bacteremia with unknown focus, and inappropriate therapy were independent risk factors associated with bacteremia. All tested strains were characterized as strongly biofilm producers. A higher mortality was found among patients with bacteremia by carbapenem-resistant P. aeruginosa strains, associated independently with extrinsic risk factors, however it was not evident the association with the presence of virulence and metallo-β-lactamases genes.

Antimicrobial Resistance Profile of Planktonic and Biofilm Cells of Staphylococcus aureus and Coagulase-Negative Staphylococci

The objective of the present study was to determine the antimicrobial resistance profile of planktonic and biofilm cells of Staphylococcus aureus and coagulase-negative staphylococci (CoNS). Two hundred Staphylococcus spp. strains were studied, including 50 S. aureus and 150 CoNS strains (50 S. epidermidis, 20 S. haemolyticus, 20 S. warneri, 20 S. hominis, 20 S. lugdunensis, and 20 S. saprophyticus). Biofilm formation was investigated by adherence to polystyrene plates. Positive strains were submitted to the broth microdilution method to determine the minimum inhibitory concentration (MIC) for planktonic and biofilm cells and the minimal bactericidal concentration for biofilm cells (MBCB). Forty-nine Staphylococcus spp. strains (14 S. aureus, 13 S. epidermidis, 13 S. saprophyticus, 3 S. haemolyticus, 1 S. hominis, 3 S. warneri, and 2 S. lugdunensis) were biofilm producers. These isolates were evaluated regarding their resistance profile. Determination of planktonic cell MIC identified three (21.4%) S. aureus strains that were resistant to oxacillin and six (42.8%) that were resistant to erythromycin. Among the CoNS, 31 (88.6%) strains were resistant to oxacillin, 14 (40%) to erythromycin, 18 (51.4%) to gentamicin, and 8 (22.8%) to sulfamethoxazole/trimethoprim. None of the planktonic isolates were resistant to vancomycin or linezolid. MICs were 2-, 4-, 8-, and up to 16-fold higher for biofilm cells than for planktonic cells. This observation was more common for vancomycin and erythromycin. The MBCB ranged from 8 to >256 µg/mL for oxacillin, 128 to >128 µg/mL for vancomycin, 256 to >256 µg/mL for erythromycin and gentamicin, >64 µg/mL for linezolid, and 32/608 to >32/608 µg/mL for sulfamethoxazole/trimethoprim. The results showed considerably higher MICs for S. aureus and CoNS biofilm cells compared to planktonic cells. Analysis of MBCM confirmed that even high concentrations of vancomycin were unable to eliminate the biofilms of S. aureus and CoNS species. Linezolid was the most effective drug in inhibiting staphylococci in the biofilm, without an increase in the MIC, when compared to planktonic cells. None of the isolates were resistant to this drug.

Medicinal Plants Used by a Mbyá-Guarani Tribe against Infections: Activity on KPC-Producing Isolates and Biofilm-Forming Bacteria

The traditional use of medicinal plants for treatment of infectious diseases by an indigenous Mbyá-Guarani tribe from South Brazil was assessed by evaluating the antibiotic and antibiofilm activities against relevant bacterial pathogens. Aqueous extracts from 10 medicinal plants were prepared according to indigenous Mbyá-Guarani traditional uses. To evaluate antibiotic (OD600) and antibiofilm (crystal violet method) activities, Pseudomonas aeruginosa ATCC 27853, Staphylococcus epidermidis ATCC 35984 and seven multi-drug resistant Klebsiella pneumoniae carbapenemase (KPC)-producing bacterial clinical isolates were challenged with the extracts. Furthermore, the susceptibility profile of KPC-producing bacteria and the ability of these isolates to form biofilm were evaluated. The plants Campomanesia xanthocarpa, Maytenus ilicifolia, Bidens pilosa and Verbena sp. showed the best activity against bacterial growth and biofilm formation. The majority of KPC-producing isolates, which showed strong ability to form biofilm and a multidrug resistance profile, was inhibited by more than 50% by some extracts. The Enterobacter cloacae (KPC 05) clinical isolate was the only one resistant to all extracts. This study confirms the importance of indigenous traditional medicinal knowledge and describes for the first time the ability of these plants to inhibit biofilm formation and/or bacterial growth of multi-drug resistant KPC-producing isolates.

Significance of biofilm for the prosthetic surgeon

Biofilm formation on implanted medical devices is becoming more recognized as both a common finding and a potential problem. Although seen frequently in nature, these sequestered bacterial communities are proving to be an assiduous enemy as medical device technologies advance. The penile prosthesis has gone through many improvements, now with a more reliable mechanical function and a reduced infection rate. However, there remains a notable increase in infectious risk in revisions compared to novel cases, with many implants found to harbor a subclinical bacterial presence isolated in biofilms. This article focuses on recent updates in implant technology and surgical technique to combat infection, and reviews current research on biofilm prevention and treatment.

Perfil de sensibilidade de células sésseis e planctônicas de Escherichia coli a antimicrobianos usados no tratamento da mastite bovina

Escherichia coli é um micro-organismo altamente adaptativo e sua habilidade em formar biofilmes pode ser fundamental na resistência a tratamentos com antimicrobianos. A avaliação da concentração mínima inibitória (CMI) vem sendo utilizada para verificar a sensibilidade dos micro-organismos aos antimicrobianos. Entretanto, quando se avaliam células sésseis, a concentração do antimicrobiano requerido para erradicação do biofilme é maior do que a determinada pela CMI. Objetivou-se comparar as CMI com as concentrações mínimas de erradicação de biofilmes (CMEB) de antimicrobianos usados no tratamento da mastite em 27 isolados de E. coli produtores de biofilmes provenientes de mastite. Os isolados foram submetidos a testes de sensibilidade a antimicrobianos usados no tratamento da mastite, tanto para células planctônicas, por meio da CMI, quanto para células sésseis, pela avaliação da CMEB. Os resultados revelaram uma alta sensibilidade: apenas quatro (14,8%) isolados obtiveram valores da CMI elevados, variando de 4 a 10µg/mL, sendo classificados como resistentes. Para os demais isolados (85,2%), os valores foram menores, variando de 0,125 a 2µg/mL, classificados como sensíveis. A avaliação de CMEB indicou que a concentração dos antimicrobianos necessária para eliminar as células sésseis variou de 100µg/mL a 500µg/mL. Os valores de CMEB foram significativamente maiores nos isolados grandes e moderados produtores de biofilmes em relação aos isolados fracos produtores de biofilmes (p<0,001). Não houve correlação entre os valores de CMEB e CMI (p>0,05). A escolha da terapêutica antimicrobiana correta para o tratamento de infecções intramamárias em bovinos relacionadas com a produção de biofilmes parece exigir a aplicação de testes mais específicos. Testes de susceptibilidade antimicrobiana baseados apenas em valores de CMI mostraram-se ineficazes em determinar com precisão a susceptibilidade das células bacterianas sésseis.

Rifampicin fails to eradicate mature biofilm formed by methicillin-resistant Staphylococcus aureus

INTRODUCTION

Antimicrobial activity on biofilms depends on their molecular size, positive charges, permeability coefficient, and bactericidal activity. Vancomycin is the primary choice for methicillin-resistant Staphylococcus aureus (MRSA) infection treatment; rifampicin has interesting antibiofilm properties, but its effectivity remains poorly defined.

METHODS

Rifampicin activity alone and in combination with vancomycin against biofilm-forming MRSA was investigated, using a twofold serial broth microtiter method, biofilm challenge, and bacterial count recovery.

RESULTS

Minimal inhibitory concentration (MIC) and minimal bactericidal concentration for vancomycin and rifampicin ranged from 0.5 to 1mg/l and 0.008 to 4mg/l, and from 1 to 4mg/l and 0.06 to 32mg/l, respectively. Mature biofilms were submitted to rifampicin and vancomycin exposure, and minimum biofilm eradication concentration ranged from 64 to 32,000 folds and from 32 to 512 folds higher than those for planktonic cells, respectively. Vancomycin (15mg/l) in combination with rifampicin at 6 dilutions higher each isolate MIC did not reach in vitro biofilm eradication but showed biofilm inhibitory capacity (1.43 and 0.56log10 CFU/ml reduction for weak and strong biofilm producers, respectively; p<0.05).

CONCLUSIONS

In our setting, rifampicin alone failed to effectively kill biofilm-forming MRSA, demonstrating stronger inability to eradicate mature biofilm compared with vancomycin.

Inhibition of biofilm maturation by linezolid in meticillin-resistant Staphylococcus epidermidis clinical isolates: comparison with other drugs

Biofilm resistance mechanisms are multifactorial and vary from one organism to another. The purpose of this study was to investigate the efficacy of linezolid against indwelling device-related meticillin-resistant Staphylococcus epidermidis (MRSE) biofilm, and compare this with other antimicrobials. MICs, minimum biofilm inhibitory concentrations (MBICs) and minimum biofilm eradication concentrations (MBECs) were determined by the microtitre plate method. Fourteen and thirteen isolates from patients with indwelling device-related bacteraemia (IDB) and indwelling device colonization not associated with bacteraemia, respectively, were assessed. High MBIC was associated with a high intensity of biofilm formation (gentamicin r=0.796; linezolid r=0.477; rifampicin r=0.634; tigecycline r=0.410; and vancomycin r=0.771), but this correlation was not observed with MBEC. Linezolid demonstrated better in vitro antimicrobial activity than other antimicrobials (MBIC - gentamicin P<0.001, rifampicin P=0.019, vancomycin P=0.008; MBEC - gentamicin P<0.001, rifampicin P=0.002, vancomycin P<0.001). Biofilm growth inhibition was strongly associated with biofilm formation intensity; however, biofilm eradication was not cell number dependent. MRSE biofilm eradication would represent a huge advance for IDB, although high concentrations of gentamicin, linezolid, rifampicin, tigecycline and vancomycin were required for that. In general, linezolid reached better in vitro concentrations and was demonstrated to be highly active against MRSE biofilms by inhibiting their growth during biofilm formation.

Enhancement of antistaphylococcal activities of six antimicrobials against sasG-negative methicillin-susceptible Staphylococcus aureus: an in vitro biofilm model

This study was designed to evaluate antimicrobial activities against methicillin-susceptible Staphylococcus aureus in both sessile and planktonic forms and to detect genes associated with this biofilm phenotype. Minimal biofilm inhibition and eradication concentrations (MBIC and MBEC, respectively) were determined by an in vitro biofilm model, and icaA, atlA, and sasG genes were detected by polymerase chain reaction. Vancomycin and tigecycline presented better biofilm inhibitory activity (MBIC range: 4-8 μg/mL) (P ≤ 0.05) and lower MBEC/MIC ratios (P ≤ 0.001) than other antimicrobials. All isolates harbored icaA and atlA, whereas sasG was present only in strong biofilm formers (P ≤ 0.05). Interestingly, antimicrobial activities against sasG- weak biofilm formers were significantly higher than those against sasG+ strong biofilm formers (P ≤ 0.05), demonstrating that number of cells in a biofilm matrix affected the antimicrobial activity, which was also variable, and might be associated with specific genetic determinants. To our knowledge, this was the first study reporting the presence of sasG in clinical isolates of S. aureus in South America.

In vitro antioxidant, anticoagulant and antimicrobial activity and in inhibition of cancer cell proliferation by xylan extracted from corn cobs

Xylan is one of most abundant polymer after cellulose. However, its potential has yet to be completely recognized. Corn cobs contain a considerable reservoir of xylan. The aim of this work was to study some of the biological activities of xylan obtained from corn cobs after alkaline extraction enhanced by ultrasonication. Physical chemistry and infrared analyses showed 130 kDa heteroxylan containing mainly xylose:arabinose: galactose:glucose (5.0:1.5:2.0:1.2). Xylan obtained exhibited total antioxidant activity corresponding to 48.5 mg of ascorbic acid equivalent/g of xylan. Furthermore, xylan displayed high ferric chelating activity (70%) at 2 mg/mL. Xylan also showed anticoagulant activity in aPTT test. In antimicrobial assay, the polysaccharide significantly inhibited bacterial growth of Klebsiella pneumoniae. In a test with normal and tumor human cells, after 72 h, only HeLa tumor cell proliferation was inhibited (p < 0.05) in a dose-dependent manner by xylan, reaching saturation at around 2 mg/mL, whereas 3T3 normal cell proliferation was not affected. The results suggest that it has potential clinical applications as antioxidant, anticoagulant, antimicrobial and antiproliferative compounds.

High biofilm production by invasive multiresistant staphylococci

Biofilm-forming staphylococci are known for being opportunistic and invasive pathogens that cause severe disease, mostly catheter-related infections. Early detection and pathogenic strains carrying highly transferable resistance cassettes epidemiology are essential for infection spread control. Hence, this study was designed to evaluate staphylococci biofilm formation and SCCmec typing. Biofilm production and SCCmec typing were evaluated using a semi-quantitative method based on microtiter plates and a multiplex PCR for types, I-V, respectively. Blood cultures and peripheral intravenous device (IVD) staphylococci were consecutively enrolled and allocated into two different groups (invasive and colonizing) based on clinical and microbiological criteria. Seventy-four invasive and 30 colonizing isolates from distinct patients were studied. Vancomycin was the most administrated antimicrobial agent among these patient's treatments. Biofilm formation was observed in 89% of invasive and 64% of colonizing isolates (p < 0.05). There was significant difference regarding SCCmec typing between colonizing and invasive isolates when harboring SCCmec types IV or V (p < 0.05), but no correlation between biofilm intensity and SCCmec types was verified. The SCCmec elements spread are still ongoing and for that reason, antimicrobial resistance evolution in invasive and colonizing biofilm-forming staphylococci is highly relevant.

Potential of medicinal plants from the Brazilian semi-arid region (Caatinga) against Staphylococcus epidermidis planktonic and biofilm lifestyles

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants from the Caatinga, a Brazilian xeric shrubland, are used in folk medicine to treat infections. These ethnopharmacological data can contribute to obtaining new antimicrobial/antibiofilm extracts and natural product prototypes for the development of new drugs. The aim of this study was to investigate the antibiofilm and antibacterial activities of 45 aqueous extracts from 24 Caatinga plant species.

MATERIALS AND METHODS

The effect of aqueous extracts on planktonic cells and on biofilm formation by Staphylococcus epidermidis was studied by the OD(600) absorbance and by the crystal violet assay, respectively. Scanning electron microscopy (SEM) was used to generate comparative images of extract-treated and untreated biofilms. Chromatographic analyses were performed to characterize the active extracts.

RESULTS

The in vitro screening, at 0.4 mg/mL and 4.0mg/mL, showed 20 plants effective in preventing biofilm formation and 13 plants able to inhibit planktonic bacterial growth. SEM images demonstrated distinct profiles of bacterial adhesion, matrix production and cell morphology according to different treatments and surfaces. The phytochemical analysis of the selected active extracts indicates the polyphenols, coumarins, steroids and terpenes as possible active compounds.

CONCLUSION

This study describes the first antibiofilm and antibacterial screening of Caatinga plants against S. epidermidis. The evaluation presented in this study confirms several ethnopharmacological reports and can be utilized to identify new antibiofilm and antibacterial products against S. epidermidis from traditional Brazilian medicine.