Effect of the combination of clarithromycin and amikacin on Pseudomonas aeruginosa biofilm in an animal model of ureteral stent infection

The Potentiation Activity of Azithromycin in Combination with Colistin or Levofloxacin Against Pseudomonas aeruginosa Biofilm Infection

Objective

Pseudomonas aeruginosa (PA) often displays drug resistance and biofilm-mediated adaptability. Here, we aimed to evaluate the antibiofilm efficacy of azithromycin-based combination regimens.

Methods

Minimum inhibitory concentrations (MICs), minimal biofilm eradication concentrations (MBECs), and MBEC-combination of azithromycin, colistin, amikacin, and levofloxacin to bioluminescent strain PAO1 and carbapenem-resistant PAO1 (CRPAO1) were assessed. An animal biofilm infection model was established and detected using a live animal bio-photonic imaging system.

Results

In vitro, PAO1 and CRPAO1 were susceptible to colistin, amikacin, and levofloxacin, while they were unsusceptible to azithromycin. The combinations based on azithromycin have no synergistic effect on biofilm in vitro. In vivo, azithromycin plus colistin or levofloxacin could shorten the PAO1 biofilm eradication time, which totally eradicates the biofilm in all mice on the 8th or 6th day, while monotherapy only eradicate biofilm in 70% or 80% mice on the 8th day. For CRPAO1 biofilm, only azithromycin-colistin combination and colistin monotherapy eradicated the bacteria in 60% and 40% of mice at the 6th day.

Conclusion

Azithromycin-based combinations containing levofloxacin or colistin had no synergistic effect in vitro, and they are promising for clinical applications due to the good synergistic activity against PAO1 biofilms in vivo.

An Evaluation of Parylene Thin Films to Prevent Encrustation for a Urinary Bladder Pressure MEMS Sensor System

Recent developments in urological implants have focused on preventive strategies to mitigate encrustation and biofilm formation. Parylene, a conformal, pinhole-free polymer coating, has gained attention due to its high biocompatibility and chemical resistance, excellent barrier properties, and low friction coefficient. This study aims to evaluate the effectiveness of parylene C in comparison to a parylene VT4 grade coating in preventing encrustation on a urinary bladder pressure MEMS sensor system. Additionally, silicon oxide (SiOx) applied as a finish coating was investigated for further improvements. An in vitro encrustation system mimicking natural urine flow was used to quantify the formation of urinary stones. These stones were subsequently analyzed using Fourier transform infrared spectrometry (FTIR). Encrustation results were then discussed in relation to coating surface chemical properties. Parylene C and VT4 grades demonstrated a very low encrustation mass, making them attractive options for encrustation prevention. The best performance was achieved after the addition of a hydrophilic SiOx finish coating on parylene VT4 grade. Parylene-based encapsulation proved to be an outstanding solution to prevent encrustation for urological implants.

The comparative effects of erythromycin and amikacin on acute respiratory Pseudomonas aeruginosa infection

BACKGROUND

One of the most common causes of pneumonia is Pseudomonas aeruginosa (P. aeruginosa). As with other microbial pathogens, this bacterium tends to develop resistance to various antibiotics. Amikacin and erythromycin, which are from the aminoglycoside and macrolide antibiotic families, are used to treat respiratory infections caused by P. aeruginosa.

OBJECTIVES

This study explored whether amikacin, erythromycin or a combination of both works better against P. aeruginosa acute lung infection.

METHODS

For this study, 32 rats were used. The trachea of rats was exposed aseptically and their lung was infected with P. aeruginosa through trachea. Then, according to the group, they received amikacin, erythromycin or a combination of both for 1 week. Finally, they were euthanised on the 3rd and 7th days post-infection. The macroscopic and microscopic evaluations of the lungs, kidney and liver were performed. The right lung was collected for in vivo bacteriological analysis.

RESULTS

The amikacin group (A group) had a statistically significantly lower macroscopic and microscopic scores than the other groups (p < 0.05). In vivo bacteriological test revealed that the A group had significantly lower lung bacterial load (p < 0.05).

CONCLUSIONS

In summary, it was concluded that amikacin could help alleviate the respiratory infection caused by P. aeruginosa solely, and it was more effective than erythromycin.

Pseudomonas aeruginosa: Infections, Animal Modeling, and Therapeutics

Pseudomonas aeruginosa is an important Gram-negative opportunistic pathogen which causes many severe acute and chronic infections with high morbidity, and mortality rates as high as 40%. What makes P. aeruginosa a particularly challenging pathogen is its high intrinsic and acquired resistance to many of the available antibiotics. In this review, we review the important acute and chronic infections caused by this pathogen. We next discuss various animal models which have been developed to evaluate P. aeruginosa pathogenesis and assess therapeutics against this pathogen. Next, we review current treatments (antibiotics and vaccines) and provide an overview of their efficacies and their limitations. Finally, we highlight exciting literature on novel antibiotic-free strategies to control P. aeruginosa infections.

Engineering biomaterials to prevent post-operative infection and fibrosis

Implantable biomaterials are essential surgical devices, extending and improving the quality of life of millions of people globally. Advances in materials science, manufacturing, and in our understanding of the biological response to medical device implantation over several decades have resulted in improved safety and functionality of biomaterials. However, post-operative infection and immune responses remain significant challenges that interfere with biomaterial functionality and host healing processes. The objectives of this review is to provide an overview of the biology of post-operative infection and the physiological response to implanted biomaterials and to discuss emerging strategies utilizing local drug delivery and surface modification to improve the long-term safety and efficacy of biomaterials.

Mimicking biofilm formation and development: Recent progress in in vitro and in vivo biofilm models

Biofilm formation in living organisms is associated to tissue and implant infections, and it has also been linked to the contribution of antibiotic resistance. Thus, understanding biofilm development and being able to mimic such processes is vital for the successful development of antibiofilm treatments and therapies. Several decades of research have contributed to building the foundation for developing in vitro and in vivo biofilm models. However, no such thing as an "all fit" in vitro or in vivo biofilm models is currently available. In this review, in addition to presenting an updated overview of biofilm formation, we critically revise recent approaches for the improvement of in vitro and in vivo biofilm models.

Placement of ureteral stents in three rabbits for the treatment of obstructive ureterolithiasis

Management of ureteral obstruction with stenting is often associated with a lower rate of complications than ureterotomy in domestic carnivores, but this treatment has not been previously evaluated in rabbits. Three rabbits (7, 6 and 10 years old) were diagnosed with unilateral obstructive ureterolithiasis associated with hydronephrosis and hydroureter on abdominal ultrasound. Decreased overall renal function was confirmed in all three cases. Ureteral stents were placed retrogradely via cystotomy without complication in two cases and anterogradely via nephrostomy in the third case. Survival after stent placement was 30, 3 and 8 months, with encrustation of the stent and re-obstruction occurring 18, 1 and 6 months after stent placement in successive cases. Ureteral stenting can be considered for short-term management of ureterolithiasis in rabbits to improve renal function and maintain quality of life. Ultrasound or radiographic monitoring is recommended to detect encrustation of the stent. Studies comparing ureteral stenting to ureterotomy in rabbits are needed to determine the effectiveness of these techniques.

Evaluating Efficacy of Antimicrobial and Antifouling Materials for Urinary Tract Medical Devices: Challenges and Recommendations

In Europe, the mean incidence of urinary tract infections in intensive care units is 1.1 per 1000 patient-days. Of these cases, catheter-associated urinary tract infections (CAUTI) account for 98%. In total, CAUTI in hospitals is estimated to give additional health-care costs of £1-2.5 billion in the United Kingdom alone. This is in sharp contrast to the low cost of urinary catheters and emphasizes the need for innovative products that reduce the incidence rate of CAUTI. Ureteral stents and other urinary-tract devices suffer similar problems. Antimicrobial strategies are being developed, however, the evaluation of their efficacy is very challenging. This review aims to provide considerations and recommendations covering all relevant aspects of antimicrobial material testing, including surface characterization, biocompatibility, cytotoxicity, in vitro and in vivo tests, microbial strain selection, and hydrodynamic conditions, all in the perspective of complying to the complex pathology of device-associated urinary tract infection. The recommendations should be on the basis of standard assays to be developed which would enable comparisons of results obtained in different research labs both in industry and in academia, as well as provide industry and academia with tools to assess the antimicrobial properties for urinary tract devices in a reliable way.

Freeze-casting porous chitosan ureteral stents for improved drainage

As a new strategy for improved urinary drainage, in parallel to the potential for additional functions such as drug release and self-removal, highly porous chitosan stents are manufactured by radial, bi-directional freeze-casting. Inserting the porous stent in to a silicone tube to emulate its placement in the ureter shows that it is shape conforming and remains safely positioned in place, also during flow tests, including those performed in a peristaltic pump. Cyclic compression tests on fully-hydrated porous stents reveal high stent resilience and close to full elastic recovery upon unloading. The drainage performance of the chitosan stent is evaluated, using effective viscosity in addition to volumetric flow and flux; the porous stent's performance is compared to that of the straight portion of a commercial 8 Fr double-J stent which possesses, in its otherwise solid tube wall, regularly spaced holes along its length. Both the porous and the 8 Fr stent show higher effective viscosities, when tested in the silicone tube. The performance of the porous stent improves considerably more (47.5%) than that of the 8 Fr stent (30.6%) upon removal from the tube, illustrating the effectiveness of the radially aligned porosity for drainage. We conclude that the newly-developed porous chitosan ureteral stent merits further in vitro and in vivo assessment of its promise as an alternative and complement to currently available medical devices. STATEMENT OF SIGNIFICANCE: No papers, to date, report on porous ureteral stents, which we propose as a new strategy for improved urinary drainage. The highly porous chitosan stents of our study are manufactured by radial, bi-directional freeze casting. Cyclic compression tests on fully-hydrated porous stents revealed high stent resilience and close to full recovery upon unloading. The drainage performance of the chitosan is evaluated, using effective viscosity in addition to volumetric flow and flux, and compared to that of the straight portion of a commercial 8 Fr double-J stent. The performance of the porous stent improves considerably more (47.5%) than that of the 8 Fr stent (30.6%) upon removal from the tube, illustrating the effectiveness of the radially aligned porosity for drainage. While further studies are required to explore other potential benefits of the porous stent design such as antimicrobial behavior, drug release, and biodegradability, we conclude that the newly-developed porous chitosan ureteral stent has considerable potential as a medical device.

Combination Susceptibility Testing of Common Antimicrobials in Vitro and the Effects of Sub-MIC of Antimicrobials on Staphylococcus aureus Biofilm Formation

The current study was conducted to evaluate the antibacterial combination efficacies, and whether the sub-inhibitory concentrations (sub-MIC) of antibiotics can influent on the biofilm formation of S. aureus. The minimum inhibitory concentration (MIC) of common antibacterial drugs was determined in vitro against clinical isolates of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pasteurella multocida (P. multocida) alone and in combination with each other by using the broth microdilution method and the checkerboard micro-dilution method analyzed with the fractional inhibitory concentration index (FICI), respectively. Regarding these results, antibacterial drug combinations were categorized as synergistic, interacting, antagonistic and indifferent, and most of the results were consistent with the previous reports. Additionally, the effects of sub-MIC of seven antimicrobials (kanamycin, acetylisovaleryltylosin tartrate, enrofloxacin, lincomycin, colistin sulfate, berberine, and clarithromycin) on S. aureus biofilm formation were determined via crystal violet staining, scanning electron microscopy (SEM) and real-time PCR. Our results demonstrate that all antibiotics, except acetylisovaleryltylosin tartrate, effectively reduced the S. aureus biofilm formation. In addition, real-time reverse transcriptase PCR was used to analyze the relative expression levels of S. aureus biofilm-related genes such as sarA, fnbA, rbf, lrgA, cidA, and eno after the treatment at sub-MIC with all of the six antimicrobials. All antibiotics significantly inhibited the expression of these biofilm-related genes except for acetylisovaleryltylosin tartrate, which efficiently up-regulated these transcripts. These results provide the theoretical parameters for the selection of effective antimicrobial combinations in clinical therapy and demonstrate how to correctly use antibiotics at sub-MIC as preventive drugs.

Increased therapeutic efficacy of combination of azithromycin and ceftazidime on Pseudomonas aeruginosa biofilm in an animal model of ureteral stent infection

Background

Infection caused by ureteral stent indwelling is one of the most difficult medical problems, since once bacteria reside in biofilms they are extremely resistant to antibiotics as well as to the host immune defences. In this study we assessed the in vitro and in vivo efficacy of azithromycin and ceftazidime in preventing ureteral stent infection by Pseudomonas aeruginosa.

Results

The susceptibility testing with adherent bacteria showed that the biofilm was strongly inhibited by azithromycin treatment, ceftazidime against adherent bacteria in the presence of azithromycin showed the minimum inhibitory concentrations (MICs) and minimum bacteriocidal concentrations (MBCs) dramatically lower than those obtained in the absence of azithromycin. Moreover, ceftazidime plus azithromycin reduced twitching motility and production of rhamnolipid. For the single-treatment groups, in vivo intravenous injection of ceftazidime showed the highest inhibitory effect on bacterial load. Azithromycin prophylactic injection combined with ceftazidime showed increased inhibitory effect on bacterial load than that of each single antibiotic.

Conclusions

Combination of azithromycin and ceftazidime effectively prevent the formation of biofilm and reduced bacteria load of Pseudomonas aeruginosa compared to separate treatment of either of these two antibiotics. This combined treatment option have the potential to contribute to the success of Pseudomonas biofilm elimination in the clinical environment.

Draft Genome Sequence of a Pseudomonas aeruginosa Strain Able To Decompose N , N -Dimethyl Formamide

Pseudomonas aeruginosa is a Gram-negative bacterium, which uses a variety of organic chemicals as carbon sources. Here, we report the genome sequence of the Cu1510 isolate from wastewater containing a high concentration of N,N-dimethyl formamide.

Advances in ureteral stents

Ureteral stents are commonly used in urology. Every urologist is familiar with the problems that are associated with stents including infection, encrustation, and bothersome symptoms. These problems limit and affect the use of ureteral stents which are necessary, even in light of the problems they can cause. New designs such as a helically cut ureteral stent which is designed to stretch and conform to the ureter is designed to improve comfort. Drug-eluting designs with an antimicrobial (triclosan) are designed to reduce bacterial adherence to ureteral stents. Chlorhexidine, an antiseptic, has been incorporated into a stent and held in place by a slow release varnish to prevent biofilm formation. Combinations of antibiotics coated directly on the stent and administered systemically have been shown to reduce stent colonization both in vitro and in vivo. Gel-based ureteral stents were also showed to reduce bacterial infection and colonization. Bioabsorbable materials have also been designed to reduce infection, symptoms and prevent the forgotten stent syndrome. Newer designs including stents based on guidewire technology, gels, and a combination of self-expanding wire stents with polymer films are reviewed. There is hope on the horizon that new stents will be able to effectively tackle problems that are often seen with ureteral stents.

Ureteral stent technology: Drug-eluting stents and stent coatings

Ureteral stents are commonly used following urological procedures to maintain ureteral patency. However, alongside the benefits of the device, indwelling stents frequently cause significant patient discomfort (pain, urgency, frequency) and can become encrusted and infected. The importance of these sequelae is that they are not only bothersome to the patient but can lead to significant morbidity, urinary retention, ureteral damage, recurrent infections, pyelonephritis and sepsis. When these problems occur, stent removal or replacement alongside antibiotic, analgesic and/or other symptom-modifying therapies are essential to successfully treat the patient. In an attempt to prevent such morbidity, numerous approaches have been investigated over the past several decades to modify the stent itself, thereby affecting changes locally within the urinary tract without significant systemic therapy. These strategies include changes to device design, polymeric composition, drug-elution and surface coatings. Of these, drug-elution and surface coatings are the most studied and display the most promise for advancing ureteral stent use and efficacy. This article reviews these two strategies in detail to determine their clinical potential and guide future research in the area.

A novel rat model of catheter-associated urinary tract infection

PURPOSE

The authors aimed to establish a rat model of catheter-associated UTIs using a complete urethral catheter. Bacterial growth in biofilms on urethral catheters was analyzed using standard culture methods to validate this model.

METHODS

A total of 15 rats were divided into the following three groups according to the duration of indwelling catheter placement: a 2-week group (n = 5, group 1), a 4-week group (n = 5, group 2), and a 6-week group (n = 5, group 3). A urethral catheter was inserted with the distal end buried just beneath the urethra, and it was fixed inside of the urethra with a single suture starting at the vagina so that the suture knot was hidden inside of the vagina, preventing the rats from biting it off. A standard culture method was used to analyze bacterial growth in the biofilms.

RESULTS

All 15 urethral catheters were intact at the end of the experiment. Pseudomonas aeruginosa, Escherichia coli, Enterococcus spp., Enterococcus faecalis, and Corynebacterium spp. were identified in the biofilms on the urethral catheters.

CONCLUSION

Our rat UTI model consisting of a complete urinary catheter is feasible. Our study may provide fundamental data for future biofilm studies incorporating molecular techniques, and even clinical studies.

Antimicrobial efficacy of combined clarithromycin plus daptomycin against biofilms-formed methicillin-resistant Staphylococcus aureus on titanium medical devices

In vitro efficacy of combined eradication therapy with clarithromycin and daptomycin against biofilm-formed methicillin-resistant Staphylococcus aureus on the orthopedic titanium devices was evaluated. The bactericidal effect of this antibiotic was investigated by a re-culture test, the scanning electron microscopy, and fluorescence microscopy using a double-staining dyes. Clarithromycin decreased the amount to half in 24 h. Although MRSA biofilms were not eradicated with clarithromycin or daptomycin alone, clarithromycin combined with daptomycin was useful to sterilize titanium devices within 72 h. This in vitro study showed that combined treatment with clarithromycin plus daptomycin is useful to eradicate staphylococcal biofilms formed on orthopedic devices.

From in vitro to in vivo Models of Bacterial Biofilm-Related Infections

The influence of microorganisms growing as sessile communities in a large number of human infections has been extensively studied and recognized for 30–40 years, therefore warranting intense scientific and medical research. Nonetheless, mimicking the biofilm-life style of bacteria and biofilm-related infections has been an arduous task. Models used to study biofilms range from simple in vitro to complex in vivo models of tissues or device-related infections. These different models have progressively contributed to the current knowledge of biofilm physiology within the host context. While far from a complete understanding of the multiple elements controlling the dynamic interactions between the host and biofilms, we are nowadays witnessing the emergence of promising preventive or curative strategies to fight biofilm-related infections. This review undertakes a comprehensive analysis of the literature from a historic perspective commenting on the contribution of the different models and discussing future venues and new approaches that can be merged with more traditional techniques in order to model biofilm-infections and efficiently fight them.

Efficacy of clarithromycin on biofilm formation of methicillin-resistant Staphylococcus pseudintermedius

BACKGROUND

Surgical site infections (SSIs) caused by biofilm-forming methicillin-resistant Staphylococcus pseudintermedius (MRSP) have emerged as the most common hospital-acquired infections in companion animals. No methods currently exist for the therapeutic remediation of SSIs caused by MRSP in biofilms. Clarithromycin (CLA) has been shown to prevent biofilm formation by Staphylococcus aureus. This study aims to assess the in vitro activity of CLA in eradicating MRSP biofilm formation on various materials.

RESULTS

Quantitative assay results (P = 0.5126) suggest that CLA does not eradicate MRSP biofilm formation on polystyrene after 4 - 24 h growth periods. Scanning electron micrographs confirmed that CLA did not eradicate MRSP biofilm formed on orthopaedic implants.

CONCLUSIONS

By determining the in vitro characteristics and activities of MRSP isolates alone and against antibiotics, in vitro models of biofilm related infections can be made. In vitro data suggests that CLA does not effectively eradicate S. pseudintermedius biofilms in therapeutic doses.

Macrolides decrease the minimal inhibitory concentration of anti-pseudomonal agents against Pseudomonas aeruginosa from cystic fibrosis patients in biofilm

BACKGROUND

Biofilm production is an important mechanism for bacterial survival and its association with antimicrobial resistance represents a challenge for the patient treatment. In this study we evaluated the in vitro action of macrolides in combination with anti-pseudomonal agents on biofilm-grown Pseudomonas aeruginosa recovered from cystic fibrosis (CF) patients.

RESULTS

A total of 64 isolates were analysed. The biofilm inhibitory concentration (BIC) results were consistently higher than those obtained by the conventional method, minimal inhibitory concentration, (MIC) for most anti-pseudomonal agents tested (ceftazidime: P = 0.001, tobramycin: P = 0.001, imipenem: P < 0.001, meropenem: P = 0.005). When macrolides were associated with the anti-pseudomonal agents, the BIC values were reduced significantly for ceftazidime (P < 0.001) and tobramycin (P < 0.001), regardless the concentration of macrolides. Strong inhibitory quotient was observed when azithromycin at 8 mg/L was associated with all anti-pseudomonal agents tested in biofilm conditions.

CONCLUSIONS

P. aeruginosa from CF patients within biofilms are highly resistant to antibiotics but macrolides proved to augment the in vitro activity of anti-pseudomonal agents.