In vitro susceptibility to fosfomycin in clinical and environmental extended-spectrum beta-lactamase producing and/or ciprofloxacin-non-susceptible Escherichia coli isolates

Extended-spectrum beta-lactamase producing and ciprofloxacin-non-susceptible Escherichia coli are clinical and environmental issues. We evaluated the susceptibility profile of fosfomycin in non-susceptible E. coli isolated from urine and the environment. We measured the activity of fosfomycin against 319 and 36 E. coli strains from urine and environmental isolates, respectively, collected from rivers. Fosfomycin resistance profiles were investigated using the minimal inhibitory concentration (MIC), according to the Clinical and Laboratory Standards Institute (CLSI) and the European Committee for Antimicrobial Susceptibility Testing (EUCAST) guidelines. Antibiotic susceptibility testing revealed that 5% and 6.6% of urine samples were non-susceptible to fosfomycin according to CLSI and EUCAST guidelines, respectively. The fosfomycin MIC50/90 was 0.5/4 mg/L. Of the 36 E. coli isolates from river water, 11.1% and 13,8% were non-susceptible to fosfomycin according to CLSI and EUCAST, respectively (range ≤0.25 ≥512 mg/L). All the isolates with MIC ≥512 mg/L for fosfomycin showed the fosA3 gene. Fosfomycin resistance was more frequent in the environment than in clinical samples.

Different concentrations of vancomycin with gentamicin loaded PMMA to inhibit biofilm formation of Staphylococcus aureus and their implications

BACKGROUND

This study aimed to evaluate different concentrations of vancomycin and/or gentamicin loaded polymethylmethacrylate (PMMA) against biofilm formation of Staphylococcus aureus.

METHODS

Biofilm production of S. aureus in PMMA loaded with different concentrations of vancomycin and gentamicin were evaluated by quantitative analysis of biofilm cells, scanning electronic microscopy, viability assay, Fourier transform infrared spectroscopy, and checkerboard. Statistical analysis was performed by Mann Whitney test. The difference in colony forming units per mL was significant when p < 0.05.

RESULTS

All loaded PMMA presented a reduction in the number of colony forming units per mL (p < 0.05). The gentamicin-loaded PMMA could inhibits the grown of sessile cells (p < 0.05), where the group vancomycin 4 g + gentamicin 500 mg presented a better result. The Fourier transform infrared spectra showed no significant differences, and checkerboard of vancomycin and gentamicin showed synergism.

CONCLUSION

Effects against adherence and bacterial development in PMMA loaded with antibiotics were mainly seen in the group vancomycin 4 g + gentamicin 500 mg, and synergic effect can be applied in antibiotic-loaded cement.

Comparison of amphotericin B lipid complex, deoxycholate amphotericin B, fluconazole, and anidulafungin activity against Candida albicans biofilm isolated from breakthrough candidemia

INTRODUCTION

Biofilm formation causes virulence and resistance in Candida albicans. However, little is known about breakthrough candidemia isolates. We evaluated the antifungal activity of fluconazole, anidulafungin, deoxycholate amphotericin B (dAMB), and amphotericin B lipid complex (ABLC) against biofilms of C. albicans isolated from patients with breakthrough candidemia.

METHODS

The present study used strains of C. albicans isolated from breakthrough and non-breakthrough candidemia patients (control group). The susceptibility of planktonic cells to amphotericin B, anidulafungin, and fluconazole was determined by broth microdilution. Antifungal activity in sessile cells was evaluated using the minimum biofilm eradication concentration (MBEC), metabolic activity was estimated by reducing MTT, and biomass was estimated using crystal violet retention.

RESULTS

The planktonic strains were susceptible to amphotericin B, anidulafungin, and fluconazole, with minimum inhibitory concentrations of 1, ≤0.03, and 2mg/L, respectively. However, fluconazole and anidulafungin did not exert an antifungal effect on biofilms. Additionally, dAMB and ABCL reduced the metabolic activity and biomass. However, eradication was only achieved using 16mg/L dAMB. C. albicans isolates of breakthrough candidemia exhibited strong biofilm production, and the in vitro activity of available therapeutic options was poor.

CONCLUSION

In the present study, only dAMB and ABCL exhibited antibiofilm effects against sessile breakthrough candidemia isolates.

Evaluation of silver nanoparticle-impregnated PMMA loaded with vancomycin or gentamicin against bacterial biofilm formation

INTRODUCTION

Bone cement containing vancomycin or gentamicin is a therapeutic strategy for combating orthopedic infections: however, the activity of these antibiotics is narrow. Silver nanoparticles (AgNPs) are nanocomponents with a wide spectrum, including multidrug-resistant bacteria. In the present study, we aimed to evaluate the effect of AgNP-loaded polymethylmethacrylate (PMMA) on biofilm formation by Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus epidermidis.

METHODS

The effect of AgNP-loaded PMMA with and without vancomycin or gentamicin on biofilm production was quantitatively analyzed. S. aureus, E. coli, P. aeruginosa, and S. epidermidis were included as biofilm-producing microorganisms in the in vitro model.

RESULTS

AgNP-loaded PMMA with antibiotics reduced the number of colony-forming units (CFUs; p<0.001). However, AgNP-loaded PMMA alone did not significantly reduce biofilm formation.

CONCLUSION

Our study demonstrated the potential of AgNP-loaded PMMA. Notably, we observed that AgNP-loaded PMMA containing vancomycin or gentamycin exhibited significantly superior efficacy, with satisfactory activity against most biofilm-forming microbial agents examined.

Sonication as a tool for disrupting biofilms and recovering microorganisms in bladder catheters

INTRODUCTION

Urinary catheter-related infection is commonly associated with bacterial biofilm. The impact of anaerobes is unknown, but their detection in the biofilm on this device has not been previously reported. This study aimed to evaluate the capability to recovery strict, facultative, and aerobic microorganisms in patients using bladder catheters from ICUs using conventional culture, sonication, urinary analysis, and mass spectrometry.

METHODS

Parallel, sonicated bladder catheters from 29 critically ill patients were compared with their routine urine culture. Identification was performed using matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry.

RESULTS

The positivity rate in urine (n = 2, 3.4%) was lower than that in sonicated catheters (n = 7, 13.8%).

CONCLUSION

Bladder catheter sonication showed more positive culture results than urine samples for anaerobic and aerobic microorganisms. The role of anaerobes in urinary tract infection and catheter biofilm is discussed.

Antimicrobial Treatment of Staphylococcus aureus Biofilms

Staphylococcus aureus is a microorganism frequently associated with implant-related infections, owing to its ability to produce biofilms. These infections are difficult to treat because antimicrobials must cross the biofilm to effectively inhibit bacterial growth. Although some antibiotics can penetrate the biofilm and reduce the bacterial load, it is important to understand that the results of routine sensitivity tests are not always valid for interpreting the activity of different drugs. In this review, a broad discussion on the genes involved in biofilm formation, quorum sensing, and antimicrobial activity in monotherapy and combination therapy is presented that should benefit researchers engaged in optimizing the treatment of infections associated with S. aureus biofilms.

Pathogenesis of the Pseudomonas aeruginosa Biofilm: A Review

Pseudomonas aeruginosa is associated with several human infections, mainly related to healthcare services. In the hospital, it is associated with resistance to several antibiotics, which poses a great challenge to therapy. However, one of the biggest challenges in treating P. aeruginosa infections is that related to biofilms. The complex structure of the P. aeruginosa biofilm contributes an additional factor to the pathogenicity of this microorganism, leading to therapeutic failure, in addition to escape from the immune system, and generating chronic infections that are difficult to eradicate. In this review, we address several molecular aspects of the pathogenicity of P. aeruginosa biofilms.

Comparative study of decellularization techniques to obtain natural extracellular matrix scaffolds of human peripheral-nerve allografts

BACKGROUND

We hypothesize that adding sonication cycles to the process of decellularization of cadaveric human peripheral nerves will increase the removal of cell debris and myelin sheath, increasing their utility as allografts.

METHODS

Our aim of this study was to develop a decellularization protocol that allows the removal of cells and myelin sheath without detrimental effects on nerve architecture. Segments of ulnar and median nerves from human donors, isolated both before and after cardiac arrest, were subjected to two methods of decellularization: two-detergent-based (M1) and the same method with sonication added (M2). We evaluated the histology of unprocessed and decellularized nerves (n = 24 per group) for general morphology, presence of cell nuclei, nuclear remnants, collagen fibers, and myelin. We performed immunohistochemistry to verify the removal of Schwann cells associated with histomorphometry. We used scanning electron microscopy (EM) to evaluate the ultrastructure of both native and decellularized nerves. The efficacy of decellularization was assessed by analysis of genomic DNA.

RESULTS

Histology confirmed that both decellularization protocols were adequate and maintained natural nerve architecture. Scanning EM showed that 3D ultrastructural architecture also was maintained. Histomorphometric parameters showed a more complete removal of the myelin with the M2 protocol than with M1 (p = 0.009). Fiber diameter and density were not modified by decellularization methods.

CONCLUSIONS

Sonication can be a complementary method to decellularization of peripheral nerve allografts with sonication increasing the effectiveness of detergent-based protocols for the removal of unwanted cellular components from peripheral nerve allografts.

Evaluation of Staphylococcus aureus and Candida albicans biofilms adherence to PEEK and titanium-alloy prosthetic spine devices

BACKGROUND

Titanium and polyether-ether-ketone (PEEK) interbody cages are commonly used for spine fusion. Few data are known about bacterial and yeast biofilms formation in these implants. The aim of this study was to compare Staphylococcus aureus and Candida albicans biofilm formation in the surface of two different interbody devices used routinely in spine surgery.

METHODS

Six bodies of proof specimens of PEEK and titanium alloy were used for microbiological tests, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Experimental biofilm was produced with Staphylococcus aureus and Candida albicans, followed by quantitative analysis of planktonic cells and sessile cells. The comparison between the medians of biofilm quantification between the two models was performed using the Mann-Whitney test and considered the statistical difference for a p < 0.05.

RESULTS

In the S. aureus model, in both planktonic and sessile cell counts, titanium-alloy samples showed lower values for colony forming units per milliliter (UFC/mL) (p < 0.05). The evaluation through the optic density of planktonic and sessile cells showed lower values in the titanium-alloy samples, however, only statistically significant in planktonic cell count (p < 0.05). The count of planktonic yeast cells in PEEK was similar to titanium-alloy samples, while the count of sessile yeast cells in titanium alloy was lower when compared to PEEK (p < 0.05).

CONCLUSION

Titanium-alloy models were associated with less staphylococcal and Candida biofilm formation when compared with PEEK.

Disinfection protocol for human musculoskeletal allografts in tissue banking using hydrogen peroxide 30

Musculoskeletal allografts are used in reconstructive procedures, however, the risk of contamination with potential pathogens is possible, and safe transplantation requires multiple processing considerations. Hydrogen peroxide (H₂O₂) has commonly been used in bone washing because it can remove donor cells and eliminate antigens, pathogens, or cytotoxic agents from the matrix. The aim of this study was to evaluate the quantitative activity of H₂O₂ in a model of bone contamination with a high bacterial load to define the bioburden reduction. Twelve bone disc models were artificially contaminated with Staphylococcus aureus. The bones were treated with a washing process composed by antibiotics, 30% hydrogen peroxide, and 70% alcohol. Tryptic Soy Agar plates were directly inoculated with 100µL of each step of the washing process and colonies were counted in CFU/mL. Scanning electron microscopy was used for bone structural analysis before and after the washing process. After antibiotics, there was a drop of less than 1 log for cancellous bone and almost 1 log for cortical bone. However, after H₂O₂, there as a drop of 3 logs for cortical (p = 0.007), and 2 logs for cancellous bone (p = 0.063). The use of alcohol did not change the bioburden following H₂O₂ in cancellous and cortical bone. Despite the important drop of bacterial load, H₂O₂ was not enough to completely eradicate bacterial with this model of bioburden. H₂O₂ is useful in decontamination, but antibiotics have little activity, and alcohol is useless. The process is useful in decontamination up to 3 logs of bioburden.

Direct detection of microorganisms in sonicated orthopedic devices after in vitro biofilm production and different processing conditions

BACKGROUND

The gold standard for microbial detection in prosthetic joint infections is the multiple culture of the peri-prosthetic tissue. The fluid cultures after sonication can improve the recovery of the microorganisms.

OBJECTIVE

The aim of this study was to evaluate the sonication technique with a plastic bag and the effect of refrigeration on microorganism detection with conventional culturing, MALDI-TOF MS and qPCR assay on an orthopedic screw model.

METHODS

We produced biofilms of Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans on orthopedic screws, which were stored under different conditions and temperatures before sonication. After sonication, the mass spectrometry by MALDI-TOF, qPCR and culture protocols was performed using the sonicated fluid, for detecting the microorganisms involved in the biofilm.

RESULTS

The bacterial bioburden decreased by approximately one log after the refrigeration period, in the screws containing P. aeruginosa and S. aureus biofilms. All the microorganisms involved in the screw biofilms were detected with MALDI-TOF and qPCR. Significant reductions in CFU counts occurred only in groups stored in the plastic bag, indicating that changes in temperature and humidity may favor cell death. However, this variation is not important for this model as it did not affect the detection owing to the high counts obtained.

CONCLUSION

Microbial identification by MALDI-TOF in sonicated fluid is feasible. With qPCR, there were no differences between the detection in the screws processed immediately or after refrigeration. It is necessary to consider whether or not the refrigeration period would affect microbial recovery in an explanted prosthesis.

Determination of antibiotics and detergent residues in decellularized tissue-engineered heart valves using LC-MS/MS

Residual chemicals that are presented during tissue processing in human tissue banks can be a risk for the allograft recipient. Determine the residual concentrations of the antibiotics and detergent used in the process of human decellularized tissue-engineered heart valves stored in isotonic saline solution up to 18 months. A total of 24 human decellularized allografts were stored in sterile sodium chloride and analyzed immediately after the decellularization process (0 months) and after storage for 6, 12, and 18 months, which includes the use of sodium dodecyl sulfate (SDS) and antibiotics (cefoxitin, vancomycin hydrochloride, lincomycin hydrochloride, polymyxin B sulfate). These valves were used for suitability tests, the zone of inhibition evaluation, and direct contact cytotoxicity assay. The stock solution from 32 valves was used for LC-MS/MS analysis of antibiotics and SDS. Tissue samples from decellularized valves showed a zone of inhibition formation for S. aureus and B. subtilis, suggesting the presence of an inhibitory molecule in the tissue. Cytotoxicity tests were negative. Polymyxin B, vancomycin, and SDS were detected and quantified in human decellularized aortic and pulmonary allografts during all periods of the study. There were no traces of residual cefoxitin and lincomycin in the tissue stock solution. We found residual concentrations of the antibiotics and detergent used in the process of human decellularized tissue-engineered heart valves stored in isotonic saline solution up to 18 months.

Histological and Biomechanical Characteristics of Human Decellularized Allograft Heart Valves After Eighteen Months of Storage in Saline Solution

Background: The best storage preservation method for maintaining the quality and safety of human decellularized allograft heart valves is yet to be established. Objective: The aim of the present study was to evaluate the stability in terms of extracellular matrix (ECM) integrity of human heart valve allografts decellularized using sodium dodecyl sulfate-ethylenediaminetetraacetic acid (SDS-EDTA) and stored for 6, 12, and 18 months. Methods: A total of 70 decellularized aortic and pulmonary valves were analyzed across different storage times (0, 6, 12, and 18 months) for solution pH measurements, histological findings, cytotoxicity assay results, biomechanical test results, and microbiological suitability test results. Continuous data were analyzed using one-way analysis of variance comparing the follow-up times. Results: The pH of the stock solution did not change during the different time points, and no microbial growth occurred up to 18 months. Histological analysis showed that the decellularized allografts did not present deleterious outcomes or signs of structural degeneration in the ECM up to 12 months. The biomechanical properties showed changes over time in different aspects. Allografts stored for 18 months presented lower tensile strength and elasticity than those stored for 12 months (p < 0.05). The microbiological suitability test suggested no residual antimicrobial effects. Conclusion: Changes in the structure and functionality of SDS-EDTA decellularized heart valve allografts occur after 12 months of storage.

Detection and quantification of human immunodeficiency virus and hepatitis C virus in cadaveric tissue donors using different molecular tests

BACKGROUND

Tissues from cadaveric donors are used in several clinical circumstances, and the transmission of infectious diseases has been reported. Cadaveric donor (CD) blood sample analysis is challenging due to its poor quality. However, studies have demonstrated the usefulness of molecular based methods, and the lack of studies using available commercial molecular tests was reported.

OBJECTIVE

The aim of this study was to evaluate the performance, specificity, sensitivity, and accuracy of different commercial molecular tests for HIV and HCV detection and quantification in CD through spiked samples.

STUDY DESIGN

20 CD and 20 blood donor samples were tested using 1,000 copies/mL and 1,000 IU/mL of lyophilized standards of HIV and HCV, respectively. Samples were analyzed by different molecular kits: XPERT HCV Viral Load and HIV-1 (Cepheid), COBAS® TaqMan® HIV-1 and COBAS® TaqMan® HCV Test, v2.0 (Roche), and artus® HI Virus-1 QS-RGQ and artus® HCV RG RT-PCR Kit (Qiagen).

RESULTS

HIV and HCV in CD were detected by RT-PCR-based quantitative kits. The tests performed by the Cepheid and the Roche kits showed the most accurate, sensitive and specific results, however, a wide variability between the assays and kits was observed. The Qiagen kits did not demonstrate satisfactory results.

CONCLUSIONS

CD evaluation showed great variability. The Cepheid and Roche kits were more sensitive for detecting HIV on CD and Cepheid was the most efficient kit for HCV quantification in CD. The Roche and Cepheid kits can be used to screen tissue donors for HIV and HCV.

Anaerobic bioburden in transport solution of human cardiovascular tissues

Although reports of infections caused by anaerobes after tissue transplantation are uncommon, contamination of allografts may result in substantial complications. Anaerobic incubation and testing of organ transport solution (TS) are not routine. The aim of this study was to determine the bioburden of strict anaerobic bacteria and oxygen tension of heart-TS. Forty TS from different donors were evaluated cultured using membrane filtration (MF), direct inoculation on broth and automated blood culture bottle (ABCB). Bacterial identification was performed by MALDI-TOF. The transport conditions were simulated to verify the bacterial recovery. A sterile bag fulfilled with 250 ml^-1 of sterile saline was spiked with 100 CFU ml^-1 of Clostridium perfringens and the fluid recovered 0 h, 1 h, 2 h, 6 h, 12 h, 24 h and 48 h for culture and oxygen measurement. Strict anaerobic bacteria were not isolated in heart-TS. The recovery of C.perfringens spiked in heart-TS was 100% using automated blood culture bottles. MF method detected >100 CFU only after 6 h of spiking. The manual culture was not able to recover C.perfringens after the process. The percentage of O₂ measures varied from 77.6 to 87.9%. MF or ABCB are better than direct inoculation for recovery of anaerobes from heart-TS. Although all samples from heart donors were negative for anaerobes (probably due to low incidence of contamination), C.perfringens were all recovered in the simulated transport condition.

Decellularization as a method to reduce calcification in bovine pericardium bioprosthetic valves

OBJECTIVES

Decellularization is an alternative method for processing biological tissues with decreased antigenicity and resistance to calcification. The aim of this study was to characterize the properties of decellularized (dCell) bovine pericardium fixed with 0.1% glutaraldehyde (GA) and to evaluate outcomes of bioprosthetic valves constructed with this tissue when implanted in the mitral position of juvenile sheep.

METHODS

Bioprosthetic mitral valves were constructed with fresh bovine pericardium fixed in 0.5% GA (control group) or dCell bovine pericardium fixed in 0.1% GA (study group). Before implantation, samples were submitted to histological (haematoxylin-eosin, Movat and 4',6-diamidino-2-phenylindole), biochemical (residual deoxyribonucleic acid and α-gal epitopes) and biomechanical characterization. Valves were implanted (n = 8 in each group) as a mitral valve replacement for 180 days in sheep and explants were re-evaluated histologically and for calcification with radiological studies and calcium content determination.

RESULTS

Unimplanted dCell pericardia exhibited a well-preserved extracellular matrix with absence of cells, a 77% reduction in deoxyribonucleic acid levels and with no detectable α-gal epitopes. When compared to controls, they had lower ultimate tensile strength (7.3 ± 5.4 vs 10.2 ± 3.0 mPa, P = 0.04) and greater percentage elongation in the longitudinal direction (29 ± 6.5% vs 23.8 ± 5.1%, P = 0.02). After 180 days in mitral position, dCell valves showed pliable leaflets without macroscopic signs of calcification. Histologically, dCell leaflets had intact collagen fibres, better tissue remodelling and a significant 89% reduction in calcium content.

CONCLUSIONS

This study demonstrates that bioprosthetic valves constructed with dCell bovine pericardium fixed in low GA concentration were resistant to calcification and may thereby improve long-term durability of the tissue.

Human Heart Explant-Derived Extracellular Vesicles: Characterization and Effects on the In Vitro Recellularization of Decellularized Heart Valves

Extracellular vesicles (EVs) are particles released from different cell types and represent key components of paracrine secretion. Accumulating evidence supports the beneficial effects of EVs for tissue regeneration. In this study, discarded human heart tissues were used to isolate human heart-derived extracellular vesicles (hH-EVs). We used nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM) to physically characterize hH-EVs and mass spectrometry (MS) to profile the protein content in these particles. The MS analysis identified a total of 1248 proteins. Gene ontology (GO) enrichment analysis in hH-EVs revealed the proteins involved in processes, such as the regulation of cell death and response to wounding. The potential of hH-EVs to induce proliferation, adhesion, angiogenesis and wound healing was investigated in vitro. Our findings demonstrate that hH-EVs have the potential to induce proliferation and angiogenesis in endothelial cells, improve wound healing and reduce mesenchymal stem-cell adhesion. Last, we showed that hH-EVs were able to significantly promote mesenchymal stem-cell recellularization of decellularized porcine heart valve leaflets. Altogether our data confirmed that hH-EVs modulate cellular processes, shedding light on the potential of these particles for tissue regeneration and for scaffold recellularization.

Risk factors associated with contamination of allograft valves in a tissue bank

The contamination of the transport solution used in cardiovascular allografts can occur from different sources. Risk factors associated with positive microbiological test of transport solution have not been reported previously. This study aimed to determine the risk factor for contamination of transport solution used in the heart valve allografts stored in a Brazilian tissue bank. This retrospective study was conducted on all donors of cardiovascular allografts stored in a tissue bank from December 2008 to December 2017. Microbiological cultures for aerobic and anaerobic bacteria, fungi/yeasts were carried out in TS. Clinical variables were included. From 1001 transport solution, 52% were contaminated. A total of 770 microorganisms were identified, and Staphylococcus spp. was identified in 248 isolates (32.2%). Skin bacteria from skin microbiota were the most commonly identified microorganisms (Staphylococcus spp., Cutibacterium spp., Corynebacterium spp., and Bacillus spp.), occurring in 49.6%. The presence of a diagnosis of healthcare-associated infection was not associated with skin contamination (odds ratio [OR] 0.62 [0.41-0.94]; p = 0.014). Conditions like fever, use of antibiotics, and leukocytosis were less likely associated with contamination of transport solution. A longer warm ischemic time was associated with higher frequency of contamination. In the multivariable analysis, warm ischemic time was independently associated with contamination, and antibiotic therapy was a factor that decreased the rate of contamination (p < 0.05). Contamination of transport solution is associated with modifiable risk factors, such as warm ischemic time. Measures to minimize contamination should be employed to avoid unnecessary tissue discharges.

Experimental procedures for decontamination and microbiological testing in cardiovascular tissue banks

IMPACT STATEMENT

Sterility testing is a critical issue in the recovery, processing, and release of tissue allografts. Contaminated allografts are often discarded, increasing costs, and reducing tissue stocks. Given these concerns, it is important to determine the most effective methodology for sterility testing. This work provides an overview of microbiological methods for sampling and culturing donor grafts for cardiovascular tissue banking.

Conventional culture method and qPCR using 16S rDNA for tissue bank: a comparison using a model of cardiac tissue contamination

Real-time polymerase chain reaction (qPCR) using 16S rDNA is an alternative to conventional culture-based tests. The aim of this study was to compare the conventional culture method with qPCR using 16S rDNA in a model of cardiac tissue contamination. Samples of cardiac tissue for artificial contamination with Escherichia coli and control samples were submitted for DNA extraction, which was conducted by selective and alkaline lysis and purification steps. A standard curve for 16S rDNA was constructed to determine the efficiency and analytical sensitivity of the assay in concentrations from 10⁶ to 10² c.f.u. ml^-1 using TaqMan Master Mix. 16S rDNA was detected in all contaminated samples; however, it was not detected in the the final washing step solution of the sample with a bioburden of 10² c.f.u. ml^-1. Using qPCR is a potential alternative to conventional culture for microbiological safety testing of allograft tissues for biobanking, reducing the time and labour input required.

Comparison of two surgical techniques for creating an acute myocardial infarct in rats

Objective

To perform a comparative assessment of two surgical techniques that are used creating an acute myocardial infarc by occluding the left anterior descending coronary artery in order to generate rats with a left ventricular ejection fraction of less than 40%.

Methods

The study was completely randomized and comprised 89 halothane-anaesthetised rats, which were divided into three groups. The control group (SHAM) comprised fourteen rats, whose left anterior descending coronary artery was not occluded. Group 1 (G1): comprised by 35 endotracheally intubated and mechanically ventilated rats, whose left anterior descending coronary artery was occluded. Group 2 (G2): comprised 40 rats being manually ventilated using a nasal respirator whose left anterior descending coronary artery was occluded. Other differences between the two techniques include the method of performing the thoracotomy and removing the pericardium in order to expose the heart, and the use of different methods and suture types for closing the thorax. Seven days after surgery, the cardiac function of all surviving rats was determined by echocardiography.

Results

No rats SHAM group had progressed to death or had left ventricular ejection fraction less than 40%. Nine of the 16 surviving G1 rats (56.3%) and six of the 20 surviving G2 rats (30%) had a left ventricular ejection fraction of less than 40%.

Conclusion

The results indicate a tendency of the technique used in G1 to be better than in G2. This improvement is probably due to the greater duration of the open thorax, which reduces the pressure over time from the surgeon, allowing occlusion of left anterior descending coronary artery with higher accuracy.