Gábor Rappai

Effect of Antibiotics on Cell Surface Hydrophobicity of Bacteria Causing Orthopedic Wound Infections

Background: Despite antibiotic prophylaxis and treatment, the incidence of wound infections in orthopedic surgery is significant. Postoperative wound infection is a multifactorial process, which can be modified by several bacterial factors. Cell surface hydrophobicity of bacteria is a very important physicochemical feature, which has a great influence on the ability of bacteria to adhere to the surface of host cells or medical implants. Methods: In this study, the hydrophobic properties of thirteen bacterial strains (coagulase-negative staphylococci, Staphylococcus aureus and Pseudomonas aeruginosa) isolated from patients with postoperative deep wound infections following orthopedic procedures were determined by the salt aggregation test. Results were compared to the hydrophobicity of three Hungarian standard bacterial strains. The modifying effect of four antibiotics (cefuroxime, cefotaxime, amoxicillin combined with clavulanic acid and amikacin) – applied most often in our Department for prophylaxis and treatment of patients – were analyzed. Results: The cell surface hydrophobicity of certain strains showed considerable changes after antibiotic treatment. These alterations indicated the decrease in hydrophobicity. Supra-inhibitory concentrations (2× minimum inhibitory concentrations, MIC) of the antibiotics were able to induce more frequent alterations in hydrophobicity than sub-inhibitory (0.5× MIC) levels. Conclusions: Alterations in cell surface hydrophobicity caused by antibiotics can modify the adhesion process and thus the pathogenicity of bacterial strains. These changes should be taken into consideration in the management of proper antibiotic prophylaxis and in the treatment of orthopedic patients.

Index-Building in a System of Interdependent Variables: The Penalty for Bottleneck

While the importance and the popularity of indices able to capture complex categories and the multidimensional nature of a particular phenomenon have been increasing, most approaches are still not able to provide plausible policy recommendations. The Penalty for Bottleneck (PFB) methodology is based on the assumption that the performance of the system depends on the weakest link, i.e., the variable that has the lowest value. This approach deviates from the most frequently applied method of calculating the arithmetic averages of the variables, which explicitly assumes perfect substitutability and, hence, provides potentially false policy implications. The resulting PFB-based policy recommendation is clear: the bottleneck should be improved first because it has a magnifying effect on the other indicators in the system. The PFB methodology is applied to the Heritage Foundation Index of Economic Freedom data. We show how the original methodology and the PFB methodology differ from each other by using a conservative logarithmic penalty function.

Interaction between CTLA4 gene and IBD5 locus in Hungarian Crohn’s disease patients

Backgrounds and aimsThe IGR2198a_1 and IGR2096a_1 variants of the IBD5 region were found to be associated with Crohn’s disease (CD) in the Hungarian population, while IGR2230a_1 does not seem to confer risk for the disease. In the present study, our aim was to investigate the statistical interaction of these three IBD5 polymorphisms with the +49 A/G substitution within the cytotoxic T lymphocyte antigen-4 (CTLA4) gene, detected previously as neutral gene variant in Hungarian IBD patients.MethodsA total of 305 unrelated subjects with CD and 310 healthy controls were genotyped with PCR-RFLP methods.ResultsIn contrast with single gene effects, after genotype stratification, the IGR2198a_1 C and IGR2096a_1 T variants were found to confer susceptibility only in subjects with CTLA4 +49 AA genotype (P = 0.008; OR = 1.86 and P = 0.016; OR = 1.74, respectively), for IGR2230a_1 no such effect on disease risk could be demonstrated.ConclusionAnalysis of specific genotype combinations unfolded a possible association between the CTLA4 +49 A/G substitution and two of the observed IBD5 variants with respect to disease risk.

Effect of antibiotic treatment on bacterial attachment to a DePuy Enduron orthopedic implant.

Background: The increasing incidence of bacterial infections in orthopedic surgery might be related to the increasing application of artificial devices. In most cases, bacteria multiply on the surface of implants in biofilms. Poor penetration of antibiotics, frequent necessity of prosthesis removal, chronic processes and financial costs emphasize the significance of preventive measures. Method: Adhesion of bacterial strains (two Staphylococcus aureus, two coagulase-negative staphylococci and two Pseudomonas aeruginosa strains isolated from orthopedic patients’ wounds) to the surface of a polyethylene cupwas investigated using an ultrasonic method. Results were compared to the adhesive ability of three Hungarian standard strains. The effect of antibiotic treatment (cefuroxime, cefotaxime, amoxicillin with clavulanic acid and amikacin) has been examined. Results: The staphylococcal strains showed significantly higher adhesive ability than Pseudomonas strains. Antibiotic treatment significantly reduced the attachment of bacteria. The higher the concentration of the antibiotics, the higher was the decrease in bacterial adhesion. Conclusions: Antibiotic prophylaxis was proven to be effective against bacterial adhesion, and, if applied at the proper time at the highest tolerable dose, it might prevent the formation of biofilms.

Analyzing the Impact of Process Improvement on Lot Sizes in JIT Environment When Capacity Utilization Follows Beta Distribution

Even after many years one kind picture still floating in my eyes: I see professor Szidarovszky, facing the blackboard, sponge and chalk at the upheld left and right hands, and writing and cleaning the lines simultaneously he put on the table, to fill up our heads with numerical methods. This style expresses his very dynamic and efficient research work at the same time, and hopefully this paper indicates that his efforts have not been useless as numerical methods are very intensively used in order to characterize the nature of lot sizing problems in JIT environment. In JIT environment the jidoka principle empowers employees to signal quality problems, and these result in frequent stoppages. This way we consider the output of the assembly line random variable that follows Beta distribution, but with low beta values. For specific beta values we derive explicit forms of the expected values of the inventory related and the annual total costs as function of alpha, the other parameter of the Beta distribution. But increasing alpha expresses increasing process quality. We found that increasing process quality decreases the expected annual cost, and the explicit forms give the saved cost volumes. Two simulation analyses are conducted to reveal the development of the variance of annual costs. The estimations of the variance of the minimum total annual costs indicate that with process improvement the variance of the minimum of the annual total costs will decrease.