[Corneal biomechanics before and after cross-linking in patients with keratoconus]. / Die Biomechanik der Hornhaut vor und nach Crosslinking bei Patienten mit Keratokonus.

OBJECTIVE: The aim of this study was to analyze the effect of corneal cross-linking (CXL) on corneal biomechanics and visual acuity. PATIENTS AND METHODS: The examination results before and after CXL in 56 eyes of 56 patients between 2017 and 2021 were evaluated retrospectively. The last preoperative examination was compared to the postoperative follow-up values after 6 and 12 months. The main outcome measures included various biomechanical parameters from the Corvis ST (CST), Pentacam and the visual acuity (logMAR, "logarithm of the Minimal Angle of Resolution"). For longitudinal evaluation, a general linear model for repeated measurements was used. A p-value of less than 0.05 was considered to show a statistically significant result. Bonferroni correction was applied for multiple comparisons. RESULTS: The maximum corneal refractive power Kmax decreased slightly without statistical significance from 57.1 ± 6.1 diopters (dpt) to 56.6 ± 6.3 dpt after 6 months (p = 0.076) and 56.8 ± 6.6 dpt after 12 months (p = 0.443). The Pentacam parameter Belin/Ambrósio Enhanced Ectasia Total Deviation Display (BAD D) showed a statistically significant increase from the preoperative value of 8.4 ± 3.7 to the postoperative value of 9.1 ± 3.6 after 6 months (p < 0.001) and to 8.9 ± 3.5 after 12 months (p = 0.051). The CST parameter Ambrósio's relational thickness to horizontal profile (ARTh) decreased statistically significantly from 229.9 ± 109.6 to 204.8 ± 84.9 at 6 months (p = 0.017) and 205.3 ± 93.7 at 12 months (p = 0.022). The CST parameter stiffness parameter A1 (SP A1) increased slightly from the preoperative value 69.9 ± 17.2 to 70.4 ± 17.2 after 6 months (p = 1) and 71 ± 18.2 after 1 year (p = 1). Mean best-corrected visual acuity (logMAR) showed an improvement from 0.39 ± 0.3 to 0.34 ± 0.3 at 6 months (p = 0.286) and to 0.31 ± 0.3 at 12 months (p = 0.077). Regarding the ABCD classification, the parameters were determined preoperatively with an average of A2B3C1D2. They showed the same value of A2B3C1D2 after 6 and 12 months. CONCLUSION: In progressive keratoconus, corneal cross-linking has the potential to positively influence the biomechanics of the cornea and visual acuity as a low complication treatment option.

Characterization of Amino Acid Substitutions in the Two-Component Regulatory System AdeRS Identified in Multidrug-Resistant Acinetobacter baumannii.

In Acinetobacter baumannii, resistance-nodulation-cell division (RND)-type efflux is a resistance mechanism of great importance since it contributes to reduced susceptibility to multiple antimicrobial compounds. Some mutations within the genes encoding the two-component regulatory system AdeRS appear to play a major role in increased expression of the RND efflux pump AdeABC and, consequently, in reduced antimicrobial susceptibility, as they are commonly observed in multidrug-resistant (MDR) A. baumannii. In the present study, the impact of frequently identified amino acid substitutions, namely, D21V and D26N in AdeR and T156M in AdeS, on adeB expression, efflux activity, and antimicrobial susceptibility was investigated. Reverse transcription-quantitative PCR (qRT-PCR) studies revealed significantly increased adeB expression caused by D26N (AdeR) and T156M (AdeS). In addition, accumulation assays have shown that these mutations induce increased efflux activity. Subsequently, antimicrobial susceptibility testing via agar dilution and broth microdilution confirmed the importance of these substitutions for the MDR phenotype, as the MICs for various antimicrobials of different classes were increased. In contrast, the amino acid substitution D21V in AdeR did not lead to increased adeB expression and did not reduce antimicrobial susceptibility. This study demonstrates the impact of the D26N (AdeR) and T156M (AdeS) amino acid substitutions, highlighting that these regulators represent promising targets for interfering with efflux activity to restore antimicrobial susceptibility. IMPORTANCE The active efflux of antimicrobials by bacteria can lead to antimicrobial resistance and persistence and can affect multiple different classes of antimicrobials. Efflux pumps are tightly regulated, and their overexpression can be mediated by changes in their regulators. Identifying these changes is one step in the direction of resistance prediction, but it also opens the possibility of targeting efflux pump regulation as a strategy to overcome antimicrobial resistance. Here, we have investigated commonly found changes in the regulators of the main efflux pumps in Acinetobacter baumannii.

Comparison of the Acinetobacter baumannii Reference Strains ATCC 17978 and ATCC 19606 in Antimicrobial Resistance Mediated by the AdeABC Efflux Pump.

The Acinetobacter baumannii RND efflux pump AdeABC is regulated by the 2-component regulator AdeRS. In this study, we compared the regulation and expression of AdeABC of the reference strains ATCC 17978 and ATCC 19606. A clearly stronger efflux activity was demonstrated for ATCC 19606. An amino acid substitution at residue 172 of adeS was identified as a potential cause for differential expression of the pump. Therefore, we recommend caution with exclusively using single reference strains for research.

[Stage-appropriate treatment of keratoconus]. / Stadiengerechte Therapie des Keratokonus.

Keratoconus (KC) is a progressive cone-shaped corneal protrusion that causes paracentral thinning at the apex of the cone and typically occurs asymmetrically on both sides. After a careful anamnesis and classification of the degree of severity a targeted treatment appropriate to the stage of the disease is available. If the visual acuity is no longer sufficient, rigid gas-permeable contact lenses (CL) are fitted by a specialist. Riboflavin UVA cross-linking (CXL) is recommended in cases of progression and visual acuity that is still useful for the patient. Intracorneal ring segments (ICRS) are indicated for CL intolerance in cases of reduced visual acuity and a clear central cornea. If the stage is more advanced, deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PKP) is recommended. A PKP is contraindicated in acute KC but deep stromal sutures for readaptation of the Descemet tear with gas filling of the anterior chamber can considerably shorten the course. Almost no other eye disease is nowadays as easily accessible for an early instrument-based diagnosis and stage-appropriate treatment as KC.

[Evaluation of a virtual reality simulator for learning direct ophthalmoscopy in student teaching]. / Evaluierung eines VR-Simulators zum Erlernen der direkten Ophthalmoskopie in der studentischen Lehre.

BACKGROUND: The use of direct ophthalmoscopy in non-ophthalmological specialties seems to be decreasing in the clinical routine. This could be due to a lack of training and thus an uncertain assessment. OBJECTIVE: The aim of this study was to evaluate the effectiveness and acceptance of learning direct ophthalmoscopy on a simulator in comparison to the classical teaching method among students. MATERIAL AND METHODS: Within the framework of the student block internship for ophthalmology, a total of 34 students took part in the project. The first group received classical training, the second group received simulator training. The learning success was assessed by an objective structured clinical examination (OSCE). RESULTS: The simulator training group showed a significantly higher points score in individual disciplines. The subjects in the classical group achieved a learning success in the OSCE of 78%. In the simulator-based group a higher score of 91% was achieved with a lower scatter in all subdisciplines. DISCUSSION: The patient and instructor-independent availability of the teaching materials, a reduction of light exposure for patients and test subjects, as well as a standardized and controlled mediation of physiological and pathological findings can be emphasized as advantages of the tested simulator. CONCLUSION: The simulator-based training for learning direct funduscopy is effective. The virtual reality simulator evaluated in this project can improve the training of students and residents.

Prevalence and molecular epidemiology of methicillin-resistant Staphylococcus aureus in a tertiary Greek hospital.

BACKGROUND/AIM: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of health- and community-associated infections; its prevalence in Greece is among the highest in Europe. We investigated the prevalence and molecular epidemiology of MRSA in a tertiary Greek hospital. MATERIAL AND METHODS: Spa typing and random polymorphic DNA analysis were used to investigate the molecular epidemiology of 28 MRSA isolates during May 2010 to May 2011 in a tertiary hospital in Northern Greece. RESULTS: Nine spa types were detected; t003 was the predominant (32.1%) one, detected in various wards and throughout the study period, while t037 was recovered only from intensive care unit patients, and only in April 2011, suggestive of an epidemic. Additional rare types were detected for the first time in Greece. CONCLUSIONS: Spa typing and random polymorphic DNA analysis gave an insight into the epidemiology of MRSA in a Northern Greece hospital. Concerning the distribution in the hospital, the predominant spa type t003 was present in various wards, and was constantly detected throughout the study period, very suggestive of an epidemic, while other types were detected only in specific wards. Our data underline the need for surveillance, typing and constant reassessment of existing strategies to control MRSA.

Detection of West Nile virus lineage 2 in mosquitoes during a human outbreak in Greece.

A human outbreak of West Nile virus (WNV) infections occurred in 2010 in central Macedonia, northern Greece. Most cases were observed close to four rivers forming a large Delta, a major Mediterranean wetland. WNV lineage 2 sequences were obtained from two pools of Culex pipiens mosquitoes trapped in sites where encephalitis cases occurred a few days before the trapping. The Greek strain showed the highest homology to Hungarian and South African strains, differing from the Russian WNV lineage 2 strain, which suggests that at least two lineage 2 strains have been introduced and established in Europe, causing severe disease to humans.

Loss of hepatitis B immunity in hemodialysis patients acquired either naturally or after vaccination.

AIM: The aim of our study was the long-term evolution of hepatitis B immunity and the titers of antibodies against the surface antigen (anti-HBs) acquired either naturally or after vaccination in hemodialysis (HD) patients with no history of hepatitis C virus (HCV) infection. METHODS: 36 HD patients were vaccinated with 4 doses of 40 microg recombinant B vaccine (Engerix, Rixensart, Belgium), intramuscularly at 0, 1, 2 and 6 months. 21 patients (60%) seroconverted developing anti-HBs titers > or = 10 IU/ml. Two patients were transferred to another unit before completion of 6 months after the last vaccine dose. We followed-up 19 HD patients who were immune against HBV after vaccination (Group A), and 30 immune patients (anti-HBs titers > or = 10 IU/ml) who had never been vaccinated and had antibodies against the core antigen (anti-HBc), diagnostic of natural HBV infection (Group B). In all patients of Groups A and B, anti-HBs were determined every 6 months, starting 6 months after the last dose in the vaccinated patients. Follow-up period lasted from October 2002 - April 2006. RESULTS: The mean follow-up in Group A was 21 +/- 12 months (range 6 - 36) and in Group B 29 +/- 12 months (range 6 - 42). Age, sex, presence of diabetes mellitus and duration of dialysis did not differ between the two groups. Five patients in Group A (26%) and 2 patients in Group B (9%) lost immunity (anti-HBs < 10 IU/ml) (p = 0.07). The median time to loss of immunity in Group A patients was 12 months (interquartile range 6 - 18 months), while in Group B patients it was 15 months (interquartile range 12 - 18 months). No booster dose was administered during the study. The 2 patients of Group B who lost immunity were the oldest of the group and redeveloped anti-HBs 6 and 12 months after they had lost it. During the first 6 months of the follow-up period, Group A had significantly higher anti-HBs titers than Group B (p < 0.05). However, this difference was lost later on, and after the first year of follow-up, anti-HBs titers were decreased significantly in Group A (p < 0.05), but remained unchanged in Group B throughout the follow-up period. CONCLUSIONS: In conclusion, HD patients lost hepatitis B immunity both after natural infection or vaccination, but naturally infected patients easily redeveloped protective anti-HBs titers. Anti-HBs titers decreased faster in vaccinated patients than in those with natural acquired immunity who held stable titers for a longer period. It is suggested that HD patients should be followed-up regularly for loss of HBV immunity after vaccination and receive a boosting dose when this occurs. In contrast, patients who acquired natural immunity do not need any anamnestic vaccination.

Direct quantitative determination of acidic end products in clinical specimens for presumptive diagnosis of anaerobic infections.

Acidic metabolic products determined directly in clinical specimens of 51 anaerobic and 12 aerobic infections by quantitative gas-liquid chromatography (GLC) were correlated with the bacteriologic findings. The presence of appreciable amounts of succinic acid, more than 1 microM per ml, propionic and isovaleric acid, at concentrations not exceeding 3 microM per ml, was strong evidence for Bacteroides fragilis infections. When isobutyric acid was also detected, a B. melaninogenicus infection could be presumed. However, the presence of other anaerobes or aerobes could not be excluded. The presence of Clostridium spp. could also be presumed by the detection of butyric acid at a concentration greater than 4 microM per ml and of acetic, propionic and isobutyric acid at relatively high concentrations. In specimens from aerobic infections, no other acid except acetic and lactic acid could be detected. Our data also show that quantitative GLC is not valid in Peptococcus and Peptostreptococcus spp. infections except in some cases where Peptococcus alone or together with aerobic organisms are found.