Karl-Anton Hiller

Repeated exposure to subinhibitory concentrations of antiseptics may lead to reduced susceptibility or resistance and potentially promote cross-resistance to antibiotics. However, the underlying molecular mechanisms remain incompletely understood. This study investigated whether antiseptic-adapted Escherichia coli strains exhibit altered protein expression profiles compared with wild-type (WT) E. coli. Protein expression was analysed in E. coli strains previously adapted over ten passages to subinhibitory concentrations of chlorhexidine (CHX), cetylpyridinium chloride (CPC), and benzalkonium chloride (BAC). WT bacteria were exposed to sub-minimum inhibitory concentrations (sub-MICs) of antiseptics for 3 h to induce stress. Untreated WT and heat-shocked WT E. coli (42 °C, 2 h) served as controls. Protein expression profiles were assessed using SDS-PAGE and Western blotting targeting stress-associated proteins. SDS-PAGE demonstrated altered protein expression patterns in antiseptic-adapted strains, including differences in band intensities and additional protein bands. Western blot analysis showed increased DnaK and GroEL expression with reduced LexA levels in heat-shocked WT bacteria, whereas RecA remained largely unchanged. Antiseptic-adapted strains exhibited increased DnaK, GroEL, and OmpF expression together with reduced LexA and RecA expression. These findings indicate that adaptation to antiseptics involves complex mechanisms among multiple proteins rather than a single adaptive mechanism.

Objectives: This questionnaire‐based study aimed to assess parent‐reported caries (PRC) at ages 2–5 years and identify potential influencing factors using an exploratory, repeated cross‐sectional analysis within an ongoing birth‐cohort study. Methods: Parental factors included health, socioeconomic status, maternal age and dental check‐up attendance. Child factors included birth mode and weight, antibiotic, probiotic, bottle use, early dentition, weaning age, oral hygiene, diet, body mass index (BMI) and mouth‐breathing. Environmental factors included sibling caries, contact with other children, pets, or farms. Families ( n = 1296) who completed the 2‐year caries questionnaire were included, corresponding numbers were 1276 at 3 years, 993 at 4 years, and 768 at 5 years. A subgroup comprised children who had visited a dentist since their last birthday ( n = 735, at 2 years, n = 951, 891 and 662 at 3, 4 and 5 years respectively). Results: PRC rate was 0.4%, 1.3%, 2.7% and 4.4% for ages 2–5. Rates were 0.4%, 1.6%, 3.3% and 4.7% for the subgroup at the same ages. At Age 2, maternal migration background, lower paternal education and unemployment, late weaning, infrequent maternal dental check‐ups and pet contact were associated with PRC. Except for paternal education, the same factors remained associated in the subgroup. At Age 3, single‐parent status, maternal physical health, late weaning, sibling caries and pet contact were significantly associated with PRC. With the addition of infrequent maternal dental check‐ups, the same factors remained associated in the subgroup. At Age 4, early dentition, mouth‐breathing aged 1 were associated with PRC. Including late weaning, the same factors remained significantly associated in the subgroup. At Age 5, poor dietary and toothbrushing behaviour aged 2, younger mother, low BMI aged 1, infrequent maternal dental check‐ups, pet contact, and pacifier hygiene were associated with PRC. Except dietary behaviour aged 2, with the addition of paternal employment, the same factors were significantly associated in the subgroup. Conclusions: This study identifies key parental, child, and environmental risk factors for early childhood caries, revealing novel factors for further investigation and targeted prevention.

Background: This study provides a comparative analysis of Optimal Effective Concentration Combinations (OPECCs) and synergy evaluations derived from the Loewe additivity and Bliss independence models for binary antimicrobial combinations in vitro. The aim was to provide a comprehensive perspective on the utility of these strategies in analyzing binary antimicrobial combinations and their implications for effective therapeutic strategies. This study contributes to the understanding of methodological differences in evaluating antimicrobial combinations.Methods: Binary combinations of Benzalkonium chloride, Chlorhexidine, Cetylpyridinium chloride, and Ciprofloxacin were tested against E. coli and S. aureus. OPECCs and synergy evaluations were derived from OD-measurements after 3 h of aerobic incubation at 37 °C in Mueller-Hinton medium.Results: All OPECCs were determinable for each binary combination pair. For each binary concentration component, the OPECC lay below the respective minimum effective concentration in single application. The synergy scores obtained with both models ranged from −13.4 (antagonistic) to 11.2 (synergistic), with consistently higher scores for the Bliss model. However, the concentration pairs at maximum synergy, determined using the respective matrices, showed inconsistent antibacterial assessments. No pattern could be derived regarding the antibacterial effect of these concentrations in relation to the OPECCs, nor between the two synergy models. The general synergy score of a combination also does not inevitably reflect the results at effective concentrations.Conclusion: The comparison demonstrated that the assumptions like “additivity” or “independence” underlying these models can result in concentration pairs at maximum synergy that may not necessarily be effective. As a consequence, the synergy evaluation methods tested do not account for the effectiveness of the assessed concentration pairs. In contrast, the model-independent OPECC method identifies effective concentration combinations directly from experimental data, without reliance on interaction assumptions or further data processing. The separating curve is based on directly measured optical density (OD) values of the binary concentration combinations, thus representing the real situation. By offering an alternative or complementary approach to existing models, the OPECC method may support more accurate identification of effective antimicrobial combinations and provide valuable insights for the development of optimized treatment strategies in the context of rising antimicrobial resistance.

Introduction: This questionnaire-based investigation aimed to assess oral health behaviour (OHB) in 2-year-old children taking part in a birth cohort study and to identify relationships between general health, socioeconomic as well as psychosocial factors and OHB. Methods: Factors examined were single-parent status, migration background, child’s sex, parity, maternal age, education and social support, paternal employment, parental mental and physical health, and child health, data for which were collected at birth, 4 weeks, or 1 year. Participants who answered all OHB questions at 2 years (n = 730) were included. Nutritional score (NS), toothbrushing score (TS), and dental check-up score (CS) were used to calculate overall OHB score. Results: Overall OHB in this cohort was good. 62% ate fruit or vegetables daily, 75% brushed 2–3 times daily, and 61% had already had a dental check-up. Children of single mothers had significantly lower OHB scores. NS was significantly higher for children with migration background, children of mothers with better physical health or higher educational level, but lower for children of mothers reporting poor social support. TS was significantly lower in children of single mothers and children of fathers reporting poorer mental health. CS was significantly higher in children of multiparous mothers. This study highlights the relevance of social support and parental health, in contributing to OHB patterns. Conclusion: Families with special healthcare needs or less robust social support may have difficulty maintaining good OHB.

The widespread occurrence of multi-resistant bacteria is a health problem of global dimension. Infections caused by multi-resistant pathogens are difficult to treat and often associated with high mortality. Therefore, new treatment strategies are of interest, such as the use of differently acting antibacterial concepts. One of these new concepts is the use of antiseptics in combination with the antibacterial photodynamic therapy (aPDT). Currently, no method has yet been established as a standard procedure for investigating combined effects and evaluating them in a generally valid and unambiguous manner. The focus of this study was on how cationic antiseptics benzalkonium chloride (BAC) and chlorhexidine digluconate (CHX) behave in a combined application with aPDT using the photosensitizer TMPyP. For this purpose, BAC and CHX were applied in combination with the aPDT using TMPyP in non-lethal concentrations to the three bacteria Escherichia coli, Staphylococcus aureus, and Enterococcus faecalis. The results of the combination experiments with sublethal concentrations of BAC or CHX with the aPDT showed that the binary application had a lethal effect. Irrespective of the bacteria, the reduction in concentrations in OPECC, compared to individual concentrations, was more than 50% for TMPyP, 23–40% for BAC, and 18–43% for CHX. Furthermore, the optimal effective concentration combinations (OPECCs) could be determined. The latter showed that the combined application allowed the reduction of both concentrations compared to the single application.

Combination therapies appear to be beneficial for preventing bacterial resistance to antibacterial approaches. The aim of this study was to define and determine an optimal effective concentration combination (OPECC) for binary application of antibacterial compounds. The antiseptics chlorhexidine (CHX), benzalkonium chloride (BAC), and cetylpyridinium chloride (CPC), as well as the antibiotic ciprofloxacin (CIP), were tested against planktonic Escherichia coli in binary combinations by applying a checkerboard assay, and then evaluated according to the established synergism principles. Extending the checkerboard method, the optical density (OD) of the wells was measured photometrically. On the borderline between effective (OD = 0) and non-effective (OD > 0) eradication of the bacterial cultures, the OPECC was determined. Binary combinations of CPC or CHX with BAC were assessed as either synergistic or indifferent, respectively, while there was no OPECC to calculate. For all other binary combinations, an OPECC was derivable, and these were assessed as either synergistic or indifferent. In conclusion, the evaluation of the binary combination application of antibacterial compounds based on the checkerboard method was refined to such an extent that it was possible to determine at least one concentration pair that could be defined and considered as an OPECC, independently of the evaluation of the system according to the different synergy principles. In general, the method presented herein for determining an OPECC can be applied to any conceivable method or system aimed at the eradication of a pathogen.