Sukran Ozturk

Background: Antimicrobial preservatives are an integral part of dermocosmetic formulations to prevent contamination and ensure product stability. Exposure to these substances may create selective pressure on the skin microbiota and may potentially lay the groundwork for the development of antimicrobial resistance. This study aimed to evaluate the effects of commonly used dermocosmetic preservatives on the resistance profiles of skin-associated microorganisms. Methods: Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 35984, Pseudomonas aeruginosa ATCC 15442, and Candida albicans ATCC 14053 strains were exposed to phenoxyethanol, benzyl alcohol, potassium sorbate, sodium benzoate, and methylparaben for 5, 15, and 30 days. Minimum inhibitory concentration (MIC) values were determined at all stages using the broth microdilution method. Antimicrobial resistance was evaluated using vancomycin, cefepime, and fluconazole, respectively. Results: Benzyl alcohol and methylparaben showed the highest initial activity against bacterial strains, whereas potassium sorbate exhibited lower efficacy. C. albicans generally showed higher susceptibility to preservatives. Prolonged preservative exposure led to time-dependent increases in antibiotic MIC values in S. epidermidis, P. aeruginosa, and C. albicans, while S. aureus remained largely stable. Twofold increases were observed in the early period (5-15 days), and these increases reached fourfold on day 30 in some preservative–microorganism combinations. The observed MIC increases remained at the threshold of clinical resistance limits. Conclusion: Prolonged exposure to dermocosmetic preservatives may lead to measurable and time-dependent resistance developments reflecting adaptive microbial responses. These findings indicate that safety evaluations should consider not only the immediate antimicrobial efficacy of preservatives but also their long-term selective effects. Cite this article as: Ayvaz AS, Öztürk Ş, Altanlar N. Effects of dermocosmetic preservative exposure on the development of antimicrobial resistance in skin microbiota. Trends in Pharmacy, 2026, 3, 0016, doi: 10.5152/TIP.2026.26016.

Background/Objectives: The increasing prevalence of antifungal resistance among Candida albicans (C. albicans) strains necessitates the development of alternative therapeutic strategies. Curcumin (CUR), a natural polyphenolic compound, has attracted attention due to its antimicrobial and immunomodulatory properties. This study aimed to evaluate the antifungal activity of curcumin (CUR) and its effects on cellular and nuclear morphometric parameters (area, width, height, and perimeter), cytoplasmic area, and the nuclear-to-cytoplasmic ratio in an in vivo Galleria mellonella (G. mellonella) infection model. Methods: The experimental design consisted of four groups: (i) healthy control receiving phosphate-buffered saline (PBS), (ii) C. albicans-infected group (1.5 × 10⁸ CFU/mL), (iii) infected group treated with CUR (10 mg/kg), and (iv) healthy group treated with CUR. Survival was monitored for 96 h. Hemolymph samples were collected from larvae, smeared onto slides, and stained using May–Grünwald–Giemsa and Giemsa methods. Morphological evaluation and cytomorphometric analyses, including cellular area, nuclear area, cytoplasmic area, perimeter, width, height, and nucleus-to-cytoplasm ratio, were performed. Results: A higher dose (100 mg/kg) resulted in 100% mortality within 24 h and was therefore defined as lethal, whereas 10 mg/kg showed no toxicity in healthy larvae. Hemolymph was collected from surface-sterilized larvae, pooled per group, and a 10 µL aliquot was smeared onto slides. Conclusions: CUR exhibited significant antifungal activity against C. albicans and modulated host immune cell morphometry in the G. mellonella model. Its effects were dose-dependent, with potential cytotoxicity at higher concentrations. Further studies involving quantitative fungal burden analyses and mammalian models are required to clarify its therapeutic potential.

Mespilus germanica L. is one of the two species of the genus Mespilus L., and is distributed in several regions, including Southeastern Europe, Anatolia, the Caucasus, and parts of the Middle East. The fruits of the plant are consumed as food, and the fruits, leaves, and stem bark are traditionally used for various systemic disorders, including gastrointestinal, respiratory, urinary tract, and skin conditions, as well as menstrual irregularities. In our study, the anti-inflammatory potential and antimicrobial activities of aqueous-methanolic extracts prepared from ripe (MGRF) and unripe fruits (MGUF), leaves (MGL), and stem bark (MGB) of M. germanica were evaluated in vitro. Quercetin, catechin, epicatechin, ellagic acid, chlorogenic acid, and caffeic acid were analyzed using high-performance liquid chromatography. MGL exhibited the strongest activity against Staphylococcus aureus (MIC = 8 µg/mL), while MGB was most active against Enterococcus faecalis (MIC = 4 µg/mL), and fruit extracts were effective against resistant Acinetobacter baumannii (MIC = 16–32 µg/mL). Membrane-protective effects were more pronounced in MGUF and MGB, whereas MGL demonstrated the highest protein stabilization activity. Leaves also contained the highest levels of chlorogenic acid and epicatechin. These findings support the traditional use of M. germanica, though further studies are required to explore its therapeutic potential.

This study, which bridges the disciplines of archaeology and microbiology, examines the ancient bacterial communities and antibiotic-resistance genes in soil samples collected from İnönü Cave in Zonguldak, Turkiye. Our aim is to provide a comprehensive understanding of historical human activities and their influence on microbial communities. Soil samples were gathered from four distinct cultural levels from the Chalcolithic Age to the Early Iron Age. The microbial communities were characterized, and antibiotic-resistance genes were identified using high-throughput sequencing of 16S rRNA genes and metagenomic studies. This interdisciplinary approach not only enriches our understanding of ancient microbial communities but also opens up new avenues for research and collaboration. The results of our study showed a wide range of microorganisms, including prominent bacterial groups such as Acidobacteriota, Actinobacteriota, Bacteroidota, Chloroflexi, Cyanobacteria, Firmicutes, Myxococcota, and Proteobacteria. The study identified the presence of the tetracycline resistance gene tetA in Chalcolithic samples, the class 1 integron intl1 in Early Bronze Age samples, and the oxacillinase gene OXA58 in Late Bronze Age samples. These findings underscore the long-term impact of human activities on microbial communities, as antibiotic-resistance genes have been present and have remained over various historical periods, perhaps influenced by both human activities and environmental variables. This knowledge is crucial for understanding the resilience and adaptability of microbial communities in the face of human-induced changes. The coexistence of these resistance genes and alterations in the microbial population suggest substantial connections between human activities and soil microbiota. This study, which draws on the fields of archaeology, microbiology, and environmental science, offers valuable insights into the ancient microbial ecology and underscores the enduring presence of antibiotic resistance. It emphasizes the necessity of a comprehensive, interdisciplinary approach, spanning multiple fields, to comprehend microbial communities’ evolution and resistance mechanisms in archaeological settings.

Amaç: Bu çalışmada, Kırmızı Kantaron, Hypericum capitatum var. capitatum (H. capitatum) bitkisinin fenolik içeriğinin ve antioksidan aktivitesinin belirlenmesi, standart suşlar ve klinik izolatlar üzerinde antimikrobiyal etkisinin araştırılması amaçlanmıştır. Gereç ve Yöntemler: H. capitatum’un, standart bakteri suşları ile kolistin dirençli Acinetobacter baumannii (A. baumannii) ve çok ilaca dirençli (ÇİD) A. baumannii klinik izolatları üzerindeki antimikrobiyal etki düzeylerine sıvı mikrodilüsyon testi (MİK) ile gerçekleştirilmiştir (ISO, 2006). Yüksek Performanslı Sıvı Kromatografisi (YPSK) ile bazı içerikleri aydınlatılan H. capitatum ekstraktının, tohum, gövde ve yaprak örneklerinde total fenol içeriği araştırılmıştır. DPPH (2,2-difenil-1-pikrilhidrazil) yöntemi ile antioksidan etkinlik tayini yapılmıştır. Bulgular: Metanolle ekstrakte edilen bitkinin, Gram (+) bakterilere karşı Staphylococcus aureus (S.aureus) ATCC-29213 ve Metisilin dirençli S. aureus (MRSA) ATCC 43300 antimikrobiyal etkinliğinin 16 (mg/mL) olduğu saptanmıştır. Dirençli A. baumannii klinik izolatlarına karşı, 64-128 mg/mL MİK değerleri ile etkin olduğu tespit edilmiştir. YPSK ile bitkinin tohum kısmındaki içerikler ise, sırasıyla; şikimik asit (1720.42 ppm(mg/ml), kafeik asit (52.50 ppm(mg/ml), sinaminik asit, (14.217,61 ppm(mg/ml), rosmarinik asit (30,90 ppm(mg/ml) olarak belirlenmiştir. H. capitatum kısımlarına göre toplam fenolik madde miktarlarının, yaprak (155,93 mg/L), gövde (177,85 mg/L) ve tohum (344,22 mg/L) şeklinde farklılık gösterdiği tespit edilmiştir. DPPH İnhibisyon aktivitesi; tohum (%55.476 mg/mL), gövde (%57.318 mg/ ml), yaprak (%53.241 mg/ml) BHA (Butil hidroksi anozil) ve BHT (Butil hidroksi tolüen) sırasıyla (%93.77 ve %88.62) askorbik asit ise (%95.21) olarak belirlenmiştir. Sonuç: Fenolik içerikçe zengin olduğu görülen H. capitatum’ un, antioksidan etkinlik sonuçları, farklı kısımlarının metanol ekstreleri orta derecede etkili serbest radikal gideren doğal bir antioksidan kaynağı olduğunu göstermiştir. Antimikrobiyal etkinlik sonuçları ise, standart suşlar ve özellikle klinikte tedavisinin zor olduğu bilinen dirençli A. baumannii izolatlarına karşı etkinliğinin umut vaat edici olduğu görülmüştür.

Amaç: Yaygın hastane enfeksiyon ajanı olan Pseudomonas aeruginosa (P. aeruginosa)’ nın tedavisi için antiviral ilaçlar ile antibiyotiklerin kombinasyon olarak kullanılmaları sonucunda oluşan sinerjistik etkinliği araştırılmıştır. Gereç ve Yöntem: Antiviral ilaçların etken maddesi olan Umifenovir (UMF) ve Ribavirin (RBV) ile yaptığımız çalışmada Çok İlaca Dirençli (ÇİD) ve Kolistin (KOL) dirençli P. aeruginosa klinik izolatları kullanılmıştır. P. aeruginosa üzerinde, UMF ve RBV’ nin ayrı ayrı minimal inhibisyon katsayılarına (MİK) mikrodilüsyon yöntemi ile, KOL ve Sulbaktam (SUL) ile sinerjistik etkinliğine ise dama tahtası sinerji testi ile bakılmıştır. Sonuç ve Tartışma: Dirençli suşlarda, RBV ile KOL ve SUL kombinasyonlarında sinerji ve kısmi sinerji oluşurken (FİK = 0.375-0.75), ATCC 27853 suşu ile yapılan çalışmada indeferans ve aditif (FİK= 1.0-2.0) etkileşimin daha yoğun olduğu görülmüştür. UMF ile KOL ve SUL kombinasyonlarında ise sinerji ve kısmi sinerjiler (FİK=0.53-0.75) dikkat çekerken, ATCC 27853 suşlarında aditif (FİK=1.0) etki tespit edilmiştir. Sonuçlar değerlendirildiğinde UMF ve RBV’ nin KOL ve SUL ile kombinasyon kullanımlarının dirençli suşlar üzerinde daha etkin olduğu görülmüş olup, kombinasyonların dirençli hastane enfeksiyon etkenlerinin tedavisinde alternatif bir seçenek olarak kullanılabileceği fikrini ortaya koymuştur

Due to increasing antimicrobial resistance, studies where new treatment options are investigated along with the synergistic effects of natural products with antibiotics have arisen. Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen and infection with multi-drug resistant (MDR) P. aeruginosa poses a critical problem during treatment. Curcumin (CUR) is listed in the literature as one of the promising natural ingredients with its strong antimicrobial activity. In our study, our aim was to investigate the in vitro synergistic effect of CUR with imipenem (IMP) and Colistin (CST) in MDR P. aeruginosa isolates and in vivo activity on Galleria mellonella (G. mellonella) larvae. Three clinical isolates of MDR P. aeruginosa, which were determined to be phenotypically resistant to carbapenems, were used, and KPC and OXA48 resistance genes were determined by PCR method. The synergistic effect of CUR with antibiotics were investigated by the checkerboard method. Larval survival and bacterial load were compared with the in vivo study. In this study, IMP MIC values were significantly reduced (two to eight-fold decrease) in the presence of CUR, and partial synergy was observed. For CST, this value decreased two-fold. Bacterial load was evaluated to investigate the effect of antimicrobials during infection. While the CFUs increased over time in non-treated larvae as compared to the initial inoculum, bacterial load was significantly decreased for the groups treated with CUR, IMP and CST compared to the untreated group (p < 0.05). It was concluded CUR-antibiotic combinations can provide an alternative approach in the treatment of infections with MDR bacteria.

The aim of this study were to determine total phenol contents, antibacterial and antioxidant activity of bryophyte species including Plasteurhynchium striatum (Spruce) M. Fleisch, Palamocladium euchloron (Bruch ex Müll. Hal.) Wijk & Margad. and Cratoneuron filicinum (Hedw.) Spruce and Campyliadelphus chrysophylus (Brid.) R.S. Chopra. Antibacterial activity of methanolic, ethanolic, chloroform, acetone and water extracts of these species was determined by microdilution method. Antioxidant activity of these species was evaluated by 2,2-diphenyl-1-picrylhydrazyl free radical-scavenging ability. The total phenol content of these species was determined quantitatively using the folin ciocalteu reagent, with gallic acid equivalents as the standard. The highest DPPH free radical scavenging activity was observed in about 65% C. filicinum. Total phenolic content of P. euchloron was determined the highest extract value of 0,027±0,002 mg/g. The methanol extract of bryophytes was found to have significant antioxidant activity and phenolic contents. Antibacterial effect of the extracts was not observed against the tested microorganisms

The aim of this study was to investigate and compare in detail both the antifungal activity in vitro (with planktonic and biofilm-forming cells) and the essential oil composition (EOs) of naturally growing (OMN) and cultivated (OMC) samples of Origanum majorana L. (marjoram). The essential oil composition was analyzed using GC-MS. The major constituent of both EOs was carvacrol: 75.3% and 84%, respectively. Both essential oils showed high antifungal activity against clinically relevant Candida spp. with IC₅₀ and IC₉₀ less than or equal to 0.5 µg mL⁻¹ and inhibition of biofilm with a concentration of 3.5 µg mL⁻¹ or less. Cultivated marjoram oil showed higher anti-biofilm activity against C. albicans. In addition, OMC showed greater inhibition of germ-tube formation (inhibition by 83% in Spider media), the major virulence factor of C. albicans at a concentration of 0.125 µg mL⁻¹. Both EOs modulated cell surface hydrophobicity (CSH), but OMN proved to be more active with a CSH% up to 58.41%. The efficacy of O. majorana EOs was also investigated using Galleria mellonella larvae as a model. It was observed that while the larvae of the control group infected with C. albicans (6.0 × 10⁸ cells) and not receiving treatment died in the controls carried out after 24 h, all larvae in the infected treatment group survived at the end of the 96th hour. When the treatment group and the infected group were evaluated in terms of vital activities, it was found that the difference was statistically significant (p < 0.001). The infection of larvae with C. albicans and the effects of O. majorana EOs on the hemocytes of the model organism and the blastospores of C. albicans were evaluated by light microscopy on slides stained with Giemsa. Cytological examination in the treatment group revealed that C. albicans blastospores were phagocytosed and morphological changes occurred in hemocytes. Our results indicated that the essential oil of both samples showed strong antifungal activities against planktonic and biofilm-forming C. albicans cells and also had an influence on putative virulence factors (germ-tube formation and its length and on CSH).