The reduction in infectious disease morbidity and mortality may be attributed to a variety of factors; however, improved sanitation and public health, and the introduction of vaccines and antibiotics are among the most significant. The development of antimicrobial resistance (AMR) in bacterial pathogens is an expected consequence of evolutionary adaptation to these noxious agents and the widespread use of these drugs has significantly sped up this process. Infections caused by multidrug resistant pathogens are directly associated with worse clinical outcomes, longer hospital stays, excess mortality in the affected patients and an increasing burden and costs on the healthcare infrastructure. The Sustainable Development Goals (SDGs) were published in 2015 by the United Nations to serve as a global blueprint for a better, more equitable, more sustainable life on our planet. The SDGs contextualize AMR as a global public health and societal issue; in addition, the continuing emergence of AMR may limit the attainment on many SDGs. The aim of this mini-review is to provide insight on the interface between attainment of SDGs and the clinical problem of drug resistance in bacteria.

The significant growth in scientific and technological advancements within the field of dentistry has resulted in a wide range of novel treatment modalities for dentists to use. Photodynamic therapy (PDT) is an emerging, non-invasive treatment method, involving photosensitizers, light of a specific wavelength and the generation of singlet oxygen and reactive oxygen species (ROS) to eliminate unwanted eukaryotic cells (e.g., malignancies in the oral cavity) or pathogenic microorganisms. The aim of this review article is to summarize the history, general concepts, advantages and disadvantages of PDT and to provide examples for current indications of PDT in various subspecialties of dentistry (oral and maxillofacial surgery, oral medicine, endodontics, preventive dentistry, periodontology and implantology), in addition to presenting some images from our own experiences about the clinical success with PDT.

Introduction: Staphylococcus aureus (S. aureus) is an important causative pathogen in human infections. The production of biofilms by bacteria is an important factor, leading to treatment failures. There has been significant interest in assessing the possible relationship between the multidrug-resistant (MDR) status and the biofilm-producer phenotype in bacteria. The aim of our present study was to assess the biofilm-production rates in clinical methicillin-susceptible S. aureus [MSSA] and methicillin-resistant S. aureus [MRSA] isolates from Hungarian hospitals and the correlation between resistance characteristics and their biofilm-forming capacity. Methods: A total of three hundred (n=300) S. aureus isolates (corresponding to MSSA and MRSA isolates in equal measure) were included in this study. Identification of the isolates was carried out using the VITEK 2 ID/AST system and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Antimicrobial susceptibility testing was performed using the Kirby–Bauer disk diffusion method and E-tests, confirmation of MRSA status was carried out using PBP2a agglutination assay. Biofilm-production was assessed using the crystal violet (CV) tube-adherence method and the Congo red agar (CRA) plate method. Results: There were significant differences among MSSA and MRSA isolates regarding susceptibility-levels to commonly used antibiotics (in case of erythromycin, clindamycin and ciprofloxacin: p< 0.001, gentamicin: p=0.023, sulfamethoxazole/trimethoprim: p=0.027, rifampin: p=0.037). In the CV tube adherence-assay, 37% (n=56) of MSSA and 39% (n=58) of MRSA isolates were positive for biofilm-production, while during the use of CRA plates, 41% (n=61) of MSSA and 44% (n=66) of MRSA were positive; no associations were found between methicillin-resistance and biofilm-production. On the other hand, erythromycin, clindamycin and rifampin resistance was associated with biofilm-positivity (p=0.004, p< 0.001 and p< 0.001, respectively). Biofilm-positive isolates were most common from catheter-associated infections. Discussion: Our study emphasizes the need for additional experiments to assess the role biofilms have in the pathogenesis of implant-associated and chronic S. aureus infections.

The formation of a protective biofilm by Pseudomonas aeruginosa (PA) is one of the hallmarks of their survival both in vivo and in harsh environmental conditions, thus, biofilm-eradication has relevance from therapeutic perspectives and for infection control. The aim of our study was to investigate the possible relationship between antibiotic resistance, biofilm-forming capacity and virulence factors in n = 166 PA isolates of environmental origin. Antimicrobial susceptibility testing and the phenotypic detection of resistance determinants were carried out using standard protocols. The biofilm-forming capacity of PA was tested using a standardized crystal violet microtiter plate-based method. Motility (swimming, swarming, and twitching) and siderophore production of the isolates were also assessed. Resistance rates were highest for ciprofloxacin (46.98%), levofloxacin (45.18%), ceftazidime (31.92%) and cefepime (30.12%); 19.28% of isolates met the criteria to be classified as multidrug-resistant (MDR). Efflux pump overexpression, AmpC overexpression, and modified Hodge-test positivity were noted in 28.31%, 18.07% and 3.61%, respectively. 22.89% of isolates were weak/non-biofilm producers, while 27.71% and 49.40% were moderate and strong biofilm producers, respectively. Based on MDR status of the isolates, no significant differences in biofilm-production were shown among environmental PA (non-MDR OD₅₇₀ [mean ± SD]: 0.416 ± 0.167 vs. MDR OD₅₇₀: 0.399 ± 0.192; p > 0.05). No significant association was observed between either motility types in the context of drug resistance or biofilm-forming capacity (p > 0.05). 83.13% of isolates tested were positive for siderophore production. The importance of PA as a pathogen in chronic and healthcare-associated infections has been described extensively, while there is increasing awareness of PA as an environmental agent in agriculture and aquaculture. Additional studies in this field would be an important undertaking to understand the interrelated nature of biofilm production and antimicrobial resistance, as these insights may become relevant bases for developing novel therapeutics and eradication strategies against PA.

The relationship between the multidrug-resistant (MDR) phenotype and biofilm-forming capacity has been a topic of extensive interest among biomedical scientists, as these two factors may have significant influence on the outcomes of infections. The aim of the present study was to establish a possible relationship between biofilm-forming capacity and the antibiotic-resistant phenotype in clinical Acinetobacter baumannii (A. baumannii) isolates. A total of n = 309 isolates were included in this study. Antimicrobial susceptibility testing and the phenotypic detection of resistance determinants were carried out. The capacity of isolates to produce biofilms was assessed using a crystal violet microtiter-plate-based method. Resistance rates were highest for ciprofloxacin (71.19%; n = 220), levofloxacin (n = 68.61%; n = 212), and trimethoprim-sulfamethoxazole (n = 66.02%; n = 209); 42.72% (n = 132) of isolates were classified as MDR; 22.65% (n = 70) of tested isolates were positive in the modified Hodge-test; the overexpression of efflux pumps had significant effects on the susceptibilities of meropenem, gentamicin, and ciprofloxacin in 14.24% (n = 44), 6.05% (n = 19), and 27.51% (n = 85), respectively; 9.39% (n = 29), 12.29% (n = 38), 22.97% (n = 71), and 55.35% (n = 170) of isolates were non-biofilm-producing and weak, moderate, and strong biofilm producers, respectively. A numerical, but statistically not significant, difference was identified between the MDR and non-MDR isolates regarding their biofilm-forming capacity (MDR: 0.495 ± 0.309 vs. non-MDR: 0.545 ± 0.283; p = 0.072), and no association was seen between resistance to individual antibiotics and biofilm formation. Based on numerical trends, MER-resistant isolates were the strongest biofilm producers (p = 0.067). Our study emphasizes the need for additional experiments to assess the role biofilms have in the pathogenesis of A. baumannii infections.

Streptococcus suis (S. suis) is an emerging zoonotic pathogen, demonstrated as an etiological agent in human infections in increasing frequency, including diseases like purulent meningitis, sepsis, uveitis-endophtalmitis and arthritis. Due to the increased availability and utility of novel diagnostic technologies in clinical microbiology, more studies have been published on the epidemiology of S. suis, both in veterinary and human medicine; however, there are no comprehensive data available regarding human S. suis infections from East-Central European countries. As a part of our study, data were collected from the National Bacteriological Surveillance (NBS) system on patients who had at least one positive microbiological result for S. suis, corresponding to an 18-year study period (2002–2019). n = 74 S. suis strains were isolated from invasive human infections, corresponding to 34 patients. The number of affected patients was 1.89 ± 1.53/year (range: 0–5). Most isolates originated from blood culture (63.5%) and cerebrospinal fluid (18.9%) samples. Additionally, we present detailed documentation of three instructive cases from three regions of the country and with three distinctly different outcomes. Hungary has traditional agriculture, the significant portion of which includes the production and consumption of pork meat, with characteristic preparation and consumption customs and unfavorable epidemiological characteristics (alcohol consumption, prevalence of malignant diseases or diabetes), which have all been described as important predisposing factors for the development of serious infections. Clinicians and microbiologist need to be vigilant even in nonendemic areas, especially if the patients have a history of occupational hazards or having close contact with infected pigs.