Search Results (213)

Polymicrobial biofilms involving fungal and bacterial species are increasingly recognized as contributors to persistent infections, particularly in the oral cavity. Candida albicans and Aggregatibacter actinomycetemcomitans are two commensals that can turn into opportunistic pathogens and are able to form robust biofilms. Objectives: This study aimed to assess the interaction dynamics between these two microorganisms and to evaluate their susceptibility to fluconazole and azithromycin in single- and mixed-species forms. Methods: Biofilm biomass was quantified using crystal violet assays, while biofilm cell viability was assessed through CFU enumeration (biofilm viability assay). To assess the resistance properties of single versus mixed-species coincubations, we applied the antimicrobial susceptibility test (AST) to each drug, and analysed spatial organization with confocal laser scanning microscopy, using PNA-FISH. Results: The results indicated that both species can coexist without significant mutual inhibition. However, a non-reciprocal synergism was also observed, whereby mixed-species biofilm conditions promoted the growth of A. actinomycetemcomitans, while C. albicans growth remained stable. As expected, antimicrobial tolerance was elevated in mixed cultures, likely due to enhanced extracellular matrix production and potential quorum-sensing interactions, contributing to increased resistance against azithromycin and fluconazole. Conclusions: This study provides novel insights into previously rarely explored interactions between C. albicans and A. actinomycetemcomitans. These findings underscore the importance of investigating interspecies interactions within polymicrobial biofilms, as understanding their mechanisms, such as quorum-sensing molecules and metabolic cooperation, can contribute to improved diagnostics and more effective targeted therapeutic strategies against polymicrobial infections. Full article

About a quarter of the world’s population is infected with Mycobacterium tuberculosis. Growing antibiotic resistance by this microorganism is a major problem in the therapy of the disease. M. avium-M. intracellulare that emerged as a major opportunistic infection of HIV/AIDS continues to afflict immunocompromised individuals. We describe the use of liposome-encapsulated antibiotics in the experimental and clinical therapy of mycobacterial infections, as well as recent experimental liposomal vaccines against tuberculosis. Liposome-mediated intravenous or inhalational delivery of antibiotics enhances the antibacterial effects of the drugs, particularly for infections of resident macrophages, where the liposomes are passively targeted. Despite experimental successes of liposomal antibiotics in the treatment of mycobacterial and other bacterial infections, applications of this method to the clinic have been lagging. This review underscores the significance of liposomes in the treatment of mycobacterial infections, encompassing their synthesis methods, limitations, and both preclinical and clinical studies, providing guidance for the development of future therapeutic approaches and innovative antimicrobial strategies. Full article

Staphylococcus saprophyticus (S. saprophyticus) is an opportunistic coagulase-negative staphylococcus (CoNS) known to cause urinary tract infections in humans and is increasingly recognized in veterinary medicine. The aim of this study was to provide an epidemiological characterization of S. saprophyticus strains and to identify potential virulence factors that may contribute to interspecies transmission. This research is particularly important, as companion animals represent an understudied reservoir of this microorganism, and their role in the spread of resistant pathogens remains insufficiently understood. A total of 61 S. saprophyticus strains isolated from humans, dogs, and cats were analyzed. Identification was performed using MALDI-TOF MS and confirmed by PCR targeting the hrcA gene. Antimicrobial susceptibility was assessed using the disk diffusion and broth microdilution methods, while resistance genes were detected by PCR. The blaZ and mecA genes were present in all strains; additionally, the majority harbored the resistance genes ermA, ermB, tetM, and tetK. Multidrug resistance (MDR) was identified in 21/61 strains (34.4%). Biofilm-forming capacity was temperature-dependent, with the strongest biofilm production observed at 37 °C (70.5%). At 38 °C and 39 °C, the proportion of strong biofilm producers decreased to 50.8% and 52.5%, respectively. All tested strains demonstrated pathogenic potential in the Galleria mellonella larvae infection model, with the highest mortality recorded for selected feline and canine strains. These findings indicate that S. saprophyticus strains from both humans and companion animals possess notable virulence and multidrug resistance. The detection of genotypically and phenotypically resistant strains in animals highlights their potential role as reservoir for zoonotic transmission. Full article

Cutibacterium acnes (C. acnes) is a commensal bacterium of the skin microbiota that can transform itself into a pathogen depending on the peculiar susceptibility of the host: it is the sole microorganism so far to be found in the specific organ lesions of sarcoidosis, and C. acnes-induced activation of T-helper-type-1 cell responses is generally higher in patients with sarcoidosis than in healthy subjects. This bacterium acts as an opportunistic agent in several inflammatory conditions other than sarcoidosis, such as prostate cancer and prosthetic joint infections. Both innate and adaptive immunity systems are involved in the pathogenesis of C. acnes-mediated sarcoid lesions, and a seminal role is played by host toll-like receptor (TLR)-2, TLR-4, TLR-6, NOD-like receptors, and mononuclear cell cytoplasmic receptors. This review summarizes current knowledge on the potential cause–effect relationship existing between C. acnes and sarcoidosis, addressing issues of future research directions and novel therapeutic strategies in the management of a complex disease such as sarcoidosis. Full article

Bloodstream infections are a significant cause of morbidity and mortality among hemodialysis patients. These infections primarily involve Gram-positive bacteria and, less frequently, Gram-negative bacilli. Raoultella ornithinolytica is a Gram-negative bacillus which is known to be a rare opportunistic pathogen. It is found only occasionally in human infections; however, it has been noted as an emerging pathogen. Sepsis caused by this microorganism is very rare. A few cases have been reported among immunocompromised patients or those undergoing invasive procedures. Cases involving urinary catheters or port catheters have also been reported, as well as a single case of a patient on peritoneal dialysis. Here, we present a novel case of Raoultella ornithinolytica bloodstream infection in a patient with chronic renal failure undergoing hemodialysis who was successfully treated. We discuss the microbiology and clinical features of such infections, and consider aspects of treatment. Full article

Background/Objectives: Patients with head and neck cancer frequently develop oral complications such as oral mucositis, infections, necrosis, and periodontal disease among others as a consequence of antineoplastic therapy. It is mainly radiotherapy that promotes oral dysbiosis, favouring the overgrowth of opportunistic microorganisms. Identifying effective adjunctive strategies to prevent or mitigate these adverse effects is crucial. Recent studies have suggested that probiotics could be used to restore microbial homeostasis and modulate inflammatory responses in the oral cavity. This systematic review and meta-analysis assessed the efficacy of probiotics in alleviating oral complications associated with antineoplastic treatments in this patient population. Methods: A comprehensive search was conducted in PubMed, LILACS, Scopus and the Cochrane Central Register of Controlled Trials, following the PRISMA 2020 guidelines. Only randomised controlled trials (RCTs) were included. Results: Nine eligible RCTs were analysed using a random-effects meta-analysis. Probiotic use was significantly associated with a reduced incidence of severe (grade 3–4) oral mucositis (RR = 0.58; 95% CI: 0.41–0.81). Moderate benefits were also observed in modulating the oral microbiota and reducing levels of pathogenic bacteria and Candida spp. However, no significant improvements were noted in periodontal parameters or plaque indices. Conclusions: Probiotics show promise in the management of oral mucositis, but further well-designed trials are needed to evaluate their broader impact on oral health during cancer therapy. This review is not registered on PROSPERO. Full article

Background: Cryptococcus species constitute opportunistic fungi that seldom cause infections in individuals with competent immune systems. In the rare case of cryptococcal endocarditis, the fungus infiltrates the endocardium. This disease occurs almost exclusively in patients with active immunosuppression, implanted cardiac devices, or prosthetic valves. Objectives: This study aims to analyze all documented cases of Cryptococcus spp. endocarditis in humans, emphasizing the epidemiology, microbiology, clinical manifestations, therapeutic approaches, and infection outcomes. Methods: A comprehensive review was performed by searching the PubMed and Scopus databases. Results: A total of 16 studies reported data on 16 patients diagnosed with cryptococcal endocarditis. The mean patient age was 46.6 years, with males comprising 81.25% of cases. Immunosuppression was the most prevalent predisposing factor (31.25%), followed by a history of end-stage renal disease and prosthetic cardiac valves (25%). The most commonly affected intracardiac sites were the mitral (60%) and aortic valve (46.6%), while in 33.3% of cases, multiple-valve infection was observed. Cryptococcus neoformans was detected as the causative organism in the majority of cases (87.5%). The most frequently administered antifungal treatments included amphotericin B (87.5%) and fluconazole (43.75%), with combination therapy used in 62.5% of cases. Overall mortality was relatively high at 56.25%, with 50% of deaths directly attributed to the infection. Conclusions: Considering the ability of Cryptococcus spp. to induce severe systemic infections, healthcare providers should consider this pathogen in the differential diagnosis when yeast microorganisms are identified in microbiological samples. This is particularly crucial for patients with underlying comorbidities or immunodeficiency, as early recognition is crucial to ensure precise diagnosis and treatment. Full article

Helicobacter pylori and Candida spp. are widespread microorganisms found in the human gastrointestinal tract, often coexisting in the same ecological niche. H. pylori, a Gram-negative bacterium, is a well-known pathogen responsible for gastritis, peptic ulcers, and gastric cancer. In contrast, Candida fungi, often detected in food, particularly Candida albicans, are generally considered commensal organisms, but can become opportunistic pathogens under certain conditions. Recent studies suggest a possible link between these microorganisms, highlighting a new survival strategy of H. pylori, that is, its ability to internalize in Candida vacuoles. This phenomenon, confirmed by various microscopic and molecular techniques, may provide H. pylori with protection against adverse environmental conditions, especially clinically important antibiotic therapy. The basic premise of this theory is the ability of H. pylori to penetrate vacuoles in fungal cells, which then become a reservoir of infection, allowing the infection to recur. Understanding the interaction between H. pylori and Candida may offer new insights into the pathogenesis of gastrointestinal diseases and may lead to the development of treatments targeting both organisms simultaneously. The purpose of this article is to review the literature, considering the first observations on this problem in the literature and the current state of knowledge, and to suggest a direction for further research. Full article

Human infections are greatly impacted by intestinal nematodes. These nematodes, which encompass the large roundworms, have a direct impact on human health and well-being due to their close cohabitation with the host’s microorganisms. When nematodes infect a host, the microbiome composition changes, and this can impact the host’s ability to control the parasites. We aimed to find out if the small intestinal roundworms produce substances that have antimicrobial properties and respond to their microbial environment, and if the immune and regulatory reactions to nematodes are altered in humans lacking gut microbes. There is no doubt that different nematodes living in the intestines can alter the balance of intestinal bacteria. Nonetheless, our knowledge about the parasite’s influence on the gut microbiome remains restricted. The last two decades of study have revealed that the type of iron utilized can influence the activation of unique virulence factors. However, some roundworm proteins like P43, which makes up a large portion of the worm’s excretory-secretory product, have an unknown role. This review explores how the bacterial iron regulatory network contributes to the adaptability of this opportunistic pathogen, allowing it to successfully infect nematodes in different host environments. Full article

The escalating global prevalence of fungal and bacterial co-infections underscores the significant and multifaceted impact of ubiquitous microorganisms on both environmental equilibria and human well-being. The human microbiome, a complex ecosystem of bacterial communities, harbors opportunistic pathogens capable of inducing superinfections or concurrent infections with Candida spp. The intricate interplay, exemplified by the interaction between Candida albicans and diverse bacteria, necessitates rigorous investigation to elucidate mechanisms by which this polymicrobial behavior potentiates fungal virulence, particularly in immunocompromised individuals. Our study aims to comprehensively examine the ramifications of these interactions, with a specific focus on their influence on fungal virulence and the consequent exacerbation of disease severity. Achieving a comprehensive understanding of these complex relationships is paramount for informing effective clinical management strategies for infectious diseases, and the accurate identification of fungal–bacterial co-infections holds substantial implications for optimizing clinical treatment paradigms, especially in vulnerable immunocompromised hosts. Full article

Biofilms are structurally organized communities of microorganisms that adhere to a variety of surfaces. These communities produce protective matrices consisting of polymeric polysaccharides, proteins, nucleic acids, and/or lipids that promote shared resistance to various environmental threats, including chemical, antibiotic, and immune insults. While algal and bacterial biofilms are more apparent in the scientific zeitgeist, many fungal pathogens also form biofilms. These surprisingly common biofilms are morphologically distinct from the multicellular molds and mushrooms normally associated with fungi and are instead an assemblage of single-celled organisms. As a collection of yeast and filamentous cells cloaked in an extracellular matrix, fungal biofilms are an extreme threat to public health, especially in conjunction with surgical implants. The encapsulated yeast, Cryptococcus neoformans, is an opportunistic pathogen that causes both pulmonary and disseminated infections, particularly in immunocompromised individuals. However, there is an emerging trend of cryptococcosis among otherwise healthy individuals. C. neoformans forms biofilms in diverse environments, including within human hosts. Notably, biofilm association correlates with increased expression of multiple virulence factors and increased resistance to both host defenses and antifungal treatments. Thus, it is crucial to develop novel strategies to combat fungal biofilms. In this review, we discuss the development and treatment of fungal biofilms, with a particular focus on C. neoformans. Full article

This article reviews the scientific literature discussing the microbial interactions between water microbiota, live food microbiota, fish larvae immune system and gut microbiota, and biofilm microbial communities in rearing systems for marine fish larvae. Fish gut microbiota is the first line of defense against opportunistic pathogens, and marine fish larvae are vulnerable to high mortalities during the first weeks after hatching. The bacterial colonization of fish larvae is a dynamic process influenced by environmental and host-related factors. The bacteria transferred to larvae from the eggs can influence the composition of the gut microbiota in the early stages of fish. Fish larvae ingest free-living microorganisms present in the water, as marine fish larvae drink water for osmoregulation. In marine aquaculture systems, the conventional feeding–rearing protocol consists of zooplankton (rotifers, Artemia, and copepods). These live food organisms are filter-feeders. Once transferred to a new environment, they quickly adopt the microflora of the surrounding water. So, the water microbiota is similar to the microbiota of the live food at the time of ingestion of live food by the larvae. In aquaculture rearing systems, bacterial biofilms may harbor opportunistic pathogenic bacteria and serve as a reservoir for those microbes, which may colonize the water column. The methods applied for the study of fish larvae microbiota were reviewed. Full article

Cryptococcus neoformans, a high-priority pathogen (WHO, 2022) and ubiquitous fungus, is responsible for hundreds of thousands of meningoencephalitis cases annually, with a high fatality rate. Its distribution is uneven: it primarily affects immunocompromised individuals (especially HIV-positive patients). Our study aims to explore the Cryptococcus’ brain tropism in immunosuppressed patients, its gender preference and the possible interactions with other opportunistic neurotropic microorganisms, such as Mycobacterium tuberculosis (MTB) and the brain microbiota, with a particular focus on Toxoplasma gondii (T. gondii). Methods: We conducted a retrospective descriptive analysis of all cases diagnosed with central nervous system cryptococcosis (Crypto-CNS) in HIV-positive patients admitted over 10 years (2010–2019) in a tertiary Romanian hospital. We examined their demographic, clinical, immunobiological, and imaging data, as well as their medical history, comorbidities, and coinfections. Results: Forty-two cases were admitted, with a male predominance (3.6:1) and a mean age of 33.3 years; 24% were diagnosed concomitantly with HIV infection and Crypto-CNS. All patients were severely immunosuppressed, with CD4 counts <200 cells/mm³ (median = 20.5 [1–163], mean = 31.6). Recent/concomitant tuberculosis was found in 10 (27.7%). T. gondii-seropositive patients developed Crypto-CNS at a lower immunological state than seronegative ones (27.1 CD4 cells/mm³ vs. 46.7 cells/mm³, means). Of 25 cases with available brain imagery, 28% had high intracranial pressure. Twelve patients (28.5%) died during the hospitalization within 26.3 days (mean, SD = 21.4); 1-year mortality increased to 50%. In-hospital mortality was associated with lower CD4 counts, increased intracranial pressure, and T. gondii-seropositivity. Conclusions: Crypto-CNS in HIV-positive patients mainly affects men and may be promoted by concomitant or recent tuberculosis. T. gondii may confer some protection even at low immune levels but increases mortality when immunity is critically low. Full article

The incidence of fungal infections continues to increase and one of the factors responsible for these high rates is the emergence of multi-resistant species, hospitalizations, inappropriate or prolonged use of medications, and pandemics, such as the ongoing HIV/AIDS pandemic. The recent pandemic caused by the severe acute respiratory syndrome virus (SARS-CoV-2) has led to a significant increase in fungal infections, especially systemic mycoses caused by opportunistic fungi. There is a growing and urgent need to better understand how these microorganisms cause infection and develop resistance as well as to develop new therapeutic strategies to combat the diverse diseases caused by fungi. Non-mammalian hosts are increasingly used as alternative models to study microbial infections. Due to their low cost, simplicity of care, conserved innate immunity and reduced ethical issues, the greater wax moth Galleria mellonella is an excellent model host for studying fungal infections and it is currently widely used to study fungal pathogenesis and develop innovative strategies to mitigate the mycoses studied. G. mellonella can grow at 37 °C, which is similar to the mammalian temperature, and the anatomy of the larvae allows researchers to easily deliver pathogens, biological products, compounds and drugs. The aim of this review is to describe how G. mellonella is being used as a model system to study fungal infections as well as the importance of this model in evaluating the antifungal profile of potential drug candidates or new therapies against fungi. Full article

Feline immunodeficiency virus (FIV) is the domestic cat analogue of HIV infection in humans. Both viruses induce oral disease in untreated individuals, with clinical signs that include gingivitis and periodontal lesions. Oral disease manifestations in HIV patients are abated by highly effective combination antiretroviral therapy (cART), though certain oral manifestations persist despite therapy. Microorganisms associated with oral cavity opportunistic infections in patients with HIV cause similar pathologies in cats. To further develop this model, we evaluated characteristics of feline oral health and the oral microbiome during experimental FIV infection over an 8-month period following cART. Using 16S rRNA sequencing, we evaluated gingival bacterial communities at four timepoints in uninfected and FIV-infected cats treated with either cART or placebo. Comprehensive oral examinations were also conducted by a veterinary dental specialist over the experimental period. Gingival inflammation was higher in FIV-infected cats treated with placebo compared to cART-treated cats and the controls at the study endpoint. Oral microbiome alpha diversity increased in all groups, while beta diversity differed among treatment groups, documenting a significant effect of cART therapy on microbiome community composition. This finding has not previously been reported, and indicates cART ameliorates immunodeficiency virus-associated oral disease via the preservation of oral mucosal microbiota. Further, this study illustrates the value of the FIV animal model for investigations of mechanistic associations and therapeutic interventions for HIV’s oral manifestations. Full article