Microbial Diversity and Antimicrobial Resistance Profile in Microbiota From Soils of Conventional and Organic Farming Systems

Soil is one of the biggest reservoirs of microbial diversity, yet the processes that define the community dynamics are not fully understood. Apart from soil management being vital for agricultural purposes, it is also considered a favorable environment for the evolution and development of antimicrobial resistance, which is due to its high complexity and ongoing competition between the microorganisms. Different approaches to agricultural production might have specific outcomes for soil microbial community composition and antibiotic resistance phenotype. Therefore in this study we aimed to compare the soil microbiota and its resistome in conventional and organic farming systems that are continually influenced by the different treatment (inorganic fertilizers and pesticides vs. organic manure and no chemical pest management). The comparison of the soil microbial communities revealed no major differences among the main phyla of bacteria between the two farming styles with similar soil structure and pH. Only small differences between the lower taxa could be observed indicating that the soil community is stable, with minor shifts in composition being able to handle the different styles of treatment and fertilization. It is still unclear what level of intensity can change microbial composition but current conventional farming in Central Europe demonstrates acceptable level of intensity for soil bacterial communities. When the resistome of the soils was assessed by screening the total soil DNA for clinically relevant and soil-derived antibiotic resistance genes, a low variety of resistance determinants was detected (resistance to β-lactams, aminoglycosides, tetracycline, erythromycin, and rifampicin) with no clear preference for the soil farming type. The same soil samples were also used to isolate antibiotic resistant cultivable bacteria, which were predominated by highly resistant isolates of Pseudomonas, Stenotrophomonas, Sphingobacterium and Chryseobacterium genera. The resistance of these isolates was largely dependent on the efflux mechanisms, the soil Pseudomonas spp. relying mostly on RND, while Stenotrophomonas spp. and Chryseobacterium spp. on RND and ABC transporters

The peculiarities of Pseudomonas aeruginosa resistance to antibiotics and prevalence of serogroups

Pseudomonas aeruginosa is one of the most common nonfermenting aerobic gramnegative microorganisms identified in clinical specimens of hospitalized patients. The emergence of multidrug-resistant (MDR) Pseudomonas aeruginosa strains is a growing concern in hospitalacquired infections. Typing of strains is important for identifying the sources of infection as well as prevention of cross-infections and monitoring of the efficacy of antimicrobial therapy. The aim of this study was to evaluate the antimicrobial resistance and prevalence of Pseudomonas aeruginosa serogroups isolated at Kaunas University of Medicine Hospital, Lithuania. Material and methods. Minimum inhibitory concentrations of piperacillin, cefoperazone, ceftazidime, cefotaxime, cefepime, imipenem, meropenem, gentamicin, amikacin, tobramycin, and ciprofloxacin for 609 Pseudomonas aeruginosa strains isolated from various clinical specimens between November 2001 and November 2002 were determined by the microdilution method in Mueller–Hinton agar using interpretative guidelines of National Committee for Clinical Laboratory Standards. Serogroups of Pseudomonas aeruginosa strains were identified using serums of Seiken Co. Ltd (Tokyo, Japan), containing antibodies against antigens of Pseudomonas aeruginosa O-group. Results. Pseudomonas aeruginosa strains were the most sensitive to ceftazidime (78.9%), imipenem (73.6%), meropenem (70.9%) and the most resistant to gentamicin (54.1%) and ciprofloxacin (52.5%). Multidrug-resistant strains made up 9.85% of all Pseudomonas aeruginosa strains investigated. Multidrug-resistant Pseudomonas aeruginosa strains were 1.5–3.5 times more resistant to antibiotics compared to non-multidrug-resistant strains, except to amikacin: multidrug-resistant strains were more sensitive (81.7%) than non-multidrug-resistant Pseudomonas aeruginosa strains (61.0%). Pseudomonas aeruginosa serogroups O:E and O:B were the most common serogroups (34.7% and 29.0%, respectively) followed by serogroups O:I (11.4%) and O:A (10.1%). Pseudomonas aeruginosa serogroup O:E strains were the most prevalent among multidrug-resistant strains (48.3%). Conclusions. The results of our study show that serogroup O:E was the most prevalent serogroup of Pseudomonas aeruginosa in our hospital, and its resistance to antibiotics was the highest

Effect of graphene oxide and silver nanoparticles hybrid composite on P. aeruginosa strains with acquired resistance genes

Background: In the last decades, nosocomial infections caused by drug-resistant Pseudomonas aeruginosa became a common problem in healthcare facilities. Antibiotics are becoming less effective as new resistant strains appear. Therefore, the development of novel enhanced activity antibacterial agents becomes very significant. A combination of nanomaterials with different physical and chemical properties enables us to generate novel multi-functional derivatives. In this study, graphene oxide and polyvinylpyrrolidone-stabilized silver nanoparticles hybrid nanocomposite (GO-Ag HN) were synthesized. The relation between antibiotic resistance and GO-Ag HN potential toxicity to clinical P. aeruginosa strains, their antibiotic resistance, and molecular mechanisms were assessed. Methods: Chemical state, particle size distribution, and morphology of synthesized GO-Ag NH were investigated using spectroscopy and microscopy techniques (UV-Vis, FTIR, XPS, TEM, SEM, AFM). Broad-spectrum antibiotic resistance of P. aeruginosa strains was determined using E-test. Antibiotic resistance genes were identified using polymerase chain reaction (PCR). Results: In this study, the toxicity of the GO-Ag NH to the isolated clinical P. aeruginosa strains has been investigated. A high antibiotic resistance level (92%) was found among P. aeruginosa strains. The most prevalent antibiotic resistance gene among tested strains was the AMPC beta-lactamase gene (65.6%). UV-vis, FTIR, and XPS studies confirmed the formation of the silver nanoparticles on the GO nanosheets. The functionalization process occurred through the interaction between Ag nanoparticles, GO, and polyvinylpyrrolidone used for nanoparticle stabilization. SEM analysis revealed that GO nanosheets undergo partial fragmentation during hybrid nanocomposite preparation, which remarkably increases the number of sharp edges and their mediated cutting effect. TEM analysis showed that GO-Ag HN spherical Ag nanoparticles mainly 9– 12 nm in size were irregularly precipitated on the GO nanosheet surface. A higher density of Ag NPs was observed in the sheets’ wrinkles, corrugations, and sharp edges. This hybrid nanocomposite poses enhanced antibacterial activity against carbapenem-resistant P. aeruginosa strains through a possible synergy between toxicity mechanisms of GO nanosheets and Ag nanoparticles. With incubation time increasing up to 10 minutes, the survival of P. aeruginosa decreased significantly. Conclusion: A graphene oxide and silver nanoparticles hybrid composite has been shown to be a promising material to control nosocomial infections caused by bacteria strains resistant to most antibiotics

Microflora of the Oral Cavity in Patients with Xerostomia

Objective. The aim of this study was to evaluate the dependence of the condition of the microflora of the oral cavity on the etiology of xerostomia, patients’ sex, age, degree of hyposalivation, and duration of the sense of dryness. Material and Methods. A total of 64 patients with complaints of oral dryness referred to the Clinic of Oral and Dental Diseases, Hospital of Lithuanian University of Health Sciences, for consultation during the period from 2003 to 2005 were selected for the study. The etiological factors of xerostomia were as follows: radiotherapy (PRT) to the maxillofacial area, Sjögren’s syndrome (SS), and xerogenic medications, tricyclic antidepressants (TCAs). Results. There were 50 women and 14 men. Their mean age was 60.5±1.6 years. All the patients in the PRT group had high counts of Candida spp. as compared with percentages of patients in the TCA and SS groups (100% vs. 66.7% and 56.2%, P<0.05). Patients’ age and sex in different etiology groups had no significant impact on the condition of their oral microflora. There were equal percentages of patients with deficient and normal salivation in the TCA group (44% in both the groups; P<0.01). All the patients in the PRT group had pronounced hyposalivation (P<0.002). A significantly greater percentage of patients with severely reduced salivation had high counts of Lactobacillus spp. (P<0.01). Significantly greater percentages of patients with the clinical duration of xerostomia of up to 6 months had high counts of Lactobacillus spp. and Candida spp. colonies. Conclusions. In patients with xerostomia, the condition of the microflora of the oral cavity and impairment of major salivary gland function varied according to the etiology of the disease. The level of hyposalivation and the duration of xerostomia were found to have a significant impact on the microflora of the oral cavity