Phylogenetic group B2 expressed significant biofilm formation among drug-resistant uropathogenic Escherichia coli

Biofilm is an important virulent marker attributed to the development of urinary tract infections (UTIs) by uropathogenic E. coli (UPEC). Drug-resistant and biofilm-producing UPEC are highly problematic causing catheter-associated or recurrent UTIs with significant morbidity and mortality. The aim of the current study was to investigate the prevalence of biofilm formation and phylogenetic groups in drug-resistant UPEC to predict their ability to cause disease. This prospective study was conducted at the Department of Microbiology, University of Karachi from January to June 2019. A total of 50 highly drug-resistant UPEC were selected for this study. UPEC isolates were screened to form biofilm by Congo-red agar (CRA) and microtiter plate (MTP) technique. The representative biofilm-producing isolates were analysed by scanning electron microscopy (SEM) monitoring. Phylogenetic analysis was done by PCR method based on two preserved genes; chuA, yjaA and TspE4-C2 DNA fragment. On CRA 34 (68%) UPEC were slime producers, while on MTP 20 (40%) were strong biofilm producers, 19 (38%) moderate and 11 (22%) were low to negligible biofilm producers. Molecular typing confirmed that phylogenetic group B2 was prevalent in drug resistant UPEC strains. Pathogenic strains belonged to phylogenetic group B2 and D were found to have greater biofilm forming ability as compare to non-pathogenic commensal strains that belonged to phylogenetic group A. Our results indicate that biofilm formation vary in drug resistant UPEC belonged to different phylogenetic groups. This study indicates possible link between in vitro biofilm formation and phylogenetic groups of UPEC, therefore this knowledge might be helpful to predict the pathogenic potential of UPEC and help design strategies for controlling UTIs

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731-736In this study, marine isolate DK1-SA11 was identified and analyzed for antagonistic activity against fish pathogen along with its potential possible role as probiotic agent. The strain DK1-SA11 was identified on the basis of rec-A gene sequence similarity analysis and phylogenetic studies. Strain DK1-SA11 antagonistic activity against fish pathogens was analyzed by oxford cup agar diffusion method. Acute toxicity assay of strain DK1-SA11 with zebra fish (Danio rerio) was performed to evaluate the safety of strain for its future potential application as probiotic in aquaculture. recA gene sequencing analysis identified the strain as Bacillus sbutilis subsp. spizizenii strain DK1-SA11. Furthermore, strain DK1-SA11 has shown broad antagonistic activity against fish pathogens including Aeromonas hydrophila, A. salmonicida, Vibrio alginolyticus, V. anguillarum, V. campbellii, V. chagasii, V. chagasii, Photobacterium damsela, V. diazotrophicus, V. harveyi, V. ichthyoenteri, V. mediterranei, V. mimicus, V. parahaemolyticus, V. pomeroyi, V. splendidus, V. tubiashii, V. vulnificus and V. xuii. Acute toxicity results revealed that strain has neither fatal nor visible toxic effect to fish and the lethal concentration (LC50) of DK1-SA11 to the fish was > 108 CFU mL-1. Therefore, it has been concluded that Bacillus subtilis subsp. spizizenii strain DK1-SA11 might be a putative strain for prevention and control of fish and shellfish diseases, and could be use for probiosis

Relationship of cell surface hydrophobicity with biofilm formation and growth rate: A study on Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli

Objective(s): This study was designed to determine the relationship of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli isolates in multispecies biofilms and their individual phenotypic characters in biofilm consortia. Materials and Methods:  The subject isolates were recovered from different food samples and identified on the basis of growth on differential and selective media.  Tube methods, Congo-red agar method, and scanning electron microscopy (SEM) were used to study biofilms phenotypes. The hydrophobicity of the strains was evaluated by the adhesion to apolar solvent. Results: The results showed that E. coli dominated the pre-biofilm stage. It has been observed that E. coli adopted biofilm life much before S. aureus and P. aeruginosa. However, after adopting biofilm lifestyle, slowly and gradually, P. aeruginosa dominated the consortia and dispersed other stakeholders. The subject isolates of P. aeruginosa produce cis-2-decanoic acid to disperse or inhibit S. aureus and E. coli biofilms. Gas-chromatography and mass spectrometry results showed that cis-2-decanoic was higher in the co-culture condition and increased at late log-phase or at stationary phase. Although majority of S. aureus were unable to compete with P. aeruginosa, however, a minor population competed, survived, and persisted in biofilm consortia as small colony variants. The survivors showed higher expression of sigB and sarA genes. P. aeruginosa showed comparatively higher hydrophobic surface properties. Conclusion: Comparative analysis showed that cell surface hydrophobicity, growth rate, and small colony variants (SCVs) are correlated in biofilm consortia of the P. aeruginosa, S. aureus, and E. coli

Pseudomonas aeruginosa Response to Acidic Stress and Imipenem Resistance

The present study aimed to unveil the phenotypic heterogeneity and heteroresistance of P. aeruginosa to acidic stress and imipenem. Furthermore, the growth, morphology, and potential for biofilm formation of the subject isolates at different pHs were assessed. Isolates of P. aeruginosa were recovered from juice samples and confirmed by molecular analysis. Antibiotics sensitivity was evaluated using the Kirby&ndash;Bauer-disk diffusion method, and the MIC for imipenem was determined, followed by a biofilm formation assay and population analysis. Scanning electron microscopy (SEM) was used to visualize biofilm formation. The subject isolates persisted in an acidic environment and adopted a biofilm lifestyle. The population analysis assay indicated the presence of two distinct phenotypes, i.e., a normal colony phenotype (NCP) and slow growing colony phenotype (SGCP). NCP showed visible colonies after 48 h, while SGCP colonies appeared after 72 h of incubation. Both displayed heteroresistance to imipenem and susceptibility to other antibiotics. Biofilm formation at acidic pH was observed in both phenotypes. Interestingly, the recovery of SGCP was increased in an acidic environment. Biofilm consortia were highly resistant to imipenem. The present study indicated that P. aeruginosa persisted for a long time in an acidic environment, through phenotypic alteration. The subject isolates adopted a biofilm lifestyle and reduced metabolism, to neutralize the effects of acidic pH and imipenem toxicity. Interestingly, the biofilm consortia harbored metabolically active (NCP), as well as inactive populations, of (SGCP), to maintain an active growth and persistency. SGCP retained the potential to revert to NCP upon subsequent sub-culturing in plentiful nutrients and optimum conditions

Nanotubes Formation in P. aeruginosa

The present study discusses a biofilm-positive P. aeruginosa isolate that survives at pH levels ranging from 4.0 to 9.0. The biofilm consortia were colonized with different phenotypes i.e., planktonic, slow-growing and metabolically inactive small colony variants (SCVs). The lower base of the consortia was occupied by SCVs. These cells were strongly attached to solid surfaces and interconnected through a network of nanotubes. Nanotubes were observed at the stationary phase of biofilm indwellers and were more prominent after applying weight to the consortia. The scanning electron micrographs indicated that the nanotubes are polar appendages with intraspecies connectivity. The micrographs indicated variations in physical dimensions (length, width, and height) and a considerable reduction in volume due to weight pressure. A total of 35 cells were randomly selected. The mean volume of cells before the application of weight was 0.288 &micro;m3, which was reduced to 0.144 &micro;m3 after the application of weight. It was observed that a single cell may produce as many as six nanotubes, connected simultaneously to six neighbouring cells in different directions. The in-depth analysis confirmed that these structures were the intra-species connecting tools as no free nanotubes were found. Furthermore, after the application of weight, cells incapable of producing nanotubes were wiped out and the surface was covered by nanotube producers. This suggests that the nanotubes give a selective advantage to the cells to resist harsh environmental conditions and weight pressure. After the removal of weight and proper supply of nutrients, these phenotypes reverted to normal planktonic lifestyles. It is concluded that the nanotubes are not merely the phenomenon of dying cells; rather they are a connectivity tool which helps connected cells to tolerate and resist environmental stress

Biogenic Selenium Nanoparticles and Their Anticancer Effects Pertaining to Probiotic Bacteria—A Review

Selenium nanoparticles (SeNPs) can be produced by biogenic, physical, and chemical processes. The physical and chemical processes have hazardous effects. However, biogenic synthesis (by microorganisms) is an eco-friendly and economical technique that is non-toxic to human and animal health. The mechanism for biogenic SeNPs from microorganisms is still not well understood. Over the past two decades, extensive research has been conducted on the nutritional and therapeutic applications of biogenic SeNPs. The research revealed that biogenic SeNPs are considered novel competitors in the pharmaceutical and food industries, as they have been shown to be virtually non-toxic when used in medical practice and as dietary supplements and release only trace amounts of Se ions when ingested. Various pathogenic and probiotic/nonpathogenic bacteria are used for the biogenic synthesis of SeNPs. However, in the case of biosynthesis by pathogenic bacteria, extraction and purification techniques are required for further useful applications of these biogenic SeNPs. This review focuses on the applications of SeNPs (derived from probiotic/nonpathogenic organisms) as promising anticancer agents. This review describes that SeNPs derived from probiotic/nonpathogenic organisms are considered safe for human consumption. These biogenic SeNPs reduce oxidative stress in the human body and have also been shown to be effective against breast, prostate, lung, liver, and colon cancers. This review provides helpful information on the safe use of biogenic SeNPs and their economic importance for dietary and therapeutic purposes, especially as anticancer agents