Investigating the relationship between carbapenemase production and biofilm formation in Klebsiella pneumoniae clinical isolates.

OBJECTIVE: Carbapenemase production and biofilm formation in K. pneumoniae are crucial factors influencing the pathogenicity and antibiotic resistance of this bacterium. This study investigated the interplay between carbapenemase production and biofilm formation in K. pneumoniae clinical isolates. RESULTS: The distribution of biofilm-forming ability significantly differed between carbapenemase-producing (CP-Kp) (n = 52) isolates and carbapenemase-nonproducing (CN-Kp) isolates (n = 37), suggesting a potential link between carbapenemase production and biofilm formation. All the blaNDM-1-harbouring isolates demonstrated biofilm formation, with varying levels classified as strong (33.33%), moderate (22.22%), or weak (44.45%). blaNDM-1 and blaKPC-coharbouring isolates did not exhibit strong or moderate biofilm formation. blaNDM-1 and blaOXA-48-coharbouring isolates were predominantly moderate (48.65%), followed by weak (32.43%), with none showing strong biofilm production. These findings suggest a correlation between the presence of carbapenemases and biofilm-forming ability; however, the heterogeneity in biofilm-forming abilities associated with different carbapenemase types and the absence of strong biofilm producers in the detected carbapenemase combinations prompt a closer look at the complex regulatory mechanisms governing biofilm formation in CP-Kp isolates.

Sub-inhibitory concentrations of ceftriaxone induce morphological alterations and PIA-independent biofilm formation in Staphylococcus aureus.

The exposure of bacteria to sub-inhibitory concentrations of antibiotics is of biological significance since it can occur in vivo under many circumstances, including low-dose treatment, poor adherence to a regimen, poor drug penetration, drug-drug interactions, and antibiotic resistance of the pathogen. In this study, we investigated the effects of subinhibitory concentrations of four antibiotics: ampicillin, ceftriaxone, gentamicin, and norfloxacin, which are commonly used in clinical settings and on cell morphology and biofilm formation in Staphylococcus aureus as one of the leading causes of nosocomial and biofilm-associated infections. Nine clinical S. aureus biofilm-producing isolates and two known biofilm-producing reference strains, S. aureus ATCC 29213 and S. aureus ATCC 6538, were used in this study. Sub-MICs of beta-lactam antibiotics (ampicillin and ceftriaxone) significantly induced biofilm formation in S. aureus ATCC 29213 and S. aureus ATCC 6538 and in six clinical isolates out of the nine selected isolates when compared with the antibiotic-free control group (P < 0.05), with an approximately 2- to 2.5-fold increase. Gentamicin and norfloxacin induced biofilms in S. aureus ATCC 29213 and S. aureus ATCC 6538, while gentamicin and norfloxacin induced biofilms only in three and two of the nine tested isolates, respectively (P < 0.05). The chemical nature of the biofilm matrix produced by half the MIC of ceftriaxone in the six isolates that showed increased biofilm was all non-polysaccharide in composition (PIA-independent). Gene expression of biofilm-encoding genes atl and sarA in biofilms of the two tested strains (S. aureus ATCC 6538) and clinical strain (S. aureus 16) showed a significant upregulation after exposure to half MIC of ceftriaxone. Additionally, the bacterial cell morphological changes in planktonic cells caused by half MIC of ceftriaxone were evaluated by scanning electron microscopy, which demonstrated a significant cell enlargement when compared with the antibiotic-free control (P < 0.05), and some deformed cells were also noticed. In S. aureus clinical isolates, sub-MICs of ampicillin, ceftriaxone, gentamicin, and norfloxacin may stimulate substantial production of biofilm, which could have important clinical significance and make infection treatment challenges. Further, in vivo research is needed to fully comprehend how sub-MIC of antibiotics can affect biofilm formation in clinical settings. Additionally, more research is required to reveal the clinical implications of the morphological alterations in S. aureus brought on by exposure to ceftriaxone at concentrations below its MIC.

Comparative analysis of the ocular surface microbiome in type-1, type-2 diabetes mellitus and healthy individuals.

AIM: Ocular health greatly impacts the quality of life, and diabetes mellitus (DM) is a major cause of several visual diseases. Likewise, microbiomes have a pivotal role in eye health. The aim was to study the effect of DM, both type-1 (T1DM) and type-2 (T2DM) on the ocular microbiome. METHODS AND RESULTS: A total of 70 subjects were recruited for this study and divided into two main groups healthy nondiabetic (n = 18) and diabetic (28 T1DM and 24 T2DM). The ocular surface (OS) microbiome was more diverse in the healthy group than in the diabetic one. Taxonomic analysis revealed Proteobacteria as the main phylum (healthy nondiabetic 41.8%, T1DM 50.6%, and T2DM 52.5%), besides Streptococcus (healthy nondiabetic 16%, T1DM 26.75%, and T2DM 29.20%) and Paracoccus (healthy nondiabetic 17%, T1DM 34.85%, and T2DM 37.47%) as the main genera. No significant diversity was found between T1DM and T2DM on both phylum and genus levels; yet genera Brevundimonas and Leptotrichia were more significantly predominant in T1DM. CONCLUSION: Two pathogenic genera, Streptococcus and Paracoccus, were more predominant in the DM group than in the healthy one.

Hypolipidemic activity of lactic acid bacteria: Adjunct therapy for potential probiotics.

BACKGROUND: Individuals with hyperlipidemia are two times more likely to develop atherosclerotic cardiovascular disease (ASCVD) as opposed to those with controlled serum total cholesterol (TC) levels. Considering the documented adverse events of the current lipid-lowering medications which ultimately affect patient's compliance, substantial efforts have been made to develop new therapeutic strategies. Probiotics, on the other hand, are reported to have lipid-lowering activity with the added benefit of being generally well-tolerated making it an appealing adjuvant therapy. METHODS: A total of fifty Lactic acid bacteria (LAB) were isolated from raw milk (human and animal) and dairy products. Isolates demonstrating promising in vitro cholesterol removal capabilities were morphologically and biochemically characterized. Lastly, two bacterial candidates were selected for evaluation of their potential hypolipidemic activity using a laboratory animal model. Statistical differences between the means were analyzed by one-way analysis of variance (ANOVA) followed by Tukey's post-hoc test. A p-value < 0.05 was considered statistically significant. RESULTS: Most of the isolates demonstrated an in vitro cholesterol removal activity. The six LAB isolates showing the highest cholesterol removal activity (36.5-55.6%) were morphologically and biochemically identified as Lactobacillus, Pediococcus, and Lactococcus species. The results demonstrated two promising antihyperlipidemic candidates, a Lactococcus lactis ssp. lactis with an in vivo significant reduction of serum triglycerides (TG) levels by 34.3%, and a Pediococcus sp. that was able to significantly reduce both the serum TC and TG levels by 17.3% and 47.0%, respectively, as compared to the diet-induced hyperlipidemic animal group. CONCLUSION: This study further supports the growing evidence regarding the antihyperlipidemic activity among probiotics, presenting them as a promising therapeutic approach for the management of hyperlipidemia.

HilE is required for synergistic activation of SPI-1 gene expression in Salmonella enterica serovar Typhimurium.

BACKGROUND: Salmonella enterica serovar Typhimurium is an intestinal pathogen capable of infecting a wide range of animals. It initiates infection by invading intestinal epithelial cells using a type III secretion system encoded within Salmonella pathogenicity island 1 (SPI-1). The SPI-1 genes are regulated by multiple interacting transcription factors. The master regulator is HilD. HilE represses SPI-1 gene expression by binding HilD and preventing it from activating its target promoters. Previous work found that acetate and nutrients synergistically induce SPI-1 gene expression. In the present study, we investigated the role of HilE, nominally a repressor of SPI-1 gene expression, in mediating this response to acetate and nutrients. RESULTS: HilE is necessary for activation of SPI-1 gene expression by acetate and nutrients. In mutants lacking hilE, acetate and nutrients no longer increase SPI-1 gene expression but rather repress it. This puzzling response is not due to the BarA/SirA two component system, which governs the response to acetate. To identify the mechanism, we profiled gene expression using RNAseq in the wild type and a ΔhilE mutant under different growth conditions. Analysis of these data suggested that the Rcs system, which regulates gene expression in response to envelope stress, is involved. Consistent with this hypothesis, acetate and nutrients were able to induce SPI-1 gene expression in mutants lacking hilE and the Rcs system. CONCLUSIONS: While the exact mechanism is unknown, these results demonstrate the HilE, nominally a repressor of SPI-1 gene expression, can also function as an activator under the growth conditions investigated. Collectively, these results provide new insights regarding SPI-1 gene regulation and demonstrate that HilE is more complex than initially envisioned.

Assessment of the Prevalence of Non-Organ-Specific Autoantibodies in Egyptian Patients with HCV.

The relation between non-organ specific autoantibodies (NOSA) and hepatitis C virus (HCV) infection has been investigated within different communities resulting in different prevalence rates and patterns. The purpose of this study was to investigate the prevalence of some NOSA such as RF-IgG, ANA, ASMA, and LKM-1 in Egyptian patients with HCV group as compared with Egyptian healthy controls group. A total of 186 HCV positive serum samples in addition to 81 samples from healthy control were screened for the presence of some common autoantibodies (RF-IgG, ANA, ASMA, and LKM-1) using ELISA technique for ANA, ASMA, and LK-1 while RF-IgG was assayed by latex agglutination technique. The presence of these autoantibodies was tested in relation to some demographic variables and viral titers. Associations were assessed using logistic regression analysis adjusted for potential confounders. Among patients, 100 (53.7%) of 186 and 6 (7.4%) of 81 healthy control group were positive for at least one autoantibody. Furthermore, 2 patients (1%) were positive for three autoantibodies, whereas 22 patients (11.7%) were positive for 2 autoantibodies. The most prevalent autoantibody in anti-HCV-positive group was RF-IgG (87, 46.7%) followed by ASMA (26, 14%). The frequency of autoantibodies was bit higher in women as compared to men. Taken together, this study reports a non-significant difference in prevalence of NOSA between patients with HCV infection and healthy individuals except for ASMA. Likewise, no significant difference was found in prevalence of such autoantibodies when correlated with some demographic variables.

Synergistic action of SPI-1 gene expression in Salmonella enterica serovar typhimurium through transcriptional crosstalk with the flagellar system.

BACKGROUND: Salmonella enterica serovar Typhimurium is a common food-borne pathogen. S. enterica uses a type III secretion system encoded within Salmonella pathogenicity island 1 (SPI-1) to invade intestinal epithelial cells. A complex network of interacting transcription factors regulates SPI-1 gene expression. In addition, SPI-1 gene expression is coupled to flagellar gene expression. Both SPI-1 and flagellar gene expression are bistable, with co-existing populations of cells expressing and not expressing these genes. Previous work demonstrated that nutrients could be used to tune the fraction of cells expressing the flagellar genes. In the present study, we tested whether nutrients could also tune the fraction of cells expressing the SPI-1 genes through transcriptional crosstalk with the flagellar genes. RESULTS: Nutrients alone were not found to induce SPI-1 gene expression. However, when the cells were also grown in the presence of acetate, the concentration of nutrients in the growth medium was able to tune the fraction of cells expressing the SPI-1 genes. During growth in nutrient-poor medium, acetate alone was unable to induce SPI-1 gene expression. These results demonstrate that acetate and nutrients synergistically activate SPI-1 gene expression. The response to acetate was governed by the BarA/SirA two-component system and the response to nutrients was governed by transcriptional crosstalk with the flagella system, specifically through the action of the flagellar regulator FliZ. CONCLUSIONS: Acetate and nutrients are capable of synergistically activating SPI-1 gene expression. In addition, these signals were found to tune the fraction of cells expressing the SPI-1 genes. The governing mechanism involves transcriptional crosstalk with the flagellar gene network. Collectively, these results further our understanding of SPI-1 gene regulation and provide the basis for future studies investigating this complex regulatory mechanism.

Silver nanoparticles: Antimicrobial activity, cytotoxicity, and synergism with N-acetyl cysteine.

The fast progression of nanotechnology has led to novel therapeutic interventions. Antimicrobial activities of silver nanoparticles (Ag NPs) were tested against standard ATCC strains of Staphylococcus aureus (ATCC 9144), Escherichia coli (O157:H7), Pseudomonas aeruginosa (ATCC 27853), and Candida albicans (ATCC 90028) in addition to 60 clinical isolates collected from cancer patients. Antimicrobial activity was tested by disk diffusion method and MIC values for Ag NPs alone and in combination with N-acetylcysteine (NAC) against tested pathogens were determined by broth microdilution method. Ag NPs showed a robust antimicrobial activity against all tested pathogens and NAC substantially enhanced the antimicrobial activity of Ag NPs against all tested pathogens. Synergism between Ag NPs and NAC has been confirmed by checkerboard assay. The effect of Ag NPs on tested pathogens was further scrutinized by Transmission Electron Microscope (TEM) which showed disruption of cell wall in both bacteria and fungi. Ag NPs abrogated the activity of respiratory chain dehydrogenase of all tested pathogens and released muramic acid content from S. aureus in culture. The cytotoxic effect of Ag NPs alone and in combination with NAC was examined using human HepG2 cells and this revealed no cytotoxicity at MIC values of Ag NPs and interestingly, NAC reduced the cytotoxic effect of Ag NPs at concentrations higher than their MIC values. Taken together, Ag NPs have robust antimicrobial activity and NAC substantially enhances their antimicrobial activities against MDR pathogens which would provide a novel safe, effective, and inexpensive therapeutic approach to control the prevalence of MDR pathogens.

Inhibition of quorum sensing-mediated biofilm formation in Pseudomonas aeruginosa by a locally isolated Bacillus cereus.

Quorum sensing has been shown to play a crucial role in Pseudomonas aeruginosa pathogenesis where it activates expression of myriad genes that regulate the production of important virulence factors such as biofilm formation. Antagonism of quorum sensing is an excellent target for antimicrobial therapy and represents a novel approach to combat drug resistance. In this study, Chromobacterium violaceum biosensor strain was employed as a fast, sensitive, reliable, and easy to use tool for rapid screening of soil samples for Quorum Sensing Inhibitors (QSI) and the optimal conditions for maximal QSI production were scrutinized. Screening of 127 soil isolates showed that 43 isolates were able to breakdown the HHL signal. Out of the 43 isolates, 38 isolates were able to inhibit the violet color of the biosensor and to form easily detectable zones of color inhibition around their growth. A confirmatory bioassay was carried out after concentrating the putative positive cell-free lysates. Three different isolates that belonged to Bacillus cereus group were shown to have QSI activities and their QSI activities were optimized by changing their culture conditions. Further experiments revealed that the cell-free lysates of these isolates were able to inhibit biofilm formation by P. aeruginosa clinical isolates.

The border sequence of the balhimycin biosynthesis gene cluster from Amycolatopsis balhimycina contains bbr, encoding a StrR-like pathway-specific regulator.

Balhimycin, produced by the actinomycete Amycolatopsis balhimycina DSM5908, is a glycopeptide antibiotic highly similar to vancomycin, the antibiotic of 'last resort' used for the treatment of resistant Gram-positive pathogenic bacteria. Partial sequence of the balhimycin biosynthesis gene cluster was previously reported. In this work, cosmids which overlap the region of the characterized gene cluster were isolated and sequenced. At the 'left' end of the cluster, genes were identified which are involved in balhimycin biosynthesis, transport, resistance and regulation. The 'right' end border is defined by a putative 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (dahp) gene. The proximate gene is similar to a type I polyketide synthase gene of the rifamycin producer Amycolatopsis mediterranei indicating that another biosynthesis gene cluster might be located directly next to the balhimycin gene cluster. The newly identified StrR-like pathway-specific regulator, Bbr, was characterized to be a DNA-binding protein and may have a role in balhimycin biosynthesis. Purified N-terminally His-tagged Bbr shows specific DNA-binding to five promoter regions within the gene cluster. By in silico analysis and by comparison of the DNA sequences binding Bbr, conserved inverted repeat sequences for the Bbr-binding site are proposed. The putative Bbr consensus sequence differs from that published for StrR.