Interference of Pseudomonas strains in the identification of Helicobacter pylori

Anti-persister efficacy of colistin and meropenem against uropathogenic Escherichia coli is dependent on environmental conditions

Antibiotic persistence is a phenomenon observed when genetically susceptible cells survive long-term exposure to antibiotics. These 'persisters' are an intrinsic component of bacterial populations and stem from phenotypic heterogeneity. Persistence to antibiotics is a concern for public health globally, as it increases treatment duration and can contribute to treatment failure. Furthermore, there is a growing array of evidence that persistence is a 'stepping-stone' for the development of genetic antimicrobial resistance. Urinary tract infections (UTIs) are a major contributor to antibiotic consumption worldwide, and are known to be both persistent (i.e. affecting the host for a prolonged period) and recurring. Currently, in clinical settings, routine laboratory screening of pathogenic isolates does not determine the presence or the frequency of persister cells. Furthermore, the majority of research undertaken on antibiotic persistence has been done on lab-adapted bacterial strains. In the study presented here, we characterized antibiotic persisters in a panel of clinical uropathogenic Escherichia coli isolates collected from hospitals in the UK and Australia. We found that a urine-pH mimicking environment not only induces higher levels of antibiotic persistence to meropenem and colistin than standard laboratory growth conditions, but also results in rapid development of transient colistin resistance, regardless of the genetic resistance profile of the isolate. Furthermore, we provide evidence for the presence of multiple virulence factors involved in stress resistance and biofilm formation in the genomes of these isolates, whose activities have been previously shown to contribute to the formation of persister cells.

Colorimetric Detection of Urease-Producing Microbes Using an Ammonia-Responsive Flexible Film Sensor

Urease-producing (ureolytic) microbes have given rise to environmental and public health concerns because they are thought to contribute to emissions of ammonia and to be a virulence factor for infections. Therefore, it is highly important to have the ability to detect such microbes. In this study, a poly(dimethylsiloxane) (PDMS)-based colorimetric film sensor was employed for the detection of urease-producing microbes. The sensor was able to detect the enzyme activity of commercially available urease, as the color and absorbance spectrum of the sensor was observed to change upon being exposed to the reaction catalyzed by urease. The ratio of the absorbance of the sensor at 640 nm to that at 460 nm (A₆₄₀/A₄₆₀) was linearly proportional to the amount of urease present. The performance of the sensor was validated by the results of a sensitivity and selectivity analysis towards thirteen different bacterial strains. Based on the development of blue color of the sensor, the tested bacteria were classified as strongly positive, moderately positive, weakly positive, or negative urease producers. The response of the sensor to ureolytic bacteria was verified using the urease inhibitor phenyl phosphorodiamidate (PPDA). Additionally, the sensor achieved the selective detection of ureolytic bacteria even in the presence of non-ureolytic bacteria. In addition, a used sensor could be reverted to its original state by being subjected to simple aeration, and in this way the same sensor could be used at least five times for the detection of bacterial urease activity.

Microbial Diversity and Composition in Six Different Gastrointestinal Sites among Participants Undergoing Upper Gastrointestinal Endoscopy in Henan, China

The objective of this study was to describe and compare the dynamic microbiota characteristics in the gastrointestinal (GI) tract in Chinese participants via high-throughput sequencing techniques. The study collected saliva, esophageal swab, cardia biopsy, noncardia biopsy, gastric juice, and fecal specimens from 40 participants who underwent upper GI tract cancer screening in Linzhou (Henan, China) in August 2019. The V4 region of 16S rRNA genes was amplified and sequenced using the Illumina MiniSeq platform. The observed amplicon sequence variants (ASVs) gradually decreased from saliva to esophageal swab, cardia biopsy, noncardia biopsy, and gastric juice specimens and then increased from gastric juice to fecal specimens (P < 0.05). Each GI site had its own microbial characteristics that overlapped those of adjacent sites. Characteristic genera for each site were as follows: Neisseria and Prevotella in saliva, Streptococcus and Haemophilus in the esophagus, Helicobacter in the noncardia, Pseudomonas in gastric juice, Faecalibacterium, Roseburia, and Blautia in feces, and Weissella in the cardia. Helicobacter pylori-positive participants had decreased observed ASVs (cardia, P < 0.01; noncardia, P < 0.001) and Shannon index values (cardia, P < 0.001; noncardia, P < 0.001) compared with H. pylori-negative participants both in cardia and noncardia specimens. H. pylori infection played a more important role in the microbial composition of noncardia than of cardia specimens. In gastric juice, the gastric pH and H. pylori infection had similar additive effects on the microbial diversity and composition. These results show that each GI site has its own microbial characteristics that overlap those of adjacent sites and that differences and commonalities between and within microbial compositions coexist, providing essential foundations for the continuing exploration of disease-associated microbiota. IMPORTANCE Upper gastrointestinal (UGI) tract cancer is one of the most common cancers worldwide, while limited attention has been paid to the UGI microbiota. Microbial biomarkers, such as Fusobacteria nucleatum and Helicobacter pylori, bring new ideas for early detection of UGI tract cancer, which may be a highly feasible method to reduce its disease burden. This study revealed that each gastrointestinal site had its own microbial characteristics that overlapped those of adjacent sites. There were significant differences between the microbial compositions of the UGI sites and feces. Helicobacter pylori played a more significant role in the microbial composition of the noncardia stomach than in that of the cardia. Gastric pH and Helicobacter pylori had similar additive effects on the microbial diversity of gastric juice. These findings played a key role in delineating the microbiology spectrum of the gastrointestinal tract and provided baseline information for future microbial exploration covering etiology, primary screening, treatment, outcome, and health care products.

Colonization by Pseudomonas aeruginosa and Staphylococcus aureus of Antral Biopsy Specimens from Gastritis Patients Uninfected with Helicobacter Pylori

Purpose

Roles and incidence of some microorganisms that transiently or permanently colonize the human stomach are still unknown despite advances in gastroenterology. We aimed to examine the incidence of four microorganisms, Helicobacter pylori, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis, in the antral biopsy specimens of patients with gastroduodenal conditions.

Patients and Methods

Patients (67 females, 33 males; mean age = 49.5 years) were initially examined and diagnosed by a gastroenterologist at the Mehrad Hospital, Tehran, Iran. We enrolled those who underwent the upper gastrointestinal endoscopy because of gastroduodenal conditions. Two antral biopsy samples were taken by endoscopy; the first sample was used for the “rapid urease test” to confirm H. pylori. The second was used for DNA extraction and PCR analyses with specific, corresponding primer sets to establish the presence of the four microorganisms. Our study was approved by the Ethics Committee at the Tarbiat Modares University, Tehran.

Results

Based on pathology and endoscopy findings, we divided the patients into three groups: 62 presented with gastritis, 18 with duodenal ulcer, and 20 gastric ulcer. The number of patients with P. aeruginosa but without H. pylori significantly differed from the number of those co-infected with both microorganisms (P = 0.03). Additionally, a similar significance was found between the incidence of S. aureus in patients without H. pylori and those with both infections (P = 0.04). Our results indicated that a significant number of patients with gastritis were colonized with P. aeruginosa or S. aureus without being co-infected with H. pylori (P < 0.001). Interestingly, the incidence of colonization by P. aeruginosa of patients without H. pylori (45/49, 91.8%) was higher than that by S. aureus (28/49, 57%).

Conclusion

The number of patients without H. pylori but with P. aeruginosa or with S. aureus infection significantly differed from that with both infections, respectively. Our study thus shows that patients without H. pylori infection are prone to be colonized by P. aeruginosa or S. aureus, indicating that targeted antibiotic regimens are necessary for clinically treating them.

Neisseria flavescens: A Urease-Expressing Potential Pathogen Isolated from Gastritis Patients

Parasitic pathogens, such as H. pylori (Helicobacter pylori), are considered as primary elements for causing stomach infection and leading to chronic gastritis or ulcers. Here, an unreported urease- and oxidase-producing Neisseria flavescens-like bacteria was isolated from the gastroscopic biopsies of ¹⁴C-UBT-positive gastritis patients. The isolate expressed the activity of urease, which is a pathogenic factor and considered as a reliable marker for diagnosis of H. pylori infection. However, the isolate didn't express the key functional genes of H. pylori including vacA and hpaA, and also the morphological feature of isolate was significantly different with H. pylori. Eventually, the 16S rDNA of isolate was sequenced and its sequence shared about 99.8% similarity with the N. flavescens standard strains, but about 20.8% similarity with the H. pylori. Further study of antibiotics-resistance revealed the N. flavescens isolate is high resistant to metronidazole, but highly sensitive to ampicillin sodium. To summarize, a urease-expressing N. flavescens strain was isolated and identified from Chinese gastritis patients; the encouraging results provides an important reference for the further study of its pathogenicity and the reasonable diagnosis and use of antibiotics clinically.

The pathogenic potential of Pseudomonas fluorescens MFN1032 on enterocytes can be modulated by serotonin, substance P and epinephrine

Pseudomonas fluorescens is a commensal bacterium present at low level in the human digestive tract that has also been reported in many clinical samples (blood, urinary tract, skin, lung, etc.) and sometimes associated with acute opportunistic infections. It has recently been found that the human β-defensin-2 can enhance the pathogenic potential of P. fluorescens. In this study, we evaluated the effect of other intestinal molecules (5HT, SP and Epi) on growth and virulence of the clinical strain P. fluorescens MFN1032. We found that P. fluorescens MFN1032 growth was not mainly affected by these factors, but several modifications in the virulence behavior of this bacterium were observed. 5HT, SP and Epi were able to modulate the motility of P. fluorescens MFN1032. 5HT and SP had an effect on pyoverdin production and IL-8 secretion, respectively. Infection of Caco-2/TC7 cells with P. fluorescens MFN1032 pretreated by SP or Epi enhanced the permeability of the monolayers and led to a partial delocalization of F-actin to the cytoplasm. These findings show that some intestinal molecules can modulate the pathogenic potential of P. fluorescens MFN1032. We can hypothesize that this dialogue between the host and the human gut microbiota may participate in health and disease.

Pseudomonas fluorescens-like bacteria from the stomach: A microbiological and molecular study

AIM: To characterize oxidase- and urease-producing bacterial isolates, grown aerobically, that originated from antral biopsies of patients suffering from acid peptic diseases.

METHODS: A total of 258 antral biopsy specimens were subjected to isolation of bacteria followed by tests for oxidase and urease production, acid tolerance and aerobic growth. The selected isolates were further characterized by molecular techniques viz. amplifications for 16S rRNA using universal eubacterial and HSP60 gene specific primers. The amplicons were subjected to restriction analysis and partial sequencing. A phylogenetic tree was generated using unweighted pair group method with arithmetic mean (UPGMA) from evolutionary distance computed with bootstrap test of phylogeny. Assessment of acidity tolerance of bacteria isolated from antrum was performed using hydrochloric acid from 10^-7 mol/L to 10^-1 mol/L.

RESULTS: Of the 258 antral biopsy specimens collected from patients, 179 (69.4%) were positive for urease production by rapid urease test and 31% (80/258) yielded typical Helicobacter pylori (H. pylori) after 5-7 d of incubation under a microaerophilic environment. A total of 240 (93%) antral biopsies yielded homogeneous semi-translucent and small colonies after overnight incubation. The partial 16S rRNA sequences revealed that the isolates had 99% similarity with Pseudomonas species. A phylogenetic tree on the basis of 16S rRNA sequences denoted that JQ927226 and JQ927227 were likely to be related to Pseudomonas fluorescens (P. fluorescens). On the basis of HSP60 sequences applied to the UPGMA phylogenetic tree, it was observed that isolated strains in an aerobic environment were likely to be P. fluorescens, and HSP60 sequences had more discriminatory potential rather than 16S rRNA sequences. Interestingly, this bacterium was acid tolerant for hours at low pH. Further, a total of 250 (96.9%) genomic DNA samples of 258 biopsy specimens and DNA from 240 bacterial isolates were positive for the 613 bp amplicons by targeting P. fluorescens-specific conserved putative outer membrane protein gene sequences.

CONCLUSION: This study indicates that bacterial isolates from antral biopsies grown aerobically were P. fluorescens, and thus acid-tolerant bacteria other than H. pylori can also colonize the stomach and may be implicated in pathogenesis/protection.

Comparative evaluation of 3 selective media for primary isolation of Helicobacter pylori from gastric biopsies under routine conditions

This study evaluates 3 selective media (Pylori agar [bioMérieux, France], BD Helicobacter agar, modified [Becton Dickinson, USA], and an in-house medium) designed for Helicobacter pylori isolation. Ninety-eight strains were isolated from 400 gastric biopsies. The media were equally efficient for Helicobacter pylori's growth. However, contaminations were only observed using commercial media.

Pseudomonas aeruginosa: resistance and therapeutic options at the turn of the new millennium

Pseudomonas aeruginosa is a major cause of nosocomial infections. This organism shows a remarkable capacity to resist antibiotics, either intrinsically (because of constitutive expression of beta-lactamases and efflux pumps, combined with low permeability of the outer-membrane) or following acquisition of resistance genes (e.g., genes for beta-lactamases, or enzymes inactivating aminoglycosides or modifying their target), over-expression of efflux pumps, decreased expression of porins, or mutations in quinolone targets. Worryingly, these mechanisms are often present simultaneously, thereby conferring multiresistant phenotypes. Susceptibility testing is therefore crucial in clinical practice. Empirical treatment usually involves combination therapy, selected on the basis of known local epidemiology (usually a beta-lactam plus an aminoglycoside or a fluoroquinolone). However, therapy should be simplified as soon as possible, based on susceptibility data and the patient's clinical evolution. Alternative drugs (e.g., colistin) have proven useful against multiresistant strains, but innovative therapeutic options for the future remain scarce, while attempts to develop vaccines have been unsuccessful to date. Among broad-spectrum antibiotics in development, ceftobiprole, sitafloxacin and doripenem show interesting in-vitro activity, although the first two molecules have been evaluated in clinics only against Gram-positive organisms. Doripenem has received a fast track designation from the US Food and Drug Administration for the treatment of nosocomial pneumonia. Pump inhibitors are undergoing phase I trials in cystic fibrosis patients. Therefore, selecting appropriate antibiotics and optimising their use on the basis of pharmacodynamic concepts currently remains the best way of coping with pseudomonal infections.