Comparing invasive effects of five foodborne bacterial pathogens in human embryonic intestine 407 cells and human ileocecum HCT-8 cells

Objective: To refine the infectious doses of enteric bacterial pathogens in animal assays and vaccine clinical trials by studying the invasion kinetics of five bacterial pathogens with human intestinal cells.Methods: Utilizing in vitro cultured cell invasion assays with gentamicin-killing step,the invasive effects were analyzed in foodborne pathogens including Salmonella,Shigella, Yersinia, Escherichia coli(E. coli) O157 and opportunistic pathogens Citrobacter in human embryonic intestine 407 cells and ileocecum HCT-8 cells at multiplicities of infection(MOIs) of 0.04–4 000.00 E. coli HS served as a noninvasive control.Results: The study results showed that the bacterial invasive efficiency and the average number of internalized bacteria per host cell changed with different starting MOIs. Higher starting MOIs did not always produce more bacterial internalization. The bacterial invasion effects varied with different bacterial strains and host cell lines. E. coli O157:H7 did invade human ileocecum HCT-8 cells.Conclusions: This study shows that these bacteria possess different invasive patterns at various starting MOIs and also in different cell lines. The results could help to figure out the appropriate infectious doses of the bacteria in animal assays and in vaccine clinical trials. The bacterial invasion kinetics is also valuable in evaluating the safety and efficacy of live attenuated bacterial vaccines.

Characterization and Identification of Two Opportunistic Human Bacterial Pathogens in Rice

Burkholderia cepacia （Bc） and Pseudomonas aeruginosa （Pa） are both biocontrol agents in agriculture and opportunistic human pathogens in hospitals. Effective management and utilization practice is needed to understand their characteristics and distribution in rice. During the last decade, the two opportunistic human pathogens were detected in 631 samples of rice seed and 117 samples of rice plant in plain, highland and mountainous rice growing areas of China. Bc and Pa were primarily differentiated by common bacteriological characteristics and pathogenic tests and then identified into species by Biolog and FAME tests. However, the genotypes of Bc still could not be distinguished. It has been noted that the Bc and Pa mainly existed in rice root with the highest distribution frequency in plain areas （ 6.1% and 16.1%） and lowest in the mountainous areas （1.0% and 7.8%）.

Insights into effects of algae on decay and distribution of bacterial pathogens in recreational water:Implications for microbial risk management

The decay and distribution of bacterial pathogens in water is an important information for the health risk assessment to guide water safety management, and suspended algae might affect bacterial pathogens in water. This study established microcosms to investigate the effects of algae-related factors on the representative indicators and opportunistic pathogen species in water. We found that suspended algae increased the persistence of targeted species by 1-2 orders of magnitude of concentrations compared to microcosms without algae;and the effect of algae on microbial survival was affected by water nutrient levels(i.e., carbon, nitrogen and phosphorus), as the increased microbial persistence were correlated to the increased algae concentrations with more nutrient supplies. Moreover, decay and distribution profiles of representative species were determined. The three opportunistic pathogen species( Pseudomonas aeruginosa, Aeromonas hydrophila and Staphylococcus aureus) showed lower decay rates(0.82–0.98/day, 0.76–0.98/day, 0.63–0.87/day) largely affected by algae-related factors, while the enteric species( Escherichia coli and Enterococcus faecalis) had higher decay rates(0.94–1.31/day, 0.89–1.21/day) with little association with algae, indicating the propensity for attachment to algae is an important parameter in microbial fate. Together results suggest suspended algae played an evident role in the decay and distribution of bacterial pathogens, providing important implications regarding microbial safety in recreational water.

Protein secretion systems in bacterial pathogens

Many bacterial pathogens utilize specialized secretion systems to deliver virulence factors into the extracellular milieu. These exported effectors act to manipulate various processes of targeted cells in order to create a suitable niche for bacterial growth. Currently, seven different types of secretion system have been described, of which Type I - VI are mainly present in Gram-negative bacteria and the newly discovered Type VII system seems exclusive to Gram-positive species. This review summaries our current understanding on the architecture and transport mechanisms of each secretion apparatus. We also discuss recent studies revealing the roles that these secretion systems and their substrates play in microbial pathogenesis.

Isolation, Identification and Pathogenicity Evaluation of Pathogens of Soybean Bacterial Diseases

In order to research soybean bacterial diseases in Heilongiiang Province, a bacterial strain was isolated from diseased leaves of Suinong 14 collected from Harbin Yanjiagang farm. The pathogen had been carried out antibiotic resistance identification, molecular identification, re-inoculation identification and pathogenicity identification respectively. By Gram staining, pathogen inoculation test, 16S rDNA molecular identification, the pathogen was determined as Pseudomonas syringae and named Psgneau 2. The isolated strain presented resistance to 25, 50 and 100 μg/mL ampicillin and carbenicillin, but susceptible to spectinomycin, rifampicin, kanamycin, gentamicin, tetracycline and chloramphenicol. Ten soybean varieties were inoculated with Psgneau 2, in which Suinong 14 was more susceptible than other varieties and Hefeng 35 presented higher resistance to Psgneau 2.

Identification of Bacterial Fish Pathogens in Brazil by Direct Colony PCR and 16S rRNA Gene Sequencing

Intensive fish farming systems in Brazil have increased the disease incidence, mainly of bacterial origin, due to higher stocking density, high organic matter levels and poor quality of the aquatic environment that causes high mortality rates during outbreaks. The identification of pathogenic species using a fast and reliable method of diagnosis is essential for successful epidemiological studies and disease control. The present study evaluated the use of direct colony PCR in combination with 16S rRNA gene sequencing to diagnose fish bacterial diseases, with the goal of reducing the costs and time necessary for bacterial identification. The method was successful for all 178 isolates tested and produced bands with the same intensity as the standard PCR performed using pure DNA. In conclusion, the genetics methods allowed detecting the most common and important pathogens in Aquaculture, including 12 species of occurrence in Brazilian fish farms. The results of the present study constitute an advance in the available diagnostic methods for bacterial pathogens in fish farms.

In vitro activity of moxifloxacin and piperacillin/sulbactam against pathogens of acute cholangitis

AIM：To analyze the in vitro activity of moxifloxacin and piperacillin/sulbactam against pathogens isolated from patients with acute cholangitis. METHODS： In this prospective study a total of 65 patients with acute cholangitis due to biliary stone obstruction （n = 7）, benign biliary stricture （n = 16）, and malignant biliary stricture （n = 42） were investigated with regard to spectrum of bacterial infection and antibiotic resistance. Pathogens were isolated from bile cultures in all study patients. In 22 febrile patients, blood cultures were also obtained. In vitro activity of moxifloxacin and piperacillin/ sulbactam was determined by agar diffusion. RESULTS： Thirty-one out of 65 patients had positive bile and/or blood cultures. In 31 patients, 63 isolates with 17 different species were identified. The predominant strains were Enterococcus species （26/63）, Ecoli （13/63） and Klebsiella species （8/63）. A comparable in vitro activity of moxifloxacin and piperacillin/sulbactam was observed for E.coli and Klebsiella species. In contrast, Enterococcus species had higher resistances towards moxifloxacin. Overall bacteria showed antibiotic resistances in vitro of 34.9% for piperacillin/sulbactam and 36.5% for moxifioxacin.CONCLUSION： Enterococcus species, E.co/i and Klebsiella species were the most common bacteria isolated from bile and/or blood from patients with acute cholangitis. Overall, a mixed infection with several species was observed, and bacteria showed a comparable in vitro activity for piperacillin/sulbactam and moxifloxacin.

Natural History, Outcomes and Antibiotic Treatment for Ventilator-Associated Tracheobronchitis in Critical Ill Patients

We assessed incidence and outcomes of patients with ventilator-associated respiratory infections (VARI) due to tracheobronchitis (VAT) and pneumonia (VAP), including length of intensive care unit (ICU) stay and ventilator days. We also examined pathogens, rate of progression from VAT to VAP, and impact of antibiotic therapy for VAT. Data analysis included 234 patients, 100 patients (43%) had at least moderate (+++) bacterial growth in their semi-quantitative endotracheal aspirate (SQ-ETA) cultures. VAT and VAP were each diagnosed in 34 (15%) patients. Staphylococcus aureus was the most common pathogen isolated and had the highest rate of progression from VAT to VAP. Seven (21%) of the 34 patients were diagnosed with VAT that later progressed to VAP in averaged 3 days. Patients diagnosed with VAT had significantly more ventilator days (9 vs 6, p p < 0.001) and hospital days (22 vs 17, p < 0.001). No significant difference was observed in the clinical outcomes of the 25 VAT patients with timely, appropriate antibiotics compared to the 9 VAT patients who did not receive timely appropriate antibiotics. VAT was a risk factor for increased ventilator days, longer length of ICU and hospital stay. The time window from VAT to VAP allowed physicians to identify the pathogens and sensitivity profile needed to treat VAT with appropriate antibiotics. Data from well-designed studies were needed to assess the impact of early, appropriate antibiotic therapy for VAT, the choice of antibiotics, as well as the duration and route of administration.

The ubiquitin system： a critical regulator of innate immunity and pathogen-host interactions

The ubiquitin system comprises enzymes that are responsible for ubiquitination and deubiquitination, as well as ubiquitin receptors that are capable of recognizing and deciphering the ubiquitin code, which act in coordination to regulate almost all host cellular processes, including host-pathogen interactions. In response to pathogen infection, the host innate immune system launches an array of distinct antimicrobial activities encompassing inflammatory signaling, phagosomal maturation, autophagy and apoptosis, all of which are fine-tuned by the ubiquitin system to eradicate the invading pathogens and to reduce concomitant host damage. By contrast, pathogens have evolved a cohort of exquisite strategies to evade host innate immunity by usurping the ubiquitin system for their own benefits. Here, we present recent advances regarding the ubiquitin system-mediated modulation of host-pathogen interplay, with a specific focus on host innate immune defenses and bacterial pathogen immune evasion.

Receptor-like kinases and receptor-like proteins： keys to pathogen recognition and defense signaling in plant innate immunity

Plants have evolved multiple layers of defense against various pathogens in the environment. Receptor-like kinases/proteins （RLKs/RLPs） are on the front lines of the battle between plants and pathogens since they are present at the plasma membrane and perceive signature molecules from either the invading pathogen or damaged plant tissue. With a few notable exceptions, most RLKs/RLPs are positive regulators of plant innate immunity. In this review, we summarize recently discovered RLKs/RLPs that are involved in plant defense responses against various classes of pathogens, We also describe what is currently known about the mechanisms of RLK-mediated initiation of signaling via protein-protein interactions and phosphorylation.

Antimicrobial properties of marine seaweed,Sargassum muticum against human pathogens

Objective:To evaluate the antibacterial efficiency of the seaweed,Sargassum muticum(S.muticum)collected from Pudumadam,Ramanathapuram,Tamil Nadu,India.Methods:Crude solvent extracts of S.muticum were obtained by using Soxhlet extraction and the solvents like acetone,methanol and chloroform.These different extracts were tested against different human bacterial pathogens such as Micrococcus sp.,Staphylococcus aureus(methicillin resistance),Salmonella paratyphi B,Staphylococcus epidermis(3615),Enterobacter aerogenus(111),Klebsiella pneumonia(109),Shigella fleschneri(1457)(S.fleschneri),Proteus vulgaris(1771),Staphylococcus aureus(96)and Salmonella typhymurium(SP7)which were obtained from Microbial Type Culture Collection,Indian Institute of Microbial Technology,Chandigarh,India.Results:The results revealed that acetone extract had unveiled the maximum of 11 mm zone of inhibition at 40μL against S.fleschneri.Similar zone of inhibition(11 mm)was also observed at 50μL against Micrococcus sp.and S.fleschneri.Followed by acetone extract,chloroform extract also contributed 11 mm zone of inhibition against S.fleschneri and Salmonella paratyphi B at 40 and 50μL respectively.Besides,methanol extracts revealed meager antibacterial activity(9 mm).Conclusions:The present investigation suggests that the phytochemical constituent of the S.muticum might be suitable agents for the control of human deadly diseases.

Effect of fucoidan from Turbinaria ornata against marine ornamental fish pathogens

Objective:To evaluate the antimicrobial capacity of fucoidan from the brown seaweed Turbinaria ornata against the marine ornamental fish bacterial pathogens.Methods:Fucoidan was isolated by the ethanol extraction method and the functional groups were identified by Fourier Transform Infrared Spectroscopy analysis.Subsequently,structural characterization was done by 1H NMR analysis.In vitro antibacterial activity of fucoidan was performed by the agar plate diffusion method and Minimum Inhibitory Concentration.Results:The characteristic C-0-S bending vibration of sulfate substituent the axial C-4 was observed at 839 cm^(-1).Characterisitic signal of the fucoidan was detected in a different ppm of 1H NMR analysis.The maximum antibacterial activity(16.23±0.11)mm was obtained for Vibrio parahaemolyticus and the minimum activity(5.1±0.24)mm was recorded for Yersinia enterocolitica.The Minimum Inhibitory Concentration value was recorded between 2.5 to 10 mg/mL to the respective pathogens.Conclusions:The present study proved that fucoidan possessed the significant antibacterial activity against the tested fish bacterial pathogens.It could be further used as a natural antibiotic in an aquaculture system to control the bacterial diseases.However,the present study suggested that the further in vivo study is required to get the better understanding of the mode of action of fucoidan.

Efficiency of surface inactivation disinfectants for bacteria studied in an aquaculture microbiology laboratory

Routine microbial inactivation procedures used in microbiology laboratories must be verified.In this study,the efficacy of surface disinfection using 70%Isopropanol,0.45%Presept,and 1%Virkon was tested against 24 bacterial strains commonly handled in aquaculture microbiology laboratories.Isopropanol was ineffective against Nocardia asteroides NCIMB 1290,while Virkon was not effective against Aeromonas eucrenophila NCIMB 74 or Pediococcus acidilacti R52037.