Modulation of host defence against bacterial and viral infections by omega-3 polyunsaturated fatty acids.

OBJECTIVES: Although n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) are used widely in the treatment of chronic inflammatory diseases, their effect in infectious disease requires a particular attention. METHODS: The present article discusses their anti-inflammatory and immune properties involved in the host defence and presents a systematic review of the effects of their oral administration on the prevention and outcome of experimental and clinical infections. RESULTS: At a dose corresponding to an human dose of 500 mg/day, n-3 LC-PUFAs intake is beneficial against experimental infections caused by extracellular pathogens including Streptococcus pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus by reducing inflammation, and reduces the incidence of pneumococcal infections in the elderly, but at 2-4-fold higher doses as occurs in some human intervention and/or during long-term it becomes detrimental in intestinal infections with Citrobacter rodentium or Helicobacter hepaticus by exacerbating anti-inflammatory response. They are also harmful against infections caused by intracellular pathogens as Mycobacterium tuberculosis, Salmonella, Influenza virus and Herpes simplex virus by affecting the immune cell response. CONCLUSION: The effects of n-3-LC-PUFAs on infections depend on the pathogen and the n-3 LC-PUFA dose and timing. Caution should be recommended for high-dose and long-term supplementation in humans.

Helicobacter hepaticus induces an inflammatory response in primary human hepatocytes.

Helicobacter hepaticus can lead to chronic hepatitis and hepatocellular carcinoma in certain strains of mice. Until now the pathogenic role of Helicobacter species on human liver tissue is still not clarified though Helicobacter species identification in human liver cancer was successful in case controlled studies. Therefore we established an in vitro model to investigate the interaction of primary human hepatocytes (PHH) with Helicobacter hepaticus. Successful co-culturing of PHH with Helicobacter hepaticus was confirmed by visualization of motile bacteria by two-photon-microscopy. Isolated human monocytes were stimulated with PHH conditioned media. Changes in mRNA expression of acute phase cytokines and proteins in PHH and stimulated monocytes were determined by Real-time PCR. Furthermore, cytokines and proteins were analyzed in PHH culture supernatants by ELISA. Co-cultivation with Helicobacter hepaticus induced mRNA expression of Interleukin-1 beta (IL-1ß), Tumor necrosis factor-alpha, Interleukin-8 (IL-8) and Monocyte chemotactic protein-1 (MCP-1) in PHH (p<0.05) resulting in a corresponding increase of IL-8 and MCP-1 concentrations in PHH supernatants (p<0.05). IL-8 and IL-1ß mRNA expression was induced in monocytes stimulated with Helicobacter hepaticus infected PHH conditioned media (p<0.05). An increase of Cyclooxygenase-2 mRNA expression was observed, with a concomitant increase of prostaglandin E2 concentration in PHH supernatants at 24 and 48 h (p<0.05). In contrast, at day 7 of co-culture, no persistent elevation of cytokine mRNA could be detected. High expression of intercellular adhesion molecule-1 on PHH cell membranes after co-culture was shown by two-photon-microscopy and confirmed by flow-cytometry. Finally, expression of Cytochrome P450 3A4 and albumin mRNA were downregulated, indicating an impairment of hepatocyte synthesis function by Helicobacter hepaticus presence. This is the first in vitro model demonstrating a pathogenic effect of a Helicobacter spp. on human liver cells, resulting in an inflammatory response with increased synthesis of inflammatory mediators and consecutive monocyte activation.

The Helicobacter hepaticus hefA gene is involved in resistance to amoxicillin.

BACKGROUND: Gastrointestinal infections with pathogenic Helicobacter species are commonly treated with combination therapies, which often include amoxicillin. Although this treatment is effective for eradication of Helicobacter pylori, the few existing reports are less clear about antibiotic susceptibility of other Helicobacter species. In this study we have determined the susceptibility of gastric and enterohepatic Helicobacter species to amoxicillin, and have investigated the mechanism of amoxicillin resistance in Helicobacter hepaticus. MATERIALS AND METHODS: The minimal inhibitory concentration (MIC) of antimicrobial compounds was determined by E-test and agar/broth dilution assays. The hefA gene of H. hepaticus was inactivated by insertion of a chloramphenicol resistance gene. Transcription was measured by quantitative real-time polymerase chain reaction. RESULTS: Three gastric Helicobacter species (H. pylori, H. mustelae, and H. acinonychis) were susceptible to amoxicillin (MIC < 0.25 mg/L). In contrast, three enterohepatic Helicobacter species (H. rappini, H. bilis, and H. hepaticus) were resistant to amoxicillin (MIC of 8, 16, and 6-64 mg/L, respectively). There was no detectable beta-lactamase activity in H. hepaticus, and inhibition of beta-lactamases did not change the MIC of amoxicillin of H. hepaticus. A H. hepaticus hefA (hh0224) mutant, encoding a TolC-component of a putative efflux system, resulted in loss of amoxicillin resistance (MIC 0.25 mg/L), and also resulted in increased sensitivity to bile acids. Finally, transcription of the hefA gene was not responsive to amoxicillin, but induced by bile acids. CONCLUSIONS: Rodents are frequently colonized by a variety of enterohepatic Helicobacter species, and this may affect their global health status and intestinal inflammatory responses. Animal facilities should have treatment strategies for Helicobacter infections, and hence resistance of enterohepatic Helicobacter species to amoxicillin should be considered when designing eradication programs.

Study of Helicobacter hepaticus in gallbladders with cholelithiasis and its sensitivity pattern.

BACKGROUND: Cholelithiasis is one of the most common digestive surgical disorders. The natural history of gallstone development is unknown. Bacteria are found in high concentration in bile and stone. It is difficult to ascertain whether bacterial infection of the bile arose before stone formation or vice versa. MATERIALS & METHODS: Prospective study was carried out in 30 cholecystectomy specimens of patients with cholelithiasis collected from 15th January 2005 to 24th July 2005 in Department of Pathology, Kathmandu Medical College Teaching Hospital. The samples were collected in a sterile vial containing 0.5% saline. A small piece of gallbladder was taken in Blood agar and Chocolate agar media for micro anaerobic culture at 370 degrees Celsius. The growth of the organism was observed after 48 hours of incubation. Gram stain and various biochemical tests were performed for the confirmation of Helicobacter hepaticus and its sensitivity pattern was studied. Histologically Helicobacter hepaticus was demonstrated in formalin fixed tissue sections using Warthin Starry Silver stain. RESULTS: A total of 76.66% cases showed growth positivity. Nitrofurantoin was found to be the most sensitive drug (95.7%) for Helicobacter hepaticus followed by Ciprofloxacin (91.3%), Cephalaxin (91.3%), Certriaxone (91.3%),Ofloxacin (82.6%), Amikacin (65.2%) and Norfloxacin (60.9%). Helicobacter hepaticus was least sensitive to Amoxycillin (57%). CONCLUSION: From this study, it is quite apparent that Helicobacter hepaticus infection is commonly associated (76.66%) with cholelithiasis. If the patients are treated with the sensitive antibiotics regularly and the infection, that is the number one cause for the precipitation of bile leading to the formation of gallstones, can be controlled, the incidence of cholelithiasis can be reduced so that the health care expenditure related to gallbladder disease can be reduced markedly.

The NADPH quinone reductase MdaB confers oxidative stress resistance to Helicobacter hepaticus.

An mdaB mutant strain in a quinone reductase (MdaB) of Helicobacter hepaticus type strain ATCC51449 was constructed by insertional mutagenesis, and the MdaB protein was purified and compared to the Helicobacter pylori enzyme. While wild type H. hepaticus cells could tolerate 6% O(2) for growth, the mdaB strain was clearly inhibited at this oxygen level. Disruption of the gene downstream of mdaB (HH1473) did not affect the oxidative stress phenotype of the strain. The mdaB mutant was also more sensitive to oxidative stress reagents such as H(2)O(2), cumene hydroperoxide, t-butyl hydroperoxide, and paraquat. All H. hepaticus mdaB strains isolated constitutively up-expressed another oxidative stress-combating enzyme, superoxide dismutase; this is in contrast to H. pylori mdaB strains. H. hepaticus MdaB is a flavoprotein catalyzing quinone reduction using a two-electron transfer mechanism from NAD(P)H to quinone. The H. hepaticus enzyme specific activity was far less than for the H. pylori enzyme purified in the same manner.