John Hwa Lee

Bio: John Hwa Lee is an academic researcher from Chonbuk National University. The author has contributed to research in topics: Salmonella & Immune system. The author has an hindex of 33, co-authored 213 publications receiving 3934 citations.

Methicillin (Oxacillin)-Resistant Staphylococcus aureus Strains Isolated from Major Food Animals and Their Potential Transmission to Humans

Abstract: From May 2001 to April 2003, various types of specimens from cattle, pigs, and chickens were collected and examined for the presence of methicillin (oxacillin)-resistant Staphylococcus aureus (MRSA). S. aureus was isolated and positively identified by using Gram staining, colony morphology, tests for coagulase and urease activities, and an API Staph Ident system. Among 1,913 specimens collected from the animals, 421 contained S. aureus; of these, 28 contained S. aureus resistant to concentrations of oxacillin higher than 2 μg/ml. Isolates from 15 of the 28 specimens were positive by PCR for the mecA gene. Of the 15 mecA-positive MRSA isolates, 12 were from dairy cows and 3 were from chickens. Antimicrobial susceptibility tests of mecA-positive MRSA strains were performed by the disk diffusion method. All isolates were resistant to members of the penicillin family, such as ampicillin, oxacillin, and penicillin. All isolates were also susceptible to amikacin, vancomycin, and trimethoprim-sulfamethoxazole. To determine molecular epidemiological relatedness of these 15 animal MRSA isolates to isolates from humans, random amplified polymorphic DNA (RAPD) patterns were generated by arbitrarily primed PCR. The RAPD patterns of six of the isolates from animals were identical to the patterns of certain isolates from humans. The antibiotypes of the six animal isolates revealed types similar to those of the human isolates. These data suggested that the genomes of the six animal MRSA isolates were very closely related to those of some human MRSA isolates and were a possible source of human infections caused by consuming contaminated food products made from these animals.

Bacterial flagellin-a potent immunomodulatory agent.

Abstract: Flagellin is a subunit protein of the flagellum, a whip-like appendage that enables bacterial motility. Traditionally, flagellin was viewed as a virulence factor that contributes to the adhesion and invasion of host cells, but now it has emerged as a potent immune activator, shaping both the innate and adaptive arms of immunity during microbial infections. In this review, we summarize our understanding of bacterial flagellin and host immune system interactions and the role flagellin as an adjuvant, anti-tumor and radioprotective agent, and we address important areas of future research interests.

Electrospun Antimicrobial Polyurethane Nanofibers Containing Silver Nanoparticles for Biotechnological Applications

Abstract: In this study, a new class of polyurethane (PU) nanofibers containing silver (Ag) nanoparticles (NPs) was synthesized by electrospinning. A simple method that did not depending on additional foreign chemicals was used to self synthesize the silver NPs in/on PU nanofibers. The synthesis of silver NPs was carried out by exploiting the reduction ability of N,N-dimethylformamide (DMF), which is used mainly to decompose silver nitrate to silver NPs. Typically, a sol-gel consisting of AgNO3/PU was electrospun and aged for one week. Silver NPs were created in/on PU nanofibers. SEM confirmed the well oriented nanofibers and good dispersion of pure silver NPs. TEM indicated that the Ag NPs were 5 to 20 nm in diameter. XRD demonstrated the good crystalline features of silver metal. The mechanical properties of the nanofiber mats showed improvement with increasing silver NPs content. The fixedness of the silver NPs obtained on PU nanofibers was examined by harsh successive washing of the as-prepared mats using a large amount of water. The results confirmed the good stability of the synthesized nanofiber mats. Two model organisms,E. coli andS. typhimurium, were used to check the antimicrobial influence of these nanofiber mats. Subsequently, antimicrobial tests indicated that the prepared nanofibers have a high bactericidal effect. Accordingly, these results highlight the potential use of these nanofiber mats as antimicrobial agents.

Induction of Interleukin-12 and Gamma Interferon Requires Tumor Necrosis Factor Alpha for Protective T1-Cell-Mediated Immunity to Pulmonary Cryptococcus neoformans Infection

Abstract: The development of T1-cell-mediated immunity is required to clear a pulmonary Cryptococcus neoformans infection. The objective of these studies was to determine the mechanism by which tumor necrosis factor alpha (TNF-α) augments the development of pulmonary T1 immunity to C. neoformans infection. TNF-α expression was detected in lavage sample cells at days 2, 3, and 7 following C. neoformans infection. The numbers of CFU in the lung were not different between control and anti-TNF-α-treated mice at any time point examined during the afferent phase of the response (days 0 to 7). However, neutralization of TNF-α prevented the initiation of pulmonary clearance during the efferent phase of the response (day 14). Administration of anti-TNF-α monoclonal antibody (day 0) diminished the lung levels of TNF-α, interleukin-12 (IL-12), and gamma interferon (IFN-γ) induced by C. neoformans at day 7 postinfection. Neutralization of TNF-α (day 0) also altered the IFN-γ/IL-4 ratio in the lung-associated lymph nodes at day 7 following C. neoformans infection. Anti-TNF-α-treated mice developed a pulmonary eosinophilia at day 14 postinfection. Consistent with the pulmonary eosinophilia, anti-TNF-α-treated mice exhibited elevated serum immunoglobulin E and inhibition of the anticryptococcal delayed-type hypersensitivity response, indicating a shift toward a T2 response. Neutralization of IL-12 also prevented lung leukocyte production of IFN-γ in response to the infection. These findings demonstrate that afferent-phase TNF-α production is essential for the induction of IL-12 and IFN-γ and neutralization of early TNF-α results in a T2 shift of the T1/T2 balance of antifungal immunity.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic.

Abstract: Summary: Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

The challenge of emerging and re-emerging infectious diseases

Abstract: Infectious diseases have for centuries ranked with wars and famine as major challenges to human progress and survival. They remain among the leading causes of death and disability worldwide. Against a constant background of established infections, epidemics of new and old infectious diseases periodically emerge, greatly magnifying the global burden of infections. Studies of these emerging infections reveal the evolutionary properties of pathogenic microorganisms and the dynamic relationships between microorganisms, their hosts and the environment.

Food Animals and Antimicrobials: Impacts on Human Health

Abstract: Antimicrobials are valuable therapeutics whose efficacy is seriously compromised by the emergence and spread of antimicrobial resistance. The provision of antibiotics to food animals encompasses a wide variety of nontherapeutic purposes that include growth promotion. The concern over resistance emergence and spread to people by nontherapeutic use of antimicrobials has led to conflicted practices and opinions. Considerable evidence supported the removal of nontherapeutic antimicrobials (NTAs) in Europe, based on the "precautionary principle." Still, concrete scientific evidence of the favorable versus unfavorable consequences of NTAs is not clear to all stakeholders. Substantial data show elevated antibiotic resistance in bacteria associated with animals fed NTAs and their food products. This resistance spreads to other animals and humans-directly by contact and indirectly via the food chain, water, air, and manured and sludge-fertilized soils. Modern genetic techniques are making advances in deciphering the ecological impact of NTAs, but modeling efforts are thwarted by deficits in key knowledge of microbial and antibiotic loads at each stage of the transmission chain. Still, the substantial and expanding volume of evidence reporting animal-to-human spread of resistant bacteria, including that arising from use of NTAs, supports eliminating NTA use in order to reduce the growing environmental load of resistance genes.

Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors

Abstract: In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.

Diseases of Poultry

Abstract: VERY few veterinary surgeons have thought fit to write a book on diseases of poultry. Mr. Ernest Gray has done justice to the subject and is to be congratulated on his effort. A book of this size, written by one with specialized knowledge, will add to the value of any library or private bookshelf. Diseases of Poultry Their Aetiology, Diagnosis, Treatment and Control; with a Section on the Normal Anatomy and Physiology of the Fowl. By Ernest Gray. (Lockwood's Agricultural and Horticultural Handbooks.) Pp. x + 198 + 16 plates. (London: Crosby Lockwood and Son, Ltd., 1940.) 9s. 6d. net.