Bacteriocidal Activity Research Articles

Structure–activity relationships of the phosphonate antibiotic dehydrophos

Synthetic derivatives of the phosphonate antibiotic dehydrophos were tested for antimicrobial activity. Both the phosphonate monomethyl ester and the vinyl phosphonate moiety proved to be important for bacteriocidal activity of the natural product.

Polymyxin B Identified as an Inhibitor of Alternative NADH Dehydrogenase and Malate: Quinone Oxidoreductase from the Gram-positive Bacterium Mycobacterium smegmatis

Tuberculosis is the leading cause of death due to a single infectious agent in the world and the emergence of multidrug-resistant strains prompted us to develop new drugs with novel targets and mechanism. Here, we screened a natural antibiotics library with Mycobacterium smegmatis membrane-bound dehydrogenases and identified polymyxin B (cationic decapeptide) and nanaomycin A (naphtoquinone derivative) as inhibitors of alternative NADH dehydrogenase [50% inhibitory concentration (IC(50)) values of 1.6 and 31 microg/ml, respectively] and malate: quinone oxidoreductase (IC(50) values of 4.2 and 49 microg/ml, respectively). Kinetic analysis on inhibition by polymyxin B showed that the primary site of action was the quinone-binding site. Because of the similarity in K(m) value for ubiquinone-1 and inhibitor sensitivity, we examined amino acid sequences of actinobacterial enzymes and found possible binding sites for L-malate and quinones. Proposed mechanisms of polymyxin B and nanaomycin A for the bacteriocidal activity were the destruction of bacterial membranes and production of reactive oxygen species, respectively, while this study revealed their inhibitory activity on bacterial membrane-bound dehydrogenases. Screening of the library with bacterial respiratory enzymes resulted in unprecedented findings, so we are hoping that continuing efforts could identify lead compounds for new drugs targeting to mycobacterial respiratory enzymes.

Efficacy of Monotherapy in the Treatment of Pseudomonas Ventilator-Associated Pneumonia in Patients With Trauma

Controversy persists regarding the optimal treatment regimen for Pseudomonas ventilator-associated pneumonia (VAP). Combination antibiotic therapy is used to broaden the spectrum of activity of empiric treatment and provide synergistic bacteriocidal activity. The relevance of such "synergy" is commonly supposed but poorly supported. The purpose of this study was to evaluate the efficacy of monotherapy in the treatment of Pseudomonas VAP as measured by microbiological resolution. Patients admitted to the trauma intensive care unit during a 36-month period with gram-negative VAP diagnosed on initial bronchoalveolar lavage (BAL) (> or = 10(5) colony forming units [CFU]/mL) were evaluated. All patients received empiric antibiotic monotherapy based on the duration of intensive care unit stay. Patients with Pseudomonas VAP were identified and appropriate monotherapy was selected. Repeat BAL was performed on day 4 of appropriate antibiotic therapy to determine efficacy. Microbiological resolution was defined as < or = 10(3) CFU/mL. Combination therapy with an aminoglycoside was reserved for patients with either persistent positive or increasing colony counts on repeat BAL. Recurrence was defined as > or = 10(5) CFU/mL on subsequent BAL after 2 weeks of appropriate therapy. One hundred ninety-six patients were identified with late gram-negative VAP. There were 84 patients with Pseudomonas VAP. Monotherapy achieved microbiological resolution in 79 patients (94.1%) with zero recurrence. Thirty-six isolates were completely eradicated at repeat BAL. Five patients (5.9%) required combination therapy to achieve resolution. Monotherapy in the treatment of Pseudomonas VAP has an excellent success rate in patients with trauma. Empiric monotherapy therapy should be modified once susceptibility of the microorganism is documented (all isolates were sensitive to cefepime) and antibiotic choice should be based on local patterns of susceptibilities. The routine use of combination therapy for synergy is unnecessary. Combination therapy should be reserved for patients with persistent microbiological evidence of Pseudomonas VAP despite adequate therapy.

Triclosan derivatives: towards potent inhibitors of drug-sensitive and drug-resistant Mycobacterium tuberculosis.

Triclosan has been previously shown to inhibit InhA, an essential enoyl acyl carrier protein reductase involved in mycolic acid biosynthesis, the inhibition of which leads to the lysis of Mycobacterium tuberculosis. Using a structure-based drug design approach, a series of 5-substituted triclosan derivatives was developed. Two groups of derivatives with alkyl and aryl substituents, respectively, were identified with dramatically enhanced potency against purified InhA. The most efficacious inhibitor displayed an IC(50) value of 21 nM, which was 50-fold more potent than triclosan. X-ray crystal structures of InhA in complex with four triclosan derivatives revealed the structural basis for the inhibitory activity. Six selected triclosan derivatives were tested against isoniazid-sensitive and resistant strains of M. tuberculosis. Among those, the best inhibitor had an MIC value of 4.7 microg mL(-1) (13 microM), which represents a tenfold improvement over the bacteriocidal activity of triclosan. A subset of these triclosan analogues was more potent than isoniazid against two isoniazid-resistant M. tuberculosis strains, demonstrating the significant potential for structure-based design in the development of next generation antitubercular drugs.

Food Science Education Publications and Websites

Bird The purpose of this column is to highlight innovative publications and websites in food science education. If you know of a website or a recent publication that you believe other readers would like to know about, please submit the full text of the article or the URL for the website and an annotation of not more than 125 words. We welcome your resources and comments on this column. Material should be submitted to: Jim Bird, Science & Engineering Center, Fogler Library, Univ. of Maine, Orono, ME 04469, or e-mail to Jim.Bird@umit.maine.edu. If e-mailing, please put “JFSE submission” in the subject line. College English (National Council of Teachers of English). 2008. Special topic: Food. 70(4):345–436. This issue of College English is devoted to food writing. Papers include: “Consuming prose: The delectable rhetoric of food writing”, “Food memoirs: What they are, why they are popular, and why they belong in the literature classroom”, and “Books that cook: Teaching food and food literature in the English classroom”. For a very brief description of each article in this special topic issue go to http://www.indiana.edu/~cedialog/?cat=10 Koch P, Barton AC, Contento I, and Crabtree M. 2008. Farm to table and beyond: Helping students make sense of the global food system. Sci Scope 31(9):36–9. The authors describe an activity, part of the Farm to Table & Beyond curriculum, where grade 5 to 6 students diagram the production and processing of food. This activity, utilizing observation and discussion, helps students put the food system into a biological and environmental context. Topics explored in the curriculum include food preservation, environmental effects of food systems, and transportation issues related to food. McDonald J. 2008. Enhancing food-safety education through shared teaching resources. J Vet Med Educ 35(2):207–11. The author describes an innovative project, Design to Dissemination (D2D), developed for veterinary teaching faculty to provide them with food safety resources. The information (called “learning objects”) is presented in various formats including text, animation, audio, powerpoint, and video. The project has three objectives (from p. 208–209): “To provide institutions, faculty, and students with high-quality, clinically relevant, interactive educational materials….; To provide easy access to the materials….; To help faculty use learning objects effectively to build or enhance a course.” A logon is required to fully utilize the site's capabilities but users can create an account. To view this ongoing project, go to the following website: Veterinary Food Safety Education Learning Object Repository http://webcls.utmb.edu/d2d Segner S and Scholthof K-BG. 2007. Environmental microbiology: Bacteria & fungi on the foods we eat. The Am Biol Teach 69(3):149–57. Utilizing fruits and vegetables, a laboratory exercise was developed for the undergraduate course “Pathogens, the Environment, and Society” at Texas A&M Univ. Students concentrated on the identity of cosmopolitan bacteria and fungi on both washed and unwashed fruits and vegetables. Detailed laboratory protocols are presented. The author presents a number of internet resources useful in lab and lecture preparation. Sorgo A, Hajdinjak Z, and Briski D. 2008. The journey of a sandwich: computer-based laboratory experiments about the human digestive system in high school biology teaching. Adv Physiol Educ 32(1):92–9. Based on results from a questionnaire, the authors found that high school students were most successful when hands-on, computer-based experiments were used to teach human digestion. Topics taught included jaw chewing force, dissolution speed, enzymatic breakdown of food, bacteriocidal activity of hydrochloric acid, and importance of the intestine lining's surface. These experiments will be upgraded in the future, based on student input. The authors plan to design experiments to teach other systems. Dairy Science and Food Technology http://www.dairyscience.info (accessed 11/17/2008) This website contains information on the industrial uses of lactic acid bacteria and their bacteriophages, antimicrobial systems in milk, and factors influencing the quality and yield of cheese. There are also sections on starter cultures, probiotics, modeling in food technology, and a summary of information on modified atmosphere packaging. The articles on general food technology include labeling, nutritional claims, wine making and thermal processing. There are calculators and models, such as one for predicting the grade value of Cheddar cheese, theoretical yield of cheese, and a calculator using linear programming for calculating ice cream mixes. The site is aimed at students and practitioners in dairy science and technology, and there are discussion area, extensive links, and literature citations. There are also significant sections aimed at helping students write papers and theses including a Harvard-style reference generator. (Contributed by Dr. Michael Mullan, Head of Higher Education Branch, Greenmount Campus, College of Agriculture, Food and Rural Enterprise, Antrim BT41 4PU, Northern Ireland. michael.mullan@dardni.gov.uk)

Synthesis of agarose-metal/semiconductor nanoparticles having superior bacteriocidal activity and their simple conversion to metal-carbon composites

Agarose, a naturally occurring biopolymer is used for the stabilization of metal, semiconductor nanoparticles. Ag and Cu nanoparticles stabilized in agarose matrix show excellent antibacterial activity against E. coli bacteria. The well dispersed metal nanoparticles within the agarose composite films can be readily converted to carbon-metal composites of catalytic importance.

Alpinia katsumadai hayata prevents mouse sepsis induced by cecal ligation and puncture through promoting bacterial clearance and downregulating systemic inflammation

Sepsis continues to be a challenge in clinic. Therapeutic strategies focus on local host defenses and the inhibition of overwhelming inflammation response. The present study aimed to investigate the protective effects and the underlying mechanisms of the ethanol extract of Alpinia katsumadai Hayata seeds (EAKH) on polymicrobial sepsis induced by cecal ligation and puncture (CLP) in mice. It was shown that oral administration of EAKH at 1 h before and 2 h after CLP significantly elevated the survival rate and the mean arterial pressure of mice. Histological examination and serum ALT/AST assessment demonstrated that EAKH protected the animals from lung and liver tissue injury and dysfunction. Although EAKH was devoid of direct bacteriostatic or bacteriocidal activities, it facilitated peritoneal bacteria clearance and increased leukocyte migration into peritoneal cavity of septic mice. Furthermore, EAKH remarkably decreased serum pro-inflammatory cytokine (TNF-alpha, IL-1beta and NO) levels in septic mice. These findings demonstrated that EAKH has preventive effects on mouse sepsis induced by CLP, which may be attributed to elevating local defense via promoting leukocyte migration to infection focus and attenuating systemic inflammation.

Discovery of novel nitrobenzothiazole inhibitors for Mycobacterium tuberculosis ATP phosphoribosyl transferase (HisG) through virtual screening.

HisG is an ATP-phosphoribosyl transferase (ATPPRTase) that catalyzes the first step in the biosynthetic pathway for histidine. Among the enzymes in this pathway, only HisG represents a potential drug target for tuberculosis. Only a few inhibitors with limited potency for HisG are currently known. To discover more potent and diverse inhibitors, virtual screening was performed. The crystal structure of M. tuberculosis HisG has been solved and reveals a large, solvent-exposed active site with subsites for ATP and PRPP substrates. Two docking algorithms, GOLD and FLEXX, were used to screen two large libraries, Chembridge and NCI, containing over 500000 compounds combined. An initial subset of top-ranked compounds were selected and assayed, and seven were found to have enzyme inhibition activity at micromolar concentrations. Several of the hits contained a nitrobenzothiazole fragment, which was predicted to dock into the monophosphate-binding loop, and this binding mode was confirmed by crystallographic evidence. A secondary screen was performed to identify compounds with similar structures. Several of these also exhibited micromolar inhibition. Furthermore, two of the compounds showed bacteriocidal activity in a whole-cell assay against Mycobacterium smegmatis.

Network Relationships of Bacteria in a Stable Mixed Culture

We investigated the network relationships of bacteria in a structurally stable mixed culture degrading cellulose. The mixed culture consists of four bacterial strains (a cellulose-degrading anaerobe [strain S], a saccharide-utilizing anaerobe [strain F], a peptide- and acetate-utilizing aerobe [strain 3] and a peptide-, glucose-, and ethanol-utilizing aerobe [strain 5]). Interspecies interactions were examined by analyzing the effects of culture filtrates on the growth of the other strains and by comprehensively analyzing population dynamics in the mixed-culture systems with all possible combinations of the four bacterial strains. The persistence of strain S depends on the effects of strain 5. However, strain 5 is a disadvantaged strain because strain 3 has bacteriocidal activity on strain 5. The extinction of strain 5 is indirectly prevented by strain F that suppresses the growth of strain 3. Although strain F directly has suppressive effects on the growth of strain S, strain F is essential for the persistence of strain S, considering the indirect effects (maintaining strain 5, which is essential for the survival of strain S, by inhibiting strain 3). These indirect relationships form a bacterial network in which all the relationships including suppressive effects were well balanced to maintain the structural stability. In addition to direct metabolite interactions, such kind of indirect relationships could have a great impact on microbial community structure in the natural environment.

Bactericidal activity of denture-cleaning formulations against planktonic health care–associated and community-associated methicillin-resistant Staphylococcus aureus

The aim of this study was to examine the survival dynamics of several epidemic health care-associated (HA) and community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) in planktonic state in widely employed denture-cleaning solutions. The bacteriocidal activity of five widely employed denture-cleaning formulations were examined against five phage-types of HA-MRSA (EMRSA 15, EMRSA 16, Irish 1, Irish 2, unique type), as well as a CA-MRSA strain, in this study. Viable MRSA cells (circa 10(5) cfu/mL) were coincubated with optimum recommended working concentrations of denture-cleaning solutions for up to 17 hours (overnight). Recovery experiments were unable to isolate any of the inoculated MRSA organisms 10 minutes post inoculation. The significance and impact of this short study indicates that HA-MRSA and CA-MRSA are not able to remain culturable for 10 minutes in planktonic form, in commonly used denture-cleaning formulations widely available on the UK High Street, suggesting that these formulations may be useful in lowering the numbers of MRSA. Further work is however required to examine the more complex survival dynamics of MRSA in naturally derived denture biofilm, associated with dental plaque and the use of such cleaning formulations.

Surgical laser use in implantology and endodontics

The use of surgical lasers has been advocated to aid in the placement and second stage recovery of dental implants, together with soft tissue contouring. In addition, laser use has been suggested as an aid in decontamination of the implant surface in cases of peri-implantitis. In endodontics, the association of laser energy with dentine hypersensitivity, bacteriocidal action and pulp-capping, has led to a growing number of reports as to its beneficial use, together with claims of morphological changes in the canal wall, to enhance endodontic treatment success.

Tobacco Smoke Exposure Disrupts CCL20 Production and Antimicrobial Activity by Respiratory Epithelial Cells. (B173)

Abstract The mechanism whereby tobacco smoke (TS) exposure increases the risk of infection is unknown. We tested the hypothesis that exposure to TS suppresses production of respiratory tract CCL20, a defensin-like antimicrobial peptide characterized primarily as a chemokine. When nasal washes from human subjects exposed to TS within the last two years were compared to nasal washes from individuals not exposed for more than 20 years, the latter had approximately six times more CCL20 than the former. In studies of polarized human bronchial epithelial cells (Beas-2b) grown in antibiotic-free media, CCL20 was released preferentially to the apical surface of the cell cultures. When cells were treated with tobacco smoke extract (TSE), CCL20 mRNA and secreted protein levels decreased by approximately half. In bacterial survival assays conducted with apically-collected conditioned media, media collected from TSE-treated cells killed significantly fewer CFU than media from non-TSE-treated cells; assays conducted with media treated with anti-CCL20 antibody resulted in abolition of its bacteriocidal activity. Statistically similar results were obtained in assays using rhCCL20 instead of apical media. These results demonstrate that TS exposure disrupts important antimicrobial activity and signaling by respiratory epithelial cells, a condition which may lead to increased susceptibility to infection.

Effects of Heating, Storage, and Ultraviolet Exposure on Antimicrobial Activity of Garlic Juice

This study was designed to investigate the effect of heating, storage, and ultraviolet exposure on antimicrobial activity of garlic juice and its bacteriocidal activity against common human pathogens. Antimicrobial activity of fresh garlic juice was tested against Escherichia coli, Staphylococcus aureus, Streptococcus hemolyticus B, S. hemolyticus A, Klebsiella sp., Shigella dysenteriae, and Candida albicans using the disc method. The dilution method was performed by addition of garlic juice to broth media to obtain 1-100% concentrations as vol/vol or wt/vol. Garlic juice was used after 24 hours of storage at 4 degrees C, heating to 100 degrees C for 5 minutes, 10 minutes, 30 minutes, and 60 minutes, heating to 80 degrees C for 60 minutes, and 4 hours of exposure to ultraviolet light. Re-culture of specimens taken from garlic-induced negative media was performed in fresh broth free of garlic juice. Results showed that all the isolates were sensitive to fresh garlic juice; the most sensitive was C. albicans, and the least sensitive was S. hemolyticus A. Heating to 100 degrees C for 30 and 60 minutes completely abolished the antimicrobial activity, while heating for 5 and 10 minutes, storage for 24 hours, and 4 hours of ultraviolet exposure decreased it. Garlic juice was bactericidal at concentrations of 5% and more. Thus garlic juice has marked antimicrobial activity that makes it a potential agent to be tested in clinical trials. The antimicrobial activity was compromised by storage and heating; therefore it is advisable to use fresh garlic and avoid boiling it for more than 5 minutes during cooking.

The bacteriocidal and bacteriostatic activities of normal bovine serum with and without extraneous complement on &lt;i&gt;Exchericha coli&lt;/i&gt;

The bacteriocidal and bacteriostatic activities of normal bovine serum with and without extraneous complement on &lt;i&gt;Exchericha coli&lt;/i&gt;

Inhibitory effect of Chardonnay and black raspberry seed extracts on lipid oxidation in fish oil and their radical scavenging and antimicrobial properties

Ethanol extracts of Chardonnay grape and black raspberry seed flours were evaluated for their capacity to suppress lipid oxidation, preserve important fatty acids, and inhibit microbial growth. They were also tested for radical scavenging activity against DPPH and peroxyl radicals as reflected in oxygen radical absorbance capacity (ORAC), and total phenolic content (TPC). Both tested seed flour extracts suppressed lipid oxidation and rancidity development in fish oil. Black raspberry seed flour extract significantly reduced the degradation of biologically important n − 3 PUFA under accelerated oxidative conditions. Black raspberry and Chardonnay seed flour extracts at 165 and 160 μg seed flour equivalents/mL, respectively exhibited bacteriocidal activity against Escherichia coli and growth inhibition of Listeria monocytogenes under experimental conditions. Both seed flour extracts exhibited DPPH radical quenching activity and Chardonnay had the stronger ORAC of 663 μmol Trolox equivalents per gram seed flour and the higher TPC of 99 mg gallic acid equivalents/g flour. The data from this study suggest the potential for developing natural food preservatives from these seed flours for improving food stability, quality, safety, and consumer acceptance.

N-thiolated β-lactams: Studies on the mode of action and identification of a primary cellular target in Staphylococcus aureus

This study focuses on the mechanism of action of N-alkylthio β-lactams, a new family of antibacterial compounds that show promising activity against Staphylococcus and Bacillus microbes. Previous investigations have determined that these compounds are highly selective towards these bacteria, and possess completely unprecedented structure–activity profiles for a β-lactam antibiotic. Unlike penicillin, which inhibits cell wall crosslinking proteins and affords a broad spectrum of bacteriocidal activity, these N-thiolated lactams are bacteriostatic in their behavior and act through a different mechanistic mode. Our current findings indicate that the compounds react rapidly within the bacterial cell with coenzyme A (CoA) through in vivo transfer of the N-thio group to produce an alkyl-CoA mixed disulfide species, which then interferes with fatty acid biosynthesis. Our studies on coenzyme A disulfide reductase show that the CoA thiol-redox buffer is not perturbed by these compounds; however, the lactams appear to act as prodrugs. The experimental evidence that these β-lactams inhibit fatty acid biosynthesis in bacteria, and the elucidation of coenzyme A as a primary cellular target, offers opportunities for the discovery of other small organic compounds that can be developed as therapeutics for MRSA and anthrax infections.

Enhanced Bacteriocidal Function by WKYMVm in Patients with Acute Leukemia.

Acute leukemia (AL) is a disease of challenge in that many patients die not only from eventual relapse but also from infection during treatment. In this regard efforts for decreasing infectious mortality will help increasing survival. Our previous study revealed that leukocyte bacteriocidal functions in chemotherapy-treated cancer patients were decreased and were stimulated by a novel hexapeptide, WKYMVm. We evaluated the leukocyte bacteriocidal function in patients with AL and searched whether WKYMVm can enhance the bacteriocidal function in patients with AL. On induction chemotherapy, blood sampling was performed at diagnosis and repeated weekly from start day of chemotherapy until patient died or complete remission was achieved. Tests were done weekly until white blood cell (WBC) count reached up to 1000/mm3 and platelet counts were stable without transfusion after consolidation chemotherapy. Nineteen AL patients and 10 healthy controls were enrolled. Diseases were acute myeloid leukemia (17 patients) and acute lymphoblastic leukemia (2 patients). Median WBC, absolute blast count (ABC) and absolute neutrophil count (ANC) at diagnosis were 5280/mm3 (range 840–315100), 162.9/mm3 (range 0–286741) and 796.4/mm3 (range 126–7336), respectively. Mean values of bacreriocidal activity at diagnosis were increased by concentrations of WKYMVm (13.4 at 0 nM; 24.9 at 1 nM; 33.3 at 10 nM; 38.5 at 100 nM; p<0.001), which were also increased in normal samples (20.6 at 0 nM; 41.6 at 1 nM; 51.6 at 10 nM; 66.4 at 100 nM; p<0.001). At each concentrations of WKYMVm, the bacteriocidal activities were inferior to those of normal control (p=0.029, at 0 nM; p=0.015, at 1 nM; p=0.015, at 10 nM; p=0.015, at 100 nM). The bacteriocidal activities were increased (p=0.008, at 0 nM; p=0.015, at 1 nM; p=0.011, at 10 nM; p=0.021, at 100 nM) compared with the corresponding values when patients achieved complete remission (CR). However, bactericidal activities by stimulation of WKYMVm were inferior to normal control even in CR (p=0.036, at 1 nM; p=0.036, at 10 nM; p=0.036, at 100 nM) although base line value were similar (p=1.0, at 0 nM). After hematological recovery of consolidation chemotherapy, the bacteriocidal activities of patients were similar to those of normal control (p=0.533, at 0 nM; p=0.133, at 1 nM; p=0.133, at 10 nM; p=0.133, at 100 nM). In conclusion, the bacteriocidal activities in AL patients were severely decreased at diagnosis and could be enhanced by WKYMVm. Near normal bacteriocidal activities can be achieved when 1 nM or more concentration of WKYMVm is applied in patients with AL. At the end of consolidation, bacteriocidal activities and stimulation by WKYMVm in patients were almost recovered.

Helicobacter pylori therapy: what is coming?

Helicobacter pylori infection is a widespread disease causing significant morbidity and mortality, with a relevant economic impact. To cure such an infection, the use of a 7-day triple therapy (a proton pump inhibitor together with two antibiotics) is suggested in those areas in which clarithromycin resistance rate is < 20%, whereas a 7-day quadruple therapy or a 14-day triple therapy should be used where clarithromycin resistance is higher. However, no existing therapies achieve bacterial eradication in all treated patients, the eradication rate can actually reach values as low as 70 – 80%. Therefore, new drugs are vital within this field. Surprisingly, very few patents have been claimed in the last three years. Quinolone derivatives probably remain the most investigated drugs, gemifloxacin being proposed most recently. New pleuromutilin derivatives (I-valnemulin) showed a very powerful bacteriocidal activity against H. pylori isolates, but in vivo data are still lacking. A novel proton pump inhibitor – the (-)-enantiomer of tenatoprazole – with reduced nocturnal acid breakthrough values has been claimed. This compound might improve activity of the antibiotic dose administered at bedtime.

Antimicrobial activity of lysostaphin and a Listeria monocytogenes bacteriophage endolysin produced and secreted by lactic acid bacteria

The expression and secretion signals of the Sep protein from Lactobacillus fermentum BR11 were used to direct export of two peptidoglycan hydrolases by Lb. fermentum BR11, Lactobacillus rhamnosus GG, Lactobacillus plantarum ATCC 14917 and Lactococcus lactis MG1363. The production levels, hydrolytic and bacteriocidal activities of the Listeria monocytogenes bacteriophage N-acetylmuramoyl- l-alanine amidase endolysin Ply511 and the glycylglycine endopeptidase lysostaphin were examined. Buffering of the growth media to a neutral pH allowed detection of Ply511 and lysostaphin peptidoglycan hydrolytic activity from all lactic acid bacteria. It was found that purified Ply511 has a pH activity range similar to that of lysostaphin with both enzymes functioning optimally under alkaline conditions. Supernatants from lactobacilli expressing lysostaphin reduced viability of methicillin resistant Staphylococcus aureus (MRSA) by ∼8 log 10 CFU/ml compared to controls. However, supernatants containing Ply511 were unable to control L. monocytogenes growth. In coculture experiments, both Lb. plantarum and Lb. fermentum synthesizing lysostaphin were able to effectively reduce MRSA cell numbers by >7.4 and 1.7 log 10CFU/ml, respectively, while lactic acid bacteria secreting Ply511 were unable to significantly inhibit the growth of L. monocytogenes. Our results demonstrate that lysostaphin and Ply511 can be expressed in an active form from different lactic acid bacteria and lysostaphin showed superior killing activity. Lactobacilli producing lysostaphin may have potential for in situ biopreservation in foodstuffs or for prevention of S. aureus infections.

Functional Characterization of Neutrophils from Nine-Banded Armadillos (Dasypus novemcicntus; Edentata, Dasypodidae) Infected with Microfilariae

The neutrophils from uninfected armadillos have adequate phagocytic and bacteriocidal activity, but diminished chemotactic activity. However, endocytic activity from armadillo neutrophils infected with bacteria, parasites or viruses is unknown. This report shows that neutrophils from armadillos infected with microfilariae displayed deficiencies in their bacteriocidal mechanisms and TNF-like production, but not in their endocytic capacity.