Negative Pathogenic Bacteria Research Articles

Antifungal activity of rice straw extract on some phytopathogenic fungi

Escherichia coli BL21(DE3) was transformed with a pHCD1 plasmid harboring the human β-defensin-1 ( hBD1 ) gene fused in frame behind a disulfide bond isomerase (DsbC), a His-tag, and an enterokinase cleavage site. After induction, the DsbC-hBD1 was expressed as a ~36 kDa soluble fusion protein in recombinant E. coli, which also inhibited host cell growth. After cell disruption, the soluble protein was easily recovered by Ni 2+ affinity chromatography and cleaved by enterokinase to yield a mature hBD1 of about 4 kDa. Importantly, the mature hBD1 showed broad antimicrobial activity against Gram-positive and -negative pathogenic bacteria, including Streptococcus pneumoniae , E. coli O157:H7, and Klebsiella pneumoniae. Key words : Antimicrobial activity, Escherichia coli , human β-defensin-1, soluble expression.

Detection of pathogenic gram negative bacteria using infrared thermography

Detection of viable bacteria is of prime importance in all fields of microbiology and biotechnology. Conventional methods of enumerating bacteria are often time consuming and labor-intensive. All living organisms generate heat due to metabolic activities and hence, measurement of heat energy is a viable tool for detection and quantification of bacteria. In this article, we employ a non-contact and real time method – infrared thermography (IRT) for measurement of temperature variations in four clinically significant gram negative pathogenic bacteria, viz. Vibrio cholerae, Vibrio mimicus, Proteus mirabilis and Pseudomonas aeruginosa. We observe that, the energy content, defined as the ratio of heat generated by bacterial metabolic activities to the heat lost from the liquid medium to the surrounding, vary linearly with the bacterial concentration in all the four pathogenic bacteria. The amount of energy content observed in different species is attributed to their metabolisms and morphologies that affect the convection velocity and hence heat transport in the medium.

Evaluation on Antibacterial Activity of <i>Lactobacillus acidophilus</i> Strains Isolated from Honey

Problem statement: This study reports the isolation of lactic acid bacteria from 13 honey samples produced in Malaysia, Libya and Saudi Arabia and their antibacterial activity against three Gram negative pathogenic bacteria. Approach: A modified MRS agar with 0.8% CaCO3 and MRS with 1% glucose was found to facilitate isolation of LAB compared to MRS, tomato juice agar and modified tomato juice agar. 32 isolates were confirmed LAB by catalase test and Gram staining. Six isolates were screened for antibacterial activity and identified as strains of Lactobacillus acidophilus 1 by API CH50. Results: All the isolates showed very good inhibitory activity against target Gram negative bacteria as indicated by the diameter of inhibition zone: Salmonella Typhimurium (23-30 mm), Escherichia coli (7-18 mm) and Enterobacter aerogenes (10-18 mm) after 24 h incubation at 30°C. Supernatants of L. acidophilus 1 strains showed good antibacterial activity against all target bacteria. Heating the supernatants at 90 and 121°C for 1 h enhanced the antibacterial activity against all target bacteria except supernatants H006-A and H010-G against S. Typhimurium. Antibacterial activity of supernatants were maintained after pH adjustment to 3, but at pH5 supernatants H006-A, H008-D and H010-G lost the activity against S. Typhimurium and E. coli within 48 h of incubation while at pH 6 all supernatants lost activity except against E. aerogenes. Enzymes treatments of supernatants with RNase II and Proteinase K for 1 h inhibited all target bacteria except supernatants H008-D, H008-E and H006-A which were relatively sensitive to both enzymes against S. Typhimurium and E. coli. Conclusion/Recommendations: In conclusion, honey from different sources contains strains of L. acidophilus 1 that produced compounds with good antibacterial activity which may be responsible for the antibacterial properties of honey.

Synthesis and Antimicrobial Screening of Three Triazole Derivatives

Due to the medicinal importance of triazole derivatives, the antimicrobial property of three synthesized triazole derivatives were screened in vitro against some Gram positive and Gram negative pathogenic bacteria and some pathogenic fungi. In this study, three compounds 2-(5-mercapto-4-phenyl-4H-[1,2,4] triazole-3-yl]-cyclohexa- 1,5-dienol (S1), 2-[5-mercapto-4-(2-mercapto-phenyl)-4H- [1,2,4] triazole-3-yl]-phenol (S2) and 4-[3-(2-hydroxyphenyl)- 5-mercapto-[1,2,4] triazole-4-yl]-benzene sulfonamide (S3) have been synthesized. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were assessed by serial dilution technique. The compounds showed moderate antimicrobial activity against all the tested organisms and the results are comparable to standard antibiotic kanamycin. The MIC values of the compounds were found to be in the range of 16~64μg/ml. The low MIC and MBC values and high sensitivity of pathogenic microorganisms to the compounds led to conclude that the triazole derivatives have potential antimicrobial properties. DOI: http://dx.doi.org/10.3329/dujps.v10i1.10014 DUJPS 2011; 10(1): 43-47

Antibacterial activity of Phoenix dactylifera L. leaf and pit extracts against selected Gram negative and Gram positive pathogenic bacteria

The crude methanol, acetone and water extracts of leaves and pits of three varieties ofPhoenix dactylifera were tested for antibacterial action against selected Gram positive and Gram negative pathogenic bacteria. Barring Enterococcus faecalis, the acetone and methanol extracts showed good antibacterial activity against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Shigella flexeneri, Staphylococcus aureus, and Streptococcus pyogenes, whereas the water extract had very little effect on all test bacterial species and there was almost negligible effect on P. aeruginosa. Pits extracts of all three varieties of P. dactylifera were found to be more effective than leaves extracts. Results clearly showed that S.pyogenes was most sensitive pathogen to the crude extracts and had shown maximum zone of inhibition. Minimum inhibitory concentration (MIC) for S. pyogenes was found to be 1.3, 1.1, 1.6 and 1.4 mg/ml for methanol leaves and pits extracts and acetone leaves and pits extracts, respectively. Key words: Date palm, Phoenix dactylifera L, antibacterial, crude extracts.

Organic Acids as Feed Additive in Pig and Poultry Diets: A Review

A review was carried on the potentials of organic acids as feed additive in the diets of poultry and pigs. Organic acids (as acetic, butyric, citric, formic and propionic acids) or their salts (calcium formate and sodium butyrate) are weak carboxylic acids that occur naturally in fruits but could be synthesized and manufactured in commercial quantity. They exhibit certain properties which could make them unique as growth promoters in monogastric animals. Organic acids are antimicrobial in action reducing bacteria and fungi both in the feed and in the gastro intestinal tract. Their ability to reduce gram negative pathogenic bacteria in the gut reduces fermentation in the gut thereby improving digestibility, nutrient absorption and utilization. Other areas organic acids could enhance animal productivity is their ability to induce endogenous secretions such as gastric hydrochloric acid, enzymes, bile and mucus. They also function to increase the number and height of the villi and reduce both the crypt depth and digesta viscosity. High level in the feed could reduce feed intake and growth. They could be corrosive to feed mixers, feed bins, silos, feeding and could also pose health problems to farm and feed mill attendants. Keywords : feed additive, pig, poultry, and organic acids.

Pharmacological and Phytochemical Screening of Ethanol Extract of Litsea monopetala (Roxb.) Pers.

Present study was conducted by the ethanol extract of leaves of Litsea monopetala. Preliminary phytochemical screening with the crude extract demonstrated the presence of alkaloids, tannins, steroids, flavonoids and reducing sugars. In-vitro antimicrobial sensitivity was evaluated against 4 Gram positive and 7 Gram negative pathogenic bacteria and 7 fungi using ciprofloxacin and fluconazole respectively as standards. In disc diffusion antimicrobial assay, L. monopetala showed varying degrees of antimicrobial activities with zone of inhibition ranging from 10-12 mm and 12-14 mm for test bacteria and fungi respectively where the growth of Pityrosporum ovale and Cryptococcus neoformans were strongly inhibited. In the minimum inhibitory concentration (MIC) test by serial dilution method, a mild to strong MICs were observed for the test microorganisms. During the in-vitro clot lysis test, the crude extract exhibited percent lysis of clot significantly by 18.84% compared to the standard, SK (81.53%). Moreover, the extract produced inhibition of protein denaturation and haemolysis by 40% and 42.44% in the in-vitro anti-inflammatory and membrane stabilization test.

In vitro antibacterial and antifungal activities of Cassia fistula Linn. fruit pulp extracts

Aim of the study is to assess the antimicrobial activity Cassia fistula fruit pulp extracts on some bacterial and fungal strains. Hydro alcohol and chloroform extracts of Cassia fistula fruit pulp were evaluated for the potential antimicrobial activity. The antimicrobial activity was determined in both the extracts using the agar disc diffusion method. Extracts were effective on tested microorganisms. The antibacterial and antifungal activities of solvent extracts (5, 25, 50, 100, 250 μg/mL) of C. fistula were tested against two gram positive, two gram negative human pathogenic bacteria and three fungi, respectively. Crude extracts of C. fistula exhibited moderate to strong activity against most of the bacteria tested. The tested bacterial strains were Staphylococcus aureus, Streptococcus pyogenes, Escherichia coil, Pseudomonas aeruginosa, and fungal strains were Aspergillus. niger, Aspergillus. clavatus, Candida albicans. The antibacterial potential of the extracts were found to be dose dependent. The antibacterial activities of the C. fistula were due to the presence of various secondary metabolites. Hence, these plants can be used to discover bioactive natural products that may serve as leads in the development of new pharmaceuticals research activities.

ANTIMICROBIAL POTENCY OF FIVE SOUTH INDIAN FERNS AGAINST XANTHOMONAS CAMPESTRIS

ABSTRACT The objective of the present study is to evaluate the antimicrobial potency of five solvents (petroleum ether, benzene, chloroform, methanol and water) extracts of five medicinal ferns Pteris biaurita L., Lygodium flexiuosam (L.) Sw., Hemionitis arifolia (Burm.F.) T. Moore, Actinopteris radiata (J. Koenig ex Sw.) Link and Adiantum latifolium Lam. against the gram negative plant pathogenic bacteria Xanthomonas campestris. Antimicrobial activity, Minimum Inhibitory Concentration (MIC) and Relative Percentage Inhibition (RPI) value of the extracts against X. campestris were screened according to the standard procedures. Among the twenty five tested extracts, methanol and benzene extracts of P. biaurita showed significant inhibition (p<0.05) against the tested bacteria. Based on the results of MIC (8µg/mL) and RPI (199.36%) values, it could be concluded that P. biaurita can be used as potential plant for the management of X. campestris which is known to cause leaf spot disease on many vegetables and cash crops particularly Centella asiatica.

Screening of antimicrobial potential of polysaccharide from cuttlebone and methanolic extract from body tissue of Sepia prashadi Winkworth, 1936

Objective To evaluate the antimicrobial activity of polysaccharide from cuttlebone and methanolic extract from body tissue of Sepia prashadi, against ten human pathogenic bacteria and five fungi. Methods The activity of polysaccharide and methanolic extract was investigated against Vibrio cholerae, Pseudomonas aeruginosa, Klebsiella pneumoniae, Vibrio alginolyticus, Staphylococcus aureus, Vibrio parahaemolyticus, Streptococcus sp., Streptococcus pneumoniae, Salmonella sp. and Escherichia coli, and five fungal strains such as Alternaria alternata, Candida tropicalis, Penicillium italicum, Fusarium equiseti and Candida albican using disc diffusion method and minimum inhibitory concentration (MIC) were also calculated. Results Both polysaccharide and methanolic extract was active against gram positive than that of gram negative pathogenic bacteria but inactive against fungi. The MIC of both the extract ranging from 60 to 100 mg/mL. Conclusions These results suggest that cephalopod polysaccharide and methanolic extract possess relatively good antibacterial activity.

Antibacterial activities of some plant extracts used in Indian traditional folk medicine

Objective To evaluate the antibacterial activity of the leaf extracts of Cestrum diurnum , Ocimum sanctum , Carcica papaya, Solanum villosum , Vitex negundo , and Clerodendron inerme against two gram positive bacteria ( Staphylococcus aureus MTCC 2940 and Bacillus subtilis MTCC 441) and two gram negative bacteria ( Escherichia coli MTCC 739 and Pseudomonas aeruginosa MTCC 2453). Methods The sensitivity of two gram positive and two gram negative pathogenic multi-drug resistant bacteria to extracts of leaves of six medicinal plants used as popular medicine in India was studied in vitro by the disk diffusion method and minimal inhibitory concentration (MIC). Results All the bacterial strains were found to be sensitive to aqueous, n-hexane and ethanol extracts. But, it is evident that the organic extracts were comparatively more effective than aqueous extracts. Conclusions It can be concluded that the leaf extracts of the six medicinal plants possess antibacterial activity against human pathogens.

Bioactive compounds and biological activities of Jatropha curcas L. kernel meal extract.

Defatted Jatropha curcas L. (J. curcas) seed kernels contained a high percentage of crude protein (61.8%) and relatively little acid detergent fiber (4.8%) and neutral detergent fiber (9.7%). Spectrophotometric analysis of the methanolic extract showed the presence of phenolics, flavonoids and saponins with values of 3.9, 0.4 and 19.0 mg/g DM, respectively. High performance liquid chromatography (HPLC) analyses showed the presence of gallic acid and pyrogallol (phenolics), rutin and myricetin (flavonoids) and daidzein (isoflavonoid). The amount of phorbol esters in the methanolic extract estimated by HPLC was 3.0 ± 0.1 mg/g DM. Other metabolites detected by GC-MS include: 2-(hydroxymethyl)-2 nitro-1,3-propanediol, β-sitosterol, 2-furancarboxaldehyde, 5-(hydroxymethy) and acetic acid in the methanolic extract; 2-furancarboxaldehyde, 5-(hydroxymethy), acetic acid and furfural (2-furancarboxaldehyde) in the hot water extract. Methanolic and hot water extracts of kernel meal showed antimicrobial activity against both Gram positive and Gram negative pathogenic bacteria (inhibition range: 0–1.63 cm) at the concentrations of 1 and 1.5 mg/disc. Methanolic extract exhibited antioxidant activities that are higher than hot water extract and comparable to β-carotene. The extracts tended to scavenge the free radicals in the reduction of ferric ion (Fe3+) to ferrous ion (Fe2+). Cytotoxicity assay results indicated the potential of methanolic extract as a source of anticancer therapeutic agents toward breast cancer cells.

English

    Traditional medicine has a key role in health care worldwide. Obtaining scientific information about the efficacy and safety of the wild plants grown in western Mediterranean coast of Egypt is one of our research goals. In this study, 10 wild plants namely Mesembryanthemum crystallinum, Blackiella aellen, Arthrocnemon glaucum, Atriplex halimus, Thymelaea hirsute, Carduus getulus, Nicotiana glauca,Alhagi maurorum, Atractylis carduus and Echinops spinosissimus were collected from El-Hammam, Burg El Arab and Bahig regions located along the Western Mediterranean coast of Egypt. Hexane and methanol extracts of fresh aerial parts ofthe plants were screened in vitro for antimicrobial activity against 15 Gram positive and negative pathogenic bacteria. Both methanol and hexane plant extracts showed strong antibacterial activity against at least two pathogenic microorganisms tested. However, hexane extracts generally showed lower activity against microorganisms compared to methanol extracts. The microorganisms’ susceptibility to different extracts did not correlate with the susceptibility or resistance to a particular antibiotic. The results of this study thus support the medical usage of the studied plants and suggest that some of these plants possess antimicrobial properties that can be used to cure infectious diseases.     Key words: Egyptian wild plants, antagonism, biological control, phytochemicals, multi-drug resistant.

In vitro bioactivity and phytochemical screening of Suaeda maritima (Dumort): A mangrove associate from Bhitarkanika, India

Objective To investigate the in vitro antioxidant and antimicrobial activities along with phytochemical screening of organic and aqueous extracts of leaf and stem of Suaeda maritima (Dumort), a mangrove associate from Bhitarkanika of Odisha, India. Methods Antioxidant activity of the crude extracts was evaluated in terms of total antioxidant capacity, total phenol content, ascorbic acid content, DPPH radical scavenging, metal chelating, nitric oxide scavenging, and reducing power etc. The antimicrobial activity of the plant was determined by agar well diffusion method along with MIC and MBC carried out by microdilution techniques against 10 gram positive and gram negative human pathogenic bacteria. The qualitative and quantative phytochemical screening were carried out by standard biochemical assays. Results Out of the seven antioxidant bioassays, both the leaf and stem extracts were found to posses strong antioxidant properties of 70 % to 92 % for phenol, total antioxidant capacity, DPPH free radical scavenging activity and fairly good ascorbic acid content, metal chelating (1.33 %-22.55 %), reducing power (0.01-0.12) and nitric oxide scavenging (0.84 %-66.99 %) activities. Out of the four extracts evaluated for antimicrobial activity, two leaf extracts such as acetone and ethanol showed promising activity against four pathogenic bacteria and one stem methanol extracts against one pathogenic bacteria when compared with amoxcycillin as standard. The MIC and MBC values of the antimicrobial extracts ranged between 2.5 to 5.0 mg/mL. Screening of phytochemicals showed presence of carbohydrates, protein, tannins, alkaloids and flavonoids in comparatively higher amount than other phytochemicals tested. Conclusions The present study reveals the presence of potential antioxidants and antimicrobial properties in the plant extract which could be exploited for pharmaceutical application.

Evaluation of the inhibitory effect of a number of medicinal plants fixed oils on a group of pathogenic bacteria invitro

The present study was designed to evaluate the antibacterial effect of 4 of local medicinal plants oils :Eletteria cardaomum,Nigella sativa,Prunus dulcisvar and Brassica alba in addition to 5 Antibiotics: Ciprofloxacin ,Chloramphenicol, Aztereonam, Sulfamethaxazole /Trimethoprime and Erythromycine as a positive control against 7 gram positive and gram negative pathogenic bacteria:Micrococcus spp.,Staphylococcus cohnii cohnii ,Enterobacter cloacae,Escherichia coli, Proteus mirabilis,Pseudomonas aeroginosa and Klebsiella pneumonia by using of agar well diffusion method . The result showed that for the oil of Eletteria cardamomum the best antibacterial effect was produced against Proteus mirabilis followed by Klebsiella pneumonia then Enterobacter cloacae,Pseudomonas aeroginosa,Escherichia coli,Micrococcus spp. and Staphylococcus cohnii cohnii , and for the oil Nigella sativa the antibacterial effect was highest against Micrococcus spp., followed by Proteus mirabilis then Escherichia coli and Staphylococcus cohnii cohnii. Brassica alba oil express it is antibacterial effect only against Pseudomonas aeroginosa and there was no effect on any other bacteria while Brassica alba had no effect on any of the studied bacteria.The inhibition of the growth of Pseudomonas aeroginosa was stronger by Prunus dulcisvar oil than Eletteria cardamomum oil .For Escherichia coli,Staphylococcus cohnii cohnii and Micrococcus the wider zone of inhibition was obtained by Nigella sativa oil than Eletteria cardamomum oil, while for Proteus mirabilis the inhibition of the growth was higher for the oil of Eletteria cardamomum than Nigella sativa oil.The values were given as mean ±Standard deviation and P< 0.05 was considered statistically significant.The datad were analyzed by student's t-test using SPSS (version 10).

Antibacterial, cytotoxic and antioxidant activity of chloroform, n-hexane and ethyl acetate extract of plant Coccinia cordifolia

The main aim of this study was to find out the antibacterial, cytotoxic and antioxidant activity of chloroform, n-hexane and ethyl acetate extracts of Coccinia cordifolia (Family: Cucurbitaceae). Disc diffusion technique was used for in vitro antibacterial screening against gram positive and gram negative human pathogenic bacteria. Here kanamycin disc (30g/disc) was used as standard. The chloroform extract of Coccinia cordifolia showed good antibacterial activity with the average zone of inhibition 9-12mm. The n-hexane and ethyl acetate extract showed average zone of inhibition 7-10mm and 7-11mm respectively. The Brine shrimp lethality bioassay method was used to determine the cytotoxic activity and vincristine sulphate was used as positive control. The LC50 values of standard vincristine sulphate, chloroform, n-hexane and ethyl acetate extract were 7.55μg/ml, 23.96 μg/ml, 14.12 μg/ml & 15.49 μg/ml respectively which indicate the plants extracts compounds are promisingly cytotoxic and they might have antitumer and pesticidal activity. Among the extracts the chloroform extract showed the highest cytotoxic activity with LC50 23.96 μg/ml. Antioxidant activity test of the crude extracts were assessed by means of DPPH free radical scavenging method where ascorbic acid was used as standard with IC50 43.22 μg/ml. The ethyl acetate fraction of Coccinia cordifolia showed strongest antioxidant activity with IC50 value of 50.98 μg/ml.

The Effect of different crude methanolic extracts against some gram negative pathogenic bacteria

This present study was conducted to evaluated the antibacterial activity of crude extracts (Methanolic) of punica granatum peel, Menthe longifolia and Olea eurpeae leaves against some gram negative bacteria like Pseudomonas aerugenosa, Serratia marcesens, Escherichia coli, Proteus vulgaris, Klebsiella pnemunoniae. The Agar-well diffusion was used to know the ability of inhibititory of crude extracts against bacteria. Results showed different susceptibility response of bacteria under study. It was observed that Pseudomonas aerugenosa the most susceptible to Methanolic extracts to all plants in (25, 50) mg/ml-1 concentrate. While the bacterial strains shown no responding against mint and pomegranate extracts in 10 mg/ml-1 except Pseudomonas aerugenosa and Escherichia coli, was inhibited with Olive extracts only. That ability to inhabitation less in concentrate 10 mg ml-1.

Modeling inactivation kinetics and occurrence of sublethal injury of a pulsed electric field-resistant strain of Escherichia coli and Salmonella Typhimurium in media of different pH

A study of the effect of pulsed electric fields (PEF) on the kinetics of inactivation and the occurrence of cell damage in Escherichia coli O157:H7 and Salmonella Typhimurium 878 treated in McIlvaine buffer covering a range from pH 3.5 to 7.0 was conducted. Mathematical equations based on the Weibull distribution were developed to describe the influence of the electric field strength, treatment time and pH of the treatment medium on the lethality and generation of cell damage of both Gram negative pathogenic bacteria after the application of PEF treatments. E. coli O157:H7 was more PEF resistant than Salmonella Typhimurium at all pH investigated. PEF resistance of E. coli was influenced by the pH but the pH hardly affected the PEF resistance of Salmonella Typhimurium 878. After 150 μs at 35 kV/cm, 1 and 5 log10 cycles of inactivation of E. coli O157:H7 were observed in the range of pH 3.5–4.5 and 5.5–6.5, respectively. Cell damage increased with the field strength and treatment time. A maximum cell damage level of 4.2 and 2.7 log10 cycles for E. coli O157:H7 and Salmonella Typhimurium was observed respectively after a treatment of 30 kV/cm at pH 3.5. PEF induced cell damage was not detected at pH higher than 5.0 for both microorganisms. The developed equations can be applied to design combining processes which can increase the lethality of PEF or to reduce the intensity of PEF treatments to achieve a determine level of microbial inactivation. This study demonstrates that when the influence of several factors on the microbial behavior is investigated, the development of mathematical models is a very useful tool to evaluate the influence of each parameter and their interactions. In this study, it has been mathematically described for first time the influence of the pH of the treatment medium and the occurrence of sublethal injury in a wide range of electric field strengths and treatment times in two Gram negative pathogenic bacteria, Escherichia coli O157:H7 and Salmonella Typhimurium 878. These models would also be of interest for engineering design, evaluation and optimization of PEF process as a new technique for food preservation.

Antimicrobial and Cytotoxic Activity of the Alkaloids of Amlaki (Emblica officinalis)

Alkaloids are important sources of drug that's why we have conducted our research to find out the biological activity of the alkaloids of a plant that is the Amlaki. Alkaloids were extracted from the methanolic extract of the fresh ripe fruits of Amlaki (Emblica officinalis) through solvent-solvent partitioning method with n-hexane and chloroform. The chloroform soluble fraction of the crude methanolic extract of the ripe fruits of Amlaki containing alkaloids was subjected to antimicrobial activity and brine shrimp lethality bioassay for observing cytotoxic activity. The chloroform soluble fraction of the methanolic extract exhibited significant antimicrobial activity against some Gram positive and Gram negative pathogenic bacteria and strong cytotoxicity having a LC50 of 10.257 +/- 0.770 microg mL(-1). It is concluded that the chloroform soluble fraction of the ripe fruits of Amlaki containing alkaloids are biologically active.

Functional properties of novel protective lactic acid bacteria and application in raw chicken meat against Listeria monocytogenes and Salmonella enteritidis

In this study 635 lactic acid bacteria of food origin were evaluated for their potential application as protective cultures in foods. A stepwise selection method was used to obtain the most appropriate strains for application as protective cultures in chicken meat. Specifically, all strains were examined for antimicrobial activity against various Gram positive and Gram negative pathogenic and spoilage bacteria. Strains exhibiting anti-bacterial activity were subsequently examined for survival in simulated food processing and gastrointestinal tract conditions, such as high temperatures, low pH, starvation and the presence of NaCl and bile salts. Selected strains where then examined for basic safety properties such as antibiotic resistance and haemolytic potential, while their antimicrobial activity was further investigated by PCR screening for possession of known bacteriocin genes. Two chosen strains were then applied on raw chicken meat to evaluate their protective ability against two common food pathogens, Listeria monocytogenes and Salmonella enteritidis, but also to identify potential spoilage effects by the application of the protective cultures on the food matrix. Antimicrobial activity in vitro was evident against Gram positive indicators, mainly Listeria and Brochothrix spp., while no antibacterial activity was obtained against any of the Gram negative bacteria tested. The antimicrobial activity was of a proteinaceous nature while strains with anti-listerial activity were found to possess one or more bacteriocin genes, mainly enterocins. Strains generally exhibited sensitivity to pH 2.0, but good survival at 45 °C, in the presence of bile salts and NaCl as well as during starvation, while variable survival rates were obtained at 55 °C. None of the strains was found to be haemolytic while variable antibiotic resistance profiles were obtained. Finally, when the selected strains Enterococcus faecium PCD71 and Lactobacillus fermentum ACA-DC179 were applied as protective cultures in chicken meat against L. monocytogenes and S. enteritidis respectively, a significantly reduced growth of these pathogenic bacteria was observed. In addition, these two strains did not appear to have any detrimental effect on biochemical parameters related to spoilage of the chicken meat.