An evaluation and partial characterization of a bacteriocin produced by Lactococcus lactis subsp lactis ST1 isolated from goat milk

A bacteriocin-like inhibitory substance producing Lactococcus lactis subsp lactis strain, ST1, isolated from goat milk of Iranian origin and with broad spectrum of activity and desirable technical properties was used for evaluating some futures of bacteriocin inhibitory activity. Cell growth and bacteriocin production studies were carried out in MRS medium incubated statically under uncontrolled pH condition. The antibacterial activity presented a primary metabolite pattern and showed a rapid decrease at the stationary phase. Microaerobiosis and capnophily growth conditions resulted in higher bacteriocin production while aerobiosis showed negative effect on both cell growth and bacteriocin production. Bacteriocin production, on the other hand, was favored in MRS broth (pH; 6.5) inoculated with 0.1 ml l-1 fresh culture when incubation was carried out at 30 °C. This indicated that the conditions resulted in higher levels of growth were frequently favoring bacteriocin production by ST1 as well. Decrease in activity, at the stationary growth phase, was much pronounced in favored growth condition. Nutrient depletion, deferent effect of low pH on bacteriocin production and/or protein degradation seemed more responsible for this phenomenon. The study also provided further data on new method for bacteriocin release from the cell wall of producer. It was clearly shown that both heating and ultrasound shock for 5 min at pH 2 could increase bacteriocin activity significantly. The release was more pronounced in the presence of 0.5% Tween80.

Detección y caracterización de Betalactamasa de espectro extendido en enterobacterias / Detection and characterization of extended-spectrum beta-lactamases in Enterobacteriaceae

El incremento y la diseminación de la resistencia antimicrobiana en baterias que son patógenas para el hombre se ha constituido en un importante problema de Salud Pública cualquier uso de drogas antimicrobianas en humanos, plantas o animales pueden conducir a las resistencia bacteriana. El género enterobacterias es uno de los grupos bacterianos que más ha sido sometido a la presión selección por el uso indiscriminado de drogas antimicrobianas y por la gran variedad de especies capaces de producir patología en el hombre. La particularidad del comportamiento de estos agentes, dependiendo del medio donde surge como patógenos ha llegado a numerosso grupos de trabajo a realizar estudios de monitoreos locales de resistencia. El principal mecanismo de aparición de la resistencia es la producción de enzimas inactivantes de las betalactamasas de espectro extendido (BLEE)...

Horizontol dissemination of TEM- and SHV-typr beta-lactamase genes-carrying resistance plasmids amongst clonical isolates of Enterobacteriaceae / Disseminação horizontal de plasmídios de resistência contendo genes de beta-lactamase dos tipos TEM e SHV entre isolados clínicos de Enterobacteriaceae

The extended-spectrum â-lactamase (ESBL)-producing bacteria have been isolated at increasing frequency worldwide. Expression of ESBL is often associated with multidrug resistance and dissemination by resistance plasmids. During a two-month period in 2000, 133 clinical isolates of enterobacterial strains were randomly collected from outpatients and inpatients at a university hospital in Turkey. The ESBL producing strains were determined by double-disk synergy (DDS) testing. Twenty ESBL producing strains (15 percent) including Escherichia coli (n = 9), Klebsiella pneumoniae (n = 7), Klebsiella oxytoca (n = 2) and Enterobacter aerogenes (n = 2) were detected and further analyzed for their resistance transfer features, plasmid profile and nature of the resistance genes. Plasmid transfer assays were performed using broth mating techniques. TEM- and SHV- genes were analyzed by polymerase chain reaction (PCR) and hybridization using specific probes. EcoRI restriction enzyme analyses of R plasmids were used in the detection of epidemic plasmids. Fourteen plasmid profiles (A, B1, B2, C1, and C2 to L) were obtained with EcoRI restriction enzyme analysis. Most of these plasmids were detected to carry both TEM- and SHV-derived genes by PCR, and confirmed by localizing each gene by hybridization assay. Epidemiological evidence indicated that there was an apparent horizontal dissemination of conjugative R plasmids among multidrug-resistant enterobacterial genera and species in this hospital

O isolamento de bactérias produtoras de beta-lactamases de espectro expandido (ESBL) está aumentando no mundo todo. Freqüentemente, a expressão de ESBL está associada com resistência a múltiplas drogas e disseminação por plasmídios de resistência. Durante um período de dois meses em 2000, 133 isolados clínicos de cepas de enterobactérias foram obtidos aleatoriamente de pacientes internos e externos de um hospital universitário na Turquia. As cepas produtoras de ESBL foram identificadas pelo teste de sinergia em disco-duplo (DDS). Foram detectadas vinte cepas produtoras de ESBL, entre as quais Escherichia coli (n=9), Klebsiella pneumoniae (n=7), Klebsiella oxytoca (n=2) e Enterobacter aerogenes (n=2), que foram posteriormente analisadas quanto a suas características de transferência de resistência, perfil plasmidial e natureza dos genes de resistência. Os testes de transferência de plasmídios foram realizados empregando técnicas de conjugação em caldo. Os genes TEM e SHV foram analisados pela reação da polimerase em cadeia (PCR) e hibridização com sondas especificas. A detecção de plasmídios epidêmicos foi feita por análise dos plasmídios R com a enzima de restrição EcoRI. Através desta análise, foram obtidos catorze perfis plasmidiais (A, B1, B2, C1 e C2 até L).Observou-se pela PCR que a maioria dos plasmidios carregavam genes derivados de TEM e SHV, confirmados através da detecção dos genes pelos testes de hibridização. As evidencias epidemiológicas indicaram que havia uma aparente transferência horizontal dos plasmídios R conjugativos entre as enterobactérias multiresistentes neste hospital.

Molecular studies of E. coli mercuric reductase gene (merA) and its impact on human health.

Bacterial plasmids encode resistance systems for toxic metal ions including Hg2+ functioning by energy-dependent efflux of toxic ions. The inducible mercury resistance (mer) operon encodes both a mercuric ion uptake and a detoxification enzymes. In Gram-negative bacteria especially in E. coli, a periplasmic protein, MerP, an inner- membrane transport protein, MerT, and a cytoplasmic enzyme, mercuric reductase (the MerA protein), are responsible for the transport of mercuric ions into cell and their reduction to elemental mercury, Hg0. Phytoremediation involves the use of plants to extract, detoxify and/or sequester environmental pollutants from soil and water. Transgenic plants cleave mercury ions from methyl-mercury complexes; reduce mercury ions to the metallic form; take up metallic mercury through their roots; and evolve less toxic elemental mercury. PCR were performed to detect 1695 bp of mercuric reductase gene (merA), which is mainly responsible for the conversion of mercuric (Hg+2) and mercurous (Hg+1) ions into non-toxic elemental mercury. PCR products of putative merA genes from environmental E. coli strains were purified and cloned into a plant expression vector pRT100. The construct will be transformed in calli of Nicotiana plants.

Efecto de la adición de nisina en los parámetros físicos, químicos y sensoriales del queso telita / Effect of the addition of nisin on the physical, chemical and sensory parameters of telita cheese

El uso de la nisina, una bacteriocina natural, es una alternativa para disminuir los riesgos de la elaboración de queso con leche cruda, aumentarle la vida útil del producto y en consecuencia mejorar su comercialización. En este estudio se evaluó el efecto de dos concentraciones de nisina (10 y 16,7 mg/kg queso), en las características físicas, químicas y en la calidad sensorial del queso "telita" elaborado con 3 partidas de leche fresca de diferente procedencia. El queso "telita" sin la adición de nisina se usó como control. Se prepararon 3 lotes de quesos. A la leche cruda se le determinó densidad, pH, acidez, proteínas, grasa, cenizas, fósforo y calcio. Se le determinó humedad, proteínas, grasas, aw, pH y calidad sensorial a 24h de elaborados los quesos. Se observaron variaciones significativas en la composición de las tres partidas de leche utilizadas. La composición promedio de los quesos analizados fue: humedad 64 por ciento, proteínas 16 por ciento, grasas 17 por ciento, aw 0,98 y pH 5,7. La calidad sensorial del queso con nisina no varió significativamente con respecto al queso control. Los resultados indican que la adición de nisina en las concentraciones ensayadas no afectó la composición química y la calidad sensorial del queso telita.

Immunization of rats with a targeted fusion anticaries DNA vaccine / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To observe the expression of a targeted fusion anticaries DNA vaccine pGJA-P in situ. To compare the levels of specific antibodies and anticaries efficacy generated by pGJA-P and pGLUA-P, a fusion anticaries DNA vaccine.</p><p><b>METHODS</b>pGJA-P was administrated intramuscularly or intranasally to rats, and the expression of recombinant protein was detected by immunohistochemistry technique. Wistar rats were fed a cariogenic diet and orally infected with S. mutans, then immunized with pGJA-P or pGLUA-P via the intramuscular or intranasal route. All rats received a booster immunization 2 weeks later. At the termination of the experiment, blood and saliva samples were collected for assay of antibodies by ELISA and jaws were obtained for caries evaluation by the Keyes method.</p><p><b>RESULTS</b>Recombinant protein could be detected in muscle in intramuscularly immunized rats and in nasal mucosa in intranasally immunized rats. Rats immunized intramuscularly with pGJA-P had significantly higher serum IgG levels than others (P < 0.01). Rats immunized intranasally or intramuscularly with pGJA-P had significantly higher salivary IgA levels than others (P < 0.01). Keyes scores of pGJA-P groups were significantly lower than those of pGLUA-P groups and pCI groups (P < 0.01).</p><p><b>CONCLUSIONS</b>pGJA-P could be correctly expressed in vivo. pGJA-P generated increased humoral immune response and anticaries efficacy compared with pGLUA-P.</p>

Factores de virulencia de Escherichia coli aviar asociados a la colisepticemia en pollos de engorde / Avian Escherichia coli virulence factors associated with coli septicemia in broiler chickens

In order to detect phenotypic characteristics associated with pathogenicity, 25 strains of Escherichia coli, isolated from clinical cases of colisepticemia in broiler chickens, were examined to determine the following properties: colicinogenicity, colicin V production, type 1 fimbriae, hemolysin expression and motility. Colicinogenicity occurred in 72 of the strains, 56 of all strains produced colicin V, 84 were positive for type 1 fimbriae and 80 were positive for motility. None of the strains had hemolytic activity; however, all of them, expressed at least one of the other characteristics studied. These results suggest that the diversity of phenotypes detected partially explain the multifactorial nature of avian colisepticemia.

Antilisterial activity of lactic acid bacteria isolated from vacuum-packaged brazilian meat and meat products

Twenty samples of Brazilian meat and meat products were screened by the agar overlay method for bacteriocin-producing lactic acid bacteria, using Lactobacillus sake ATCC 15521 as indicator strain. Based on Gram staining, KOH reaction, catalase test and fermentation of 49 carbohydrates (API 50 CH), three out of seven isolates with confirmed antagonist properties were identified as Lactobacillus curvatus, one as Leuconostoc mesenteroides and one as Leuconostoc sp. Two isolates could not be properly identified using these tests. The inhibitors produced by these strains were sensitive to proteases. Inhibition due to lytic bacteriophages was ruled out, so the isolates were classified as bacteriocin-producing lactic acid bacteria. Four of them presented antilisterial activity and a potential application as biopreservatives in meat systems.

Bacteriocins of indigenous clinical staphylococci: screening and charcterization

Staphylococcin [a class of bacteriocin] production was studied in 250 clinical isolates of staphylococci. 7% of the isolates exhibited intra - isolate and broad - range antagonistic activity. Crude bacteriocin preparations were not inactivated after prolonged thermal exposure [80°C] and were stable in the pH range of 5.4 - 10. The preparations also resisted the action of trypsin [a proteolytic enzyme], lysozyme [a glycolytic enzyme] and lipase [a lipolytic enzyme]. However, one of the extracts [Staphylococcin AB201] was sensitive to heat and trypsin. All the preparations retained their bioactivity after prolonged [16 weeks] refrigeration and freezing. Attempts to induce bacteriocin production [with UV, 0.5% mannitol and 2% yeast extract] and to elute cell bound bacteriocin [with 0.1M, 1M and 5M NaCl and 0.05M EDTA] were unsuccessful. The bacteriocinogenic determinants in the staphylococcal isolates were cured by heating [44°C] and ethidium bromide [300 micro g/mL], suggestive of their plasmid- borne location

Colicinogeny in Salmonella serovars isolated in Brazil

Investigou-se a produçäo de colicina em 748 amostras de Salmonella (97 sorovares) advindas de díferentes fontes: humana (291), animal (119), ambiental (141), de alimentos (102) e raçöes (95). Detectaram-se 64 amostras (8,6%) colicinogênicas, particularmente isoladas de alimentos (30,4%). ColE1 (53) e Ia (44) foram as mais freqüentes, especialmente no sorovar S, agona, de origem ambiental e de alimentos. Identificou-se também a produçäo de col V em 5 amostras de S. typhimurium dentre 8 culturas produtoras de origem humana. Discute-se a relaçäo entre a capacidade colicinogênica e as fontes e sorovares de Salmonella