RESUMEN
The aim of this work was to study the efficiency of diverse chemical and thermal treatments usually used in dairy industries to control the number of virulent and temperate Lactobacillus delbrueckii bacteriophages. Two temperate (Cb1/204 and Cb1/342) and three virulent (BYM, YAB and Ib3) phages were studied. The thermal treatments applied were: 63 degrees C for 30 min (low temperature--long time, LTLT), 72 degrees C for 15 s (high temperature--short time, HTST), 82 degrees C for 5 min (milk destined to yogurt elaboration) and 90 degrees C for 15 min (FIL-IDF). The chemical agents studied were: sodium hypochlorite, ethanol, isopropanol, peracetic acid, biocides A (quaternary ammonium chloride), B (hydrogen peroxide, peracetic acid and peroctanoic acid), C (alkaline chloride foam), D (p-toluensulfonchloroamide, sodium salt) and E (ethoxylated nonylphenol and phosphoric acid). The kinetics of inactivation were drew and T(99) (time necessary to eliminate the 99% of phage particles) calculated. Results obtained showed that temperate phages revealed lower resistance than the virulent ones to the treatment temperatures. Biocides A, C, E and peracetic acid showed a notable efficiency to inactivate high concentrations of temperate and virulent L. delbrueckii phages. Biocide B evidenced, in general, a good capacity to eliminate the phage particles. Particularly for this biocide virulent phage Ib3 showed the highest resistance in comparison to the rest of temperate and virulent ones. On the contrary, biocide D and isopropanol presented a very low capacity to inactivate all phages studied. The efficiency of ethanol and hypochlorite was variable depending to the phages considered. These results allow a better knowledge and give useful information to outline more effective treatments to reduce the phage infections in dairy plants.
Asunto(s)
Fagos de Bacillus/fisiología , Productos Lácteos/microbiología , Desinfectantes/farmacología , Calor , Lactobacillus delbrueckii/virología , Fagos de Bacillus/efectos de los fármacos , Seguridad de Productos para el Consumidor , Productos Lácteos/virología , Microbiología de Alimentos , Lactobacillus delbrueckii/crecimiento & desarrollo , Lactobacillus delbrueckii/patogenicidad , Factores de Tiempo , Virulencia , Inactivación de VirusRESUMEN
Eleven Bacillus isolates from the surface and subsurface waters of the Gulf of Mexico were examined for their capacity to sporulate and harbor prophages. Occurrence of sporulation in each isolate was assessed through decoyinine induction, and putative lysogens were identified by prophage induction by mitomycin C treatment. No obvious correlation between ability to sporulate and prophage induction was found. Four strains that contained inducible virus-like particles (VLPs) were shown to sporulate. Four strains did not produce spores upon induction by decoyinine but contained inducible VLPs. Two of the strains did not produce virus-like particles or sporulate significantly upon induction. Isolate B14905 had a high level of virus-like particle production and a high occurrence of sporulation and was further examined by genomic sequencing in an attempt to shed light on the relationship between sporulation and lysogeny. In silico analysis of the B14905 genome revealed four prophage-like regions, one of which was independently sequenced from a mitomycin C-induced lysate. Based on PCR and transmission electron microscopy (TEM) analysis of an induced phage lysate, one is a noninducible phage remnant, one may be a defective phage-like bacteriocin, and two were inducible prophages. One of the inducible phages contained four putative transcriptional regulators, one of which was a SinR-like regulator that may be involved in the regulation of host sporulation. Isolates that both possess the capacity to sporulate and contain temperate phage may be well adapted for survival in the oligotrophic ocean.
Asunto(s)
Fagos de Bacillus/genética , Bacillus/fisiología , Lisogenia , Agua de Mar/microbiología , Bacillus/genética , Bacillus/virología , Fagos de Bacillus/efectos de los fármacos , Fagos de Bacillus/fisiología , Bacillus anthracis/efectos de los fármacos , Bacillus anthracis/genética , Secuencia de Bases , ADN Viral/genética , Genoma Bacteriano , Genoma Viral , Integrasas/genética , Lisogenia/efectos de los fármacos , Microscopía Electrónica de Transmisión , Mitomicina/farmacología , Datos de Secuencia Molecular , Océanos y Mares , Profagos/efectos de los fármacos , Profagos/genética , Profagos/fisiología , Esporas Bacterianas/efectos de los fármacos , Esporas Bacterianas/genética , Proteínas Virales/genética , Activación Viral/efectos de los fármacos , Activación Viral/genética , Activación Viral/fisiología , Integración Viral/efectos de los fármacos , Replicación Viral/efectos de los fármacos , Replicación Viral/genéticaRESUMEN
The effect of several biocides, thermal treatments, and photocatalysis on the viability of four Lactobacillus plantarum phages was investigated. Times to achieve 99% inactivation (T99) of phages at 63, 72, and 90 degrees C were evaluated in four suspension media: deMan Rogosa Sharpe broth, reconstituted skim milk, a commercial EM-glucose medium, and Tris magnesium gelatin buffer. The four phages studied were highly resistant to 63 degrees C (T99 > 45 min); however, counts < 10 PFU/ml were achieved by heating at 90 degrees C for 5 min. Higher thermal resistance at 72 degrees C was observed when reconstituted skim milk and EM-glucose medium were assayed. Peracetic acid (0.15%, vol/vol) was an effective biocide for the complete inactivation of all phages studied within 5 min of exposure. Sodium hypochlorite (800 ppm) inactivated the phages completely within 30 min. Ethanol (100%) did not destroy phage particles even after 45 min. Isopropanol did not have any effect on phage viability. Phage counts < 50 PFU/ml were obtained within 180 min of photocatalytic treatment. The results obtained in this work are important for establishing adequate methods for inactivating phages in industrial plants and laboratory environments.