Selective pressure in the aquatic environment of intensive fish farms leads to acquired antibiotic resistance. This study used the broth microdilution method to measure minimum inhibitory ...concentrations (MICs) of 15 antibiotics against 104 Aeromonas spp. strains randomly selected among bacteria isolated from Sparus aurata reared in six Italian mariculture farms. The antimicrobial agents chosen were representative of those primarily used in aquaculture and human therapy and included oxolinic acid (OXA), ampicillin (AM), amoxicillin (AMX), cephalothin (CF), cloramphenicol (CL), erythromycin (E), florfenicol (FF), flumequine (FM), gentamicin (GM), kanamycin (K), oxytetracycline (OT), streptomycin (S), sulfadiazine (SZ), tetracycline (TE) and trimethoprim (TMP). The most prevalent species selected from positive samples was Aeromonas media (15 strains). The bacterial strains showed high resistance to SZ, AMX, AM, E, CF, S and TMP antibiotics. Conversely, TE and CL showed MIC90 values lower than breakpoints for susceptibility and many isolates were susceptible to OXA, GM, FF, FM, K and OT antibiotics. Almost all Aeromonas spp. strains showed multiple antibiotic resistance. Epidemiological cut-off values (ECVs) for Aeromonas spp. were based on the MIC distributions obtained. The results showed a high frequency of Aeromonas spp. contamination in Sparus aurata reared on the Italian coast and an elevated biodiversity in isolated bacterial strains. Aeromonas isolates comprise potentially pathogenic species for humans, often resistant to several antibiotics and able to transfer the genes responsible for antibiotic resistance to microorganisms pathogenic for humans throughout the food chain. The few ECV studies available on many antibiotics against Aeromonas spp. strains isolated from the aquaculture environment highlight the need for further research in this area, while regular monitoring programmes should be stepped up to check for antibiotic resistance.
•Aeromonas spp. strains isolated from Sparus aurata were tested against 15 antibiotics.•Almost all strains showed multiple antibiotic resistance.•Epidemiological cut-off values (ECV) revealed a high prevalence of wild-type strains.
Four different classes of HDACs have been identified in humans so far. Classes I, II and IV are zinc-dependent amidohydrolases, while III is a family of phylogenetically conserved NAD-dependent ...protein deacetylases/ADP-ribosyltransferase with a well-defined role in modifying chromatin conformation and altering the accessibility of the damaged sites of DNA for repair enzymes. Sirtuins are histone deacetylases (HDACs) of class III that cleave off acetyl groups from acetyl-lysine residues in histones and non-histone proteins. As sirtuins are involved in many physiological and pathological processes, their activity has been associated with different human diseases, including cancer. Especially two sirtuin members, SIRT1 and SIRT2, have been found to antagonize p53-dependent transcriptional activation and apoptosis in response to DNA damage by catalyzing p53 deacetylation. The findings that SIRT1 levels are increased in a number of tumors highlight the oncogenic role of sirtuins, in particular, in the down-modulation of p53 oncosuppressor activity. Along this lane, cancers carrying wild-type (wt) p53 protein are known to deregulate its activity by other mechanisms. Therefore, inhibition of SIRT1 and SIRT2, aimed at restoring wt-p53 transcriptional activity in tumors that retain the ability to express normal p53, might represent a valid therapeutic cancer approach specially when combined with standard therapies. This review will be focused on sirtuin inhibitors, with a specific attention on inhibitors of SIRT1 and SIRT2. Among them, nicotinamide and its analogs, sirtinol, A3 and M15, splitomicin, HR73 and derivatives, cambinol and derivatives, EX 527, kinase inhibitors, suramin, 4-dihydropyridine derivatives, tenovins, TRIPOS 360702, AC 93253, 3-arylideneindolinones, CSC8 and CSC13 will also be described.
Ricotta fresca is a whey cheese susceptible of secondary contamination, mainly from Pseudomonas spp. The extension of the shelf life of refrigerated ricotta fresca could be obtained using protective ...cultures inhibiting the growth of this spoilage microorganism. A commercial biopreservative, Lyofast CNBAL, comprising Carnobacterium spp was tested against Pseudomonas spp. The surface of ricotta fresca samples were inoculated either with Pseudomonas spp or Pseudomonas and Carnobacterium spp. Samples were MAP packed, stored at 4 °C and analyzed the day of the inoculum and 7, 14 and 21 days after the contamination. Microbiological analyses included total bacterial count, mesophilic lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp, Listeria monocytogenes, moulds and yeasts. Pseudomonas mean initial contamination level was comparable in blank and artificially inoculated samples, respectively with values of 2.15 ± 0.21 and 2.34 ± 0.26 log cfu g−1. Carnobacterium spp. significantly reduced the growth of Pseudomonas spp respectively of 1.28 log and 0.83 log after 14 and 21 days of refrigerated storage. Intrinsic properties and physico-chemical composition were also investigated. Limited variation of pH was observed in samples inoculated with the protective cultures, indicating low acidification properties of Carnobacterium spp. Instead, no significant differences were observed for aW, moisture, fat and proteins during storage and between inoculated and control samples.
•Pseudomonas spp is the main spoilage microorganism in refrigerated ricotta fresca.•A microbiological challenge test was conducted on MAP ricotta fresca samples.•Carnobacterium spp commercial protective culture was tested against Pseudomonas spp.•Inoculation of Carnobacterium spp protective culture reduced Pseudomonas spp growth.
AIMS: The present study aimed to determine, by multilocus sequence type (MLST), the heterogeneity level of Arcobacter butzleri isolates and to compare MLST and pulsed‐field gel electrophoresis (PFGE) ...in terms of discriminatory power (DI) as well as unidirectional and bi‐directional concordance. METHODS AND RESULTS: Arcobacter butzleri isolates (N = 133) from dairy products and environmental samples, collected from dairy plants, were characterized by MLST and PFGE with SacII and classified in 29 sequence types (STs), 47 PFGE and 62 type strains (TS). Among the 119 alleles, 19 were previously unreported and the same for all the STs but two. A significant linkage disequilibrium was detected when the complete ST data set was analysed The DIs of MLST, PFGE and their combination were 0·937, 0·953 and 0·965 respectively. The adjusted Wallace coefficients between MLST and PFGE as well as PFGE and MLST were 0·535 and 0·720 respectively; the adjusted Rand coefficient was 0·612. CONCLUSIONS: The A. butzleri studied population showed recombination to some degree. PFGE showed a DI higher than MLST. Both methods presented good concordance. The TS analysis seems to show persistence of the same strain on time and possible cross‐contaminations between food and environmental sites. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides insights in the A. butzleri population found in raw milk, cheese, and dairy production plants. The data suggest that MLST and PFGE genotypes correlate reasonably well, although their combination results in optimal resolution.
Ricotta fresca cheese is susceptible to secondary contamination and is able to support the growth of pathogens or spoilage psychotrophic bacteria during storage. The aim of the present study was to ...evaluate which among three commercial biopreservatives was suitable to be used to control the growth of spoilage microorganisms in sheep's milk MAP ricotta fresca cheese. 144 Ricotta fresca cheese samples were inoculated either with the bioprotective culture Lyofast FPR 2 (including Enterococcus faecium, Lactobacillus plantarum e Lactobacillus rhamnosus) or Lyofast CNBAL (Carnobacterium spp) or the fermentate MicroGARD 430. Not inoculated control and experimental ricotta were MAP packed (30% CO2 and 70% N2) and stored at 4 °C. Triplicate samples were analyzed after 5 h and 7, 14 and 21 days after inoculation for total bacterial count, mesophilic lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp, Listeria monocytogenes, moulds and yeasts. Among the tested biopreservatives only Carnobacterium spp was able to control Pseudomonas spp and Enterobacteriaceae. The maximum reduction in the concentration of Pseudomonas spp and Enterobacteriaceae was respectively 1.93 and 2.66 log10 cfu/g, observed 14 days after production. Therefore, Carnobacterium spp was selected as the culture of choice to conduct a challenge study against Pseudomonas spp.
•Ricotta fresca support psychotrophic microorganism growth during refrigerated storage.•3 Commercial biopreservatives were tested against spoilage bacteria in ricotta fresca.•Cultures Lyofast FPR 2, Lyofast CNBAL and the fermentate FERM 430D were tested.•Inoculation of Carnobacterium spp protective culture reduced Pseudomonas spp growth.
► PCDD/Fs and PCBs were determined in sheep milk samples. ► Milk samples were collected from an industrialized area of Sardinia, Italy. ► Overall milk contamination level was below the limit values ...for human consumption. ► Samples the nearest to pollution sources had concentrations above the action level. ► On the whole the results revealed a situation of moderate contamination.
Concentrations of 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs) and 22 polychlorinated biphenyls (PCBs), including 12 dioxin like-PCBs (non- and mono-ortho PCBs) were measured in 80 sheep milk samples from farms located in an industrialized area of Sardinia, Italy. PCDDs and PCDFs mean concentrations were 2.45 and 3.69pgg−1 fat basis, respectively. The mean dl-PCB concentration was 2.01ngg−1 fat basis, while cumulative ndl-PCB levels ranged from 1.02 to 20.42, with a mean of 4.92ngg−1 fat. The results expressed in pg WHO-TEQ/g fat showed that contamination level of milk was below the limit values for human consumption established by EC legislation. In the same way, all the investigated milk exhibited PCDD/Fs concentrations below EU action levels, while dl-PCBs concentrations exceeded the action level of 2.0pg WHO-TEQ/g fat. These findings point to the need to continue to conduct general monitoring programmes, including also milk samples from areas not close to the contaminant-emitting industries, in order to better evaluate the impact of industrial activities on surrounding environment.
Growth potential of Listeria monocytogenes was assessed in Ricotta salata, a traditional sheep’s whey cheese. 36 Ricotta salata wheels were inoculated with a mixture of three L. monocytogenes strains ...obtaining an inoculum level of approximately 102 cfu g−1. Samples were analyzed for the detection and enumeration of L. monocytogenes after 6 h, and after 2, 4 and 6 months. Growth potential (log10 cfu g−1) was 4.87, 6.90 and 6.20 at 2, 4 and 6 months, respectively. The greater relative rate of increase in L. monocytogenes levels was obtained in the first 2 months after inoculation. Ricotta salata supports the growth of L. monocytogenes to levels that may represent a serious risk to public health even during storage at refrigeration temperatures. Further research is needed to assess the effectiveness of post-lethality treatments to reduce the initial level of contamination or of competitive microflora to limit the extent of pathogen growth.
As a control measure for Listeria monocytogenes contamination a post-lethality heat treatment was applied in vacuum packaged Ricotta salata, a traditional whey cheese obtained from sheep’s milk. In ...Ricotta salata L. monocytogenes usually occurs as post-process contamination and its concentration can increase during storage at refrigeration temperature. Ricotta salata wheels were challenged spraying the rind with a L. monocytogenes suspension, obtaining a contamination level of ca. 106 cfu g−1. In order to take into account strains differences in growth, the inoculum contained a mixture of the reference strain NCTC 10887 (serovar 1/2b) and two wild type (serovar 1/2a) strains. 87 artificially contaminated Ricotta wheels were randomly selected and subjected to water bath heat treatment at 85 °C for 90 min, while 21 served as negative controls. Samples were stored at refrigeration temperatures until analysis. L. monocytogenes, background microflora and physico-chemical properties were assessed 6 h, 2, 4, 6 and 12 months after the artificial contamination. Pulsed filed gel electrophoresis was conducted to distinguish between the inoculated and recovered strains. L. monocytogenes cells were below the limit for the enumeration method in samples submitted to the lethal treatment. Heat treatment was effective to achieve a 6 log10 reduction of L. monocytogenes cells.
► We assessed the effectiveness of heat treatment on L. monocytogenes survival. ► Ricotta salata were contaminated with a mixture of 3 L. monocytogenes strains. ► A reduction of 6 log10 cfu g−1 in L. monocytogenes count was obtained.
The study investigated Salmonella prevalence in slaughtered wild boars from Asinara island National Park in Sardinia (Italy). Salmonella isolates were serotyped and the antimicrobial resistance ...profile was evaluated. Isolates were furthermore characterized with Whole Genome Sequencing. Additional analysis were performed in order to evaluate the microbial hygiene of wild boars carcasses.
A total of 306 samples were tested for Salmonella presence, of which n. 270 were from n. 90 slaughtered wild boars and n. 36 were from slaughterhouse environment. Salmonella was detected in 32/90 (35.6%) colon content and 16/90 (17.8%) mesenteric lymph nodes samples. The overall prevalence of Salmonella carriers wild boars, either in colon content and/or lymph nodes, was 42/90 (46.7%) but only one animal was found positive at carcass level. Prevalence was not influenced (P > 0.05) by the age and the gender of the animals. Eight different Salmonella serotypes were identified between 50 isolates, with the most common ones being Abony and Newport. The sequence analysis showed that S. Abony and S. Newport strains clustered separately from public genomes. This finding refects the origin of the animals from the geographical closed environment of Asinara island. Moreover, sequence analysis showed high similarity between strains belonging to the same serovar. S. Derby and S. Agona strains exhibited phenotypic resistance to fosfomycin and harboured the fosA7 gene. The mean aerobic colony count and Enterobacteriaceae values showed a good hygiene level of the carcasses. This study demonstrated that Salmonella enterica is widespread in wild boar population of Asinara island and could play an important role in transmission to humans. The finding of Salmonella strains resistant to fosfomycin is of primary importance as this drug is used as an alternative treatment for infections caused by multi-drug resistant microorganisms.
•Salmonella in wild boar play a role in transmission to humans.•High variability of Salmonella serovars.•High similarity of Salmonella serovars with whole genome sequencing.•Extended sensitivity to antimicrobials.•Fosfomycin resistance encoded by the gene fosA7 in S. Agona and S. Derby isolates.
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