Franca Rossi | Università Degli Studi Di Verona (original) (raw)

Papers by Franca Rossi

Journal of Apicultural Research, Nov 22, 2019

Insects, Nov 16, 2018

The application of quantitative PCR (qPCR) as a routine method to detect and enumerate Paenibacil... more The application of quantitative PCR (qPCR) as a routine method to detect and enumerate Paenibacillus larvae in honey and hive debris could greatly speed up the estimation of prevalence and outbreak risk of the American foulbrood (AFB) disease of Apis mellifera. However, none of the qPCR tests described so far has been officially proposed as a standard procedure for P. larvae detection and enumeration for surveillance purposes. Therefore, in this study, inclusivity, exclusivity and sensitivity of detection of P. larvae spores directly in samples of honey and hive debris were re-evaluated for the previously published qPCR methods. To this aim, recently acquired P. larvae sequence data were considered to assess inclusivity in silico and more appropriate non-target species were used to verify exclusivity experimentally. This led to the modification of a previously described method by shortening the forward primer, designing a new reverse primer and using more stringent amplification conditions. The new test allowed the detection of P. larvae spores in honey and hive debris down to 1 CFU/g. The qPCR test optimized in this study proved suitable for quantification and also for identification of field P. larvae strains and real contaminated samples. Therefore, it is proposed for reliable detection and quantification of P. larvae in honey and hive debris, thus circumventing the disadvantages of late AFB diagnosis based on clinical symptoms and possible underestimation of spore numbers that is the main drawback of culture-dependent procedures.

This study aimed to evaluate the hazards posed by foodborne bacteria of the Listeria genus by ana... more This study aimed to evaluate the hazards posed by foodborne bacteria of the Listeria genus by analyzing prevalence, diversity and virulence of Listeria spp. in food and food manufacturing plants. Seventy five isolates obtained from the routine analysis of 653 samples by three diagnostic laboratories in Northern Italy were genotipically differentiated by Repetitive Extragenic Palindrome (rep) PCR with the GTG5 primer, identified by sequencing the 16S rRNA gene and examined by specific PCR tests for the presence of L. monocytogenes virulence determinants occasionally found to occur in other species of the genus. The identity of the amplification products was confirmed by sequencing. Fifty seven isolates were identified as L. innocua, 12 as L. monocytogenes, 5 as L. welshimeri and one as L. seeligeri. All L. monocytogenes isolates belonged to the serotype 1/2a and were predicted to be virulent for the presence of the inlJ internalin gene. Potentially virulent strains of L. innocua, L. seeligeri and L. welshimeri, carrying the L. monocytogenes inlA gene and/or hly gene, were identified, and most isolates were found to possess the toxin-antitoxin system mazEF for efficient adaptation to heat shock. Results indicated the need to reinforce food contamination prevention measures against all Listeria species by efficiently defining their environmental distribution.

Challenges, Feb 28, 2018

In this context, an overview is presented of the book "Microbiology in dairy processing; challeng... more In this context, an overview is presented of the book "Microbiology in dairy processing; challenges and opportunities", edited by Palmiro Poltronieri, researcher at the Institute of Sciences of Food Productions of the Italian National Research Council and published by Wiley-Blackwell, for the Institute of Food Technologist (IFT) press series (

Challenges, Feb 14, 2016

Bacteriocinogenic cultures can represent a natural way to increase the safety of cheeses made fro... more Bacteriocinogenic cultures can represent a natural way to increase the safety of cheeses made from raw milk, in which a relevant role in ripening and flavor formation is exerted by the nonstarter lactic acid bacteria (NSLAB). Since the latter can be inhibited by bacteriocin producers, this study evaluated to which extent a nisinogenic culture inoculated at low initial levels can affect the growth rate and peptide degradation activity of the nisin-sensitive cheese isolate Lactobacillus plantarum LZ by comparison with its isogenic variant, L. plantarum LZNI, with increased immunity to nisin. A growth delay of the nisin sensitive strain was observed only when its initial number was 100-fold lower than the nisin producer and nisin was added as an inducer of its own production. In this case, the amount of free α-amino groups was significantly different between cultures of L. plantarum LZ and LZNI only at Day 1. Reverse Phase High Performance Liquid Chromatography (RP-HPLC) highlighted a few differences between the peptide profiles of co-cultures L. plantarum LZ and LZNI. However, results showed that the bacteriocin producer did not dramatically influence the behavior of the sensitive NSLAB and that the evaluation of the effects on microbial contaminants in cheese is worthwhile.

Microorganisms, May 10, 2019

Microorganisms belonging to the Lactobacillus genus complex (LGC) are naturally associated or del... more Microorganisms belonging to the Lactobacillus genus complex (LGC) are naturally associated or deliberately added to fermented food products and are widely used as probiotic food supplements. Moreover, these bacteria normally colonize the mouth, gastrointestinal (GI) tract, and female genitourinary tract of humans. They exert multiple beneficial effects and are regarded as safe microorganisms. However, infections caused by lactobacilli, mainly endocarditis, bacteremia, and pleuropneumonia, occasionally occur. The relevance of Lactobacillus spp. and other members of the LGC as opportunistic pathogens in humans and related risk factors and predisposing conditions are illustrated in this review article with more emphasis on the species L. rhamnosus that has been more often involved in infection cases. The methods used to identify this species in clinical samples, to distinguish strains and to evaluate traits that can be associated to pathogenicity, as well as future perspectives for improving the identification of potentially pathogenic strains, are outlined.

Journal of Apicultural Research, 2021

American foulbrood (AFB) is one of the most devastating infectious diseases of honey bees with a ... more American foulbrood (AFB) is one of the most devastating infectious diseases of honey bees with a worldwide distribution. Based on clinical symptoms of AFB, the disease has been thought to have long...

Hygienic characteristics of fresh dairy products with a short period of preservation are taking u... more Hygienic characteristics of fresh dairy products with a short period of preservation are taking up at present far more importance. In the case of cheeses made from pasteurized milk the final hygienic quality is strongly influenced by secondary contaminations occurring during the technological process of production. A previous research allowed to recognize possible points of contamination in the processing phases between salting in brine and packaging. The present work evaluates the effect of secondary contaminations on the length of the preservation period through microbiological determinations on cow's milk Mozzarella cheese packaged in different ways. The samples were partly hand wrapped up with the procedure currently adopted by the dairy plant (A) and partly drawn aseptically soon after cutting off, salted in sterile brine and wrapped up wearing sterile mask and gloves (B). All the samples came from the same processing cycle. Half the samples of groups A and B were stored at 4°C and the rest was kept at 20°C. The analysis at 0, 2, 4 and 7 days gave different values of microbial counts for each series of samples. Test B stored at 4°C showed every time lower numbers of microorganisms for all the microbial groups taken into account, thus pointing out a method in perfect agreement with a longer shelf-life of the product

ABSTRACT The effect of different temperatures on the shelf-life of Mozzarella cheese was studied.... more ABSTRACT The effect of different temperatures on the shelf-life of Mozzarella cheese was studied. pH, non-protein nitrogen, moisture, total proteins, methyl esters of combined fatty acids, Total Viable Count, lactic acid bacteria, enterococci, Micrococcaceae, Enterobacteriaceae, psychrotrophic bacteria, Pseudomonas, yeasts and moulds were evaluated during 9 days of storage at 4 degrees, 7 degrees and 13 degrees C. Samples stored at 4 degrees and 7 degrees C showed insignificant variations in the chemical parameters and acceptable increases of the microbial groups. Samples stored at 13 degrees C exhibited a greater increase in the microbial number and higher non-protein nitrogen.

Challenges, Oct 24, 2016

Coffee is an important crop that assures a sustainable economy to farmers in tropical regions. A ... more Coffee is an important crop that assures a sustainable economy to farmers in tropical regions. A dramatic concern for coffee production is currently represented by climate change, which threatens the survival of Coffea arabica cultivation worldwide and imposes modifications of the agronomic practices to prevent this risk. The quality of coffee beans depends on optimized protocols of cultivation, ripe berries collection, and removal of the outer fruit layers by dry or wet processes and moisture reduction. Storage and shipment represent two steps where bean quality needs to be preserved by preventing fungal contamination that may impact the final product and form mycotoxins, mainly ochratoxin A. In this review, we describe the challenges faced by the coffee industry to guarantee quality from production to roasting and brewing. An overview of novel technologies, such as the application of starter cultures in fermentation and the exploitation of industrial enzymes in accelerating the process of flavour development in coffee beans, is given. Moreover, the results of studies on microbial populations on coffee and the differences found in fungi, yeasts and bacteria composition among the investigations, are summarized. In particular, this review describes new attempts to contain the development of mycotoxigenic fungi, through the application of antagonistic microorganisms such as S. cerevisiae. The new wave of specialty coffees, i.e., those with a cupping score higher than 85/100, is also presented. It is shown how, through careful coffee production methods and controlled fermentation processes, coffee producers may increase their income by assuring high standards of quality and high added value for the coffee experience sector.

Microorganisms

This study aims to explore the intra-species distribution of genetic characteristics that favor t... more This study aims to explore the intra-species distribution of genetic characteristics that favor the persistence in the gastrointestinal tract (GIT) and host interaction of bacteria belonging to species of the Lacticaseibacillus genus. These bacterial species comprise commercial probiotics with the widest use among consumers and strains naturally occurring in GIT and in fermented food. Since little is known about the distribution of genetic traits for adhesion capacity, polysaccharide production, biofilm formation, and utilization of substrates critically important for survival in GIT, which influence probiotic characteristics, a list of genetic determinants possibly involved in such functions was created by a search for specific genes involved in the above aspects in the genome of the extensively characterized probiotic L. rhamnosus GG. Eighty-two gene loci were retrieved and their presence and variability in other Lacticaseibacillus spp. genomes were assessed by alignment with the ...

Ventricina del Vastese is a traditional dry fermented sausage from Central Italy not yet charac-t... more Ventricina del Vastese is a traditional dry fermented sausage from Central Italy not yet charac-terized for occurrence, identity and safety of coagulase negative staphylococci (CNS), a bacterial group technologically important for this kind of products. Therefore, in this study, 98 CNS isolates from four manufacturers were differentiated by Repetitive element palindromic PCR (Rep-PCR) and identified by 16S rRNA gene sequencing. These were examined for genes encoding biogenic amine (BA) production, resistance to aminoglycosides, β-lactams and tetracyclines and staphylococcal enterotoxins (SEs). Staphylococcus succinus (55%) predominated, followed by S. xylosus (30%), S. epidermidis (7.4%), S. equorum (3.1%), S. saprophyticus (3.1%) and S. warneri (1%). One S. succinus subsp. casei isolate was slightly β-hemolytic. SEs and the histidine decarboxylase gene hdcA were not detected, while the tyrosine decarboxylase gene tdcA was detected in four S. xylosus isolates. A blaZ beta-lactamase ...

Annals of Microbiology, 2002

ABSTRACT Abstract: This study was undertaken to achieve more information on the aminopeptidase ac... more ABSTRACT Abstract: This study was undertaken to achieve more information on the aminopeptidase activities expressed in Propionibacterium freudenreichii strains naturally occurring in milk and dairy products. Fifty four strains belonging to both subspecies freudenreichii and shermanii were analyzed for activity towards different amino acyl beta-naphthylamide (betaNA) derivatives. The ability to efficiently hydrolyze aminoterminal leucine was common to all the isolates, with notably high activities for five strains. Proline iminopeptidase activity was generally expressed. Accordingly, PCR targeted to the P. freudenreichii ATCC 9617 prolyl iminopeptidase encoding gene (pip) demonstrated its presence in all but three strains. Activity towards Lys- and Arg-betaNA was less expressed and strain-dependent. The X-prolyl-dipeptidyl aminopeptidase activity was relatively low in absence of NaCl. It increased in presence of 3% NaCl only toward Phe-Pro-betaNa and not toward Gly-Pro-betaNA. The substrate Glu-betaNA was not cleaved by any strain. Findings suggest that the adventitious P. freudenreichii strains may have a significant and variable effect on secondary proteolysis of hard cheeses, being a possible factor of organoleptic differences.

Journal of Applied Microbiology, Mar 2, 2001

Aims: To ascertain 1 the identi®cation and typing of the Gram-positive, coagulase-negative cocci ... more Aims: To ascertain 1 the identi®cation and typing of the Gram-positive, coagulase-negative cocci present in`Salsiccia Sotto Sugna', an Italian artisanal sausage. Methods and Results: Fifty-one strains were isolated and genotypically identi®ed by ampli®cation of the 16S±23S rDNA intergenic region with universal primers. Most isolates were identi®ed as Staphylococcus xylosus and one strain as Staph. condimenti. Isolates were clustered by numerical analysis of both RAPD (Random Ampli®ed Polymorphic DNA) PCR pro®les and physiological characters. Genotypic clustering allowed the separation of strains showing nitrate reduction and amino acid decarboxylase activities. Phenotypic clustering distinguished strains isolated at diverse ripening stages. Conclusions: The predominance of Staph. xylosus in Italian dry sausages was con®rmed. Genotypic similarities related to the possession of single phenotypic traits. Signi®cance and Impact of the Study: In this study, a rapid method of Staphylococcus and Kocuria species distinction was proposed. The suitability of RAPD PCR to discriminate strains of Staph. xylosus with technologically relevant activities was reported.

Streptococcus thermophilus is an important component of the starter cultures used in many dairy p... more Streptococcus thermophilus is an important component of the starter cultures used in many dairy products. Strains of this species are mainly selected on the basis of acidifying capacity, while the possibility of use of bacteriocins producers belonging to this species as protective agents in dairy products has been little considered. In recent years, several reports have described S. thermophilus strains as bacteriocin producers and some of the antimicrobial peptides have been purified and sequenced. These proteinaceous compounds, called thermophilins, have been found to inhibit pathogenic and spoilage microbes such as clostridia and Listeria. Bacteriocin producing S. thermophilus strains able to dominate in natural ecosystems might constitute a mean to increase the safety of products obtained with natural cultures. Therefore, in this study the natural occurrence of bacteriocin producers in the species S. thermophilus was evaluated by examining 75 strains isolated from whey and milk cultures for cheesemaking, different cheeses made from raw milk and the plants Plantago lanceolata and Rosa canina. Though PCR tests showed the presence of genes encoding known thermophilins in most strains, only sixteen were active against at least one of the bacterial indicators tested. The involvement of a proteinaceous compound was ascertained in all the strains showing antimicrobial activity. These included representative strains of Clostridium tyrobutyricum, Enterococcus faecium, Escherichia coli, Listeria innocua, as a non pathogenic counterpart of L. monocytogenes, Staphylococcus aureus and common starter lactic acid bacteria belonging to the species Lactobacillus delbrueckii subsp. bulgaricus and lactis, L. helveticus, S. thermophilus and S. macedonicus. Only the two isolates from plants were active against E. coli. All the active strains inhibited Staphylococcus aureus, most inhibited some starter microorganisms and none inhibited Listeria innocua and Clostridium tyrobutyricum. Therefore a limited potential of natural thermophilin producers as biopreserving agents was put in evidence. For the two strains with a wider inhibition spectrum, i.e. S. thermophilus PRI36 and PRI45, the arrangement of the genes encoding the most active components of the thermophilin 9 complex was elucidated. Results highlighted a high level of variability in sequence and gene content

BioMed Research International, 2014

Large antibiotic resistance gene pools in the microbiota of foods may ultimately pose a risk for ... more Large antibiotic resistance gene pools in the microbiota of foods may ultimately pose a risk for human health. This study reports the identification and quantification of tetracycline-and erythromycin-resistant populations, resistance genes, and gene diversity in traditional Spanish and Italian cheeses, via culturing, conventional PCR, real-time quantitative PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE). The numbers of resistant bacteria varied widely among the antibiotics and the different cheese varieties; in some cheeses, all the bacterial populations seemed to be resistant. Up to eight antibiotic resistance genes were sought by gene-specific PCR, six with respect to tetracycline, that is, tet(K), tet(L), tet(M), tet(O), tet(S), and tet(W), and two with respect to erythromycin, that is, erm(B) and erm(F). The most common resistance genes in the analysed cheeses were tet(S), tet(W), tet(M), and erm(B). The copy numbers of these genes, as quantified by qPCR, ranged widely between cheeses (from 4.94 to 10.18log 10 /g). DGGE analysis revealed distinct banding profiles and two polymorphic nucleotide positions for tet(W)-carrying cheeses, though the similarity of the sequences suggests this tet(W) to have a monophyletic origin. Traditional cheeses would therefore appear to act as reservoirs for large numbers of many types of antibiotic resistance determinants.