Methicillin Resistant Staphylococcus aureus (MRSA) in raw buffalo milk and its fate along the human gastrointestinal tract: an in vitro study

Methicillin resistant Staphylococcus aureus (MRSA) has become one of the major public health challenges worldwide. MRSA strains are capable of causing from mild non-life-threatening to severe infections of the skin and soft tissues, and even death. Skin infections caused by MRSA include primary pyodermas such as folliculitis, furuncles, carbuncles, and impetigo. Infections involving the soft tissues include cellulitis and pyo-myositis, which are less common but can cause serious morbidity. The contamination of raw food, especially meat and milk, by MRSA is well documented as well as its transmission to humans via animal contact. In addition, humans can act as reservoirs of MRSA without showing any clinical signs, thus they can contaminate foods by handling. Its presence in several kinds of food has suggested the possibility of MRSA to act as a foodborne pathogen. Although the hypothesis is suggestive, there are insufficient evidence to consider the foodstuff a vehicle of MRSA infection. For instance, nothing is known about its ability to survive under human gastroenteric conditions. Despite of the potential hazard for human health there is a lack of date on prevalence of MRSA in some foods, such as buffalo milk and buffalo dairy products. The high consumptions of buffalo drinking milk and dairy products worldwide involve an elevated number of consumers of all ages, and this is crucial considering their potential role in the transmission of foodborne pathogens. To address these issues, the aims of the thesis are: i) to assess the occurrence of MRSA in new ecological niches such as buffalo dairy farms and buffalo tank milk from Italy in order to better understand the epidemiology of MRSA ii) to study the fate of MRSA strains isolated from foods and from humans along the human gastrointestinal tract and its inter-species interaction with the human gut microbiota. Regarding the occurrence of MRSA in raw buffalo milk, seventy-five bulk tank milk (BTM) samples from farms and 24 nasal swabs from farm workers were collected, respectively. Three (4%) out of 75 BTM samples and 1 (4%) out of 24 nasal swabs were MRSA-positive. The milk isolates showed the following genotypes: ST1/t127/Va and ST72/t3092/V, while the human isolate was characterized as ST1/t127/IVa. No ST398 were found. All the isolates were multidrug resistant but vancomycin susceptible, carrying the icaA gene, while they tested negative for pvl and ses genes. This study demonstrates for the first time in Europe that MRSA might be present in dairy buffalo farms and in raw buffalo milk. For what concern the second aim, a MRSA ST398/t011/V strain, previously isolated from raw cow milk, and a human origin MRSA strain were inoculated into two foods of animal origin respectively. The pH of the matrices was gradually decreased to 2.0 in 2 hours, during which time they were kept at 37°C and periodically homogenized. The same MRSA strains levels were inoculated within an intestinal in vitro simulator and it was periodically analyzed their fate along the whole transit. Mucin agar carriers replaced the intestinal mucus layer and a basic feed medium represented the intestinal lumen contents. A three-day in vitro study was performed using microbiota from the pooled faeces of healthy individuals that were stabilized simulating colon conditions. The MRSA population survived the decreasing gastric pH levels unharmed, but it was affected by the organic acids produced by the enteric microbiota along the transit into the simulator. It was, in fact, no longer viable after 24 h of incubation with luminal colon microbiota, whereas counts of 4 log cfu/g were still obtained in the mucin agar carriers after 72 h of incubation. Despite the ability of MRSA to overcome human stomach acidic conditions, these results confirm the hypothesis that competitive microbiota may control MRSA intestinal colonization

Observer Placement for Source Localization: The Effect of Budgets and Transmission Variance

When an epidemic spreads in a network, a key question is where was its source, i.e., the node that started the epidemic. If we know the time at which various nodes were infected, we can attempt to use this information in order to identify the source. However, maintaining observer nodes that can provide their infection time may be costly, and we may have a budget $k$ on the number of observer nodes we can maintain. Moreover, some nodes are more informative than others due to their location in the network. Hence, a pertinent question arises: Which nodes should we select as observers in order to maximize the probability that we can accurately identify the source? Inspired by the simple setting in which the node-to-node delays in the transmission of the epidemic are deterministic, we develop a principled approach for addressing the problem even when transmission delays are random. We show that the optimal observer-placement differs depending on the variance of the transmission delays and propose approaches in both low- and high-variance settings. We validate our methods by comparing them against state-of-the-art observer-placements and show that, in both settings, our approach identifies the source with higher accuracy.Comment: Accepted for presentation at the 54th Annual Allerton Conference on Communication, Control, and Computin

Systemic Lupus Erythematosus with and without Anti-dsDNA Antibodies: Analysis from a Large Monocentric Cohort

Objectives. The anti-dsDNA antibodies are a marker for Systemic Lupus Erythematosus (SLE) and 70–98% of patients test positive. We evaluated the demographic, clinical, laboratory, and therapeutical features of a monocentric SLE cohort according to the antidsDNA status. Methods. We identified three groups: anti-dsDNA + (persistent positivity); anti-dsDNA ± (initial positivity and subsequent negativity during disease course); anti-dsDNA − (persistent negativity). Disease activity was assessed by the European Consensus Lupus Activity Measurement (ECLAM). Results. We evaluated 393 patients (anti-dsDNA +: 62.3%; anti-dsDNA ±: 13.3%; anti-dsDNA −: 24.4%). The renal involvement was signifiantly more frequent in anti-dsDNA + (30.2%), compared with antidsDNA ± and anti-dsDNA − (21.1% and 18.7%, resp.; = 0.001). Serositis resulted signifiantly more frequent in anti-dsDNA − (82.3%) compared to anti-dsDNA + and anti-dsDNA ± (20.8% and 13.4%, resp.; < 0.0001). Th reduction of C4 serum levels was identified significantly more frequently in anti-dsDNA + and anti-dsDNA ± (40.0% and 44.2%, resp.) compared with antidsDNA − (21.8%, = 0.005). We did not identify significant differences in the mean ECLAM values before and after modifiation of anti-dsDNA status ( = 0.7). Conclusion. Anti-dsDNA status influences the clinical and immunological features of SLE patients. Nonetheless, it does not appear to affect disease activity

Contribution of L-Arginine supplementation during gestation on sow productive performance and on sow microbial faecal profile

Arginine plays an important role during reproduction, however, the amount of supplementation in sow diet is still uncertain. The aim of the study was to verify the efficacy of a gestating diet enriched or not with a low dose of L-arginine (Arg) on sow productive performance in terms of numbers and weight of piglets at birth and at weaning, frequency of intrauterine growth retardation (IUGR) and piglets' mortality, sow placenta weight and salivary humoral immunity and intestinal microbial balance of the sows. 205 sows (Landrace x Large White) were divided into two experimental groups: a control group (CON) (102 sows) and a group supplemented with 0.25% of Arg (ARG) for the whole pregnancy period. Saliva and faecal samples were collected two days before farrowing and used for immunoglobulins and microbial analysis, respectively. Arg improved the number of total born piglets (p = .043) and tended to improve the number of total born alive (p = .086) and to reduce IUGR % (p = .090) and dead piglets at d0–d3 (p = .088). The weight of placenta and humoral immunity were not influenced by Arg. Arg did not modify the faecal microbial structure (alpha and beta indices) but increased the relative abundance of Bacteroidaceae family and Bacteroides genera (p = .0001). The results support the knowledge that Arg plays a key role in nutrition and physiology of pregnant sows without compromising gut eubiosis.HighlightArg supplementation of sows' gestation diet increased the number of total bornsArg supplementation of sows' gestation diet did not negatively affect the sows' gut eubiosisArg plays a significant role in the nutrition of pregnant sows. Arg supplementation of sows' gestation diet increased the number of total borns Arg supplementation of sows' gestation diet did not negatively affect the sows' gut eubiosis Arg plays a significant role in the nutrition of pregnant sows

Global Emergence of Colistin-Resistant Escherichia coli in Food Chains and Associated Food Safety Implications: A Review

Antimicrobial resistance in bacteria represents one of the most important challenges for public health worldwide. Human infections from antimicrobial-resistant bacteria can be transmitted from person to person, via the environment (especially in the hospital environment), or via handling or eating contaminated foods. Colistin is well known as a last-resort antibiotic for the treatment of human infections; a recent study performed in the People's Republic of China has revealed that colistin resistance is also conferred by the plasmid-mediated mcr-1 gene in Escherichia coli. After that discovery, further plasmid-mediated, colistin resistance genes have been detected. However, to date, only reports on E. coli carrying the mcr-1 gene (E. coli mcr-1+) in foodstuff are available. E. coli mcr-1+ has been isolated from food of animal origin and vegetables; this discovery has opened a debate among food safety experts. This review aims to provide a critical overview of the currently available scientific literature on the presence of the plasmid-mediated, colistin resistance gene E. coli mcr-1 in foodstuffs, focusing on the main implications and future perspectives for food safety

Fate of Methicillin‐resistant Staphylococcus aureus (MRSA) under simulated acidic conditions of the human stomach

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A General Framework for Sensor Placement in Source Localization

When an epidemic spreads in a given network of individuals or communities, can we detect its source using only the information provided by a small set of nodes? We propose a general framework that incorporates two dimensions. First, we can either rely exclusively on a set of selected nodes (i.e., sensors) which always reveal their state independently of any particular epidemic (these are called static), or we can add some sensors (called dynamic) as an epidemic spreads, depending on which additional information is required. Second, the method can either localizes the source after an epidemic has spread through the entire network (offline), or while the epidemic is ongoing (online). We empirically study the performance of offline and online localization both with and without dynamic sensors. Our analysis shows that, by using dynamic sensors, the number of sensors necessary to localize the source is reduced by up to a factor of 10 and that, even with high-variance transmission delays, the source can be localized by using fewer than 5% of the nodes as sensors

The effect of transmission variance on observer placement for source-localization

Abstract Detecting where an epidemic started, i.e., which node in a network was the source, is of crucial importance in many contexts. However, finding the source of an epidemic can be challenging, especially because the information available is often sparse and noisy. We consider a setting in which we want to localize the source based exclusively on the information provided by a small number of observers – i.e., nodes that can reveal if and when they are infected – and we study where such observers should be placed. We show that the optimal observer placement depends not only on the topology of the network, but also on the variance of the node-to-node transmission delays. We consider both low-variance and high-variance regimes for the transmission delays and propose algorithms for observer placement in both cases. In the low-variance regime, it suffices to only consider the network-topology and to choose observers that, based on their distances to all other nodes in the network, can distinguish among possible sources. However, the high-variance regime requires a new approach in order to guarantee that the observed infection times are sufficiently informative about the location of the source and do not get masked by the noise in the transmission delays; this is accomplished by additionally ensuring that the observers are not placed too far apart. We validate our approaches with simulations on three real-world networks. Compared to state-of-the-art strategies for observer placement, our methods have a better performance in terms of source-localization accuracy for both the low- and the high-variance regimes

Budgeted sensor placement for source localization on trees

We address the problem of choosing a fixed number of sensor vertices in a graph in order to detect the source of a partially-observed diffusion process on the graph itself. Building on the definition of double resolvability we introduce a notion of vertex resolvability. For the case of tree graphs we give polynomial time algorithms for both finding the sensors that maximize the probability of correct detection of the source and for identifying the sensor set that minimizes the expected distance between the real source and the estimated one

Determination of gaseous elemental mercury (GEM) emissions by a non-stationary static accumulation chamber. The case study of Portoscuso (South-West Sardinia)

This work describes the methodology based on a non­statonary statc accumulaton chamber used for measuring the GEM emissions at the soil­atmosphere interface in some residental and agricultural areas of the Portoscuso Municipality (South­West Sardinia). Afer a preliminary risk assessment of soil contaminaton, the investgated areas highlighted potental significant human health risks for volatlizaton pathways related to total Hg content in the soil. The aim of this study is to use the GEM emission rate to estmate indoor and outdoor human exposure according to the specific use of the areas. Acceptable GEM emissions (AGEM), i.e. maximum emissions associated with an acceptable human exposure and health risk, were defined accordingly and compared with measured ones. The measured GEM emissions probably consttute the sum of two contributons: • a real flux of GEM “through the soil­atmosphere interface”. This flux is originated by the presence of sources (both natural and/or related to potental contaminaton) in the first meters of depth and is regulated by mainly advectve mechanisms; • a component produced “at the soil­atmosphere interface”, as a response to the acton of UV radiaton on divalent Hg (II) in soil partcles. In this study the contributon of each of these two components has not been evaluated; however the main results showed, at the scale of the single sample representatve area (Thiessen polygon), few values (8 out of 163, about 5%) exceeding the AGEM values for the indoor scenario. These results are poorly indicatve of a real unacceptable risk, given their extremely punctual extent not representatve of a long­term human exposure. Conversely, GEM emissions for each macroarea showed a general compliance with acceptable thresholds emission (AGEM) computed for both outdoor and indoor scenarios. Further investgatons will be aimed at discriminatng the two components that originate the measured GEM flux values