Assessing the relationship between organic farming practices and microbiological characteristics of organic lettuce varieties (Lactuca sativa L.) grown in Sao Paulo, Brazil

AIMS

This study aimed to gather information on farming practices employed in organic lettuce fields in Sao Paulo, Brazil and associate these practices with the microbiological characteristics of the products.

METHODS AND RESULTS

Practices were surveyed using a questionnaire applied in ten farms, where 200 heads of lettuce were collected and submitted to enumeration of total coliforms and generic Escherichia coli and tested for Salmonella spp. using culture and molecular (qPCR) methods. Based on the responses, the farms could be clustered in two groups: group 1, comprised by six farms, where chicken manure was used as fertilizer in most of them and the composting process was not performed on site; and group 2, comprised by four farms, where other types of fertilizer were used, and the composting process was performed on site. Generic E. coli was detected in 56 (28%) samples, with an average of 1·1 ± 0·7 log MPN per g. Salmonella DNA was detected in two (1%) samples by qPCR.

CONCLUSIONS

The prevalence and bacterial loads of generic E. coli, and the occurrence of Salmonella, even at low populations undetectable by conventional culture methods, highlight the need for control measures during farming practices to reduce microbial contamination and risks of foodborne illnesses. These measures include the use of properly composted manure and appropriate washing procedures for leafy vegetables before consumption.

SIGNIFICANCE AND IMPACT OF THE STUDY

The obtained data contribute to a better understanding of the farming practices of organically grown lettuces in Sao Paulo, Brazil.

Topical application of probiotics in skin: adhesion, antimicrobial and antibiofilm in vitro assays

AIMS

When skin dysbiosis occurs as a result of skin disorders, probiotics can act as modulators, restoring microbial balance. Several properties of selected probiotics were evaluated so that their topical application could be considered.

METHODS AND RESULTS

Adhesion, antimicrobial, quorum sensing and antibiofilm assays were carried out with several probiotic strains and tested against selected skin pathogens. All tested strains displayed significant adhesion to keratin. All lactobacilli with the exception of Lactobacillus delbrueckii, showed antimicrobial activity against skin pathogens, mainly due to organic acid production. Most of them also prevented biofilm formation, but only Propioniferax innocua was able to break down mature biofilms.

CONCLUSIONS

This study demonstrates that although all tested probiotics adhered to human keratin, they showed limited ability to prevent adhesion of some potential skin pathogens. Most of the tested probiotics successfully prevented biofilm formation, suggesting that they may be successfully used in the future as a complement to conventional therapies in the treatment of a range of skin disorders.

SIGNIFICANCE AND IMPACT OF STUDY

The topically used probiotics may be a natural, targeted treatment approach to several skin disorders and a complement to conventional therapies which present many undesirable side effects.

Transmission of wireless neural signals through a 0.18 µm CMOS low-power amplifier

In the field of Brain Machine Interfaces (BMI) researchers still are not able to produce clinically viable solutions that meet the requirements of long-term operation without the use of wires or batteries. Another problem is neural compatibility with the electrode probes. One of the possible ways of approaching these problems is the use of semiconductor biocompatible materials (silicon carbide) combined with an integrated circuit designed to operate with low power consumption. This paper describes a low-power neural signal amplifier chip, named Cortex, fabricated using 0.18 μm CMOS process technology with all electronics integrated in an area of 0.40 mm(2). The chip has 4 channels, total power consumption of only 144 μW, and is impedance matched to silicon carbide biocompatible electrodes.

Using exact relations in damage-spreading simulations: the Baxter line of the two-dimensional Ashkin-Teller model

The nearest-neighbor-interaction ferromagnetic Ashkin-Teller model is investigated on a square lattice through a powerful computational method for dealing with correlation functions in magnetic systems. This technique, which is based on damage-spreading numerical simulations, makes use of exact relations involving special kinds of damage and correlation functions, as well as the corresponding order parameters of the model. The computation of correlation functions, which represents usually a hard task in standard Monte Carlo simulations, due to large fluctuations, turns out to be much simpler within the present approach. We concentrate our analysis along the Baxter line, well known for its continuously varying critical exponents; seven different points along this line are investigated. The critical exponents associated with correlation functions along the Baxter line are successfully evaluated, by means of numerical methods, within damage-spreading simulations. The efficiency of this method is confirmed through precise estimates of the critical exponents associated with the order parameters (magnetization and polarization), as well as with their corresponding correlation functions, in spite of the small lattice sizes considered.

Damage-spreading simulations through exact relations for the two-dimensional Potts ferromagnet

A powerful computational method for dealing with correlation functions in magnetic systems, based on damage-spreading simulations, is reviewed and tested, by investigating the q-state Potts ferromagnet, on a square lattice, at criticality. Exact relations involving special kinds of damage and the spin-spin correlation function, as well as the magnetization, are used. The efficiency of the method arises with a significant reduction of the finite-size effects, with respect to conventional Monte Carlo simulations. Correlation functions, which represent usually a hard task within this latter procedure, appear to be much more easily estimated through the present damage-spreading simulations. The effectiveness of the technique is illustrated by an accurate estimate of the exponent eta, of the spin-spin correlation function, for q=2, 3, and 4, with rather small lattice sizes. In the cases q > or = 5, an analysis of the magnetization is consistent with the well-known first-order phase transition.

Chronic rapid atrial pacing to maintain atrial fibrillation: use to permit control of ventricular rate in order to treat tachycardia induced cardiomyopathy

LR was a patient, followed over a 16-year period, who presented with an atrial tachycardia which was initially intermittent, but became incessant. Neither the atrial tachycardia nor the associated rapid ventricular response rate could be treated successfully with available drug therapy, resulting in a dilated cardiomyopathy and New York Heart Association (NYHA) class III-IV congestive heart failure. Acute induction of atrial fibrillation with rapid atrial pacing demonstrated that the associated ventricular rate could be satisfactorily slowed with digitalis therapy. Initially, short bursts from an implanted, radiofrequency controlled, patient activated pacemaker programmed to a rate of 600 bpm and connected to a permanent endocardial atrial J lead successfully interrupted the tachycardia and precipitated atrial fibrillation. Over a period of 3 months, this therapy changed the patient's heart failure to NYHA class II status. Subsequently, precipitation of atrial fibrillation with this technique failed, resulting in return to NYHA class III-IV congestive heart failure. Therefore, a custom-designed, high rate, rate-programmable pacemaker was implanted to pace the atria rapidly and continuously to maintain atrial fibrillation. A pacing rate of 375 bpm plus digoxin slowed the ventricular rate to 70-80 bpm, with stabilization of the congestive heart failure to NYHA class II. The pacemaker generator was replaced 6 months later, and after another 5 months, pacing was discontinued. The patient's subsequent rhythm remained stable atrial fibrillation with clinically successful control of both the ventricular rate and heart failure (NYHA class II) until the patient's death 72 months later. This unique case demonstrates another form of chronic therapy which, in selected cases, can be used for the long term control of rapid ventricular response rates to supraventricular arrhythmia.