Nanoplexes of ZnS quantum dot-poly-l-lysine/iron oxide nanoparticle-carboxymethylcellulose for photocatalytic degradation of dyes and antibacterial activity in wastewater treatment.

The contamination and pollution of wastewater with a wide diversity of chemical, microbiological, and hazardous substances is a field of raising environmental concern. In this study, we developed, for the first time, new hybrid multifunctional nanoplexes composed of ZnS semiconductor quantum dots (ZnS QDs) chemically biofunctionalized with epsilon-poly-l-lysine (ɛPL) and coupled with magnetic iron oxide nanoparticles (MION, Fe3O4) stabilized by carboxymethylcellulose (CMC) for the photodegradation (ZnS) of organic molecules and antibacterial activity (ɛPL) with a potential of recovery by an external magnetic field (Fe3O4). These nanosystems, which were synthesized entirely through a green aqueous process, were comprehensively characterized regarding their physicochemical properties combined with spectroscopic and morphological features. The results demonstrated that supramolecular colloidal nanoplexes were formed owing to the strong cationic/anionic electrostatic interactions between the biomacromolecule capping ligands of the two nanoconjugates (i.e., polypeptide in ZnS@ɛPL and polysaccharide in Fe3O4@CMC). Moreover, these nanosystems showed photocatalytic degradation of methylene blue (MB) used as a model dye pollutant in water. Besides MB, methyl orange, congo red, and rhodamine dyes were also tested for selectivity investigation of the photodegradation by the nanoplexes. The antibacterial activity ascribed to the ɛPL biomolecule was confirmed against Gram-positive and Gram-negative bacteria, including drug-resistance field strains. Hence, it is envisioned that these novel green nanoplexes offer a new avenue of alternatives to be employed for reducing organic pollutants and inactivating pathogenic bacteria in water and wastewater treatment, benefiting from easy magnetic recovery.

Virulence factors and antimicrobial resistance in Staphylococcus aureus isolated from bovine mastitis in Brazil.

This study aimed to evaluate virulence factors and genetic markers of antimicrobial resistance in 400 Staphylococcus aureus strains isolated from bovine mastitis in four Brazilian states, as well as to assess the association between these characteristics and field information. Virulence factors and drug resistance genes were identified by PCR screening. Biofilm-forming and hemolytic phenotype were detected using Congo red Tryptic Soy Broth and defibrinated sheep blood agar, respectively. Of all isolates, 83.5% were biofilm-forming and 98.5% strains exhibited biofilm gene icaAD, and a significant association between phenotype and genotype for biofilm was observed (P = 0.0005). Hemolysin genes were observed in 82.85% (hla+hlb+), 16.5% (hla+) and 0.75% (hlb+) isolates, whereas the hemolytic phenotype exhibited was complete and incomplete hemolysis in 64.25%, complete in 28.25%, incomplete in 4.75%, and negative in 2.75% of the strains. Virulence factors genes luk, seb, sec, sed, and tst were observed in 3.5%, 0.5%, 1%, 0.25%, and 0.74% isolates, respectively. The gene blaZ was detected in 82.03% of penicillin-resistant isolates, whereas tetK and aac(6')-Ie-aph(2')-Ia were observed in 33.87% and 45.15% of the tetracycline and aminoglycosides-resistant isolates, respectively. Fluoroquinolone resistance gene mepA was detected for the first time in S. aureus from bovine mastitis. Resistance genes tetM (3.22%), tetL (1.61%), ermA (14.29%), ermB (14.29%), ermC (33.3%), ermT (9.52%), ermY (4.76%), msrA (9.52%), and mphC (9.52%) were also detected among resistant isolates. No association between virulence factors or antimicrobial-resistant genes and year of isolation, geographic origin, or antimicrobial resistance profile was observed. Our results showed that S. aureus strains isolated from bovine mastitis in the four Brazilian states sampled are mainly biofilm-forming and hemolytic, whereas virulence genes associated with enterotoxins, luk and tst, were less frequently observed. Moreover, a wide variety of resistance genes that confer resistance to almost all classes of antimicrobial agents approved for use in animals and humans were found. Overall, the data point to a great pathogenic potential of S. aureus associated with bovine mastitis and to the non-negligible risks to public health of staphylococcal infections from animal origin.

Risk factors for high bulk milk somatic cell counts in dairy herds from Campos das Vertentes region, Minas Gerais State, Brazil: a case-control study / Fatores de risco para contagens elevadas de células somáticas no leite de tanque em rebanhos de bovinos da região de Campos das Vertentes, Minas Gerais, Brasil: um estudo de caso-controle

High bulk milk somatic cell counts (BMSCC) are indicative of failures related to the control of mastitis in the herd, which compromises the quality of the milk and generates great losses for the producers and for the industry. A case-control study was carried out in dairy herds in the Campos das Vertentes region, Minas Gerais State, Brazil, in order to contribute to the knowledge of the risk factors involved with elevated BMSCC. The study involved 46 dairy herds, of which 30 were considered cases (BMSCC ≥700,000 cells/mL of milk) and 16 control farms (BMSCC ≤200,000 cells/mL of milk). Sixteen qualitative variables and four quantitative variables were analyzed. The results showed that the risk factors for BMSCC ≥700,000 cells/mL were the presence of Staphylococcus aureus and Streptococcus agalactiae pathogens in bulk milk, non-use of pre and post-dipping, non-use of disposable paper towel for drying of mammary glands, non-monitoring of mastitis in the herd by means of California Mastitis Test (CMT) or individual somatic cell counts (SCC), non-implementation of the milking line and therapy of dry cows and failures in hygiene of teats and udders before milking. Moderate correlations were also observed between the elevation of BMSCC and counts of S. aureus and BMSCC and counts S. agalactiae in bulk milk, and a moderate correlation between S. aureus and S. agalactiae counts in bulk milk. Failures with regard to the maintenance and use of milking equipment, including manual pressure application in milking assemblies, unregulated milking vacuum pressure, and vacuum loss during milking, and maintenance failures of the milking machine and bulk milk tank were also pointed out as important risk factors of BMSCC elevation. The results of this study provided subsidies for the elaboration of more effective programs for mastitis control and improvement of raw milk quality, reducing the losses caused by the disease to producers and industry.(AU)

Altas contagens de células somáticas no leite do tanque (CCSt) são indicativas de falhas relacionadas com o controle da mastite no rebanho, o que compromete a qualidade do leite e gera grandes perdas para os produtores e para a indústria. Visando identificar os fatores de risco envolvidos com a CCSt elevada, foi realizado um estudo de caso-controle em rebanhos bovinos leiteiros da região de Campos das Vertentes, em Minas Gerais. O estudo envolveu 46 propriedades, das quais 30 foram consideradas casos (CCSt ≥700.000 cels/mL de leite) e 16 propriedades controles (CCSt ≤200.000 cels/mL de leite). Foram analisadas 16 variáveis qualitativas e quatro variáveis quantitativas. Os resultados demonstraram que os fatores de risco para valores de CCSt ≥700.000 cels/mL de leite foram a presença dos patógenos Staphylococcus aureus e Streptococcus agalactiae, não utilização do pré e de pós-dipping, não utilização de papel toalha descartável para a secagem dos tetos, não monitoramento da mastite por meio do California Mastitis Test (CMT) ou CCS individual, não implementação da linha de ordenha e da terapia de vacas secas e falhas na higiene de tetos e de úbere antes da ordenha. Também se observaram correlações moderadas entre a CCSt e as contagens de S. aureus e entre CCSt e as contagens de S. agalactiae, e correlação moderada entre as contagens de S. aureus e de S. agalactiae no leite do tanque. Falhas com relação à manutenção e utilização dos equipamentos de ordenha, aplicação de pressão manual nos conjuntos da ordenha, pressão de vácuo da ordenha desregulada, perda de vácuo durante a ordenha e falhas de manutenção da ordenhadeira e do tanque de expansão foram também apontadas como fatores de risco para elevação da CCSt. Os resultados deste estudo possibilitaram identificar fatores de risco importantes para contagens elevadas de CCSt que poderão fornecer subsídios para a elaboração de programas de controle mais efetivos para a mastite e para a melhoria da qualidade do leite, mitigando o impacto que a doença causa para os produtores e para a indústria.(AU)

Staphylococcus aureus and Streptococcus agalactiae: prevalence, resistance to antimicrobials, and their relationship with the milk quality of dairy cattle herds in Minas Gerais state, Brazil / Staphylococcus aureus e Streptococcus agalactiae: prevalência, resistência aos antimicrobianos e suas relações com a qualidade do leite em rebanhos leiteiros de Minas Gerais, Brasil

Bovine mastitis is the most frequent disease worldwide in dairy herds, causing high economic losses to producers and industry, as well as having implications for public health due to the zoonotic potential of some agents involved in its etiology and the increased risk of antimicrobial residues in milk and its derivatives. Considering the multifactorial aspect of this disease, knowledge of the agents involved in its etiology and their antimicrobial susceptibility profiles is very important. This study was conducted with 306 dairy herds from the Campo das Vertentes region, located in the south of Minas Gerais state, whose owners were milk suppliers to a dairy in the same region. The study involved approximately 34,000 dairy cows and covered an area of approximately 12,564 km2. In these herds, prevalence rates of Staphylococcus aureus and Streptococcus agalactiae and their relationship with bulk milk somatic cell counts (BMSCC), total bacterial counts (TBC), and daily production were evaluated. In addition, analyses of resistance of these pathogens to the antimicrobials most commonly used in the treatment of mastitis in dairy herds were performed. Microbiological analyses of milk samples from collect from bulk milk tanks were performed aiming to evaluate the prevalence of S. aureus and S. agalactiae. For these proposes, the modified Baird-Parker Agar medium was used for detection of S. aureus and the modified Edwards Agar medium, enriched with 5% defibrinated sheep blood, was used for detection of S. agalactiae. The disc diffusion technique was applied to evaluate antimicrobial resistance. Results show high prevalence rates of S. aureus (70.3%) and S. agalactiae (67.0%) in the dairy farms studied, with 47.71% of the herds showing both pathogens. Associations between BMSCC and the presence of pathogens S. aureus and S. agalactiae and between TBC and the presence of S. agalactiae were observed, demonstrating the influence of these pathogens in milk quality. No variation was observed in the distribution of S. aureus and S. agalactiae in the different strata of daily production. High levels of resistance and multi-resistance were observed among the pathogens S. aureus and S. agalactiae. The results indicate the need for more effective control measures for mastitis caused by S. aureus and S. agalactiae in the dairy herds of the region studied and more judicious use of antimicrobials in order to reduce the problem of resistance to them.(AU)

A mastite bovina é a doença de maior frequência em rebanhos leiteiros em nível mundial, acarretando grandes prejuízos econômicos aos produtores e à indústria. Além disso, esta enfermidade tem implicações na saúde pública, devido ao potencial zoonótico de alguns agentes envolvidos em sua etiologia e por aumentar os riscos de resíduos de antimicrobianos no leite e derivados. Considerando o aspecto multifatorial da mastite bovina, o conhecimento dos agentes envolvidos em sua etiologia e os perfis de suscetibilidade aos antibióticos é de suma importância. O estudo envolveu 306 fazendas de leite da região de Campo das Vertentes, localizada no sul de Minas Gerais, cujos proprietários eram fornecedores de leite para um laticínio da região, totalizando aproximadamente 34.000 animais e abrangendo uma área aproximada 12.564 km2. Nestes rebanhos, avaliaram-se a prevalência de Staphylococcus aureus e Streptococcus agalactiae e a relação destes agentes com os índices de contagem de células somáticas do leite do tanque de expansão (CCSt), contagem bacteriana total (CBT) e produção diária. Analisou-se também a resistência destes patógenos aos antimicrobianos mais comumente utilizados no tratamento da mastite em rebanhos leiteiros. Análises microbiológicas de amostras de leite dos tanques de expansão foram realizadas para se determinar as prevalências dos patógenos S. aureus e S. agalactiae. Para a detecção de S. aureus, utilizou-se o meio seletivo Ágar Baird-Parker modificado e para a detecção de S. agalactiae, o meio seletivo Ágar Edwards modificado, enriquecido com 5% de sangue ovino desfibrinado. Foi utilizada a técnica de difusão em discos para a avaliação de resistência aos antimicrobianos. Os resultados apontaram altas prevalências de S. aureus (70,3%) e de S. agalactiae (67,0%), com 47,71% dos rebanhos examinados apresentando ambos os agentes. Verificaram-se associações entre a CCSt e a presença dos patógenos S. aureus e S. agalactiae, e também entre a CBT e a presença de S. agalactiae, demonstrando a interferência negativa destes patógenos nestes quesitos de qualidade. Não se observaram variações nas distribuições dos patógenos S. aureus e nem S. agalactiae em função da produção diária das propriedades estudadas. Níveis elevados de resistência e de multirresistência foram observados para ambos os agentes. Os resultados apontam a necessidade de medidas mais efetivas de controle para S. aureus e S. agalactiae nos rebanhos da região estudada e do uso mais criterioso dos antimicrobianos, visando minimizar o problema da resistência aos mesmos.(AU)

Molecular epidemiology of Streptococcus agalactiae isolated from mastitis in Brazilian dairy herds.

Streptococcus agalactiae is one of the most common pathogens leading to mastitis in dairy herds worldwide; consequently, the pathogen causes major economic losses for affected farmers. In this study, multilocus sequence typing (MLST), genotypic capsular typing by multiplex polymerase chain reaction (PCR), and virulence gene detection were performed to address the molecular epidemiology of 59 bovine (mastitis) S. agalactiae isolates from 36 dairy farms located in the largest milk-producing mesoregions in Brazil (Minas Gerais, São Paulo, Paraná, and Pernambuco). We screened for the virulence genes bac, bca, bibA, cfb, hylB, fbsA, fbsB, PI-1, PI-2a, and PI-2b, which are associated with adhesion, invasion, tissue damage, and/or immune evasion. Furthermore, five capsular types were identified (Ia, Ib, II, III, and IV), and a few isolates were classified as non-typeable (NT). MLST revealed the following eight sequence types (STs): ST-61, ST-67, ST-103, ST-146, ST-226, ST-314, and ST-570, which were clustered in five clonal complexes (CC64, CC67, CC103, CC17, and CC314), and one singleton, ST-91. Among the virulence genes screened in this study, PI-2b, fbsB, cfb, and hylB appear to be the most important during mastitis development in cattle. Collectively, these results establish the molecular epidemiology of S. agalactiae isolated from cows in Brazilian herds. We believe that the data presented here provide a foundation for future research aimed at developing and implementing new preventative and treatment options for mastitis caused by S. agalactiae.