ABSTRACT
Fifty-two Staphylococcus aureus recovered from papillary ostium and milk samples collected from cows with subclinical mastitis and milking environments in three small dairy herds located in southeastern Brazil were subjected to PCR identification based on the thermonuclease (nuc) gene. All the strains were submitted to in vitro antimicrobial susceptibility testing, and we investigated the sequence types (STs), agr groups (I-IV), virulence genes encoding for Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs), biofilm-associated proteins, bi-component toxins, pyrogenic toxin superantigens, and enterotoxins. Screening for oxacillin resistance (2-6 µg/ml oxacillin), beta-lactamase activity assays, and PCR for the mecA/mecC genes detected 26 methicillin-susceptible S. aureus(MSSA) and 26 mec-independent oxacillin-nonsusceptible S. aureus (MIONSA). While MSSA isolates were found to be susceptible to all antimicrobial agents tested, or only resistant to penicillin and ampicillin, MIONSA isolates were multidrug-resistant. ST126-agr group II MSSA isolates were prevalent in milk (n=14) and carried a broad set of virulence genes (clfA, clfB, eno, fnbA, fiB, icaA, icaD, lukED, hla, and hlb), as well as the ST126-agr group II MIONSA isolated from milking liners (n=1), which also carried the eta gene. ST1-agr group III MIONSA isolates (n=4) were found in papillary ostium and milk, but most MIONSA isolates (n=21), which were identified in both papillary ostium and milking liners, were agr-negative and assigned to ST126. The agr-negative and agr group III lineages showed a low potential for virulence. Studies on the characterization of bovine-associated MSSA/MIONSA are essential to reduce S. aureus mastitis to prevent economic losses in dairy production and also to monitor the zoonotic potential of these pathogens associated with invasive infections and treatment failures in healthcare.
Cinquenta e dois isolados de Staphylococcus aureus obtidos de amostras colhidas do óstio papilar, do leite de vacas com mastite subclínica e do ambiente de ordenha em três fazendas de rebanhos leiteiros localizadas no sudeste do Brasil foram identificados por PCR para o gene da termonuclease (nuc). Todos os isolados foram testados para sensibilidade a antimicrobianos e foram investigados os sequence types (STs), grupos agr (I-IV) e genes de virulência que codificam Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs), proteínas associadas a biofilme, toxinas bi-componentes, toxinas pirogênicas com propriedades de superantígenos e enterotoxinas. Triagem para detecção de resistência à oxacilina (2-6 µg/ml oxacilina), ensaios de atividade de enzimas beta-lactamases e PCR para os genes mecA/mecC detectaram 26 estirpes de S. aureus sensíveis à meticilina (methicillin-susceptible S. aureus, MSSA) e 26 estirpes de S. aureus mec-negativas não sensíveis à meticilina (mec-independent oxacillin-nonsusceptible S. aureus, MIONSA). Enquanto os isolados MSSA foram sensíveis a todos os agentes antimicrobianos testados, ou apenas resistentes à penicilina e ampicilina, os isolados MIONSA foram multirresistentes. MSSA ST126-agr grupo II foram prevalentes no leite (n= 14) e apresentaram um amplo conjunto de genes de virulência (clfA, clfB, eno, fnbA, fiB, icaA, icaD, lukED, hla e hlb), assim como o isolado MIONSA ST126-agr grupo II proveniente de um insuflador (n= 1), o qual também apresentou o gene eta. MIONSA ST1-agr grupo III (n= 4) foram identificados no óstio papilar e leite, mas a maioria dos isolados MIONSA (n= 21), encontrados em óstios papilares e insufladores, foram agr-negativos e pertenceram ao ST126. As linhagens agr-negativas e agr grupo III apresentaram baixo potencial de virulência. Estudos sobre a caracterização de MSSA/MIONSA associados a bovinos são essenciais para a redução da mastite causada por S. aureus e de perdas econômicas na produção leiteira e, também, para o monitoramento do potencial zoonótico desses patógenos associados a infecções invasivas e falhas de tratamento em ambientes hospitalares.
Subject(s)
Animals , Female , Cattle , Staphylococcus aureus/isolation & purification , Mastitis, Bovine/microbiology , Anti-Bacterial Agents/pharmacology , Staphylococcus aureus/drug effects , Staphylococcus aureus/genetics , Virulence , Microbial Sensitivity Tests , Polymerase Chain ReactionABSTRACT
BACKGROUND Evolutionary changes in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) include indels in non-structural, structural, and accessory open reading frames (ORFs) or genes. OBJECTIVES We track indels in accessory ORFs to infer evolutionary gene patterns and epidemiological links between outbreaks. METHODS Genomes from Coronavirus disease 2019 (COVID-19) case-patients were Illumina sequenced using ARTIC_V3. The assembled genomes were analysed to detect substitutions and indels. FINDINGS We reported the emergence and spread of a unique 4-nucleotide deletion in the accessory ORF6, an interesting gene with immune modulation activity. The deletion in ORF6 removes one repeat unit of a two 4-nucleotide repeat, which shows that directly repeated sequences in the SARS-CoV-2 genome are associated with indels, even outside the context of extended repeat regions. The 4-nucleotide deletion produces a frameshifting change that results in a protein with two inserted amino acids, increasing the coding information of this accessory ORF. Epidemiological and genomic data indicate that the deletion variant has a single common ancestor and was initially detected in a health care outbreak and later in other COVID-19 cases, establishing a transmission cluster in the Uruguayan population. MAIN CONCLUSIONS Our findings provide evidence for the origin and spread of deletion variants and emphasise indels' importance in epidemiological studies, including differentiating consecutive outbreaks occurring in the same health facility.
ABSTRACT
Accessory gene regulator (agr)-mediated quorum sensing system plays a crucial role in staphylococcal aureus (S.aureus) pathogenesis.It upregulates secreted virulence factors and downregulates cell surface proteins,thereby influencing invasiveness of S.aureus and cell dispersal from biofilms.S.aureus can be divided into four groups according to the polymorphism in the sequence of agr system and of its corresponding receptor.Auto-inducing peptide (AIP) can activate the agr locus in the same group,but mutually inhibit agr locus from different groups.Recent researches have demonstrated that agr dysfunction is common among S.aureus isolates.Certain agr classes and agr-defective strains have been associated with specific clonal complexes and a variety of diseases,influencing the courses of infections and the antibiotic resistance.In this paper,the effects of different agr types and dysfunctional agr on the virulence,antibiotic resistance and biofilm formation of S.aureus were reviewed.
ABSTRACT
Accessory gene regulator(agr)-mediated quorum sensing system plays a crucial role in staphylococcal aureus(S.aureus) pathogenesis.It upregulates secreted virulence factors and downregulates cell surface proteins, thereby influencing invasiveness of S. aureus and cell dispersal from biofilms.S.aureus can be divided into four groups according to the polymorphism in the sequence of agr system and of its corresponding receptor.Auto-inducing peptide(AIP)can activate the agr locus in the same group, but mutually inhibit agr locus from different groups.Recent researches have demonstrated that agr dysfunction is common among S. aureus isolates.Certain agr classes and agr-defective strains have been associated with specific clonal complexes and a variety of diseases, influencing the courses of infections and the antibiotic resistance.In this paper, the effects of different agr types and dysfunctional agr on the virulence, antibiotic resistance and biofilm formation of S. aureus were reviewed.
ABSTRACT
Objective: To investigate the effect of accessory gene regulator C (agr C) specific binding peptides (named N1) on the biofilm formation of Staphylococcus epidermidis on the surface of polyvinyl chloride (PVC) materials in vitro. Methods: Firstly, the two strains (ATCC35984, ATCC12228) were cultured with N1 at concentrations of 100, 200, 400, 800, and 1 600 μg/mL, respectively. The control group was cultured with agrC specific binding unrelated peptides (named N0) at the same concentrations and the absorbance ( A) value was measured after 24 hours to determine the optimal bacteriostatic concentration of N1. The two strains were cultured with N1 and N0 of the optimal concentration, respectively. The A values were measured at 6, 12, 18, 24, 30, and 48 hours to observe the effect of N1 on the biofilm formation ability of Staphylococcus epidermidis. On this basis, the surface structure of the biofilm on the surface of PVC material was observed by scanning electron microscopy after 6, 12, 18, 24, and 30 hours of incubation with PVC material sheet. The thickness of the biofilm was observed by laser confocal microscopy after 6, 12, 18, and 24 hours of incubation with ATCC35984 strain. Results: The optimal bacteriostatic concentration of N1 was 800 μg/mL. ATCC 12228 strain did not form obvious biofilm after being cultured with N1 and N0. When ATCC35984 strain was cultured with N1 and N0 for 12 hours, the difference in biofilm formation ability between groups N1 and N0 was statistically significant ( P0.05). Scanning electron microscopy examination showed that mature biofilm structure was observed in ATCC35984 strain and was not observed in ATCC12228 strain. Laser confocal microscopy observation showed that the number of bacteria in the group N1 was significantly lower than that in the group N0 at 12 hours, and the most of bacteria were dead bacteria. There was no significant difference in the number of bacteria at 6, 18, and 24 hours, and the most of them were live bacteria. The biofilm thickness of group N1 was significantly lower than that of group N0 at 12 and 18 hours ( P<0.05). Conclusion: The intensity of N1 inhibiting the formation of Staphylococcus epidermidis biofilm is dose-dependent. During the aggregation period, N1 can inhibit the biofilm formation by hindering the bacterial growth and aggregation. The inhibition effect on mature biofilm is not obvious.
ABSTRACT
Staphylococcus aureus continues to be a major pathogen in both community and healthcare associated infections.The pathogenicity of staphylococcus aureus is a complex process involving a variety of extracellular and cell wall components that are coordinately expressed during different stages of infection.Accessory gene regulator (agr)-mediated quorum sensing plays a major role in staphylococcal pathogenesis.However,agr dysfunction strains exist extensively in staphylococcus aureus clinical isolates.This review will mainly focus on the influence of agr dysfunction on staphylococcus aureus biofilm formation,clinical course and outcome of infectious diseases,and antibiotic resistance.
ABSTRACT
The formation of Staphylococcus epidermidis biofilm on the surface of medical biomaterials may resist the antibiotics treatment and cause chronic infection,which has become a research focus in recent years.Multiple genes constitute complex regulatory network which affect the biofilm formation,and play different roles in the different stages of biofilm formation.Accessory gene regulator (agr) is one of the most important genes in the process of biofilm formation.The process of bacterial biofilm formation,research status of regulation mechanism of agr system and its related genes in the formation of biofilm are reviewed,to provide reference of using agr as a target for the treatment of staphylococcus epidermidis biofilm related infections.