Anti-Restriction Gene Homologs Are Highly Represented in Methicillin-Resistant and Multidrug-Resistant Staphylococcus aureus ST239 and ST398: Implications for Resistance Gene Acquisitions.

Multidrug resistance is commonly acquired by transferring DNA from one bacterium to another. However, the mechanisms that enhance the acquisitions of foreign genes are poorly understood, as well as the dynamics of their transmission between hosts in different environments. Here, genomic approaches were applied to evaluate the enrichment of the S. aureus chromosome with resistance traits in groups of genomes with or without anti-restriction genes and to analyze some evolutionary aspects of these acquisitions. Furthermore, the role played by an anti-restriction gene in improving multiresistance in MRSA was investigated by molecular cloning. A strong association was observed between the presence of anti-restriction gene homologs and patterns of multidrug resistance. Human isolates, mainly ST239-SCCmecIII, carry ardA-H1, and from animal sources, mainly CC398, carry ardA-H2. Increased DNA transfer was observed for clones that express the ardA-H1 allele, corroborating its role in promoting gene transfer. In addition, ardA-H1 was expressed in the dsDNA format in the BMB9393 strain. The evolution of successful multidrug-resistant MRSA lineages of the ST239 and ST398 was initiated not only by the entry of the mec cassette but also by the acquisition of anti-restriction gene homologs. Understanding the mechanisms that affect DNA transfer may provide new tools to control the spread of drug resistance.

Country data on AMR in Brazil in the context of community-acquired respiratory tract infections: links between antibiotic susceptibility, local and international antibiotic prescribing guidelines, access to medicine and clinical outcome.

BACKGROUND: Antimicrobial resistance (AMR) is one of the biggest threats to global public health. Selection of resistant bacteria is driven by inappropriate use of antibiotics, amongst other factors. COVID-19 may have exacerbated AMR due to unnecessary antibiotic prescribing. Country-level knowledge is needed to understand options for action. OBJECTIVES: To review the situation with respect to AMR in Brazil and initiatives addressing it. Identifying areas where more information is required will provide a call to action to minimize any further rises in AMR within Brazil and to improve patient outcomes. METHODS: National initiatives to address AMR, antibiotic use and prescribing in Brazil, and availability of susceptibility data, particularly for the key community-acquired respiratory tract infections (CA-RTI) pathogens Streptococcus pneumoniae and Haemophilus influenzae, were identified. National and international antibiotic prescribing guidelines for CA-RTIs (community-acquired pneumonia, acute otitis media and acute bacterial rhinosinusitis) commonly used locally were also reviewed, along with local antibiotic availability. CONCLUSIONS: In Brazil there have been some initiatives addressing AMR such as the National Action Plan for AMR, established in 2018. Antibiotic consumption in Brazil is high but a ban on over-the-counter sales of antibiotics has led to a decrease in consumption. Local antibiotic susceptibility testing needs to be increased and the Survey of Antibiotic Resistance (SOAR) study in Brazil will provide useful data for pathogens causing CA-RTIs. A more standardized inclusive approach in developing local guidelines, using up-to-date surveillance data of isolates from community-acquired infections in Brazil, could make guideline use more locally relevant for clinicians. This would pave the way for a higher level of appropriate antibiotic prescribing and improved adherence. This would, in turn, potentially limit AMR development and improve clinical outcomes for patients.

Antibiofilm effects of N,O-acetals derived from 2-amino-1,4-naphthoquinone are associated with downregulation of important global virulence regulators in methicillin-resistant Staphylococcus aureus.

Despite the existing antibiotics, antimicrobial resistance is a major challenge. Consequently, the development of new drugs remains in great demand. Quinones is part of a broad group of molecules that present antibacterial activity besides other biological properties. The main purpose of this study was to evaluate the antibiofilm activities of synthetic N,O-acetals derived from 2-amino-1,4-naphthoquinone [7a: 2-(methoxymethyl)-amino-1,4-naphthoquinone; 7b: 2-(ethoxymethyl)-amino-1,4-naphthoquinone; and 7c: 2-(propynyloxymethyl)-amino-1,4-naphthoquinone] against methicillin-resistant Staphylococcus aureus (MRSA). The derivatives 7b and 7c, specially 7b, caused strong impact on biofilm accumulation. This inhibition was linked to decreased expression of the genes fnbA, spa, hla and psmα3. More importantly, this downregulation was paralleled by the modulation of global virulence regulators. The substitution of 2-ethoxymethyl (7b) in comparison with 2-propynyloxymethyl (7c) enhanced sarA-agr inhibition, decreased fnbA transcripts (positively regulated by sarA) and strongly impaired biofilm accumulation. Indeed, 7b triggered intensive autolysis and was able to eliminate vancomycin-persistent cells. Consequently, 7b is a promising molecule displaying not only antimicrobial effects, but also antibiofilm and antipersistence activities. Therefore, 7b is a good candidate for further studies involving the development of novel and more rational antimicrobials able to act in chronic and recalcitrant infections, associated with biofilm formation.

Local Diversification of Methicillin- Resistant Staphylococcus aureus ST239 in South America After Its Rapid Worldwide Dissemination.

The global spread of specific clones of methicillin-resistant Staphylococcus aureus (MRSA) has become a major public health problem, and understanding the dynamics of geographical spread requires worldwide surveillance. Over the past 20 years, the ST239 lineage of MRSA has been recognized as an emerging clone across the globe, with detailed studies focusing on isolates from Europe and Asia. Less is known about this lineage in South America, and, particularly, Brazil where it was the predominant lineage of MRSA in the early 1990s to 2000s. To gain a better understanding about the introduction and spread of ST239 MRSA in Brazil we undertook a comparative phylogenomic analysis of ST239 genomes, adding seven completed, closed Brazilian genomes. Brazilian ST239 isolates grouped in a subtree with those from South American, and Western, romance-language-speaking, European countries, here designated the South American clade. After an initial worldwide radiation in the 1960s and 1970s, we estimate that ST239 began to spread in South America and Brazil in approximately 1988. This clone demonstrates specific genomic changes that are suggestive of local divergence and adaptational change including agrC single-nucleotide polymorphisms variants, and a distinct pattern of virulence-associated genes (mainly the presence of the chp and the absence of sea and sasX). A survey of a geographically and chronologically diverse set of 100 Brazilian ST239 isolates identified this virulence genotype as the predominant pattern in Brazil, and uncovered an unexpectedly high prevalence of agr-dysfunction (30%). ST239 isolates from Brazil also appear to have undergone transposon (IS256) insertions in or near global regulatory genes (agr and mgr) that likely led to rapid reprogramming of bacterial traits. In general, the overall pattern observed in phylogenomic analyses of ST239 is of a rapid initial global radiation, with subsequent local spread and adaptation in multiple different geographic locations. Most ST239 isolates harbor the ardA gene, which we show here to have in vivo anti-restriction activity. We hypothesize that this gene may have improved the ability of this lineage to acquire multiple resistance genes and distinct virulence-associated genes in each local context. The allopatric divergence pattern of ST239 also may suggest strong selective pressures for specific traits in different geographical locations.

The role of biofilms in persistent infections and factors involved in ica-independent biofilm development and gene regulation in Staphylococcus aureus.

Staphylococcus aureus biofilms represent a unique micro-environment that directly contribute to the bacterial fitness within hospital settings. The accumulation of this structure on implanted medical devices has frequently caused the development of persistent and chronic S. aureus-associated infections, which represent an important social and economic burden worldwide. ica-independent biofilms are composed of an assortment of bacterial products and modulated by a multifaceted and overlapping regulatory network; therefore, biofilm composition can vary among S. aureus strains. In the microniches formed by biofilms-produced by a number of bacterial species and composed by different structural components-drug refractory cell subpopulations with distinct physiological characteristics can emerge and result in therapeutic failures in patients with recalcitrant bacterial infections. In this review, we highlight the importance of biofilms in the development of persistence and chronicity in some S. aureus diseases, the main molecules associated with ica-independent biofilm development and the regulatory mechanisms that modulate ica-independent biofilm production, accumulation, and dispersion.

Inactivation of the Autolysis-Related Genes lrgB and yycI in Staphylococcus aureus Increases Cell Lysis-Dependent eDNA Release and Enhances Biofilm Development In Vitro and In Vivo.

Staphylococcus aureus ica-independent biofilms are multifactorial in nature, and various bacterial proteins have been associated with biofilm development, including fibronectin-binding proteins A and B, protein A, surface protein SasG, proteases, and some autolysins. The role of extracellular DNA (eDNA) has also been demonstrated in some S. aureus biofilms. Here, we constructed a Tn551 library, and the screening identified two genes that affected biofilm formation, lrgB and yycI. The repressive effect of both genes on the development of biofilm was also confirmed in knockout strains constructed by allelic recombination. In contrast, the superexpression of either lrgB or yycI by a cadmium-inducible promoter led to a decrease in biofilm accumulation. Indeed, a significant increase in the cell-lysis dependent eDNA release was detected when lrgB or yycI were inactivated, explaining the enhanced biofilm formed by these mutants. In fact, lrgB and yycI genes belong to distinct operons that repress bacterial autolysis through very different mechanisms. LrgB is associated with the synthesis of phage holin/anti-holin analogues, while YycI participates in the activation/repression of the two-component system YycGF (WalKR). Our in vivo data suggest that autolysins activation lead to increased bacterial virulence in the foreign body animal model since a higher number of attached cells was recovered from the implanted catheters inoculated with lrgB or yycI knockout mutants.

First report in South America of companion animal colonization by the USA1100 clone of community-acquired meticillin-resistant Staphylococcus aureus (ST30) and by the European clone of methicillin-resistant Staphylococcus pseudintermedius (ST71).

BACKGROUND: Methicillin-resistant staphylococci can colonize and cause diseases in companion animals. Unfortunately, few molecular studies have been carried out in Brazil and other countries with the aim of characterizing these isolates. Consequently, little is known about the potential role of companion animals in transmitting these resistant bacteria to humans. In this work we searched for mecA gene among Staphylococcus isolates obtained from nasal microbiota of 130 healthy dogs and cats attended in a veterinary clinic located in the west region of Rio de Janeiro. The isolates recovered were identified to the species level and characterized using molecular tools. RESULTS: A community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) isolate related to USA1100 (Southwest Pacific clone) and susceptible to all non-ß-lactams was detected in a cat (1.7%, 1/60). Another coagulase-positive isolate harboring mecA was recovered from a dog (1.4%, 1/70) and identified as Staphylococcus pseudintermedius (MRSP) related to the European clone (ST71). The two isolates of Staphylococcus conhii subsp. urealyticus (1.4%, 1/70 dogs and 1.7%, 1/60 cats), similarly to the MRSP isolate, also presented high-level multiresistance. The majority of the methicillin-resistant coagulase-negative staphylococci recovered were Staphylococcus saprophyticus (5.7%, 4/70 dogs and 6.7%, 4/60 cats) and all clustered into the same PFGE type. CONCLUSIONS: This work demonstrates that mecA-harboring Staphylococcus isolates are common members of the nasal microbiota of the healthy companion animals studied (9.2%, 12/130 animals), including some high-level multiresistant isolates of S. pseudintermedius and S. conhii subsp. urealyticus. The detection, for the first time in South America, of USA1100-related CA-MRSA and of ST71 MRSP (European clone), colonizing companion animals, is of concern. Both S. pseudintermedius and S. aureus are important agents of infections for animals. The USA1100 CA-MRSA is a causative of severe and disseminated diseases in healthy children and adults. Additionally, MRSP is a nosocomial pathogen in veterinarian settings. It had already been demonstrated that the virulent ST71 MRSP is geographically spread over Europe and USA, with potential for zoonotic infections.

Complete Genome Sequence of a Variant of the Methicillin-Resistant Staphylococcus aureus ST239 Lineage, Strain BMB9393, Displaying Superior Ability To Accumulate ica-Independent Biofilm.

Biofilm is considered an important virulence factor in nosocomial infections. Herein, we report the complete genome sequence of a variant of methicillin-resistant Staphylococcus aureus, strain BMB9393, which is highly disseminated in Brazil. This strain belongs to the lineage ST239 and displays increased ability to accumulate ica-independent biofilm and to invade human epithelial cells.