Methicillin/Oxacillin-resistant Staphylococcus aureus as a hospital and public health threat in Brazil

Staphylococcus aureus: Dynamics of pathogenicity and antimicrobial-resistance in hospital and community environments - Comprehensive overview

This study reviews Staphylococcus aureus, a significant pathogen in both hospital and community-acquired infections, addressing its epidemiology, pathogenesis, and antimicrobial resistance. It highlights virulence mechanisms, such as adhesion factors, toxins, enzymes, and biofilms, which contribute to survival and immune evasion. The spread of resistance occurs through the transfer of mobile genetic elements like SCCmec and genetic mutations. The analysis also compares hospital and community strains, including multidrug-resistant lineages like MRSA, VISA, and VRSA. The study concludes that S. aureus presents a major public health challenge, requiring new therapeutic approaches and preventive strategies.

Genomic Analysis of a Community-Acquired Methicillin-Resistant Staphylococcus aureus Sequence Type 1 Associated with Caprine Mastitis

This study aimed to investigate the genomic and epidemiological features of a methicillin-resistant Staphylococcus aureus sequence type 1 (MRSA ST1) strain associated with caprine subclinical mastitis. An S. aureus strain was isolated from goat's milk with subclinical mastitis in Paraiba, Northeastern Brazil, by means of aseptic procedures and tested for antimicrobial susceptibility using the disk-diffusion method. Whole genome sequencing was performed using the Illumina MiSeq platform. After genome assembly and annotation, in silico analyses, including multilocus sequence typing (MLST), antimicrobial resistance and stress-response genes, virulence factors, and plasmids detection were performed. A comparative SNP-based phylogenetic analysis was performed using publicly available MRSA genomes. The strain showed phenotypic resistance to cefoxitin, penicillin, and tetracycline and was identified as sequence type 1 (ST1) and spa type 128 (t128). It harbored the SCCmec type IVa (2B), as well as the lukF-PV and lukS-PV genes. The strain was phylogenetically related to six community-acquired MRSA isolates (CA-MRSA) strains associated with human clinical disease in North America, Europe, and Australia. This is the first report of a CA-MRSA strain associated with milk in the Americas. The structural and epidemiologic features reported in the MRSA ST1 carrying a mecA-SCCmec type IVa suggest highly complex mechanisms of horizontal gene transfer in MRSA. The SNP-based phylogenetic analysis suggests a zooanthroponotic transmission, i.e., a strain of human origin.

The application of the loop-mediated isothermal amplification method for rapid detection of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is an important problem associated with significant mortality and morbidity and well known as a predominant bacterial pathogen. The aim of this study was to identify MRSA strains. In this study (June 2018 to June 2019) isolates of S. aureus were obtained from patients referred to teaching hospitals of Ahvaz, Iran. All isolates were confirmed by conventional microbiological methods. In following, antimicrobial susceptibility testing (AST), MRSA screening, PCR detection of MRSA and LAMP assay were performed. Out of a total of 156 staphylococcal isolates, 126 isolates were identified as MRSA. Seventy-two (57.1%) MRSA isolates were recovered from wound. All MRSA isolates were sensitive to vancomycin, linezolid, teicoplanin, quinupristin-dalfopristin, and tigecycline. The results of LAMP showed 100% agreement with PCR. Sensitivity and specificity of the LAMP assays for the mecA genes were 100% and 100%, respectively. The LAMP assay is a rapid and simple method for the identifications of MRSA. Because of its performance without the need for specific instrumentation, this method can be easily employed in medical centers for the detection of mecA.

Comparison of quick SOFA and SIRS scales at the bedside of patients with Staphylococcus aureus bacteremia

Introducción:

Staphylococcus aureus es una de las principales causas de bacteriemia, adquirida en la comunidad o asociada con la atención en salud, la cual presenta un gran porcentaje de complicaciones y elevadas tasas de morbilidad y mortalidad. Los criterios SRIS (Systemic Inflammatory Response Syndrome) se han usado tradicionalmente con el fin de establecer la presencia de sepsis; sin embargo, recientemente se ha cuestionado su valor predictivo dada su baja sensibilidad y especificidad. En el 2016, apareció la escala qSOFA (quick Sequential Organ Failure Assessment), como una nueva herramienta para la evaluación rápida de las infecciones en los servicios de urgencias.

Objetivo.

Comparar las herramientas qSOFA y SRIS para la predicción de la bacteriemia por S. aureus.

Materiales y métodos.

Se hizo un estudio observacional sobre el comportamiento clínico de pacientes con bacteriemia por S. aureus para evaluar el perfil de resistencia fenotípica, algunas características sociodemográficas, clínicas y de laboratorio, las complicaciones y la mortalidad, así como los resultados de las evaluaciones con la escala qSOFA y los criterios SRIS, para establecer cuál podría predecir mejor la presencia de bacteriemia por S. aureus.

Resultados.

Se seleccionaron 26 pacientes con bacteriemia, en cuyas muestras S. aureus había sido el segundo germen más frecuentemente aislado. Se encontró una mortalidad del 50 % (13 casos) y una prevalencia del 30 % de S. aureus resistente a meticilina (SARM). Según los puntajes clínicos obtenidos, la escala qSOFA fue positiva en 30,8 % de los pacientes y los criterios SRIS lo fueron en el 92,3 %.

Discusión.

Se encontró una elevada mortalidad en la población analizada. La escala qSOFA fue menos efectiva para el diagnóstico que los criterios clásicos de reacción inflamatoria sistémica.

A mechanistic approach to the in-vitro resistance modulating effects of fluoxetine against meticillin resistant Staphylococcus aureus strains

Emergence of methicilin resistant Staphylococcus aureus (MRSA) strains is a major cause of infirmity worldwide and has limited our therapeutic options against these pathogens. In this regard, the search for candidates with an antimicrobial activity, with a greater efficacy and a lower toxicity, is necessary. As a result, there is greater need to search for resistance modifying agents which, in combination with existing drugs, will restore the efficacy of these drugs. The antibacterial effect of fluoxetine was determined by a broth microdilution method (the M07-A9 method of the Clinical and Laboratory Standard Institute) and flow cytometry techniques in which the probable mechanism of action of the compound was also assessed. The isolates used in the study belonged to the Laboratory of Bioprospecting of Antimicrobial Molecules (LABIMAN) of the Federal University of Ceará. After 24 h, Methicillin-resistant Sthaphylococcus aureus (MRSA) strains showed fluoxetine MICs equal to 64 μg/mL and 128 μg/mL, respectively. Cytometric analysis showed that treatment with fluoxetine caused alterations to the integrity of the plasma membranes and DNA damage, which led to cell death, probably by apoptosis.

Characterization of methicillin resistant Staphylococcus aureus strains among inpatients and outpatients in a referral hospital in Tehran, Iran

Methicillin resistant Staphylococcus aureus is one of the most common causes of a variety of infections ranging from wound infections to urinary tract infections (UTI) in hospital and community. In this study during 3 years we characterized the antibiotic resistance patterns of 491 hospital acquired MRSA and community associated MRSA strains by the guidelines of clinical and laboratory standard institute. A combination of high resolution PhP typing method and SCCmec typing were used for clonal dissemination of isolates. Among all 491 MRSA strains, diverse PhP types consisting of 29 common types (CTs) and 4 single types (STs) and also 2 different SCCmec types (III and IVa) were detected. In addition, 18 CTs were common among CA- and HA-MRSA strains and the presence of all 4 STs was limited to HA-MRSA strains. All isolates were resistant to penicillin and high level resistance was observed against ciprofloxacin, erythromycin, tobramycin and kanamycin and the rate of resistance to most of the antibiotic tested among HA-MRSA was significantly higher than CA-MRSA isolates. Moreover, all isolates showed susceptibility to linezolid, vancomycin and quinupristin-dalfopristin and very low resistance to fusidic acid, nitrofurantoin and chloramphenicol were detected. Our findings illustrated the increasing rate of clonal dissemination and persistence of highly antibiotic resistant CA-MRSA strains in Tehran hospitals, and also indicated the important role of the hospitals as the reservoir of MRSA strains.

Spreading of genes encoding enterotoxins, haemolysins, adhesin and biofilm among methicillin resistant Staphylococcus aureus strains with staphylococcal cassette chromosome mec type IIIA isolated from burn patients

The emergence of antibiotic-resistant Staphylococcus aureus in particular methicillin-resistant S. aureus (MRSA) is an important concern in burn medical centers either in Iran or worldwide. A total of 128 S. aureus isolates were collected from wound infection of burn patients during June 2013 to June 2014. Multiplex-polymerase chain reaction (MPCR) assay was performed for the characterization of the staphylococcal cassette chromosome mec (SCCmec). Genes encoding virulence factors and biofilm were targeted by PCR. Of 128 S. aureus isolates, 77 (60.1%) isolates were MRSA. Fifty four (70.1%) isolates were identified as SCCmec type IIIA. The most frequently detected toxin genes among MRSA isolates with SCCmec type IIIA were sea (64.1%) and hla (51.8%). The rate of coexistence of sea with hla and sea with hla and hlb was 37% and12.9%, respectively. The sec, eta, tst, pvl, hla and hlb genes were not detected in any of the MRSA isolates. The most prevalent genes encoding biofilm was eno, found in 61.1% of isolates, followed by fib and icaA found in 48.1% and 38.8% of the isolates, respectively. The rate of coexistence of fib + eno + icaA + icaD and fib + eno was 20.3% and 9.2%, respectively. The ebps gene was not detected in any of the isolates. In conclusion, our study indicated that the sea, hla, fib and icaA were most frequent genes encoding virulence factors among MRSA with SCCmec type IIIA isolated from burn wound infection. Moreover, the results of this study shows that the rate of coexistence of genes encoding different virulence factor were high.

Genotypic Diversity of Staphylococcus aureus α-Hemolysin Gene (hla) and Its Association with Clonal Background: Implications for Vaccine Development

The α-hemolysin, encoded by the hla gene, is a major virulence factor in S. aureus infections. Changes in key amino acid residues of α-hemolysin can result in reduction, or even loss, of toxicity. The aim of this study was to investigate the diversity of the hla gene sequence and the relationship of hla variants to the clonal background of S. aureus isolates. A total of 47 clinical isolates from China were used in this study, supplemented with in silico analysis of 318 well-characterized whole genome sequences from globally distributed isolates. A total of 28 hla genotypes were found, including three unique to isolates from China, 20 found only in the global genomes and five found in both. The hla genotype generally correlated with the clonal background, particularly the multilocus sequence type, but was not related to geographic origin, host source or methicillin-resistance phenotype. In addition, the hla gene showed greater diversity than the seven loci utilized in the MLST scheme for S. aureus. Our investigation has provided genetic data which may be useful for future studies of toxicity, immunogenicity and vaccine development.

Biofilm formation of Brazilian meticillin-resistant Staphylococcus aureus strains: prevalence of biofilm determinants and clonal profiles

Biofilms plays an important role in medical-device-related infections. This study aimed to determine the factors that influence adherence and biofilm production, as well as the relationship between strong biofilm production and genetic determinants in clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA). Fifteen strains carrying different chromosomal cassettes recovered from hospitalized patients were selected; five SCCmecII, five SCCmecIII and five SCCmecIV. The SCCmec type, agr group and the presence of the virulence genes (bbp, clfA, icaA, icaD, fnbB, bap, sasC and IS256) were assessed by PCR. PFGE and multilocus sequence typing (MLST) techniques were also performed. The initial adhesion and biofilm formation were examined by quantitative assays. The surface tension and hydrophobicity of the strains were measured by the contact angle technique to evaluate the association between these parameters and adhesion ability. SCCmecIII and IV strains were less hydrophilic, with a high value for the electron acceptor parameter and higher adhesion in comparison with SCCmecII strains. Only SCCmecIII strains could be characterized as strong biofilm producers. The PFGE showed five major pulsotypes (A-E); however, biofilm production was related to the dissemination of one specific PFGE clone (C) belonging to MLST ST239 (Brazilian epidemic clonal complex). The genes agrI, fnbB and IS256 in SCCmecIII strains were considered as genetic determinants associated with strong biofilm-formation by an ica-independent biofilm pathway. This study contributes to the understanding of biofilm production as an aggravating factor potentially involved in the persistence and severity of infections caused by multidrug-resistant MRSA belonging to this genotype.

Detection and preliminary physico-chemical properties of antimicrobial components in the native excretions/secretions of three species of Chrysomya (Diptera, Calliphoridae) in Brazil

Antibiotic-resistant bacteria in hospitals and communities increasingly threaten public health in Brazil and the rest of the World. There is an urgent need for additional antimicrobial drugs. Calliphorid blowfly larvae are a rich source of antimicrobial factors but the potential of Neotropical species has been neglected. This preliminary study evaluates the antimicrobial activity of the native excretions/secretions of larvae of three species of Brazilian calliphorids, Chrysomya megacephala, Chrysomya albiceps and Chrysomya putoria. Native excretions/secretions were collected from third instar larvae, sterile filtered and tested for antibacterial activity against Staphylococcus aureus 9518, Escherichia coli K12 4401 and Serratia marcescens 365. Turbidometric assays were made in micro-plates, using an ELISA reader, with readings taken up to 22 h. Bacterial suspensions at the start and end of each experiment were also serially diluted, spread on nutrient agar plates and then colony forming units counted. The physico-chemical characteristics of the native excretions/secretions were also tested by freezing/thawing, boiling, and protease digestion. The native excretions/secretions of larvae from these three Chrysomya species significantly inhibited bacterial growth. Therefore, Brazilian calliphorid flies could potentially provide new classes of antibiotics.

Prevalence of methicillin-resistant Staphylococcus aureus in a University Hospital in the South of Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) stand out as one of the main agents causing nosocomial and community infections. This retrospective study aimed to analyze the MRSA predominance in a university hospital in the south of Brazil and it was carried out for five years (from 2007 to 2011). 616 MRSA (33,3% of the total) were isolated and an important reduction in the MRSA predominance was observed along the study. Although it was registered a reduction in the MRSA predominance, male adult patients (41-70 years old), who were in the Medical Clinic and Adult ICU, had the highest infection rates and concerning MRSA isolates rates, these were higher in blood and tracheal aspirates. In conclusion, studies of this type are becoming relevant to recognize pathogens like MRSA and to determine its predominance.

Molecular characterization of methicillin-resistant Staphylococcus aureus resistant to tigecycline and daptomycin isolated in a hospital in Brazil

We report the molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) with resistance to tigecycline and to daptomycin isolated from intensive-care-unit patients in Brazil over a 6-month period. Thirty-six isolates (25 from infection sites, 11 from nasal sites) recovered from 23 patients who presented with MRSA infection during this period were characterized by pulsed-field gel electrophoresis, multilocus sequence typing, staphylococcal cassette chromosome mec (SCCmec) typing, and antimicrobial susceptibility profiling. Ten isolates from six patients and two isolates from different patients were resistant to tigecycline and daptomycin, respectively. Eight pulsotypes were identified and one, type A, accounted for 21 isolates from 12 patients; type A isolates were SCCmecII as were a further nine isolates of other pulsotypes. All but four of the total isolates were sequence type (ST) 5 or ST105 and classified as clonal complex (CC) 5; the historically prevalent lineage in Brazil, ST239-SCCmecIII, was identified in only three patients. Tigecycline-resistant strains were all ST105-SCCmecII and two patients were nasally colonized by strains of the same pulsotype found in infection sites. Two ST5-SCCmecII were daptomycin resistant after 48 h incubation. The origin and mechanism of these resistant strains remains unknown and further studies are warranted to determine whether such clones are becoming endemic in Brazilian hospitals and to assess their impact on infection control practice.

Antimicrobial resistance and molecular epidemiology of Staphylococcus aureus from Ulaanbaatar, Mongolia

This study aimed to characterize Staphylococcus aureus (S. aureus) strains isolated from human infections in Mongolia. Infection samples were collected at two time periods (2007–08 and 2011) by the National Center for Communicable Diseases (NCCD) in Ulaanbaatar, Mongolia. S. aureus isolates were characterized using polymerase chain reaction (PCR) for mecA, PVL, and sasX genes and tested for agr functionality. All isolates were also spa typed. A subset of isolates selected by frequency of spa types was subjected to antimicrobial susceptibility testing and multilocus sequence typing. Among 251 S. aureus isolates, genotyping demonstrated methicillin resistance in 8.8% of isolates (22/251). Approximately 28% of the tested S. aureus isolates were observed to be multidrug resistant (MDR). Sequence type (ST) 154 (spa t667) was observed to be a strain with high virulence potential, as all isolates for this spa type were positive for PVL, had a functional agr system and 78% were MDR. S. aureus isolates of ST239 (spa t037) were observed to cause infections and roughly 60% had functional agr system with a greater proportion being MDR. Additionally, new multilocus sequence types and new spa types were identified, warranting continued surveillance for S. aureus in this region.

Novel methicillin-resistant coagulase-negative Staphylococcus clone isolated from patients with haematological diseases at the Blood Bank Centre of Amazon, Brazil

Methicillin-resistant Staphylococcus remains a severe public health problem worldwide. This research was intended to identify the presence of methicillin-resistant coagulase-negative staphylococci clones and their staphylococcal cassette chromosome mec (SCCmec)-type isolate from patients with haematologic diseases presenting bacterial infections who were treated at the Blood Bank of the state of Amazonas in Brazil. Phenotypic and genotypic tests, such as SCCmec types and multilocus sequence typing (MLST), were developed to detect and characterise methicillin-resistant isolates. A total of 26 Gram-positive bacteria were isolated, such as: Staphylococcus epidermidis (8/27), Staphylococcus intermedius (4/27) and Staphylococcus aureus (4/27). Ten methicillin-resistant staphylococcal isolates were identified. MLST revealed three different sequence types: S. aureus ST243, S. epidermidis ST2 and a new clone of S. epidermidis, ST365. These findings reinforce the potential of dissemination presented by multi-resistant Staphylococcus and they suggest the introduction of monitoring actions to reduce the spread of pathogenic clonal lineages of S. aureus and S. epidermidis to avoid hospital infections and mortality risks.

Virulence strategies of the dominant USA300 lineage of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) poses a serious threat to worldwide health. Historically, MRSA clones have strictly been associated with hospital settings, and most hospital-associated MRSA (HA-MRSA) disease resulted from a limited number of virulent clones. Recently, MRSA has spread into the community causing disease in otherwise healthy people with no discernible contact with healthcare environments. These community-associated MRSA clones (CA-MRSA) are phylogenetically distinct from traditional HA-MRSA clones, and CA-MRSA strains seem to exhibit hypervirulence and more efficient host : host transmission. Consequently, CA-MRSA clones belonging to the USA300 lineage have become dominant sources of MRSA infections in North America. The rise of this successful USA300 lineage represents an important step in the evolution of emerging pathogens and a great deal of effort has been exerted to understand how these clones evolved. Here, we review much of the recent literature aimed at illuminating the source of USA300 success and broadly categorize these findings into three main categories: newly acquired virulence genes, altered expression of common virulence determinants and alterations in protein sequence that increase fitness. We argue that none of these evolutionary events alone account for the success of USA300, but rather their combination may be responsible for the rise and spread of CA-MRSA.

Lack of methicillin-resistant Staphylococcus aureus nasal carriage among patients at a primary-healthcare unit in Porto Alegre, Brazil

INTRODUCTION

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a pathogen in individuals without traditional risk factors.

MATERIAL AND METHODS

MRSA nasal carriage was assessed in individuals consulting at a Primary Health Unit in Brazil.

RESULTS

A total of 336 individuals were included: 136 were tested only for MRSA and 200 for any S. aureus. No MRSA was found among the 336 individuals and 23 (11.5%) of 200 were colonized by S. aureus.

DISCUSSION

Low prevalence rates have been found in non-hospitalized individuals, but MRSA surveillance should be encouraged to monitor clinical and molecular epidemiology of CA- MRSA.