Small Molecules Produced by Commensal Staphylococcus epidermidis Disrupt Formation of Biofilms by Staphylococcus aureus.

The microbiota influences host health through several mechanisms, including protecting it from pathogen colonization. Staphylococcus epidermidis is one of the most frequently found species in the skin microbiota, and its presence can limit the development of pathogens such as Staphylococcus aureusS. aureus causes diverse types of infections ranging from skin abscesses to bloodstream infections. Given the increasing prevalence of S. aureus drug-resistant strains, it is imperative to search for new strategies for treatment and prevention. Thus, we investigated the activity of molecules produced by a commensal S. epidermidis isolate against S. aureus biofilms. We showed that molecules present in S. epidermidis cell-free conditioned media (CFCM) caused a significant reduction in biofilm formation in most S. aureus clinical isolates, including all 4 agr types and agr-defective strains, without any impact on growth. S. epidermidis molecules also disrupted established S. aureus biofilms and reduced the antibiotic concentration required to eliminate them. Preliminary characterization of the active compound showed that its activity is resistant to heat, protease inhibitors, trypsin, proteinase K, and sodium periodate treatments, suggesting that it is not proteinaceous. RNA sequencing revealed that S. epidermidis-secreted molecules modulate the expression of hundreds of S. aureus genes, some of which are associated with biofilm production. Biofilm formation is one of the main virulence factors of S. aureus and has been associated with chronic infections and antimicrobial resistance. Therefore, molecules that can counteract this virulence factor may be promising alternatives as novel therapeutic agents to control S. aureus infections.IMPORTANCES. aureus is a leading agent of infections worldwide, and its main virulence characteristic is the ability to produce biofilms on surfaces such as medical devices. Biofilms are known to confer increased resistance to antimicrobials and to the host immune responses, requiring aggressive antibiotic treatment and removal of the infected surface. Here, we investigated a new source of antibiofilm compounds, the skin microbiome. Specifically, we found that a commensal strain of S. epidermidis produces molecules with antibiofilm activity, leading to a significant decrease of S. aureus biofilm formation and to a reduction of previously established biofilms. The molecules potentiated the activity of antibiotics and affected the expression of hundreds of S. aureus genes, including those associated with biofilm formation. Our research highlights the search for compounds that can aid us in the fight against S. aureus infections.

Methicillin resistance and virulence genes in invasive and nasal Staphylococcus epidermidis isolates from neonates.

BACKGROUND: Staphylococcus epidermidis is an opportunistic pathogen involved in hospital-acquired infections, particularly in those related to medical devices. This study characterized 50 genetically unrelated S. epidermidis isolates from bloodstream infections (BSIs, n = 31) and nares (n = 19) of neonates in relation to staphylococcal chromosomal cassette mec (SCCmec) type, biofilm production and associated genes, and the arginine catabolic mobile elements (ACME), in order to detect virulence factors that could discriminate a potential invasiveness isolate or predict an increasing pathogenicity. RESULTS: Isolates from both groups showed no difference for biofilm production and ACME genes detection. However, BSI isolates harbored more frequently the sdrF and sesI genes (p < 0.05), whereas biofilm producer isolates were associated with presence of the aap gene. The sdrF gene was also significantly more in the biofilm producer isolates from BSI. The SCCmec type IV and the ccr2 complex were related to BSI isolates (p < 0.05), while 83% of the nasal isolates were non-typeable for the SCCmec elements, with the mec complex and ccr undetectable as the most frequent profile. CONCLUSIONS: Despite the great clonal diversity displayed by S. epidermidis isolates from neonates, BSI isolates harbored more frequently the sdrF and sesI adhesin genes, while nasal isolates were very variable in SCCmec composition. These aspects could be advantageous to improve colonization in the host increasing its pathogenicity.

Influence of the microbiological component of Cariogram® for evaluating the risk of caries in children.

OBJECTIVE: To compare the risk for caries in children as determined by Cariogram® software (CS; Stockholm, Sweden) with and without its microbiological component and by a form based on Cariogram® (FBC). METHODS: Children (n = 28) aged 3-9 years were included. Data were collected clinically and from anamnesis. The salivary levels of Streptococcus mutans (SM) were evaluated. A linear regression model was used to determine which variables were predictive for each type of risk analysis. Caries risk was the dependent variable and the independent variables were caries experience, related disease, plaque amount, diet frequency, salivary levels of SM, fluoride sources and clinical judgment. A paired Student t-test was used for the following comparisons: (a) CS with and without SM; (b) CS without SM and FBC; (c) CS with SM and FBC. RESULTS: The mean dmft/DMFT was 5.56 ± 2.51. There was no difference between the methods (p < .05). Regardless of caries risk, the children presented the same levels of SM (p = .889). Caries experience, plaque amount, diet frequency and fluoride sources were predictors of caries risk in all assessment methods. Clinical judgment was a significant predictor in CS. CONCLUSIONS: Caries experience, plaque amount, diet frequency and fluoride sources are valuable predictors of caries risk; microbiological tests are not necessary for evaluating caries risk in children, which can be assessed similarly by CS without SM and FBC.

Systemic infection caused by the methicillin-resistant Staphylococcus aureus USA300-LV lineage in a Brazilian child previously colonized.

The methicillin-resistant Staphylococcus aureus (MRSA) USA300-Latin American variant (USA300-LV) lineage is well documented in northern Latin American countries. It has replaced established clones in hospital environments. We herein report a systemic infection caused by a USA300-LV isolate in a 15-year-old boy, from a low-income area of Rio de Janeiro, previously colonized by the same strain. During hospital stay, seven pvl-positive MRSA USA300-LV isolates were recovered by nasal swab, blood and abscess secretion. The patient underwent intravenous vancomycin, daptomycin, and oral sulfamethoxazole/trimethoprim, and was discharged after 45 days after full recovery. This is the first documented case of a community-acquired MRSA infection caused by the USA300-LV variant in Brazil in a previously colonized adolescent with no history of recent travel outside of Rio de Janeiro. The need for improved surveillance programs to detect MRSA colonization in order to control the spread of hypervirulent lineages among community and hospital settings is highlighted.

Subacute infective endocarditis caused by Bacillus cereus in a patient with Systemic Lupus Erythematosus.

A rare and difficult to diagnose case of subacute infective endocarditis caused by Bacillus cereus in a patient with systemic lupus erythematosus and Libman-Sacks endocarditis has been reported. Our aim is to highlight the importance of molecular methods such as MALDI-TOF and PCR to explain clinical and epidemiological issues about infections caused by unusual pathogen.

Pandemic clone USA300 in a Brazilian hospital: detection of an emergent lineage among methicillin-resistant Staphylococcus aureus isolates from bloodstream infections.

BACKGROUND: Staphylococcus aureus is one of the leading causes of bloodstream infections (BSI) worldwide. In Brazil, the hospital-acquired methicillin-resistant S. aureus USA100/SCCmecII lineage replaced the previously well-established clones. However, the emergence of community-associated (CA) MRSA lineages among hospitalized patients is an increasing issue. METHODS: Consecutive S. aureus isolates recovered from BSI episodes of patients admitted between January 2016 and December 2018 in a Brazilian teaching hospital were tested for antimicrobial resistance, their genotypic features were characterized, and the clinical characteristics of the patients were evaluated. RESULTS: A total of 123 S. aureus isolates were recovered from 113 patients. All isolates were susceptible to linezolid, teicoplanin and vancomycin and 13.8% were not susceptible to daptomycin. Vancomycin MIC50 and MIC90 of 2 mg/L were found for both MRSA and MSSA isolates. The MRSA isolation rate was 30.1% (37/123), and 51.4% of them carried the SCCmec type II, followed by SCCmecIV (40.5%). Among the 37 MRSA isolates, the main lineages found were USA100/SCCmecII/ST5 and ST105 (53.7%) and USA800/ST5/SCCmecIV (18.9%). Surprisingly, six (16%) CA-MRSA isolates, belonging to USA300/ST8/SCCmecIVa that carried PVL genes and the ACME cassette type I, were detected. These six patients with USA300 BSI had severe comorbidities, including cancer, and most had a Charlson score ≥ 5; furthermore, they were in wards attended by the same health professionals. MRSA isolates were associated with hospital acquired infections (p = 0.02) in more elderly patients (p = 0.03) and those diagnosed with hematologic cancer (p = 0.04). Among patients diagnosed with MRSA BSI, 19 (54.3%) died. CONCLUSIONS: The pandemic MRSA USA300 was detected for the first time in the Brazilian teaching hospital under study, and its cross-transmission most probably occurred between patients with BSI. This lineage may already be circulating among other Brazilian hospitals, which highlights the importance of carrying out surveillance programs to fight multidrug resistant and hypervirulent isolates.

Panton-Valentine leukocidin (PVL) isoforms among Staphylococcus aureus lineages isolated from hospitals in Rio de Janeiro, Brazil.

Panton-Valentine leukocidin (PVL) is a Staphylococcus aureus virulence factor codified by lukSF-PV genes. Single-nucleotide polymorphisms (SNPs) at lukSF-PV genes can lead to two PVL sequence variants (R and H) generating different PVL isoforms. This study analyzed lukSF-PV genes SNPs among four different clonal lineages (STs/CC 1, 5, 8, and 30) of nine S. aureus isolated at Brazilian hospitals. The sequenced products showed SNPs at seven sites (positions 121, 470, 527, 663, 856, 1396, and 1729), leading to non-synonymous substitutions in all isolates investigated. Our findings showed new R and H isoforms variants in S. aureus isolated in Brazil and suggest a possible relationship between H2b isoform and the ST30/CC30 lineage.

Methicillin-resistant Staphylococcus epidermidis isolates with reduced vancomycin susceptibility from bloodstream infections in a neonatal intensive care unit.

Introduction. Vancomycin has become the first-line therapy for most infections caused by methicillin-resistant staphylococci.Aim. To evaluate the vancomycin MIC, staphylococcal cassette chromosome mec (SCCmec) types and clonality of coagulase-negative staphylococci (CoNS) isolates recovered from neonates with true primary bloodstream infections (BSI).Methodology. CoNS isolates were prospectively recovered from blood cultures of non-repetitive patients admitted to a neonatal intensive care unit (NICU) in a tertiary-care hospital during a 3-year period. BSI was defined based on established criteria. Micro-organisms were identified phenotypically and by PCR. MIC-values for vancomycin and oxacillin were determined by broth dilution method and E-test. The SCCmec type conferring methicillin resistance was determined by multiplex PCR. The heterogeneous vancomycin (hV) resistance phenotype was screened on brain heart infusion agar containing 4 µg ml-1 of vancomycin. The clonality was investigated by PFGE.Results. Seventy-four CoNS isolates were recovered from blood cultures of neonates during the study period but only 40 (54 %) were associated with true primary BSI. Nine (22.5%) babies died. Staphylococcus epidermidis was the most prevalent species (95 %; 38/40). All S. epidermidis isolates were methicillin-resistant (MR). SCCmec type IV was predominant (55.3 %; 21/38). Most (80.0 %; 32/38) isolates exhibited vancomycin MIC-values of 2-4 µg ml-1 not associated with the SCCmec type or clonality. Sixteen (42.1%) isolates displayed hV resistance. All babies who died were harbouring MR-S. epidermidis exhibiting vancomycin MICs of 2-4 µg ml-1.Conclusion. The findings of this study demonstrated that blood invasive MR-S. epidermidis isolates recovered at NICU tend to show decreased vancomycin susceptibility making therapy of those fragile patients difficult.

Molecular characterization of methicillin-resistant and methicillin-sensitive Staphylococcus aureus isolates from human milk samples in Brazil.

Human milk is the best nutrient for infants. The donor human milk is stored in a milk bank before pasteurization. However, the human milk is not sterile and could be colonized with different types of bacteria. Many studies have shown S. aureus to be the most prevalent potential pathogen detected in human milk. This study characterized 22 methicillin-resistant and methicillin-sensitive Staphylococcus aureus isolates from raw human milk for the presence of virulence genes and agr type. Moreover, the genotypic as identified characterization was realized. The presence of virulence genes sei, seg, sec, seh, and etb was identified in resistant and sensitive strains. We observed the predominance of agr type II. The presence of SCCmec IV (67%, 4/6) and V (33%, 2/6) characterized resistant strains as CA-MRSA. Endemic lineages detected (ST1635/CC5-t002, ST5/CC5-t002, ST72/CC5-t126, ST1/CC1-t127, ST45/CC45-t065, and ST398/t1451) could be related to epidemic clones, such as USA800/ST5, USA700/ST72, USA400/ST1, USA600/ST45, and ST398. This study made it possible to understand the characteristics of virulence and clonality of some strains that circulate in breast milk in our region. The discovery of human milk colonization by MSSA and MRSA strains with molecular characteristics similar to infectious clones spread globally demonstrates the importance of monitoring strains that can spread and cause serious infections.