Diagnosis and management of Panton-Valentine leukocidin toxin associated Staphylococcus aureus infection: an update

In Vitro Detected hly II Cytotoxin in a Strain of Staphylococcus aureus (BM S-2) and Plant-Derived Aromatic Components: a Molecular Docking Study

In time, diagnosis and detection of virulence factor and its pathogenomics study continues to grow and this leads to novel treatments for infectious diseases. The objective of this study was to detect and characterise virulence genes in a haemolytic strain of Staphylococcus aureus in vitro and molecular interaction studies with herbal essential oil components in silico. A hospital biosample-isolated strain of Staphylococcus aureus (BMS-2) was resistant towards Cephalosporin. The PCR-amplified FASTA nucleotide sequence was identical with S. aureus strains absolutely. The calculated GC value was 34.05%. The translated protein sequence was identified with a conserved domain of hlyII β-channel forming cytolysin belonging to leukocidin superfamily and was predicted as a stable, non-transmembrane protein comprising B cell epitopes. Structurally, the protein was found to be composed of α helix, π-helix, extended strands, β-sheet, turn and bends with atomic composition as C₆₅₈H₁₀₂₆N₁₇₄O₂₀₀S₂. The molecular docking studies made between the HlyII cytolysin (receptor) and wet lab studied essential oil components (citral a, citronellol, eucalyptol, eugenol, geraniol, linalool, menthol, piperine and thymol) as ligands using Autodock 1.5.6 tool had inferred about prevalence of hydrogen bonds as well as covalent bonds in the intermolecular interactions. Amino acids like Tyr68, Tyr 69, Asn106, Asp67 and Asn106 were observed to be the most active residues for H-bond and hydrophobic bonds respectively. Only geraniol had interaction with glycine residue of the toxin molecule. In conclusion, geraniol with the highest ligand efficiency was observed to be the most potent phyto-constituent interacting with the in vitro detected hlyII cytotoxin.

Panton-Valentine Leukocidin-Producing Staphylococcus aureus Infection: A Case Series

Panton-Valentine leukocidin-producing Staphylococcus aureus (PVL-SA) is associated with relapsing multifocal skin and soft tissue infections (SSTI), necrotizing pneumonia (NP) and severe musculoskeletal infections. Epidemiology is underknown and underdiagnosis is likely. Recent travel abroad, case clustering and relapsing disease are often reported. We reviewed all cases of PVL-SA infection diagnosed at our center, and found 21 cases over a 43-month period. Most patients were adult males, had relevant travel history, reported recurrent disease and presented with SSTI. Etiologic diagnosis took up to five years; meanwhile, 42% of patients had antibiotic treatments. Draining procedures were required in 43% of patients and intensive care support in 19%. All patients recovered. Methicillin-resistance prevalence was 24%. Only 2/13 decolonized patients had posterior relapsing SSTI, both with likely infected contacts. PVL-SA infection’s severity and impact are clear, even in small case series as ours. Physician awareness and active PVL-gene search are crucial for an adequate management.

Antimicrobial Capacity of Plant Polyphenols against Gram-positive Bacteria: A Comprehensive Review

BACKGROUND

Multi-drug-resistant bacteria such as Methicillin-Resistant Staphylococcus aureus (MRSA) disseminate rapidly amongst patients in healthcare facilities and suppose an increasingly important cause of community-associated infections and associated mortality. The development of effective therapeutic options against resistant bacteria is a public health priority. Plant polyphenols are structurally diverse compounds that have been used for centuries for medicinal purposes, including infections treatment and possess, not only antimicrobial activity, but also antioxidant, anti-inflammatory and anticancer activities among others. Based on the existing evidence on the polyphenols' antibacterial capacity, polyphenols may be postulated as an alternative or complementary therapy for infectious diseases.

OBJECTIVE

To review the antimicrobial activity of plant polyphenols against Gram-positive bacteria, especially against S. aureus and its resistant strains. Determine the main bacterial molecular targets of polyphenols and their potential mechanism of action.

METHODOLOGY

The most relevant reports on plant polyphenols' antibacterial activity and their putative molecular targets were studied. We also performed virtual screening of thousand different polyphenols against proteins involved in the peptidoglycan biosynthesis to find potential valuable bioactive compounds. The bibliographic information used in this review was obtained from MEDLINE via PubMed.

RESULTS

Several polyphenols: phenolic acids, flavonoids (especially flavonols), tannins, lignans, stilbenes and combinations of these in botanical mixtures, have exhibited significant antibacterial activity against resistant and non-resistant Gram-positive bacteria at low μg/mL range MIC values. Their mechanism of action is quite diverse, targeting cell wall, lipid membrane, membrane receptors and ion channels, bacteria metabolites and biofilm formation. Synergic effects were also demonstrated for some combinations of polyphenols and antibiotics.

CONCLUSION

Plant polyphenols mean a promising source of antibacterial agents, either alone or in combination with existing antibiotics, for the development of new antibiotic therapies.

The Role of Staphylococcus aureus in Mastitis : A Multidisciplinary Working Group Experience

BACKGROUND

Breastfeeding women are at risk of developing mastitis during the lactation period. Staphylococcus aureus has emerged as the community-acquired pathogen responsible for virulence (methicillin resistance and Panton-Valentine leukocidin toxin producing).

RESEARCH AIM

The aim was to compare the microorganisms responsible for mastitis and breast abscesses during breastfeeding.

METHODS

This observational study was conducted with a sample of women (N = 60) admitted to our hospital between 2016 and 2018. Participants affected by mastitis and breast abscess were studied and cared for by a multidisciplinary working group. A diagnostic breast ultrasound identified the pathology.

RESULTS

Twenty-six participants (43.3%) were affected by mastitis and 34 (56.7%) by breast abscess. The most common microorganism identified was Staphylococcus aureus (S. aureus; mastitis, n = 13; abscesses, n = 24). Methicillin resistance was identified in 21 (44.7%) S. aureus strains: 17 (80.9%) cases of abscess and four (19.1%) cases of mastitis. The median number of months of breastfeeding was smaller in the methicillin-resistant S. aureus (MRSA) cases (median = 3, range = 1-20 months) than in the methicillin-sensitive S. aureus (MSSA) cases (median = 6.5, range = 3-21 months). The Panton-Valentine leukocidin toxin gene was detected in 12 (25.5%) cases (MRSA, n = 8, 66.7%; MSSA, n = 4, 33.3%). Hospitalization was required more frequently in MRSA (n = 8, 38%; five Panton-Valentine leukocidin positive) than in MSSA cases (n = 5, 19%; one Panton-Valentine leukocidin positive). Four women out of the eight MRSA cases (50%) that were Panton-Valentine leukocidin positive stopped breastfeeding during mammary pathologies, three (37.5%) participants continued breastfeeding until the follow-up recall, and one case was lost at follow-up.

CONCLUSION

Clinical severity was probably complicated by the presence of the Panton-Valentine leukocidin toxin, which required hospitalization more frequently.

Elimination of Staphylococcus aureus nasal carriage in intensive care patients lowers infection rates

This study surveys the clinical relevance of the nasal Staphylococcus aureus colonization status on intensive care unit (ICU)-acquired S. aureus infections and compares molecular characteristics of isolates from the nose and infectious sites. The 390 patients included comprised 278 non-carriers and 112 carriers. Among the carriers, 56 were decolonized with mupirocin. Decolonization was verified through a second (negative) culture. Spa typing and virulence gene profiling were performed for all isolates. Twenty six S. aureus infections were detected in the carriage group and 20 in the non-carriage group. Eighteen of these 26 (69.2%) infections were among carriers, and 8 of these 26 (30.8%) infections occurred among decolonized carriers (p = 0.02). Overall, 31/112 (27.7%) of the colonized patients and 25/46 (60.1%) of infection were due to methicillin-resistant S. aureus (MRSA). The highest frequency virulence genes were sea and hlg (both 100%) in nasal isolates and sea, hlg, fnb, and clf (100%) for infectious isolates. t030 was the most abundant spa type overall. S. aureus carriers were more likely to develop S. aureus infection compared with decolonized and non-carrying patients. The sources of ICU S. aureus infection appear to be exogenous mostly, and a predominant clone (spa type 030) plays an important role. We confirm that nasal mupirocin treatment prevents ICU infections even when there is an increased prevalence of nosocomial MRSA.

Leukotoxin and pyrogenic toxin Superantigen gene backgrounds in bloodstream and wound Staphylococcus aureus isolates from eastern region of China

Background

The bicomponent leukotoxins and the pyrogenic toxin superantigens (PTSAgs) are important virulence factors of Staphylococcus aureus. It is necessary to survey the prevalence and expression of these toxin-encoding genes for understanding the possible pathogenic capacity of S. aureus to cause disease.

Methods

Five leukotoxin genes and thirteen PTSAg determinants were detected for 177 S. aureus isolates from blood (n = 88) and wound (n = 89) infections by Polymerase Chain Reaction (PCR). The expression of leukotoxin ED (lukED) was determined by quantitative real-time PCR (qRT-PCR). The genetic backgrounds of isolates were analyzed by Staphylococcal Cassette Chromosome mec (SCCmec) typing (for methicillin-resistant S. aureus isolates), Pulsed-Field Gel Electrophoresis (PFGE), accessory gene regulator (agr) typing and Multilocus Sequence Typing (MLST, for representative isolates based on PFGE type) methods.

Results

99.4% (176/177) isolates contained at least one of leukotoxin genes. Among them, 94.9% (168/177), 81.4% (144/177) and 67.8% (120/177) isolates harbored hlgBC, lukED and lukAB, respectively. Compared to leukotoxin genes, there was a relatively lower overall prevalence of PTSAg genes [99.4% versus 72.9% (129/177), P < 0.001], and they were organized in 59 patterns, with the most common combination of the egc cluster with or without other PTSAg genes. Genetic analysis showed the distributions of certain toxin genes were associated with the genetic backgrounds of isolates. The egc cluster was a common feature of CC5 isolates, among which ST5 and ST764 isolates harbored more PTSAg genes. The lukED was not present in ST398 isolates, and its expression was quite different among isolates. No significant correlations were observed between the lukED expression levels of strains and the ST or agr types.

Conclusions

The present study elucidated the distribution of leukotoxin and PTSAg genes and the expression of lukED in blood and wound isolates, and analyzed the relationship between them with genetic characteristics of isolates. These data improve the current understanding of the possible pathogenicity of S. aureus.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3297-0) contains supplementary material, which is available to authorized users.

Panton-Valentine Leucocidin (PVL) as a Potential Indicator for Prevalence, Duration, and Severity of Staphylococcus aureus Osteomyelitis

Staphylococcus aureus is the most common cause of the difficult-to-treat osteomyelitis (OM). To better diagnose and manage S. aureus OM, especially for severe and long duration cases, indicators for risk prediction and severity evaluation are needed. Here, 139 clinical S. aureus isolates from orthopedic infections were divided into OM group (60 isolates from 60 OM patients) and non-OM group (79 isolates from 79 non-OM patients). Molecular types, antimicrobial susceptibility, and virulence factor profiles were evaluated and compared between the two groups to identify potential indicators associated with the prevalence of S. aureus OM. Clinical manifestations and laboratory data were analyzed to identify indicators affecting OM duration and severity. We found that some sequence types were specific to OM infection. The pvl, bbp, and ebps genes were associated with S. aureus OM prevalence. The pvl, bbp, and sei genes were associated with relatively longer OM duration. Panton-Valentine leucocidin (PVL)-positive S. aureus OM presented more serious inflammatory responses. Our results emphasize the significance of PVL in affecting the prevalence, duration, and severity of S. aureus OM. Diagnosing and monitoring PVL-related S. aureus OM may help direct better prognosis and treatment of these patients.