Necrotizing pneumonia secondary to Influenza A (H1N1) coinfection with Staphylococcus aureus: A case report.

Objective: This study aims to enhance understanding of necrotizing pneumonia and toxic shock syndrome by analyzing an adult case of community-acquired necrotizing pneumonia caused by co-infection of Influenza A (H1N1) and Staphylococcus aureus with LukS-PV and LukF-PV virulence factor genes. Method: The clinical data of one patient admitted to the intensive care unit (ICU) with co-infection of Influenza A (H1N1) and Staphylococcus aureus was retrospectively analyzed. Results: The patient exhibited typical clinical manifestations of viral and Staphylococcus aureus co-infection, including necrotizing pneumonia and toxic shock syndrome. The presence of LukS-PV and LukF-PV virulence factor genes of Staphylococcus aureus was detected in the patient's bronchoalveolar lavage fluid. Unfortunately，although antiviral agents (oseltamivir) and antibiotics (linezolid, imipenem-cilastatin) were timely administrated, as well as corticosteroids for anti-inflammatory purposes, the patient's condition was progressively deteriorated and eventually led to death. Conclusion: Clinical practitioners should be vigilant about the co-infection of Influenza virus and Staphylococcus aureus, particularly when the latter carries virulence factors. The presence of virulence factor genes of Staphylococcus aureus can lead to necrotizing pneumonia with a poor prognosis. This is a particular concern because both infections can be life threatening in young adults.

A simple scoring algorithm predicting paravertebral and/or iliopsoas abscess among adults with community-onset bloodstream infections: matters of PVL-producing Staphylococcus aureus.

PURPOSE: Misdiagnosis or delayed diagnosis of paravertebral and/or iliopsoas abscess (PVIPA) has been frequently reported to be associated with unfavorable prognosis. We aimed to develop a scoring algorithm that can easily and accurately identify patients at greater risk for PVIPA among individuals with community-onset bloodstream infections. METHODS: In a multicenter, retrospective cohort study, the score was developed with the first four study years and validated with the remaining two years. Applying logistic regression, the score values of prediction determinants were derived from the adjusted odds ratios (AOR). The performance of the scoring algorithm was assessed with the receiver operating characteristic (ROC) curve. RESULTS: In the derivation (3869 patients) and validation (1608) cohorts, patients with PVIPA accounted for 1.7% and 1.4%, respectively. In the derivation cohort, five independent predictors of PVIPA were recognized using multivariable analyses: time-to-defervescence > 5 days (AOR, 7.00; 2 points), Panton-Valentine Leukocidin (PVL)-producing Staphylococcus aureus (AOR, 5.98; 2 points), intravenous drug users (AOR, 2.60; 1 points), and comorbid hemato-oncology (AOR, 0.41; -1 point) or liver cirrhosis (AOR, 2.56; 1 points). In the derivation and validation cohorts, areas under ROC curves (95% confidence intervals) of the prediction algorithm are 0.83 (0.77-0.88) and 0.85 (0.80-0.90), and a cutoff score of + 2 represents sensitivity of 83.3% and 95.7%, specificity of 68.6% and 67.7%, positive predictive values of 4.4% and 4.1%, and negative predictive values of 99.6% and 99.9%, respectively. CONCLUSIONS: Of a scoring algorithm with substantial sensitivity and specificity in predicting PVIPA, PVL-producing S. aureus and Time-to-defervescence > 5 days were crucial determinants.

Exploration of compounds to inhibit the Panton-Valentine leukocidin of Staphylococcus aureus.

The Panton-Valentine leukocidin (PVL) of Staphylococcus aureus is associated with necrotizing infections. After binding to complement 5a receptor (C5aR/CD88) and CD45 it causes cytolysis in polymorphonuclear neutrophils (PMNs) as well as inflammasome activation in monocytes. The objective of this study was to test if (ant)agonists of C5aR and CD45 can attenuate the effect of PVL on PMNs and monocytes. We tested the effect of various concentrations of six C5aR (ant)agonists (avacopan, BM213, DF2593A, JPE-1375, PMX205 and W-54011) and one CD45 antagonist (NQ301) to attenuate the cytotoxic effect of PVL on human PMNs and monocytes in vitro. Shifts in the half-maximal effective concentration (EC50) of PVL to achieve a cytotoxic effect on PMNs and modulation of inflammatory cytokine response from monocytes were determined by flow cytometry and IL-1ß detection. Pre-treatment of PMNs with avacopan, PMX205 and W-54,011 resulted in 3.6- to 4.3-fold shifts in the EC50 for PVL and were able to suppress IL-1ß secretion by human monocytes in the presence of PVL. BM213, DF2593A and NQ301 were unable to change the susceptibility of PMNs towards PVL or reduce inflammasome activation in monocytes. Avacopan, PMX205 and W-54,011 showed protection against PVL-induced cytotoxicity and suppressed IL-1ß secretion by monocytes. Clinical studies are needed to prove whether these substances can be used therapeutically as repurposed drugs.

A Single Lung Abscess Caused by Panton-Valentine Leukocidin-Producing Methicillin-Resistant Staphylococcus aureus.

This case report presents a rare occurrence of a single lung abscess caused by Panton-Valentine leukocidin (PVL)-producing methicillin-resistant Staphylococcus aureus (MRSA) in a 38-year-old immunocompetent man. The patient, of Southeast Asian origin, presented with symptoms of fever, chest pain, cough, and shortness of breath following a recent flu-like illness. Imaging indicated a cavitary lung lesion in the left lower lobe, suggestive of a lung abscess. Initial antibiotic treatment failed, and drainage of the abscess confirmed MRSA with the PVL gene, indicating a community-acquired MRSA infection. The patient received intravenous vancomycin followed by oral linezolid, leading to the resolution of the abscess. Contact tracing and decolonization measures were implemented. This case highlights the importance of considering PVL-producing S. aureus as a potential pathogen in severe necrotizing pneumonia or sepsis and underscores the need for prompt diagnosis, appropriate antibiotic therapy, and infection control measures in managing such infections.

Panton-Valentine Leukocidin-Positive Staphylococcus aureus in Family and Pet Cat.

Continued detection of Panton-Valentine leukocidin-positive Staphylococcus aureus in samples from a family with severe repeated skin infections and their pet cat suggests transmission between the family and the cat. Decolonizing the pet led to successful elimination of the bacteria from the household. Clinicians should consider pet cats as possible reinfection sources.

Characterisation of PVL-Positive Staphylococcus argenteus from the United Arab Emirates.

Staphylococcus argenteus is a recently described staphylococcal species that is related to Staphylococcus aureus but lacks the staphyloxanthin operon. It is able to acquire both resistance markers such as the SCCmec elements and mobile genetic elements carrying virulence-associated genes from S. aureus. This includes those encoding the Panton-Valentine leukocidin (PVL), which is associated mainly with severe and/or recurrent staphylococcal skin and soft tissue infections. Here, we describe the genome sequences of two PVL-positive, mecA-negative S. argenteus sequence type (ST) 2250 isolates from the United Arab Emirates in detail. The isolates were found in a dental clinic in the United Arab Emirates (UAE). Both were sequenced using Oxford Nanopore Technology (ONT). This demonstrated the presence of temperate bacteriophages in the staphylococcal genomes, including a PVL prophage. It was essentially identical to the published sequence of phiSa2wa_st78 (GenBank NC_055048), a PVL phage from an Australian S. aureus clonal complex (CC) 88 isolate. Besides the PVL prophage, one isolate carried another prophage and the second isolate carried two additional prophages, whereby the region between these two prophages was inverted. This "flipped" region comprised about 1,083,000 bp, or more than a third of the strain's genome, and it included the PVL prophage. Prophages were induced by Mitomycin C treatment and subjected to transmission electron microscopy (TEM). This yielded, in accordance to the sequencing results, one or, respectively, two distinct populations of icosahedral phages. It also showed prolate phages which presumptively might be identified as the PVL phage. This observation highlights the significance bacteriophages have as agents of horizontal gene transfer as well as the need for monitoring emerging staphylococcal strains, especially in cosmopolitan settings such as the UAE.

A case of community-acquired Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus (MRSA) necrotizing pneumonia successfully treated with two anti-MRSA drugs.

A 22-year-old Vietnamese man was referred to our hospital owing to cough, dyspnea, and difficulty moving. The patient was diagnosed with community-acquired Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus (MRSA) bacteremia and necrotizing pneumonia. Treatment involved vancomycin (VCM) and meropenem, and the MRSA bacteremia improved. However, lung tissue destruction progressed. Therefore, linezolid was added to the VCM regimen, and this intervention led to the patient's recovery, and he was discharged from the hospital. Here, we report a case in which the patient was treated with a combination of two anti-MRSA drugs and was cured.

Clinical impact and public health challenges of a PVL-MRSA bacteraemia outbreak amongst people who inject drugs in South Yorkshire, UK.

Background: Panton-Valentine leukocidin (PVL) Staphylococcus aureus (SA) is an emergent public health concern. PVL toxin has been mostly associated with methicillin-sensitive S. aureus (MSSA)-related skin and soft tissue infections occurring in high-risk groups such as people who inject drugs (PWID). The emergence of PVL methicillin-resistant S. aureus (MRSA) infection is causing severe and life-threatening disease in PWID. Clinical cases: We present an outbreak of eight PVL-MRSA bacteraemia cases at a UK teaching hospital between 2018 and 2022. An additional four patients developed bacteraemia with PVL-negative MRSA of the same multilocus sequence type (MLST). All patients were PWID and aged 33-51 years old. Four patients developed MRSA bacterial endocarditis. Three patients died. These cases represent the initial cases detected at Doncaster and Bassetlaw Teaching Hospitals of what is an ongoing and developing outbreak. Management: An outbreak investigation has been undertaken in association with the UK Health Security Agency. Epidemiological factors have been explored, including via direct contact at a local sheltered accommodation and the possibility of a contaminated drug supply. Whole-genome sequencing confirmed that all isolates were closely related and of the same MLST (sequence type 5). A community substance misuse group disseminated health education on the prevention of PVL-MRSA. Preventing infection in PWID presents a major challenge due to the impact of addiction on engagement with services and the significant barriers faced by our patients in observing infection prevention measures. Conclusion: PVL-MRSA is of major public health concern and outbreak investigation and mapping out local epidemiological patterns plays a vital role in preventing further spread throughout the community. Additionally, this work enables targeted and early treatment in patients in high-risk categories for disease. These cases of PVL-MRSA infection in PWID highlights the transmissibility, pathogenic potential and severe clinical disease spectrum within this population. Further work is required to tackle transmission and infection from this pathogenic strain.

A Study of Community-Acquired Pyodermas with Special Reference to Panton-Valentine Leukocidin (PVL)-Positive Methicillin-Resistant Staphylococcus Aureus.

Background: Community-acquired (CA) pyodermas are one of the most common infections encountered in the dermatology outpatient clinics. A significant number of these conditions are caused by Staphylococcus aureus. CA-methicillin-sensitive Staphylococcus aureus (MSSA) and CA-methicillin-resistant Staphylococcus aureus (MRSA) have specific virulence genes which are associated with these diseases, particularly the Panton-Valentine leukocidin (PVL) genes. The presence of the PVL gene as a virulence factor may be associated with recurrent and severe skin infections. Materials and Methods: A prospective study was conducted with 205 cases of CA pyodermas, of which five were discarded due to mixed isolates. Clinical details were taken and wound exudate was sent for bacteriological examination. Further, the molecular study was performed on all MRSA (7) isolates and 13 randomly selected MSSA isolates using polymerase chain reaction for mecA and PVL genes. Results: Staphylococcus aureus was the most common organism (90%) isolated from primary or secondary CA pyodermas. The prevalence of CA-MRSA among all pyodermas was 3.5% in our community. The PVL gene was not detected in all tested CA-MRSA and CA-MSSA isolates. Conclusion: While pyodermas are common, the prevalence of MRSA is low in the CA pyodermas in our region. PVL does not appear to be a virulence factor among the isolated MRSA. Larger, multicentric, and periodic studies are, however, required to further justify these claims.

Panton-Valentine leukocidin-induced neutrophil extracellular traps lack antimicrobial activity and are readily induced in patients with recurrent PVL + -Staphylococcus aureus infections.

Staphylococcus aureus strains that produce the toxin Panton-Valentine leukocidin (PVL-SA) frequently cause recurrent skin and soft tissue infections. PVL binds to and kills human neutrophils, resulting in the formation of neutrophil extracellular traps (NETs), but the pathomechanism has not been extensively studied. Furthermore, it is unclear why some individuals colonized with PVL-SA experience recurring infections whereas others are asymptomatic. We thus aimed to (1) investigate how PVL exerts its pathogenicity on neutrophils and (2) identify factors that could help to explain the predisposition of patients with recurring infections. We provide genetic and pharmacological evidence that PVL-induced NET formation is independent of NADPH oxidase and reactive oxygen species production. Moreover, through NET proteome analysis we identified that the protein content of PVL-induced NETs is different from NETs induced by mitogen or the microbial toxin nigericin. The abundance of the proteins cathelicidin (CAMP), elastase (NE), and proteinase 3 (PRTN3) was lower on PVL-induced NETs, and as such they were unable to kill S. aureus. Furthermore, we found that neutrophils from affected patients express higher levels of CD45, one of the PVL receptors, and are more susceptible to be killed at a low PVL concentration than control neutrophils. Neutrophils from patients that experience recurring PVL-positive infections may thus be more sensitive to PVL-induced NET formation, which might impair their ability to combat the infection.