Case report: Personalized triple phage-antibiotic combination therapy to rescue necrotizing fasciitis caused by Panton-Valentine leukocidin-producing MRSA in a 12-year-old boy.

Maximal standard-of-care (SOC) management could not stop the life-threatening progression of a necrotizing fasciitis induced by Panton-Valentine Leukocidin-producing Methicillin-Resistant Staphylococcus aureus (MRSA) in a 12-year-old boy. Multi-route phage therapy was initiated along with antibiotics against Staphylococcus aureus, Pseudomonas aeruginosa and Stenotrophomonas maltophilia, eventually leading to full recovery with no reported adverse events.

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.

Recurrent skin and soft tissue infections (SSTIs) in three family members caused by methicillin-resistant Staphylococcus aureus (MRSA) with Panton-Valentine leukocidin (PVL) exotoxin.

Three family members attended their general practice and emergency department over a 3-month period with recurrent skin and soft tissue infections (SSTIs) such as paronychia, submandibular carbuncle and groin and gluteal abscess requiring surgical drainage. Only when two family members were concurrently admitted with abscesses requiring drainage under general anaesthetic was the definitive diagnosis reached. The wound swabs identified methicillin-resistant Staphylococcus aureus (MRSA) and subsequent identification of the exotoxin Panton-Valentine leukocidin (PVL). Following MRSA decolonisation therapy with mupirocin and octenidine, only one family member has had one recurrence of an SSTI with MRSA isolated from the wound. When patients present with a history of recurrent SSTIs or a family all have had similar presentations, the clinician should consider MRSA with PVL exotoxin infection. Then patients must be referred for confirmation to ensure management is effective for the SSTI and prescribe MRSA decolonisation therapy concurrently to reduce recurrence.

Exploring the pathogenicity of Mycoplasma pneumoniae: Focus on community-acquired respiratory distress syndrome toxins.

Community-Acquired Respiratory Distress Syndrome Toxin (CARDS TX) is a unique exotoxin produced by Mycoplasma pneumoniae (MP) and has been confirmed to possess ADP-ribosyltransferase (ART) and vacuolating activities. CARDS TX binds to receptors on the surfaces of mammalian cells followed by entry into the cells through clathrin-mediated endocytosis, and exerts cytotoxic effects by undergoing retrograde transport and finally cleavage on endosomes and cellular organelles. In addition, CARDS TX can trigger severe inflammatory reactions resulting in airway dysfunction, producing allergic inflammation and asthma-like conditions. As a newly discovered virulence factor of MP, CARDS TX has been extensively studied in recent years. As resistance to macrolide drugs has increased significantly in recent years and there is no vaccine against MP, the development of a vaccine targeting CARDS TX is considered a potential preventive measure. This review focuses on recent studies and insights into this toxin, providing directions for a better understanding of MP pathogenesis and treatment. IMPORTANCE: A serious hazard to worldwide public health in recent years, Mycoplasma pneumoniae (MP) is a prominent bacterium that causes community-acquired pneumonia (CAP) in hospitalized children. Due to their high prevalence and fatality rates, MP infections often cause both respiratory illnesses and extensive extrapulmonary symptoms. It has recently been shown that MP produces a distinct exotoxin known as Community-Acquired Respiratory Distress Syndrome Toxin (CARDS TX). Mycoplasma pneumoniae pneumonia (MPP)-like tissue injury is caused by this toxin because it has both ADP-ribosyltransferase and vacuolating properties. A better knowledge of MP etiology and therapy is provided by this review, which focuses on latest research and insights into this toxin.

Enhancing the cytotoxicity of immunotoxins by facilitating their dissociation from target receptors under the reducing conditions of the endocytic pathway.

Immunotoxins (ITs) are recombinant chimeric proteins that combine a protein toxin with a targeting moiety to facilitate the selective delivery of the toxin to cancer cells. Here, we present a novel strategy to enhance the cytosolic access of ITs by promoting their dissociation from target receptors under the reducing conditions of the endocytic pathway. We engineered monobodySS, a human fibronectin type III domain-based monobody with disulfide bond (SS)-containing paratopes, targeting receptors such as EGFR, EpCAM, Her2, and FAP. MonobodySS exhibited SS-dependent target receptor binding with a significant reduction in binding under reducing conditions. We then created monobodySS-based ITs carrying a 25 kDa fragment of Pseudomonas exotoxin A (PE25), termed monobodySS-PE25. These ITs showed dose-dependent cytotoxicity against target receptor-expressing cancer cells and a wider therapeutic window due to higher efficacy at lower doses compared to controls with SS reduction inhibited. ERSS/28-PE25, with a KD of 28 nM for EGFR, demonstrated superior tumor-killing potency compared to ER/21-PE25, which lacks an SS bond, at equivalent and lower doses. In vivo, ERSS/28-PE25 outperformed ER/21-PE25 in suppressing tumor growth in EGFR-overexpressing xenograft mouse models. This study presents a strategy for developing solid tumor-targeting ITs using SS-containing paratopes to enhance cytosolic delivery and antitumor efficacy.

Antimicrobial resistance profile of Staphylococcus aureus isolated from patients, healthcare workers, and the environment in a tertiary hospital in Addis Ababa, Ethiopia.

Staphylococcus aureus infection and colonization in patients may be transmitted to healthcare providers and the environment and subsequently cause healthcare-associated infections in other patients. Pathogenic S. aureus strains produce virulence factors, such as Panton-Valentine Leukocidin (PVL), that contribute to the severity of infections and aid in their spread. The emergence of antimicrobial resistance (AMR) is additional concern with respect to S. aureus infection. In this study, the virulence genes and antibiotic resistance profiles of S. aureus were characterized from patients' clinical isolates, healthcare workers' (HCWs') nasal colonization screenings, and the environment at a tertiary healthcare hospital in Addis Ababa, Ethiopia. A total of 365 samples were collected from September 2021 to September 2022: 73 patients' clinical specimens, 202 colonization screenings from HCWs, and 90 hospital environment's swabs. Fifty-one (25.2%) HCW and 10/90 (11.1%) environment S. aureus isolates were identified. Among the 134 isolates, 10 (7.5%) were methicillin-resistant S. aureus (MRSA). Three (4.1%), five (9.8%), and two (20.0%) of the MRSA isolates were identified from the patients, HCWs, and the environment, respectively. Overall, 118 (88.1%) were ampicillin and penicillin resistant; 70 (52.2%) were trimethoprim sulfamethoxazole resistant; and 28 (20.9%) were erythromycin resistant. S. aureus isolates from patients were more resistant to antibiotics than isolates from HCWs or the hospital environment (p<0.05). A total of 92/134 (68.6%) isolates possessed the lukfF-PV gene, which was identified in 62 (85.0%), 26 (51.0%), and 4 (40.0%) of the patient, HCWs, and the environment, respectively. The proportion of lukfF-PV gene containing S. aureus isolated from patient samples was statistically significant. Four (40.0%) of the MRSA isolates also had the lukfF-PV gene. The identification of highly AMR and virulence factors from patients, HCWs and the environment is concerning. Further studies are needed to identify potential transmission links and improve infection prevention and control.

[Zirconium-based metal-organic framework composites for solid phase extraction of brevetoxin-A from seawater].

Red tides are a type of natural marine disaster caused by harmful algae characterized by a high toxicity, wide distribution, and long duration. Since the concentration of algal toxins in seawater increases with the occurrence of red tides, algal toxins detected in seawater could be used to predict the occurrence and evolution of red tides. Brevetoxin-A (BTX-A) is a secondary metabolite produced by the harmful algae Karenia brevis, whose detection in seawater could form the basis of an accurate warning system for incoming red tides. However, due to the inherent complexity of the seawater matrix and the extremely low levels of BTX-A in seawater, the use of instruments for its direct detection is difficult. Therefore, there is an urgent need to develop a sample pretreatment method for the efficient enrichment of BTX-A in seawater. In this study, a metal-organic backbone material (UiO-66) and its composite with silica microspheres (SiO2@UiO-66) were successfully synthesized using the solvothermal method. The prepared SiO2@UiO-66 exhibited good hydrophilicity, water stability, and large specific surface area. Furthermore, it also exhibited hydrogen bonding and electrostatic interactions with BTX-A, had a strong affinity for BTX-A, and was able to efficiently adsorb BTX-A in complex matrices. Therefore, SiO2@UiO-66 showed potential as a novel packing material for the extraction of BTX-A from solid phase extraction columns. Combined with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), a highly sensitive detection method for the determination of BTX-A in marine water was established. The established analytical method had a low detection limit (3.0 pg/mL), a wide linear range (10.0 -200.0 pg/mL), and a good linear relationship (R=0.9992). Combined with the Fujian Province Red Tide Monitoring and Early Warning Information 2021 issued by the Fujian Provincial Oceanic and Fisheries Bureau, the analytical method established herein was successfully applied to analyze and monitor the content of BTX-A in actual seawater samples. This highlights the proposed system's potential for use as an early warning factor in the monitoring of red tides, representing a simple and fast pretreatment methodology for the detection of BTX-A in seawater.

Prevalence of the M1UK sublineage among emm1 Streptococcus pyogenes invasive strains isolated in the Czech Republic from December 2022 to May 2023. / Výskyt sub-linie M1 UK mezi invazivními kmeny Streptococcus pyogenes typ emm1 izolovanými od prosince 2022 do kvetna 2023 v Ceské republice.

AIMS: Since December 2022, an increase in invasive disease caused by Streptococcus pyogenes has been observed in the Czech Republic, with a shift in the clinical presentation and age of patients. Unlike in previous years, invasive disease is more common in children and adolescents under 18 years of age and in previously healthy middle-aged adults. An increase has been noticed in the number of S. pyogenes isolates from primarily sterile sites such as haemoculture, cerebrospinal fluid, pleural effusion fluid, joint fluid, and postmortem specimens. Routine emm gene typing revealed emm1 to be the predominant emm type of S. pyogenes. Between January 2023 and July 2023, 46% of all S. pyogenes isolates from invasive cases were assigned to the emm1 type. The globally spread M1UK sublineage is characterized by differences in the expression of seven genes, including the streptococcal pyrogenic toxin A (speA) gene, compared to historical emm1 iGAS strains. The aim of this study is to determine whether the more toxigenic M1UK sublineage is associated with the increase in invasive disease in the Czech Republic. METHODS: Whole genome sequencing of 41 S. pyogenes isolates from patients with invasive disease recovered in the Czech Republic in 2018 and 2019 and from December 2022 to May 2023 was performed using the MiSeq instrument (Illumina). Bioinformatics analysis was performed using freely available online tools the Bacterial and Viral Bioinformatics Resource Center. RESULTS: Based on whole genome sequencing data of 41 emm1 isolates of S. pyogenes from patients with invasive infectious disease recovered in 2018 and 2019 and from December 2022 to May 2023, the M1UK sublineage was found to be predominant from December 2022 to May 2023. CONCLUSION: The reason for the spread of the M1UK sublineage in the Czech Republic late in 2022 and in the first half of 2023 is not entirely clear, but it may be related to reduced immunity due to limited GAS transmission during lockdowns, especially in children. Another factor that may have contributed to the high incidence of invasive infectious diseases is the seasonal circulation of respiratory viruses.

An epidermal growth factor receptor-targeting immunotoxin based on IgG shows potent antitumor activity against head and neck cancer.

The epidermal growth factor receptor (EGFR) is an important target for cancer therapies. Many head and neck cancer (HNC) cells have been reported to overexpress EGFR; therefore, anti-EGFR therapies have been attempted in patients with HNC. However, its clinical efficacy is limited owing to the development of drug resistance. In this study, we developed an EGFR-targeting immunotoxin consisting of a clinically proven anti-EGFR IgG (cetuximab; CTX) and a toxin fragment (LR-LO10) derived from Pseudomonas exotoxin A (PE) using a novel site-specific conjugation technology (peptide-directed photo-crosslinking reaction), as an alternative option. The immunotoxin (CTX-LR-LO10) showed specific binding to EGFR and properties of a typical IgG, such as stability, interactions with receptors of immune cells, and pharmacokinetics, and inhibited protein synthesis via modification of elongation factor-2. Treatment of EGFR-positive HNC cells with the immunotoxin resulted in apoptotic cell death and the inhibition of cell migration and invasion. The efficacy of CTX-LR-LO10 was evaluated in xenograft mouse models, and the immunotoxin exhibited much stronger tumor suppression than CTX or LR-LO10. Transcriptome analyses revealed that the immunotoxins elicited immune responses and altered the expression of genes related to its mechanisms of action. These results support the notion that CTX-LR-LO10 may serve as a new therapeutic agent targeting EGFR-positive cancers.

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.

Panton-Valentine leucocidin gene in methicillin resistant Staphylococcus aureus isolated from tertiary care hospital in Nepal.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) expresses the Panton-Valentine leukocidin (PVL) virulence gene, which is associated with community and hospital-acquired severe MRSA infections. The objective of this study was to determine the prevalence and antibiotic susceptibility profile with a focus on the presence of the PVL gene among MRSA isolates in healthcare settings. METHODOLOGY: A total of 1,207 clinical specimens and 304 hospital environment swabs were collected in a tertiary care hospital in Nepal, and investigated following basic microbiological techniques. S. aureus was confirmed with the coagulase test. An antibiotic susceptibility test (AST) was performed by the Kirby-Bauer method and screening for MRSA was carried out by the cefoxitin disc diffusion method guided by the Clinical and Laboratory Standards Institute (CLSI), 2020. DNA was extracted and used in a polymerase chain reaction (PCR) to detect mecA and PVL genes. RESULTS: Of the 1,511 samples, 45 (2.9%) S. aureus (23 clinical and 22 environmental) were isolated. Among them, 69.6% (16/23) and 27.3% (6/22) were MRSA in clinical and environmental isolates, respectively. Twelve (52.2%) clinical isolates and seven (31.8%) environmental isolates were multidrug resistant. The majority of isolates were susceptible to vancomycin and linezolid. The PVL gene was detected in 18.2% (n = 4/22) of the MRSA isolates, of which three were from clinical sources and one was from an environmental swab. CONCLUSIONS: The prevalence of MRSA, and PVL-producing S. aureus were higher in the hospital setting. Hence, immediate and urgent implementation of infection control and sanitation measures are needed in the hospital.

Staphylococcus aureus: No ticket for the Paris 2024 Olympic Games!

Athletes are vulnerable to Staphylococcus aureus infections due to skin-to-skin contact and skin abrasions during training and competitions involving sharied sport equipment or toiletries, which promote the spread of the bacteria between athletes and within sport teams. This results not only in higher prevalence of S.aureus carriage among athletes compared to the general population, but also in outbreaks of infections, particularly skin infections, within sports teams. To limit the spread of S. aureus among athletes, a decolonization protocol can be applied when clustered cases of S. aureus infections occur, especially if Panton-Valentine leukocidin-producing strains are implicated. Finally, to avoid exposing athletes to S.aureus transmission/colonization, it is recommended to establish strict and clearly formulated individual and collective hygiene rules and to regularly disinfect shared sports equipment.

Investigation of SCCmec types using the real time PCR method in cefoxitin-resistant Staphylococcus aureus isolates.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen that can cause many community and hospital-acquired infections. This study was conducted to investigate the SCCmec gene types responsible for methicillin resistance in MRSA isolates isolated from hospitalised patients. MATERIAL AND METHODS: MRSA isolates isolated from samples sent from various clinics to Gaziantep University Hospital Microbiology Laboratory between March 2021-January 2022 were included in the study. Bacteria were identified using by VITEK 2 automated system. Cefoxitin (FOX) resistance was determined by the disc diffusion method according to EUCAST standards. Cefoxitin resistance was confirmed by the Penicillin Binding Protein 2' latex agglutination test. Types of mecA, mecC, coa, nuc, Panton Valentin Leukocidin (PVL), ccrC2, class A mec, SCCmec types in isolates detected as MRSA were investigated by real-time PCR. RESULTS: In this study, 116 isolates meeting the study criteria were examined. By detecting the nuc and coa genes in all isolates by PCR, the phenotypic identification of S.aureus was confirmed. While the mecA gene was detected in all MRSA isolates, no mecC gene was detected in any isolates. Detected SCCmec types were as follows; SCCmec Type 1 (2.6%), Type II (28.4%), Type III (12.9%), Type IVa (11.2%), Type IVb (3.4%), Type IVc (3.4%), Type IVg (12.1%), Type V (0.9%), Type VII (4.3%), Type VIII (18.1%), Type IX (0.9%), Type XII (1.7%). On the other hand, SCCmec Type VI, X, XI and XIII were not found in any isolate. It was determined that four of the MRSA isolates (3.4%) carried the PVL gene that two (50%) of these were found in SCCmec Type VIII. CONCLUSION: Monitoring of FOX resistance is an effective and safe method for determination of MRSA isolates. The change in the mec gene causes resistance, which should be monitored regularly with molecular methods. Our study is the first study in Turkey.

Does Adjunctive Clindamycin Have a Role in Staphylococcus aureus Bacteremia? A Protocol for the Adjunctive Treatment Domain of the Staphylococcus aureus Network Adaptive Platform (SNAP) Randomized Controlled Trial.

BACKGROUND: The use of adjunctive antibiotics directed against exotoxin production in Staphylococcus aureus bacteremia (SAB) is widespread, and it is recommended in many guidelines, but this is based on limited evidence. Existing guidelines are based on the theoretical premise of toxin suppression, as many strains of S. aureus produce toxins such as leukocidins (eg, Panton-Valentine leukocidin, toxic shock syndrome toxin 1, exfoliative toxins, and various enterotoxins). Many clinicians therefore believe that limiting exotoxin production release by S. aureus could reduce its virulence and improve clinical outcomes. Clindamycin, a protein synthesis inhibitor antibiotic, is commonly used for this purpose. We report the domain-specific protocol, embedded in a large adaptive, platform trial, seeking to definitively answer this question. METHODS AND ANALYSIS: The Staphylococcus aureus Network Adaptive Platform (SNAP) trial is a pragmatic, randomized, multicenter adaptive platform trial that aims to compare different SAB therapies, simultaneously, for 90-day mortality rates. The adjunctive treatment domain aims to test the effectiveness of adjunctive antibiotics, initially comparing clindamycin to no adjunctive antibiotic, but future adaptations may include other agents. Individuals will be randomized to receive either 5 days of adjunctive clindamycin (or lincomycin) or no adjunctive antibiotic therapy alongside standard-of-care antibiotics. Most participants with SAB (within 72 hours of index blood culture and with no contraindications) will be eligible to participate in this domain. Prespecified analyses are defined in the statistical appendix to the core protocol, and domain-specific secondary analyses will be adjusted for resistance to clindamycin, disease phenotype (complicated or uncomplicated SAB) and Panton-Valentine leukocidin-positive isolate.

Exploring the virulence potential of Staphylococcus aureus CC121 and CC152 lineages related to paediatric community-acquired bacteraemia in Manhiça, Mozambique.

Staphylococcus aureus is a frequent agent of bacteraemia. This bacterium has a variety of virulence traits that allow the establishment and maintenance of infection. This study explored the virulence profile of S. aureus strains causing paediatric bacteraemia (SAB) in Manhiça district, Mozambique. We analysed 336 S. aureus strains isolated from blood cultures of children younger than 5 years admitted to the Manhiça District Hospital between 2001 and 2019, previously characterized for antibiotic susceptibility and clonality. The strains virulence potential was evaluated by PCR detection of the Panton-Valentine leucocidin (PVL) encoding genes, lukS-PV/lukF-PV, assessment of the capacity for biofilm formation and pathogenicity assays in Galleria mellonella. The overall carriage of PVL-encoding genes was over 40%, although reaching ~ 70 to 100% in the last years (2014 to 2019), potentially linked to the emergence of CC152 lineage. Strong biofilm production was a frequent trait of CC152 strains. Representative CC152 and CC121 strains showed higher virulence potential in the G. mellonella model when compared to reference strains, with variations within and between CCs. Our results highlight the importance of monitoring the emergent CC152-MSSA-PVL+ and other lineages, as they display important virulence traits that may negatively impact the management of SAB paediatric patients in Manhiça district, Mozambique.

Nasal carriage of virulent and multidrug resistant Staphylococcus aureus: a possible comorbidity of COVID-19.

BACKGROUND: Staphylococcus aureus (S. aureus) associated with COVID-19 has not been well documented. This cross-sectional study evaluated the association between nasal S. aureus carriage and COVID-19. METHODS AND RESULTS: Nasopharyngeal samples were collected from 391 participants presenting for COVID-19 test in Lagos, Nigeria, and S. aureus was isolated from the samples. Antimicrobial susceptibility test was done by disc diffusion method. All S. aureus isolates were screened for the presence of mecA, panton-valentine leucocidin (PVL) and toxic shock syndrome toxin (TSST) virulence genes by polymerase chain reaction. Staphylococcal protein A (spa) typing was conducted for all the isolates. Participants with COVID-19 had double the prevalence of S. aureus (42.86%) compared to those who tested negative (20.54%). A significant association was seen between S. aureus nasal carriage and COVID-19 (p = 0.004). Antimicrobial sensitivity results showed resistance to oxacillin (100%), cefoxitin (53%), and vancomycin (98.7%). However, only 41% of the isolates harbored the mecA gene, with SCCmecV being the most common SCCmec type. There was no association between the carriage of virulence genes and COVID-19. A total of 23 Spa types were detected, with t13249 and t095 being the two most common spa types. CONCLUSION: This study examined the association between nasal S. aureus carriage and SARS-COV-2 infection. Further research is required to fully explore the implications of S. aureus co-infection with COVID-19.

Streptococcal pyrogenic exotoxin B is a superantigen that induces murine splenocyte proliferation and secretion of IL-2 and IFN-γ ex vivo.

Streptococcus pyogenes is a significant human pathogen, producing a range of virulence factors, including streptococcal pyrogenic exotoxin B (SpeB) that is associated with foodborne outbreaks. It was only known that this cysteine protease mediates cleavage of transmembrane proteins to permit bacterial penetration and is found in 25% of clinical isolates from streptococcal toxic shock syndrome patients with extreme inflammation. Its interaction with host and streptococcal proteins has been well characterized, but doubt remains about whether it constitutes a superantigen. In this study, for the first time it is shown that SpeB acts as a superantigen, similarly to other known superantigens such as staphylococcal enterotoxin A or streptococcal pyrogenic exotoxin type C, by inducing proliferation of murine splenocytes and cytokine secretion, primarily of interleukin-2 (IL-2), as shown by cytometric bead array analysis. IL-2 secretion was confirmed by enzyme-linked immunosorbent assay (ELISA) as well as secretion of interferon-γ. ELISA showed a dose-dependent relationship between SpeB concentration in splenocyte cells and IL-2 secretion levels, and it was shown that SpeB retains activity in milk pasteurized for 30 min at 63°C.

High Prevalence of Panton-Valentine Leukocidin Among Staphylococcus aureus Causing Acute Hematogenous Bone and Joint Infections From a Tertiary Children's Hospital in Vietnam.

BACKGROUND: We aimed to investigate the clinical features, antimicrobial susceptibility and pvl gene expression in Staphylococcus aureus causing acute hematogenous bone and joint infections (BJIs) in children in Vietnam. METHODS: In this prospective study, the demographics, microbiology and clinical outcomes of pediatric patients with acute hematogenous BJIs were collected from September 2022 to September 2023. Antimicrobial susceptibility profiles were determined using VITEK2 Compact system. The pvl gene encoding the Panton-Valentine leukocidin (PVL) toxin was detected by using polymerase chain reaction. Mann-Whitney, χ 2 and Fisher test were used for statistical analysis. RESULTS: In total, 78 patients (46 boys) with S. aureus acute hematogenous BJIs were recruited at the National Children's Hospital, Hanoi, Vietnam. Of all S. aureus isolates, 84.6% were methicillin-resistant S. aureus . All S. aureus isolates were susceptible to vancomycin, ciprofloxacin and levofloxacin; 97% of methicillin-resistant S. aureus isolates was resistant to clindamycin (minimum inhibitory concentration ≥8 µg/mL). The pvl gene was detected in 83.3% of isolates, including 57 methicillin-resistant S. aureus isolates. Patients in the pvl -positive group had significantly higher C-reactive protein levels than those in the pvl -negative group ( P = 0.04). In addition, all 8 children with septic shock were infected with pvl -positive S. aureus . CONCLUSIONS: PVL is a prevalent virulence factor of S. aureus in Vietnam. Furthermore, high inflammatory parameters (C-reactive protein) may be present at the time of diagnosis in PVL positivity-related acute hematogenous BJIs. Further research is necessary to enhance our understanding of the varying correlations between virulence factors and outcomes of S. aureus BJIs.

Injury of Macrophages Induced by Clostridium perfringens Type C Exotoxins.

Clostridium perfringens is a kind of anaerobic Gram-positive bacterium that widely exists in the intestinal tissue of humans and animals. And the main virulence factor in Clostridium perfringens is its exotoxins. Clostridium perfringens type C is the main strain of livestock disease, its exotoxins can induce necrotizing enteritis and enterotoxemia, which lead to the reduction in feed conversion, and a serious impact on breeding production performance. Our study found that treatment with exotoxins reduced cell viability and triggered intracellular reactive oxygen species (ROS) in human mononuclear leukemia cells (THP-1) cells. Through transcriptome sequencing analysis, we found that the levels of related proteins such as heme oxygenase 1 (HO-1) and ferroptosis signaling pathway increased significantly after treatment with exotoxins. To investigate whether ferroptosis occurred after exotoxin treatment in macrophages, we confirmed that the protein expression levels of antioxidant factors glutathione peroxidase 4/ferroptosis-suppressor-protein 1/the cystine/glutamate antiporter solute carrier family 7 member 11 (GPX4/FSP1/xCT), ferroptosis-related protein nuclear receptor coactivator 4/transferrin/transferrin receptor (NCOA4/TF/TFR)/ferritin and the level of lipid peroxidation were significantly changed. Based on the above results, our study suggested that Clostridium perfringens type C exotoxins can induce macrophage injury through oxidative stress and ferroptosis.