Necrotizing haemorrhagic pneumonia proves fatal in an immunocompetent child due to Panton-Valentine Leucocidin, toxic shock syndrome toxins 1 and 2 and enterotoxin C-producing Staphylococcus aureus

Molecular characterization of Staphylococcus aureus isolates derived from severe pneumonia: a retrospective monocentre study

BACKGROUND

Staphylococcus aureus is endowed with a repertoire of virulence factors potentially implicated in its pathogenicity and ability to cause invasive disease. The main objective of this study was to describe the bacterial genotype, including virulence genes and affiliation to clonal complexes (CCs), encountered in severe pneumonia.

METHODS

DNA microarray was used to analyse 18 S. aureus isolates from patients hospitalized with severe pneumonia between 2017 and 2019.

RESULTS

Among 18 S. aureus isolates, 14 were methicillin-susceptible S. aureus (MSSA), and 4 methicillin-resistant S. aureus (MRSA). There were 14 community-acquired, 3 healthcare-associated, and 1 hospital-acquired infections. Different radiological presentations were observed: necrotizing pneumonia (n = 8, 44%), alveolar consolidation (n = 7, 39%), alveolar-interstitial infiltrates (n = 3, 17%). Sixteen patients (89%) required ICU hospitalization, 13 (72%) an invasive mechanical ventilation, and 12 (67%) a vasopressor support. Mortality affected 6 patients (33%). Panton-Valentine leukocidin (PVL), staphylococcal enterotoxins, toxic shock syndrome toxine-1 (TSST-1) encoding genes were documented in nine (50%), 12 (67%), one (6%) of the isolates, respectively. Accessory regulator gene group I was the most reported (n = 9, 50%) and was found in five deaths. The majority of isolates were affiliated to CC152 (n = 6), followed by CC15 (n = 3), CC45 (n = 2), CC30 (n = 2), CC1 (n = 2), CC8 (n = 1), CC9 (n = 1), and CC25 (n = 1). All the CC152 isolates were PVL-positive.

CONCLUSION

CC152-PVL positive S. aureus strains were the most prevalent in severe pneumonia. Other virulence gene profiles were found coupled to additional clonal lineages. A genotyping strategy contributes to describe the current circulating strains and bacterial genetic backgrounds.

Two Cases of Intrafamilial Transmission of Community-Acquired Methicillin-Resistant Staphylococcus aureus Producing Both PVL and TSST-1 Causing Fatal Necrotizing Pneumonia and Sepsis

Introduction

Staphylococcus aureus produces numerous toxins, such as toxic shock syndrome toxin 1 (TSST-1) and Panton–Valentine leukocidin (PVL). We isolated community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains producing both TSST-1 and PVL isolated from severe necrotizing pneumonia cases in a Nepali family. Detection of these CA-MRSA strains is rare in the world, and infection with these strains can take a rapidly progressive and lethal course. In this study, we traced the clinical course of this case and conducted a genetic analysis of the isolated strains.

Case Report

We described 2 familial cases (a 20-year-old male and 61-year-old female) of severe necrotizing pneumonia caused by CA-MRSA with the TSST-1 and PVL genes. A 20-year-old Nepalese male was admitted to our hospital after a 3-day history of high fever and coughing. Despite resuscitation efforts, he died of multiple organ failure. A 61-year-old Nepalese female was admitted to our hospital with a complaint of high fever and dyspnea for 1 day. She was the grandmother of the male subject and mostly stayed at his residence in Japan. We administered intravenous antibiotics, including anti-MRSA antibiotics, and she improved in 2 weeks. The sequence type of the isolates was ST22/SCCmec type IVa, and the spa type was t005. The virulence genes detected were as follows: PVL gene (lukSF-pv), TSST-1 gene (tst-1), sec, seg, sei, sel, sem, sen, seo, and seu. ST22 was not the dominant CA-MRSA clone type in Japan. Some of the reports demonstrated that PVL-/TSST-1-positive ST22-MRSA strains are prevalent in Nepal. Therefore, the MRSA strains were thought to be acquired from Nepal.

Conclusion

These cases highlight the emergence of TSST-1- and PVL-positive CA-MRSA infection and its association with life-threatening community-acquired necrotizing pneumonia. Clinicians should note the possibility of introducing MRSA strains from abroad and be aware of this illness to initiate appropriate treatment.

Passive therapy with humanized anti-staphylococcal enterotoxin B antibodies attenuates systemic inflammatory response and protects from lethal pneumonia caused by staphylococcal enterotoxin B-producing Staphylococcus aureus

Drugs such as linezolid that inhibit bacterial protein synthesis may be beneficial in treating infections caused by toxigenic Staphylococcus aureus. As protein synthesis inhibitors have no effect on preformed toxins, neutralization of pathogenic exotoxins with anti-toxin antibodies may be beneficial in conjunction with antibacterial therapy. Herein, we evaluated the efficacy of human-mouse chimeric high-affinity neutralizing anti-staphylococcal enterotoxin B (SEB) antibodies in the treatment of experimental pneumonia caused by SEB-producing S. aureus. Since HLA class II transgenic mice mount a stronger systemic immune response following challenge with SEB and are more susceptible to SEB-induced lethal toxic shock than conventional mice strains, HLA-DR3 transgenic mice were used. Lethal pneumonia caused by SEB-producing S. aureus in HLA-DR3 transgenic mice was characterized by robust T cell activation and elevated systemic levels of several pro-inflammatory cytokines and chemokines. Prophylactic administration of a single dose of linezolid 30 min prior to the onset of infection attenuated the systemic inflammatory response and protected from mortality whereas linezolid administered 60 min after the onset of infection failed to confer significant protection. Human-mouse chimeric high-affinity neutralizing anti-SEB antibodies alone, but not polyclonal human IgG, mitigated this response and protected from death when administered immediately after initiation of infection. Further, anti-SEB antibodies as well as intact polyclonal human IgG, but not its Fab or Fc fragments, protected from lethal pneumonia when followed with linezolid therapy 60 min later. In conclusion, neutralization of superantigens with high-affinity antibodies may have beneficial effects in pneumonia.

Genetic diversity of pvl-positive community-onset methicillin-resistant Staphylococcus aureus isolated at a university hospital in Japan

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is pathogenic to healthy individuals and a significant issue throughout the world. Panton-Valentine leukocidin gene (pvl)-positive sequence type (ST) 8-staphylococcal cassette chromosome (SCC) mec type IV (ST8-IV) as represented by the USA300 clone, is the most prevalent CA-MRSA in many countries. However, the prevalence of pvl-positive CA-MRSA was limited in Japan. Here, we report the incidence of pvl-positive community-onset MRSA (CO-MRSA) isolated from 10 patients seen between 2009 and 2014 at a Japanese university hospital. All patients were Japanese and eight cases involved severe skin infections. Antimicrobial susceptibility patterns of the pvl-positive isolates were consistent with those of a typical CA-MRSA clone. Detailed molecular epidemiological analyses showed that three isolates were ST8-IV USA300 clones, whereas the other seven were ST30-IV (three isolates), ST30-I (one isolate), ST59-V (two isolates), and ST1-V (one isolate) clones. No clear difference of infection severity was found between the patients associated with the USA300 clone and those with the other clones. Our findings show that, not only the USA300 clone, but also diverse pvl-positive CO-MRSA clones exist in the community and cause severe skin infections in Japan.

Pathogenesis of Staphylococcus aureus necrotizing pneumonia: the role of PVL and an influenza coinfection

Only recently necrotizing pneumonia was defined as a specific disease entity that is caused by a Panton-Valentine leukocidin (PVL)-producing Staphylococcus aureus strain and is frequently preceded by an influenza infection. Necrotizing pneumonia is characterized by a sudden onset and rapid worsening of symptoms, leukopenia, airway hemorrhages, severe respiratory failure and a high mortality rate. Despite clear epidemiological data, the function of PVL in necrotizing pneumonia has been controversially discussed due to conflicting results from different disease models. Furthermore, there are many proposed mechanisms how a viral infection could facilitate and interact with a bacterial superinfection. In this review, we summarize current data from 43 clinical cases and results from various infection models on necrotizing pneumonia. We discuss the contribution of S. aureus PVL and a preceding influenza infection and present a concept of the pathogenesis of necrotizing pneumonia.

Panton-Valentine leukocidin Staphylococcus causing fatal necrotising pneumonia in a young boy

Panton-Valentine leukocidin (PVL) toxin producing strains of Staphylococcus aureus are known to cause skin and soft tissue infection. They can also cause necrotising pneumonia in otherwise healthy individuals. Here we report a case of severe, necrotising, haemorrhagic pneumonia in a 12-year-old boy who presented with a four-day history of a sore throat and fever. During his admission he deteriorated and needed full ventilatory support but despite all efforts he died. Postmortem examination lung swabs confirmed the presence of PVL-associated S aureus. There is a need to improve awareness of this disease among medical practitioners as early diagnosis and appropriate management can save lives.

Linezolid is superior to vancomycin in experimental pneumonia caused by Superantigen-Producing staphylococcus aureus in HLA class II transgenic mice

Superantigens (SAg), the potent activators of the immune system, are important determinants of Staphylococcus aureus virulence and pathogenicity. Superior response to SAg in human leukocyte antigen (HLA)-DR3 transgenic mice rendered them more susceptible than C57BL/6 mice to pneumonia caused by SAg-producing strains of S. aureus. Linezolid, a bacterial protein synthesis inhibitor, was superior to vancomycin in inhibiting SAg production by S. aureus in vitro and conferred greater protection from pneumonia caused by SAg-producing staphylococci.

Panton-Valentine leukocidin-associated Staphylococcus aureus necrotizing pneumonia in infants: a report of four cases and review of the literature

Four children under 16 months of age presented within an 18-month period with severe, rapidly progressive Panton-Valentine leukocidin-associated ST93 Staphylococcus aureus necrotizing pneumonia. Two of the cases that required extracorporeal membranous oxygenation and proved fatal had poor prognostic features of leukopenia, rash and pulmonary haemorrhage. All four cases had recent contact with S. aureus infection in a family member. Reported cases of S. aureus necrotizing pneumonia in infants are reviewed, and approach to management is discussed.

Community-acquired necrotizing pneumonia due to methicillin-sensitive Staphylococcus aureus secreting Panton-Valentine leukocidin: a review of case reports

BACKGROUND

Community-acquired necrotizing pneumonia caused by Panton-Valentine leukocidin (PVL)-secreting Staphylococcus aureus is a highly lethal infection that mainly affects healthy children and young adults. Both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) may carry the PVL-phage, but the majority of publications relate to community-associated methicillin-resistant S. aureus (CA-MRSA) or mixed patient groups. This study focuses on necrotizing pneumonia due to methicillin-sensitive S. aureus strains, with the purpose to determine factors associated with outcome.

METHODS

We report a patient with PVL secreting MSSA necrotizing pneumonia and performed a systematic review of similar case in the literature. We analyzed factors associated with outcome.

RESULTS

A total of 32 patient descriptions were retained for analysis. Septic shock (p = 0.007), influenza-like prodrome (p = 0.02), and the absence of a previous skin and soft-tissue infection (p = 0.024) were associated with fatal outcome. In multivariate analysis, influenza-like prodrome (odds ratio (OR), 7.44; 95% confidence interval (CI), 1.24-44.76; p = 0.028) and absence of previous skin and soft-tissue infection (OR, 0.09; 95% CI, 0.01-0.86; p = 0.036) remained significant predictors of death.

CONCLUSIONS

Influenza-like prodrome may be predictive of adverse outcome in PVL-secreting MSSA necrotizing pneumonia. In contrast, previous skin and soft-tissue infection may be associated with improved prognosis.

Fatal S. aureus hemorrhagic pneumonia: genetic analysis of a unique clinical isolate producing both PVL and TSST-1

In 2008, an unusual strain of methicillin-sensitive Staphylococcus aureus (MSSA68111), producing both Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin-1 (TSST-1), was isolated from a fatal case of necrotizing pneumonia. Because PVL/TSST-1 co-production in S. aureus is rare, we characterized the molecular organization of these toxin genes in strain 68111. MSSA68111 carries the PVL genes within a novel temperate prophage we call ФPVLv68111 that is most similar, though not identical, to phage ФPVL--a phage type that is relatively rare worldwide. The TSST-1 gene (tst) in MSSA68111 is carried on a unique staphylococcal pathogenicity island (SaPI) we call SaPI68111. Features of SaPI68111 suggest it likely arose through multiple major recombination events with other known SaPIs. Both ФPVLv68111 and SaPI68111 are fully mobilizable and therefore transmissible to other strains. Taken together, these findings suggest that hypervirulent S. aureus have the potential to emerge worldwide.

Purpura fulminans caused by community-associated methicillin-resistant Staphylococcus aureus

Sepsis-induced purpura fulminans is a rare but life-threatening condition characterized by rapidly progressive hemorrhagic infarction of the skin due to dermal vascular thrombosis resulting in tissue loss and severe scarring. Although most commonly related to meningococcal or invasive group A streptococcal disease, it may also be caused by several other bacterial or viral pathogens including Pneumococcus and Varicella. Purpura fulminans associated with Staphylococcus aureus sepsis is rare but has been reported in adults. However, the syndrome is very unusual in children, and to our knowledge, only 2 cases of staphylococcal purpura fulminans have been reported in children, both due to methicillin-susceptible S aureus in the United Kingdom. We report the first well-described case of purpura fulminans due to community-associated methicillin-resistant S aureus in a child.

Factors associated with the outcome of life-threatening necrotizing pneumonia due to community-acquired Staphylococcus aureus in adult and adolescent patients

BACKGROUND

Although community-acquired Staphylococcus aureus pneumonia with highly virulent Panton-Valentine leukocidin (PVL)-positive strains, a severe disease with significant lethality, is rare, especially in adult and adolescent patients, recent reports highlight that these infections are on the rise.

OBJECTIVES

To describe the demographic and clinical features of reported cases of life-threatening community-acquired S. aureus pneumonia with usually PVL-positive strains in adult and adolescent patients, to evaluate the variables related to death, and to select a more appropriate antimicrobial treatment for this potentially deadly disease.

METHODS

We summarized all of the 92 reported cases and our case. The effect of 5 variables on mortality was measured using logistic regression.

RESULTS

S. aureus community-acquired pneumonia (CAP) with usually PVL-positive strains is a severe disease with significant lethality, i.e. 42.9%; a short duration of the time from the onset of symptoms to death, i.e. 5.5 ± 10.1 days, and prolonged hospital admissions, i.e. 33.2 ± 29.5 days. Seventy-three cases have been tested for the gene for PVL, and 71 strains have been found to carry the PVL gene. Logistic regression analysis showed that leucopenia (p = 0.002), influenza-like symptoms or laboratory-confirmed influenza (p = 0.011), and hemoptysis (p = 0.024) were the factors associated with death. Antibiotic therapies inhibiting toxin production were associated with an improved outcome in these cases (p = 0.007).

CONCLUSIONS

Physicians should pay special attention to those patients who acquired severe CAP during influenza season and have flu-like symptoms, hemoptysis, and leucopenia, and they should consider S. aureus more frequently among the possible pathogens of severe CAP. Empiric therapy for severe CAP with this distinct clinical picture should include coverage for S. aureus. Targeted treatment with antimicrobials inhibiting toxin production appears to be a more appropriate selection.

Screening for staphylococcal superantigen genes shows no correlation with the presence or the severity of chronic rhinosinusitis and nasal polyposis

BACKGROUND

Staphylococcus aureus secretes numerous exotoxins which may exhibit superantigenic properties. Whereas the virulence of several of them is well documented, their exact biological effects are not fully understood. Exotoxins may influence the immune and inflammatory state of various organs, including the sinonasal mucosa: their possible involvement in chronic rhinosinusitis has been suggested and is one of the main trends in current research. The aim of this study was to investigate whether the presence of any of the 22 currently known staphylococcal exotoxin genes could be correlated with chronic rhinosinusitis.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a prospective, multi-centred European study, analysing 93 Staphylococcus aureus positive swabs taken from the middle meatus of patients suffering from chronic rhinosinusitis, with or without nasal polyposis, and controls. Strains were systematically tested for the presence of the 22 currently known exotoxin genes and genotyped according to their agr groups. No direct correlation was observed between chronic rhinosinusitis, with or without nasal polyposis, and either agr groups or the presence of the most studied exotoxins genes (egc, sea, seb, pvl, exfoliatins or tsst-1). However, genes for enterotoxins P and Q were frequently observed in nasal polyposis for the first time, but absent in the control group. The number of exotoxin genes detected was not statistically different among the 3 patient groups.

CONCLUSIONS/SIGNIFICANCE

Unlike many previous studies have been suggesting, we did not find any evident correlation between staphylococcal exotoxin genes and the presence or severity of chronic rhinosinusitis with or without nasal polyposis.

Fatal cases of Staphylococcus aureus pleural empyema in infants

Community-associated infections and especially pleural empyema due to Staphylococcus aureus are increasing worldwide. The virulence of staphylococcal strains is notably determined by different toxin expressing-genes, such as the Panton-Valentine leukocidin (PVL) gene found in S. aureus isolates obtained from pediatric necrotizing pneumonia samples. We describe 2 similar cases of infants with severe respiratory distress and death after an upper respiratory tract infection, having occurred in the same urban area during the same winter time. Necropsies performed between November 2006 and March 2007 revealed bronchopneumonia and an important pleural empyema, justifying the review of clinical charts and laboratory exams. A methicillin-sensitive S. aureus (MSSA) isolate carrying the PVL gene was identified in both cases. We have subsequently cared for an additional case in the same time interval with sudden death and similar pathological findings. No positive microbiological results were obtained, a negative finding possibly related to a 5-day antibiotics regimen. This report describes the pathological features of these cases and stresses the need to recognize PVL-positive S. aureus infections in young children. Finally, we believe that all lethal infections due to PVL-positive S. aureus, independently of the methicillin resistance profile, deserve a mandatory report to the provincial public health authorities.

Severe invasive Panton-Valentine Leucocidin positive Staphylococcus aureus infections in children in London, UK

OBJECTIVE

To describe the features of invasive Panton-Valentine Leucocidin positive Staphylococcus aureus (PVL-SA) in children at a London teaching hospital, from 2004 to 2008.

METHODS

Retrospective case note review.

RESULTS

Eleven previously healthy children, 7 male, median age 9 years (range 7 months-13 years), had invasive infections due to unrelated community-acquired meticillin-sensitive PVL-SA. Possible risk factors were identified in 10 cases. Eight patients had complicated musculoskeletal infections, 2 had pneumonia, and 1 had a massive retropharyngeal abscess. At admission neutropenia was present in 2 patients, deep vein thrombosis in 3, and initial blood cultures were positive in 8. Patients with musculoskeletal involvement had a median of 3 (range 1-6) sites of infection, and required median 5 (range 1-11) operative procedures. Eight patients were admitted to PICU, 7 had septic shock. Median duration of hospital stay was 51 (range 14-255) days. One child died and 5 have long-term morbidity.

CONCLUSIONS

The clinical features of invasive PVL-SA in this series were similar to those reported from USA and Europe. Musculoskeletal infection was the most common manifestation, frequently progressing to multiple sites and severe sepsis. Most cases had risk factors and clinical features which might have allowed earlier diagnosis, and possibly improved outcome.