Pediatric case of fatal necrotizing pneumonia due to Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus in Spain

Staphylococcus aureus Community-acquired Pneumonia in Children After 13-Valent Pneumococcal Vaccination (2008-2018): Epidemiology, Clinical Characteristics and Outcomes

BACKGROUND

The epidemiology of community-acquired pneumonia (CAP) has changed, influenced by sociosanitary conditions and vaccination status. We aimed to analyze the recent epidemiology of bacterial CAP in hospitalized children in a setting with high pneumococcal vaccination coverage and to describe the clinical characteristics of pediatric Staphylococcus aureus CAP.

METHODS

Children <17 years old hospitalized from 2008 to 2018 with bacterial CAP in 5 tertiary hospitals in Spain were included. Cases with pneumococcal CAP were randomly selected as comparative group following a case-control ratio of 2:1 with S. aureus CAP.

RESULTS

A total of 313 bacterial CAP were diagnosed: Streptococcus pneumoniae CAP (n = 236, 75.4%), Streptococcus pyogenes CAP (n = 43, 13.7%) and S. aureus CAP (n = 34, 10.9%). Throughout the study period, the prevalence of S. pyogenes increased (annual percentage change: +16.1% [95% CI: 1.7-32.4], P = 0.031), S. pneumoniae decreased (annual percentage change: -4.4% [95 CI: -8.8 to 0.2], P = 0.057) and S. aureus remained stable. Nine isolates of S. aureus (26.5%) were methicillin-resistant. Seventeen cases (50%) with S. aureus CAP had some pulmonary complication and 21 (61.7%) required intensive care. S. pneumoniae CAP showed a trend toward higher prevalence of pulmonary complications compared with S. aureus CAP (69.1% vs. 50.0%, P = 0.060), including higher frequency of pulmonary necrosis (32.4% vs. 5.9%, P = 0.003).

CONCLUSIONS

The incidence of S. aureus CAP in children remained stable, whereas the prevalence of pneumococcal CAP decreased and S. pyogenes CAP increased. Patients with S. aureus presented a high frequency of severe outcomes, but a lower risk of pulmonary complications than patients with S. pneumoniae.

Exploring Virulence Factors and Alternative Therapies against Staphylococcus aureus Pneumonia

Pneumonia is an acute pulmonary infection associated with high mortality and an immense financial burden on healthcare systems. Staphylococcus aureus is an opportunistic pathogen capable of inducing S. aureus pneumonia (SAP), with some lineages also showing multidrug resistance. Given the high level of antibiotic resistance, much research has been focused on targeting S. aureus virulence factors, including toxins and biofilm-associated proteins, in an attempt to develop effective SAP therapeutics. Despite several promising leads, many hurdles still remain for S. aureus vaccine research. Here, we review the state-of-the-art SAP therapeutics, highlight their pitfalls, and discuss alternative approaches of potential significance and future perspectives.

Panton-valentine leucocidin carrying Staphylococcus aureus causing necrotizing pneumonia inactivates the JAK/STAT signaling pathway and increases the expression of inflammatory cytokines

PURPOSE

Methicillin-resistant Staphylococcus aureus (MRSA) carrying Panton-Valentine leukocidin, a pore-forming toxin, is a common cause of necrotizing pneumonia. However, the early pulmonary inflammatory response following PVL(+) MRSA infection is unknown. The purpose of this study was to use a murine model to determine the effect of PVL(+) MRSA on lung tissues and the expression of cytokines and JAK and STAT mRNA and protein.

METHODS

Mice were randomly divided into 3 groups and intra-nasally treated with PBS (control group), recombinant PVL (rPVL group), and PVL(+) MRSA (PVL group). At 24 and 48 h after inoculation, bronchoalveolar lavage fluid (BALF) was tested for cytokine levels, and lung tissues were tested for JAK and STAT mRNA and protein expression, and examined after hematoxylin and eosin staining.

RESULTS

Mice infected with the PVL(+) strain became ill, characterized by impaired mobility, hunched posture, ruffled fur, and labored breathing. Lung tissue exhibited tissue necrosis and hemorrhage. BALF levels of IL-8, TNF-α, IFN-γ, IL-12, sICAM-1, and sVCAM-1 were increased in the rPVL or PVL groups, while levels of IL-10 and IL-4 levels were similar among the groups. JAK1 and STAT1 mRNA expression and protein levels were increased in lung tissue from mice infected with PVL(+) MRSA and rPVL.

CONCLUSIONS

PVL is a significant S. aureus virulence factor, and upregulates the expression of proinflammatory cytokines but does not affect the expression of anti-inflammatory cytokines. The effect of PVL may be due to JAK/STAT pathway activation. Blockade of the JAK/STAT pathway may decrease the severity of PVL(+) MRSA pneumonia.