Mortality Predictive Scores for Community-Acquired Pneumonia in Children

PURPOSE OF REVIEW

The use of severity score for the staging of pneumonias has emerged as a necessity for the physician caring for this disease. Although there are several established prognostic scoring systems for community-acquired pneumonia in adults, the availability for children are scarce.

RECENT FINDINGS

Recently, scoring system for risk stratification of children with pneumonia were developed in low- and middle-income countries. They use clinical variables that represent known risk factors for severe outcomes of respiratory illness in children, such as hypoxemia, chest indrawing, refusal to feed, malnutrition, age, and stage of HIV disease among others factors. Although they showed good discriminating power and are very useful in low-resource settings, the characteristics of the patients, the local epidemiology of concurrent diseases, the social conditions, and the facilities of the hospitals make them not applicable to developed countries. A new prognostic scale for estimating mortality based on the modified PIRO scale used in adults with pneumonia can be useful for developed countries. Although several scoring systems for the estimation of mortality in childhood CAP were developed in the last years, most of them come from developing countries and the results are not applicable to patients with pneumonia in developed countries. Prospective studies applying scores adapted to the reality of the developed countries are needed.

Nuclear PTEN enhances the maturation of a microRNA regulon to limit MyD88-dependent susceptibility to sepsis

Sepsis-induced organ damage is caused by systemic inflammatory response syndrome (SIRS), which results in substantial comorbidities. Therefore, it is of medical importance to identify molecular brakes that can be exploited to dampen inflammation and prevent the development of SIRS. We investigated the role of phosphatase and tensin homolog (PTEN) in suppressing SIRS, increasing microbial clearance, and preventing lung damage. Septic patients and mice with sepsis exhibited increased PTEN expression in leukocytes. Myeloid-specific Pten deletion in an animal model of sepsis increased bacterial loads and cytokine production, which depended on enhanced myeloid differentiation primary response gene 88 (MyD88) abundance and resulted in mortality. PTEN-mediated induction of the microRNAs (miRNAs) miR125b and miR203b reduced the abundance of MyD88. Loss- and gain-of-function assays demonstrated that PTEN induced miRNA production by associating with and facilitating the nuclear localization of Drosha-Dgcr8, part of the miRNA-processing complex. Reconstitution of PTEN-deficient mouse embryonic fibroblasts with a mutant form of PTEN that does not localize to the nucleus resulted in retention of Drosha-Dgcr8 in the cytoplasm and impaired production of mature miRNAs. Thus, we identified a regulatory pathway involving nuclear PTEN-mediated miRNA generation that limits the production of MyD88 and thereby limits sepsis-associated mortality.

Successful rescue combination of extracorporeal membrane oxygenation, high-frequency oscillatory ventilation and prone positioning for the management of severe methicillin-resistant Staphylococcus aureus pneumonia complicated by pneumothorax: a case report and literature review

BACKGROUND

To describe the experience of combination therapy with extracorporeal membrane oxygenation(ECMO), high-frequency oscillatory ventilation(HFOV) and prone positioning in treating severe respiratory failure caused by community acquired methicillin resistant Staphylococcus aureus(CA-MRSA).

CASE PRESENTATION

A 30-year-old female presented with fever and dyspnea for 3 days. She was diagnosed CA-MRSA pneumonia complicated by severe respiratory failure, pneumothorax and neutropenia. Venovenous ECMO was applied within 8 h of the pneumothorax diagnosis. For amelioration of ventilator-induced lung injury, HFOV and prone positioning were combined with ECMO. The patient's condition improved considerably. ECMO was weaned on day 19, and she was discharged on day 48 with good lung recovery.

CONCLUSIONS

To the best of our knowledge, this was the first case in which ECMO was combined with HFOV and prone positioning to treat severe necrotic CA-MRSA pneumonia complicated with pneumothorax. This combination therapy may provide safe respiratory support, may minimize the risk of barotrauma, and provide better drainage of secretions in patients with necrotizing pneumonia.

Characterization of a PVL-negative community-acquired methicillin-resistant Staphylococcus aureus strain of sequence type 88 in China

Sequence type 88 community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strain SR434, isolated from an outpatient with skin and soft tissue infection, was subjected to whole genome sequencing, antimicrobial susceptibility testing, mouse skin infection model and hemolysis analysis to identify its virulence and resistance determinants. MRSA strain SR434 is resistant to clindamycin, erythromycin and fosfomycin. Four plasmids with resistance genes were identified in this strain, including a 20,658bp blaZ-carrying plasmid, a 2473bp ermC-carrying plasmid, a 2622bp fosB7-carrying plasmid (86% identity with plasmid in a ST2590 MRSA strain) and a 4817bp lnuA-carrying plasmid (99% identity with pLNU4 from bovine coagulase-nagetive Staphylococci). This strain contains staphylococcal cassette chromosome mec type IV and does not contain arginine catabolic mobile element or Panton-Valentine-Leukocidin. SR434 harbors genomic islands νSaα, νSaβ, νSaγ and ΦSa3 and pathogenicity islands νSa2 that carries genes encoding toxic shock syndrome toxin 1, superantigen enterotoxin C and superantigen enterotoxin L. Mouse skin infection model results show that SR434 had similar virulence potential causing invasive skin infection as a PVL-negative epidemic Korea clone HL1 (ST72). CA-MRSA strain of ST88 lineage might be a great concern for its high virulence. PVL has limited contribution to virulence phenotype among this lineage.

SOCS1 is a negative regulator of metabolic reprogramming during sepsis

Sepsis can induce an overwhelming systemic inflammatory response, resulting in organ damage and death. Suppressor of cytokine signaling 1 (SOCS1) negatively regulates signaling by cytokine receptors and Toll-like receptors (TLRs). However, the cellular targets and molecular mechanisms for SOCS1 activity during polymicrobial sepsis are unknown. To address this, we utilized a cecal ligation and puncture (CLP) model for sepsis; C57BL/6 mice subjected to CLP were then treated with a peptide (iKIR) that binds the SOCS1 kinase inhibitory region (KIR) and blocks its activity. Treatment with iKIR increased CLP-induced mortality, bacterial burden, and inflammatory cytokine production. Myeloid cell-specific SOCS1 deletion (Socs1Δmyel) mice were also more susceptible to sepsis, demonstrating increased mortality, higher bacterial loads, and elevated inflammatory cytokines, compared with Socs1fl littermate controls. These effects were accompanied by macrophage metabolic reprograming, as evidenced by increased lactic acid production and elevated expression of the glycolytic enzymes hexokinase, lactate dehydrogenase A, and glucose transporter 1 in septic Socs1Δmyel mice. Upregulation was dependent on the STAT3/HIF-1α/glycolysis axis, and blocking glycolysis ameliorated increased susceptibility to sepsis in iKIR-treated CLP mice. These results reveal a role of SOCS1 as a regulator of metabolic reprograming that prevents overwhelming inflammatory response and organ damage during sepsis.

Life-threatening MRSA sepsis with bilateral pneumonia, osteomyelitis, and septic arthritis of the knee in a previously healthy 13-year-old boy: a case report

The incidence and severity of methicillin resistant Staphylococcus aureus (MRSA) infections are increasing and cause high mortality and morbidity. We describe the first pediatric case in Scandinavia with Panton-Valentine leucocidin (PVL) positive MRSA septicemia who developed bilateral pneumonia, arthritis of the knee, and osteomyelitis of the tibia. Radiological investigation and interpretation directed the treatment, especially the surgical debridement, and combined with clinical and biochemical findings lead to close interdisciplinary treatment with frequent surgical interventions and antimicrobial combination therapy. The outcome was a healthy patient without sequelae, a favorable course unlike those previously described in the literature. This case underlines the necessity of a close interdisciplinary cooperation in children with severe MRSA infection encompassing pneumonia, septic arthritis, and osteomyelitis, using different imaging modalities to guide the surgical and antibiotic treatment.

Control of adaptive immune responses by Staphylococcus aureus through IL-10, PD-L1, and TLR2

Microbes induce innate immune responses in hosts. It is critical to know how different microbes control adaptive responses through innate pathways. The impact of gram-positive bacteria on the innate and adaptive responses is unclear. Herein we report that Staphylococcus aureus induces IL-10, Th17-inducing cytokines IL-6 and IL-23, chemokines, and regulates dendritic cell markers. S. aureus inhibits T-cell IL-2 responses through modulation of HLA-DR, CD86 and PD-L1. IFN-gamma, Src kinase inhibitors, or TLR2 antibodies prevented the down-modulation of HLA-DR by S. aureus. Our data demonstrate that innate TLR signaling induces multi-dimensional inhibition of adaptive immune responses, which may contribute to the lack of protective immunity to bacteria or microbe tolerance. IL-10 and PD-L1 antagonists may boost immunity to vaccines for S. aureus and other microbes.

[Staphylococcus aureus infections in the intensive care unit: clinical and epidemiological characteristics]

INTRODUCTION

There has been an increase in invasive Staphylococcus Aureus infections over the last few years, which have required admission to the pediatric intensive care unit (PICU).

PATIENTS AND METHODS

All patients with S. aureus infection who were admitted to PICU were enrolled in a retrospective study (January 2006-June 2010). The patients were classified into 2 groups: community-acquired infection (Group 1) and nosocomial infection (Group 2). We recorded epidemiological data, type of S. aureus (methicillin-susceptible S. aureus [MSSA], methicillin-resistant S. aureus [MRSA]), risk factors, site of infection, presence of hemodynamic instability, respiratory support, and mortality.

RESULTS

A total of 51 patients were enrolled, 21 belonging to Group 1 and 30 to Group 2. The median age was lower in Group 1 (1.6 years vs 3.2 years; P=.009). MSSA was isolated in 88% of cases. MRSA was detected in 6/51 (12%) of cases, which were isolated in the later study period (January 2009-June 2010). The risk factors for infection were: immunosuppression, venous catheter, institutionalization, mechanical ventilation, previous surgery, previous trauma and chronic osteomyelitis. A large majority (83%) of the patients with MRSA infection had risk factors. The type of infection was varied, with respiratory tract infection being the most common (75%). Hemodynamic instability was observed in 43% of patients. Most patients (86%) required respiratory support. One patient in Group 1 died of necrotizing pneumonia caused by MSSA.

CONCLUSIONS

Infections by S. aureus in children are severe and have a high morbidity. Respiratory infection was the most common in our series. Isolation of MSSA is common in these infections, although, an increase in the number of infections by MRSA was observed during the latter part of the study.

Antibiotic therapy for pediatric community-acquired pneumonia: do we know when, what and for how long to treat?

Community-acquired pneumonia (CAP) is a common cause of morbidity among children in developed countries and accounts for an incidence of 10-40 cases per 1000 children in the first 5 years of life. Given the clinical, social and economic importance of CAP, there is general agreement that prompt and adequate therapy is essential to reduce the impact of the disease. The aim of this discussion paper is to consider critically the available data concerning the treatment of uncomplicated pediatric CAP and to consider when, how and for how long it should be treated. This review has identified the various reasons that make it difficult to establish a rational approach to the treatment of pediatric CAP, including the definition of CAP, the absence of a pediatric CAP severity score, the difficulty of identifying the etiology, limited pharmacokinetic (PK)/pharmacodynamic (PD) studies, the high resistance of the most frequent respiratory pathogens to the most widely used anti-infectious agents and the lack of information concerning the changes in CAP epidemiology following the introduction of new vaccines against respiratory pathogens. More research is clearly required in various areas, such as the etiology of CAP and the reasons for its complications, the better definition of first- and second-line antibiotic therapies (including the doses and duration of parenteral and oral antibiotic treatment), the role of antiviral treatment and on how to follow-up patients with CAP. Finally, further efforts are needed to increase vaccination coverage against respiratory pathogens and to conduct prospective studies of their impact.

Predictors of mortality in Staphylococcus aureus Bacteremia

Staphylococcus aureus bacteremia (SAB) is an important infection with an incidence rate ranging from 20 to 50 cases/100,000 population per year. Between 10% and 30% of these patients will die from SAB. Comparatively, this accounts for a greater number of deaths than for AIDS, tuberculosis, and viral hepatitis combined. Multiple factors influence outcomes for SAB patients. The most consistent predictor of mortality is age, with older patients being twice as likely to die. Except for the presence of comorbidities, the impacts of other host factors, including gender, ethnicity, socioeconomic status, and immune status, are unclear. Pathogen-host interactions, especially the presence of shock and the source of SAB, are strong predictors of outcomes. Although antibiotic resistance may be associated with increased mortality, questions remain as to whether this reflects pathogen-specific factors or poorer responses to antibiotic therapy, namely, vancomycin. Optimal management relies on starting appropriate antibiotics in a timely fashion, resulting in improved outcomes for certain patient subgroups. The roles of surgery and infectious disease consultations require further study. Although the rate of mortality from SAB is declining, it remains high. Future international collaborative studies are required to tease out the relative contributions of various factors to mortality, which would enable the optimization of SAB management and patient outcomes.

The management of community-acquired pneumonia in infants and children older than 3 months of age: clinical practice guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America

Evidenced-based guidelines for management of infants and children with community-acquired pneumonia (CAP) were prepared by an expert panel comprising clinicians and investigators representing community pediatrics, public health, and the pediatric specialties of critical care, emergency medicine, hospital medicine, infectious diseases, pulmonology, and surgery. These guidelines are intended for use by primary care and subspecialty providers responsible for the management of otherwise healthy infants and children with CAP in both outpatient and inpatient settings. Site-of-care management, diagnosis, antimicrobial and adjunctive surgical therapy, and prevention are discussed. Areas that warrant future investigations are also highlighted.

Transcription and translation products of the cytolysin gene psm-mec on the mobile genetic element SCCmec regulate Staphylococcus aureus virulence

The F region downstream of the mecI gene in the SCCmec element in hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) contains two bidirectionally overlapping open reading frames (ORFs), the fudoh ORF and the psm-mec ORF. The psm-mec ORF encodes a cytolysin, phenol-soluble modulin (PSM)-mec. Transformation of the F region into the Newman strain, which is a methicillin-sensitive S. aureus (MSSA) strain, or into the MW2 (USA400) and FRP3757 (USA300) strains, which are community-acquired MRSA (CA-MRSA) strains that lack the F region, attenuated their virulence in a mouse systemic infection model. Introducing the F region to these strains suppressed colony-spreading activity and PSMα production, and promoted biofilm formation. By producing mutations into the psm-mec ORF, we revealed that (i) both the transcription and translation products of the psm-mec ORF suppressed colony-spreading activity and promoted biofilm formation; and (ii) the transcription product of the psm-mec ORF, but not its translation product, decreased PSMα production. These findings suggest that both the psm-mec transcript, acting as a regulatory RNA, and the PSM-mec protein encoded by the gene on the mobile genetic element SCCmec regulate the virulence of Staphylococcus aureus.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

A comparison of risk factors associated with community-associated methicillin-resistant and -susceptible Staphylococcus aureus infections in remote communities

In this case-control study, cases [community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), n=79] and controls [community-associated methicillin-susceptible S. aureus (CA-MSSA), n=36] were defined as a laboratory-confirmed infection in a patient with no previous hospital-associated factors. Skin and soft tissue were the predominant sites of infection, both for cases (67·1%) and controls (55·6%). Most of the cases (79·7%) and controls (77·8%) were aged <30 years. Investigations did not reveal any significant statistical differences in acquiring a CA-MRSA or CA-MSSA infection. The most common shared risk factors included overcrowding, previous antibiotic usage, existing skin conditions, household exposure to someone with a skin condition, scratches/insect bites, and exposure to healthcare workers. Similar risk factors, identified for both CA-MRSA and CA-MSSA infections, suggest standard hygienic measures and proper treatment guidelines would be beneficial in controlling both CA-MRSA and CA-MSSA in remote communities.

Severe invasive community-associated methicillin-resistant Staphylococcus aureus infections in previously healthy children

OBJECTIVE

An increase in community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections has been reported in the literature. Most severe, life-threatening infections were previously thought to be associated with chronically ill or frail patients. Our pediatric intensive care unit (PICU) has seen a recent dramatic increase in primary, severe invasive CA-MRSA infections in healthy children.

DESIGN/SETTING

A retrospective chart review of all previously healthy patients admitted to our 19-bed combined medical-surgical PICU with a primary diagnosis of severe invasive, culture-proven CA-MRSA disease during the past 6 years.

RESULTS

Eleven previously healthy patients were admitted to our PICU with severe, primary, invasive CA-MRSA infections from March 2006 through September 2007, in contrast to no patients meeting these criteria in the preceding 5 years. The mortality rate was 27%, compared with an overall PICU mortality rate during the study period of <7%. The mean PICU length of stay of these patients was 14.9 days, compared with an average PICU length of stay of 2.4 days. Despite initiation of treatment with vancomycin at admission to the PICU in all but one case, patients took a mean of 5.7 days to convert to negative blood cultures. Eight patients had bacteremia longer than 4 days. Six of the patients developed bilateral necrotizing pneumonia requiring prolonged mechanical ventilation.

CONCLUSIONS

Severe CA-MRSA infections in healthy children are increasing at an alarming rate in our institution. This acute rise in incidence, coupled with an alarmingly high associated mortality rate, raises important questions about the initial empirical antibiotic therapy we use in caring for patients presenting with suspected life-threatening CA-MRSA disease. Vancomycin monotherapy may not be adequate treatment for severe CA-MRSA infections.

Impact of antimicrobial resistance on the treatment and outcome of patients with sepsis

Antimicrobial therapy is one of the main stones of sepsis therapy. A recent study of septic shock patients showed that each hour of delay in antimicrobial administration during the ensuing 6 h after the onset of hypotension was associated with a decrease in survival rates. However, many questions regarding the impact of infection caused by antimicrobial-resistant pathogens on the mortality of patients with sepsis still need to be clarified. There is a lack of fair studies in the literature. Most studies have had inadequate sample size, inadequate adjustment for predictors of adverse outcomes, and inadequate definition of appropriate antibiotic therapy. Despite the fact that appropriate therapy is essential to treat sepsis, it seems that severity of underlying diseases and comorbidities are more important than resistance, although the studies were not well designed to examine the real impact of resistance on outcome. Finally, new technologies such as microarray that can identify different microorganisms, genes of resistance, and virulence in a few hours might have a great impact on the treatment of sepsis due to antimicrobial-resistant pathogens in the future.

Using innate immunity to characterize the host response to microbial invasion in severe sepsis

Severe sepsis is a life-threatening systemic inflammatory response to microbial infection. Although mortality from severe sepsis has decreased modestly over the past three decades, its incidence is increasing dramatically. Current treatment of severe sepsis relies primarily on identification and appropriate antibiotic coverage of the invading pathogen, with supportive therapies aimed primarily at reducing the risk of associated organ injury. Current efforts to identify the invading pathogens are successful in approximately only 50% of patients with severe sepsis. In this review, we examine host-pathogen interactions through the Toll-like receptors and Nod signaling systems as principal mechanisms of the innate immune response, and explore the application of high-throughput genomic technologies that have permitted a more complete dissection of the innate immune response during severe sepsis. Early controlled studies suggest that these genome-wide tools can readily identify pathogen-specific host responses in macrophages and dendritic cells. However, despite considerable progress, clinical application of these approaches to pathogen recognition in hospitalized patients with severe sepsis is still years away.

Complementary analysis of the vegetative membrane proteome of the human pathogen Staphylococcus aureus

The Gram-positive bacterium Staphylococcus aureus is a serious human pathogen causing a wide variety of diseases, and its increasing resistance toward all available antibiotics makes its further investigation absolutely essential. We examined the membrane proteome of exponentially growing cells of S. aureus COL because this subproteome plays a major role in the virulence of the bacterium in its host. In general, an analysis of membrane proteins is impeded by their hydrophobic nature as well as by a high abundance of many cytosolic proteins. The implementation of three different technologies, one-dimensional gel-LC, two-dimensional LC, and a membrane shaving approach combined with MS/MS analyses, enabled an identification of 271 integral and 86 peripheral membrane proteins from exponentially growing cells. In particular, the latter approach that combined membrane shaving with a subsequent chymotrypsin digest of integral membrane domains of proteins greatly facilitated the detection of hydrophobic peptides derived from membrane-spanning segments (713 peptides, 60% of all peptides) and therefore yielded almost exclusively highly hydrophobic integral membrane proteins (96.7%). A comparison of the various methods disclosed the one-dimensional gel-LC and the shaving approach to be highly complementary techniques. A combination of them will reveal a most comprehensive view on membrane proteomes.

Antimicrobial-resistant pathogens: an emerging pediatric threat

The clinical impact of these three bacterial threats is readily apparent to any who practice pediatrics. The potential virulence of CA-MRSA and MDR pneumococci and the threat of failed antimicrobial options for MDRGN pose enormous challenges now and in the near future. With careful attention to antimicrobial stewardship, however, and knowledge of the clinical and epidemiologic factors of these organisms, one can hope to mitigate the impact on patient care and outcomes while awaiting ongoing discovery of new antimicrobial options. Most important, however, will be careful and thoughtful management of any new antimicrobial products to protect their efficacy for the future.