Why is the rate of pneumococcal pneumonia declining?

Methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa community acquired pneumonia: Prevalence and locally derived risk factors in a single hospital system

Objectives

Current American Thoracic Society/Infectious Disease Society of America (ATS/IDSA) community-acquired pneumonia (CAP) guidelines expand the CAP definition to include infections occurring in patients with recent health care exposure. The guidelines now recommend that hospital systems determine their own local prevalence and predictors of Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) among patients satisfying this new broader CAP definition. We sought to carry out these recommendations in our system, focusing on the emergency department, where CAP diagnosis and initial empiric antibiotic selection usually ooccur.

Methods

We performed a retrospective cohort study of patients admitted with CAP through any of 3 EDs in our hospital system in Northern California between November 2019 and October 2021. Inclusion criteria included an ED admission diagnosis of pneumonia or sepsis, fever or hypothermia, leukocytosis or leukopenia, and consistent chest imaging result. SARS-CoV-2-positive cases were excluded. We abstracted variables historically associated with P. aeruginosa and MRSA. Outcome measures were prevalence of P. aeruginosa and MRSA in the overall clinically defined cohort and among microbiologically confirmed cases and predictors of P. aeruginosa or MRSA isolation, as determined by univariate logistic regression, bootstrapped least absolute shrinkage and selection operator, and random forest analyses. Additionally, we describe the iterative process used and challenges encountered in carrying out the new ATS/IDSA guideline recommendations.

Results

There were 1133 unique patients who satisfied our definition of clinically defined CAP, of whom 109 (9.6%) had a bacterial pathogen isolated. There were 24 P. aeruginosa isolates and 11 MRSA isolates in 33 patients. Thus, the prevalence P. aeruginosa and MRSA was 2.9% in the overall CAP cohort, but 30.3% in the microbiologically confirmed cohort. The most important predictors of either P. aeruginosa or MRSA isolation were tracheostomy (odds ratio [OR] 22.08; 95% confidence interval [CI] 10.39-46.96) and gastrostomy tube (OR 14.7; 95% CI 7.14-30.26). Challenges included determining the suspected infection type in patients admitted simply for "sepsis"; interpreting dictated radiology reports; determining functional status, presence of indwelling lines and tubes, and long-term care facility residence from the electronic health record; and correctly attributing culture results to pneumonia.

Conclusion

Prevalence of MRSA and P. aeruginosa was low among patients admitted in our medical system with CAP - now broadly defined - but high among those with a microbiologically confirmed bacterial etiology. Our locally derived predictors of MRSA and P. aeruginosa can be used to aid our emergency physicians in empiric antibiotic selection for CAP. Findings from this project might inform efforts at other institutions.

Impact of vaccination on the epidemiology and prognosis of pneumonia

Adults with lung diseases, comorbidities, smokers, and elderly are at risk of lung infections and their consequences. Community-acquired pneumonia happen in more than 1% of people each year. Possible pathogens of community-acquired pneumonia include viruses, pneumococcus and atypicals. The CDC recommend vaccination throughout life to provide immunity, but vaccination rates in adults are poor. Tetravalent and trivalent influenza vaccine is designed annually during the previous summer for the next season. The available vaccines include inactivated, adjuvant, double dose, and attenuated vaccines. Their efficacy depends on the variant of viruses effectively responsible for the outbreak each year, and other reasons. Regarding the pneumococcal vaccine, there coexist the old polysaccharide 23-valent vaccine with the new conjugate 10-valent and 13-valent conjugate vaccines. Conjugate vaccines demonstrate their usefulness to reduce the incidence of pneumococcal pneumonia due to the serotypes present in the vaccine. Whooping cough is still present, with high morbidity and mortality rates in young infants. Adult's pertussis vaccine is available, it could contribute to the control of whooping cough in the most susceptible, but it is not present yet in the calendar of adults around the world. About 10 vaccines against SARS-CoV-2 have been developed in a short time, requiring emergency use authorization. A high rate of vaccination was observed in most of the countries. Booster doses became frequent after the loss of effectiveness against new variants. The future of this vaccine is yet to be written.

Unfortunate Outcomes in Patients With SARS-CoV-2 Superimposed on Pneumococcal Pneumonia

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the disease it causes, coronavirus disease 2019 (COVID-19), continue to have socioeconomic as well as health implications worldwide. The virus has already led to over 200,000 deaths in the United States alone. This is most likely secondary to quick respiratory deterioration seen in patients inflicted with the virus. In other words, the heightened inflammatory response leads to major organ system damage, which leads to rapid decompensation of the patient's clinical condition. Interestingly enough, some patients present with both the novel virus as well as a superimposed bacterial infection that further complicates the management of the disease. We present a case of a patient with a positive polymerase chain reaction (PCR) test for SARS-CoV-2 as well as a pneumococcal urine antigen; he was treated with both appropriate antibiotics as well as dexamethasone and remdesivir for pneumonia and novel virus, respectively. The patient's hypoxemia continued to worsen with appropriate means of oxygenation and eventually led to cardiac arrest.

Incidence, trends, and outcomes of infection sites among hospitalizations of sepsis: A nationwide study

Purpose

To determine the trends of infection sites and outcome of sepsis using a national population-based database.

Materials and methods

Using the Nationwide Inpatient Sample database of the US, adult sepsis hospitalizations and infection sites were identified using a validated approach that selects admissions with explicit ICD-9-CM codes for sepsis and diagnosis/procedure codes for acute organ dysfunctions. The primary outcome was the trend of incidence and in-hospital mortality of specific infection sites in sepsis patients. The secondary outcome was the impact of specific infection sites on in-hospital mortality.

Results

During the 9-year period, we identified 7,860,687 admissions of adult sepsis. Genitourinary tract infection (36.7%), lower respiratory tract infection (36.6%), and systemic fungal infection (9.2%) were the leading three sites of infection in patients with sepsis. Intra-abdominal infection (30.7%), lower respiratory tract infection (27.7%), and biliary tract infection (25.5%) were associated with highest mortality rate. The incidences of all sites of infections were trending upward. Musculoskeletal infection (annual increase: 34.2%) and skin and skin structure infection (annual increase: 23.0%) had the steepest increase. Mortality from all sites of infection has decreased significantly (trend p<0.001). Skin and skin structure infection had the fastest declining rate (annual decrease: 5.5%) followed by primary bacteremia (annual decrease: 5.3%) and catheter related bloodstream infection (annual decrease: 4.8%).

Conclusions

The anatomic site of infection does have a differential impact on the mortality of septic patients. Intra-abdominal infection, lower respiratory tract infection, and biliary tract infection are associated with higher mortality in septic patients.

Progress in mucosal immunization for protection against pneumococcal pneumonia

Introduction: Lower respiratory tract infections are the fourth cause of death worldwide and pneumococcus is the leading cause of pneumonia. Nonetheless, existing pneumococcal vaccines are less effective against pneumonia than invasive diseases and serotype replacement is a major concern. Protein antigens could induce serotype-independent protection, and mucosal immunization could offer local and systemic immune responses and induce protection against pneumococcal colonization and lung infection. Areas covered: Immunity induced in the experimental human pneumococcal carriage model, approaches to address the physiological barriers to mucosal immunization and improve delivery of the vaccine antigens, different strategies already tested for pneumococcal mucosal vaccination, including live recombinant bacteria, nanoparticles, bacterium-like particles, and nanogels as well as, nasal, pulmonary, sublingual and oral routes of vaccination. Expert opinion: The most promising delivery systems are based on nanoparticles, bacterial-like particles or nanogels, which possess greater immunogenicity than the antigen alone and are considered safer than approaches based on living cells or toxoids. These particles can protect the antigen from degradation, eliminating the refrigeration need during storage and allowing the manufacture of dry powder formulations. They can also increase antigen uptake, control release of antigen and trigger innate immune responses.

Common Genetic Variants in the Complement System and their Potential Link with Disease Susceptibility and Outcome of Invasive Bacterial Infection

Streptococcus pneumoniae and Neisseria meningitidis are pathogens that frequently colonize the nasopharynx in an asymptomatic manner but are also a cause of invasive bacterial infections mainly in young children. The complement system plays a crucial role in humoral immunity, complementing the ability of antibodies to clear microbes, thereby protecting the host against bacterial infections, including S. pneumoniae and N. meningitidis. While it is widely accepted that complement deficiencies due to rare genetic variants increase the risk for invasive bacterial infection, not much is known about the common genetic variants in the complement system in relation to disease susceptibility. In this review, we provide an overview of the effects of common genetic variants on complement activation and on complement-mediated inflammation.