The Hospitalist Perspective on Treatment of Community–Acquired Bacterial Pneumonia

Isorhamnetin as a novel inhibitor of pneumolysin against Streptococcus pneumoniae infection in vivo/in vitro

The increasing incidence of Streptococcus pneumoniae (S. pneumoniae) infection severely threatened the global public heath, causing a significant fatality in immunocompromised hosts. Notably, pneumolysin (PLY) as a pore-forming cytolysin plays a crucial role in the pathogenesis of pneumococcal pneumonia and lung injury. In this study, a natural flavonoid isorhamnetin was identified as a PLY inhibition to suppress PLY-induced hemolysis by engaging the predicted residues and attenuate cytolysin PLY-mediated A549 cells injury. Underlying mechanisms revealed that PLY inhibitor isorhamnetin further contributed to decrease the formation of bacterial biofilms without affecting the expression of PLY. In vivo S. pneumoniae infection confirmed that the pathological injury of lung tissue evoked by S. pneumoniae was ameliorated by isorhamnetin treatment. Collectively, these results presented that isorhamnetin could inhibit the biological activity of PLY, thus reducing the pathogenicity of S. pneumoniae. In summary, our study laid a foundation for the feasible anti-virulence strategy targeting PLY, and provided a promising PLY inhibitor for the treatment of S. pneumoniae infection.

Diagnostic and Prognostic Roles of Procalcitonin and Other Tools in Community-Acquired Pneumonia: A Narrative Review

Community-acquired pneumonia (CAP) is among the most common causes of death and one of the leading healthcare concerns worldwide. It can evolve into sepsis and septic shock, which have a high mortality rate, especially in critical patients and comorbidities. The definitions of sepsis were revised in the last decade as "life-threatening organ dysfunction caused by a dysregulated host response to infection". Procalcitonin (PCT), C-reactive protein (CRP), and complete blood count, including white blood cells, are among the most commonly analyzed sepsis-specific biomarkers also used in pneumonia in a broad range of studies. It appears to be a reliable diagnostic tool to expedite care of these patients with severe infections in the acute setting. PCT was found to be superior to most other acute phase reactants and indicators, including CRP as a predictor of pneumonia, bacteremia, sepsis, and poor outcome, although conflicting results exist. In addition, PCT use is beneficial to judge timing for the cessation of antibiotic treatment in most severe infectious states. The clinicians should be aware of strengths and weaknesses of known and potential biomarkers in expedient recognition and management of severe infections. This manuscript is intended to present an overview of the definitions, complications, and outcomes of CAP and sepsis in adults, with special regard to PCT and other important markers.

A Hospital-Based and Cross-Sectional Investigation on Clinical Characteristics of Pediatric Streptococcus pneumoniae Isolates in Beijing from 2015 to 2021

Introduction

Streptococcus pneumoniae (S. pneumoniae) is a major pathogen causing death in children. Few studies have evaluated the importance of S. pneumoniae in the identified bacteria in clinical work. This retrospective study aimed to reveal the rank of S. pneumoniae in determined bacteria isolated from children in Beijing, China, as well as the antimicrobial resistance of this pathogen.

Methods

The number of specimen for bacterial culture and of bacterial species were cumulated and ranked based on the data of the two largest children's hospitals in Beijing from 2015 to 2021. The temporal change of S. pneumoniae culture, as well as the clinical data of S. pneumoniae isolates were collected and analyzed. The minimum inhibitory concentrations of antimicrobial agents were determined by BD Phoenix 100 automated system or Vitek 2 automated system for antimicrobial susceptibility testing. The breakpoints recommended by CLSI were adopted.

Results

During the 7-year study period, a total of 45,631 bacterial isolates were cultured from 462,144 submitted specimens, in which S. pneumoniae was the third frequent agent following S. aureus and H. influenza, and accounting for 8.79% of the isolates (4011/45,631). In the 4011 S. pneumoniae isolates, 2239 and 997 ones were, respectively, isolated from sputum and bronchial lavage fluid. Most of S. pneumoniae strains were identified in winter (34.7%) and spring (26.1%), and were mainly isolated from patients under 5 years old (77.1%). Low susceptible rate (27.6%) of CSF isolates was determined to penicillin according to the parenteral meningitis breakpoints, while high susceptible rate (56.9%) of non-CSF isolates was obtained according to the parenteral non-meningitis breakpoints. The isolates showed low sensitivity to erythromycin and tetracycline (<5%). All isolates were susceptible to vancomycin and linezolid.

Conclusion

The present results demonstrated that S. pneumoniae was one of the most commonly detected bacteria in current pediatric clinical tests, especially in young children under 5 years old, which emphasized the importance of prevention. Penicillin could still be the first empiric choice to treat non-meningitis pneumococcal infections, while erythromycin should not be involved in the treatment.

In Vitro and In Vivo Properties of CUO246, a Novel Bacterial DNA Gyrase/Topoisomerase IV Inhibitor

CUO246, a novel DNA gyrase/topoisomerase IV inhibitor, is active in vitro against a broad range of Gram-positive, fastidious Gram-negative, and atypical bacterial pathogens and retains activity against quinolone-resistant strains in circulation. The frequency of selection for single step mutants of wild-type S. aureus with reduced susceptibility to CUO246 was <4.64 × 10^-9 at 4× and 8× MIC and remained low when using an isogenic QRDR mutant (<5.24 × 10^-9 at 4× and 8× MIC). Biochemical assays indicated that CUO246 had potent inhibitory activity against both DNA gyrase (GyrAB) and topoisomerase IV (ParCE). Furthermore, CUO246 showed rapid bactericidal activity in time-kill assays and potent in vivo efficacy against S. aureus in a neutropenic murine thigh infection model. These results suggest that CUO246 may be useful in treating infections by various causative agents of acute skin and skin structure infections, respiratory tract infections, and sexually transmitted infections.

Molecular Characterization of Predominant Serotypes, Drug Resistance, and Virulence Genes of Streptococcus pneumoniae Isolates From East China

Streptococcus pneumoniae is a common diplococcus pathogen found worldwide. The characterization of predominant serotypes, drug resistance, and virulence genes of S. pneumoniae isolates prevailing in different areas and countries is clinically important for choice of antibiotics and improvement of vaccines. In this study, pneumonia (78.7%) and meningitis (37.0%) were the predominant diseases observed in the 282 (children) and 27 (adults) S. pneumoniae-infected patients (p < 0.05) from seven hospitals in different areas of East China. Of the 309 pneumococcal isolates, 90.3% were classified by PCR into 15 serotypes, with serotypes 19F (27.2%) and the 6A/B (19.1%) being most predominant (p < 0.05). Importantly, serotypes 15A and 15B/C combined for a total of 10.4% of the isolates, but these serotypes are not included in the 13-valent pneumococcal capsule conjugate vaccine used in China. Antimicrobial susceptibility analysis by the E-test showed that >95% of the 309 pneumococcal isolates were susceptible to moxifloxacin and levofloxacin, as well as 18.4, 85.8, and 81.6% of the isolates displayed susceptibility to penicillin, cefotaxime, and imipenem, respectively. A significant correlation between the prevalence of predominant serotypes and their penicillin resistance was observed (p < 0.05). In particular, >95% of all the pneumococcal isolates showed resistance to erythromycin and azithromycin. Of the nine detected virulence genes, the lytA, ply, hysA, and nanA were the most common with 95–100% positive rates in the 309 pneumococcal isolates, while the pavA and psaA genes displayed a significant correlation with pneumococcal bacteremia and meningitis (p < 0.05). Overall, our data suggested that the predominant serotypes, drug resistance, and virulence genes of the S. pneumoniae isolates prevailing in East China are distinct from those observed in other areas of China and adjacent countries.

Dysregulation of Streptococcus pneumoniae zinc homeostasis breaks ampicillin resistance in a pneumonia infection model

Streptococcus pneumoniae is the primary cause of community-acquired bacterial pneumonia with rates of penicillin and multidrug-resistance exceeding 80% and 40%, respectively. The innate immune response generates a variety of antimicrobial agents to control infection, including zinc stress. Here, we characterize the impact of zinc intoxication on S. pneumoniae, observing disruptions in central carbon metabolism, lipid biogenesis, and peptidoglycan biosynthesis. Characterization of the pivotal peptidoglycan biosynthetic enzyme GlmU indicates a sensitivity to zinc inhibition. Disruption of the sole zinc efflux pathway, czcD, renders S. pneumoniae highly susceptible to β-lactam antibiotics. To dysregulate zinc homeostasis in the wild-type strain, we investigated the safe-for-human-use ionophore 5,7-dichloro-2-[(dimethylamino)methyl]quinolin-8-ol (PBT2). PBT2 rendered wild-type S. pneumoniae strains sensitive to a range of antibiotics. Using an invasive ampicillin-resistant strain, we demonstrate in a murine pneumonia infection model the efficacy of PBT2 + ampicillin treatment. These findings present a therapeutic modality to break antibiotic resistance in multidrug-resistant S. pneumoniae.

Early detection of drug-resistant Streptococcus pneumoniae and Haemophilus influenzae by quantitative flow cytometry

Early detection of drug resistance contributes to combating drug-resistant bacteria and improving patient outcomes. Microbial testing in the laboratory is essential for treating infectious diseases because it can provide critical information related to identifying pathogenic bacteria and their resistance profiles. Despite these clinical requirements, conventional phenotypic testing is time-consuming. Additionally, recent rapid drug resistance tests are not compatible with fastidious bacteria such as Streptococcus and Haemophilus species. In this study, we validated the feasibility of direct bacteria counting using highly sensitive quantitative flow cytometry. Furthermore, by combining flow cytometry and a nucleic acid intercalator, we constructed a highly sensitive method for counting viable fastidious bacteria. These are inherently difficult to measure due to interfering substances from nutrients contained in the medium. Based on the conventional broth microdilution method, our method acquired a few microliter samples in a time series from the same microplate well to exclude the growth curve inconsistency between the samples. Fluorescent staining and flow cytometry measurements were completed within 10 min. Therefore, this approach enabled us to determine antimicrobial resistance for these bacteria within a few hours. Highly sensitive quantitative flow cytometry presents a novel avenue for conducting rapid antimicrobial susceptibility tests.

Medicaid Expansion and Hospitalization for Ambulatory Care-Sensitive Conditions Among Nonelderly Adults With Diabetes

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Among nonelderly adults with diabetes, we compared hospitalizations for ambulatory care–sensitive conditions from 2013 (pre-Medicaid expansion) and 2014 (post-Medicaid expansion) for 13 expansion and 4 nonexpansion states using State Inpatient Databases. Medicaid expansion was associated with decreases in proportions of hospitalizations for chronic conditions (difference between 2014 and 2013 −0.17 percentage points in expansion and 0.37 in nonexpansion states, P = .04), specifically diabetes short-term complications (difference between 2014 and 2013 −0.05 percentage points in expansion and 0.21 in nonexpansion states, P = .04). Increased access to care through Medicaid expansion may improve disease management in nonelderly adults with diabetes.

International prevalence and risk factors evaluation for drug-resistant Streptococcus pneumoniae pneumonia

OBJECTIVE

Streptococcus pneumoniae is the most frequent bacterial pathogen isolated in subjects with Community-acquired pneumonia (CAP) worldwide. Limited data are available regarding the current global burden and risk factors associated with drug-resistant Streptococcus pneumoniae (DRSP) in CAP subjects. We assessed the multinational prevalence and risk factors for DRSP-CAP in a multinational point-prevalence study.

DESIGN

The prevalence of DRSP-CAP was assessed by identification of DRSP in blood or respiratory samples among adults hospitalized with CAP in 54 countries. Prevalence and risk factors were compared among subjects that had microbiological testing and antibiotic susceptibility data. Multivariate logistic regressions were used to identify risk factors independently associated with DRSP-CAP.

RESULTS

3,193 subjects were included in the study. The global prevalence of DRSP-CAP was 1.3% and continental prevalence rates were 7.0% in Africa, 1.2% in Asia, and 1.0% in South America, Europe, and North America, respectively. Macrolide resistance was most frequently identified in subjects with DRSP-CAP (0.6%) followed by penicillin resistance (0.5%). Subjects in Africa were more likely to have DRSP-CAP (OR: 7.6; 95%CI: 3.34-15.35, p<0.001) when compared to centres representing other continents.

CONCLUSIONS

This multinational point-prevalence study found a low global prevalence of DRSP-CAP that may impact guideline development and antimicrobial policies.

Mast cells participate in regulation of lung-gut axis during Staphylococcus aureus pneumonia

Objectives

The lung‐gut axis is known to be involved in the pathogenesis of Staphylococcus aureus pneumonia. However, the underlying mechanisms remain unclear. We examined the role of pulmonary mast cells (MCs) in the regulation of the lung‐gut axis during S. aureus pneumonia.

Materials and Methods

We created a mouse model of S. aureus pneumonia using MC‐deficient mice (Kit^{W‐sh/W‐sh}) and examined the level of inflammation, bacterial burden, expression of cathelicidin‐related antimicrobial peptide (CRAMP) and composition of the gut microbiota. We further evaluated anti‐bacterial immunity by administering bone marrow MCs (BMMCs) or CRAMP into the lungs of Kit^{W‐sh/W‐sh} mice.

Results

After S. aureus challenge, the MC‐deficient mice, compared with wild‐type (WT) mice, displayed attenuated lung inflammation, decreased expression of CRAMP, higher bacterial lung load and disturbance of the intestinal microbiota. Adoptive transfer of BMMCs into the lung effectively reconstituted the host defence against S. aureus in Kit^{W‐sh/W‐sh} mice, thus resulting in recovery of S. aureus pneumonia‐induced intestinal dysfunction. Similarly, exogenous administration of CRAMP significantly enhanced anti‐bacterial immunity in the lungs of MC‐deficient mice.

Conclusions

This study provides evidence for the involvement of MCs in the regulation of the lung‐gut axis during S. aureus pneumonia.

Sublethal β-lactam antibiotics induce PhpP phosphatase expression and StkP kinase phosphorylation in PBP-independent β-lactam antibiotic resistance of Streptococcus pneumoniae

StkP and PhpP of Streptococcus pneumoniae have been confirmed to compose a signaling couple, in which the former is a serine/threonine (Ser/Thr) kinase while the latter was annotated as a phosphotase. StkP has been reported to be involved in penicillin-binding protein (PBP)-independent penicillin resistance of S. pneumoniae. However, the enzymatic characterization of PhpP and the role of PhpP in StkP-PhpP couple remain poorly understood. Here we showed that 1/4 minimal inhibitory concentration (MIC) of penicillin (PCN) or cefotaxime (CTX), the representatives of β-lactam antibiotics, could induce the expression of stkP and phpP genes and phosphorylation of StkP in PCN/CTX-sensitive strain ATCC6306 and three isolates of S. pneumoniae (MICs: 0.02-0.5 μg/ml). The product of phpP gene hydrolyzed PP2C type Ser/Thr phosphotase-specific RRA (pT)VA phosphopeptide substrate with the Km and Kcat values of 277.35 μmoL/L and 0.71 S^-1, and the hydrolytic activity was blocked by sodium fluoride, a PP2C type Ser/Thr phosphatase inhibitor. The phosphorylation levels of StkP in the four phpP gene-knockout (ΔphpP) mutants were significantly higher than that in the wild-type strains. In particular, the MICs of PCN and CTX against the ΔphpP mutants were significantly elevated as 4-16 μg/ml. Therefore, our findings confirmed that sublethal PCN and CTX act as environmental inducers to cause the increase of phpP and stkP gene expression and StkP phosphorylation. PhpP is a PP2C type Ser/Thr protein phosphatase responsible for dephosphorylation of StkP. Knockout of the phpP gene results in a high level of StkP phosphorylation and PBP-independent PCN/CTX resistance of S. pneumoniae.

Multidrug-Resistant Gram-Negative Bacterial Infections in the Hospital Setting: Overview, Implications for Clinical Practice, and Emerging Treatment Options

The increasing prevalence of infections due to multidrug-resistant (MDR) gram-negative bacteria constitutes a serious threat to global public health due to the limited treatment options available and the historically slow pace of development of new antimicrobial agents. Infections due to MDR strains are associated with increased morbidity and mortality and prolonged hospitalization, which translates to a significant burden on healthcare systems. In particular, MDR strains of Enterobacteriaceae (especially Klebsiella pneumoniae and Escherichia coli), Pseudomonas aeruginosa, and Acinetobacter baumannii have emerged as particularly serious concerns. In the United States, MDR strains of these organisms have been reported from hospitals throughout the country and are not limited to a small subset of hospitals. Factors that have contributed to the persistence and spread of MDR gram-negative bacteria include the following: overuse of existing antimicrobial agents, which has led to the development of adaptive resistance mechanisms by bacteria; a lack of good antimicrobial stewardship such that use of multiple broad-spectrum agents has helped perpetuate the cycle of increasing resistance; and a lack of good infection control practices. The rising prevalence of infections due to MDR gram-negative bacteria presents a significant dilemma in selecting empiric antimicrobial therapy in seriously ill hospitalized patients. A prudent initial strategy is to initiate treatment with a broad-spectrum regimen pending the availability of microbiological results allowing for targeted or narrowing of therapy. Empiric therapy with newer agents that exhibit good activity against MDR gram-negative bacterial strains such as tigecycline, ceftolozane-tazobactam, ceftazidime-avibactam, and others in the development pipeline offer promising alternatives to existing agents.

No development of ciprofloxacin resistance in the Haemophilus species associated with pneumonia over a 10-year study

Background

The widespread overuse of antibiotics promotes the development of antibiotic resistance in bacteria, which can cause severe illness and constitutes a major public health concern. Haemophilus species are a common cause of community- and nosocomial-acquired pneumonia. The antibiotic resistance of these Gram-negative bacteria can be prevented through the reduction of unnecessary antibiotic prescriptions, the correct use of antibiotics, and good hygiene and infection control. This article examines, retrospectively, antibiotic resistance in patients with community- and nosocomial-acquired pneumonia caused by Haemophilus species.

Methods

The demographic, clinical, and laboratory data of all patients with community- and nosocomial-acquired pneumonia caused by Haemophilus species were collected from the hospital charts at the HELIOS Clinic, Witten/Herdecke University, Wuppertal, Germany, within a study period from 2004 to 2014. Antimicrobial susceptibility testing was performed for the different antibiotics that have been consistently used in the treatment of patients with pneumonia caused by Haemophilus species.

Results

During the study period of January 1, 2004, to August 12, 2014, 82 patients were identified with community- and nosocomial-acquired pneumonia affected by Haemophilus species. These patients had a mean age of 63.8 ± 15.5 (60 [73.2 %, 95 % CI 63.6 %–82.8 %] males and 22 [26.8 %, 95 % CI 17.2 %–36.4 %] females). Haemophilus species had a high resistance rate to erythromycin (38.3 %), ampicillin (24.4 %), piperacillin (20.8 %), cefuroxime (8.5 %), ampicillin-sulbactam (7.3 %), piperacillin-sulbactam (4.3 %), piperacillin-tazobactam (2.5 %), cefotaxime (2.5 %), and levofloxacin (1.6 %). In contrast, they were not resistant to ciprofloxacin in patients with pneumonia (P = 0.016).

Conclusion

Haemophilus species were resistant to many of the typically used antibiotics. Resistance toward ciprofloxacin was not detected in patients with pneumonia caused by Haemophilus species.

What Is New in Antibiotic Therapy in Community-Acquired Pneumonia? An Evidence-Based Approach Focusing on Combined Therapy

Despite all published literature, controversies remain about the optimal antibiotic treatment in community-acquired pneumonia. The most debated issue is whether it is necessary to empirically start one or two antibiotics, i.e. whether or not to cover atypical agents. A review of the literature published from 2005 to present was completed, searching for new insights in antibiotic treatment in community-acquired pneumonia (CAP) focusing on monotherapy versus combined therapy. Forty-one articles were identified enrolling outpatients, and patients admitted to the ward and to the intensive care unit: 11 were meta-analyses, 8 clinical trials and 22 observational-prospective and retrospective-studies. Although controversies remain in the treatment of CAP, the use of combination therapy seems to be associated with a lower mortality in case of severe CAP that requires intensive care unit (ICU) admission, especially when a beta-lactam-macrolide association is delivered. Moreover, combination therapy is associated with better outcomes-although not always with a lower mortality-in cases of non-ICU patients with risk factors for a poor outcome, bacteraemic pneumococcal pneumonia and high suspicion of infection by atypical agents. In this setting, it appears that the best choice of treatment may be a beta-lactam-macrolide regimen.

Selection and evolution of resistance to antimicrobial drugs

The overuse and misuse of antibiotics over many years has selected a high frequency of resistance among medically important bacterial pathogens. The evolution of resistance is complex, frequently involving multiple genetic alterations that minimize biological fitness costs and/or increase the resistance level. Resistance is selected at very low drug concentrations, such as found widely distributed in the environment, and this selects for resistant mutants with a high fitness. Once resistance with high fitness is established in a community it is very difficult to reduce its frequency. Addressing the problem of resistance is essential if we are to ensure a future where we can continue to enjoy effective medical control of bacterial infections. This will require several actions including the discovery and development of novel antibiotics, the creation of a continuous pipeline of drug discovery, and the implementation of effective global antibiotic stewardship to reduce the misuse of antibiotics and their release into the environment.