Clinical relevance of antimicrobial resistance in the management of pneumococcal community-acquired pneumonia

Systematic review of the clinical outcomes of pneumonia with a penicillin-group resistant pneumococcus in respiratory and blood culture specimens in children in low- and middle-income countries

Background

Streptococcus pneumoniae is one of the most common bacteria causing pneumonia and the World Health Organization (WHO) recommends first-line treatment of pneumonia with penicillins. Due to increases in the frequency of penicillin resistance, this systematic review aimed to determine the clinical outcomes of children with pneumonia in low- and middle-income countries (LMICs), with penicillin-group resistant pneumococci in respiratory and/or blood cultures specimens.

Methods

English-language articles from January 2000 to November 2020 were identified by searching four databases. Systematic reviews and epidemiological studies from LMICs that included children aged one month to 9 years and reported outcomes of pneumonia with a penicillin-resistant pneumococcus in respiratory and blood culture specimens with or without comparison groups were included. Risk of bias was assessed using the Effective Public Health Practice Project (EPHPP) Quality Assessment Tool for Quantitative Studies. A narrative synthesis of findings based on the results of included studies was performed.

Results

We included 7 articles involving 2864 children. One strong- and four medium-quality studies showed no difference in clinical outcomes (duration of symptoms, length of hospital stay and mortality) between those children with penicillin non-susceptible compared to susceptible pneumococci. Two weak quality studies suggested better outcomes in the penicillin-susceptible group.

Conclusions

Current evidence suggests no difference in clinical outcomes of child pneumonia due to a penicillin-resistant S. pneumoniae and as such, there is no evidence to support a change in current WHO antibiotic guidelines.

Prevalence of Invasive Streptococcus pneumoniae Infections among Iranian Children: A Systematic Review and Meta-Analysis

Background:

Streptococcus pneumoniae is an important pathogen of children, mostly in developing countries. We aimed to investigate the prevalence of invasive S. pneumoniae among Iranian children using a systematic review and meta-analysis.

Methods:

A systematic search was carried out to identify papers published by Iranian authors in the Web of Science, PubMed, Scopus, and Google Scholar electronic databases from January of 2010 to December of 2017. Then, seven publications that met our inclusion criteria were selected for data extraction and analysis.

Results:

Totally, one study was multicenter, and six were single-center based studies. Meanwhile, all of the included studied performed among hospitalized patients. Seven studies reported the prevalence of invasive S. pneumoniae isolated from children, of these the pooled prevalence of S. pneumoniae was 2.5% (95% CI: 0.7%–9.1%).

Conclusion:

The overall prevalence of invasive S. pneumoniae infections among Iranian children is low (2.5%). However, further clinical studies are required to elucidate the burden of infections among Iranian children, especially in eastern regions.

The Role of Neutrophils and Neutrophil Elastase in Pneumococcal Pneumonia

Streptococcus pneumoniae, also known as pneumococcus, is a Gram-positive diplococcus and a major human pathogen. This bacterium is a leading cause of bacterial pneumonia, otitis media, meningitis, and septicemia, and is a major cause of morbidity and mortality worldwide. To date, studies on S. pneumoniae have mainly focused on the role of its virulence factors including toxins, cell surface proteins, and capsules. However, accumulating evidence indicates that in addition to these studies, knowledge of host factors and host-pathogen interactions is essential for understanding the pathogenesis of pneumococcal diseases. Recent studies have demonstrated that neutrophil accumulation, which is generally considered to play a critical role in host defense during bacterial infections, can significantly contribute to lung injury and immune subversion, leading to pneumococcal invasion of the bloodstream. Here, we review bacterial and host factors, focusing on the role of neutrophils and their elastase, which contribute to the progression of pneumococcal pneumonia.

Quercetin, a pneumolysin inhibitor, protects mice against Streptococcus pneumoniae infection

Pneumolysin (PLY), a pore-forming cytotoxin and a major virulence determinant, is a member of the cholesterol-dependent cytolysin (CDC) family and essential for promoting Streptococcus pneumoniae (S.pneumoniae) infection. Due to the action characteristics of hemolysin itself, the pneumolysin released after killing bacteria with conventional antibiotics still has the ability to damage host cells; therefore, drug treatments directly inhibiting hemolysin activity are the most effective. Hemolysis assays were used to confirm that quercetin can inhibit the activity of PLY, protecting cells in vitro, and an oligomerization assay was used to determine the mechanism of quercetin to suppress PLY activity. Live/Dead testing, lactate dehydrogenase (LDH) release analysis and a murine model of endonasal pulmonary infection were used to explore the capability of quercetin to protect cells and mice from S. pneumoniae-mediated damage in vivo and in vitro. The results indicated that quercetin significantly reduced PLY-induced hemolytic activity and cytotoxicity via repressing the formation of oligomers. In addition, treatment with quercetin can reduce PLY-mediated cell injury, improve the survival rate of mice infected with a lethal dose of S. pneumoniae, alleviate the pathological damage of lung tissue and inhibit the release of cytokines (IL-1β and TNF-α) in bronchoalveolar lavage fluid. Considering the importance of these events in antimicrobial resistant S. pneumoniae pathogenesis, our results indicated that quercetin may be a novel potential drug candidate for the treatment of clinical pneumococcal infections.

From Phenylthiazoles to Phenylpyrazoles: Broadening the Antibacterial Spectrum toward Carbapenem-Resistant Bacteria

The narrow antibacterial spectrum of phenylthiazole antibiotics was expanded by replacing central thiazole with a pyrazole ring while maintaining its other pharmacophoric features. The most promising derivative, compound 23, was more potent than vancomycin against multidrug-resistant Gram-positive clinical isolates, including vancomycin- and linezolid-resistant methicillin-resistant Staphylococcus aureus (MRSA), with a minimum inhibitory concentration (MIC) value as low as 0.5 μg/mL. Moreover, compound 23 was superior to imipenem and meropenem against highly pathogenic carbapenem-resistant strains, such as Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli. In addition to the notable biofilm inhibition activity, compound 23 outperformed both vancomycin and kanamycin in reducing the intracellular burden of both Gram-positive and Gram-negative pathogenic bacteria. Compound 23 cleared 90% of intracellular MRSA and 98% of Salmonella enteritidis at 2× the MIC. Moreover, preliminary pharmacokinetic investigations indicated that this class of novel antibacterial compounds is highly metabolically stable with a biological half-life of 10.5 h, suggesting a once-daily dosing regimen.

Recombinant activated protein C attenuates coagulopathy and inflammation when administered early in murine pneumococcal pneumonia

Recombinant human activated protein C (APC), which has both anticoagulant and anti-inflammatory properties, improves survival of patients with severe sepsis. This beneficial effect is especially apparent in patients with pneumococcal pneumonia. Earlier treatment with APC in sepsis has been associated with a better therapeutic response as compared to later treatment. In a mouse model it was recently confirmed that recombinant murine (rm-)APC decreases coagulation activation and improves survival in pneumococcal pneumonia; however, APC did not impact on the inflammatory response. The aim of this study was to determine the effect of APC treatment instigated early in infection on activation of coagulation and inflammation after induction of pneumococcal pneumonia. Mice were infected intranasally with viable S. pneumoniae. Mice were treated with rm-APC (125 μg) or vehicle intraperitoneally 12 hours after infection and were sacrificed after 20 hours, after which blood and organs were harvested for determination of bacterial outgrowth, coagulation activation and inflammatory markers. In this early treatment model, rm-APC treatment inhibited pulmonary and systemic activation of coagulation as reflected by lower levels of throm-bin-antithrombin complexes and D-dimer. Moreover, rm-APC reduced the levels of a large number of cytokines and chemokines in the lung. When administered early in pneumococcal pneumonia, rm-APC inhibits systemic and pulmonary activation of coagulation and moreover exerts various anti-inflammatory effects in the lung.

The Role of Galectin-3 in the Kidneys

Galectin-3 is a 32- to 35-kDa member of the galectin family of b-galactoside-binding lectins, which is characterized by a carbohydrate recognition domain. Through its carbohydrate-binding function, it regulates cell growth, differentiation, and inflammation. It also plays a complex, context-dependent role in the kidneys. During development, it promotes nephrogenesis and is strongly expressed in the ureteric bud and its derivatives. An increase in the concentration of galectin-3 has been reported to be associated with fibrosis of the kidneys. Elevated levels of plasma galectin-3 are also associated with increased risks of rapid renal function decline, incident chronic kidney disease, and progressive renal impairment, and also with cardiovascular end points, infection, and all-cause mortality in patients with renal function impairment. This review discusses a general survey on galectin-3 expressions in nephrogenesis, kidney injury animal models, clinical renal diseases, renal transplantation and the potential role of galectin-3 for treatment in kidney disease.

Community-acquired pneumonia: impact of empirical antibiotic therapy without respiratory fluoroquinolones nor third-generation cephalosporins

Guidelines for inpatients with community-acquired pneumonia (CAP) propose to use respiratory fluoroquinolone (RFQ) and/or third-generation cephalosporins (Ceph-3). However, broad-spectrum antibiotic therapy is associated with the emergence of drug-resistant bacteria. We established a guideline in which RFQ and Ceph-3 were excluded as a first course. Our aim was to evaluate the impact of our therapeutic choices for CAP on the length of hospital stay (LOS) and patient outcome. This was a cohort study of patients with CAP from July 2005 to June 2014. We compared patients benefiting from our guideline established in 2008 to those receiving non-consensual antibiotics. Disease severity was evaluated through the Pneumonia Severity Index (PSI). The empirical treatment for PSI III to V was a combination therapy of amoxicillin-clavulanic acid (AMX-C) + roxithromycin (RX) or AMX + ofloxacin. Adherence to guidelines was defined by the prescription of one of these antibiotic agents. Requirement for intensive care or death defined unfavorable outcome. Among 1,370 patients, 847 were treated according to our guideline (61.8 %, group 1) and 523 without concordant therapy (38.2 %, group 2). The mean PSI was similar: 82 vs. 83, p > 0.5. The mean LOS was lower in group 1: 7.6 days vs. 9.1 days, p < 0.001. An unfavorable outcome was less frequent in group 1: 5.4 % vs. 9.9 %, p = 0.001. In logistic regression models, concordant therapy was associated with a favorable outcome: adjusted odds ratio (AOR) [95 % confidence interval (CI)] 1.85 [1.20-2.88], p = 0.005. CAP therapy without RFQ and Ceph-3 use was associated with a shorter LOS and fewer unfavorable outcomes.

Myeloid-related protein-8/14 facilitates bacterial growth during pneumococcal pneumonia

BACKGROUND

Streptococcus pneumoniae is the most commonly identified pathogen in community-acquired pneumonia (CAP). Myeloid-related protein (MRP) 8/14 is a major component of neutrophils that is released upon infection or injury. MRP8/14 is essential for protective immunity during infection by a variety of micro-organisms through its capacity to chelate manganese and zinc. Here, we aimed to determine the role of MRP8/14 in pneumococcal pneumonia.

METHODS

MRP8/14 was determined in bronchoalveolar lavage fluid (BALF) and serum of CAP patients, in lung tissue of patients who had succumbed to pneumococcal pneumonia, and in BALF of healthy subjects challenged with lipoteichoic acid (a component of the gram-positive bacterial cell wall) via the airways. Pneumonia was induced in MRP14 deficient and normal wildtype mice. The effect of MRP8/14 on S. pneumoniae growth was studied in vitro.

RESULTS

CAP patients displayed high MRP8/14 levels in BALF, lung tissue and serum. Healthy subjects challenged with lipoteichoic acid demonstrated elevated MRP8/14 in BALF. Likewise, mice with pneumococcal pneumonia had high MRP8/14 levels in lungs and the circulation. MRP14 deficiency, however, was associated with reduced bacterial growth and lethality, in the absence of notable effects on the inflammatory response. High zinc levels strongly inhibited growth of S. pneumoniae in vitro, which was partially reversed by MRP8/14.

CONCLUSIONS

In sharp contrast to its previously reported host-protective role in several infections, the present results reveal that in a model of CAP, MRP8/14 is misused by S. pneumoniae, facilitating bacterial growth by attenuating zinc toxicity toward the pathogen.

Triggering receptor expressed on myeloid cells-1 (TREM-1) improves host defence in pneumococcal pneumonia

Streptococcus (S.) pneumoniae is a common Gram-positive pathogen in community-acquired pneumonia and sepsis. Triggering receptor expressed on myeloid cells-1 (TREM-1) is a receptor on phagocytes known to amplify inflammatory responses. Previous studies showed that TREM-1 inhibition protects against lethality during experimental Gram-negative sepsis. We here aimed to investigate the role of TREM-1 in an experimental model of pneumococcal pneumonia, using TREM-1/3-deficient (Trem-1/3(-/-) ) and wild-type (Wt) mice. Additionally ex vivo responsiveness of Trem-1/3(-/-) neutrophils and macrophages was examined. S. pneumoniae infection resulted in a rapid recruitment of TREM-1-positive neutrophils into the bronchoalveolar space, while high constitutive TREM-1 expression on alveolar macrophages remained unchanged. TREM-1/3 deficiency led to increased lethality, accompanied by enhanced growth of S. pneumoniae at the primary site of infection and increased dissemination to distant organs. Within the first 3-6 h of infection, Trem-1/3(-/-) mice demonstrated a strongly impaired innate immune response in the airways, as reflected by reduced local release of cytokines and chemokines and a delayed influx of neutrophils. Trem-1/3(-/-) alveolar macrophages produced fewer cytokines upon exposure to S. pneumoniae in vitro and were less capable of phagocytosing this pathogen. TREM-1/3 deficiency did not influence neutrophil responsiveness to S. pneumoniae. These results identify TREM-1 as a key player in protective innate immunity during pneumococcal pneumonia, most likely by enhancing the early immune response of alveolar macrophages.

Overview of community-acquired pneumonia and the role of inflammatory mechanisms in the immunopathogenesis of severe pneumococcal disease

Community-acquired pneumonia (CAP) remains a leading cause of morbidity and mortality among the infectious diseases. Despite the implementation of national pneumococcal polyvalent vaccine-based immunisation strategies targeted at high-risk groups, Streptococcus pneumoniae (the pneumococcus) remains the most common cause of CAP. Notwithstanding the HIV pandemic, major challenges confronting the control of CAP include the range of bacterial and viral pathogens causing this condition, the ever-increasing problem of antibiotic resistance worldwide, and increased vulnerability associated with steadily aging populations in developed countries. These and other risk factors, as well as diagnostic strategies, are covered in the first section of this review. Thereafter, the review is focused on the pneumococcus, specifically the major virulence factors of this microbial pathogen and their role in triggering overexuberant inflammatory responses which contribute to the immunopathogenesis of invasive disease. The final section of the review is devoted to a consideration of pharmacological, anti-inflammatory strategies with adjunctive potential in the antimicrobial chemotherapy of CAP. This is focused on macrolides, corticosteroids, and statins with respect to their modes of anti-inflammatory action, current status, and limitations.

CCAAT/enhancer-binding protein δ facilitates bacterial dissemination during pneumococcal pneumonia in a platelet-activating factor receptor-dependent manner

CCAAT/enhancer-binding protein δ (C/EBPδ) recently emerged as an essential player in the inflammatory response to bacterial infections. C/EBPδ levels increase rapidly after a proinflammatory stimulus, and increasing C/EBPδ levels seem to be indispensable for amplification of the inflammatory response. Here we aimed to elucidate the role of C/EBPδ in host defense in community-acquired pneumococcal pneumonia. We show that C/EBPδ(-/-) mice are relatively resistant to pneumococcal pneumonia, as indicated by delayed and reduced mortality, diminished outgrowth of pneumococci in lungs, and reduced dissemination of the infection. Moreover, expression of platelet-activating factor receptor (PAFR), which is known to potentiate bacterial translocation of gram-positive bacteria, was significantly reduced during infection in C/EBPδ(-/-) mice compared with WT controls. Importantly, cell stimulation experiments revealed that C/EBPδ potentiates PAFR expression induced by lipoteichoic acid and pneumococci. Thus, C/EBPδ exaggerates bacterial dissemination during Streptococcus pneumoniae-induced pulmonary infection, suggesting an important role for PAFR-dependent bacterial translocation.

Fluoroquinolones in the management of community-acquired pneumonia in primary care

A literature search was conducted to evaluate the pharmacokinetic and pharmacodynamic profile of the respiratory fluoroquinolones (gemifloxacin, levofloxacin and moxifloxacin) and their efficacy and safety in the management of community-acquired pneumonia (CAP). Data show that CAP is a common presentation in primary care practice, and is associated with high rates of morbidity and mortality, particularly in the elderly. Although the causative pathogens differ depending on treatment setting and patient factors, Streptococcus pneumoniae is the primary pathogen in all treatment settings. As a class, the respiratory fluoroquinolones have a very favorable pharmacokinetic and pharmacodynamic profile. Pharmacodynamic criteria suggest that moxifloxacin and gemifloxacin are more potent against S. pneumoniae, which may have the added benefit of reducing resistance selection and enhancing bacterial eradication. The respiratory fluoroquinolones are also generally well tolerated, and are first-line options for outpatient treatment of CAP in patients with comorbidities or previous antibiotic use.

Combined retrospective analysis of seven phase II and III trials of the efficacy of linezolid in the treatment of pneumonia caused by multidrug-resistant Streptococcus pneumoniae

BACKGROUND

Antimicrobial resistance among Streptococcus pneumoniae is of concern. Up to 30% of pneumococcal isolates worldwide are multidrug resistant.

OBJECTIVE

The objective of this analysis was to assess the effectiveness of linezolid for the treatment of pneumonia caused by S pneumoniae, including multidrug-resistant S pneumoniae (MDRSP).

METHODS

Data from 7 Phase II and III clinical trials that assessed the efficacy of linezolid in community- or hospital-acquired pneumonia were pooled. Adults and children (aged ≤12 years) received linezolid 600 mg and 10 mg/kg, respectively, IV or PO q12h for 7 to 14 days, with the exception of patients with documented bacteremia who could be treated for up to 28 days. Patients with a confirmed baseline isolate of S pneumoniae, including MDRSP, were assessed for clinical and microbiological outcomes. MDRSP was defined as an isolated strain of S pneumoniae that was resistant to ≥3 classes of antibiotics. Clinical cure was defined as the resolution of clinical signs and symptoms of pneumonia compared with baseline, with either improvement or absence of progression of abnormalities on chest radiography. Microbiological eradication was defined as documented or presumed eradication at the test-of-cure (TOC) visit. Results from patients with indeterminate or missing outcomes at TOC were not included in the analyses.

RESULTS

Of the patients with no bacteremia and treated with linezolid, 19 adults had MDRSP and 165 had non-MDRSP, and 3 children had MDRSP and 7 had non-MDRSP. Clinical cure and microbiological eradication rates were not significantly different between those infected with an MDRSP or non-MDRSP pathogen, respectively, in adults (16/19 [84%] and 150/164 [91%]) and children (3/3 [100%] and 7/7 [100%]).

CONCLUSION

Linezolid was efficacious for the treatment of pneumonia caused by S pneumoniae, including multidrug-resistant strains.

Antimicrobial resistance in clinical isolates of Streptococcus pneumoniae in a tertiary hospital in Kuwait, 1997-2007: implications for empiric therapy

OBJECTIVE

This study evaluated antibiotic resistance trends in Streptococcus pneumoniae isolated in a tertiary hospital in Kuwait and its implications for empiric therapy.

MATERIALS AND METHODS

Antimicrobial susceptibility of 1353 strains of S. pneumoniae isolated from clinical specimens during 1997-2007 was performed by disc diffusion method. MIC was determined by E test. The results were compared for 1997-2001, 2002-2005 and 2006-2007.

RESULTS

The prevalence of resistance for the respective periods were as follows: penicillin, 51.3%, 61.3% and 54.5%; erythromycin, 31.2%, 36.7% and 37.7%; tetracycline, 30.8%, 45.3% and 41.3%; co-trimoxazole, 49.5%, 58.5% and 62.8%; clindamycin, 20.4%, 20.6% and 24.5% and chloramphenicol, 8.1%, 8.9% and 3.7%. All were susceptible to vancomycin and rifampicin. For oxacillin-resistant isolates, penicillin resistance was rare (0.8%) with the new non-meningeal breakpoint. However, using the meningeal breakpoints, resistance increased for penicillin from 0.6%, to 28.7%, for cefotaxime from none to 16.5%, and for ceftriaxone from none to 7%. Intermediate resistance to meropenem increased from 1.7% to 22.4%. Multiple drug resistance increased from 22.4% to 37.8%.

CONCLUSION

The study demonstrated that antimicrobial resistance of S. pneumoniae is increasing in Kuwait. However, the results of MIC determinations indicated that penicillin can still be used for therapy of non-meningeal infections. High prevalence of erythromycin resistance suggests that therapy of pneumonia with a macrolide alone may result in failure and should be based on results of susceptibility testing.

PCR using blood for diagnosis of invasive pneumococcal disease: systematic review and meta-analysis

The use of molecular-based methods for the diagnosis of bacterial infections in blood is appealing, but they have not yet passed the threshold for clinical practice. A systematic review of prospective and case-control studies assessing the diagnostic utility of PCR directly with blood samples for the diagnosis of invasive pneumococcal disease (IPD) was performed. A broad search was conducted to identify published and unpublished studies. Two reviewers independently extracted the data. Summary estimates for sensitivity and specificity with 95% confidence intervals (CIs) were calculated by using the hierarchical summary receiver operating characteristic method. The effects of sample processing, PCR type, the gene-specific primer, study design, the participants' age, and the source of infection on the diagnostic odds ratios were assessed through meta-regression. Twenty-nine studies published between 1993 and 2009 were included. By using pneumococcal bacteremia for case definition and healthy people or patients with bacteremia caused by other bacteria as controls (22 studies), the summary estimates for sensitivity and specificity were 57.1% (95% CI, 45.7 to 67.8%) and 98.6% (95% CI, 96.4 to 99.5%), respectively. When the controls were patients suspected of having IPD without pneumococcal bacteremia (26 studies), the respective values were 66.4% (95% CI, 55.9 to 75.6%) and 87.8% (95% CI, 79.5 to 93.1%). With lower degrees of proof for IPD (any culture or serology result and the clinical impression), the sensitivity of PCR decreased and the specificity increased. All analyses were highly heterogeneous. The use of nested PCR and being a child were associated with low specificity, while the use of a cohort study design was associated with a low sensitivity. The lack of an appropriate reference standard might have caused underestimation of the performance of the PCR. Currently available methods for PCR with blood samples for the diagnosis of IPD lack the sensitivity and specificity necessary for clinical practice.

Azithromycin-chloroquine and the intermittent preventive treatment of malaria in pregnancy

In the high malaria-transmission settings of sub-Saharan Africa, malaria in pregnancy is an important cause of maternal, perinatal and neonatal morbidity. Intermittent preventive treatment of malaria in pregnancy (IPTp) with sulphadoxine-pyrimethamine (SP) reduces the incidence of low birth-weight, pre-term delivery, intrauterine growth-retardation and maternal anaemia. However, the public health benefits of IPTp are declining due to SP resistance. The combination of azithromycin and chloroquine is a potential alternative to SP for IPTp. This review summarizes key in vitro and in vivo evidence of azithromycin and chloroquine activity against Plasmodium falciparum and Plasmodium vivax, as well as the anticipated secondary benefits that may result from their combined use in IPTp, including the cure and prevention of many sexually transmitted diseases. Drug costs and the necessity for external financing are discussed along with a range of issues related to drug resistance and surveillance. Several scientific and programmatic questions of interest to policymakers and programme managers are also presented that would need to be addressed before azithromycin-chloroquine could be adopted for use in IPTp.

Pneumococcal antimicrobial resistance: therapeutic strategy and management in community-acquired pneumonia

Streptococcus pneumoniae has been consistently shown to represent the most frequent causative agent of community-acquired pneumonia (CAP) and pneumococcal antibiotic resistance towards different families of antibiotics continues to be a much-debated issue. Microbial resistance causes a great deal of confusion in choosing an empirical treatment for pneumonia and this makes it necessary to know which factors actually determine the real impact of antimicrobial resistance on the outcome of pneumococcal infections. Several different aspects have to be taken into account when analyzing this matter, such as the study design, the condition of the patient at the time of diagnosis, the choice of the initial antimicrobial regimen (combination or monotherapy) and the pharmacokinetic/pharmacodynamic variables of the chosen antibiotic. It is generally accepted that in the treatment of beta-lactam-resistant pneumococcal infections, the use of standard antipneumococcal beta-lactam agents is unlikely to impact negatively on the outcome of CAP when appropriate agents are given in sufficient doses. As a general rule, for infections with penicillin-sensitive strains, penicillin or an aminopenicillin in a standard dosage will be effective; in the cases of strains with intermediate resistance, beta-lactam agents are still considered appropriate treatment although higher dosages are recommended; finally, infections with isolates of high-level penicillin resistance should be treated with alternative agents such as the third-generation cephalosporins or the new antipneumococcal fluoroquinolones. In areas of high prevalence of high-level macrolide resistance, empirical monotherapy with a macrolide is not optimal for the treatment of hospitalised patients with moderate or moderately-severe CAP. Fluoroquinolones are considered to be excellent antibiotics in the treatment of pneumococcal CAP in adults, but their general recommendation has been withheld due to fears of a widespread development of resistance. Most international guidelines recommend combination therapy (beta-lactam plus a macrolide) for the treatment of hospitalised patients with CAP.

Galectin-3 reduces the severity of pneumococcal pneumonia by augmenting neutrophil function

The Gram-positive Streptococcus pneumoniae is the leading cause of community-acquired pneumonia worldwide, resulting in high mortality. Our in vivo studies show that galectin-3(-/-) mice develop more severe pneumonia after infection with S. pneumoniae, as demonstrated by increased bacteremia and lung damage compared to wild-type mice and that galectin-3 reduces the severity of pneumococcal pneumonia in part by augmenting neutrophil function. Specifically, we show that 1) galectin-3 directly acts as a neutrophil-activating agent and potentiates the effect of fMLP, 2) exogenous galectin-3 augments neutrophil phagocytosis of bacteria and delays neutrophil apoptosis, 3) phagocytosis of apoptotic neutrophils by galectin-3(-/-) macrophages is less efficient compared to wild type, and 4) galectin-3 demonstrates bacteriostatic properties against S. pneumoniae in vitro. Furthermore, ad-back of recombinant galectin-3 in vivo protects galectin-3-deficient mice from developing severe pneumonia. Together, these results demonstrate that galectin-3 is a key molecule in the host defense against pneumococcal infection. Therapeutic strategies designed to augment galectin-3 activity may both enhance inflammatory cell function (by directly affecting neutrophil responsiveness and prolonging neutrophil longevity) and have direct bacteriostatic activity, improving clinical outcomes after severe pneumococcal infection.

Penicillin Resistance Not a Factor in Outcome from Invasive Streptococcus pneumoniae Community-Acquired Pneumonia in Adults When Appropriate Empiric Therapy Is Started

BACKGROUND

Invasive Streptococcus pneumoniae pneumonia among adults due to penicillin-resistant or intermediate resistant strains was investigated to determine whether these patients responded poorly to common antibiotic regimens compared to pneumonia due to susceptible strains.

METHODS

During a 21-year period (1983-2003), clinical outcome was analyzed among 3 groups of adults, 19 with resistant, 33 with intermediate, and 133 with susceptible invasive S pneumoniae pneumonia admitted to hospitals in Huntington, West Virginia. Adults with resistant and intermediate infections were matched by age and month of admission to a group of 133 adults with penicillin-susceptible infections. All isolates of resistant and intermediate infections were capsular serotypes/serogroups 6, 9, 14, 19, and 23, and isolates of susceptible infections included 24 different serotypes/serogroups. Case fatality rates were calculated for deaths that occurred during the first 7, first 14, and first 21 days of hospitalization. Minimal inhibitory concentration (MIC) was determined by E-test and capsular serotype by Quellung procedures.

RESULTS

The resistant and susceptible groups did not differ in several measures of severity of illness, including admission vital signs, duration of fever, mean total leukocyte count, number of lobes involved, preexisting underlying diseases, and antibiotic treatment regimens. There were no significant differences in case fatality rates between the 3 groups of pneumonia by days in hospital, age, severity of illness, and empiric antibiotic treatment regimen with a cephalosporin and a macrolide, the most common antibiotic regimen.

CONCLUSIONS

These findings provide evidence that combination antibiotic regimens effective in the treatment of invasive susceptible S pneumoniae pneumonia are equally effective in the treatment of invasive resistant (MIC = 2-4 microg/mL) and of intermediate (MIC = 0.1-1 microg/mL) S pneumoniae pneumonia.

La fenêtre de mutation pour le couple « pneumocoque–fluoroquinolone ». Apport des modèles expérimentaux

Low-level resistance to fluoroquinolones (in vitro susceptible but with topoisomerase mutation, parC) is currently rare among pneumococci in France. However, this resistance is more frequently observed in previously exposed patients and therapeutic failure has been reported. These issues were investigated by using a humanized model of experimental pneumonia induced by pneumococci exhibiting this low-level resistance profile. The results are as follows: 1) when the pneumonia is due to a wild type pneumococcus, humanized ciprofloxacin treatment is not effective because of resistant mutants with parC mutation; moreover, levoflaxin treatment is less bactericidal than gatiflo- or moxifloxacin (-4 vs -6 log CFU/g); 2) when an efflux strain is used, levo-treatment is not efficient but there are no mutants, a gatiflo-treatment is combined when mutants appear and moxiflo-treatment is effective; 3) when the pneumonia is induced with susceptible parC strains, treatment with either levo, or gati, or moxifloxacin is completely ineffective because resistant mutants appear (acquisition of another gyrA mutation). Measure of the mutation prevention concentration (MPC) allows anticipating these results since the mutation window can be determined. These results stress the necessity to identify patients with such pneumococcal strains in order to avoid therapeutic failure and the emergence of fluoroquinolone resistant mutants.

Antimicrobial therapy of multidrug-resistant Streptococcus pneumoniae, vancomycin-resistant enterococci, and methicillin-resistant Staphylococcus aureus

Antibiotic resistance among pneumococci, enterococci, and staphylococci has become increasingly important in recent decades. Clinicians should be familiar with the nuances of antibiotic susceptibility testing and interpretation in selecting antibiotics for these infections. The clinical significance of penicillin-resistant Streptococcus pneumoniae, macrolide-resistant S pneumoniae, and multidrug-resistant S pneumoniae is discussed. The clinical spectrum and therapeutic approach to Enterococcus faecalis (i.e., vancomycin-sensitive enterococci) and E faecium (i.e., vancomycin-resistant enterococci) are discussed. Differences in therapeutic approach between methicillin-sensitive Staphylococcus aureus and methicillin-resistant S aureus (MRSA) infections are reviewed. Differences between in vitro susceptibility testing and in vivo effectiveness of antibiotics for hospital-acquired MRSA (HA-MRSA) are described. Finally, the clinical features of infection and therapy of HA-MRSA and community-acquired MRSA (CA-MRSA) infections are compared.

Controversies in the treatment of pneumococcal community-acquired pneumonia

Community-acquired pneumonia remains an important cause of disease and death both in the developed and the developing worlds, despite the ready availability of potent antimicrobial agents to which the organisms remain susceptible. Furthermore, disease management is complicated by emerging resistance of the common pathogens to the various classes of commonly prescribed antimicrobial agents. Much recent research in the field of community-acquired pneumonia has focused attention on optimal treatment, evaluating the impact of antibiotic resistance, as well as of antimicrobial choices, on the outcome of these infections. In addition, efforts have been directed towards finding adjunctive therapies to antibiotics that may improve the prognosis of these patients. This article reviews some of these research areas, highlighting controversies that still exist with regard to final recommendations, and in particular with regard to infections with Streptococcus pneumoniae, the most common bacterial cause of community-acquired pneumonia.

The Impact of Penicillin Resistance on Short-Term Mortality in Hospitalized Adults with Pneumococcal Pneumonia: A Systematic Review and Meta-Analysis

BACKGROUND

The clinical impact of penicillin resistance on the outcome of pneumococcal pneumonia has remained controversial. We performed a meta-analysis of prospective cohort studies to examine the association between penicillin resistance and short-term all-cause mortality for pneumococcal pneumonia.

METHODS

We retrieved studies published in any language by a comprehensive search of the Medline, Current Contents, and Embase databases for all appropriate articles published up to January 2005. We also manually reviewed bibliographies of retrieved articles, recent national treatment guidelines, and review articles. We included prospective cohort studies that involved adult subjects, and we examined the association between penicillin resistance and short-term mortality for pneumococcal pneumonia. Two reviewers independently extracted data on crude and adjusted risk estimates of all-cause mortality for pneumococcal infections with different levels of penicillin resistance and assessed the methodological quality of selected studies. We also contacted authors to obtain additional information. We performed meta-analyses using a random-effect model.

RESULTS

Of 1152 articles identified in the search, 10 studies that involved 3430 patients (most of whom were hospitalized) were included. The mortality rate was 19.4% in the penicillin-nonsusceptible Streptococcus pneumoniae group and 15.7% in the penicillin-susceptible S. pneumoniae group. The combined relative risks of all-cause mortality for the penicillin-nonsusceptible, -intermediate, and -resistant S. pneumoniae groups, compared with the penicillin-susceptible S. pneumoniae group, were 1.31 (95% confidence interval [CI], 1.08-1.59), 1.34 (95% CI, 1.13-1.60), and 1.29 (95% CI, 1.01-1.66), respectively. The combined adjusted relative risks of mortality for penicillin-nonsusceptible versus penicillin-susceptible S. pneumoniae group was 1.29 (95% CI, 1.04-1.59) for the 6 studies that adjusted for age, comorbidities, and severity of illness. There was minimal between-study heterogeneity in these analyses.

CONCLUSION

Penicillin resistance is associated with a higher mortality rate than is penicillin susceptibility in hospitalized patients with pneumococcal pneumonia. Additional efforts are needed to understand the mechanisms of this association.

Optimal pharmacological therapy for community-acquired pneumonia: the role of dual antibacterial therapy

The optimal pharmacological therapy of community-acquired pneumonia (CAP) is one of the most ardently debated issues in medicine. Presently, most guidelines recommend either a fluoroquinolone alone or dual therapy with a third-generation cephalosporin plus a macrolide in patients hospitalised with CAP, but few provide clinicians with specific considerations for selecting from these agents. Despite a similar spectrum of activity and favourable resistance patterns (for fluoroquinolones and third-generation cephalosporins) against CAP pathogens, there is emerging evidence that dual therapy may be superior to monotherapy in certain populations.In patients with non-severe CAP, the evidence supports the use of either monotherapy or dual therapy in most patients; however, patients with severe CAP or bacteraemic pneumococcal CAP experience improved survival when treated with dual therapy. It is unclear from this evidence if any specific combination of agents is the most effective, but the combination of a third-generation cephalosporin plus a macrolide is the most extensively studied. Dual therapy was superior to monotherapy irrespective of the susceptibility of the aetiological pathogen, thus insufficient antimicrobial spectrum does not explain the disparity. The most likely explanation for improved outcomes with dual therapy is the combined effect of optimised antimicrobial spectrum (including atypicals), decreased impact of resistance to a single agent and the immunomodulatory effects of macrolides. Increasing resistance in patients with non-severe CAP warrants the consideration of dual therapy and perhaps a reappraisal of agents usually reserved for second-line therapy, including doxycycline, in these populations as well. In light of the available evidence, dual therapy should be strongly considered in all patients with severe CAP, especially when complicated by pneumococcal bacteraemia.

Temporal Trends of Invasive Disease Due to Streptococcus pneumoniae among Children in the Intermountain West: Emergence of Nonvaccine Serogroups

BACKGROUND

Use of the heptavalent pneumococcal conjugate vaccine (PCV-7 [Prevnar]) has been associated with decreased a incidence of invasive pneumococcal disease (IPD) among children in the United States.

METHODS

Cases of IPD in children < 18 years of age insured by or receiving health care from Intermountain Health Care during 1996-2003 were identified. Isolates of S. pneumoniae from children with IPD treated at Primary Children's Medical Center (PCMC; Salt Lake City, UT) during 1997-2003 were serogrouped. Temporal trends of IPD, serogroup distribution of pneumococci, and antibiotic resistance among pneumococci were analyzed.

RESULTS

A total of 1535 cases of IPD were identified. The rate of IPD decreased 27% after the introduction of PCV7. Among children with IPD who were cared for at PCMC, disease in 73% was caused by PCV7 serogroups in 1997-2000, compared with 50% in 2001-2003 (P < .001), and the percentage of isolates resistant to penicillin decreased from 34% in 1997-2000 to 22% in 2001-2003 (P = .04). The percentage of IPD cases that were empyema increased from 16% to 30% (P = .015), and the percentage of severe cases of IPD increased from 57% to 71% (P = .026). Children with IPD due to non-PCV7 serogroups were older, were more likely to have parapneumonic empyema, and had longer hospital stays.

CONCLUSIONS

The incidence of IPD in the IMW decreased by 27% after the introduction of the PCV7 vaccine. During the postvaccine period (2001-2003), there were significant decreases in the proportion of cases of IPD caused by PCV7 and antibiotic-resistant serogroups. These benefits were accompanied by a significant increase in the proportion of IPD cases due to non-PCV7 serogroups, with increases in the incidence of empyema and severe IPD.