Antimicrobial susceptibility of Streptococcus pneumoniae in eight European countries from 2001 to 2003

Comparison of transformation frequencies among selected Streptococcus pneumoniae serotypes

Although there are over 90 serotypes of Streptococcus pneumoniae, antimicrobial resistance is predominantly found in a limited number of serotypes/serogroups, namely 6, 9, 14, 19 and 23. There is no compelling mechanism to account for this restriction. We aimed to determine whether serotypes commonly associated with drug resistance have higher transformation frequencies than those that are susceptible to antimicrobial agents. An in vitro investigation of the genetic transformation frequency of drug-resistant serotypes compared with that of susceptible serotypes under the influence of synthetic competence-stimulating peptides was performed. The transforming DNA was genomic DNA carrying a Tn916-like transposon containing the mefE gene that confers resistance to erythromycin. It was observed that serotypes 6, 9, 14, 19 and 23, which are highly associated with drug resistance, do not exhibit a higher degree of transformation efficiency than other serotypes. These findings suggest that the association of serotype with drug resistance is likely due to prolonged exposure to transforming DNA resulting from longer nasopharyngeal carriage and to a greater selective pressure from antimicrobials, particularly in children. This is the first study to compare the transformation frequencies of pneumococcal clinical isolates using genomic DNA that carries the composite Tn916-like element.

Antimicrobial resistance of Streptococcus pneumoniae in Southeast Austria, 1997-2008

Antibiotic resistance in Streptococcus pneumoniae has increased worldwide but varies within geographical regions. We conducted a retrospective analysis of resistance in S. pneumoniae over a 12-year period to assess local and temporal trends in antibacterial resistance. From 1997 to 2008, a total of 1814 non-duplicate S. pneumoniae isolates were identified at the Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Austria. Antibiotic resistance was determined by the Clinical and Laboratory Standards Institute (CLSI) disk diffusion test. For penicillin, the minimum inhibitory concentration was determined by Etest. Susceptibility was defined according to CLSI interpretive criteria. For penicillin, resistance rates were consistently low at 0.2% over the 12-year study period. An increase in resistance was remarkable for erythromycin (3.5% in 1997; 14.7% in 2008), clindamycin (1.8% in 1997; 10.6% in 2008) and tetracycline (1.8% in 2000; 11.0% in 2008). For trimethoprim/sulfamethoxazole, resistance increased slightly to 9.2% in 2008. Quinolones showed a low resistance rate of 0.2% that persisted over the whole study period. In contrast to previously published national data, resistance to penicillin was observed to remain at a remarkably low and constant level. Although international surveillance programmes have set up sustainable and interlinked data networks, our results suggest that regional surveillance may still be needed as decision support for appropriate empirical antibiotic therapy in the local health setting.

Laboratory-based surveillance of Streptococcus pneumoniae invasive disease in children in 10 Latin American countries: a SIREVA II project, 2000-2005

BACKGROUND

For the last 14 years the Pan American Health Organization has been promoting surveillance of invasive pneumococcal disease in Latin American children for better understanding of the disease tendencies regarding capsular types circulation in each country and susceptibility to antimicrobials.

METHODS

Laboratory-based surveillance data from 10 Latin American countries collected from 2000 to 2005 were analyzed, including serotype distribution and susceptibility to beta-lactam antibiotics.

RESULTS

Although 61 different capsular types were identified during the 6-year surveillance, 13 serotypes accounted for 86% of all isolates. These were consistently the most prevalent throughout the study period with serotype 14 predominating. Diminished susceptibility to penicillin was detected in 38% of all Streptococcus pneumoniae isolates, with the highest prevalence in Dominican Republic and Mexico. Decreased susceptibility to penicillin increased in Brazil and Colombia whereas decreased high resistance rates was recorded in Chile.

CONCLUSIONS

These data indicate that 10 countries of the Region continue to have high quality laboratory-based surveillance for pneumococcal disease thus generating valuable information so that healthcare decision makers may prioritize interventions. The heptavalent vaccine will potentially cover from 52.4% to 76.5% of strains causing invasive pneumococcal disease and the 13 valent from 76.7% to 88.3%.

Changes in fluoroquinolone-resistant Streptococcus pneumoniae after 7-valent conjugate vaccination, Spain

Among 4,215 Streptococcus pneumoniae isolates obtained in Spain during 2006, 98 (2.3%) were ciprofloxacin resistant (3.6% from adults and 0.14% from children). In comparison with findings from a 2002 study, global resistance remained stable. Low-level resistance (30 isolates with MIC 4-8 microg/mL) was caused by a reserpine-sensitive efflux phenotype (n = 4) or single topoisomerase IV (parC [n = 24] or parE [n = 1]) changes. One isolate did not show reserpine-sensitive efflux or mutations. High-level resistance (68 isolates with MIC >or=16 microg/mL) was caused by changes in gyrase (gyrA) and parC or parE. New changes in parC (S80P) and gyrA (S81V, E85G) were shown to be involved in resistance by genetic transformation. Although 49 genotypes were observed, clones Spain9V-ST156 and Sweden15A-ST63 accounted for 34.7% of drug-resistant isolates. In comparison with findings from the 2002 study, clones Spain14-ST17, Spain23F-ST81, and ST8819F decreased and 4 new genotypes (ST9710A, ST57016, ST43322, and ST71733) appeared in 2006.

The antimicrobial resistance profile of Streptococcus pneumoniae

Antibacterial resistance in pneumococci is increasing worldwide, primarily against beta-lactams and macrolides. Understanding the role played by molecular determinants of resistance, transformation and competence in the evolution of Streptococcus pneumoniae is important in addressing this trend. Data from the Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin (PROTEKT) study indicate that about 40% of pneumococci display multidrug-resistant phenotypes (resistance to three or more antibiotics), with highly variable prevalence rates observed in different countries. Alterations in the structure of six penicillin-binding proteins (PBPs) have been described in S. pneumoniae (1a, 1b, 2x, 2a, 2b and 3), enabling resistance to beta-lactam antibiotics. Mechanisms conferring macrolide resistance include resistance mediated through the erm(B) gene, which results in macrolide-lincosamide-streptogramin B resistance, or through the mef(A) gene, which encodes an antibiotic efflux pump. Another variant, mef(E), is also expressed in S. pneumoniae; both mef(A) and mef(E) variants are associated with strains belonging to serotype 14. In addition to the selection pressure resulting from misuse of antibiotics, widespread vaccination programmes may contribute to changing pneumococcal epidemiology. Since the introduction of the seven-valent pneumococcal conjugate vaccine (PCV7), the rate of invasive pneumococcal disease due to PCV7 serotypes has declined significantly in many countries, but some countries have reported an increase in non-PCV7 serotypes. This phenomenon, termed 'replacement', is associated with certain pneumococcal serotypes or clones (e.g. serotype 19A). Whether novel 'vaccine escape recombinant' pneumococcal strains are emerging or changes in distribution are part of a secular cycle remains to be determined.

Antimicrobial susceptibility of tigecycline and comparators against bacterial isolates collected as part of the TEST study in Europe (2004-2007)

Tigecycline is a broad-spectrum antimicrobial agent that has been approved for the treatment of skin and soft-tissue infections as well as intra-abdominal infections. The Tigecycline Evaluation and Surveillance Trial (TEST) is a global, longitudinal surveillance study established in 2004 to monitor the in vitro activity of tigecycline and comparator agents against key Gram-negative and Gram-positive pathogens. This report examines data obtained for 24748 isolates collected across 24 European countries between 2004 and 2007. Tigecycline, meropenem and imipenem were the most active antimicrobial agents against most Gram-negative isolates including multidrug-resistant Acinetobacter baumannii (15.7% of the A. baumannii isolates in this study), extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (8.5% of E. coli) and ESBL-producing Klebsiella pneumoniae (13.6% of K. pneumoniae). Only amikacin was active against >90% of Pseudomonas aeruginosa isolates (92.8% susceptible). Tigecycline, linezolid and vancomycin were the most active agents against Gram-positive agents across Europe between 2004 and 2007, with tigecycline displaying the lowest MIC(90) values (minimum inhibitory concentration for 90% of the organisms) against meticillin-resistant Staphylococcus aureus (26.5% of the collected S. aureus isolates), vancomycin-resistant Enterococcus faecium (15.7% of the E. faecium strains) and penicillin-resistant Streptococcus pneumoniae (9.3% of the S. pneumoniae strains). Longitudinal analysis showed no increase in tigecycline MIC values over the 4-year study period, whilst increased resistance was noted for several comparator agents.

Clinical features of bacterial meningitis in Italy: a multicenter prospective observational study

We carried out a prospective observational study on clinical features of bacterial meningitis. Between October 2002 and June 2005, 322 adult bacterial meningitis cases in 49 infectious disease wards in Italy (MENTORE study group) were enrolled in the study. 133 cases were due to Streptococcus pneumoniae, 44 to Neisseria meningitidis and 145 to other microorganisms. A high SAPS score and coma on admission, as well as need for mechanical ventilation, were more frequent in the pneumococcal meningitis group. Neurological impairment was present in 151 out of 311 patients, and was more frequent in pneumococcal meningitis. A single antibiotic was employed in only 90 of 315 cases; a combination of ceftriaxone and ampicillin was the most frequently administered treatment. Ceftriaxone was also the single most used drug. Adjunctive treatment with steroids was administered in 210 out of 303 patients for a median duration of 7 days. Median duration of fever was 4 days, and median hospital stay was 16 days; hospitalization was significantly longer in the pneumococcal meningitis group. At discharge, neurological impairment was still present in 59 (21%) of 277 patients. Twenty (6.9%) out of 289 patients died during hospitalization. Distribution of adverse outcome (death and neurological impairment) in patients treated with or without steroids and within different time zones between onset of symptoms and commencement of antibiotics was studied; a trend toward a worse prognosis was seen in patients treated more than 24 hours after onset of the disease.In our study, infectious disease clinicians made extensive use of steroids as adjuvant therapy for bacterial meningitis, even in absence of detailed national and local guidelines. Mortality seemed to be lower in comparison with the literature.

Safety and efficacy of intravenous tigecycline in treatment of community-acquired pneumonia: results from a double-blind randomized phase 3 comparison study with levofloxacin

Tigecycline exhibits potent in vitro activity against many community-acquired pneumonia (CAP) pathogens, including antibiotic-resistant ones. Its spectrum of activity and ability to penetrate lung tissue suggest it may be effective for hospitalized CAP patients. Hospitalized CAP patients (n=418) were randomized to receive intravenous (i.v.) tigecycline or levofloxacin. Patients could be switched to oral levofloxacin after receiving 6 or more doses of i.v. study medication. Therapy duration was 7 to 14 days. Coprimary efficacy end points were clinical responses in the clinically evaluable (CE: tigecycline, n=138; levofloxacin, n=156) and clinical modified intent-to-treat (c-mITT: tigecycline, n=191; levofloxacin, n=203) populations at test-of-cure (TOC). Safety was assessed in the mITT population (tigecycline, n=208; levofloxacin, n=210). Cure rates in tigecycline and levofloxacin groups were comparable in CE (90.6% versus 87.2%, respectively) and c-mITT (78% versus 77.8%, respectively) populations at TOC. Nausea and vomiting occurred in significantly more tigecycline-treated patients; elevated alanine aminotransferase and aspartate aminotransferase levels were reported in significantly more levofloxacin-treated patients. There were no significant differences in hospital length of stay, median duration of i.v. or oral antibiotic treatments, hospital readmissions, or number of patients switched to oral levofloxacin. Tigecycline was safe, effective, and noninferior to levofloxacin in hospitalized patients with CAP.

Integrated results of 2 phase 3 studies comparing tigecycline and levofloxacin in community-acquired pneumonia

Tigecycline (TGC), a glycylcycline, has expanded activity against Gram-positive and Gram-negative, anaerobic, and atypical bacteria. Two phase 3 studies were conducted. Hospitalized patients with community-acquired pneumonia (CAP) were randomized to intravenous (IV) TGC (100 mg followed by 50 mg bid) or IV levofloxacin (LEV) (500 mg bid). In 1 study, patients could be switched to oral LEV after at least 3 days intravenously. The coprimary efficacy end points were as follows: clinical response in clinically evaluable (CE) and clinical modified intent-to-treat (c-mITT) populations at test-of-cure (TOC). The secondary end points were as follows: microbiologic efficacy and susceptibility to TGC for CAP bacteria. Safety evaluations were included. Eight hundred ninety-one were patients screened: 846 mITT (TGC 424, LEV 422), 574 CE (TGC 282, LEV 292). Most patients had Fine Pneumonia Severity Index II to IV (80.7% TGC, 74.4% LEV, mITT). At TOC (CE), TGC cured 253/282 patients (89.7%) and LEV cured 252/292 patients (86.3%); the absolute difference of TGC-LEV was 3.4% (95% confidence interval [CI], -2.2 to 9.1, noninferior [P < 0.001]). In c-mITT, TGC cured 319/394 patients (81.0%) and LEV cured 321/403 patients (79.7%); the absolute difference of TGC-LEV was 1.3% (95% CI -4.5 to 7.1, noninferior [P < 0.001]). The drug-related adverse events (AEs) of nausea (20.8% TGC versus 6.6% LEV) and vomiting (13.2% TGC versus 3.3% LEV) were significantly higher in TGC; elevated alanine aminotransferase (2.8% TGC versus 7.3% LEV) and aspartate aminotransferase (2.6% TGC versus 6.9% LEV) were significantly higher in LEV. Discontinuations for AEs were low (TGC, 26 patients [6.1%]; LEV, 34 patients [8.1%]). TGC appeared safe and achieved cure rates similar to LEV in hospitalized patients with CAP.

Multidrug-resistant Streptococcus pneumoniae infections: current and future therapeutic options

Antibacterial resistance in Streptococcus pneumoniae is increasing worldwide, affecting principally beta-lactams and macrolides (prevalence ranging between approximately 1% and 90% depending on the geographical area). Fluoroquinolone resistance has also started to emerge in countries with high level of antibacterial resistance and consumption. Of more concern, 40% of pneumococci display multi-drug resistant phenotypes, again with highly variable prevalence among countries. Infections caused by resistant pneumococci can still be treated using first-line antibacterials (beta-lactams), provided the dosage is optimised to cover less susceptible strains. Macrolides can no longer be used as monotherapy, but are combined with beta-lactams to cover intracellular bacteria. Ketolides could be an alternative, but toxicity issues have recently restricted the use of telithromycin in the US. The so-called respiratory fluoroquinolones offer the advantages of easy administration and a spectrum covering extracellular and intracellular pathogens. However, their broad spectrum raises questions regarding the global risk of resistance selection and their safety profile is far from optimal for wide use in the community. For multi-drug resistant pneumococci, ketolides and fluoroquinolones could be considered. A large number of drugs with activity against these multi-drug resistant strains (cephalosporins, carbapenems, glycopeptides, lipopeptides, ketolides, lincosamides, oxazolidinones, glycylcyclines, quinolones, deformylase inhibitors) are currently in development. Most of them are only new derivatives in existing classes, with improved intrinsic activity or lower susceptibility to resistance mechanisms. Except for the new fluoroquinolones, these agents are also primarily targeted towards methicillin-resistant Staphylococcus aureus infections; therefore, demonstration of their clinical efficacy in the management of pneumococcal infections is still awaited.

Streptococcus pneumoniae choline-binding protein E interaction with plasminogen/plasmin stimulates migration across the extracellular matrix

The virulence mechanisms leading Streptococcus pneumoniae to convert from nasopharyngeal colonization to a tissue-invasive phenotype are still largely unknown. Proliferation of infection requires penetration of the extracellular matrix, which occurs by recruitment of host proteases to the bacterial cell surface. We present evidence supporting the role of choline-binding protein E (CBPE) (a member of the surface-exposed choline-binding protein family) as an important receptor for human plasminogen, the precursor of plasmin. The results of ligand overlay blot analyses, solid-phase binding assays, and surface plasmon resonance experiments support the idea of an interaction between CBPE and plasminogen. We have shown that the phosphorylcholine esterase (Pce) domain of CBPE interacts with the plasminogen kringle domains. Analysis of the crystal structure of the Pce domain, followed by site-directed mutagenesis, allowed the identification of the plasminogen-binding region composed in part by lysine residues, some of which map in a linear fashion on the surface of the Pce domain. The biological relevance of the CBPE-plasminogen interaction is supported by the fact that, compared to the wild-type strain, a mutant of pneumococcus with the cbpE gene deleted (i) displays a reduced level of plasminogen binding and plasmin activation and (ii) shows reduced ability to cross the extracellular matrix in an in vitro model. These results support the idea of a physiological role for the CBPE-plasminogen interaction in pneumococcal dissemination into human tissue.

Pneumococcal virulence gene expression and host cytokine profiles during pathogenesis of invasive disease

Pneumococcal disease continues to account for significant morbidity and mortality worldwide. For the development of novel prophylactic and therapeutic strategies against the disease spectrum, a complete understanding of pneumococcal behavior in vivo is necessary. We evaluated the expression patterns of the proven and putative virulence factor genes adcR, cbpA, cbpD, cbpG, cpsA, nanA, pcpA, piaA, ply, psaA, pspA, and spxB after intranasal infection of CD1 mice with serotype 2, 4, and 6A pneumococci by real-time reverse transcription-PCR. Simultaneous gene expression patterns of selected host immunomodulatory molecules, CCL2, CCL5, CD54, CXCL2, interleukin-6, and tomor necrosis factor alpha, were also investigated. We show that pneumococcal virulence genes are differentially expressed in vivo, with some genes demonstrating niche- and serotype-specific differential expression. The in vivo expression patterns could not be attributed to in vitro differences in expression of the genes in transparent and opaque variants of the three strains. The host molecules were significantly upregulated, especially in the lungs, blood, and brains of mice. The pneumococcal-gene expression patterns support their ascribed roles in pathogenesis, providing insight into which protein combinations might be more appropriate as vaccine antigens against invasive disease. This is the first simultaneous comparison of bacterial- and host gene expression in the same animal during pathogenesis. The strategy provides a platform for prospective evaluation of interaction kinetics between invading pneumococci and human patients in culture-positive cases and should be feasible in other infection models.

Prevalence and macrolide resistance phenotypes and genotypes among clinical isolates of Streptococcus pneumoniae collected in Sofia, Bulgaria from 2001 to 2005

A total of 328 clinical isolates of Streptococcus pneumoniae were analyzed to determine the rate of macrolide and penicillin resistance as well as macrolide resistance phenotypes and genotypes. Erythromycin resistance was found in 81 pneumococcal isolates (24.7%) and 10.7% of isolates were clindamycin resistant. The prevalence of penicillin G-intermediate (minimum inhibitory concentrations, MICs, 0.125 to 1 microg/ml) and penicillin-resistant (MICs, >or=2 microg/ml) S. pneumoniae isolates was 25.6% and 13.7%, respectively. The rate of ceftriaxone-intermediate and ceftriaxone-resistant strains was 2.7% and 1.2%, respectively. Among erythromycin-resistant S. pneumoniae isolates, strains harboring mef(A) genes (n=42; 51.8%) were found to be predominant over strains with erm(B) genes (n=34; 42.0%). One (1.2%) isolate carried both erm(B) and mef(A), while 4 (4.9%) isolates carried L4 protein mutations. By using the erythromycin, clindamycin and rokitamycin triple-disk test, 42 strains were assigned to the M phenotype of macrolide resistance, 31 isolates were assigned to the partially inducible (iMcLS) phenotype, 4 were assigned to the constitutive (cMLS) phenotype. Four strains with L4 gene showed a rare phenotype with the triple-disk test. Serotyping of S. pneumoniae isolates suggested that serotype (or serogroup) 14, 6 and 19 were predominant (81.5%) among erythromycin-resistant strains. Among mef(A) positive isolates serotype 14 was predominant, among erm(B) positive isolates serogroups 6 and 19 were the most prevalent.

Antimicrobial resistance among invasive isolates of Streptococcus pneumoniae collected across Canada

Between 2002 and 2003, 736 nonduplicate Streptococcus pneumoniae isolated from blood cultures were collected from 7 of 10 Canadian provinces (10 tertiary care centers). Microdilution broth susceptibility testing was performed using the method prescribed by the Clinical Laboratory Standards Institute. Of the isolates, 16.85% were nonsusceptible to penicillin and 5.4% were highly resistant. Of the S.pneumoniae, 14.1% had reduced susceptibility to erythromycin and 47% had been accounted for by the M phenotype. No isolates were recovered that were resistant to telithromycin. Only 6 isolates were resistant to levofloxacin and gatifloxacin. Of these, 5 strains had intermediate susceptibility to moxifloxacin and 1 was considered susceptible. The rates observed in this study are in keeping with previous surveillance studies among noninvasive isolates.

Pharmacodynamic assessment based on mutant prevention concentrations of fluoroquinolones to prevent the emergence of resistant mutants of Streptococcus pneumoniae

The objective of this study was to investigate the relationship between pharmacokinetic and pharmacodynamic parameters, on the basis of the mutant prevention concentration (MPC) concept, and the emergence of resistant mutants of Streptococcus pneumoniae to fluoroquinolone antibacterials. Some clinical isolates with various MIC and MPC values of moxifloxacin and levofloxacin were exposed under conditions simulating the time-concentration curves observed when moxifloxacin (400 or 80 mg, once a day) or levofloxacin (200 mg, twice a day) was orally administered by using an in vitro pharmacodynamic model. The decrease in susceptibility was evaluated by altering the population analysis profiles after moxifloxacin or levofloxacin treatment for 72 h. When the area under the concentration-time curve from 0 to 24 h (AUC(0-24))/MPC and peak concentration (C(max))/MPC were above 13.41 and 1.20, respectively, complete eradication occurred and no decrease in susceptibility was observed. On the other hand, when AUC(0-24)/MPC and C(max)/MPC were below 0.84 and 0.08, respectively, the susceptibility decreased. However, the time inside the mutant selective window and the time above the MPC did not show any correlation with the decrease in susceptibility. These results suggest that AUC(0-24)/MPC and C(max)/MPC are important parameters for predicting the emergence of resistant mutants and that higher values indicate greater effectiveness.

Drug susceptibility testing of clinical isolates of streptococci and enterococci by the Phoenix automated microbiology system

Background

Drug resistance is an emerging problem among streptococcal and enterococcal species. Automated diagnostic systems for species identification and antimicrobial susceptibility testing (AST) have become recently available. We evaluated drug susceptibility of clinical isolates of streptococci and enterococci using the recent Phoenix system (BD, Sparks, MD). Diagnostic tools included the new SMIC/ID-2 panel for streptococci, and the PMIC/ID-14 for enterococci. Two-hundred and fifty isolates have been investigated: β-hemolytic streptococci (n = 65), Streptococcus pneumoniae (n = 50), viridans group streptococci (n = 32), Enterococcus faecium (n = 40), Enterococcus faecalis (n = 43), other catalase-negative cocci (n = 20). When needed, species ID was determined using molecular methods. Test bacterial strains were chosen among those carrying clinically-relevant resistance determinants (penicillin, macrolides, fluoroquinolones, glycopeptides). AST results of the Phoenix system were compared to minimal inhibitory concentration (MIC) values measured by the Etest method (AB Biodisk, Solna, Sweden).

Results

Streptococci: essential agreement (EA) and categorical agreement (CA) were 91.9% and 98.8%, respectively. Major (ME) and minor errors (mE) accounted for 0.1% and 1.1% of isolates, respectively. No very major errors (VME) were produced. Enterococci: EA was 97%, CA 96%. Small numbers of VME (0.9%), ME (1.4%) and mE (2.8%) were obtained. Overall, EA and CA rates for most drugs were above 90% for both genera. A few VME were found: a) teicoplanin and high-level streptomycin for E. faecalis, b) high-level gentamicin for E. faecium. The mean time to results (± SD) was 11.8 ± 0.9 h, with minor differences between streptococci and enterococci.

Conclusion

The Phoenix system emerged as an effective tool for quantitative AST. Panels based on dilution tests provided rapid and accurate MIC values with regard to clinically-relevant streptococcal and enterococcal species.

Prevalence, characteristics, and molecular epidemiology of macrolide and fluoroquinolone resistance in clinical isolates of Streptococcus pneumoniae at five tertiary-care hospitals in Korea

The genes erm(B), mef(A), and both erm(B) and mef(A) were identified in 42.6, 10.1, and 47.3%, respectively, of the erythromycin-resistant Streptococcus pneumoniae isolates. Of the strains, 3.8% were nonsusceptible to levofloxacin and had 1 to 6 amino acid changes in the quinolone resistance-determining region, including a new mutation, Asn94Ser, in the product of parC. Levofloxacin with reserpine was highly specific for efflux screening.

Antibiotic treatment of community acquired pneumonia varies widely across Germany

Community Acquired Pneumonia (CAP) is a frequent and potentially fatal infectious disease which, in the majority of cases, needs an antibiotic intervention.

OBJECTIVES

Aim was to evaluate antibiotic treatment patterns regarding all types of mono- and combination-therapy throughout the local clinical centres (LCCs) represented in the German competence network CAPNETZ (=Community Acquired Pneumonia Network) and to identify clinical indicators for regional differences.

METHODS

We analysed outpatients and inpatients recruited between March 2003 and April 2005. Patient and treatment details were registered online using standardised data entry forms. A logistic regression model was issued for the 4 most frequently applied antibiotics, adjusting for potentially relevant confounders.

RESULTS

The study sample consisted of 3221 patients at the age of 18 to 102 years. Overall, aminopenicillins plus betalactamase inhibitor (20.4%), fluoroquinolone (17.0%), macrolides combined with cephalosporins third generation (10.6%) and cephalosporins third generation (8.9%) were most frequently prescribed. After control for potential confounders, significant treatment differences remained between study sites. Regional variability of antibiotic CAP-treatment could not be attributed to a number of clinical or sociodemographic factors.

CONCLUSIONS

The presented treatment variability ranges within given guidelines, but indicates the need for an ongoing implementation of evidence-based guidelines in order to avoid potential negative clinical or economic consequences.

Cost-effectiveness of empirical prescribing of antimicrobials in community-acquired pneumonia in three countries in the presence of resistance

OBJECTIVES

To assess the cost-effectiveness of empirical outpatient treatment options for community-acquired pneumonia (CAP) in France, the USA and Germany, representing high, moderate and low antimicrobial resistance prevalence, respectively.

METHODS

A decision analytic model was developed for mild-to-moderate CAP outpatient treatment. Treatment algorithms incorporated follow-up after treatment failure due to resistance or other reasons. First-line treatment included moxifloxacin, beta-lactams, macrolides or doxycycline; second-line treatment used a different antimicrobial class. Country-specific resistance and co-resistance prevalences to first- and second-line therapy for the major CAP pathogens were derived from surveillance studies. Clinical failure rates due to antimicrobial-susceptible and -resistant pathogens were obtained from the literature or estimated. Total costs were estimated using standard sources and a third-party payer perspective. Outcome measures included first-line clinical failures avoided, second-line treatments avoided and hospitalizations avoided. Incremental cost-effectiveness ratios (ICERs) were calculated.

RESULTS

First-line moxifloxacin treatment followed by co-amoxiclav dominated all other treatments in France, the USA and in Germany for all outcome measures. Sensitivity analyses maintained moxifloxacin dominance in France and the USA but affected ICERs in some cases in Germany.

CONCLUSIONS

Antimicrobial resistance/spectrum have a significant impact on outcomes and costs in empirical outpatient CAP treatment. Despite low acquisition costs for generic antibiotics, first-line treatment effective against the major CAP pathogens, including strains resistant to other antimicrobials, resulted in better clinical outcomes in all countries and lower treatment costs for all.

High level expression of His-tagged colicin 5 in E. coli and characterization of its narrow-spectrum bactericidal activity and pore-forming action

Since antibiotics with a broad spectrum of activity would select for resistance among the normal flora, colicins having a narrow spectrum of activity can potentially be developed as novel antibiotics. Colicin-based bactericidal proteins with modified spectra of activity might also be developed by further gene fusion or gene modification. To achieve these goals, it is necessary to first build an efficient system to produce large amounts of colicin. In the presence of an immunity gene, we successfully constructed an expression vector pQE30-cfa-cfi producing high levels of His-tagged colicin 5 (60-80 mg/L). We found that the purified His-tagged colicin 5 possesses narrow-spectrum bactericidal activity against nonimmune Escherichia coli cells. It is highly toxic to sensitive E. coli cells at a low concentration of 0.01 microg/ml, while it is nontoxic to other tested gram-negative bacteria, gram-positive bacteria and yeast at a high concentration of 1000 microg/ml. His-tagged colicin 5 kills sensitive cells by permeabilizing their cell membranes. It is not hemolytic to rabbit erythrocytes and has no obvious cytotoxicity to other nucleated mammalian cells at a high concentration of 500 microg/ml. The His-tagged colicin 5 is similar to wild-type colicin 5 in spectrum and bactericidal activity against E. coli. It is a potential novel antibiotic particularly for treating human and animal infections caused by pathogenic E. coli. Besides producing high level of colicin 5, the highly efficient expression vector constructed here might also be a useful tool to develop colicin-based artificial bactericidal proteins.

Rapid Spread in Norway of an Erythromycin-Resistant Pneumococcal Clone, Despite Low Usage of Macrolides

During the last 4 years, Norway has experienced an increase in macrolide resistance among systemic isolates of Streptococcus pneumoniae. The Norwegian reference laboratory for pneumococci received the isolates from over 85% of the Norwegian cases of systemic pneumococcal disease in the period studied. To study the details of the increased macrolide resistance, all macrolide-resistant systemic pneumococcal isolates (410 isolates) collected in the period from 1995 to 2005 were characterized phenotypically, and a representative selection of 68 strains was also studied genotypically. The serogroups most frequently associated with macrolide resistance in the studied period were 14, 6, 23, 19, and 9. The resistance M-type was expressed in 85% of the resistant isolates. Of the 68 isolates analyzed by multilocus sequence typing, 19 different sequence types (STs) were represented, including several of the international resistant clones. All but one of the clones appeared at a low frequency; mainly as isolated cases. The increase in macrolide resistance seen from 2001 to 2005 proved to be caused by ST-9, defined as the England(14)-9 clone by the Pneumococcal Molecular Epidemiology Network. All ST-9 isolates tested, carried the mef(A) gene and expressed the resistance M-type. This clone first appeared in the Oslo region in 1993, but was by 2005 isolated from all over the country. Children were overrepresented among the cases caused by this clone; however, people aged 20-29, possibly involving the parent generation, were also represented at an increased frequency. The England(14)-9 clone has been able to spread successfully in the Norwegian population despite a relatively low consumption of macrolides.

Clonal spread of mef-positive macrolide-resistant Streptococcus pneumoniae isolates causing invasive disease in adults in Germany

Isolates (3,845) obtained from German adults with invasive pneumococcal disease between 1992 and 2004 were investigated. Of these, 430 isolates (11.2%) were erythromycin A nonsusceptible. Macrolide resistance genotypes and multilocus sequence types were determined. Among the isolates, 35.6% were erm(B) positive and 63.5% were mef positive. Over the study period, the frequency of resistance rose significantly from 2.2 to 17.0% (P < 0.001). A serotype 14, sequence type 9 clone was the most widespread.

Fluoroquinolone resistance in Streptococcus pneumoniae: area under the concentration-time curve/MIC ratio and resistance development with gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin

The potential for resistance development in Streptococcus pneumoniae secondary to exposure to gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin at various levels was examined at high inoculum (10(8.5) to 10(9) log10 CFU/ml) over 96 h in an in vitro pharmacodynamic (PD) model using two fluoroquinolone-susceptible isolates. The pharmacokinetics of each drug was simulated to provide a range of free areas under the concentration-time curves (fAUC) that correlated with various fluoroquinolone doses. Potential first (parC and parE)- and second-step (gyrA and gyrB) mutations in isolates with raised MICs were identified by sequence analysis. PD models simulating fAUC/MICs of 51 and<or=60, 34 and 37, <or=82 and<or=86, and<or=24 for gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin, respectively, against each isolate were associated with first-step parC (S52G, S79Y, and N91D) and second-step gyrA (S81Y and S114G) mutations. For each fluoroquinolone a delay of first- and second-step mutations was observed with increasingly higher fAUC/MIC ratios and recovery of topoisomerase mutations in S. pneumoniae was related to the fAUC/MIC exposure. Clinical doses of gatifloxacin, gemifloxacin, and moxifloxacin exceeded the fAUC/MIC resistance breakpoint against wild-type S. pneumoniae, whereas those of levofloxacin (500 and 750 mg) were associated with first- and second-step mutations. The exposure breakpoints for levofloxacin were significantly different (P<0.001) from those of the newer fluoroquinolones gatifloxacin, gemifloxacin, and moxifloxacin. Additionally, moxifloxacin breakpoints were significantly lower (P<0.002) than those of gatifloxacin. The order of resistance development determined from fAUC/MIC breakpoints was levofloxacin>gatifloxacin>moxifloxacin=gemifloxacin, which may be related to structural differences within the class.

Effect of azithromycin and clarithromycin therapy on pharyngeal carriage of macrolide-resistant streptococci in healthy volunteers: a randomised, double-blind, placebo-controlled study

BACKGROUND

Resistance to antibiotics is a major public-health problem, and studies that link antibiotic use and resistance have shown an association but not a causal effect. We used the macrolides azithromycin and clarithromycin to investigate the direct effect of antibiotic exposure on resistance in the oral streptococcal flora of healthy volunteers.

METHODS

Volunteers were treated with azithromycin (n=74), clarithromycin (74), or placebo (76) in a randomised, double-blind trial. Pharyngeal swabs were obtained before and after administration of study treatment through 180 days. The proportion of streptococci that were macrolide resistant was assessed and the molecular basis of any change in resistance investigated. Analyses were done on an intent-to-treat basis. This study is registered with ClinicalTrials.gov, number NCT00354952.

FINDINGS

The number of dropouts (n=20) was much the same in all groups until day 42; dropouts increased substantially at day 180 (105). Both macrolides significantly increased the proportion of macrolide-resistant streptococci compared with the placebo at all points studied, peaking at day 8 in the clarithromycin group (mean increase 50.0%, 95% CI 41.7-58.2; p<0.0001) and at day 4 in the azithromycin group (53.4%, 43.4-63.5; p<0.0001). The proportion of macrolide-resistant streptococci was higher after azithromycin treatment than after clarithromycin use, with the largest difference between the two groups at day 28 (17.4% difference, 9.2-25.6; p<0.0001). Use of clarithromycin, but not of azithromycin, selected for the erm(B) gene, which confers high-level macrolide resistance.

INTERPRETATION

This study shows that, notwithstanding the different outcomes of resistance selection, macrolide use is the single most important driver of the emergence of macrolide resistance in vivo. Physicians prescribing antibiotics should take into account the striking ecological side-effects of such antibiotics.

Inhibition of pneumococcal choline-binding proteins and cell growth by esters of bicyclic amines

Streptococcus pneumoniae is one of the major pathogens worldwide. The use of currently available antibiotics to treat pneumococcal diseases is hampered by increasing resistance levels; also, capsular polysaccharide-based vaccination is of limited efficacy. Therefore, it is desirable to find targets for the development of new antimicrobial drugs specifically designed to fight pneumococcal infections. Choline-binding proteins are a family of polypeptides, found in all S. pneumoniae strains, that take part in important physiologic processes of this bacterium. Among them are several murein hydrolases whose enzymatic activity is usually inhibited by an excess of choline. Using a simple chromatographic procedure, we have identified several choline analogs able to strongly interact with the choline-binding module (C-LytA) of the major autolysin of S. pneumoniae. Two of these compounds (atropine and ipratropium) display a higher binding affinity to C-LytA than choline, and also increase the stability of the protein. CD and fluorescence spectroscopy analyses revealed that the conformational changes of C-LytA upon binding of these alkaloids are different to those induced by choline, suggesting a different mode of binding. In vitro inhibition assays of three pneumococcal, choline-dependent cell wall lytic enzymes also demonstrated a greater inhibitory efficiency of those molecules. Moreover, atropine and ipratropium strongly inhibited in vitro pneumococcal growth, altering cell morphology and reducing cell viability, a very different response than that observed upon addition of an excess of choline. These results may open up the possibility of the development of bicyclic amines as new antimicrobials for use against pneumococcal pathologies.

Vigilancia de resistencias a los antimicrobianos: estudio VIRA 2006

INTRODUCTION

The objective of this study was to determine the current antimicrobial susceptibility patterns of the most frequent multi-resistant bacteria and to analyze any possible changes with respect to the two VIRA studies carried out in 2001 and 2004.

METHODS

In February 2006, the 40 participating hospitals sent the following microorganisms: non-penicillin-susceptible Streptococcus pneumoniae (92), methicillin-resistant Staphylococcus aureus (MRSA) (290), clinically significant coagulase-negative staphylococci (136), ampicillin-resistant Enterococcus faecium (89), ampicillin-resistant Haemophilus influenzae (67), ciprofloxacin-resistant Escherichia coli (365), Pseudomonas aeruginosa (181), and Acinetobacter baumannii (92). The hospitals provided epidemiological data on these microorganisms. Susceptibility was determined with a broth microdilution method.

RESULTS

Among the non-penicillin-susceptible S. pneumoniae isolates, the proportion of those ones resistant to this antibiotic showed a significant (p < 0.001) decrease (59.8% in 2001, 30.2% in 2004 and 14.3% in 2006). Among MRSA, we detected one isolate nonsusceptible to linezolid, four resistant to quinupristin-dalfopristin and one strain with a vancomycin MIC of 4 microg/mL. The prevalence of extended-spectrum beta-lactamase-producing E. coli was 12.1%. Resistance of A. baumannii to imipenem varied from 27% in the 2001-2004 period to 47.8% in 2006 (p < 0.005).

CONCLUSION

These results again emphasize that resistance surveillance systems are an important tool for preventing the emergence and spread of multi-resistant pathogens.

Assessment of pathogen frequency and resistance patterns among pediatric patient isolates: Report from the 2004 SENTRY Antimicrobial Surveillance Program on 3 continents

Selecting empiric or directed therapy for pathogens isolated from pediatric patients can be problematic. Many antimicrobial agents are not indicated for use in pediatric patients, and regional variations of resistance mechanisms have been reported. The purpose of this study was to analyze antimicrobial resistance patterns and pathogen occurrence rates in pediatric-aged patient infections on 3 continents using data from the SENTRY Antimicrobial Surveillance Program. A total of 3537 clinical isolates were collected from 47 medical centers in 2004. With a protocol that dictated a sampling of 80 consecutive isolates from children (< or =18 years of age), all samples were forwarded to a central laboratory for reference susceptibility testing. Broth microdilution methods and current Clinical and Laboratory Standards Institute breakpoint criteria were used. The 15 most frequently observed pathogens accounted for 93.6% of all isolates. Staphylococcus aureus was the most common pathogen isolated in North America (27.4%) and Europe (19.0%), but Escherichia coli was most common in Latin America (19.3%). All Streptococcus pneumoniae strains from North America and Latin America were susceptible to the newer fluoroquinolones, gatifloxacin and levofloxacin. However, 2 S. pneumoniae strains from Italy were resistant to gatifloxacin, levofloxacin, and ciprofloxacin (> or =4 microg/mL). Ribotype and pulsed-field gel electrophoresis patterns found that these resistant pneumococci were clonal. Numerous strains of Klebsiella spp. (22.5%), E. coli (4.5%), and Proteus mirabilis (4.9%) exhibited phenotypic extended-spectrum beta-lactamase resistance patterns. Four Pseudomonas aeruginosa strains (3 from Latin America and 1 from Europe) were multidrug resistant, 2 P. aeruginosa isolates from Turkey were resistant to polymyxin B (> or =4 microg/mL), and 8.7% of Stenotrophomonas maltophilia isolates from Latin America were resistant to the "drug of choice", trimethoprim/sulfamethoxazole. Physicians should be aware of pathogen occurrences that vary by children's age, geographic location, and prior antimicrobial exposure. Therefore, continued surveillance will be necessary to monitor emerging antimicrobial resistance in the pediatric patient population, especially because new agents such as the fluoroquinolones are used to a greater extent in this age group.

In vitro efficacy, resistance selection, and structural modeling studies implicate the malarial parasite apicoplast as the target of azithromycin

Azithromycin (AZ), a broad-spectrum antibacterial macrolide that inhibits protein synthesis, also manifests reasonable efficacy as an antimalarial. Its mode of action against malarial parasites, however, has remained undefined. Our in vitro investigations with the human malarial parasite Plasmodium falciparum document a remarkable increase in AZ potency when exposure is prolonged from one to two generations of intraerythrocytic growth, with AZ producing 50% inhibition of parasite growth at concentrations in the mid to low nanomolar range. In our culture-adapted lines, AZ displayed no synergy with chloroquine (CQ), amodiaquine, or artesunate. AZ activity was also unaffected by mutations in the pfcrt (P. falciparum chloroquine resistance transporter) or pfmdr1 (P. falciparum multidrug resistance-1) drug resistance loci, as determined using transgenic lines. We have selected mutant, AZ-resistant 7G8 and Dd2 parasite lines. In the AZ-resistant 7G8 line, the bacterial-like apicoplast large subunit ribosomal RNA harbored a U438C mutation in domain I. Both AZ-resistant lines revealed a G76V mutation in a conserved region of the apicoplast-encoded P. falciparum ribosomal protein L4 (PfRpl4). This protein is predicted to associate with the nuclear genome-encoded P. falciparum ribosomal protein L22 (PfRpl22) and the large subunit rRNA to form the 50 S ribosome polypeptide exit tunnel that can be occupied by AZ. The PfRpl22 sequence remained unchanged. Molecular modeling of mutant PfRpl4 with AZ suggests an altered orientation of the L75 side chain that could preclude AZ binding. These data imply that AZ acts on the apicoplast bacterial-like translation machinery and identify Pfrpl4 as a potential marker of resistance.

Molecular characterization of non-penicillin-susceptible Streptococcus pneumoniae in Norway

A total of 125 non-penicillin-susceptible Streptococcus pneumoniae isolates were received at the Norwegian Institute of Public Health in the period from 1995 to 2001. The strains were tested for antimicrobial susceptibility, serotyped, and genotyped by multilocus sequence typing (MLST); and their penicillin-binding proteins (PBPs) were typed by restriction fragment length polymorphism analysis of their pbp genes. Of the 125 strains, 48 (38%) were fully resistant to penicillin and 77 (62%) were intermediately resistant to penicillin. Most of the strains resistant to penicillin were also resistant to one or several additional antibiotics. The most frequent serotypes among the non-penicillin-susceptible strains were 14, 9V, 19F, 23F, and 6B. MLST analysis showed a high degree of genetic diversity among the 119 strains tested, with a total of 74 different sequence types. Six of the 26 internationally known resistant clones were present; the Spain(9V)-3 clone was the most frequent, with 19 isolates. A total of 74 (62%) of the isolates were related to 1 of the 26 international clones. Restriction enzyme analyses of the pbp1a, pbp2b, and pbp2x genes revealed 12, 12, and 19 different patterns, respectively; and a total of 43 different PBPs types were demonstrated. Our data indicate that the non-penicillin-susceptible strains in Norway are highly diverse genetically and that limited spread of the internationally known resistant strains occurred in the country in the period examined.

Serotype distribution and antimicrobial susceptibility of S. pneumoniae causing invasive disease in Thai children younger than 5 years old, 2000-2005

In order to predict the potential benefit of pneumococcal conjugate vaccines (PCV), we evaluated the serotype coverage of the 7-, 9-, 11- and 13-valent PCV over the isolates causing invasive pneumococcal disease (IPD) in Thai children. One hundred and fifteen Streptococcus pneumoniae isolates from sterile sites in children younger than 5 years old between 2000 and 2005 were serotyped. The coverages of 7-, 9-, 11-, and 13-valent PCV were 69%, 73.8%, 73.8% and 85.7% in children younger than 2 years, and 73.9%, 77.4%, 77.4% and 87.8% in children younger than 5 years of age, respectively. 69.6% and 22.6% of the isolates were non-susceptible to penicillin and cefotaxime. 7-valent PCV covered 89% and 100% of penicillin and cefotaxime non-susceptible isolates.

Selection of antibiotic-resistant pathogens in the community

In recent years, the importance of the community as a breeding ground for antibiotic-resistant pathogens is being recognized. Prescription of antimicrobial drugs for viral infections, inadequate dosage, use of long-acting macrolides and broad-spectrum antibiotics, and accessibility of over-the-counter antibiotics in many countries are the main drivers of increasing resistance. Education of physicians and the public on the correct use of antibiotics, introduction of rapid and reliable laboratory methods to distinguish between viral and bacterial infections, and offering economic incentives to the pharmaceutical industry to develop new drugs appear to be key issues in the confrontation with this serious public health problem.

Surveillance of invasive Streptococcus pneumoniae in Taiwan, 2002–2003

A total of 522 Streptococcus pneumoniae invasive isolates from diverse sources were collected from January 2002 to December 2003 in Taiwan in order to understand the serotype distribution of invasive isolates in Taiwan. The most frequently isolated serotypes of S. pneumoniae were types 14 (18.4 %), 23F (15.1 %), 3 (13.8 %), 19F (13.4 %), 6B (8.2 %), 9V (3.6 %) and 4 (2.5 %). The majority of cases were either under 5 years of age (24.1 %) or older than 65 years (36.6 %). Serotype distribution in adults aged over 14 years and children aged under 2 years was similar, except for that of type 3, which was more prevalent in adults. Penicillin-non-susceptible strains accounted for 67.7 % of all strains and were the predominant strains of serotypes 23F, 19F, 6B and 14. Most strains were susceptible to cephem drug, 85.7 % of isolates were susceptible to cefotaxime and 92.9 % were susceptible to ceftriaxone. A total of 72.6 % (379/522) of the isolates were resistant to at least two antibiotics. The 23-valent vaccine in the current commercial market would cover 87.2 % of the serotypes and 100 % of the penicillin-non-susceptible serotypes of S. pneumoniae in Taiwan. The coverage of 7- and 11-valent protein conjugate vaccines of the serotypes in children under 2 years of age would be 78.8 and 86.5 %, respectively. These results will help to assess the adequacy of the vaccine formulations marketed in Taiwan.

Rapid screening of fluoroquinolone resistance determinants in Streptococcus pneumoniae by PCR-restriction fragment length polymorphism and single-strand conformational polymorphism

A rapid method, using PCR-restriction fragment length and single-strand conformation polymorphism (SSCP), was applied to screen for mutations of the fluoroquinolone resistance determinants in Streptococcus pneumoniae. One hundred nonduplicate Streptococcus pneumoniae isolates with ciprofloxacin MICs of > or = 4.0 microg/ml from the Prince of Wales Hospital, Hong Kong, years 2000 to 2003, were examined. For each isolate, PCR amplicons of quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC, and parE genes were digested with AluI, HinfI, Sau3AI, and MspI, respectively, and analyzed by SSCP. Each SSCP pattern was given a number, and each isolate obtained a four-digit code, e.g., 1111, that represented the SSCP profile. The SSCP patterns were correlated to mutations characterized from sequence analyses of PCR amplicons. The most common SSCP profile obtained was no. 5232 (40%), which included strains with two amino acid substitutions in the ParC (Lys-137-Asn) and ParE (Ile-460-Val) genes, followed by the SSCP profile 5223 (17%), which included strains with amino acid substitutions in the ParE (Ile-460-Val) gene only. Ten isolates (10%) with amino acid substitutions at GyrA and ParE (+/-ParC) genes were resistant to levofloxacin with a MIC of > or = 16 microg/ml. Other SSCP profiles were unique in distinguishing the common amino acid substitutions in GyrA (Ser-81-Phe) and ParC (Lys-137-Asn, Ser-79-Phe plus Lys-137-Asn, Asp-83-Asn plus Lys-137-Asn, Ser-79-Phe, and Glu-96-Asp). SSCP analysis of restricted fragments generated patterns that were highly discriminative for mutations present in the QRDRs of gyrA, gyrB, parC, and parE. This method provides a database of high resolution profiles on these mutations and allows rapid screening for new mutations of the fluoroquinolone resistance genes.

Levofloxacin use in the elderly: focus on pneumonia

Levofloxacin is a broad-spectrum, rapid-acting bactericidal agent that exhibits concentration-dependent killing activity as well as a postantibiotic effect. Its activity includes enteric Gram-negative bacilli, Acinetobacter spp., Pseudomonas aeruginosa, methicillin-susceptible Staphylococcus aureus and most species of streptococci, including Streptococcus pneumoniae. With increasing age, there is a natural decline in renal function by approximately 1 ml/min/year after the age of 30 years, or an average decrease in creatinine clearance of 40% by the age of 80 years. This decline in renal function can have a significant impact on antibiotics that are predominantly eliminated from the body via the kidneys, such as levofloxacin. The favorable pharmacodynamic, safety and efficacy profiles, in addition to in vitro activity versus the usual respiratory pathogens, make levofloxacin among the first-line agents for the management of pneumonia, and an option for other respiratory bacterial infections in which more resistant organisms are a consideration, such as in the elderly population.

Optimal therapy for severe pneumococcal community-acquired pneumonia

Streptococcus pneumoniae is responsible for two-thirds of ICU admissions due to community-acquired pneumonia (CAP) and is the leading cause of CAP-related death. Early death is principally due to cardiovascular collapse, whereas late death is associated with hypoxemic respiratory failure. Outcome depends on interactions between non-modifiable factors of predisposition (age, comorbidities, host defences, genetic predisposition) or infection (toxins, virulence, bacterial burden) and modifiable factors (organ-failure support, surgical drainage for empyema, adjuvant therapies and antibiotics). Excess mortality has been reported when initial therapy is discordant, but more than 95% of isolates have minimum inhibitory concentration (MIC) <4 microg/ml. Therefore, cefotaxime, ceftriaxone and high doses of amoxicillin remain successful for non-meningeal infections. Recent studies suggest that initial combination therapy improves survival in the subset of bacteremic episodes with highest severity, conceivably due to the immunomodulatory effects of macrolides. Prospective, randomized clinical trials of pneumonia patients with a pneumonia severity index score above 90 are warranted to define optimal antibiotic regimens.