Drug-resistant pneumococcal pneumonia: clinical relevance and approach to management

Microbiology laboratories involved in disease and antimicrobial resistance surveillance: Strengths and challenges of the central African states

Laboratory systems have been largely neglected on the margins of health systems in Africa. However, since the 2000s, many African countries have benefited from massive investments to strengthen laboratory capacities through projects fighting priority diseases (HIV/AIDS, tuberculosis, malaria). This review examined the laboratory capacities of the Economic Community of Central African States (ECCAS). Online research using specific terms was carried out. Studies published between 2000 and 2021 on the role of the laboratory in disease and antimicrobial resistance surveillance in the 11 ECCAS countries were considered. The number of human and animal health laboratories meeting international standards was very low in the sub-region. There were only seven International Organization for Standardization (ISO) 15189-accredited human health laboratories, with five in Cameroon and two in Rwanda. There were five high biosafety level (BSL) laboratories (one BSL3 laboratory each in Cameroon, the Central African Republic, Democratic Republic of Congo and the Republic of Congo, and one BSL4 laboratory in Gabon) and three ISO 17025-accredited laboratories in the ECCAS sub-region. Only six countries currently have whole-genome sequencing devices, which is insufficient for a sub-region as large and populous as ECCAS. Yet, a plethora of pathogens, particularly haemorrhagic viruses, are endemic in these countries. The need for laboratory capacity strengthening following a One Health approach is imperative. Since emerging and re-emerging zoonotic infectious diseases are projected to triple in frequency over the next 50 years and given the inextricable link between human and animal health, actors in the two health sectors must collaborate to preserve world health.

Combined use of a broad-panel respiratory multiplex PCR and procalcitonin to reduce duration of antibiotics exposure in patients with severe community-acquired pneumonia (MULTI-CAP): a multicentre, parallel-group, open-label, individual randomised trial conducted in French intensive care units

INTRODUCTION

At the time of the worrying emergence and spread of bacterial resistance, reducing the selection pressure by reducing the exposure to antibiotics in patients with community-acquired pneumonia (CAP) is a public health issue. In this context, the combined use of molecular tests and biomarkers for guiding antibiotics discontinuation is attractive. Therefore, we have designed a trial comparing an integrated approach of diagnosis and treatment of severe CAP to usual care.

METHODS AND ANALYSIS

The multiplex PCR and procalcitonin to reduce duration of antibiotics exposure in patients with severe-CAP (MULTI-CAP) trial is a multicentre (n=20), parallel-group, superiority, open-label, randomised trial. Patients are included if adult admitted to intensive care unit for a CAP. Diagnosis of pneumonia is based on clinical criteria and a newly appeared parenchymal infiltrate. Immunocompromised patients are excluded. Subjects are randomised (1:1 ratio) to either the intervention arm (experimental strategy) or the control arm (usual strategy). In the intervention arm, the microbiological diagnosis combines a respiratory multiplex PCR (mPCR) and conventional microbiological investigations. An algorithm of early antibiotic de-escalation or discontinuation is recommended, based on mPCR results and the procalcitonin value. In the control arm, only conventional microbiological investigations are performed and antibiotics de-escalation remains at the clinician's discretion. The primary endpoint is the number of days alive without any antibiotic from the randomisation to day 28. Based on our hypothesis of 2 days gain in the intervention arm, we aim to enrol a total of 450 patients over a 30-month period.

ETHICS AND DISSEMINATION

The MULTI-CAP trial is conducted according to the principles of the Declaration of Helsinki, is registered in Clinical Trials and has been approved by the Committee for Protection of Persons and the National French Drug Safety Agency. Written informed consents are obtained from all the patients (or representatives). The results will be disseminated through educational institutions, submitted to peer-reviewed journals for publication and presented at medical congresses.

TRIAL REGISTRATION NUMBER

NCT03452826; Pre-results.

General practitioners’ knowledge, attitudes and practices on antibiotic prescribing for acute respiratory infections in children in Lubumbashi, Democratic Republic of Congo

Objective: To assess the knowledge, attitudes and practices declared among general practitioners (GPs) concerning the use of antibiotics for the treatment of ARI in children under 5 years in Lubumbashi. Methods: A cross-sectional survey was conducted to assess the level of knowledge, attitude and practices concerning antibiotic prescribing among 67 GPs working in the pediatric setting in various health structures in Lubumbashi city, in the Democratic Republic of Congo. Data were collected from April 1st to June 30th, 2020. Results: GPs had limited knowledge about antibiotic prescriptions (mean of 46% correct answers to 8 questions). Although they are generally concerned about antibiotic resistance (mean ± SD = 0.50 ± 0.68), and are unwilling to submit to pressure to prescribe antibiotics to meet patient demands and expectations (mean ± SD = –1.78 ± 0.31) and the requirements to prescribe antibiotics for fear of losing patients (mean ± SD = –1.67 ± 0.47), there was a lack of motivation to change prescribing practices (mean ± SD = −0.37 ± 0.94) and strong agreement that they themselves should take responsibility for tackling antibiotic resistance (mean ± SD = 1.24 ± 0.74). Multiple linear regression results showed that higher knowledge scores were associated with less avoidance of responsibility when prescribing antibiotics (β = 0.919; p = 0.000). Conclusion: To curb the over-prescription of antibiotics, it is not enough to improve knowledge in itself. The lack of motivation of physicians to change must be addressed through a systematic approach. These data show the need for interventions that support the rational prescribing of antibiotics.

Antimicrobial Resistance Among Streptococcus pneumoniae

Antibiotic resistance in Streptococcus pneumoniae (pneumococcus), the main pathogen responsible for community-acquired pneumonia (CAP), meningitis, bacteremia, and otitis media, is a major concern for clinicians. This pathogen is associated with high rates of morbidity and mortality, especially among children under 2 years old, immunocompromised persons, and the elderly population. The major anti-pneumococcus agents are β-lactams and macrolides, with fluoroquinolones ranking third. The emergence of antibiotic-resistant pneumococcus due to overuse of antibiotics is a global concern. While the discovery of novel classes of antibiotics for the pneumococcus is at a standstill, significant progress in reducing the problem of resistance is associated with antibacterial vaccines. Nevertheless, the World Health Organization recently considered drug-resistant S. pneumoniae as ranking among the 12 bacteria, for which there is an urgent need for new treatments. A challenge is to slow the evolution of new strains that are resistant to the vaccines.

High prevalence of antibiotic resistance in nasopharyngeal bacterial isolates from healthy children in rural Uganda: A cross-sectional study

BACKGROUND

In Uganda, the main causes of death in children under 5 years of age are malaria and pneumonia--often due to delayed diagnosis and treatment. In preparation for a community case management intervention for pneumonia and malaria, the bacterial composition of the nasopharyngeal flora and its in vitro resistance were determined in children aged five or under to establish baseline resistance to commonly used antibiotics.

METHODS

In a population-based survey in April 2008, nasopharyngeal specimens were collected from 152 randomly selected healthy children under 5 years of age in the Iganga/Mayuge Health and Demographic Surveillance Site (HDSS). Medical history and prior treatment were recorded. Demographic characteristics and risk factors for carriage of resistant strains were obtained from the HDSS census. Bacteria were isolated and analysed for antibiotic susceptibility using disk diffusion and E test.

RESULTS

Streptococcus pneumoniae (S. pneumoniae) carriage was 58.6%, and, while most (80.9%) isolates had intermediate resistance to penicillin, none was highly resistant. Whereas no isolate was resistant to erythromycin, 98.9% were resistant to trimethoprim-sulphamethoxazole (co-trimoxazole).

CONCLUSIONS

In vitro resistance in S. pneumoniae to co-trimoxazole treatment was high, and the majority of isolates had intermediate resistance to penicillin. To inform treatment policies on the clinical efficacy of current treatment protocols for pneumonia in health facilities and at the community level, routine surveillance of resistance in pneumonia pathogens is needed as well as research on treatment efficacy in cases with resistant strains. Improved clinical algorithms and diagnostics for pneumonia should be developed.

Antimicrobial profiles of bacterial clinical isolates from the Gabonese National Laboratory of Public Health: data from routine activity

BACKGROUND

The present study is one of the first to provide a picture of antimicrobial resistance for a range of bacteria and antimicrobial classes in Gabon, Central Africa.

METHODS

During the year 2010, 146 urine cytology, 143 blood cultures, 107 vaginal swabs, 23 urethral swabs, and 18 other culture examinations were positives. All isolates were tested for antibiotic sensitivity.

RESULTS

Four hundred thirty-seven microorganisms were isolated: 210 enterobacteria, 166 staphylococci, 38 streptococci, 14 Acinetobacter, and nine Stenotrophomonas. Of the Klebsiella isolates, 18% and 30% were found to be resistant to selected third-generation cephalosporins (3CG) and fourth-generation cephalosporins (4CG), respectively. Sixty-seven percent of Escherichia coli isolates were resistant to amoxicillin with clavulanic acid. Between 3% and 30% of E. coli isolates were resistant to selected 3CG. All Enterobacter cloacae isolates were sensitive to imipenem. Resistance to quinolones/fluoroquinolones was seen in 21-50% of E. coli isolates. Twenty-six percent of E. cloacae showed resistance to ceftazidime and 37% to cefotaxime. The resistance rate to quinolones ranged between 58% and 78%. Thirty-two percent of Staphylococcus isolates were resistant to gentamicin. Low resistance rates to teicoplanin (2-4%) were observed. Thirty-seven percent of isolated Staphylococcus aureus and 61% of isolated Staphylococcus saprophyticus were resistant to both penicillin G and oxacillin. Streptococcus isolates had low resistance rates to erythromycin, ceftriaxone, and ciprofloxacin (5%, 7%, and 14%, respectively) and were highly resistant to tetracycline, gentamicin, and sulfamethoxazole-trimethoprim (92%, 91%, and 62%, respectively).

CONCLUSIONS

The antimicrobial resistance profiles seen here are of concern. To control the spread of drug-resistant bacteria, clinicians should be cognizant of their local antimicrobial resistance patterns.

Fluoroquinolone-resistant pneumococci: dynamics of serotypes and clones in Spain in 2012 compared with those from 2002 and 2006

In Spain, rates of ciprofloxacin resistance in pneumococci were low during the last decade (2.6% in 2002 and 2.3% in 2006). In 2012, the rate remained at 2.3%, equivalent to 83 of 3,621 isolates. Of the 83 resistant isolates, 15 showed a low level (MIC of 4 to 8 μg/ml) and 68 a high level (MIC of 16 to 128 μg/ml) of ciprofloxacin resistance. Thirteen low-level-resistant isolates had single changes in ParC, one had a single ParE change, and one did not present any mutations. High-level-resistant isolates had GyrA changes plus additional ParC and/or ParE changes: 51, 15, and 2 isolates had 2, 3, or 4 mutations, respectively. Although 24 different serotypes were observed, 6 serotypes accounted for 51.8% of ciprofloxacin-resistant isolates: 8 (14.5%), 19A (10.8%), 11A (7.2%), 23A (7.2%), 15A (6.0%), and 6B (6.0%). A decrease in pneumococcal 7-valent conjugate vaccine (PCV7) serotypes was observed from 2006 (35.7%) to 2012 (16.9%), especially of serotype 14 (from 16.3% to 2.4%; P<0.001). In comparison with findings in 2006, multidrug resistance was greater in 2012 (P=0.296), mainly due to the increased presence and/or emergence of clonal complexes associated with non-PCV7 serotypes: CC63 expressing serotypes 8, 15A, and 19A; CC320 (with serotype 19A); and CC42 (with serotype 23A). Although rates of ciprofloxacin resistance remained low and stable throughout the last decade, changes in serotype and genotype distributions were observed in 2012, notably the expansion of a preexisting multidrug-resistant clone, CC63, and the emergence of the CC156 clone expressing serotype 11A.

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.

The fluoroquinolone levofloxacin triggers the transcriptional activation of iron transport genes that contribute to cell death in Streptococcus pneumoniae

We studied the transcriptomic response of Streptococcus pneumoniae to levofloxacin (LVX) under conditions inhibiting topoisomerase IV but not gyrase. Although a complex transcriptomic response was observed, the most outstanding result was the upregulation of the genes of the fatDCEB operon, involved in iron (Fe(2+) and Fe(3+)) uptake, which were the only genes varying under every condition tested. Although the inhibition of topoisomerase IV by levofloxacin did not have a detectable effect in the level of global supercoiling, increases in general supercoiling and fatD transcription were observed after topoisomerase I inhibition, while the opposite was observed after gyrase inhibition with novobiocin. Since fatDCEB is located in a topological chromosomal domain downregulated by DNA relaxation, we studied the transcription of a copy of the 422-bp (including the Pfat promoter) region located upstream of fatDCEB fused to the cat reporter inserted into the chromosome 106 kb away from its native position: PfatfatD was upregulated in the presence of LVX in its native location, whereas no change was observed in the Pfatcat construction. Results suggest that topological changes are indeed involved in PfatfatDCE transcription. Upregulation of fatDCEB would lead to an increase of intracellular iron and, in turn, to the activation of the Fenton reaction and the increase of reactive oxygen species. In accordance, we observed an attenuation of levofloxacin lethality in iron-deficient media and in a strain lacking the gene coding for SpxB, the main source of hydrogen peroxide. In addition, we observed an increase of reactive oxygen species that contributed to levofloxacin lethality.

Thoracic and abdominal lymphatic pump techniques inhibit the growth of S. pneumoniae bacteria in the lungs of rats

BACKGROUND

Osteopathic physicians utilize manual medicine techniques called lymphatic pump techniques (LPT) to improve lymphatic flow and enhance immunity. Clinical studies report that LPT enhances antibody responses to bacterial vaccines, shortens duration of cough in patients with respiratory disease, and shortens the duration of intravenous antibiotic therapy and hospital stay in patients with pneumonia. The purpose of this study was to identify if thoracic LPT (Th-LPT) or abdominal LPT (Ab-LPT) would reduce Streptococcus pneumoniae colony-forming units (CFU) in the lungs of rats with acute pneumonia.

METHODS AND RESULTS

Rats were nasally infected with S. pneumoniae and received either control, sham, Ab-LPT, or Th-LPT once daily for 3 consecutive days. On day 4 post-infection, lungs were removed and bacteria were enumerated. Three daily applications of either Ab-LPT or Th-LPT were able to significantly (p<0.05) reduce the numbers of pulmonary bacteria compared to control and sham. There were no significant differences in the percentage or concentration of leukocytes in blood between groups, suggesting neither Ab-LPT nor Th-LPT release leukocytes into blood circulation.

CONCLUSIONS

Our data demonstrate that LPT may protect against pneumonia by inhibiting bacterial growth in the lung; however, the mechanism of protection is unclear. Once these mechanisms are understood, LPT can be optimally applied to patients with pneumonia, which may substantially reduce morbidity, mortality, and frequency of hospitalization.

Cumulative clinical experience from over a decade of use of levofloxacin in community-acquired pneumonia: critical appraisal and role in therapy

Levofloxacin is the synthetic L-isomer of the racemic fluoroquinolone, ofloxacin. It interferes with critical processes in the bacterial cell such as DNA replication, transcription, repair, and recombination by inhibiting bacterial topoisomerases. Levofloxacin has broad spectrum activity against several causative bacterial pathogens of community-acquired pneumonia (CAP). Oral levofloxacin is rapidly absorbed and is bioequivalent to the intravenous formulation such that patients can be conveniently transitioned between these formulations when moving from the inpatient to the outpatient setting. Furthermore, levofloxacin demonstrates excellent safety, and has good tissue penetration maintaining adequate concentrations at the site of infection. The efficacy and tolerability of levofloxacin 500 mg once daily for 10 days in patients with CAP are well established. Furthermore, a high-dose (750 mg) and short-course (5 days) of once-daily levofloxacin has been approved for use in the US in the treatment of CAP, acute bacterial sinusitis, acute pyelonephritis, and complicated urinary tract infections. The high-dose, short-course levofloxacin regimen maximizes its concentration-dependent antibacterial activity, decreases the potential for drug resistance, and has better patient compliance.

Tn916-like genetic elements: a diverse group of modular mobile elements conferring antibiotic resistance

Antibiotic-resistant Gram-positive bacteria are responsible for morbidity and mortality in healthcare environments. Enterococcus faecium, Enterococcus faecalis, Staphylococcus aureus and Streptococcus pneumoniae can all exhibit clinically relevant multidrug resistance phenotypes due to acquired resistance genes on mobile genetic elements. It is possible that clinically relevant multidrug-resistant Clostridium difficile strains will appear in the future, as the organism is adept at acquiring mobile genetic elements (plasmids and transposons). Conjugative transposons of the Tn916/Tn1545 family, which carry major antibiotic resistance determinants, are transmissible between these different bacteria by a conjugative mechanism during which the elements are excised by a staggered cut from donor cells, converted to a circular form, transferred by cell-cell contact and inserted into recipient cells by a site-specific recombinase. The ability of these conjugative transposons to acquire additional, clinically relevant antibiotic resistance genes importantly contributes to the emergence of multidrug resistance.

Canadian clinical practice guidelines for acute and chronic rhinosinusitis

This document provides healthcare practitioners with information regarding the management of acute rhinosinusitis (ARS) and chronic rhinosinusitis (CRS) to enable them to better meet the needs of this patient population. These guidelines describe controversies in the management of acute bacterial rhinosinusitis (ABRS) and include recommendations that take into account changes in the bacteriologic landscape. Recent guidelines in ABRS have been released by American and European groups as recently as 2007, but these are either limited in their coverage of the subject of CRS, do not follow an evidence-based strategy, or omit relevant stakeholders in guidelines development, and do not address the particulars of the Canadian healthcare environment.

Advances in understanding the pathophysiology of CRS, along with the development of appropriate therapeutic strategies, have improved outcomes for patients with CRS. CRS now affects large numbers of patients globally and primary care practitioners are confronted by this disease on a daily basis. Although initially considered a chronic bacterial infection, CRS is now recognized as having multiple distinct components (eg, infection, inflammation), which have led to changes in therapeutic approaches (eg, increased use of corticosteroids). The role of bacteria in the persistence of chronic infections, and the roles of surgical and medical management are evolving. Although evidence is limited, guidance for managing patients with CRS would help practitioners less experienced in this area offer rational care. It is no longer reasonable to manage CRS as a prolonged version of ARS, but rather, specific therapeutic strategies adapted to pathogenesis must be developed and diffused.

Guidelines must take into account all available evidence and incorporate these in an unbiased fashion into management recommendations based on the quality of evidence, therapeutic benefit, and risks incurred. This document is focused on readability rather than completeness, yet covers relevant information, offers summaries of areas where considerable evidence exists, and provides recommendations with an assessment of strength of the evidence base and degree of endorsement by the multidisciplinary expert group preparing the document.

These guidelines have been copublished in both Allergy, Asthma & Clinical Immunology and the Journal of Otolaryngology-Head and Neck Surgery.

Molecular characterization of erm(B)- and mef(E)-mediated erythromycin-resistant Streptococcus pneumoniae in China and complete DNA sequence of Tn2010

AIMS

To characterize the erm(B)- and mef(E)-mediated erythromycin-resistant Streptococcus pneumoniae clinical isolates obtained from ten hospitals located different cities in China.

METHODS AND RESULTS

Totally 83 S. pneumoniae were collected, and eighteen representative strains of 66 strains that exhibited erythromycin resistance were used for further characterization by antibiograms, serotyping, PFGE, MLST, DNA sequencing of the macrolide-resistance elements and mapping of the elements on the chromosome. Twelve isolates showed a high-level resistance to erythromycin, and six other isolates showed a low-level resistance to erythromycin. Thirteen isolates harboured a Tn2010 transposon (26·4 kbp) encoding the erm(B), tet(M) and mef(E) genes and were classified into three types by Tn2010 structures. The remaining five isolates harboured a Tn6002 transposon (20·9 kbp) encoding the erm(B) and tet(M) genes and were classified into three types by Tn6002 locations on the chromosome. Three of the Tn6002 elements were located within the Tn5252-like element, implying that these composed a large mobile element. The MLST analyses showed that several clones had been disseminated and that the CC271 strains carrying the Tn2010 element expressing the high-level resistance to erythromycin were predominant in China. Four new MLST strains, which were designated as ST3262, ST3263, ST3397 and ST3398 were also identified.

CONCLUSIONS

The erythromycin resistance determinant of S.pneumoniae that had been isolated in China was located in Tn2010 or the Tn6002 element and several clones had been disseminated, and the CC271 strains carrying the Tn2010 element expressing the high-level resistance to erythromycin were predominant in China.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first molecular analysis of erythromycin-resistant Streptococcus pneumoniae clinical isolates in China, and the first report of the complete nucleotide sequence of Tn2010 (26,390 bp).

Levofloxacin in the treatment of community-acquired pneumonia

Levofloxacin is a fluoroquinolone that has a broad spectrum of activity against several causative bacterial pathogens of community-acquired pneumonia (CAP). The efficacy and tolerability of levofloxacin 500 mg once daily for 10 days in patients with CAP are well established. Furthermore, a high-dose (750 mg), short-course (5 days) of once-daily levofloxacin has been approved for use in the USA in the treatment of CAP, acute bacterial sinusitis, acute pyelonephritis and complicated urinary tract infections. Levofloxacin can be used as a monotherapy in patients with CAP, however, levofloxacin combination therapy with anti-pseudomonal beta-lactam (or aminoglycoside) should be considered if Pseudomonas aeruginosa is the causative pathogen of the respiratory infection. The high-dose, short-course levofloxacin regimen maximizes its concentration-dependent antibacterial activity, decreases the potential for drug resistance and has better patient compliance. Oral levofloxacin is rapidly absorbed and is bioequivalent to the intravenous formulation and the patients can switch between these formulations, which results in more options with respect to the therapeutic regimens. Furthermore, levofloxacin is generally well tolerated, has good tissue penetration and adequate concentrations can be maintained at the site of infections.

Characterization of the quinolone resistant determining regions in clinical isolates of pneumococci collected in Canada

BACKGROUND

The objective of this study was to examine Streptococcus pneumoniae isolates collected from a longitudinal surveillance program in order to determine their susceptibility to currently used fluoroquinolones and of the frequency and type of mutations in the quinolone-resistant determining regions (QRDRs) of their parC and gyrA genes.

METHODS

The Canadian Bacterial Surveillance Network has been collecting clinical isolates of S. pneumoniae from across Canada since 1988. Broth microdilution susceptibility testing was carried out according to the Clinical and Laboratory Standards Institute guidelines. The QRDRs of the parC and gyrA genes were sequenced for all isolates with ciprofloxacin MIC > or = 4 mg/L, and a large representative sample of isolates (N = 4,243) with MIC < or = 2 mg/L.

RESULTS

A total of 4,798 out of 30,111 isolates collected from 1988, and 1993 to 2007 were studied. Of those isolates that were successfully sequenced, 184 out of 1,032 with mutations in parC only, 11 out of 30 with mutations in gyrA only, and 292 out of 298 with mutations in parC and gyrA were considered resistant to ciprofloxacin (MIC > or = 4 mg/L). The most common substitutions in the parC were at positions 137 (n = 722), 79 (n = 209), and 83 (n = 56), of which substitutions at positions 79 and 83 were associated with 4-fold increase in MIC to ciprofloxacin, whereas substitutions at position 137 had minimal effect on the ciprofloxacin MIC. A total of 400 out of 622 isolates with Lys-137 parC mutation belonged to serotypes 1, 12, 31, 7A, 9V, 9N and 9L, whereas only 49 out of 3064 isolates with no mutations belonged to these serotypes. Twenty-one out of 30 isolates with substitutions at position 81 of the gyrA gene had an increased MIC to ciprofloxacin. Finally, we found that isolates with mutations in both parC and gyrA were significantly associated with increased MIC to fluoroquinolones.

CONCLUSIONS

Not all mutations, most frequently Lys-137, found in the QRDRs of the parC gene of S. pneumoniae is associated with an increased MIC to fluoroquinolones. The high prevalence of Lys-137 appears to be due to its frequent occurrence in common serotypes.

What can we learn from the time course of untreated and partially treated community-onset Streptococcus pneumoniae pneumonia? A clinical perspective on superiority and noninferiority trial designs for mild community-acquired pneumonia

There are no well-designed placebo-controlled clinical trials in the recent era that precisely define the magnitude of the drug effect of antimicrobial therapy for mild community-acquired pneumonia (CAP). However, there is evidence that ineffective therapies, selected on the basis of the ratio of 24-h area under the concentration curve to minimum inhibitory concentration, associated with a discordant (nonsusceptible in vitro) specific agent (or no therapy) for mild CAP due to Streptococcus pneumoniae are associated with increased risk of progression to serious CAP. The relatively high rate of clinical success associated with appropriate antimicrobial treatment of mild CAP renders a standard outcome measure of clinical success an unlikely way to differentiate new agents. However, there may be an advantage in composite outcome assessments for mild CAP. Composite-outcomes end points that include time to resolution of morbidity, the use of patient reported-outcomes instruments, and biomarkers are recommended for future studies. Because the composite rate of success in recent randomized clinical trials exceeds 90%, it would seem that a noninferiority margin of 10% is reasonable for trials for mild CAP.

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.

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.

[Reducing the duration of antibiotic therapy in acute community-acquired pneumonia]

In theory, the expected benefits of a reduction of the duration of antibiotic therapy during the immunocompetent adult's community-acquired pneumonia (CAP) are of four types: improved observance; reduction of the iatrogenic risk; decrease in the emergence of resistance in the commensal flora; reduction in direct and indirect costs. In practice, the expected benefits must be weighed against the risks of lesser efficiency, i.e., continuing evolution or recurrence. The experimental models of humanized pneumonia treatments show that the period of bacterial eradication is not uniform. If it lasts 48 hours for pneumonia with sensitive pneumococci, it is longer for pneumococci resistant to amoxicillin or atypical bacteria. Thus, if the clinical trials conducted in adults with non-severe CAP, have shown that the duration of treatment could be reduced, depending on the existence or not of a comorbidity, to a 3 days amoxicillin treatment, to a 5 days telithromycin treatment, to a 5 days of levofloxacin 750 mg/day treatment or to a 5 days of ceftriaxone 1g / day treatment, it is logical to assume that such reductions cannot be extrapolated to severe unqualified PACs with severe or to those caused by resistant bacteria or atypical bacteria.

In vitro and in vivo antibacterial activities of DC-159a, a new fluoroquinolone

DC-159a is a new 8-methoxy fluoroquinolone that possesses a broad spectrum of antibacterial activity, with extended activity against gram-positive pathogens, especially streptococci and staphylococci from patients with community-acquired infections. DC-159a showed activity against Streptococcus spp. (MIC(90), 0.12 microg/ml) and inhibited the growth of 90% of levofloxacin-intermediate and -resistant strains at 1 microg/ml. The MIC 90s of DC-159a against Staphylococcus spp. were 0.5 microg/ml or less. Against quinolone- and methicillin-resistant Staphylococcus aureus strains, however, the MIC 90 of DC-159a was 8 microg/ml. DC-159a was the most active against Enterococcus spp. (MIC 90, 4 to 8 microg/ml) and was more active than the marketed fluoroquinolones, such as levofloxacin, ciprofloxacin, and moxifloxacin. The MIC 90s of DC-159a against Haemophilus influenzae, Moraxella catarrhalis, and Klebsiella pneumoniae were 0.015, 0.06, and 0.25 microg/ml, respectively. The activity of DC-159a against Mycoplasma pneumoniae was eightfold more potent than that of levofloxacin. The MICs of DC-159a against Chlamydophila pneumoniae were comparable to those of moxifloxacin, and DC-159a was more potent than levofloxacin. The MIC 90s of DC-159a against Peptostreptococcus spp., Clostridium difficile, and Bacteroides fragilis were 0.5, 4, and 2 microg/ml, respectively; and among the quinolones tested it showed the highest level of activity against anaerobic organisms. DC-159a demonstrated rapid bactericidal activity against quinolone-resistant Streptococcus pneumoniae strains both in vitro and in vivo. In vitro, DC-159a showed faster killing than moxifloxacin and garenoxacin. The bactericidal activity of DC-159a in a murine muscle infection model was revealed to be superior to that of moxifloxacin. These activities carried over to the in vivo efficacy in the murine pneumonia model, in which treatment with DC-159a led to bactericidal activity superior to those of the other agents tested.

Antipneumococcal activity of ertapenem compared with gatifloxacin in a temperature-sensitive murine model of acute pneumonia

Fluoroquinolone-resistance among pneumococci is low; however the number of isolates with a single ParC mutation has increased. Consequently, more potent agents are needed to minimize resistance selection. We investigated the efficacy of ertapenem versus gatifloxacin in a temperature-sensitive mouse model of pneumonia caused by a wildtype Streptococcus pneumoniae strain (A66) and an isogenic mutant with a ParC mutation (R222). Treatment started at 24 h and lasted for 5 days. Temperature was used to assess disease progression before and during treatment. Of mice infected with either strain and treated at an early stage of infection, 79-94% of those given ertapenem survived compared with 56-61% given gatifloxacin. If treated at a later stage, the results were similar for ertapenem (71-84%) but were considerably lower for gatifloxacin (17-33%). Ertapenem was as bactericidal as gatifloxacin against A66 (94-100% vs 92-100%) but was superior to gatifloxacin against R222 (95-100% vs 50-77%). Ertapenem is a promising new treatment for patients with pneumococcal pneumonia, including those at risk of infection with a fluoroquinolone-resistant strain.

Antibacterial resistance patterns in Streptococcus pneumoniae isolated from elderly patients: PROTEKT years 1-5 (1999-2004)

The antibacterial susceptibilities of 6,646 Streptococcus pneumoniae isolates collected in 38 countries from patients >or=65 years of age with community-acquired respiratory tract infections (RTIs) during years 1-5 of the PROTEKT study (1999-2004) were analysed. Rates of erythromycin resistance (36.0%), penicillin non-susceptibility (31.3%; 20.2% resistant plus 11.1% intermediately susceptible) and resistance to multiple antibacterials (37.2%) were stable over the 5 years. The most common macrolide resistance mechanism was erm(B) (61.4%); erm(B)+mef(A) strains increased from 5.4% (year 1) to 7.4% (year 5) (P=0.037). Overall, 37.2% of isolates exhibited resistance to two or more antibacterials, including 15.9% resistant to both penicillin and erythromycin. Antibacterial resistance was highest in the Far East. Telithromycin resistance was rare (0.12%). Appropriate alternative empirical first-line therapies may be required for treating community-acquired RTIs in the elderly.

Clinical impact of antibiotic resistance in respiratory tract infections

Streptococcus pneumoniae is the most common causative pathogen of community-acquired respiratory tract infections. In vitro evidence indicates that S. pneumoniae is increasingly resistant to commonly prescribed antimicrobial agents including the macrolides. The clinical relevance of resistance, however, has not been clearly established. This article reviews the risk factors influencing selection of resistant pneumococci, discusses endpoints used to assess the impact of resistance on clinical outcome, and proposes strategies to minimise the impact of resistance. Evidence demonstrating treatment failures due to macrolide-resistant S. pneumoniae is also reviewed. Increasing rates of resistance among S. pneumoniae present numerous clinical challenges, and require carefully selected treatment strategies to preserve antibacterial efficacy. Antibiotics with a low propensity for stimulating resistance should be chosen wherever possible.

Fitness costs of fluoroquinolone resistance in Streptococcus pneumoniae

The fitness cost of the genes responsible for resistance to fluoroquinolones in clinical isolates of Streptococcus pneumoniae were estimated in vitro in a common genetic background. Naturally occurring parC, parE, and gyrA loci containing mutations in the quinolone-resistance-determining regions were introduced by transformation into S. pneumoniae strain R6 individually and in combinations. The fitness of these transformants was estimated by pairwise competition experiments with a common R6 strain. On average, single par and gyr mutants responsible for low-level MIC resistance (first-step resistance) impose a fitness burden of approximately 8%. Some of these mutants engender no measurable cost, while one, a parE mutant, reduces the fitness of these bacteria by more than 40%. Most interestingly, the addition of the second par or gyr mutations required for clinically significant, high-MIC fluoroquinolone resistance does not increase the fitness burden imposed by these single genes and can even reduce it. We discuss the implications of these results for the epidemiology of fluoroquinolone resistance and the evolution of acquired resistance in treated patients.

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.

Macrolide resistance in bacteremic pneumococcal disease: implications for patient management

BACKGROUND

Despite pneumococcal antibiotic resistance rates in excess of 25%, macrolides remain first-line agents for the treatment of community-acquired pneumonia.

METHODS

Prospective, population-based surveillance was conducted to identify cases of pneumococcal bacteremia in Toronto and Peel, Canada, between 2000 and 2004. "Macrolide failures" were defined as cases of bacteremia occurring during outpatient treatment with macrolide antibiotics or within 2 days after treatment. Macrolide susceptibility was determined according to Clinical Laboratory Standards Institute guidelines; common macrolide resistance mechanisms were determined by genotyping.

RESULTS

During the 5 years of surveillance, there were 1696 episodes of pneumococcal bacteremia (8.5 cases/100,000 population/year), of which 60 (3.5%) were failures of outpatient macrolide therapy. Resistant isolates were more common among cases of bacteremia after failure of macrolide therapy (37 [64%] of 58 cases) than among cases of bacteremia after failure of nonmacrolide antibiotics (16 [22%] of 74 cases; P<.001) or cases of bacteremia that occurred without prior antibiotic therapy (193 [12%] of 1569 cases; P<.001). Macrolide failures were significantly more common among cases of pneumococcal bacteremia with isolates exhibiting an erythromycin MIC of 1 microg/mL than among isolates exhibiting MICs < or = 0.25 microg/mL (3 [38%] of 8 cases vs. 21 [1.5%] of 1394 cases of bacteremia; P<.001). Increases in the MIC to 1 microg/mL were not associated with further increases in the likelihood of macrolide failure. Low-level resistance conferred by mefA and high-level resistance conferred by ermB were equally overrepresented among macrolide failures.

CONCLUSIONS

Macrolide resistance contributes to an increased risk of macrolide failure, irrespective of the underlying resistance mechanism or of the degree of elevation in erythromycin MIC.