Clinical implications and treatment of multiresistant Streptococcus pneumoniae pneumonia

Exploring the synthetic approaches and clinical prowess of established macrocyclic pharmaceuticals

Macrocyclic compounds, characterized by cyclic structures, often originate from either modified forms of unicyclic canonical molecules or natural products. Within the field of medicinal chemistry, there has been a growing fascination with drug-like macrocycles in recent years, primarily due to compelling evidence indicating that macrocyclization can significantly influence both the biological and physiochemical properties, as well as the selectivity, when compared to their acyclic counterparts. The approval of contemporary pharmaceutical agents like Lorlatinib underscore the notable clinical relevance of drug-like macrocycles. Nonetheless, the synthesis of these drug-like macrocycles poses substantial challenges, primarily stemming from the complexity of ring-closing reactions, which are inherently dependent on the size and geometry of the bridging linker, impacting overall yields. Nevertheless, macrocycles offer a promising avenue for expanding the synthetic toolkit in medicinal chemistry, enabling the creation of bioactive compounds. To shed light on the subject, we delve into the clinical prowess of established macrocyclic drugs, spanning various therapeutic areas, including oncology, and infectious diseases. Case studies of clinically approved macrocyclic agents illustrate their profound impact on patient care and disease management. As we embark on this journey through the world of macrocyclic pharmaceuticals, we aim to provide a comprehensive overview of their synthesis and clinical applications, shedding light on the pivotal role they play in modern medicine.

Antibiotic persistence and its impact on the environment

From boon molecules to molecules contributing to rising concern has been the sojourn of antibiotics. The problem of antibiotic contamination has gotten worse due to antibiotics' pervasive use in every aspect of the environment. One such consequence of pollution is the increase in infections with antibiotic resistance. All known antimicrobials being used for human benefit lead to their repetitive and routine release into the environment. The misuse of antibiotics has aggravated the situation to a level that we are short of antibiotics to treat infections as organisms have developed resistance against them. Overconsumption is not just limited to human health care, but also occurs in other areas such as aquaculture, livestock, and veterinary applications for the purpose of improving feed and meat products. Due to their harmful effects on non-target species, the trace level of antibiotics in the aquatic ecosystem presents a significant problem. Since the introduction of antibiotics into the environment is more than their removal, they have been given the status of persistent pollutants. The buildup of antibiotics in the environment threatens aquatic life and may lead to bacterial strains developing resistance. As newer organisms are becoming resistant, there exists a shortage of antibiotics to treat infections. This has presented a very critical problem for the health-care community. Another rising concern is that the development of newer drug molecules as antibiotics is minimal. This review article critically explains the cause and nature of the pollution and the effects of this emerging trend. Also, in the latter sections, why we need newer antibiotics is questioned and discussed.

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

Background:

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

Methods:

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

Results:

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

Conclusion:

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

Multicenter study of pneumococcal carriage in children 2 to 4 years of age in the winter seasons of 2017-2019 in Irbid and Madaba governorates of Jordan

Streptococcus pneumoniae is one of the leading causes of death worldwide. It disseminates through colonizers and causes serious infections. Aims of this study are to determine pneumococcal carriage rate, resistance, serotype distribution, and coverage of pneumococcal conjugate vaccines from children attending day care centers from Irbid and Madaba in Jordan. Nasopharyngeal swabs were collected from day care centers (DCCs) of healthy Jordanian children 2–4 years of age from four regions of Madaba (n = 596), and from eastern Irbid (n = 423). Swabs were cultivated on Columbia blood agar base supplemented with 5% sheep blood and incubated for 18–24 hours at 37°C with 5% CO₂. Alpha-hemolytic isolates were tested for optochin sensitivity and bile solubility for identification. Isolates were analyzed for antimicrobial susceptibility by the Vitek2 system and E-test (BioMérieux). Serotyping was performed using the Neufeld Quellung method. A total of 341 pneumococcal strains were isolated from 1019 nasopharyngeal (NP) samples of healthy children attending DCCs for two winter seasons from 2017–2019. Carriage rate in eastern Irbid for both seasons was 29.6% and for Madaba 37.9%. Resistance rates for Irbid and Madaba, respectively, were as follows: Penicillin (86.3%; 94.4%), erythromycin (57.0%; 78.2%), clindamycin (30.8%; 47.2%), trimethoprim-sulfamethoxazole (68.6%; 86.6%), and tetracycline (45.7%; 51.9%). Predominant serotypes for Irbid were 19F (20.8%), 23F (12.0%), 6A (10.4%), and 6B (9.6%); whereas for Madaba were 19F (24.5%), 14 (7.4%), 6A (6.9%) and 23F (6.5%). Serotype coverage of the thirteen valent pneumococcal conjugate vaccine (PCV13) was about 65% for both regions. Over 96% of isolates with PCV13 serotypes in this study were resistant to penicillin with the exception of serotypes 3 and 5. As a conclusion resistance and carriage rates among the age group 2 to 4 years reached an alarming rate especially among vaccine types, which can be controlled by pneumococcal conjugate vaccination strategies.

Animal Models of Pneumococcal pneumonia

Streptococcus pneumoniae remains the most common bacterial pathogen causing lower respiratory tract infections and is a leading cause of morbidity and mortality worldwide, especially in children and the elderly. Another important aspect related to pneumococcal infections is the persistent rate of penicillin and macrolide resistance. Therefore, animal models have been developed to better understand the pathogenesis of pneumococcal disease and test new therapeutic agents and vaccines. This narrative review will focus on the characteristics of the different animal pneumococcal pneumonia models. The assessment of the different animal models will include considerations regarding pneumococcal strains, microbiology properties, procedures used for bacterial inoculation, pathogenesis, clinical characteristics, diagnosis, treatment, and preventive approaches.

Community-Acquired Pneumonia

Community-acquired pneumonia is one of the most common infections seen in emergency department patients. There is a wide spectrum of disease severity and viral pathogens are common. After a careful history and physical examination, chest radiographs may be the only diagnostic test required. The first step in management is risk stratification, using a validated clinical decision rule and serum lactate, followed by early antibiotics and fluid resuscitation when indicated. Antibiotics should be selected with attention to risk factors for multidrug-resistant respiratory pathogens. Broad use of pneumococcal vaccine in adults and children can prevent severe community-acquired pneumonia.

Antimicrobial Stewardship in Long-Term Care Facilities: Approaches to Creating an Antibiogram when Few Bacterial Isolates Are Cultured Annually

Antibiograms are important clinical tools to report and track antibiotic susceptibility and help guide empiric antimicrobial therapy. Antibiograms support compliance with antimicrobial stewardship (AMS) requirements from the Centers for Medicare and Medicaid Services and are in line with recommendations from the Centers for Disease Control and Prevention Core Elements of AMS for nursing homes/long-term care facilities (LTCFs). Unlike most acute-care settings, LTCFs are challenged in creating antibiograms because of the low number of bacterial isolates collected annually. Determining the best methodology for creating clinically useful antibiograms for LTCFs needs to be explored. Possible approaches include (1) extending the isolate data beyond 1 year, (2) combining isolate data from the same geographic region, (3) using a nearby acute-care facility's antibiogram as a proxy, or (4) collapsing isolate data. This article discusses the benefits and limitations of each approach.

In Vitro Activity of the Novel Lactone Ketolide Nafithromycin (WCK 4873) against Contemporary Clinical Bacteria from a Global Surveillance Program

Nafithromycin (WCK 4873), a novel antimicrobial agent of the lactone ketolide class, is currently in phase 2 development for treatment of community-acquired bacterial pneumonia (CABP). A total of 4,739 nonduplicate isolates were selected from a 2014 global surveillance program at medical institutions located in 43 countries within the United States, Europe, Latin America, and the Asia-Pacific region. Nafithromycin and comparator agents were used for susceptibility testing by reference broth microdilution methods. Nafithromycin was active against Staphylococcus aureus (MIC_50/90, 0.06/>2 μg/ml), including erythromycin-resistant strains exhibiting an inducible clindamycin resistance phenotype (MIC_50/90, 0.06/0.06 μg/ml) and telithromycin-susceptible strains (MIC_50/90, 0.06/0.06 μg/ml), but it exhibited limited activity against most telithromycin-resistant and clindamycin-resistant isolates that were constitutively resistant to macrolides (MIC_50/90, >2/>2 μg/ml). Nafithromycin was very active (MIC_50/90, 0.015/0.06 μg/ml) against 1,911 Streptococcus pneumoniae strains, inhibiting all strains, with MIC values of ≤0.25 μg/ml. Telithromycin susceptibility was 99.9% for Streptococcus pneumoniae strains, and nafithromycin was up to 8-fold more potent than telithromycin. Overall, 37.9% of S. pneumoniae strains were resistant to erythromycin, and 19.7% were resistant to clindamycin. Nafithromycin was highly active against 606 Streptococcus pyogenes strains (MIC_50/90, 0.015/0.015 μg/ml), inhibiting 100.0% of isolates at ≤0.5 μg/ml, and MIC_50/90 values (0.015/0.015 to 0.03 μg/ml) were similar for the 4 geographic regions. Nafithromycin and telithromycin demonstrated comparable in vitro activities against 1,002 Haemophilus influenzae isolates and 504 Moraxella catarrhalis isolates. Overall, nafithromycin showed potent in vitro activity against a broad range of contemporary (2014) global pathogens. These results support the continued clinical development of nafithromycin for treatment of CABP.

Risk Factors for Drug-Resistant Cap in Immunocompetent Patients

PURPOSE OF REVIEW

The increase in drug-resistant community-acquired pneumonia (CAP) is an important problem all over the world. This article explores the current state of antimicrobial resistance of different bacteria that cause CAP and also assesses risk factors to identify those pathogens.

RECENT FINDINGS

In the last two decades, it has been documented that there is a significant increase in drug-resistant Streptococcus pneumoniae and other bacteria causing CAP. The most important risk factors are overuse of antibiotics, prior hospitalization, and lung comorbidities. The direct consequences can be severe, including prolonged stays in hospital, increased costs, and morbi-mortality. However, drug-resistant CAP declined after the introduction of the pneumococcal conjugate vaccine. This review found an increase in resistance to the antibiotics used in CAP, and the risk factor can be used for identifying patients with drug-resistant CAP and initiate appropriate treatment. Judicious use of antibiotics and the development of effective new vaccines are needed.

Streptococcus pneumoniae proteomics: determinants of pathogenesis and vaccine development

Streptococcus pneumoniae is a major pathogen that is responsible for a variety of invasive diseases. The bacteria gain entry initially by establishing a carriage state in the nasopharynx from where they migrate to other sites in the body. The worldwide distribution of the bacteria and the severity of the diseases have led to a significant level of interest in the development of vaccines against the bacteria. Current vaccines, based on the bacterial polysaccharide, have a number of limitations including poor immunogenicity and limited effectiveness against all pneumococcal serotypes. There are many challenges in developing vaccines that will be effective against the diverse range of isolates and serotypes for this highly variable bacterial pathogen. This review considers how proteomic technologies have extended our understanding of the pathogenic mechanisms of nasopharyngeal colonization and disease development as well as the critical areas in developing protein-based vaccines.

Antimicrobial activity of ceftaroline tested against bacterial isolates causing respiratory tract and skin and skin structure infections in US medical centers in 2013

A total of 4533 isolates from community-acquired respiratory tract infections (CARTIs) and 8446 from skin and skin structure infections (SSSIs) were consecutively collected in 149 US medical centers in 2013. Strains were susceptibility tested by broth microdilution method against ceftaroline and numerous comparators. Ceftaroline (MIC(50/90), ≤0.015/0.12 μg/mL) was more potent than ceftriaxone (MIC(50/90), ≤0.06/1 μg/mL) against Streptococcus pneumoniae and highly active against ceftriaxone-nonsusceptible strains (n=201; MIC(90), 0.25 μg/mL). Ceftaroline was also very active against Haemophilus influenzae (MIC(50/90), 0.008/0.015 μg/mL), methicillin-susceptible (MIC(50/90), 0.25/0.25 μg/mL) and methicillin-resistant Staphylococcus aureus (MIC(50/90), 1/1 μg/mL), and β-hemolytic streptococci (highest MIC, 0.03 μg/mL). Ceftaroline exhibited good activity against non-extended-spectrum β-lactamase (ESBL) phenotype isolates of Klebsiella spp. and Escherichia coli (96.7% susceptible and MIC(90) of 0.25 μg/mL for both) but limited activity against ESBL phenotype isolates. In summary, ceftaroline exhibited potent in vitro activity against a large collection of bacterial isolates causing CARTI and SSSI in US medical centers.

Ceftaroline activity against organisms isolated from respiratory tract infections in USA hospitals: results from the AWARE Program, 2009-2011

The Assessing Worldwide Antimicrobial Resistance Evaluation Program monitors the activity of ceftaroline and comparator agents tested against pathogens causing either respiratory or skin and soft tissue infections. A total of 7733 isolates from patients in 80 medical centers across the United States (USA) identified as respiratory tract pathogens by the infection type and/or specimen site recorded by the submitting laboratory during 2009-2011 were evaluated. There were 3360 isolates of Streptococcus pneumoniae, 1799 Haemophilus influenzae, 1087 Staphylococcus aureus, 678 Moraxella catarrhalis, 459 Klebsiella pneumoniae, 223 Escherichia coli, and 127 Klebsiella oxytoca. Annual penicillin resistance among S. pneumoniae ranged from 21.9 to 24.3%. All S. pneumoniae strains were inhibited at a ceftaroline MIC of ≤0.5 μg/mL with 100.0% of isolates categorized as susceptible. Ceftaroline was 16-fold more active than ceftriaxone and 32-fold more active than amoxicillin-clavulanate against penicillin-resistant pneumococci. Only 49.8% of the penicillin-resistant isolates were susceptible to ceftriaxone. There were a total of 1087 S. aureus (48.9% methicillin-resistant S. aureus [MRSA]) isolates, and the yearly MRSA rate ranged from 47.9 to 49.7%. The ceftaroline MIC50/90 for S. aureus was at 0.25/1 μg/mL; 98.2% susceptible and no resistant strains (≥4 μg/mL). Ceftaroline activity against methicillin-susceptible S. aureus (MSSA) isolates (MIC50 and MIC90, 0.25 and 0.25 μg/mL, respectively; 100% susceptible) was 2- to 4-fold greater than for MRSA (MIC50/90, 0.5/1 μg/mL; 96.2% susceptible). The ceftriaxone MIC90 for MSSA was 4 μg/mL. Ceftaroline was active against H. influenzae (MIC50/90 ≤0.015/0.03 μg/mL; 100.0% susceptible) and against M. catarrhalis (MIC50/90, 0.06/0.12 μg/mL). Ceftaroline was active against non-extended spectrum β-lactamase (ESBL) phenotype strains of Enterobacteriaceae but not against ESBL-positive phenotype strains. In summary, ceftaroline was highly active against a large collection of bacterial pathogens isolated from patients with respiratory tract infections in the USA during 2009 through 2011.

Therapeutic effects of garenoxacin in murine experimental secondary pneumonia by Streptococcus pneumoniae after influenza virus infection

In a pneumococcal pneumonia murine model following influenza virus infection, garenoxacin was more effective than other fluoroquinolones and demonstrated high levels of bacterial eradication in the lung, low mortality, and potent histopathological improvements. Garenoxacin could potentially be used for the treatment of secondary pneumococcal pneumonia following influenza.

Spectrum and potency of ceftaroline against leading pathogens causing community-acquired respiratory tract and skin and soft tissue infections in Latin America, 2010

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil, is a cephalosporin with in vitro bactericidal activity against Gram-positive organisms, including methicillin-susceptible and -resistant Staphylococcus aureus, β-haemolytic and viridans group streptococci, and Streptococcus pneumoniae, as well as common Gram-negative organisms. In this study a total of 986 isolates collected in 2010 from patients in 15 medical centers in five Latin American countries from the Assessing Worldwide Antimicrobial Resistance Evaluation Program were identified as community-acquired respiratory tract or skin and soft tissue infection pathogens. Ceftaroline was the most potent agent tested against S. pneumoniae with a MIC90 value (0.12μg/mL) that was eight-fold lower than ceftriaxone, levofloxacin, and linezolid. Its spectrum of coverage (100.0% susceptible) was similar to tigecycline, linezolid, levofloxacin and vancomycin. Against Haemophilus influenzae and Moraxella catarrhalis, ceftaroline was the most active agent tested. The activity of ceftaroline against S. aureus (including MRSA) was similar to that of vancomycin and tetracycline (MIC90, 1μg/mL) and linezolid (MIC90, 2μg/mL). The β-haemolytic streptococci exhibited 100.0% susceptibility to ceftaroline. Ceftaroline activity against Escherichia coli, Klebsiella spp., and Enterobacter spp. was similar to that of ceftriaxone and ceftazidime. These parenteral cephalosporin agents have potent activity against non-extended-spectrum β-lactamase-phenotype strains, but are not active against extended-spectrum β-lactamase-phenotype strains. These results confirm the in vitro activity of ceftaroline against pathogens common in community-acquired respiratory tract and skin and soft tissue infection in Latin America, and suggest that ceftaroline fosamil could be an important therapeutic option for these infections.

Artesunate has its enhancement on antibacterial activity of β-lactams via increasing the antibiotic accumulation within methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) has now emerged as a predominant and serious pathogen because of its resistance to a large group of antibiotics, leading to high morbidity and mortality. Therefore, to develop new agents against resistance is urgently required. Previously, artesunate (AS) was found to enhance the antibacterial effect of β-lactams against MRSA. In this study, AS was first found to increase the accumulation of antibiotics (daunorubicin and oxacillin) within MRSA by laser confocal microscopy and liquid chromatography-tandem MS method, suggesting the increased antibiotics accumulation might be related to the enhancement of AS on antibiotics. Furthermore, AS was found not to destroy the cell structure of MRSA by transmission electron microscope. AS was found to inhibit gene expressions of important efflux pumps such as NorA, NorB and NorC, but not MepA, SepA and MdeA. In conclusion, our results showed that AS was capable of enhancing the antibacterial activity of β-lactams via increasing antibiotic accumulations within MRSA through inhibiting gene expressions of efflux pumps such as NorA, NorB and NorC, but did not destroy the cell structure of MRSA. AS could be further investigated as a candidate drug for treatment of MRSA infection.

Tigecycline versus levofloxacin in hospitalized patients with community-acquired pneumonia: an analysis of risk factors

INTRODUCTION

This study was conducted to evaluate the efficacy of tigecycline (TGC) versus levofloxacin (LEV) in hospitalized patients with community-acquired pneumonia (CAP) using pooled data and to perform exploratory analyses of risk factors associated with poor outcome.

MATERIALS AND METHODOLOGY

Pooled analyses of 2 phase 3 studies in patients randomized to intravenous (IV) TGC (100 mg, then 50 mg q12h) or IV LEV (500 mg q24h or q12h). Clinical responses at test of cure visit for the clinically evaluable (CE) and clinical modified intention to treat populations were assessed for patients with risk factors including aged ≥65 years, prior antibiotic failure, bacteremia, multilobar disease, chronic obstructive pulmonary disease, alcohol abuse, altered mental status, hypoxemia, renal insufficiency, diabetes mellitus, white blood cell count >30 x 10(9)/L or <4 x 10(9)/L, CURB-65 score ≥2, Fine score category of III to V and at least 2 clinical instability criteria on physical examination.

RESULTS

In the CE population of 574 patients, overall cure rates were similar: TGC (253/282, 89.7%); LEV (252/292, 86.3%). For all but one risk factor, cure rates for TGC were similar to or higher than those for LEV. For individual risk factors, the greatest difference between treatment groups was observed in patients with diabetes mellitus (difference of 22.9 for TGC versus LEV; 95% confidence interval, 4.8 - 39.9).

CONCLUSIONS

TGC achieved cure rates similar to those of LEV in hospitalized patients with CAP. For patients with risk factors, TGC provided generally favorable clinical outcomes.

Emergency management of community-acquired bacterial pneumonia: what is new since the 2007 Infectious Diseases Society of America/American Thoracic Society guidelines

Community-acquired pneumonia (CAP) is a major health problem in the United States and is associated with substantial morbidity, mortality, and health care costs. Patients with CAP commonly present to emergency departments where physicians must make critical decisions regarding diagnosis and management of pneumonia in a timely fashion, with emphasis on efficient and cost-effective diagnostic choices, consideration of emerging antimicrobial resistance, timely initiation of antibiotics, and appropriate site-of-care decisions. In light of the burden that pneumonia places on health care systems and the emergency department in particular, this article reviews significant developments in the management of CAP in the United States 5 years since the publication of the 2007 Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of CAP in adults, focusing on recent studies and recommendations for managing CAP, the primary bacterial pathogens responsible for CAP, and trends in resistance, new diagnostic technologies, and newer antimicrobials approved for the treatment of CAP. These new data and additional guidelines pertaining to the treatment of CAP further our knowledge and understanding of this challenging infection. Furthermore, appreciation of the availability of new diagnostic testing and therapeutic options will help meet the demand for improved management of CAP.

Clinical and bacteriological efficacies of sitafloxacin against community-acquired pneumonia caused by Streptococcus pneumoniae: nested cohort within a multicenter clinical trial

We evaluated the clinical and bacteriological efficacy of oral sitafloxacin (STFX) in clinically diagnosed community-acquired pneumonia (CAP) caused by Streptococcus pneumoniae. Additionally, we cultured these patient samples to test the minimal inhibitory concentrations (MICs) of levofloxacin (LVFX), moxifloxacin (MFLX), STFX, and penicillin G (PCG), as well as identified mutations in the quinolone resistance determinant regions (QRDRs) in LVFX-resistant strains. This study is a nested cohort from a prospective, multicenter clinical trial consisting of 139 patients with community-acquired pneumonia (CAP), from which 72 were included in this study. After diagnosis of CAP caused by S. pneumoniae, STFX (50 mg twice daily, or 100 mg once daily) was orally administered for 7 days. Sixty-five patient sputum samples were then cultured for MIC analysis. In a LVFX-resistant strain that was identified, mutations in the QRDRs of the gyrA, gyrB, parC, and parE genes were examined. Of 72 patients eligible for this study, S. pneumoniae was successfully cultured from the sputum of 65 patients, and only 7 patients were diagnosed by urinary antigen only. Clinical improvement of CAP was obtained in 65 of the 69 clinically evaluable patients (65/69, 94.2 %). Eradication of S. pneumoniae was observed in 62 patients of the 65 bacteriologically evaluable patients (62/65, 95.4 %). Additionally, STFX showed the lowest MIC distribution compared with LVFX, MFLX, and PCG, and no major adverse reactions were observed. STFX treatment in patients with CAP caused by S. pneumoniae was found to be highly effective both clinically (94.2 %) and bacteriologically (95.4 %).

IDSA Clinical Practice Guideline for Acute Bacterial Rhinosinusitis in Children and Adults

Evidence-based guidelines for the diagnosis and initial management of suspected acute bacterial rhinosinusitis in adults and children were prepared by a multidisciplinary expert panel of the Infectious Diseases Society of America comprising clinicians and investigators representing internal medicine, pediatrics, emergency medicine, otolaryngology, public health, epidemiology, and adult and pediatric infectious disease specialties. Recommendations for diagnosis, laboratory investigation, and empiric antimicrobial and adjunctive therapy were developed.

EUCAST expert rules in antimicrobial susceptibility testing

EUCAST expert rules have been developed to assist clinical microbiologists and describe actions to be taken in response to specific antimicrobial susceptibility test results. They include recommendations on reporting, such as inferring susceptibility to other agents from results with one, suppression of results that may be inappropriate, and editing of results from susceptible to intermediate or resistant or from intermediate to resistant on the basis of an inferred resistance mechanism. They are based on current clinical and/or microbiological evidence. EUCAST expert rules also include intrinsic resistance phenotypes and exceptional resistance phenotypes, which have not yet been reported or are very rare. The applicability of EUCAST expert rules depends on the MIC breakpoints used to define the rules. Setting appropriate clinical breakpoints, based on treating patients and not on the detection of resistance mechanisms, may lead to modification of some expert rules in the future.

In vitro pharmacodynamic evaluation of garenoxacin against quinolone-resistant Streptococcus pneumoniae

The bactericidal activity and resistance selectivity of garenoxacin against Streptococcus pneumoniae with mutations in ParC (S79F) or both GyrA (S81F) and ParC (D83Y and K137N) were investigated using in vitro pharmacokinetic models simulating plasma concentrations for a standard clinical regimen [400mg once daily (q.d.)]. The efficacy of garenoxacin was compared with that of levofloxacin (500 mg q.d.) and moxifloxacin (400mg q.d.). Garenoxacin showed excellent bactericidal activity against S. pneumoniae, including quinolone-resistant S. pneumoniae (QRSP), achieving ratios of area under the plasma concentration-time curve over 24h to minimum inhibitory concentration (AUC(0-24)/MIC) ≥ 26.3, without emerging resistant subpopulations. The area above the killing curves was greater and the time to achieve 99.9% killing was shorter for garenoxacin than the corresponding values for levofloxacin and moxifloxacin. No resistant subpopulations and no additional substitution of amino acids in GyrA or ParC emerged following treatment with garenoxacin. On the other hand, in the parC mutant strain, levofloxacin and moxifloxacin treatment caused an increase in the frequency of the resistant population and an additional substitution of amino acids in GyrA (levofloxacin, S81Y/F/C; moxifloxacin, S81Y or E85K). In QRSP with mutations in GyrA and ParC, levofloxacin had no bactericidal activity, whilst the bactericidal activity of moxifloxacin was less than that of garenoxacin; moreover, an additional substitution of amino acids in ParC (S79Y) was noted. In conclusion, garenoxacin corresponding to an oral dose of 400mg showed excellent bactericidal activity against S. pneumoniae, including QRSP, without the emergence of resistant mutants.

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.

The crystal structure of alanine racemase from Streptococcus pneumoniae, a target for structure-based drug design

Background

Streptococcus pneumoniae is a globally important pathogen. The Gram-positive diplococcus is a leading cause of pneumonia, otitis media, bacteremia, and meningitis, and antibiotic resistant strains have become increasingly common over recent years. Alanine racemase is a ubiquitous enzyme among bacteria and provides the essential cell wall precursor, D-alanine. Since it is absent in humans, this enzyme is an attractive target for the development of drugs against S. pneumoniae and other bacterial pathogens.

Results

Here we report the crystal structure of alanine racemase from S. pneumoniae (Alr_SP). Crystals diffracted to a resolution of 2.0 Å and belong to the space group P3₁21 with the unit cell parameters a = b = 119.97 Å, c = 118.10 Å, α = β = 90° and γ = 120°. Structural comparisons show that Alr_SP shares both an overall fold and key active site residues with other bacterial alanine racemases. The active site cavity is similar to other Gram positive alanine racemases, featuring a restricted but conserved entryway.

Conclusions

We have solved the structure of Alr_SP, an essential step towards the development of an accurate pharmacophore model of the enzyme, and an important contribution towards our on-going alanine racemase structure-based drug design project. We have identified three regions on the enzyme that could be targeted for inhibitor design, the active site, the dimer interface, and the active site entryway.

Risk factors and severity scores in hospitalized patients with community-acquired pneumonia: prediction of severity and mortality

Morbidity and mortality in patients with moderate to severe community-acquired pneumonia (CAP) is a global problem, and CAP is a leading cause of death due to infectious diseases. Prompt initiation of expanded-spectrum antimicrobials is essential for the prevention of unnecessary mortality and complications in patients, particularly in the elderly and other at-risk populations, and the treatment decisions made by practitioners have important implications for healthcare systems when hospitalization is required. Empirical antimicrobial treatment and the appropriate management of CAP patients will initially require the proper assessment of severity and patient risk for increased mortality, as well as risk factors for difficult-to-treat bacteria. This review will examine risk factors and scoring systems that may be predictive of moderate to severe CAP, which is often linked to increased risk of mortality. Understanding and recognizing potential risk factors will allow practitioners to proactively identify patients at the highest risk for severe illness or complications, thereby, guiding site-of-care decisions, as well as the choices for empiric antibiotic regimens. The decision to hospitalize a patient with CAP should include not only a clinical perspective and laboratory and radiographic findings, but also at least one objective tool of risk assessment, all in combination with sound clinical judgment.

Efficacy and safety of nemonoxacin versus levofloxacin for community-acquired pneumonia

Nemonoxacin, a novel nonfluorinated quinolone, exhibits potent in vitro and in vivo activities against community-acquired pneumonia (CAP) pathogens, including multidrug-resistant Streptococcus pneumoniae. Patients with mild to moderate CAP (n = 265) were randomized to receive oral nemonoxacin (750 mg or 500 mg) or levofloxacin (500 mg) once daily for 7 days. Clinical responses were determined at the test-of-cure visit in intent-to-treat (ITT), clinical per protocol (PPc), evaluable-ITT, and evaluable-PPc populations. The clinical cure rates for 750 mg nemonoxacin, 500 mg nemonoxacin, and levofloxacin were 89.9%, 87.0%, and 91.1%, respectively, in the evaluable-ITT population; 91.7%, 87.7%, and 90.3%, respectively, in the evaluable-PPc population; 82.6%, 75.3%, and 80.0%, respectively, in the ITT population; and 83.5%, 78.0%, and 82.3%, respectively, in the PPc population. Noninferiority to levofloxacin was demonstrated in both the 750-mg and 500-mg nemonoxacin groups for the evaluable-ITT and evaluable-PPc populations, and also in the 750 mg nemonoxacin group for the ITT and PPc populations. Overall bacteriological success rates were high for all treatment groups in the evaluable-bacteriological ITT population (90.2% in the 750 mg nemonoxacin group, 84.8% in the 500 mg nemonoxacin group, and 92.0% in the levofloxacin group). All three treatments were well tolerated, and no drug-related serious adverse events were observed. Overall, oral nemonoxacin (both 750 mg and 500 mg) administered for 7 days resulted in high clinical and bacteriological success rates in CAP patients. Further, good tolerability and excellent activity against common causative pathogens were demonstrated. Nemonoxacin (750 mg and 500 mg) once daily is as effective and safe as levofloxacin (500 mg) once daily for the treatment of CAP.

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.

Human antimicrobial peptide LL-37 induces MefE/Mel-mediated macrolide resistance in Streptococcus pneumoniae

Macrolide resistance is a major concern in the treatment of Streptococcus pneumoniae. Inducible macrolide resistance in this pneumococcus is mediated by the efflux pump MefE/Mel. We show here that the human antimicrobial peptide LL-37 induces the mefE promoter and confers resistance to erythromycin and LL-37. Such induction may impact the efficacy of host defenses and of macrolide-based treatment of pneumococcal disease.

Trends in antimicrobial susceptibility of Streptococcus pneumoniae in the Tohoku district of Japan: a longitudinal analysis from 1998 to 2007

Streptococcus pneumoniae is a common cause of respiratory tract infections (RTIs). The prevalence of Streptococcus pneumoniae strains with reduced susceptibility to antimicrobial agents has dramatically increased worldwide. Susceptibility to nine antimicrobial agents and serotypes were determined among 1,644 Streptococcus pneumoniae strains isolated from patients with RTIs in the Tohoku district of Japan from October to December every year from 1998 to 2007. The prevalence of penicillin G-nonsusceptible Streptococcus pneumoniae (PNSP) strains increased gradually from 48.5% in 1998, reached a statistical peak in 2004 (65.1%) and then decreased to 51.5% in 2007. Streptococcus pneumoniae strains with each serotype 3, 6, 19 and 23 were constantly detected, and the distribution of these serotypes in PNSP strains did not significantly change during the study period. A trend of Streptococcus pneumoniae strains nonsusceptible to other beta-lactams tested was similar to that of PNSP strains, except for cefditoren, to which the resistance rate was < 20% throughout the analysis period. The prevalence of strains nonsusceptible to erythromycin and minocycline were consistently > 60%. Almost all penicillin G-resistant Streptococcus pneumoniae (PRSP) strains were resistant to both erythromycin and minocycline throughout the analysis period. The prevalence of strains resistant to fluoroquinolones tested were < 3% over the study period. Our longitudinal surveillance demonstrated for the first time that decreased prevalence of both beta-lactam- and multidrug-resistant strains has been occurring since 2004 in a region of Japan. Careful monitoring of antimicrobial susceptibility of Streptococcus pneumoniae should be continued.

Increase in pneumococcus macrolide resistance, United States

During year 6 of the study, the incidence rate rose from ≈30% to 35.3%.

During year 6 (2005–2006) of the Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin surveillance study, 6,747 Streptococcus pneumoniae isolates were collected at 119 centers. The susceptibility of these isolates to macrolides was compared with data from previous years. Macrolide resistance increased significantly in year 6 (35.3%) from the stable rate of ≈30% for the previous 3 years (p<0.0001). Macrolide resistance increased in all regions of the United States and for all patient age groups. Rates were highest in the south and for children 0–2 years of age. Lower-level efflux [mef(A)]–mediated macrolide resistance decreased in prevalence to ≈50%, and highly resistant [erm(B) + mef(A)] strains increased to 25%. Telithromycin and levofloxacin susceptibility rates were >99% and >98%, respectively, irrespective of genotype. Pneumococcal macrolide resistance in the United States showed its first significant increase since 2000. High-level macrolide resistance is also increasing.

Prevalence of erythromycin and clindamycin resistance among clinical isolates of the Streptococcus anginosus group in Germany

Members of the Streptococcus anginosus group (SAG) are frequently involved in pyogenic infections in humans. In the present study, the antimicrobial susceptibility of 141 clinical SAG isolates to six antimicrobial agents was analysed by agar dilution. All isolates were susceptible to penicillin, cefotaxime and vancomycin. However, 12.8 % displayed increased MIC values (0.12 mg l(-1)) for penicillin. Resistance to erythromycin was detected in eight (5.7 %) isolates. Characterization of the erythromycin-resistant isolates with the double-disc diffusion test revealed Macrolide-Lincosamide-Streptogramin(B) and M-type resistance in six and two isolates, respectively. The erythromycin-resistant isolates were further characterized by PCR for the resistance genes ermA, ermB and mefA. Resistance and intermediate resistance to ciprofloxacin were detected in two and six isolates, respectively. Molecular typing by PFGE revealed a high genetic heterogeneity among the SAG isolates and no evidence for a clonal relationship between the erythromycin-resistant isolates. Our data show that resistance to erythromycin, clindamycin and ciprofloxacin has emerged among SAG isolates in Germany. The implications of these findings for susceptibility testing and antimicrobial therapy of SAG infections are discussed.

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.

Dihydropteroate synthase from Streptococcus pneumoniae: structure, ligand recognition and mechanism of sulfonamide resistance

DHPS (dihydropteroate synthase) catalyses an essential step in the biosynthesis of folic acid and is the target for the sulfonamide group of antimicrobial drugs. In the present paper we report two crystal structures of DHPS from the respiratory pathogen Streptococcus pneumoniae: the apoenzyme at 1.8 Å (1 Å=0.1 nm) resolution and a complex with DHPP (6-hydroxymethyl-7,8-dihydropterin monophosphate) at 2.4 Å resolution. The enzyme forms a α/β barrel structure, with a highly conserved binding pocket for recognition of the pterin substrate, DHPPP (6-hydroxymethyl-7,8-dihydropterin pyrophosphate). There is a fixed order of substrate binding: DHPPP binds first, followed by the second substrate, pABA (p-aminobenzoic acid). Binding of PPi also allows the enzyme to recognize pABA or sulfonamide drugs, which act as pABA analogues. Using equilibrium and pre-steady state kinetic fluorescence measurements, we show that the on-rate for DHPPP binding to the enzyme is relatively low (2.6×105 M−1·s−1) and propose that binding of this substrate induces a large scale movement of the second loop in the enzyme structure to participate in the formation of the pABA-binding site. Two mutations which confer resistance to sulfonamide drugs do not affect DHPPP binding, but have a substantial effect on pABA and sulfonamide recognition. The results show that binding of DHPPP and pABA are separate distinguishable events in the reaction cycle, and that mutations which confer resistance to sulfonamide drugs act exclusively on the second step in the binding process.

The epidemic of antibiotic-resistant infections: a call to action for the medical community from the Infectious Diseases Society of America

The ongoing explosion of antibiotic-resistant infections continues to plague global and US health care. Meanwhile, an equally alarming decline has occurred in the research and development of new antibiotics to deal with the threat. In response to this microbial "perfect storm," in 2001, the federal Interagency Task Force on Antimicrobial Resistance released the "Action Plan to Combat Antimicrobial Resistance; Part 1: Domestic" to strengthen the response in the United States. The Infectious Diseases Society of America (IDSA) followed in 2004 with its own report, "Bad Bugs, No Drugs: As Antibiotic Discovery Stagnates, A Public Health Crisis Brews," which proposed incentives to reinvigorate pharmaceutical investment in antibiotic research and development. The IDSA's subsequent lobbying efforts led to the introduction of promising legislation in the 109 th US Congress (January 2005-December 2006). Unfortunately, the legislation was not enacted. During the 110 th Congress, the IDSA has continued to work with congressional leaders on promising legislation to address antibiotic-resistant infection. Nevertheless, despite intensive public relations and lobbying efforts, it remains unclear whether sufficiently robust legislation will be enacted. In the meantime, microbes continue to become more resistant, the antibiotic pipeline continues to diminish, and the majority of the public remains unaware of this critical situation. The result of insufficient federal funding; insufficient surveillance, prevention, and control; insufficient research and development activities; misguided regulation of antibiotics in agriculture and, in particular, for food animals; and insufficient overall coordination of US (and international) efforts could mean a literal return to the preantibiotic era for many types of infections. If we are to address the antimicrobial resistance crisis, a concerted, grassroots effort led by the medical community will be required.

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.

Larval therapy from antiquity to the present day: mechanisms of action, clinical applications and future potential

When modern medicine fails, it is often useful to draw ideas from ancient treatments. The therapeutic use of fly larvae to debride necrotic tissue, also known as larval therapy, maggot debridement therapy or biosurgery, dates back to the beginnings of civilisation. Despite repeatedly falling out of favour largely because of patient intolerance to the treatment, the practice of larval therapy is increasing around the world because of its efficacy, safety and simplicity. Clinical indications for larval treatment are varied, but, in particular, are wounds infected with multidrug-resistant bacteria and the presence of significant co-morbidities precluding surgical intervention. The flies most often used in larval therapy are the facultative calliphorids, with the greenbottle blowfly (Lucilia sericata) being the most widely used species. This review summarises the fascinating and turbulent history of larval therapy from its origin to the present day, including mechanisms of action and evidence for its clinical applications. It also explores future research directions.

Purification and preliminary crystallization of alanine racemase from Streptococcus pneumoniae

Background

Over the past fifteen years, antibiotic resistance in the Gram-positive opportunistic human pathogen Streptococcus pneumoniae has significantly increased. Clinical isolates from patients with community-acquired pneumonia or otitis media often display resistance to two or more antibiotics. Given the need for new therapeutics, we intend to investigate enzymes of cell wall biosynthesis as novel drug targets. Alanine racemase, a ubiquitous enzyme among bacteria and absent in humans, provides the essential cell wall precursor, D-alanine, which forms part of the tetrapeptide crosslinking the peptidoglycan layer.

Results

The alanine racemases gene from S. pneumoniae (alr_SP) was amplified by PCR and cloned and expressed in Escherichia coli. The 367 amino acid, 39854 Da dimeric enzyme was purified to electrophoretic homogeneity and preliminary crystals were obtained. Racemic activity was demonstrated through complementation of an alr auxotroph of E. coli growing on L-alanine. In an alanine racemases photometric assay, specific activities of 87.0 and 84.8 U mg^-1 were determined for the conversion of D- to L-alanine and L- to D-alanine, respectively.

Conclusion

We have isolated and characterized the alanine racemase gene from the opportunistic human pathogen S. pneumoniae. The enzyme shows sufficient homology with other alanine racemases to allow its integration into our ongoing structure-based drug design project.

Garenoxacin activity against isolates form patients hospitalized with community-acquired pneumonia and multidrug-resistant Streptococcus pneumoniae

Community-acquired pneumonia (CAP) continues to cause significant morbidity worldwide, and the principal bacterial pathogens (Streptococcus pneumoniae and Haemophilus influenzae) have acquired numerous resistance mechanisms over the last few decades. CAP treatment guidelines have suggested the use of broader spectrum agents, such as antipneumococcal fluoroquinolones as the therapy for at-risk patient population. In this report, we studied 3087 CAP isolates from the SENTRY Antimicrobial Surveillance Program (1999-2005) worldwide and all respiratory tract infection (RTI) isolate population of pneumococci (14665 strains) grouped by antibiogram patterns against a new des-F(6)-quinolone, garenoxacin. Results indicated that garenoxacin was highly active against CAP isolates of S. pneumoniae (MIC(90), 0.06 microg/mL) and H. influenzae (MIC(90), < or =0.03 microg/mL). This garenoxacin potency was 8- to 32-fold greater than gatifloxacin, levofloxacin, and ciprofloxacin against the pneumococci and >99.9% of strains were inhibited at < or =1 microg/mL (proposed susceptible breakpoint). Garenoxacin MIC values were not affected by resistances among S. pneumoniae strains to penicillin or erythromycin; however, coresistances were high among the beta-lactams (penicillins and cephalosporins), macrolides, tetracyclines, and trimethoprim/sulfamethoxazole. Analysis of S. pneumoniae isolates with various antimicrobial resistance patterns to 6 drug classes demonstrated that garenoxacin was active against >99.9% (MIC, < or =1 microg/mL) of strains, and the most resistant pneumococci (6-drug resistance, 1051 strains or 7.2% of all isolates) were completely susceptible (100.0% at < or =1 microg/mL) to garenoxacin (MIC(90), 0.06 microg/mL). These results illustrate the high activity of garenoxacin against contemporary CAP isolates and especially against multidrug-resistant (MDR) S. pneumoniae that have created therapeutic dilemmas for all RTI presentations. Garenoxacin appears to be a welcome addition to the CAP treatment options, particularly for the emerging MDR pneumococci strains.

The antibiotic resistome: the nexus of chemical and genetic diversity

Over the millennia, microorganisms have evolved evasion strategies to overcome a myriad of chemical and environmental challenges, including antimicrobial drugs. Even before the first clinical use of antibiotics more than 60 years ago, resistant organisms had been isolated. Moreover, the potential problem of the widespread distribution of antibiotic resistant bacteria was recognized by scientists and healthcare specialists from the initial use of these drugs. Why is resistance inevitable and where does it come from? Understanding the molecular diversity that underlies resistance will inform our use of these drugs and guide efforts to develop new efficacious antibiotics.

Antibiotic prescription for patients referred to a specialist breast clinic

Hospital referral is indicated as an emergency for breast infections not settling with oral antibiotics. Referrals to a breast clinic over a period of 6 months were assessed for prior antibiotic prescription. A total of 1078 patients were seen during this period. 91 (8%) patients had been prescribed antibiotics, 71% of which had been prescribed for non-infective conditions. Of those patients treated for infection, 42% had the wrong antibiotic prescribed. The final diagnoses for patients inappropriately prescribed antibiotics were chest wall pain in 23% and duct ectasia in 14%. Although the reasons for prescription of antibiotics are mutifactorial, careful examination of the patient will diagnose chest wall pain. Delayed prescribing may be appropriate for some patients.