Pneumonia caused by penicillin-non-susceptible and penicillin-susceptible pneumococci in adults: a case-control study

Deciphering structural variation upon biotinylation of biotin carboxyl carrier protein domain in Streptococcus pneumoniae

Streptococcus pneumoniae is a leading cause of community-acquired pneumonia and is responsible for acute invasive and non-invasive infections. Fight against pneumococcus is currently hampered by insufficient vaccine coverage and rising antimicrobial resistance, making the research necessary on novel drug targets. High-throughput mutagenesis has shown that acetyl-CoA carboxylase (ACC) is an essential enzyme in S. pneumoniae which converts acetyl-CoA to malonyl-CoA, a key step in fatty acid biosynthesis. ACC has four subunits; Biotin carboxyl carrier protein (BCCP), Biotin carboxylase (BC), Carboxyl transferase subunit α and β. Biotinylation of S. pneumoniae BCCP (SpBCCP) is required for the activation of ACC complex. In this study, we have biophysically characterized the apo- and holo- biotinylating domain SpBCCP80. We have performed 2D and 3D NMR experiments to analyze the changes in amino acid residues upon biotinylation of SpBCCP80. Further, we used NMR backbone chemical shift assignment data for bioinformatical analyses to determine the secondary and tertiary structure of proteins. We observed major changes in AMKVM motif and thumb region of SpBCCP80 upon biotinylation. Overall, this work provides structural insight into the apo- to holo- conversion of SpBCCP80 which can be further used as a drug target against S. pneumoniae.

Serotype Distribution, Antimicrobial Susceptibility, Multilocus Sequencing Type and Virulence of Invasive Streptococcus pneumoniae in China: A Six-Year Multicenter Study

Background:Streptococcus pneumoniae is an important human pathogen that can cause severe invasive pneumococcal diseases (IPDs). The aim of this multicenter study was to investigate the serotype and sequence type (ST) distribution, antimicrobial susceptibility, and virulence of S. pneumoniae strains causing IPD in China.

Methods: A total of 300 invasive S. pneumoniae isolates were included in this study. The serotype, ST, and antimicrobial susceptibility of the strains, were determined by the Quellung reaction, multi-locus sequence typing (MLST) and broth microdilution method, respectively. The virulence level of the strains in the most prevalent serotypes was evaluated by a mouse sepsis model, and the expression level of well-known virulence genes was measured by RT-PCR.

Results: The most common serotypes in this study were 23F, 19A, 19F, 3, and 14. The serotype coverages of PCV7, PCV10, PCV13, and PPV23 vaccines on the strain collection were 42.3, 45.3, 73.3 and 79.3%, respectively. The most common STs were ST320, ST81, ST271, ST876, and ST3173. All strains were susceptible to ertapenem, levofloxacin, moxifloxacin, linezolid, and vancomycin, but a very high proportion (>95%) was resistant to macrolides and clindamycin. Based on the oral, meningitis and non-meningitis breakpoints, penicillin non-susceptible Streptococcus pneumoniae (PNSP) accounted for 67.7, 67.7 and 4.3% of the isolates, respectively. Serotype 3 strains were characterized by high virulence levels and low antimicrobial-resistance rates, while strains of serotypes 23F, 19F, 19A, and 14, exhibited low virulence and high resistance rates to antibiotics. Capsular polysaccharide and non-capsular virulence factors were collectively responsible for the virulence diversity of S. pneumoniae strains.

Conclusion: Our study provides a comprehensive insight into the epidemiology and virulence diversity of S. pneumoniae strains causing IPD in China.

Clinical relevance of bacterial resistance in lower respiratory tract infection in primary care: secondary analysis of a multicentre European trial

BACKGROUND

The impact of antimicrobial resistance on clinical outcomes in patients with lower respiratory tract infection in primary care is largely unknown.

AIM

To determine the illness course of infections with resistant bacteria in adults presenting to primary care with acute cough.

DESIGN AND SETTING

Secondary analysis of a multicentre European trial in primary care.

METHOD

A total of 2061 adults with acute cough (lasting ≤28 days) were recruited from primary care and randomised to amoxicillin or placebo. To reflect the natural course of disease, only patients in the placebo group (n = 1021) were eligible. Nasopharyngeal flocked swabs and/or sputa (when available) were analysed at baseline and Streptococcus pneumoniae and Haemophilus influenzae isolates underwent susceptibility testing. Patients recorded their symptoms in a diary every day for 4 weeks. Patients with and without resistant bacterial infection were compared with regards to symptom severity, duration of symptoms, worsening of illness, and duration of interference with normal activities or work.

RESULTS

Of the 834 patients with diary records, 104 showed S. pneumoniae and/or H. influenzae infection. Of this number, 54 (52%) were resistant to antibiotics, while seven (7%) were resistant to penicillin. For the duration of symptoms rated 'moderately bad or worse' (hazard ratio 1.27, 95% confidence interval [CI] = 0.67 to 2.44), mean symptom severity (difference -0.48, 95% CI = -1.17 to 0.21), and worsening of illness (odds ratio 0.31, 95% CI = 0.07 to 1.41), there was no statistically significant difference between the antibiotic-resistant and antibiotic-sensitive groups.

CONCLUSION

The illness course of antibiotic-resistant lower respiratory tract infection does not differ from that caused by antibiotic-sensitive bacteria.

Vaccination can drive an increase in frequencies of antibiotic resistance among nonvaccine serotypes of Streptococcus pneumoniae

The bacterial pathogen Streptococcus pneumoniae is a major public health concern, being responsible for more than 1.5 million deaths annually through pneumonia, meningitis, and septicemia. Available vaccines target only a subset of serotypes, so vaccination is often accompanied by a rise in the frequency of nonvaccine serotypes. Epidemiological studies suggest that such a change in serotype frequencies is often coupled with an increase of antibiotic resistance among nonvaccine serotypes. Building on previous multilocus models for bacterial pathogen population structure, we have developed a theoretical framework incorporating variation of serotype and antibiotic resistance to examine how their associations may be affected by vaccination. Using this framework, we find that vaccination can result in a rapid increase in the frequency of preexisting resistant variants of nonvaccine serotypes due to the removal of competition from vaccine serotypes.

Biological and Epidemiological Features of Antibiotic-Resistant Streptococcus pneumoniae in Pre- and Post-Conjugate Vaccine Eras: a United States Perspective

Streptococcus pneumoniae inflicts a huge disease burden as the leading cause of community-acquired pneumonia and meningitis. Soon after mainstream antibiotic usage, multiresistant pneumococcal clones emerged and disseminated worldwide. Resistant clones are generated through adaptation to antibiotic pressures imposed while naturally residing within the human upper respiratory tract. Here, a huge array of related commensal streptococcal strains transfers core genomic and accessory resistance determinants to the highly transformable pneumococcus. β-Lactam resistance is the hallmark of pneumococcal adaptability, requiring multiple independent recombination events that are traceable to nonpneumococcal origins and stably perpetuated in multiresistant clonal complexes. Pneumococcal strains with elevated MICs of β-lactams are most often resistant to additional antibiotics. Basic underlying mechanisms of most pneumococcal resistances have been identified, although new insights that increase our understanding are continually provided. Although all pneumococcal infections can be successfully treated with antibiotics, the available choices are limited for some strains. Invasive pneumococcal disease data compiled during 1998 to 2013 through the population-based Active Bacterial Core surveillance program (U.S. population base of 30,600,000) demonstrate that targeting prevalent capsular serotypes with conjugate vaccines (7-valent and 13-valent vaccines implemented in 2000 and 2010, respectively) is extremely effective in reducing resistant infections. Nonetheless, resistant non-vaccine-serotype clones continue to emerge and expand.

Antimicrobial stewardship program implementation in a medical intensive care unit at a tertiary care hospital in Saudi Arabia

BACKGROUND AND OBJECTIVES

Antimicrobial stewardship programs (ASPs) have shown to prevent the emergence of antimicrobial resistance associated with an inappropriate antimicrobial use. The primary objective of this study was to compare the prescribing appropriateness rate of the empirical antibiotic therapy before and after the ASP implementation in a tertiary care hospital. Secondary objectives include the rate of Clostridium difficile-associated diarrhea (CDAD), physicians' acceptance rate, patient's intensive care unit (ICU) course, total utilization using defined daily dose, and total direct cost of antibiotics.

DESIGN AND SETTINGS

This is a comparative, historically controlled study. Adult medical ICU patients were enrolled in a prospective fashion under the active ASP arm and compared with historical patients who were admitted to the same unit before the ASP implementation. This study was approved by the institutional review board, and the need for informed consent was waived because the interventions and recommendations were evidence based and considered the standard of care. The study was conducted at KFSHRC, Riyadh.

METHODS

Adult medical ICU patients were enrolled under the active ASP arm if they were on any of the 5 targeted antibiotics (piperacillin/tazobactam, imipenem/cilastatin, meropenem, vancomycin, tigecycline), and had no official infectious disease consultation. The interventions were conducted via prospective audit and feedback.

RESULTS

A total of 73 subjects were recruited, 49 in historical control and 24 in the active arm. The appropriateness of empirical antibiotics was improved from 30.6% (15/49) in the historical control arm to 100% (24/24) in the proactive ASP arm (P value < .05). For the ASP group, initially 79.1% (19/24) of the antibiotic uses were inappropriate and diminished by ASPs to 0% on the recommendations implementation. A total of 27 interventions were made with an acceptance rate of 96.3%. The rate of CDAD did not differ between the groups. A reduction in antibiotics utilization and direct cost were also noticed in the ASP arm.

CONCLUSION

A proactive ASP is a vital approach in optimizing the appropriate empirical antibiotics utilization in an ICU setting in tertiary care hospitals. This study highlights the importance of such a program and may serve as a foundation for further ASP initiatives particularly in our region.

Antibiotic-resistant bacteria: a challenge for the food industry

Antibiotic-resistant bacteria were first described in the 1940s, but whereas new antibiotics were being discovered at a steady rate, the consequences of this phenomenon were slow to be appreciated. At present, the paucity of new antimicrobials coming into the market has led to the problem of antibiotic resistance fast escalating into a global health crisis. Although the selective pressure exerted by the use of antibiotics (particularly overuse or misuse) has been deemed the major factor in the emergence of bacterial resistance to these antimicrobials, concerns about the role of the food industry have been growing in recent years and have been raised at both national and international levels. The selective pressure exerted by the use of antibiotics (primary production) and biocides (e.g., disinfectants, food and feed preservatives, or decontaminants) is the main driving force behind the selection and spread of antimicrobial resistance throughout the food chain. Genetically modified (GM) crops with antibiotic resistance marker genes, microorganisms added intentionally to the food chain (probiotic or technological) with potentially transferable antimicrobial resistance genes, and food processing technologies used at sub-lethal doses (e.g., alternative non-thermal treatments) are also issues for concern. This paper presents the main trends in antibiotic resistance and antibiotic development in recent decades, as well as their economic and health consequences, current knowledge concerning the generation, dissemination, and mechanisms of antibacterial resistance, progress to date on the possible routes for emergence of resistance throughout the food chain and the role of foods as a vehicle for antibiotic-resistant bacteria. The main approaches to prevention and control of the development, selection, and spread of antibacterial resistance in the food industry are also addressed.

Impact of a multipronged education strategy on antibiotic prescribing in Quebec, Canada

BACKGROUND

Antibiotic overuse and resistance have become a major threat in the last 2 decades. Many programs tried to optimize antibiotic consumption in the inpatient setting, but the outpatient environment that represents the bulk of antibiotic use has been challenging. Following a significant rise of Clostridium difficile infections, all the health care stakeholders in the province of Quebec, Canada initiated a global education program targeting physicians and pharmacists.

METHODS

A bundle approach was used; 11 user-friendly guidelines were produced by a group of experts and sent to all physicians and pharmacists in Quebec in January 2005. Downloadable versions of guidelines were posted on a dedicated Web site. They were promoted by professional organizations, universities, and experts during educational events, and there was strong acceptance by the pharmaceutical industry with a willingness to follow the recommendations in their marketing. The Intercontinental Medical Statistics (IMS) database was used to analyze and compare Quebec's total outpatient prescriptions per 1000 inhabitants with those in the other Canadian provinces for 2 time periods: preintervention (January 2003 to December 2004), and postintervention (February 2005 to December 2007).

RESULTS

In 2004, antibiotic consumption per capita was 23.3% higher in Canada generally than in Quebec. After the guidelines dissemination, the gap between Quebec and the other Canadian provinces increased by 4.1 prescriptions/1000 inhabitants (P = .0002), and the trend persisted 36 months later. Antibiotic costs fell $134.5/1000 inhabitants in Quebec compared with the rest of Canada (P = .054).

CONCLUSIONS

The implementation of guidelines significantly reduced antibiotic prescriptions in Quebec compared with the rest of the country, and there was a strong trend toward significant cost reduction.

Molecular characterization of invasive penicillin non-susceptible Streptococcus pneumoniae from Denmark, 2001 to 2005

The aim of this study was to characterize invasive penicillin non-susceptible pneumococci (PNSP) isolated in Denmark from 2001 to 2005, describe the genetic changes in the penicillin-binding proteins (PBPs) and compare the isolates to the international recognized PNSP clones. All isolates were characterized using serotyping; 43 isolates were also characterized by multilocus sequence typing (MLST) and sequence determination of the PBP genes, pbp1a, pbp2b and pbp2x. In addition, isolates were tested for susceptibility to various antimicrobial agents. From 2001 to 2005, 178 invasive PNSP isolates were found among all invasive isolates. Of these, 13% were penicillin-resistant pneumococci (PRP). The PRP isolates were different to the penicillin intermediate-resistant pneumococci (PIRP) as they were co-resistant to a higher number of antimicrobial agents, and the serotype diversity was lower for the PRP isolates compared to the PIRP isolates. Changes in the PBPs were found to be the same as those observed in other studies. Most PRP isolates were found to belong to the clonal complex CC156 of which most were ST156 serotype 9V or 14. ST156 is a well known multiresistant widespread international PMEN (Pneumococcal Molecular Epidemiology Network) clone, Spain(9V)-3, which is also present as one of the dominant clones in our neighbour countries of Sweden, Norway and Germany.

Economic evaluation of universal infant vaccination with 7vPCV in Hong Kong

OBJECTIVES

The purpose of this study was to evaluate the clinical and economic benefits of routine infant vaccination with seven-valent pneumococcal conjugate vaccine (7vPCV) in Hong Kong.

METHODS

A decision-analytic model was populated with local age-specific incidence data to simulate the expected health outcomes resulting from 7vPCV vaccination of a birth cohort of 57,100 children compared with an unvaccinated cohort over a 10-year horizon. Primary analyses were conducted from a payer perspective, using local inpatient and outpatient costs associated with the treatment of pneumococcal disease. Vaccine efficacy rates were consistent with results from pivotal clinical trials. The reduction in adult invasive pneumococcal disease (IPD) and associated cost avoidance due to the indirect effect of vaccination were estimated in line with published overseas rates.

RESULTS

Universal 7vPCV vaccination was estimated to prevent 524 cases of IPD and more than 2580 cases of otitis media in the birth cohort over a 10-year period, leading to a reduction of HK$28.7 million (US$3.7 million) in direct medical costs. Additional cost savings from the indirect prevention of 919 adult cases of IPD during this time period also resulted. Overall, 7vPCV vaccination was estimated to have an incremental cost per life-year gained of HK$50,456 (US$6460) from a payer perspective or HK$46,308 (US$5929) when both direct and indirect costs were included.

CONCLUSION

With reference to the World Health Organization's threshold for cost-effectiveness, results from this study indicate that routine infant vaccination with 7vPCV is a cost-effective intervention because of the added cost savings resulting from the indirect effect of vaccination on adult disease.

The additional costs of antibiotics and re-consultations for antibiotic-resistant Escherichia coli urinary tract infections managed in general practice

The emergence of antibiotic resistance is a major threat to public health. In the UK, most antibiotics are prescribed in general practice but the extra costs to general practice of resistant infections have not previously been well described. We compared the costs of treating patients presenting with resistant Escherichia coli urinary tract infections (UTIs) (resistant to ampicillin, trimethoprim or at least one antibiotic) with the costs of treating patients with UTIs that were sensitive to all six tested antibiotics (ampicillin, trimethoprim, amoxicillin/clavulanic acid, cefalexin, ciprofloxacin and nitrofurantoin) with regard to re-consultations and antibiotics prescribed. There were significantly higher antibiotic costs (mean extra antibiotic cost 1.19 pounds/1.75 euros), re-consultation costs ( 2.42 pounds/3.55 euros) and total costs ( 3.62 pounds/5.31euros) for patients whose infections were resistant to at least one antibiotic compared with those with sensitive infections even after accounting for potentially confounding factors. Although these per-patient costs may appear small, they do not take into account the full additional costs of resistant UTIs in the community and, given the high prevalence of UTIs, the overall costs to the health service are substantial.

Resource utilization of adults admitted to a large urban hospital with community-acquired pneumonia caused by Streptococcus pneumoniae

OBJECTIVE

To determine if penicillin-nonsusceptible Streptococcus pneumoniae, among other variables, was significantly associated with greater hospital costs among patients with community-acquired pneumonia (CAP).

DESIGN

Retrospective, cohort study.

SETTING

Eight hundred ten-bed, urban, private, teaching hospital.

PATIENTS

Adult patients admitted between 1999 and 2003 with CAP caused by S pneumoniae.

INTERVENTION

Clinical criteria and costs (inflated to 2004 dollars) were collected from the medical charts and detailed hospital bills for each individual patient. Costs were compared according to classification by penicillin susceptibility. Multivariate linear regression was utilized to determine variables independently associated with increased hospital costs and length of stay.

RESULTS

Of 168 patients included, 44 patients (26%) had CAP caused by penicillin-nonsusceptible S pneumoniae. Median total hospital costs were 8,654 dollars (25th to 75th percentile, 5,457 dollars to 16,027 dollars), with no difference between susceptible and nonsusceptible groups. Bed costs accounted for 55.6% of total costs, followed by laboratory (9.9%) and pharmacy (9.8%) costs. Regression analyses determined that ICU admission (p < 0.001), unexplained delays in discharge (p = 0.001), and neoplasm (p < 0.04) were independently predictive of both total hospital costs (adjusted r2 = 0.46) and increasing length of stay (adjusted r2 = 0.30). Hospital mortality, bacteremia, and congestive heart failure were also associated with at least one of the dependent variables.

CONCLUSION

In the current era in which more potent antibiotics are empirically utilized to treat CAP, it does not appear that a simple classification of penicillin nonsusceptibility complicates the economic impact of S pneumoniae infection. Focused efforts to reduce length of stay, including minimizing prolonged and unnecessary observation of patients, should have the most profound effect on reducing total costs.

Economic consequences of antimicrobial resistance

BACKGROUND

In the past two decades, a dramatic increase in the frequency and prevalence of antimicrobial-resistant pathogens has challenged clinicians and researchers.

MATERIALS AND METHODS

A review of the literature was conducted. Available data identifying the costs and consequences of resistance are summarized while the issues and limitations of research assessing the economics of resistance are acknowledged.

RESULTS

Microbial resistance is a complex, multifactorial phenomenon, but the single most powerful influence is antimicrobial use. Treatment guidelines, clinical pathways, and other directives exert widespread influences on individual selection of antimicrobial agents. However, use of an empiric regimen that does not provide effective coverage, or a targeted regimen that is dosed too low to provide optimal therapy, will delay eradication of the pathogen, increase the potential for resistance to emerge, extend and increase morbidity, and expose the patient to an increased risk of mortality. Coincident with these untoward clinical events are economic consequences secondary to increased duration of treatment, and for some, an extended duration of hospitalization.

CONCLUSION

Resistant gram-negative and gram-positive bacteria have been associated with increased direct medical costs ranging from several thousand dollars to tens of thousands of dollars per patient.

Optimal management of community-acquired acute bacterial rhinosinusitis: the allergist's perspective

OBJECTIVES

To characterize the antibiotic resistance seen in community-acquired respiratory tract infections (RTIs) and determine which characteristics to look for in an antibiotic to improve clinical outcomes and decrease the potential for development of resistance.

DATA SOURCES

Using MEDLINE, we performed a search of articles published from 1966 to 2004 to evaluate the current literature on the subject of antibiotic resistance and strategies to overcome it. Additional cited references, such as abstracts, were also identified.

STUDY SELECTION

Relevant original research articles, reviews, and published abstracts were selected for inclusion in this review.

RESULTS

Several factors were identified that should be considered when choosing empiric antibiotic therapy for community-acquired RTIs with the goal of improving clinical outcomes while minimizing the risk of resistance. These factors include spectrum of activity, bactericidal vs bacteriostatic activity, chemical structure, elimination half-life, and potency.

CONCLUSIONS

The results of these studies support the use of targeted antibiotic agents that, based on structural and chemical properties, are optimized to have a low potential to induce resistance. This approach to antimicrobial therapy appears to be the most suitable for patients with acute bacterial rhinosinusitis and other community-acquired RTIs.

Population antibiotic susceptibility for Streptococcus pneumoniae and treatment outcomes in common respiratory tract infections

PURPOSE

Antibiotic-resistant Streptococcus pneumoniae potentially threatens the successful treatment of common respiratory tract infections (RTIs); however, the relationship between antibiotic resistance and treatment outcomes remains unclear. We aimed to test the hypothesis that higher in vitro penicillin and erythromycin nonsusceptibility levels among clinical isolates of S. pneumoniae are associated with higher risk of treatment failure in suppurative acute otitis media (AOM), acute sinusitis, and acute exacerbation of chronic bronchitis (AECB).

METHODS

We conducted a population-level analysis using treatment outcomes data from a national, managed-care claims database, and antibiotic susceptibility data from a national repository of antimicrobial susceptibility results between 1997 and 2000. Treatment outcomes in patients with suppurative AOM, acute sinusitis, or AECB receiving selected macrolides or beta-lactams were assessed. Associations between RTI-specific treatment outcomes and antibiotic nonsusceptibility were determined using Spearman correlation coefficients with condition-specific paired outcome and susceptibility data for each region and each year.

RESULTS

There were 649 552 available RTI outcomes and 7252 susceptibility tests performed on S. pneumoniae isolates. There were no statistically significant trends across time for resolution proportions following treatment by either beta-lactams or macrolides among any of the RTIs. Correlation analyses found no statistically significant association between S. pneumoniae susceptibility and RTI treatment outcomes apart from a significant positive association between of erythromycin nonsusceptibility in ear isolates and macrolide treatment resolution for suppurative AOM.

CONCLUSION

On the population level, in vitro S. pneumoniae nonsusceptibility to macrolide or beta-lactam antibiotics was not associated with treatment failure in conditions of probable S. pneumoniae etiology.

Neumonías comunitarias graves del adulto

Las neumonías agudas comunitarias son causa frecuente de hospitalización y mortalidad. El reconocimiento inmediato de las formas graves según criterios simples, clínicos, radiológicos y de laboratorio, es una etapa esencial para un tratamiento rápido en el servicio de reanimación con el fin de controlar los fallos orgánicos. La obtención de muestras apropiadas para realizar estudios microbiológicos precede al tratamiento antibiótico, que se debe instaurar con rapidez después de diagnosticar la neumonía. Pese a las técnicas de identificación, sólo la mitad de las neumonías se documentan adecuadamente. El tratamiento antibiótico, en principio empírico, integra los gérmenes patógenos, tanto extracelulares como intracelulares, que producen neumonías con mayor frecuencia; siempre debe ser activo contra el neumococo, la bacteria implicada más a menudo. La asociación de un betalactámico y un macrólido o una fluoroquinolona es la que mejor responde a este objetivo. En las recomendaciones más comunes, las fluoroquinolonas activas contra los neumococos sustituyen a los fármacos precedentes. En el caso excepcional de los pacientes con factores de riesgo especiales, el tratamiento empírico debe tener en cuenta Pseudomonas aeruginosa. La gravedad de parte de las neumonías comunitarias justifica el que se recurra a tratamientos complementarios. Se debe evaluar de nuevo el tratamiento antibiótico en las 72 horas siguientes a su instauración, a fin de valorar su eficacia, adaptar el tratamiento en caso necesario y simplificarlo. El mantenimiento de antibióticos de amplio espectro expone al paciente a efectos secundarios y contribuye a producir resistencias bacterianas. En cuanto a las neumonías neumocócicas, las fluoroquinolonas activas contra el neumococo podrían representar una alternativa en caso de que el neumococo desarrolle resistencia a los betalactámicos. La mortalidad persistente de las neumonías sigue siendo notable. Esto debe fomentar la mejora del tratamiento inicial y la búsqueda de nuevas opciones terapéuticas.

Clinical implications and treatment of multiresistant Streptococcus pneumoniae pneumonia

Streptococcus pneumoniae is the leading bacterial cause of community-acquired respiratory tract infections. Prior to the 1970s this pathogen was uniformly susceptible to penicillin and most other antimicrobials. However, since the 1990s there has been a significant increase in drug-resistant Streptococcus pneumoniae (DRSP) due, in large part, to increased use of antimicrobials. The clinical significance of this resistance is not definitely established, but appears to be most relevant to specific MICs for specific antimicrobials. Certain beta-lactams (amoxicillin, cefotaxime, ceftriaxone), the respiratory fluoroquinolones, and telithromycin are among several agents that remain effective against DRSP. Continued surveillance studies, appropriate antimicrobial usage campaigns, stratification of patients based on known risk factors for resistance, and vaccination programmes are needed to appropriately manage DRSP and limit its spread.

Susceptibility of Streptococcus pneumoniae to penicillin, azithromycin and telithromycin (PROTEKT 1999–2003)

Isolates of Streptococcus pneumoniae collected over the first 4 years of the PROTEKT study were tested for susceptibility to penicillin, azithromycin and telithromycin. A total of 20,750 isolates were collected from 39 countries. Penicillin non-susceptibility rates were stable over the study period; overall, 21.8% of isolates were resistant. Azithromycin resistance increased from 31.0% in Year 1 to 36.3% in Year 4. Resistance rates for penicillin and azithromycin varied between countries and were highest in France, Spain, South Africa, USA and the Far East. Multidrug resistance in S. pneumoniae did not change significantly over the 4 years, with an overall rate of 38.6%. Telithromycin retained good activity against S. pneumoniae (0.1% of isolates resistant), including multidrug-resistant isolates.

Community-acquired bacteraemic pneumococcal pneumonia in adults: effect of diminished penicillin susceptibility on clinical outcome

Pneumococcal pneumonia remains a common disease with a high mortality rate. Between 1995 and 2000, we prospectively analyzed 95 consecutive adult cases of community-acquired bacteraemic pneumococcal pneumonia treated in a single centre. The incidence of pneumococcal resistance to penicillin increased from 19 to 50% during the study period. Multivariate analysis showed that only age and recent hospitalization were independently associated with fatal outcome. The proportion of penicillin-resistant strains was slightly but not significantly higher among patients who died before the fourth hospital day than among those who died later. Patients who died before D4 were more likely to have a recent history of hospitalization, cancer and/or chemotherapy. It thus appears that infection by a resistant pneumococcal strain is not in itself a gravity factor in this setting, but that their acquisition is associated with pejorative clinical features.

Pneumonies communautaires graves de l'adulte

Les pneumonies aiguës communautaires sont des causes fréquentes d'hospitalisation et de mortalité. La reconnaissance immédiate des formes sévères sur des critères simples, cliniques, radiologiques et biologiques, est une étape importante pour une prise en charge rapide en réanimation afin de contrôler les défaillances d'organes. Les prélèvements appropriés microbiologiques précèdent l'antibiothérapie qui doit être instituée très rapidement après le diagnostic de pneumonie. Malgré les techniques d'identification, la moitié seulement des pneumonies sont documentées. Cette antibiothérapie, initialement probabiliste, intègre les germes pathogènes les plus souvent responsables, extra- et intracellulaires ; elle doit toujours être active sur le pneumocoque, bactérie la plus fréquente. L'association d'une β-lactamine et d'un macrolide ou d'une fluoroquinolone répond le mieux à cet objectif. Les fluoroquinolones actives sur le pneumocoque se sont substituées aux précédentes dans les plus récentes recommandations. Dans le cas exceptionnel des patients ayant des facteurs de risque particuliers, le traitement probabiliste doit prendre en compte Pseudomonas aeruginosa. La gravité d'une partie des pneumonies communautaires justifie le recours à des traitements adjuvants. L'antibiothérapie doit être réévaluée dans les 72 heures dans le but d'apprécier son efficacité, de l'adapter éventuellement et de la simplifier. La poursuite des antibiotiques à large spectre expose le patient à des effets indésirables et contribue aux résistances bactériennes. Pour les pneumonies dues au pneumocoque, les fluoroquinolones actives sur le pneumocoque pourront constituer une alternative en cas d'évolution importante des résistances du pneumocoque aux β-lactamines. La mortalité persistante des pneumonies reste sévère. Ceci doit stimuler l'amélioration de la prise en charge initiale et faire rechercher de nouvelles thérapeutiques.

Clinical and Economic Analysis of Methicillin-Susceptible and -Resistant Staphylococcus aureus Infections

BACKGROUND:

The rate of methicillin-resistant Staphylococcus aureus (MRSA) has increased significantly over the last decade. Previous cohort studies of patients with MRSA bacteremia have reported higher mortality rates, increased morbidity, longer hospital length of stay (LOS), and higher costs compared with patients with methicillin-susceptible S. aureus (MSSA) bacteremia. The clinical and economic impact of MRSA involving other sites of infection has not been well characterized.

OBJECTIVE:

To determine the clinical and economic implications of MRSA compared with MSSA infections across a variety of infection sites and severity of illnesses.

METHODS:

A retrospective, case—control analysis comparing differences in clinical and economic outcomes of patients with MRSA and MSSA infections was conducted at an academic medical center. Case patients with MRSA infection were matched (1:1 ratio) to control patients with MSSA infection according to age, site of infection, and type of care.

RESULTS:

Thirty-six matched pairs of patients with S. aureus infection were identified. Baseline characteristics of patients with MSSA and MRSA infection were similar. Patients with MRSA infections had a trend toward longer hospital LOS (15.5 vs 11 days; p = 0.05) and longer antibiotic-related LOS (10 vs 7 days; p = 0.003). Median hospital cost associated with treatment of patients with MRSA infections was higher compared with patients with MSSA infections ($16 575 vs $12 862; p = 0.11); however, this difference was not statistically significant. Treatment failure was common in patients with MRSA infection. Among patients with MSSA infections, treatment failure was associated with vancomycin use.

CONCLUSIONS:

Patients with MRSA infections had worse clinical and economic outcomes compared with patients with MSSA infections.

Reference group choice and antibiotic resistance outcomes

Two types of cohort studies examining patients infected with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) were contrasted, using different reference groups. Cases were compared to uninfected patients and patients infected with the corresponding, susceptible organism. VRE and MRSA were associated with adverse outcomes. The effect was greater when uninfected control patients were used.

Streptococcus pneumoniae and community-acquired pneumonia: a cause for concern

Community-acquired pneumonia (CAP) is the sixth most common cause of death in the United States and the leading cause of death from infectious diseases. It is associated with significant morbidity and mortality, and poses a major economic burden to the healthcare system. Streptococcus pneumoniae is the leading cause of CAP. Other common bacterial causes include Haemophilus influenzae as well as atypical bacteria (Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella species). Increasing resistance to a variety of antimicrobial agents has been documented in S. pneumoniae and is common in H. influenzae as well. Successful empiric therapy is paramount to the management of CAP to avoid treatment failure and subsequent associated costs. Given that resistance is increasing among respiratory pathogens, and S. pneumoniae is the most common etiologic agent identified in CAP, strategies for antimicrobial therapy should be based on the likely causative pathogen, the presence of risk factors for infection with resistant bacteria, and local resistance patterns.

Economic aspects of pneumococcal pneumonia: a review of the literature

In this review, the economic aspects of pneumococcal pneumonia are analysed, including the costs, cost effectiveness and cost benefit of treatment and prevention. We identified eight cost-of-illness studies, 15 analyses comparing the costs of different treatment options and 15 economic evaluations of prevention that met our search criteria. The studies were conducted largely in Europe and the US. Most pertained to community-acquired pneumonia (CAP) in general, without specific analysis of pneumococcus-related illness. Many of the studies were considered to be of poor quality for the following reasons: comparison without randomisation or control variables, disregard of health outcomes, small sample size, restriction of costs to drug costs and vague or disputable sources of cost information. In the US, hospitalisation costs resulting from CAP can be estimated to be between US 7,000 dollars and US 8,000 dollars per admission or US 4 million dollars per 100,000 population. Hospitalisation costs are significant (representing about 90% of total costs), but are much lower in Europe than in the US (one-third to one-ninth of the US estimates in the UK and Spain, respectively). In general, economic studies of treatment for pneumococcal pneumonia are in line with clinical evidence. A drug with proven clinical effectiveness would also appear to be supported from an economic stand point. Furthermore, economic data support an early switch from an intravenous to an oral antibacterial, the use of quinolones for inpatients with CAP, and also the use of guidelines built on clinical evidence. Of all the possible preventive strategies for pneumococcal pneumonia, only vaccination has been subjected to economic evaluation. Pneumococcal polysaccharide vaccine seems relatively cost effective (and potentially cost saving) for those between 65 and 75 years of age, for military recruits and for HIV positive patients with a sufficiently high CD4 cell count. Evaluations of the pneumococcal conjugate vaccine (PCV) indicate the price of the vaccine to be the main determinant of cost effectiveness. As the current price is high (in the order of US 50 dollars per dose), the economic attractiveness of the universal PCV vaccination strategies hinges on the potential for price reductions and the willingness of decision makers to adopt a societal perspective.

Appropriate antimicrobial treatment in nosocomial infections—the clinical challenges

Resistance to antimicrobial agents is emerging in a wide variety of pathogens, particularly those that cause nosocomial infections. As a consequence of this increasing resistance, morbidity and mortality in nosocomial infections is also increasing. It is therefore critical to treat nosocomial infections appropriately by starting antimicrobial treatment early in the course of infection, using the correct agent, at the most appropriate dose, and for an adequate duration. Indeed, early 'appropriate' antibiotic prescribing has been shown significantly to reduce mortality, length of intensive care unit and hospital stay and overall costs. Early use of the correct antibiotic at the appropriate dose and for an adequate duration are key to initial appropriate antibiotic prescribing. Choosing the right antibiotic depends mainly on the likely pathogen(s) and the expected local susceptibility patterns. Selection of appropriate antimicrobial therapy requires a thorough understanding of the likely microbial cause of the infection, including local susceptibility patterns, as well as the properties of the antimicrobials available for treating these infections, namely spectrum of activity and potency (including activity versus known resistance mechanisms), pharmacokinetic profile and tolerability and safety. This review, based on a series of presentations at the 5th International Conference of the Hospital Infection Society (Edinburgh, 2002) examines the importance of appropriate antimicrobial therapy in nosocomial infections, and provides guidance on how to achieve this.

Factors associated with penicillin-nonsusceptible pneumococcal infections in Brazil

Resistance of Streptococcus pneumoniae is a worldwide, growing problem. Studies of factors associated with resistance to penicillin have not been conducted in Brazil. The objective of the present study was to evaluate factors associated with infection by S. pneumoniae not susceptible to penicillin. A prevalence study was conducted including all patients with a positive culture for S. pneumoniae in a hospital from July 1991 to December 1992 and the year 1994. Of 165 patients identified, 139 were considered to have clinically relevant infections and 88% of them had invasive infections. All infections were community acquired and consisted of pneumonia (44%) and of central nervous system (19%), pelvic or abdominal (12%), upper airway or ocular (12%), primary bloodstream (9%) and skin and soft tissue (5%) infections. Mortality was 25%. Susceptibility to penicillin was present in 77.6% of the isolates; 21.8% were relatively resistant, and one isolate was resistant (minimal inhibitory concentration = 4 micro g/ml). Multivariate analysis showed that age below 4 years (odds ratio (OR): 3.53, 95% confidence interval (95%CI): 1.39-8.96) and renal failure (OR: 5.50, 95%CI: 1.07-28.36) were associated with lack of susceptibility to penicillin. Bacteremia occurred significantly less frequently in penicillin-nonsusceptible infections (OR: 0.34, 95%CI: 0.14-0.84), possibly suggesting that lack of penicillin susceptibility is associated with lower virulence in S. pneumoniae.

Selective digestive decontamination should not be routinely employed

There is a general consensus that antimicrobial resistance in the hospital setting has emerged as an important variable influencing patient outcome and resource utilization. Hospitals worldwide are faced with increasingly rapid emergence and spread of antibiotic-resistant bacteria. Both antibiotic-resistant Gram-negative bacilli and Gram-positive bacteria are reported as important causes of hospital-acquired infections. Few antimicrobial agents are available for effective treatment. Selective digestive decontamination (SDD) is a technique aimed at selectively eliminating aerobic Gram-negative bacilli and yeast from the mouth and stomach to reduce the occurrence of hospital-acquired infections, including ventilator-associated pneumonia. Unfortunately, the application of SDD has been associated with emergence of antibiotic-resistant bacterial strains, limiting its overall utility.

Narrow versus broad spectrum antibacterials: factors in the selection of pneumococcal resistance to beta-lactams

Streptococus pneumoniae represents an interesting model to discuss the relative impact of broad versus narrow spectrum antibacterials as potential selectors for resistance. Indeed, this pathogen is responsible for potentially severe infections in the community, and has a great capacity for acquisition of resistance to antibacterial agents. It has been the focus of many studies to elucidate some unique aspects of molecular biology, including the adaptive mechanisms responsible for emergence and spread of multiresistance. In the past, the use of narrow spectrum agents was recommended in order to try to reduce the risk of selection of resistance. This concept is nowadays somewhat obsolete for several reasons. S. pneumoniae is able to acquire resistance to antibacterials belonging to different families of drugs through different molecular mechanisms. Thus, selection of multiresistant pneumococci can result from exposure to very different agents, including narrow spectrum as well as broad spectrum agents. In vitro studies have shown a different potential for selection of resistance among the beta-lactam agents. Furthermore, several studies have more or less directly established a close relationship between the level of antibacterial use and the rate of selection of resistance. In addition to the overall amount of antibacterials prescribed in the community, several other factors have been shown to influence the rate of selection of resistance, including the use of doses that are too low, the length of therapy and the duration of bacterial exposure to long-acting agents compared to drugs with short half-lives. Therefore, there are three main ways to control selection and spread of resistant strains: by (i) reducing the amount of antibacterials used; (ii) using optimal dosages (avoiding underdosing) and treatments of short duration; and (iii) reducing the risk of transmission among young children attending daycare centres or kindergartens. In order to help physicians reduce the number of unnecessary prescriptions, it is important to develop rapid tests to recognise the bacterial origin of a febrile illness and even more important to detect resistance to antibacterials. However, apart from rapid diagnostic tests for streptococcal pharyngitis, those tests are not currently available. As a consequence, currently, the debate around narrow versus broad spectrum antibacterials remains a false debate. Physicians should use broad spectrum agents in many instances of upper or lower respiratory tract infection, taking into consideration the probable pathogens and the risk of (multi)resistance to antibacterials. Once rapid diagnostic are available in community practice, allowing a precise diagnosis of the offending agent and its susceptibility profile, physicians will be able to add to their current criteria the selective potential for resistance of the antibacterials that appear to be active in vitro.

Clinical aspects and cost of invasive Streptococcus pneumoniae infections in children: resistant vs. susceptible strains

Invasive Streptococcus pneumoniae infections in children are associated with serious consequences in terms of morbidity and mortality. The main objective of the study was to determine if invasive infections caused by penicillin-resistant Streptococcus pneumoniae (PRSP) differed in clinical presentation, outcome, risk factors, or cost from those caused by penicillin-susceptible strains (PSSP) in children. All patients aged 18 or less with invasive Streptococcus pneumoniae infections admitted to two teaching hospitals in Montreal between 1989 and 1998 were included in the study. We present a case-control study in which for each index case of PRSP, 3 controls with PSSP infections were matched for age, sex, and site of infection. One hundred and forty-four patients were included in the analysis (36 cases, 108 controls). There was no difference between the two groups in terms of initial clinical presentation (vital signs, laboratory results) or total length of stay. Mortality was 2.7% in both groups. Hospital antibiotic cost was higher in the PRSP group (211 Canadian dollars (CAD) vs. 74 CAD; P=0.02). Antibiotic consumption in the preceding month was significantly associated with PRSP infection. Underlying diseases or day-care attendance were not shown to be significant risk factors for acquiring invasive PRSP infection. There were no differences between invasive infections caused by PRSP and PSSP in terms of clinical presentation, morbidity or mortality in a paediatric population.

Treatment of drug-resistant pneumococcal pneumonia

The increasing prevalence of resistance to penicillin and other drugs among pneumococci has considerably complicated the empirical treatment of community-acquired pneumonia. Penicillin resistance has become widespread and is a worldwide occurrence. Resistance to other classes of antibiotics traditionally used as alternatives in the treatment of pneumococcal infections has also increased markedly during recent years. In some areas of the USA, Europe, and east Asia a prevalence of macrolide resistance as high as 35% or more has been reported recently. From the clinical standpoint, a growing number of failures following the use of these agents has been described. Resistance to fluoroquinolones remains low but several failures have been reported in different parts of the world. Pharmacokinetic/pharmacodynamic parameters have become essential at the time of making a rational choice and calculation of dosage. Penicillin G remains the mainstay of therapy for the treatment of penicillin-susceptible pneumococcal pneumonia. Penicillin-resistant pneumococcal pneumonia (minimum inhibitory concentration <4 microg/mL) can be safely treated with adequate betalactams at the right dosage. The new fluoroquinolones are very active and effective in pneumococcal pneumonia. Caution should be exercised in the widespread prescription of these drugs if we are to limit the rate of resistance to these agents.

Association between antibiotic resistance and community prescribing: a critical review of bias and confounding in published studies

The reported association between antibiotic prescribing and resistance may be subject to bias or confounding. Bias describes any effect at any stage of investigation or inference tending to produce results that depart systematically from the true value. A confounding variable is one that is associated independently with both exposure and outcome. Confounding variables may create an apparent association or mask a real association. Pharmacoepidemiology is the study of the use and the effects of drugs in large numbers of people. We have used standard pharmacoepidemiological methods to investigate sources of bias and confounding in the association between prescribing and resistance. We conclude that the association is statistically valid and that the consistency of evidence supports a cause-effect relationship. Nonetheless, several important sources of bias and confounding must be taken into account in future studies that analyze the impact of prescribing policies on resistance.

Is there a role for antibiotic cycling in the intensive care unit?

Antibiotic resistance of bacterial pathogens has emerged as one of the most important issues facing critical care practitioners. Resistance of many commonly encountered bacterial species is increasing and has been associated with greater administration of inadequate antimicrobial therapy to patients within intensive care units. This has resulted in greater patient morbidity, higher mortality rates, and increased healthcare costs. Methods to reduce antimicrobial resistance have focused on increasing adherence to infection control practices and improving antibiotic utilization. Antibiotic cycling is a strategy to reduce antimicrobial resistance by withdrawing an antibiotic or antibiotic class from use and subsequently reintroducing it at a later point in time. The main goal of cycling is to allow resistance rates for specific antibiotics to decrease, or at least remain stable, when their use is periodically eliminated from the intensive care unit.

Penicillin pharmacodynamics in four experimental pneumococcal infection models

Clinical and animal studies indicate that with optimal dosing, penicillin may still be effective against penicillin-nonsusceptible pneumococci (PNSP). The present study examined whether the same strains of penicillin-susceptible pneumococci (PSP) and PNSP differed in their pharmacodynamic responses to penicillin by using comparable penicillin dosing regimens in four animal models: peritonitis, pneumonia, and thigh infection in mice and tissue cage infection in rabbits. Two multidrug-resistant isolates of Streptococcus pneumoniae type 6B were used, one for which the penicillin MIC was 0.016 microg/ml and the other for which the penicillin MIC was 1.0 microg/ml. Two additional strains of PNSP were studied in the rabbit. The animals were treated with five different penicillin regimens resulting in different maximum concentrations of drugs in serum (C(max)s) and times that the concentrations were greater than the MIC (T(>MIC)s). The endpoints were bacterial viability counts after 6 h of treatment in the mice and 24 h of treatment in the rabbits. Similar pharmacodynamic effects were observed in all models. In the mouse models bactericidal activity depended on the T(>MIC) and to a lesser extent on the Cmax/MIC and the generation time but not on the area under the concentration-time curve (AUC)/MIC. Maximal bactericidal activities were similar for both PSP and PNSP, being the highest in the peritoneum and blood (approximately 6 log10 CFU/ml), followed by the thigh (approximately 3 log10 CFU/thigh), and being the lowest in the lung (approximately 1 log10 CFU/lung). In the rabbit model the maximal effect was approximately 6 log10 CFU/ml after 24 h. In the mouse models bactericidal activity became marked when T(>MIC) was > or =65% of the experimental time and C(max) was > or =15 times the MIC, and in the rabbit model bactericidal activity became marked when T(>MIC) was > or =35%, Cmax was > or =5 times the MIC, and the AUC at 24 h/MIC exceeded 25. By optimization of the Cmax/MIC ratio and T(>MIC), the MIC of penicillin for pneumococci can be used to guide therapy and maximize therapeutic efficacy in nonmeningeal infections caused by PNSP.

Economic impact of antimicrobial resistance

One reason antimicrobial-drug resistance is of concern is its economic impact on physicians, patients, health-care administrators, pharmaceutical producers, and the public. Measurement of cost and economic impact of programs to minimize antimicrobial-drug resistance is imprecise and incomplete. Studies to describe and evaluate the problem will have to employ new methods and be of large scale to produce information that is broadly applicable.

Community-acquired pneumonia in the elderly

Pneumonia in the elderly is a common and serious problem with a clinical presentation that can differ from that in younger patients. Older patients with pneumonia complain of significantly fewer symptoms than do younger patients, and delirium commonly occurs. Indeed, delirium may be the only manifestation of pneumonia in this group of patients. Alcoholism, asthma, immunosuppression, and age >70 years are risk factors for community-acquired pneumonia in the elderly. Among nursing home residents, the following are risk factors for pneumonia: advanced age, male sex, difficulty in swallowing, inability to take oral medications, profound disability, bedridden state, and urinary incontinence. Streptococcus pneumoniae is the most common cause of pneumonia among the elderly. Aspiration pneumonia is underdiagnosed in this group of patients, and tuberculosis always should be considered. In this population an etiologic diagnosis is rarely available when antimicrobial therapy must be instituted. Use of the guidelines for treatment of pneumonia issued by the Infectious Diseases Society of America, with modification for treatment in the nursing home setting, is recommended.

Gemifloxacin: survival of the fittest

The incidence of penicillin resistance in pneumococci is increasing in the USA, having risen from <5% before 1989 to >35% in 1997. There has also been a shift in the ratio of intermediate to high-level resistance from 3 or 4:1 to 2 or 1:1. Multidrug resistance and resistance to macrolides and fluoroquinolones in pneumococci is also a matter of concern. The implications for empirical treatment of respiratory tract infections are considerable. The potential of quinolones with activity against respiratory pathogens including pneumococci must be preserved by careful antimicrobial prescribing.

The influence of inadequate antimicrobial treatment of bloodstream infections on patient outcomes in the ICU setting

STUDY OBJECTIVE

To evaluate the relationship between the adequacy of antimicrobial treatment for bloodstream infections and clinical outcomes among patients requiring ICU admission.

DESIGN

Prospective cohort study.

SETTING

A medical ICU (19 beds) and a surgical ICU (18 beds) from a university-affiliated urban teaching hospital.

PATIENTS

Between July 1997 and July 1999, 492 patients were prospectively evaluated.

INTERVENTION

Prospective patient surveillance and data collection.

RESULTS

One hundred forty-seven patients (29.9%) received inadequate antimicrobial treatment for their bloodstream infections. The hospital mortality rate of patients with a bloodstream infection receiving inadequate antimicrobial treatment (61.9%) was statistically greater than the hospital mortality rate of patients with a bloodstream infection who received adequate antimicrobial treatment (28.4%; relative risk, 2. 18; 95% confidence interval [CI], 1.77 to 2.69; p < 0.001). Multiple logistic regression analysis identified the administration of inadequate antimicrobial treatment as an independent determinant of hospital mortality (adjusted odds ratio [AOR], 6.86; 95% CI, 5.09 to 9.24; p < 0.001). The most commonly identified bloodstream pathogens and their associated rates of inadequate antimicrobial treatment included vancomycin-resistant enterococci (n = 17; 100%), Candida species (n = 41; 95.1%), oxacillin-resistant Staphylococcus aureus (n = 46; 32.6%), coagulase-negative staphylococci (n = 96; 21.9%), and Pseudomonas aeruginosa (n = 22; 10.0%). A statistically significant relationship was found between the rates of inadequate antimicrobial treatment for individual microorganisms and their associated rates of hospital mortality (Spearman correlation coefficient = 0.8287; p = 0.006). Multiple logistic regression analysis also demonstrated that a bloodstream infection attributed to Candida species (AOR, 51.86; 95% CI, 24.57 to 109.49; p < 0.001), prior administration of antibiotics during the same hospitalization (AOR, 2.08; 95% CI, 1.58 to 2.74; p = 0.008), decreasing serum albumin concentrations (1-g/dL decrements) (AOR, 1.37; 95% CI, 1.21 to 1.56; p = 0.014), and increasing central catheter duration (1-day increments) (AOR, 1.03; 95% CI, 1.02 to 1.04; p = 0.008) were independently associated with the administration of inadequate antimicrobial treatment.

CONCLUSIONS

The administration of inadequate antimicrobial treatment to critically ill patients with bloodstream infections is associated with a greater hospital mortality compared with adequate antimicrobial treatment of bloodstream infections. These data suggest that clinical efforts should be aimed at reducing the administration of inadequate antimicrobial treatment to hospitalized patients with bloodstream infections, especially individuals infected with antibiotic-resistant bacteria and Candida species.

Relationship between capsular type, penicillin susceptibility, and virulence of human Streptococcus pneumoniae isolates in mice

We examined the relationship between penicillin susceptibility, peritoneal virulence in Swiss mice, and capsular type in a selection of 122 clinical Streptococcus pneumoniae isolates belonging to 24 serotypes. Regardless of the serotype, all 32 virulent strains were susceptible to penicillin, and all 41 strains with diminished susceptibility or resistance to penicillin were avirulent. The remaining 49 strains were both susceptible to penicillin and avirulent, irrespective of the serotype. On the basis of their capsular type and pathogenic behavior, strains fell into one of four groups. In the group consisting of serotypes 1, 3, and 4 (n = 16), strains were predominantly virulent (81.3%), and all were penicillin susceptible. In the serotype 6 group (n = 32), the frequency of virulence was significantly lower (34.4 versus 81.3%, P = 0.002), and strains were predominantly penicillin susceptible (71.9%). In the group composed of serotypes 9, 14, 19, and 23 (n = 50), all strains were avirulent, and 56% had decreased susceptibility (n = 12) or resistance to (n = 16) penicillin. The fourth group was heterogenous, as it pooled 24 strains of 15 different serotypes; in this group the frequency of virulence was 33.3%, and strains were predominantly penicillin susceptible (83.3%). These data point to a complex relationship between penicillin susceptibility and virulence in mice but do not entirely separate these characteristics from the role of the capsular type. The possibility that the mechanisms conferring penicillin resistance are related to those leading to a loss of virulence is supported by these findings.

A comparative clinical study of pneumonia by penicillin-resistant and -sensitive Streptococcus pneumoniae in a community hospital

OBJECTIVE

This study aimed to determine the clinical difference of pneumonia between penicillin-resistant and penicillin-sensitive Streptococcus pneumoniae.

METHODOLOGY

Forty-nine cases in 46 patients of pneumococcal pneumonia were studied from December 1992 to May 1997. There were 24 cases (in 22 patients) of penicillin-resistant pneumococci (PRSP) pneumonia which were compared with 25 cases (in 24 patients) with penicillin-sensitive pneumococci (PSSP).

RESULTS

Both the mean age and the underlying disease states did not differ between the two groups. However, hospital-acquired pneumonia and previous use of antibiotics were observed in eight (33.3%) and 12 (50.0%) patients in PRSP compared with three (12.0%) and two (8.0%) in PSSP, respectively. The clinical efficacy rate and bacteriological eradication rates were 87.5 and 87.5% in PRSP compared with 87.5 and 87.0% in PSSP, respectively. Minimum inhibitory concentration (MIC) of antibiotics against 30 pneumococcal isolates was examined, and 10 strains ranged from 0.10-0.78 microg/mL and five strains were more than 1.56 microg/mL against penicillin G, while the MIC showed higher resistance to other antibiotics except for the carbapenems. Serotyping of the isolates by antiserum revealed differences in the predominant types PRSP (19F) and PSSP (6A,9V) [corrected].

CONCLUSIONS

We must care for not only community-acquired infection but also nosocomial transmission of PRSP pneumonia. Most patients with infections due to PRSP tended to have a milder illness with a good outcome (no patient died). As such it appears that empiric therapy for pneumococcal pneumonia does not require modification from what is recommended at present. However, in patients with infection due to highly resistant strains, and who are not responding to conventional therapy should have their treatment modified according to subsequent susceptibility testing.

Opinion: the clinical use of selective digestive decontamination

Several recent meta-analyses have shown that the use of SDD can reduce the occurrence of nosocomial pneumonia among ventilated patients in the intensive care unit (ICU) setting. However, the use of SDD has also been demonstrated to increase subsequent patient colonization and infection with antibiotic-resistant bacteria, particularly Gram-positive cocci. Therefore, the routine use of SDD cannot be advocated at the present time. The mortality benefit of SDD appears to occur in surgical/trauma patients, and to be associated primarily with the administration of parenteral antibiotics. This is already an accepted practice in most patients during the perioperative period (eg prophylactic parenteral antibiotics for 24 h). Prolonged decontamination of the aerodigestive tract with topical antimicrobials does not appear to influence outcome, and should not be routinely employed.

Advances in antimicrobial therapy of community-acquired pneumonia

Community-acquired pneumonia has a significant impact upon healthcare in North America and worldwide. In the U.S. it is responsible for three to four million cases yearly and 78,000 deaths. It is not a homogeneous entity and it may be caused by a number of pathogens including Streptococcus pneumoniae, the atypicals (Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella species) Haemophilus influenzae and Gram-negative rods. While it is clear that directed therapy is the ideal, empiric therapy is likely to remain the norm for some time to come. This is because of limitations in current diagnostic techniques, the possibility of infection with co-pathogens and the broad spectrum of antimicrobial activity required to treat the various pathogens which may be responsible for infection in any given patient. Of great concern is the increase in the incidence of resistant pathogens seen in community-acquired pneumonia. Of particular significance are the isolates of S. pneumoniae which display resistance to penicillin and macrolides although the exact clinical relevance has yet to be determined. New guidelines for the treatment of community-acquired pneumonia have been developed by the Infectious Disease Society of America which include the new fluoroquinolones. These agents offer the potential for monotherapy of community-acquired pneumonia in cases which previously required combination regimens such as a macrolide and a beta-lactam. There is great concern however, that these agents not be used inappropriately thereby hastening the emergence of resistance to the fluoroquinolone class of antimicrobials.