Antimicrobial resistance among clinical isolates of Streptococcus pneumoniae in North America

Immunization with polyamine transport protein PotD protects mice against systemic infection with Streptococcus pneumoniae

The human pathogen Streptococcus pneumoniae contains genes for a putative polyamine ABC transporter which are organized in an operon and designated potABCD. Polyamine transport protein D (PotD) is an extracellular protein which binds polyamines and possibly other structurally related molecules. PotD has been shown to contribute to virulence in both a murine sepsis model and a pneumonia model with capsular type 3 pneumococci. The protective efficacy of recombinant PotD was evaluated by active immunization and intravenous challenge with capsular type 3 pneumococci in CBA/N mice. Immunized mice had 91.7% survival following lethal pneumococcal challenge, compared with 100% mortality in the control group. Immunized animals had high-titer anti-PotD antibodies following three immunizations with alum. Protection in a sepsis model was also seen after passive administration of rabbit antiserum raised against PotD (P < 0.004). These results suggest that antibodies to PotD confer protection against invasive pneumococcal disease and that this protein should be studied further as a potential vaccine candidate for protection against invasive pneumococcal infections.

Cost-effectiveness of universal pneumococcal vaccination for infants in Italy

This study aimed at estimating the health and economic outcomes of universal infant vaccination with seven-valent pneumococcal conjugate vaccine (PCV-7) in Italy. A Markov model simulated lifetime evolution of a birth cohort (538,138 children): universal vaccination would avert 769 invasive infections, 18 deaths and 1323 life years. At base-case analysis, universal three-dose vaccination would cost euro 26,449 (95% CI: 1975-62,075) and euro 38,286 (95% CI: 22,164-70,801) per life year-saved in the societal and the NHS perspective, respectively. In the hypothesis of a 5-year long protection period, vaccination would cost euro 32,694 and euro 43,115 per life-year saved. Considering yearly incidence of invasive pneumococcal disease reported for Veneto and Sardinia regions, PCV-7 vaccination would result highly cost-effective determining a cost of euro 10,479 and euro 16,890 per life year-save in the NHS and the societal perspective, respectively.

Widespread use of fluoroquinolones versus emerging resistance in pneumococci

During the past decade, respiratory-tract pathogens have shown an increase in resistance to all classes of antimicrobial agents. Although the increasing prevalence of penicillin-resistant Streptococcus pneumoniae has resulted in an increased reliance on newer classes of agents, such as the fluoroquinolones, the broad use of these agents has contributed to increasing prevalence of strains with in vitro fluoroquinolone resistance, which are associated with treatment failures, nosocomial outbreaks, and patient fatalities. Strategies to limit this emerging dilemma and preserve the clinical utility of these agents are needed.

New potential in pneumococcal immunization. Conjugate vaccine may improve disease protection, health of infants and young children

Since 2000, a new pneumococcal conjugate vaccine has been on the US market, offering immunization against seven serotypes. Its use has the potential to dramatically reduce the incidence of pneumococcal disease and its sequelae in children. Here, the authors review the efficacy, safety, and cost of the new pneumococcal vaccine and offer guidelines on how to incorporate this newer vaccine into today's immunization regimens.

Cephalosporin-resistant pneumococcal pneumonia: does it, affect outcome?

STUDY OBJECTIVES

Penicillin resistance has been reported in various studies to have no impact on the outcome of pneumococcal pneumonia. However, the importance of cephalosporin resistance has not been systematically studied. We conducted an analysis of patients with high-level cephalosporin-resistant Streptococcus pneumoniae pneumonia (H-CRSPP).

DESIGN

Retrospective matched, case-control study.

SETTING

Two inner-city academic hospitals.

PATIENTS

Twenty-six patients with H-CRSPP admitted to the hospital between 1995 and 1999 were identified. Each patient was matched with two controls with cephalosporin-sensitive but oxacillin-resistant pneumococcal pneumonia admitted during the same time period. Matching was done based on pneumonia severity of illness index (PSI) and for other factors.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

We evaluated a number of outcomes including mortality length of stay in the hospital, and time to respond to treatment. Patients with H-CRSPP took longer to respond to treatment (6.5 +/- 0.9 days vs 4.1 +/- 0.7 days, P=0.05) and had a longer length of stay in hospital (15.4 +/- 2.2 days vs 92 +/- 1.6 days, P=0.02). None of the other outcomes were different between the two groups.

CONCLUSIONS

Overall, we have found that the presence of cephalosporin resistance does impact the course of pneumococcal pneumonia.

Resistance among Streptococcus pneumoniae: Implications for drug selection

Streptococcus pneumoniae is an important pathogen in many community-acquired respiratory infections in the United States and a leading cause of morbidity and mortality worldwide. Unfortunately, S. pneumoniae is becoming increasingly resistant to a variety of antibiotics. Results of recent surveillance studies in the United States show that the prevalence of penicillin-nonsusceptible S. pneumoniae ranges from 25% to >50%, and rates of macrolide resistance among pneumococci are reported to be as high as 31%. A high prevalence of resistance to other antimicrobial classes is found among penicillin-resistant strains. Newer quinolones (e.g., gatifloxacin, gemifloxacin, and moxifloxacin) that have better antipneumococcal activity in vitro are the most active agents and therefore are attractive options for treatment of adults with community-acquired respiratory infections. Efforts should be made to prevent pneumococcal infections in high-risk patients through vaccination.

Novel erythromycin derivatives with aryl groups tethered to the C-6 position are potent protein synthesis inhibitors and active against multidrug-resistant respiratory pathogens

A novel series of erythromycin derivatives has been discovered with potent activity against key respiratory pathogens, including those resistant to erythromycin. These compounds are characterized by having an aryl group tethered to the C-6 position of the erythronolide skeleton. Extensive structural modification of the C-6 moiety led to the discovery of several promising compounds with potent activity against both mef- and erm-mediated resistant Streptoccoccus pneumoniae. Preliminary mechanistic studies indicated that the new macrolides are potent protein synthesis inhibitors, which interact with methylated ribosomes isolated from resistant organisms. In experimental animal models, these compounds exhibited excellent in vivo efficacy and balanced pharmacokinetic profiles.

Infections in multiple myeloma

Multiple myeloma is a relatively rare but severe hematologic malignancy. Marked depression in production of normal immunoglobulins, mild neutropenia, and alkylant/steroid therapy or BMT/SCT all produce major suppression of the immune system in the totality of patients. Recurrent bacterial, fungal, and viral infections are an important cause of morbidity and the most common cause of death in these subjects. Prompt diagnosis and appropriate anti-infective chemotherapy are essential in order to reduce the risk of mortality.

Pneumococcal resistance: the treatment challenge

OBJECTIVE

To review in vitro and in vivo information dealing with pneumococcal antibiotic resistance and provide a review of the incidence, mechanisms, and controversies surrounding this growing problem. The review is also intended to provide clinicians with relevant recommendations on treatment and prevention of this organism.

DATA SOURCES AND SELECTION

Primary and review articles were identified by MEDLINE search (1966-August 2000) and through secondary resources such as conference proceedings. All of the articles identified from the data sources were evaluated, and all information deemed relevant was included in this review.

DATA SYNTHESIS

The growing incidence and reporting of pneumococcal isolates that are resistant to one or more classes of antibiotics have become a troubling trend that has resulted in significant shifts in treatment. Although clinicians have shifted to a new generation or class of antibiotics when faced with a resistance trend, data with resistant pneumococci show that this may not be necessary. By incorporating the pharmacokinetic and pharmacodynamic data of antimicrobials into the decision-making process, many of the drugs that we have become hesitant to use due to this resistance may still be appropriate if used correctly.

CONCLUSIONS

Appropriate dosing of antimicrobials, combined with optimal use of pneumococcal vaccines, will not only prolong the longevity of some agents, but also hopefully slow resistance development.

Antimicrobial resistance in the chronically critically ill patient

Infection caused by organisms resistant to conventional antimicrobial therapy is an emerging problem of global proportions. This article describes the epidemiology of infections caused by resistant organisms in chronically critically ill patients and explores factors and mechanisms that lead to the development of resistance. Specific organisms and strategies for the treatment and control of these resistance organisms are discussed.

Quinolone Resistance: Older Concepts and Newer Developments

New quinolone compounds have been recommended for use in the treatment of respiratory tract infections, particularly pneumonia caused by multi drug-resistant Streptococcus pneumoniae. Of concern, however, is the recent emergence of pneumococcal isolates with reduced susceptibilities to both old and new quinolone compounds. This necessitates the employment of quinolone-use strategies aimed at restricting the emergence of resistance, to extend the effectiveness of this very important class of antibacterial agents. This article provides a comprehensive review of the recent discoveries in type II topoisomerase/quinolone structure-function relationships. It also addresses new insights into the mechanisms of quinolone resistance, the predicted trends in quinolone resistance, and possible strategies for quinolone use against S. pneumoniae.

Quinupristin/dalfopristin: a therapeutic review

BACKGROUND

The proliferation of multidrug-resistant gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium (VREF), has created a pressing need for effective alternative antibiotics. Quinupristin/dalfopristin is a new combination streptogramin product with a selective spectrum of antibacterial activity, mainly against gram-positive aerobic bacteria. It has been assessed primarily in emergency-use protocols, in hospitalized patients with skin and skin-structure infections, and in patients with VREF bacteremia.

OBJECTIVES

The objectives of this review were to summarize important results of in vitro microbiologic studies; to provide information on relevant pharmacokinetic parameters, drug interactions, and Y-site compatibility; and to assess efficacy and safety data from clinical studies of quinupristin/dalfopristin.

METHODS

Articles included in this review were identified by a MEDLINE search of the literature published between 1966 and September 2000 using the terms Synercid, quinupristin, and dalfopristin. Additional articles were retrieved from the reference lists of articles identified in the MEDLINE search.

RESULTS

In vitro analysis of the spectrum of activity of quinupristin/dalfopristin has confirmed its relatively selective coverage of gram-positive aerobic bacteria. Both quinupristin and dalfopristin undergo hepatic metabolism and are extensively excreted in the feces. Combination quinupristin/dalfopristin inhibits the cytochrome P450 3A4 pathway, and caution is warranted with concomitant use of other medications eliminated via this pathway. In trials in patients with VREF infections, treatment success with quinupristin/dalfopristin varied depending on the site of infection, ranging from 51.9% in bacteremia of unknown origin to 88.9% in urinary tract infections. The results of comparative clinical trials suggest that quinupristin/dalfopristin has similar efficacy to that of commonly used antibiotics, including cefazolin, oxacillin, and vancomycin, in patients with skin and skin-structure infections or nosocomial pneumonia. The most frequently reported adverse effects with administration of quinupristin/dalfopristin were infusion-site inflammation, pain, and edema; other infusion-site reactions; and thrombophlebitis. Arthralgia, myalgia, nausea, diarrhea, vomiting, and rash occurred in 2.5% to 4.6% of patients and were the most frequently reported systemic adverse events.

CONCLUSIONS

Outcomes data from clinical trials indicate that quinupristin/dalfopristin has the potential to play an important role in the treatment of bacteremia, complicated skin and skin-structure infections, and nosocomial pneumonia caused by VREF. Issues of bacterial resistance to quinupristin/dalfopristin and other appropriate uses of this combination agent remain to be elucidated.

Antibiotic susceptibility and serotype distribution of Streptococcus pneumoniae causing meningitis in Italy, 1997-1999

Because few data are available in Italy regarding antimicrobial susceptibility and serotype distribution of invasive Streptococcus pneumoniae strains, meningeal isolates collected at Italian hospitals during the years 1997-1999 were studied. The 12 most common serogroups, representing > 85% of the isolates, were 14, 23, 6, 4, 3, 9, 19, 8, 1, 12, 18, and 7 (in order of frequency). The serogroups identified in children < 5 years old were more limited in number: 80% are included in the 7-valent conjugate vaccines. Penicillin resistance was observed in 14 (9.5%) of 148 strains and increased from 5% in the first part of the study to 13% in the last part. Only 2 strains were fully penicillin resistant, and these belonged to serotype 9V. Thirty percent of the strains, mostly belonging to serogroups 14 or 6 and carrying either the ermB or the mef genes, were resistant to erythromycin.

Antimicrobial resistance in Streptococcus pneumoniae: implications for patients with community-acquired pneumonia

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. During the past decade, the prevalence of penicillin resistance in S pneumoniae has increased dramatically, with resistance rates approaching 45% in some areas of the United States. Streptococcus pneumoniae has also acquired resistance to other commonly used antimicrobials, including cephalosporins, macrolides, and trimethoprim-sulfamethoxazole. While vancomycin and the newer quinolones are currently highly active against most strains of S pneumoniae, reduced susceptibilities to these agents have been identified in some strains. Prior use of antimicrobial agents is the major risk factor for colonization and infection with antibiotic-resistant strains. beta-Lactam antibiotics remain the treatment of choice for infections caused by susceptible S pneumoniae. The optimum therapy for penicillin-resistant strains remains unclear. Appropriate empirical therapy for patients with community-acquired pneumonia depends in part on the community-specific resistance patterns of S pneumoniae to various antibiotics. In this article, we provide an overview of the development of S pneumoniae resistance to commonly used antibiotics and discuss the implications of the development of resistance on treatment decisions.

Antibiotic resistance

Widespread resistance problems exist today in a global sense because of the incorporation of antibiotics with a high resistance potential into animal feeds and because of the uncontrolled use of antibiotics with a high resistance potential in the clinical setting. The only proven method of controlling nonoutbreak resistance problems in hospitals is to limit the hospital formulary to antibiotics with little or no resistance potential. The control of multiresistant organisms in outbreaks occurring in hospitals is best contained using appropriate infection control containment measures. Physicians treating infections in the community, with all other factors being equal, should preferentially select antibiotics with a low resistance potential. The titles and headings of much of the resistance literature are misleading. Articles should not contain fluoroquinolone resistant in the title when ciprofloxacin-resistant organisms are described. Many articles concerning penicillin-resistant pneumococci are entitled fluoroquinolone-resistant S. pneumoniae. These articles describe ciprofloxacin-resistant S. pneumoniae and not resistance to other fluoroquinolones. The same error is perpetuated in describing third-generation cephalosporins and carbapenems. Virtually all of the resistance problems associated with third-generation cephalosporins and carbapenems are due to ceftazidime or imipenem. More precise titling in the literature would remind physicians that antibiotic resistance is related to a specific agent and not class phenomena.

Impact of Antimicrobial Resistance on the Treatment of Invasive Pneumococcal Infections

Infectious diseases, such as pneumococcal pneumonia, which were almost invariably lethal in the pre-antibiotic era, caused radically less mortality with the advent of antimicrobial chemotherapy. However, the use, misuse, and abuse of these agents have led to the emergence of antimicrobial resistance. In the past, pneumococci were all exquisitely sensitive to penicillin G. By the late 1960s, penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) was being described. Since then, this problem has achieved epidemic proportions in many areas of the world, including the United States. Many experts no longer consider penicillin an acceptable therapy for patients suspected of having invasive pneumococcal disease, especially if the central nervous system (CNS) is involved. Recommendations for therapy are based on theoretical concerns, in vitro susceptibility testing, animal data, and a few, scattered reports of penicillin failure in patients with invasive disease.

Gram-Positive Pneumonia

Gram-positive pneumonia is a leading cause of morbidity and mortality throughout the world. Of the gram-positive pathogens that cause pneumonia, Streptococcus pneumoniae and Staphylococcus aureus are the most common. The diagnosis of gram-positive pneumonia remains less than satisfactory, and newer diagnostic techniques such as antibody- and polymerase chain reaction-based antigen detection have yet to prove themselves. Drug resistance among gram-positive organisms is now endemic throughout the world and remains a serious therapeutic problem despite the availability of new antimicrobials. Efforts to control the spread of resistant strains include, in the case of S. aureus, stringent isolation policies and topical treatment to reduce carriage and, for S. pneumoniae, increased use of available vaccines and the develop- ment of more immunogenic vaccines.

Immunogenicity of pneumococcal conjugate vaccines

BACKGROUND

Prevention of pneumococcal infections is a public health priority because of the high impact of the disease and because of the increasing problems due to antimicrobial resistance. Traditional vaccines, consisting of purified capsular polysaccharides (PSs) of Streptococcus pneumoniae, are not immunogenic in young children. In addition they confer only limited protection in patients with immunodeficiencies and hematologic malignancies.

IMMUNOGENICITY OF PNEUMOCOCCAL CONJUGATE VACCINES

Immunogenicity of the PS vaccine has been enhanced by coupling pneumococcal PSs to proteins to produce a conjugate vaccine. Conjugate molecules are designed to possess T cell dependent properties, such as immunogenicity in early infancy, stimulation of high levels of IgG isotype antibodies and enhanced immunologic memory responses. In the clinical studies multivalent pneumococcal conjugate vaccines have been shown to induce an IgG-dominating serum antibody response against common pneumococcal serotypes causing infections in children. A booster dose later in life creates a robust and rapid antibody response, indicating the existence of immunologic memory in primed children. Antibodies induced by conjugate vaccines are functionally active, as demonstrated by their high avidity and opsonophagocytic activity.