Antimicrobial-drug use and changes in resistance in Streptococcus pneumoniae

Impact of private use of the 13-valent pneumococcal conjugate vaccine (PCV13) on pneumococcal carriage among Portuguese children living in urban and rural regions

In Portugal, the 13-valent pneumococcal conjugate vaccine (PCV13) was commercially available between 2010 and 2015, following a decade of private use of PCV7. We evaluated changes on serotype distribution and antimicrobial susceptibility of pneumococci carried by children living in two regions of Portugal (one urban and one rural). Three epidemiological periods were defined: pre-PCV13 (2009-2010), early-PCV13 (2011-2012), and late-PCV13 (2015-2016). Nasopharyngeal samples (n = 4,232) were obtained from children 0-6 years old attending day-care centers. Private use of PCVs was very high in both regions (>75%). Pneumococcal carriage remained stable and high over time (62.1%, 62.4% and 61.6% (p = 0.909) in the urban region; and 59.8%, 62.8%, 59.5% (p = 0.543) in the rural region). Carriage of PCV7 serotypes remained low (5.3%, 7.8% and 4.3% in the urban region; and 2.5%, 3.7% and 4.8% in the rural region). Carriage of PCV13 serotypes not targeted by PCV7 decreased in both the urban (16.4%, 7.3%, and 1.6%; p < 0.001) and rural regions (13.2%, 7.8%, and 1.9%; p < 0.001). This decline was mostly attributable to serotype 19A (14.1%, 4.4% and 1.3% in the urban region; and 11.1%, 3.6% and 0.8% in the rural region, both p < 0.001). Serotype 3 declined over time in the urban region (10.1%, 4.4%, 0.8%; p < 0.001) and had no obvious trend in the rural region (4.2%, 6.7%, 2.4%; p = 0.505). Serotype 6C decreased in both regions while serotypes 11D, 15A/B/C, 16F, 21, 22F, 23A/B, 24F, 35F, and NT were the most prevalent in the late-PCV13 period. Intermediate resistance to penicillin and non-susceptibility to erythromycin decreased significantly in both regions (19.5%, 13.3%, and 9.3%; and 25.4%, 25.9%, and 13.4%; both p < 0.001, respectively in the urban region; and 12.4%, 11.1%, and 2.8% (p < 0.001); and 15.3%, 14.7%, and 9.2% (p = 0.037), respectively, in the rural region). In conclusion, private use of PCV13 led to significant changes on the pneumococcal population carried by children in Portugal.

Population structure, epidemiology and antibiotic resistance patterns of Streptococcus pneumoniae serotype 5: prior to PCV-13 vaccine introduction in Eastern Gambia

Background

Streptococcus pneumoniae serotype 5 is among the most common serotypes causing invasive pneumococcal disease (IPD) in The Gambia. We anticipate that introduction of the 13-valent pneumococcal conjugate vaccine (PCV-13) into routine vaccination in The Gambia will reduce serotype 5 IPD. However, the emergence of new clones that have altered their genetic repertoire through capsular switching or genetic recombination after vaccination with PCV-13 poses a threat to this public health effort. In order to monitor for potential genetic changes post-PCV-13 vaccination, we established the baseline population structure, epidemiology, and antibiotic resistance patterns of serotype 5 before the introduction of PCV-13.

Methods

Fifty-five invasive S. pneumoniae serotype 5 isolates were recovered from January 2009 to August 2011 in a population-based study in the Upper River Region of The Gambia. Serotyping was done by latex agglutination and confirmed by serotype-specific Polymerase Chain Reaction (PCR). Genotyping was undertaken using Multilocus Sequence Typing (MLST). Antimicrobial sensitivity was done using disc diffusion. Contingency table analyses were conducted using Pearson’s Chi² and Fisher’s exact test. Clustering was performed using Bionumerics version 6.5.

Results

MLST resolved S. pneumoniae serotype 5 isolates into 3 sequence types (ST), namely ST 289(6/55), ST 3339(19/55) and ST 3404(30/55). ST 289 was identified as the major clonal complex. ST 3339, the prevalent genotype in 2009 [84.6 % (11/13)], was replaced by ST 3404 [70.4 % (19/27)] in 2010 as the dominant ST. Interestingly, ST 3404 showed lower resistance to tetracycline and oxacillin (P < 0.001), an empirical surrogate to penicillin in The Gambia.

Conclusions

There has been an emergence of ST 3404 in The Gambia prior to the introduction of PCV-13. Our findings provide important background data for future assessment of the impact of PCV-13 into routine immunization in developing countries, such as The Gambia.

ASHP therapeutic position statement on strategies for identifying and preventing pneumococcal resistance

The incidence of MDRSP continues to increase, causing significant morbidity and mortality. Health care providers should seize the opportunity to promote the judicious use of antimicrobials and vaccinate patients with the pneumococcal vaccines as a means to lessen this significant health problem. Pharmacists are poised to play a key role in patient care by assessing for the need and administering vaccines in compliance with the current guidelines. A pharmacist should have a key role on the antimicrobial stewardship team.

Impact of over-the-counter restrictions on antibiotic consumption in Brazil and Mexico

Background

In Latin American countries over-the-counter (OTC) dispensing of antibiotics is common. In 2010, both Mexico and Brazil implemented policies to enforce existing laws of restricting consumption of antibiotics only to patients presenting a prescription. The objective of the present study is therefore to evaluate the impact of OTC restrictions (2010) on antibiotics consumption in Brazil and Mexico.

Methods and Findings

Retail quarterly sales data in kilograms of oral and injectable antibiotics between January 2007 and June 2012 for Brazil and Mexico were obtained from IMS Health. The unit of analysis for antibiotics consumption was the defined daily dose per 1,000 inhabitants per day (DDD/TID) according to the WHO ATC classification system. Interrupted time series analysis was conducted using antihypertensives as reference group to account for changes occurring independently of the OTC restrictions directed at antibiotics. To reduce the effect of (a) seasonality and (b) autocorrelation, dummy variables and Prais-Winsten regression were used respectively.

Between 2007 and 2012 total antibiotic usage increased in Brazil (from 5.7 to 8.5 DDD/TID, +49.3%) and decreased in Mexico (10.5 to 7.5 DDD/TID, −29.2%). Interrupted time series analysis showed a change in level of consumption of −1.35 DDD/TID (p<0.01) for Brazil and −1.17 DDD/TID (p<0.00) for Mexico. In Brazil the penicillins, sulfonamides and macrolides consumption had a decrease in level after the intervention of 0.64 DDD/TID (p = 0.02), 0.41 (p = 0.02) and 0.47 (p = 0.01) respectively. While in Mexico it was found that only penicillins and sulfonamides had significant changes in level of −0.86 DDD/TID (p<0.00) and −0.17 DDD/TID (p = 0.07).

Conclusions

Despite different overall usage patterns of antibiotics in Brazil and Mexico, the effect of the OTC restrictions on antibiotics usage was similar. In Brazil the trend of increased usage of antibiotics was tempered after the OTC restrictions; in Mexico the trend of decreased usage was boosted.

Geographic and temporal trends in antimicrobial nonsusceptibility in Streptococcus pneumoniae in the post-vaccine era in the United States

BACKGROUND

We examined whether observed increases in antibiotic nonsusceptible nonvaccine serotypes after introduction of pneumococcal conjugate vaccine in the United States in 2000 were driven primarily by vaccine or antibiotic use.

METHODS

 Using active surveillance data, we evaluated geographic and temporal differences in serotype distribution and within-serotype differences during 2000-2009. We compared nonsusceptibility to penicillin and erythromycin by geography after standardizing differences across time, place, and serotype by regressing standardized versus crude proportions. A regression slope (RS) approaching zero indicates greater importance of the standardizing factor.

RESULTS

 Through 2000-2006, geographic differences in nonsusceptibility were better explained by within-serotype prevalence of nonsusceptibility (RS 0.32, 95% confidence interval [CI], .08-.55 for penicillin) than by geographic differences in serotype distribution (RS 0.71, 95% CI, .44-.97). From 2007-2009, serotype distribution differences became more important for penicillin (within-serotype RS 0.52, 95% CI, .11-.93; serotype distribution RS 0.57, 95% CI, .14-1.0).

CONCLUSIONS

 Differential nonsusceptibility, within individual serotypes, accounts for most geographic variation in nonsusceptibility, suggesting selective pressure from antibiotic use, rather than differences in serotype distribution, mainly determines nonsusceptibility patterns. Recent trends suggest geographic differences in serotype distribution may be affecting the prevalence of nonsusceptibility, possibly due to decreases in the number of nonsusceptible serotypes.

Factors affecting caregivers' use of antibiotics available without a prescription in Peru

OBJECTIVE

To determine factors that affect caregivers' decisions about antibiotic use in children in settings where antibiotics are available without prescription.

METHODS

In a house-to-house survey, 1200 caregivers in 3 periurban districts of Lima, Peru, were asked about antibiotic use in young children.

RESULTS

In this sample, 87.2% of children aged <5 years had received an antibiotic drug in their lives; 70.3% had received antibiotics before 1 year of age, and 98.8% of those had been prescribed by a physician. Given hypothetical cases of common cold and nondysenteric diarrhea, caregivers would seek medical advice in 76.4% and 87.1%, respectively, and 84.6% of caregivers said they respected medical decisions even if an antibiotic was not prescribed. Caregivers with high school-level education accepted 80% more medical decisions of not using an antibiotic and used fewer pharmacist-recommended antibiotics. For each additional year of life, the risk of self-medicated antibiotic use and the use of pharmacist-recommended antibiotics increased in 30%. (OR: 1.3, 95% CI: 1.1-1.4, P = .001 and OR: 1.3, 95% CI: 1.2-1.5, P < .001, respectively). Caregivers respected a medical decision of not prescribing an antibiotic 5 times more when physicians had explained the reason for their advice (OR: 5.0, 95% CI: 3.2-7.8, P < .001).

CONCLUSIONS

Prescribed antibiotic use in these young children is common. Even if they are available without prescription, caregivers usually comply with medical advice and follow physicians' recommendations when antibiotics are not prescribed. Improving physician prescribing habits could reduce irrational antibiotic use, decreasing future caregiver-driven misuse.

Variations in the management of pneumonia in pediatric emergency departments: compliance with the guidelines

OBJECTIVE

We sought to assess compliance with evidence-based guidelines for the management of pediatric pneumonia, including the variations in tests ordered and antimicrobials prescribed. Our primary hypothesis was that compliance with the treatment recommendations from the most current guidelines would be low for antimicrobial prescriptions.

METHODS

We conducted a chart review at the Children's Hospital in London, Ont., to assess variation in the management of pediatric pneumonia. All patients aged 3 months to 18 years seen at the pediatric emergency department between Apr. 1, 2006, and Mar. 31, 2007, with a diagnosis of pneumonia were eligible for inclusion in the study.

RESULTS

Compliance with management guidelines was 59.7% (95% confidence interval [CI] 53%-66%, n = 211) in children 5-18 years old and 83.0% (95% CI 80%-86%, n = 605) in children 3 months to 5 years old. Significant variation existed in the choice of antimicrobial agent for children with pneumonia, with nonrecommended agents frequently prescribed.

CONCLUSION

Significant variation existed in the management of pediatric pneumonia, and adherence to guidelines was low for the group of patients aged 5-18 years. Future studies should attempt to provide guidance to distinguish between viral and bacterial etiology to allow judicious use of antimicrobials.

Seasonal distribution of otitis media pathogens among Costa Rican children

BACKGROUND

Otitis media is an important cause of pediatric consultation, and knowledge of yearly pathogen distribution might improve antimicrobial selection.

OBJECTIVES

To determine the seasonal pathogen and antimicrobial resistance distribution among Costa Rican children with otitis media.

METHODS

Between 1999 and 2004, 952 children with otitis media, aged 3-144 months who participated in various clinical trials, were analyzed. Data obtained from this period were compared against historical data collected between 1992 and 1997.

RESULTS

Five hundred sixteen (52%) children had a baseline middle ear fluid pathogen isolated. The most common pathogens were Streptococcus pneumoniae 252 (49%), Haemophilus influenzae 190 (37%), S. pyogenes 38 (7%), and Moraxella catarrhalis 36 (7%). The overall proportion of H. influenzae (24-37%; P = 0.01) and the production of beta-lactamase producing H. influenzae (2.6-7%; P = 0.02) increased from 1992-1997 to 1999-2004. There was a nonstatistically significant trend for a higher frequency of S. pneumoniae and H. influenzae isolates detected during the rainy season than during the dry season: S. pneumoniae 58% versus 42% but not significant (P = 0.1) and H. influenzae 68% versus 32% (P = 0.06), respectively. During the rainy season, penicillin-nonsusceptible S. pneumoniae was identified more frequently (38.5%) than during the dry season (18%) (P = 0.003; odds ratio: 2.94; 95% confidence interval: 1.4-6.45). Penicillin-nonsusceptible S. pneumoniae decreased from 46.5% (1999-2001) to 16% (2002-2003) and this was associated with a significant decline of a circulating 19F penicillin-resistant S. pneumoniae serotype (from 89% to 26%), respectively.

CONCLUSIONS

S. pneumoniae and H. influenzae are the 2 most common pathogens producing otitis media in Costa Rican children. An increase in the number of H. influenzae and M. catarrhalis was observed in recent years. Penicillin-nonsusceptible S. pneumoniae isolates were more commonly observed during the rainy season, in which increased morbidity with respiratory pathogens is observed.

Risk factors for development of multiple-class resistance to Streptococcus pneumoniae Strains in Belgium over a 10-year period: antimicrobial consumption, population density, and geographic location

We investigated the impact of the usage of antibiotics in ambulatory patients in Belgium in 147 defined geographical circumscriptions and at the individual isolate level. The study included 14,448 Streptococcus pneumoniae strains collected by the Belgium national reference lab from 1994 to 2004. Additional risk factors for resistance, such as population density/structure and day care attendance, were investigated for the same time-space window. A statistical model that included resistance to two or more antimicrobial classes offered the best fit for measuring the changes in nonsusceptibility to penicillin, macrolides, and tetracycline over time and place in Belgium. Analysis at the geographic level identified antimicrobial consumption with a 1-year lag (0.5% increase per additional defined daily dose) and population density as independent predictors of multiple resistance. Independent risk factors at the isolate level were age (odds ratio [OR], 1.55 for children aged <5 years), population density (7% increase in multiple resistance per 100 inhabitants/km(2)), conjugate 7-valent vaccine serotype (OR, 14.3), location (OR, 1.55 for regions bordering high-resistance France), and isolate source (OR, 1.54 for ear isolates). The expansion of multiple-resistant strains explains most of the overall twofold increase and subsequent decrease in single antimicrobial resistance between 1994 and 2004. We conclude that factors in addition to antibiotic use, such as high population density and proximity to high-resistance regions, favor multiple resistance. Regional resistance rates are not linearly related to actual antibiotic use but are linked to past antibiotic use plus a combination of demographic and geographic factors.

Modeling pneumococcal resistance to penicillin in southern Sweden using artificial neural networks

In recent decades, penicillin-resistant pneumococci (PRP) have emerged and spread rapidly between and within countries over the world. In this study we developed an iterative artificial neural network (ANN) model to describe and predict the spread of PRP in space and time as a function of antibiotic consumption and a number of different confounders. Retrospective data from 1997 to 2000 on an international epidemic PRP clone (serotype 9V) and antibiotic consumption data from Southern Sweden were used to train the ANN models and data from 2001 to 2003 for evaluation of the model predictions. Five different ANN models were trained, each with independent topology optimization for alternative sets of input variables to find the most descriptive model. The model containing all variables was the only one performing better than the reference linear models, as assessed by the correlation between predictions and observations. The inability to identify a smaller subset of most predictive parameters may reflect either diffuse causal mechanisms or just the absence of critical experimental indicators from the dataset. The iterative ANN model identified is useful to predict future data. The sensitivity analysis of the model suggests that past incidence has a small effect on the number of PRP cases.

Macrolide and ketolide resistance with Streptococcus pneumoniae

Antimicrobial agents in the macrolide family have long been considered drugs of potential utility in the management of infections caused by Streptococcus pneumoniae. However, with the emergence of macrolide resistance, the clinical value of macrolides in pneumococcal infections is threatened. In part, as a consequence of the development of macrolide resistance, recently the first agent in the ketolide antimicrobial class, telithromycin, was developed and introduced into clinical practice. The ketolides are macrolide antimicrobials whose chemistry has been modified so as avoid the effects of the most common mechanisms of macrolide resistance with S pneumoniae. This discussion reviews the current state of resistance to macrolides and ketolides with S pneumoniae in North America.

Will reduction of antibiotic use reduce antibiotic resistance?: The pneumococcus paradigm

Community-acquired respiratory infections in general, and those caused by S. pneumoniae in particular, are the main reason for prescribing antimicrobials in young children. Antibiotic drug abuse is common. This is the basis for the initiative for the reduction in antibiotic use. However, failure to consider that not all antibiotics are similar in their effect on promotion of resistance has led to continuous emerging resistance. In the present article, the trends in prescribing antibiotics in young children and their interrelation with antibiotic resistance among clinical respiratory isolates of S. pneumoniae in children will be reviewed, along with theoretical considerations and research evidence that led to concluding that among antibiotics, the least resistance-promoting drug for S. pneumoniae is amoxicillin (+/- clavulanate), whereas oral cephalosporins and azithromycin demonstrate a higher resistance-promotion potential in the individual population in the community. Although antibiotics differ in their resistant-promotion potential, all still do promote resistance.

Antibacterial Use andStreptococcus pneumoniaePenicillin Resistance: A Temporal Relationship Model

The nature of the temporal relationship between antibacterial consumption and Streptococcus pneumoniae penicillin resistance is investigated using population level data across time. IMS Health Global Services provided national outpatient antibiotic prescription data for the years 1996-2003 from France, Spain, Italy, Germany, the United Kingdom, and the United States. Surveillance data consist of S. pneumoniae isolates obtained from a surveillance database in the same geographic regions from 1996 to 2003. A linear mixed model for repeated measures was used to analyze the association between resistance and several antibacterial classes through time. Changes in penicillin resistance through time in any country are better explained by the weighted cumulative antibacterial consumption with a 2-year lag. Narrow-spectrum penicillins are associated with lower resistance rates. Large reductions in consumption at the population level are needed to affect resistance. There is a peak level of penicillin resistance associated with cumulative exposure to a combination of antibiotic classes that is unique for every country.

Factors which influence Latino community members to self-prescribe antibiotics

BACKGROUND

Although there is consistent evidence of a link between antibiotic use and increasing antimicrobial resistance in the community, inappropriate use of antimicrobials continues to be a global problem.

OBJECTIVE

To describe knowledge, attitudes, and practices of Latino community members in upper Manhattan regarding use of antibiotics.

METHODS

Written questionnaires and eight focus groups comprised of Hispanic community members (three groups), bodega employees, and healthcare providers (one group) in a Latino neighborhood in New York City.

RESULTS

There were major knowledge deficits regarding use of antibiotics. Informants reported taking antibiotics for pain or other conditions as well as for symptoms of infection. Antibiotics were frequently obtained from bodegas without prescription, but generally only for adults, not for children.

DISCUSSION

Interventions to improve antibiotic use that are focused on the formal healthcare system (e.g., clinicians, pharmacists, persons with health insurance) are unlikely to be effective with recently immigrated Latino community members. Successful interventions for this population should include targeted messages to bodega employees, community organizations, and children and their parents.

Community prescribing and resistant Streptococcus pneumoniae

We investigated the association between prescribing antimicrobial agents and antimicrobial resistance of Streptococcus pneumoniae among children with acute otitis media in southern Israel. During a 6-year period, all prescriptions of a sample of ≈20% of Jewish and Bedouin children <5 years of age were recorded and all pneumococcal isolates from middle ear fluid were collected. Although antimicrobial drug use was significantly higher in Bedouin children, the proportion of S. pneumoniae isolates with penicillin MIC ≥1.0 μg/mL was significantly higher in Jewish children. In both populations, antimicrobial prescriptions were markedly reduced over time, especially for penicillins and erythromycin. In contrast, azithromycin prescriptions increased from 1998 to 2001 with a parallel increase in macrolide and multidrug resistance. Penicillin resistance was associated with macrolide resistance. These findings strongly suggest that azithromycin affects increased antimicrobial resistance, including multidrug resistance, in S. pneumoniae.

Appropriate Outpatient Macrolide Use in Community‐Acquired Pneumonia

PURPOSE

To review current guidelines concerning the outpatient management of community-acquired pneumonia (CAP), to discuss antibiotic resistance and its relation to outcomes, and to define the appropriate use of newer macrolides in CAP.

DATA SOURCES

Comprehensive review of the scientific literature, comparison of published clinical practice guidelines, and expert opinion.

CONCLUSIONS

Despite increasing knowledge regarding its etiology and pathogenesis, CAP remains the seventh leading cause of death in the United States. Although 80% of all patients with CAP are treated as outpatients, over 1 million hospital admissions due to CAP occur each year. From an employer perspective, total annual employer costs were fivefold greater for patients with pneumonia than for those who were not affected. Appropriate antimicrobial choices should lead to improved outcomes. Reports of increasing resistance of pathogens associated with CAP, increasing frequency of atypical pathogens, and the availability of an increasing number of antimicrobials have made treatment decisions more involved.

IMPLICATIONS FOR PRACTICE

In an effort to improve outcomes, several guidelines have been published recommending appropriate antimicrobial agents to treat CAP in different patient populations. All guidelines base treatment recommendations on the hospitalization status of the patient, and all agree that coverage of atypical pathogens as part of an initial empirical regimen is important. Comorbidity and modifying factors that may increase the risk of infection with resistant organisms also are taken into account. Controversy exists regarding the use of newer macrolides versus newer fluoroquinolones as initial empirical therapy. The applicability of the reported increasing resistance of common pneumonia pathogens to outcomes in regimens containing newer macrolides is a subject of debate. Defining appropriate antimicrobial use in different patient groups should help achieve better outcomes and allay the development of resistance.

Fluoroquinolone prescribing in the United States: 1995 to 2002

PURPOSE

To measure changes in the rate and type of fluoroquinolones prescribed in the United States from 1995 to 2002.

METHODS

We performed a longitudinal analysis of the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey of adult visits to physicians in ambulatory clinics and emergency departments throughout the United States from 1995 to 2002. The main outcomes were fluoroquinolone prescribing rates and prescribing in accordance with Food and Drug Administration approval as of December 2002.

RESULTS

Between 1995 and 2002, fluoroquinolones became the most commonly prescribed class of antibiotics to adults in the United States. Fluoroquinolone prescribing rose threefold, from 7 million visits in 1995 to 22 million visits in 2002 (P < 0.0001). Fluoroquinolone prescribing increased as a proportion of overall antibiotic prescribing (from 10% to 24%; P < 0.0001) and as a proportion of the U.S. population (from 39 to 106 prescriptions per 1000 adults; P < 0.001). These increases were due to the use of newer fluoroquinolones with activity against Streptococcus pneumoniae. Forty-two percent of fluoroquinolone prescriptions were for nonapproved diagnoses. Among patients receiving antibiotics, nonapproved fluoroquinolone prescribing increased over time (odds ratio = 1.18 per year; 95% confidence interval: 1.13 to 1.24).

CONCLUSION

Fluoroquinolone prescribing increased threefold in outpatient clinics and emergency departments in the United States from 1995 to 2002. Fluoroquinolones became the most commonly prescribed class of antibiotics to adults in 2002. Nonapproved fluoroquinolone prescribing was common and increased over time. Such prescribing patterns are likely to be followed by an increasing prevalence of fluoroquinolone-resistant bacteria.

Oxazolidinones: new players in the battle against multi-resistant Gram-positive bacteria

For many years the pharmaceutical industry did not pursue the development of antimicrobial agents that specifically targeted Gram-positive bacteria. Semi-synthetic penicillins and vancomycin were the mainstays of therapy for methicillin-susceptible and -resistant strains of staphylococci, respectively, as was penicillin for Streptococcus pneumoniae and beta-lactam-aminoglycoside combinations for serious enterococcal infections. In the 1980s enterococci resistant to glycopeptides emerged, followed shortly thereafter by a dissemination of penicillin-insensitive S. pneumoniae and, more recently, the occurrence of vancomycin-intermediately susceptible Staphylococcus aureus. The emergence of fully glycopeptide-resistant S. aureus is clearly on the horizon. Multi-resistant Gram-positive bacteria now pose an important therapeutic challenge for clinicians. New drugs with activity against some of these dangerous pathogens have recently been pursued, and linezolid, the first member of the oxazolidinone class, has now been licensed for clinical use in many countries. This drug has excellent in vitro and in vivo activity against all clinically relevant multi-resistant Gram-positive cocci and fills an important void in infectious disease chemotherapy.

Management of acute bronchitis in healthy adults

Acute respiratory infections (ARIs) are the most common infections in humans, accounting for half of all acute conditions each year in the United States. Acute bronchitis episodes represent a significant portion of these illnesses. This article focuses on acute bronchitis in otherwise healthy individuals.

Availability of antibiotics without prescription in New York City

Misuse of antibiotics in the community has been associated with emergence of increasingly antibiotic-resistant bacterial strains. Although antibiotics in the United States are to be prescribed by a health care provider, the extent to which they are obtained by other means is not known. The purpose of this article is to describe a survey of the availability of nonprescription antibiotics in neighborhood independent businesses in several Manhattan, New York, neighborhoods. A survey was conducted of 101 stores in three neighborhoods--one primarily Hispanic; one primarily black, non-Hispanic; and one primarily white, non-Hispanic. Antibiotics were available in all stores in the Hispanic neighborhood (n = 34), but in none of the others (P < .001). If efforts to rationalize the use of antibiotics are to be successful, the beliefs and cultural norms of subpopulations must be considered, and interventions must be culturally relevant.

Limited spread of penicillin-nonsusceptible pneumococci, Skåne County, Sweden

In response to increasing frequencies of penicillin-nonsusceptible pneumococci (PNSP), for which the MIC of penicillin was >0.12 mg/L, in Skåne County, southern Sweden, national recommendations were initiated in 1995 to limit the spread of pneumococci with high MICs (> or =0.5 mg/L) of penicillin (PRP), especially among children of preschool age. Traditional communicable disease control measures were combined with actions against inappropriate antimicrobial drug use. During the first 6 years that these recommendations were applied in Skåne County, the average frequency of penicillin-resistant pneumococci has been stable at =2.6%, as has the average PNSP frequency (7.4%). However, PNSP have been unevenly distributed in the county, with the highest frequencies in the southwest. Simultaneously, the rate of antimicrobial drug use for children <6 years of age was reduced by 20%. Thus the spread of PNSP between and within the municipalities in the county has been limited.

Linezolid, levofloxacin, and vancomycin against vancomycin-tolerant and fluoroquinolone-resistant Streptococcus pneumoniae in an in vitro pharmacodynamic model

STUDY OBJECTIVE

To compare the pharmacodynamic profiles of linezolid, levofloxacin, and vancomycin against clinical strains of Streptococcus pneumoniae, including vancomycin-tolerant and fluoroquinolone-resistant isolates.

DESIGN

In vitro pharmacodynamic model.

SETTING

Biosafety level 2, university research laboratory. BACTERIAL STRAINS: Ciprofloxacin-susceptible (79), ciprofloxacin-resistant (R921), and vancomycin-tolerant (P9802-020) clinical strains of S. pneumoniae.

INTERVENTION

An in vitro pharmacodynamic model was used to simulate standard dosing regimens of linezolid, levofloxacin, and vancomycin against the isolates 79, R921, and P9802-020.

MEASUREMENTS AND MAIN RESULTS

Bacterial density was profiled over 48 hours. Minimum inhibitory concentrations (MICs) for linezolid, levofloxacin, and vancomycin, respectively were 1, 1, 0.5 microg/ml for isolate 79; 1, 4, 0.5 microg/ml for R921; and 0.5, 0.5, 0.5 microg/ml for P9802-020. Vancomycin minimum bactericidal concentration (MBC) values varied across large ranges for the tested strains. Linezolid achieved 99.9% kill against 79 and R921 by 24 and 28 hours, respectively. Levofloxacin achieved 99.9% kill against 79 and P9802-020 by 28 and 4 hours, respectively. Vancomycin achieved 99.9% kill against 79 and R921 by 8 and 24 hours, respectively. Levofloxacin did not demonstrate activity against R921 at the 48-hour end point. Minimal kill (< 2 log) at 48 hours was noted for vancomycin and linezolid against P9802-020. Conclusion. Vancomycin tolerance appeared to be more reliably characterized by persistent viability in time-kill analyses than by MBC:MIC ratios. Vancomycin exhibited bactericidal activity against the non-vancomycin-tolerant strains of S. pneumoniae. Linezolid exhibited both bactericidal and bacteriostatic activity against all three strains tested, whereas levofloxacin demonstrated bactericidal activity against the fluoroquinolone-susceptible isolates. Further investigation of treatment alternatives for infections due to vancomycin-tolerant S. pneumoniae are needed.

Longitudinal trends in fluoroquinolone resistance among Enterobacteriaceae isolates from inpatients and outpatients, 1989-2000: differences in the emergence and epidemiology of resistance across organisms

We conducted a 12-year study to identify and compare trends in annual prevalence of fluoroquinolone (FQ) resistance among Enterobacteriaceae isolates obtained from inpatients and outpatients in our health care system. A total of 46,070 clinical Enterobacteriaceae isolates underwent susceptibility testing. Although there were significant increases in inpatient FQ resistance for all Enterobacteriaceae, FQ resistance trends differed significantly across Enterobacteriaceae (P<.001). For isolates obtained from outpatients, only Escherichia coli and Proteus mirabilis demonstrated significant increases in FQ resistance (P<.001 for each). Trends in outpatient FQ resistance also differed significantly across Enterobacteriaceae (P<.001). There were significant differences between inpatient and outpatient FQ resistance trends for all Enterobacteriaceae except P. mirabilis and Enterobacter cloacae. Although hospital-wide use of certain antibiotics correlated significantly with inpatient FQ resistance, these correlations differed substantially across organisms. Efforts to elucidate the epidemiology of FQ resistance and identify targets for intervention must recognize and account for the variability of FQ resistance across organisms and clinical settings.

Antimicrobial peptides in animals and their role in host defences

Domesticated animals have a large variety of antimicrobial peptides that serve as natural innate barriers limiting microbial infection or, in some instances, act as an integral component in response to inflammation or microbial infection. These peptides differ in size, composition, mechanisms of activity and range of antimicrobial specificities. They are expressed in many tissues, polymorphonuclear leukocytes, macrophages and mucosal epithelial cells. There is a small group of anionic antimicrobial peptides found in ruminants and a much larger group of cationic antimicrobial peptides found in all domesticated animals. The cationic peptides include linear, helical peptides, linear peptides rich in proline and cysteine-stabilized peptides with a beta-sheet and are commonly referred to as cathelicidins and defensins. These peptides are generally broad-spectrum for Gram-positive bacteria, Gram-negative bacteria and fungi (e.g. myeloid antimicrobial peptides, alpha-, beta-defensins, and protegrins) or are specific to one of these groups (e.g. porcine cecropin P1, Bac5, Bac7, PR-39 and prophenin).

Characterisation of invasive pneumococcal isolates in Catalan children up to 5 years of age, 1989–2000

Ninety-six Streptococcus pneumoniae strains isolated between January 1989 and December 2000 from usually sterile sites of children aged < 5 years of age were included in the study. Resistance to penicillin (38.6% intermediate, 10.4% high-level), cefotaxime (20.8%), tetracycline (41.7%), chloramphenicol (33.3%) and erythromycin (27.1%), as well as serogroup/type, were related to age and pathology. Strains from children aged < 2 years showed the highest penicillin resistance rate. Resistance to penicillin, tetracycline, chloramphenicol and erythromycin was the most common pattern (18.8% of strains). Most isolates (80.2%) belonged to serogroups/types included in the heptavalent conjugate vaccine.

Antibiotic use in Hispanic households, New York city

Trained interviewers visited 631 inner city households to determine community prevalence and predictors of antibiotic use. Infectious disease symptoms were reported in 911 (33.2%) of 2,743 household members in the previous 30 days: medical attention was sought by 441 (48.4%) of 911 persons, and 354 (38.9%) of 911 took antibiotics for symptoms. Reported symptoms were respiratory (68.9%), gastrointestinal (15.3%), fever (12.8%), and skin infection (2.8%). Medical attention was sought significantly more often among those with chronic illness, those born in the United States, and those with fever, runny nose, or skin infections (all p<0.05). Antibiotics were taken significantly more often among those with poor health, those who spent more time at home, and those with fever and respiratory symptoms. Interventions to promote judicious use of antibiotics must include clinicians and the public, and for the Hispanic population such interventions must also be culturally relevant and provided in Spanish.

Current Management Issues Associated with Community-Acquired Pneumonia

Community-acquired pneumonia (CAP) is a significant cause of morbidity, mortality, and increased cost. Despite numerous managementguidelines, CAP continues to existas a challenge to the learned clinician. Due to a lack of sensitive diagnostic testing, causative pathogens are often not identified, making most therapy empiric. Increasing levels of bacterial resistance to available antimicrobials worldwide has been implicated in driving up the costs of treatment and adversely effecting clinical outcomes. Pharmacists can be part of the solution by encouraging appropriate antimicrobial selection based on resistance patterns in their communities and ensuring appropriate vaccines are employed to prevent CAP.

Decreasing beta-lactam resistance in Pneumococci from the Memphis region: analysis of 2,152 isolates From 1996 to 2001

STUDY OBJECTIVES

The Memphis region historically has had high pneumococcal antibiotic resistance rates. In recent years, we have seen a significant shift in antibiotic use away from beta-lactams toward the newer quinolones and macrolides. We hypothesized that these changes would cause a shift in pneumococcal antibiotic resistance patterns.

DESIGN

Retrospective cohort study.

SETTING

A large private hospital system.

PATIENTS AND METHODS

We analyzed the antibiotic susceptibility patterns of 2,152 pneumococcal isolates obtained in the Memphis area from 1996 to 2001. Isolates were categorized as invasive or noninvasive and antibiotic resistance was classified according to the 2000 guidelines of the National Committee for Clinical Laboratory Standards.

RESULTS

Over the study period, the proportion of penicillin-susceptible noninvasive pneumococcal isolates taken from children increased from 22 to 44% (p = 0.0004 [for trend across the 6-year period]). In noninvasive isolates taken from adults, penicillin susceptibility increased from 22 to 55% (p = 0.002), with a trend toward increasing sensitivity to cefotaxime (p = 0.02) in noninvasive isolates over the same period. The proportion of isolates with high-level penicillin resistance (ie, minimum inhibitory concentration, > or = 4 microg/mL) also decreased between 1996 and 2001 (p = 0.003). Clindamycin resistance in adult noninvasive isolates also declined (p = 0.002). The only adverse trend observed over this period was an increase in erythromycin resistance in noninvasive isolates from adults (p = 0.01). Resistance rates were significantly higher in children than in adults and were higher in noninvasive isolates than in invasive isolates.

CONCLUSIONS

The stabilization of beta-lactam resistance rates in our region suggests that a continuous increase in pneumococcal resistance to antibiotics is not inevitable and may be avoidable.

Diagnosis and treatment of acute otitis media: an assessment

OBJECTIVE

To assess compliance with the Centers for Disease Control and Prevention (CDC) evidence-based guidelines for the judicious use of antimicrobials in children with acute otitis media (AOM).

METHODS

Compliance with CDC's recommended diagnostic criteria and antimicrobial treatments for management of AOM was assessed by chart review and self-report for 29 community pediatricians in St. Louis, Missouri. For each physician, a simple random sample of AOM visits was selected and reviewed by trained reviewers. In addition, each physician completed a questionnaire.

RESULTS

Compliance with recommended diagnostic criteria was 38% (95% confidence interval: 34%-42%; n = 573) by chart audit and 41% (95% confidence interval: 24%-61%; n = 29) by self-report. Antimicrobial selection assessed by chart audit was consistent with CDC guidelines in 68% (95% confidence interval: 64%-72%) of visits for a new infection, 63% (95% confidence interval: 47%-78%) of visits for treatment failure, and 50% (95% confidence interval: 33%-67%) for recurrent disease. Self-reported compliance with treatment guidelines for new infection was 100% (95% confidence interval: 88%-100%) and 83% (95% confidence interval: 64%-94%) for treatment failure. Noncompliance was most frequently attributable to overuse of broad-spectrum antimicrobials. Most patients treated with amoxicillin received a 10-day course (98%). Subtherapeutic dosing occurred in 26% of patients treated with amoxicillin.

CONCLUSIONS

Overdiagnosis of AOM is common. Efforts to improve the judicious use of antimicrobials for AOM should focus on improving diagnostic accuracy, limiting the use of broad-spectrum antimicrobials to cases where they offer clinical benefit, and ensuring that amoxicillin dosing regimens are optimal.

Telithromycin- and fluoroquinolone-resistant Streptococcus pneumoniae in Taiwan with high prevalence of resistance to macrolides and beta-lactams: SMART program 2001 data

There is a high prevalence of beta-lactam- and macrolide-resistant Streptococcus pneumoniae in Taiwan. To understand the in vitro susceptibilities of recent isolates of S. pneumoniae to fluoroquinolones and telithromycin (which is not available in Taiwan), the MICs of 23 antimicrobial agents for 936 clinical isolates of S. pneumoniae isolated from different parts of Taiwan from 2000 to 2001 were determined by the agar dilution method. Overall, 72% of isolates were not susceptible to penicillin (with 61% being intermediate and 11% being resistant) and 92% were resistant to erythromycin. Telithromycin MICs were >or=1 microg/ml for 16% of the isolates, and for 99% of these isolates the MICs of all macrolides tested were >or=256 microg/ml; all of these isolates had the constitutive macrolide-lincosamide-streptogramin B phenotype. Eighty-eight percent of the isolates were resistant to three or more classes of drugs. The ciprofloxacin MICs were >or=4 microg/ml for six (0.6%) isolates from five patients collected in 2000 and 2001, and the levofloxacin MICs were >or=8 microg/ml for five of these isolates. Seven isolates for which ciprofloxacin MICs were >or=4 microg/ml, including one isolate recovered in 1999, belonged to three serotypes (serotype 19F, five isolates; serotype 23A, one isolate; and serotype 23B, one isolate). The isolates from the six patients for which ciprofloxacin MICs were >or=4 microg/ml had different pulsed-field gel electrophoresis profiles and random amplified polymorphic DNA patterns, indicating that no clonal dissemination occurred over this time period. Despite the increased rate of fluoroquinolone use, the proportion of pneumococcal isolates for which ciprofloxacin MICs were elevated (>or=4 microg/ml) remained low. However, the occurrence of telithromycin resistance is impressive and raises concerns for the future.

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.

Linezolid and vancomycin, alone and in combination with rifampin, compared with moxifloxacin against a multidrug-resistant and a vancomycin-tolerant Streptococcus pneumoniae strain in an in vitro pharmacodynamic model

Potential alternatives, including linezolid, adjunctive rifampin, and moxifloxacin, were evaluated against vancomycin-tolerant (P9802-020) and vancomycin-susceptible clinical isolates of Streptococcus pneumoniae in an in vitro pharmacodynamic model. Vancomycin exhibited maximal killing of 2-log(10) CFU/ml against P9802-020. Linezolid, moxifloxacin, and linezolid plus rifampin exhibited 99.9% killing against both isolates. These alternatives should be considered for further evaluation against vancomycin-tolerant S. pneumoniae.

Geographic diversity and temporal trends of antimicrobial resistance in Streptococcus pneumoniae in the United States

Resistance of Streptococcus pneumoniae to antibiotics is increasing throughout the United States, with substantial variation among geographic regions. We show that patterns of geographic variation are best explained by the intensity of selection for resistance, which is reflected by differences between the proportions of resistance within individual serotypes, rather than by differences between the frequencies of particular serotypes. Using a mathematical transmission model, we analyzed temporal trends in the proportions of singly and dually resistant organisms and found that pneumococcal strains resistant to both penicillin and erythromycin are increasing faster than strains singly resistant to either. Using the model, we predict that by 1 July 2004, in the absence of a vaccine, 41% of pneumococci at the Centers for Disease Control and Prevention (CDC)'s Active Bacterial Core surveillance (ABCs) sites, taken together, will be dually resistant, with 5% resistant to penicillin only and 5% to erythromycin only.

Antimicrobial susceptibility and serotypes of nasopharyngeal Streptococcus pneumoniae in children with pneumonia and in children attending day-care centres in Fortaleza, Brazil

The susceptibility of nasopharyngeal Streptococcus pneumoniae to eight antibiotics was studied in 482 children under 5 years of age with community-acquired pneumonia and in 429 healthy pneumococci carriers in Fortaleza, Brazil. Serotyping of strains with pooled and type-specific antisera was also performed. Overall, S. pneumoniae was isolated from 499/911 (55%) children. The carriage rate in children attending day-care centres was higher (72%) than in children with pneumonia (50%) (P<0.001). MIC determination in 441 strains revealed 45% to be intermediate penicillin-resistant and 4% high penicillin-resistant strains. Resistance rates to co-trimoxazole and erythromycin were 42 and 23%, respectively. Serotyping of 211 penicillin-resistant and 58 randomly selected penicillin-susceptible isolates showed that 78% of the strains belonged to paediatric serogroups 6, 14, 19 and 23 (86% of the penicillin-resistant and 51% of the penicillin-susceptible strains, P=0.001). Resistance rates of S. pneumoniae to penicillin and co-trimoxazole in Fortaleza were higher than previously reported in Brazil and associated with paediatric serogroups 6, 14, 19 and 23.

Using hospital antibiogram data to assess regional pneumococcal resistance to antibiotics

Antimicrobial resistance to penicillin and macrolides in Streptococcus pneumoniae has increased in the United States over the past decade. Considerable geographic variation in susceptibility necessitates regional resistance tracking. Traditional active surveillance is labor intensive and costly. We collected antibiogram reports from North Carolina hospitals and assessed pneumococcal susceptibility to multiple agents from 1996 through 2000. Susceptibility in North Carolina was consistently lower than the national average. Aggregating antibiogram data is a feasible and timely method of monitoring regional susceptibility patterns and may also prove beneficial in measuring the effects of interventions to decrease antimicrobial resistance.

An analysis of why highly similar enzymes evolve differently

The TEM-1 and SHV-1 beta-lactamases are important contributors to resistance to beta-lactam antibiotics in gram-negative bacteria. These enzymes share 68% amino acid sequence identity and their atomic structures are nearly superimposable. Extended-spectrum cephalosporins were introduced to avoid the action of these beta-lactamases. The widespread use of antibiotics has led to the evolution of variant TEM and SHV enzymes that can hydrolyze extended-spectrum antibiotics. Despite being highly similar in structure, the TEM and SHV enzymes have evolved differently in response to the selective pressure of antibiotic therapy. Examples of this are at residues Arg164 and Asp179. Among TEM variants, substitutions are found only at position 164, while among SHV variants, substitutions are found only at position 179. To explain this observation, the effects of substitutions at position 164 in both TEM-1 and SHV-1 on antibiotic resistance and on enzyme catalytic efficiency were examined. Competition experiments were performed between mutants to understand why certain substitutions preferentially evolve in response to the selective pressure of antibiotic therapy. The data presented here indicate that substitutions at position Asp179 in SHV-1 and Arg164 in TEM-1 are more beneficial to bacteria because they provide increased fitness relative to either wild type or other mutants.

Possible overestimation of penicillin resistant Streptococcus pneumoniae colonization rates due to misidentification of oropharyngeal streptococci

Standard identification of Streptococcus pneumoniae by optochin and bile solubility testing can lead to ambiguous results for certain isolates. Newer bacteriologic identification techniques (e.g., DNA probes) now exist. In a prospective point prevalence study of oropharyngeal S. pneumoniae carriage rates among outpatients, we compared standard organism identification techniques to DNA probe testing. By standard identification criteria, 35 (4%) of 872 isolates were characterized as presumptive S. pneumoniae. Thirty of 35 presumptive isolates were recoverable for DNA probing; 9 (30%) presumptive isolates were confirmed using a DNA probe. The antimicrobial susceptibility pattern of these DNA probe positive isolates closely paralleled that of clinical blood isolates of S. pneumoniae obtained during the study period. The 21 (70%) DNA probe negative isolates, which may represent phylogenetically related species (such as S. mitis or S. oralis), had significantly reduced antimicrobial susceptibility patterns when compared with the DNA probe positive isolates. In colonization studies, if classic criteria (optochin disc zone and bile solubility) are the sole means of identification, S. pneumoniae penicillin resistance rates may be over-reported.

The role of antibacterial therapy of acute otitis media in promoting drug resistance

Treatment of acute otitis media (AOM) is the leading cause of antibacterial use in children in most developed countries. Rates of Streptococcus pneumoniae strains resistant to many classes of antibacterial agents have risen dramatically in many countries over the past 20 years. While more restricted use of antibacterial agents for AOM would almost certainly slow the rise in resistance, AOM is a potentially painful disease and may have suppurative complications such as mastoiditis. In this review, we discuss the prudent use of antibacterial agents for AOM and provide an overview of the epidemiology of S. pneumoniae resistance worldwide. Data from 10 placebo-controlled studies in patients with AOM show that antibacterial treatment is generally associated with a significantly higher cure rate than placebo. Of the three studies which analysed children <2 years of age, cure rates were 28 to 48% for placebo and 41 to 74% with antibacterial agents. Of the studies purporting to show no difference in cure rates between placebo and antibacterial therapy, the diagnostic criteria defining entry into the study were poor; therefore, the studies may have included many children without bacterial disease. Accurate diagnosis of AOM is the key element in reducing unnecessary antibacterial usage. Either pneumatic otoscopy or tympanometry can provide evidence of an effusion and the presence of an opaque, yellow or creamy white bulging eardrum will confirm AOM. Finally, the selection of appropriate antibacterial agents will reduce the rise in resistance. Low dosages of antibacterial agents used for prophylaxis select for resistance, and certain classes of drugs such as the sulfonamides and macrolides appear to do the same even at therapeutic doses. Amoxicillin at high dosages should remain the first-line antibacterial agent. In the future, use of vaccination strategies against pneumococci, influenza, respiratory syncytial virus and non-typeable Haemophilus influenzae will also decrease antibacterial use.

Clinical relevance of macrolide-resistant Streptococcus pneumoniae for community-acquired pneumonia

Macrolides are often the first choice for empirical treatment of community-acquired pneumonia. However, macrolide resistance among Streptococcus pneumoniae has escalated at alarming rates in North America and worldwide. Macrolide resistance among pneumococci is primarily due to genetic mutations affecting the ribosomal target site (ermAM) or active drug efflux (mefE). Prior antibiotic exposure is the major risk factor for amplification and perpetuation of resistance. Clonal spread facilitates dissemination of drug-resistant strains. Data assessing the impact of macrolide resistance on clinical outcomes are spare. Many experts believe that the clinical impact is limited. Ribosomal mutations confer high-grade resistance, whereas efflux mutations can likely be overridden in vivo. Favorable pharmacokinetics and pharmacodynamics, high concentrations at sites of infections, and additional properties of macrolides may enhance their efficacy. In this article, we discuss the prevalence of macrolide resistance among S. pneumoniae, risk factors and mechanisms responsible for resistance, therapeutic strategies, and implications for the future.

Rapidly increasing prevalence of penicillin-resistant Streptococcus pneumoniae in middle Tennessee: a 10-year clinical and molecular analysis

The clinical and molecular epidemiology of penicillin-resistant Streptococcus pneumoniae and the diagnostic accuracy of a six-primer PCR assay in identifying penicillin resistance were analyzed by using clinical isolates recovered over a 10-year period in middle Tennessee. The prevalence of non-penicillin-susceptible S. pneumoniae isolates (MIC, > or =0.1 microg/ml) increased from 10% in 1990 to 70% in 1999 (P < 0.001). Among S. pneumoniae isolates for which the penicillin MIC was > or =2 microg/ml (highly penicillin-resistant S. pneumoniae [PRSP]), 23 and 5% were resistant to at least three and at least five other antimicrobial classes, respectively. Pulsed-field gel electrophoresis identified 13 unique strain types, with type B accounting for 33% of PRSP isolates. The sensitivity, specificity, and negative and positive predictive values of the PCR assay in detecting PRSP were 99, 100, 99, and 100%, respectively. Penicillin resistance is rapidly increasing among S. pneumoniae isolates in Tennessee. The simultaneous detection of S. pneumoniae and high-level penicillin resistance can be accurately performed with the six-primer PCR assay.

Control of multiply resistant cocci: do international comparisons help?

Antibiotic resistance has become a worldwide problem. However, the reasons for the uneven geographic distribution of antibiotic-resistant microorganisms are not fully understood. For instance, there are striking differences in the epidemiology of multiresistant gram-positive cocci between the USA and Germany. According to recent reports, the prevalence of high-level penicillin-resistant pneumococci (PRP), meticillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant enterococci (VRE) in clinically relevant isolates of hospitalised patients in the USA and Germany are: PRP, 14% versus less than 1%; MRSA, 36% versus 15%; and VRE, 15% versus 1%. These disparities may be explained by several determinants: (1) diagnostic practice and laboratory recognition (all three pathogens); (2) clonal differences and pathogen transmissibility (VRE); (3) antibiotic prescribing practices (all three pathogens); (4) population characteristics, including extensive daycare exposure in the USA (PRP); (5) cultural factors (all three pathogens); (6) factors related to the health-care and legal system (all three pathogens); and (7) infection-control practices (MRSA and VRE). Understanding these determinants is important for preventing further spread of multiresistant cocci within the USA. A rational approach to national surveillance is urgently needed in Germany to preserve the favourable situation and decrease MRSA transmission. Finally, we suggest that a macro-level perspective on antibiotic resistance can broaden the understanding of this worldwide calamity, and help prevent further dissemination of multiply resistant microorganisms.

Antimicrobial use and the emergence of antimicrobial resistance with Streptococcus pneumoniae in the United States

The rapid emergence of resistance to antimicrobial agents by Streptococcus pneumoniae in the United States has been influenced by various factors, including the clonal nature of most resistant strains and the fact that organisms with a multiresistant phenotype have become stably endemic. The ease with which transmission occurs and the fact that humans, especially children, are often colonized asymptomatically in the upper respiratory tract have contributed to the problem. Clearly, the most important factor in the emergence of antimicrobial resistance with S. pneumoniae, however, is the selective pressure of antimicrobial agents. Potency, defined as a product of both antibacterial effect and drug delivery, is a key factor. Generally speaking, the more potent an antimicrobial agent, the less likely it is to select for resistance. This is germane to comparisons of oral agents within specific antimicrobial classes (e.g., beta-lactams, macrolides, and fluoroquinolones). Within each class, potencies differ. In view of the existence of stably endemic multidrug-resistant S. pneumoniae, given comparable cost, side-effect profile, palatability, convenience of dosing, and accessibility, use of the most potent agent(s) within a particular class is advocated.

The rise and fall of antimicrobial resistance

Antimicrobial resistance is a growing problem in nearly every infectious disease, but the extent and rate of increase of the problem varies widely with different pathogen-drug combinations. The rate of increase of resistance depends primarily on the availability of resistant variants and the intensity of selection imposed by antimicrobial treatment (appropriately measured). Declines in resistance following antimicrobial control measures are typically faster in hospital-acquired infections than in community-acquired ones, probably owing to the dependence in the latter case on the fitness cost of resistance. Open questions and approaches for testing the hypotheses proposed here are outlined.