Marked differences in pneumococcal carriage and resistance patterns between day care centers located within a small area

Geographic variation in pneumococcal vaccine efficacy estimated from dynamic modeling of epidemiological data post-PCV7

Although mean efficacy of multivalent pneumococcus vaccines has been intensively studied, variance in vaccine efficacy (VE) has been overlooked. Different net individual protection across settings can be driven by environmental conditions, local serotype and clonal composition, as well as by socio-demographic and genetic host factors. Understanding efficacy variation has implications for population-level effectiveness and other eco-evolutionary feedbacks. Here I show that realized VE can vary across epidemiological settings, by applying a multi-site-one-model approach to data post-vaccination. I analyse serotype prevalence dynamics following PCV7, in asymptomatic carriage in children attending day care in Portugal, Norway, France, Greece, Hungary and Hong-Kong. Model fitting to each dataset provides site-specific estimates for vaccine efficacy against acquisition, and pneumococcal transmission parameters. According to this model, variable serotype replacement across sites can be explained through variable PCV7 efficacy, ranging from 40% in Norway to 10% in Hong-Kong. While the details of how this effect is achieved remain to be determined, here I report three factors negatively associated with the VE readout, including initial prevalence of serotype 19F, daily mean temperature, and the Gini index. The study warrants more attention on local modulators of vaccine performance and calls for predictive frameworks within and across populations.

Genetic similarity between adenoid tissue and middle ear fluid isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis from Iranian children with otitis media with effusion

BACKGROUND

Otitis media with effusion (OME) is a common disease among children, in the pathogenesis of which bacterial infections play a critical role. It was suggested that adenoid tissue could serve as a reservoir for bacterial infection, the eustachian tubes being the migration routes of bacteria into the middle ear cavity. The aim of this study was to investigate the genetic similarity between isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, obtained from adenoid tissue and middle ear fluid.

METHODS

A total of 60 specimens of middle ear fluids (MEFs) and 45 specimens of adenoid tissue were obtained from 45 children with OME. All the samples were inoculated on culture media for bacterial isolation and identification. The genetic similarity between bacterial isolates was determined by pulsed-field gel electrophoresis (PFGE).

RESULTS

The same bacterial species were simultaneously isolated from adenoid tissue and MEFs of 14 patients, among which, 6 pairs of M. catarrhalis, 5 pairs of S. pneumoniae and 3 pairs of H. influenzae were identified.

CONCLUSIONS

Based on the genetic similarities between isolate pairs, found by PFGE analysis, this study suggested that M. catarrhalis, S. pneumoniae and H. influenzae colonize the adenoid tissue, then migrate to the middle ear cavity and, hence, contribute to the total pathogenesis of OME.

Risk of invasive pneumococcal disease varies by neighbourhood characteristics: implications for prevention policies

This study investigates neighbourhood variation in rates of pneumococcal bacteraemia and community-level factors associated with neighbourhood heterogeneity in disease risk. We analysed data from 1416 adult and paediatric cases of pneumococcal bacteraemia collected during 2005-2008 from a population-based hospital surveillance network in metropolitan Philadelphia. Cases were geocoded using residential address to measure disease incidence by neighbourhood and identify potential neighbourhood-level risk factors. Overall incidence of pneumococcal bacteraemia was 36∙8 cases/100,000 population and varied significantly (0-67∙8 cases/100,000 population) in 281 neighbourhoods. Increased disease incidence was associated with higher population density [incidence rate ratio (IRR) 1∙10/10,000 people per mile², 95% confidence interval (CI) 1∙0-1∙19], higher percent black population (per 10% increase) (IRR 1∙07, 95% CI 1∙04-1∙09), population aged ≤5 years (IRR 3∙49, CI 1∙8-5∙18) and population aged ≥65 years (IRR 1∙19, CI 1∙00-1∙38). After adjusting for these characteristics, there was no significant difference in neighbourhood disease rates. This study demonstrates substantial small-area variation in pneumococcal bacteraemia risk that appears to be explained by neighbourhood sociodemographic characteristics. Identifying neighbourhoods with increased disease risk may provide valuable information to optimize implementation of prevention strategies.

Dynamics of pneumococcal acquisition and carriage in young adults during training in confined settings in Israel

BACKGROUND

Outbreaks and sporadic cases of pneumococcal illness occur among young adults in confined settings. Our aim was to characterize pneumococcal acquisition and carriage among healthy young adults in Israel during military training in confined settings.

METHODS

During the years 2007-2008, an observational longitudinal study was conducted in three cohorts of healthy soldiers, during a 7-month basic training period. Epidemiological data, oropharyngeal and nasopharyngeal cultures were sampled on 5 occasions: before and 3, 6, 12 and 24 weeks after start of training. Samples were processed within 2-18 hours. Relatedness of isolates was investigated by capsular typing of all isolates and pulsed-field gel electrophoresis to determine acquisition and transmission. Carriage and acquisition patterns were analyzed and multivariable logistic regression analysis was performed to assess the impact of time on acquisition after mixing, controlling for other covariates.

RESULTS

Pneumococci were recovered on 202 of 1872 visits among 742 individuals, including 40 different serotypes. Mean carriage prevalence increased in all visits following training initiation. Acquisition during training was high, as 36.9% of individuals acquired pneumococci at least once during training, and for almost one fourth of the whole population this occurred during the first 6 weeks. Significant clustering was noted. Sharing drinking glass/bottle was found to be a significant and common risk factor for pneumococcal acquisition.

CONCLUSIONS

Pneumococcal acquisition is highly frequent when young adults live in close contact in confined settings, especially early after mixing.

Characteristics of Streptococcus pneumoniae strains colonizing upper respiratory tract of healthy preschool children in Poland

Antibiotic resistant and invasive pneumococci may spread temporally and locally in day care centers (DCCs). We examined 267 children attending four DCCs located in the same city and 70 children staying at home in three seasons (autumn, winter, and spring) to determine prevalence, serotype distribution, antibiotic resistance patterns, and transmission of pneumococcal strains colonizing upper respiratory tract of healthy children without antipneumococcal vaccination. By pheno- and genotyping, we determined clonality of pneumococci, including drug-resistant strains. The average carriage of pneumococci in three seasons was 38.2%. 73.4% and 80.4% of the isolates belonged to serotypes present in 10- and 13-valent conjugate vaccine, respectively. Among the pneumococcal strains, 33.3% were susceptible to all antimicrobial tested and 39.2% had decreased susceptibility to penicillin. Multidrug resistance was common (35.7%); 97.5% of drug-resistant isolates represented serotypes included to 10- and 13-valent conjugate vaccine. According to BOX-PCR, clonality definitely was observed only in case of serotype 14. Multivariate analysis determined DCC attendance as strongly related to pneumococcal colonization in all three seasons, but important seasonal differences were demonstrated. In children attending DCCs, we observed dynamic turnover of pneumococcal strains, especially penicillin nonsusceptible and multidrug resistant, which were mostly distributed among serotypes included to available pneumococcal conjugate vaccines.

Niche and neutral effects of acquired immunity permit coexistence of pneumococcal serotypes

Over 90 capsular serotypes of Streptococcus pneumoniae, a common nasopharyngeal colonizer and major cause of pneumonia, bacteremia, and meningitis, are known. It is unclear why some serotypes can persist at all: They are more easily cleared from carriage and compete poorly in vivo. Serotype-specific immune responses, which could promote diversity in principle, are weak enough to allow repeated colonizations by the same type. We show that weak serotype-specific immunity and an acquired response not specific to the capsule can together reproduce observed diversity. Serotype-specific immunity stabilizes competition, and acquired immunity to noncapsular antigens reduces fitness differences. Our model can be used to explain the effects of pneumococcal vaccination and indicates general factors that regulate the diversity of pathogens.

The Streptococcus pneumoniae pilus-1 displays a biphasic expression pattern

The Streptococcus pneumoniae pilus-1 is encoded by pilus islet 1 (PI-1), which has three clonal variants (clade I, II and III) and is present in about 30% of clinical pneumococcal isolates. In vitro and in vivo assays have demonstrated that pilus-1 is involved in attachment to epithelial cells and virulence, as well as protection in mouse models of infection. Several reports suggest that pilus-1 expression is tightly regulated and involves the interplay of numerous genetic regulators, including the PI-1 positive regulator RlrA. In this report we provide evidence that pilus expression, when analyzed at the single-cell level in PI-1 positive strains, is biphasic. In fact, the strains present two phenotypically different sub-populations of bacteria, one that expresses the pilus, while the other does not. The proportions of these two phenotypes are variable among the strains tested and are not influenced by genotype, serotype, growth conditions, colony morphology or by the presence of antibodies directed toward the pilus components. Two sub-populations, enriched in pilus expressing or not expressing bacteria were obtained by means of colony selection and immuno-detection methods for five strains. PI-1 sequencing in the two sub-populations revealed the absence of mutations, thus indicating that the biphasic expression observed is not due to a genetic modification within PI-1. Microarray expression profile and western blot analyses on whole bacterial lysates performed comparing the two enriched sub-populations, revealed that pilus expression is regulated at the transcriptional level (on/off regulation), and that there are no other genes, in addition to those encoded by PI-1, concurrently regulated across the strains tested. Finally, we provide evidence that the over-expression of the RrlA positive regulator is sufficient to induce pilus expression in pilus-1 negative bacteria. Overall, the data presented here suggest that the observed biphasic pilus expression phenotype could be an example of bistability in pneumococcus.

The impact of the pneumococcal conjugate vaccine on antimicrobial resistance in the United States since 1996: evidence for a significant rebound by 2007 in many classes of antibiotics

BACKGROUND

The impact of the introduction of the pneumococcal conjugate vaccine over antimicrobial resistance has not been well established. The present study models the changes in resistance over time for all major classes of antibiotics.

METHODS

Susceptibility data on a total of 129,652 isolates from The Surveillance Network surveillance database during the period 1996-2007 were available for analysis, as well as age, specimen source, inpatient or outpatient location, and census region. Cubic splines in a logistic regression mixed model were used to model changes of the resistance rates over time in the United States, taking into account risk factors, so that separate adjusted curves were modeled for each antibiotic.

RESULTS

Yearly resistance prevalence to most antibiotics had been increasing in the period 1996-2001. Adjusted prevalence rates in a multivariate model declined in the period 2001-2004 for penicillin, erythromycin, amoxicillin/clavulanate, trimethoprim/sulfamethoxazole, tetracycline, ceftriaxone, and multidrug. These same antibiotics showed a significant rebound for the period 2004-2007, with the largest overall increase for erythromycin, followed by amoxicillin/clavulanate, tetracycline, multidrug, penicillin, trimethoprim/sulfamethoxazole, and ceftriaxone. Changes in both decline and rebound were more marked for children <5 years old and for otitis media isolates.

CONCLUSION

The indirect effect of the pneumococcal conjugate vaccine introduction on yearly resistance prevalence for several antibacterials as well as for multidrug resistance is one of blunting of a prior sustained increase, with a significant but short-lived decrease in resistance rates, and a significant rebound in adjusted rates for the period 2004-2007.

Maternal antibodies to pneumolysin but not to pneumococcal surface protein A delay early pneumococcal carriage in high-risk Papua New Guinean infants

Immunization of pregnant women can be an efficient strategy to induce early protection in infants in developing countries. Pneumococcal protein-based vaccines may have the capacity to induce pneumococcal serotype-independent protection. To understand the potential of maternal pneumococcal protein-specific antibodies in infants in high-risk areas, we studied the placental transfer of naturally acquired antibodies to pneumolysin (Ply) and pneumococcal surface protein A family 1 and 2 (PspA1 and PspA2) in relation to onset of pneumococcal nasopharyngeal carriage in infants in Papua New Guinea (PNG). In this study, 76% of the infants carried Streptococcus pneumoniae in the upper respiratory tract within the first month of life, at a median age of 19 days. Maternal and cord blood antibody titers to Ply (rho = 0.824, P < 0.001), PspA1 (rho = 0.746, P < 0.001), and PspA2 (rho = 0.631, P < 0.001) were strongly correlated. Maternal pneumococcal carriage (hazard ratio [HR], 2.60; 95% confidence interval [CI], 1.25 to 5.39) and younger maternal age (HR, 0.74; 95% CI, 0.54 to 1.00) were independent risk factors for early carriage, while higher cord Ply-specific antibody titers predicted a significantly delayed onset (HR, 0.71; 95% CI, 0.52 to 1.00) and cord PspA1-specific antibodies a significantly younger onset of carriage in PNG infants (HR, 1.57; 95% CI, 1.03 to 2.40). Maternal vaccination with a pneumococcal protein-based vaccine should be considered as a strategy to protect high-risk infants against pneumococcal disease by reducing carriage risks in both mothers and infants.

Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland - implications for elimination of transmission

Background

Day care centre (DCC) attendees play a central role in maintaining the circulation of Streptococcus pneumoniae (pneumococcus) in the population. Exposure within families and within DCCs are the main risk factors for colonisation with pneumococcal serotypes in DCC attendees.

Methods

Transmission of serotype specific carriage was analysed with a continuous time event history model, based on longitudinal data from day care attendees and their family members. Rates of acquisition, conditional on exposure, were estimated in a Bayesian framework utilising latent processes of carriage. To ensure a correct level of exposure, non-participating day care attendees and their family members were included in the analysis. Posterior predictive simulations were used to quantify transmission patterns within day care cohorts, to estimate the basic reproduction number for pneumococcal carriage in a population of day care cohorts, and to assess the critical vaccine efficacy against carriage to eliminate pneumococcal transmission.

Results

The model, validated by posterior predictive sampling, was successful in capturing the strong temporal clustering of pneumococcal serotypes in the day care cohorts. In average 2.7 new outbreaks of pneumococcal carriage initiate in a day care cohort each month. While 39% of outbreaks were of size one, the mean outbreak size was 7.6 individuals and the mean length of an outbreak was 2.8 months. The role of families in creating and maintaining transmission was minimal, as only 10% of acquisitions in day care attendees were from family members. Considering a population of day care cohorts, a child-to-child basic reproduction number was estimated as 1.4 and the critical vaccine efficacy against acquisition of carriage as 0.3.

Conclusion

Pneumococcal transmission occurs in serotype specific outbreaks of carriage, driven by within-day-care transmission and between-serotype competition. An amplifying effect of the day care cohorts enhances the spread of pneumococcal serotypes within the population. The effect of vaccination, in addition to reducing susceptibility to pneumococcal carriage in the vaccinated, induces a herd effect, thus creating a counter-effect to the amplifying effect of the cohort. Consequently, the critical vaccine efficacy against carriage, required for elimination of transmission, is relatively low. Use of pneumococcal conjugate vaccines is expected to induce a notable herd protection against pneumococcal disease.

Acute otitis media in children: association with day care centers--antibacterial resistance, treatment, and prevention

Children attending day care centers (DCCs) frequently carry antibacterial-resistant organisms in their nasopharynx, leading to acute otitis media (AOM) that may be refractory to antibacterial treatment. The development and spread of resistant organisms are facilitated in DCCs as a result of the following: (i) large numbers of children; (ii) frequent close person-to-person contact; and (iii) a wide use of antimicrobial medications. Intensive antimicrobial usage provides the selection pressure that favors the emergence of resistant organisms, while DCCs provide an ideal environment for transmission of these organisms. The American Academy of Pediatrics and American Academy of Family Physicians' guidelines recommend high-dose amoxicillin/clavulanic acid (rather than amoxicillin alone) as the first therapeutic choice in the treatment of AOM in children attending DCCs. The introduction of the 7-valent pneumococcal conjugated vaccine (PCV7) had a major role in decreasing the number of episodes of Streptococccus pneumoniae AOM secondary to the serotypes included in the vaccine. It also had a major role in reducing the nasopharyngeal carriage of vaccine-type S. pneumoniae (and in particular of antibacterial-resistant organisms), preventing, in this way, its spread to contacts in the community. However, the recent observation of increased rates of antibacterial-resistant non-vaccine serotype S. pneumoniae may erode the success of PCV7.

Assessment of molecular typing methods to determine invasiveness and to differentiate clones of Streptococcus pneumoniae

In the United States, Streptococcus pneumoniae is the leading cause of community-acquired pneumonia and invasive bacterial disease. As antimicrobial resistance increases, it will become critical to determine if strains circulating in a population are likely to cause invasive pneumococcal disease (IPD). This is possible by comparison of an isolate's genotype to strains known to be invasive. In this work, we compared pulse-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST), comparative genomic hybridization (CGH) and multi-invasive-locus sequence typing (MILST) for their ability to distinguish between known IPD causing and carrier strains using phylogenetic analyses. In addition, we assess the ability of these techniques to determine true clones from highly related strains. The resulting trees suggest that despite similar overall topologies, the clearest picture of invasiveness and genetic relatedness can be viewed when typing methods are used collectively.

Antibiotic susceptibility, serotype distribution and vaccine coverage of nasopharyngeal and oropharyngeal Streptococcus pneumoniae in a day-care centre in St. Petersburg, Russia

The objectives were to study serotypes and antibiotic susceptibility of Streptococcus pneumoniae carried by healthy children attending a day-care centre in St. Petersburg. S. pneumoniae colonization was investigated in 125 children aged 16-70 months. Antibiotic susceptibility was determined by E-test and disk diffusion. 83 S. pneumoniae cases were isolated in 75/125 (60%) children: 36/75 (48%) in the nasopharynx, 12/75 (16%) in the oropharynx and 27/75 (36%) in both. Carriage rates were 100%, 68%, 72%, 46% and 54% in children aged 12-23, 24-35, 36-47, 48-59 and >or=60 months, respectively. 97.6% of isolates were susceptible to penicillin. 61.4%, 32.5%, 19.3%, 16.7% and 6% isolates were non-susceptible to trimethoprim/sulfamethoxazole, tetracycline, clindamycin, erythromycin and chloramphenicol, respectively. 20.5% of isolates were multidrug resistant (MDR). 45% of isolates were of serotypes included in the 7-valent pneumococcal conjugate vaccine (7V-PCV); 64.9%, 56.8%, 32.4% and 27% of 7V-PCV serotypes were resistant to trimethoprim/sulfamethoxazole, tetracycline, clindamycin and erythromycin, respectively. The respective figures for MDR isolates were 100%, 94.1%, 70.6% and 76.5%; 76.5% of all MDR isolates were covered by 7V-PCV.

IN CONCLUSION

1) resistance to trimethoprim/sulfamethoxazole and tetracycline was high; 2) resistance to macrolides was higher than in other Russian regions; 3) 7V-PCV coverage was modest, but the vaccine may potentially reduce MDR-S. pneumoniae.

Characterization of Streptococcus pneumoniae isolated from children with otitis media

Streptococcus pneumoniae is the main causative agent of acute otitis media in children. Serotype-based vaccines have provided some protection against otitis media, but not as much as anticipated, demonstrating the need for alternative vaccine options. Pneumococcal otitis media isolates were obtained from children 5 years old or younger from hospitals around Mississippi in the prevaccine era (1999-2000). These isolates were compared by capsular typing, pneumococcal surface protein A (PspA) family typing, antibiotic susceptibility, and DNA fingerprinting. Our study shows that there is great genetic variability among pneumococcal clinical isolates of otitis media, except with regard to PspA. Therefore, efforts focused on the development of a PspA-based pneumococcal vaccine would be well placed.

Dynamics of pneumococcal carriage among healthy Icelandic children attending day-care centres

Invasive pneumococcal disease and antimicrobial (AM) resistance in pneumococci are important public health concerns. With the advent of new pneumococcal vaccines, information on serotype prevalence and their temporal fluctuations is important. Information on AM use and consent for participation was obtained by a questionnaire to parents of children at 5 day-care centres in Reykjavik from 1992 to 1999, and nasopharyngeal swabs were cultured selectively for pneumococci. The pneumococci were serotyped and pulsed field gel electrophoresis used to determine clonality. Of 1228 nasopharyngeal swabs, 640 (52.1%) yielded pneumococci of which 89 (13.9%) had decreased susceptibility to penicillin and 1 was resistant. Children receiving AMs during the month preceding nasopharyngeal sampling and children attending a day-care centre where AM use was high were significantly more likely to carry penicillin non-susceptible isolates. Serotypes 6A, 6B and 23F were most common (48%), and 74% of serotyped isolates belonged to 1 of the 7 most common serotypes. Almost all penicillin non-susceptible isolates were of serotype 6B or 19A. Serotype prevalence fluctuated markedly between y. In conclusion, there was significant variation in serotype prevalence between y, and only 51% of the pneumococci belonged to serotypes covered by the current 7-valent conjugated vaccine.

Clinical and bacterial characteristics of acute bacterial conjunctivitis in children in the antibiotic resistance era

BACKGROUND

Acute conjunctivitis is the most common eye disorder in young children. Bacteria are responsible for 54-73% of all cases. The goals of the study were to identify the rates of Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis in cases of bacterial conjunctivitis in children and to define antibiotic resistance rates.

METHODS

During a 2-year study period, conjunctival swabs of children 2-36 months old were collected prospectively. Nontypable H. influenzae, S. pneumoniae and M. catarrhalis were defined as the study pathogens. Analyzed variables included demography, clinical presentation, bacteriologic results and susceptibility patterns.

RESULTS

There were 428 patients enrolled. Of all cultures, 55% (237 of 428) yielded at least 1 of the study pathogens. H. influenzae and S. pneumoniae were isolated from 29 and 20% of cultures, respectively. beta-Lactamase production was found in 29% of H. influenzae isolates, and penicillin nonsusceptibility was observed in 60% of S. pneumoniae isolates. The most common S. pneumoniae serotypes were: 19F (14%); 6A and 14 (11% each). Nontypable S. pneumoniae was found in 12%. The 7-valent pneumococcal conjugate vaccine (PCV-7) could potentially cover 44% of all isolates. Conjunctivitis-otitis syndrome was found in 32% of patients, of whom 82% of cultures yielded H. influenzae.

CONCLUSIONS

Antibiotic resistance rates are alarmingly high. Conjunctivitis-otitis syndrome, predominantly caused by H. influenzae, is quite common. The potential coverage of the PCV-7 in conjunctivitis is relatively lower than that reported in other pneumococcal infections. Our findings should alert physicians on the choice of appropriate antibiotic treatment, on the frequent copresence of acute otitis media and on the potential role of conjunctivitis in the spread of antibiotic-resistant pathogens.

Genetic relatedness between pneumococcal populations originating from the nasopharynx, adenoid, and tympanic cavity of children with otitis media

Previous studies have shown that Streptococcus pneumoniae exists in both middle ear effusions and the upper respiratory region from children with otitis media with effusion (OME), but it remains unclear whether these strains represent genetically identical clones. Therefore, it cannot be determined whether these bacteria originate from a common source. To determine the presence of pneumococci at different anatomical locations of OME patients, conventional culture and PCR techniques were used. To analyze the possible genetic relatedness between pneumococci from different anatomical sites, molecular typing by amplified fragment length polymorphism was utilized. The percentage of middle ear effusions of OME patients that are positive for pneumococci after PCR analysis (13%) was higher than after conventional culture (5%). Molecular fingerprints from pneumococci derived from two different anatomic sites within patients were very similar in 80% of OME patients and in 90% of acute otitis medium patients, indicating their genetic relatedness. Biofilm formation or pneumococcal L-forms probably play a role in OME, since culture-negative effusions prove to contain pneumococcal DNA. Bacteria involved in this process most likely originate from the nasopharynx since they show a close genetic relatedness with their nasopharyngeal counterparts.

Trends in drug resistance, serotypes, and molecular types of Streptococcus pneumoniae colonizing preschool-age children attending day care centers in Lisbon, Portugal: a summary of 4 years of annual surveillance

Of the nasopharyngeal cultures recovered from 942 day care center (DCC) attendees in Lisbon, Portugal, 591 (62%) yielded Streptococcus pneumoniae during a surveillance performed in February and March of 1999. Forty percent of the isolates were resistant to one or more antimicrobial agents. In particular, 2% were penicillin resistant and 20% had intermediate penicillin resistance. Multidrug resistance to macrolides, lincosamides, and tetracycline was the most frequent antibiotype (17% of all isolates). Serotyping and molecular typing by pulsed-field gel electrophoresis were performed for 202 out of 237 drug-resistant pneumococci (DRPn). The most frequent serotypes were 6B (26%), 14 (22%), 19F (16%), 23F (10%), and nontypeable (12%). The majority (67%) of the DRPn strains were representatives of nine international clones included in the Pneumococcal Molecular Epidemiology Network; eight of them had been detected in previous studies. Fourteen novel clones were identified, corresponding to 26% of the DRPn strains. The remaining 7% of the strains were local clones detected in our previous studies. Comparison with studies conducted since 1996 in Portuguese DCCs identified several trends: (i) the rate of DRPn frequency has fluctuated between 40 and 50%; (ii) the serotypes most frequently recovered have remained the same; (iii) nontypeable strains appear to be increasing in frequency; and (iv) a clone of serotype 33F emerged in 1999. Together, our observations highlight that the nasopharynxes of children in DCCs are a melting pot of successful DRPn clones that are important to study and monitor if we aim to gain a better understanding on the epidemiology of this pathogen.

Streptococcus pneumoniae colonisation: the key to pneumococcal disease

Streptococcus pneumoniae is an important pathogen causing invasive diseases such as sepsis, meningitis, and pneumonia. The burden of disease is highest in the youngest and oldest sections of the population in both more and less developed countries. The treatment of pneumococcal infections is complicated by the worldwide emergence in pneumococci of resistance to penicillin and other antibiotics. Pneumococcal disease is preceded by asymptomatic colonisation, which is especially high in children. The current seven-valent conjugate vaccine is highly effective against invasive disease caused by the vaccine-type strains. However, vaccine coverage is limited, and replacement by non-vaccine serotypes resulting in disease is a serious threat for the near future. Therefore, the search for new vaccine candidates that elicit protection against a broader range of pneumococcal strains is important. Several surface-associated protein vaccines are currently under investigation. Another important issue is whether the aim should be to prevent pneumococcal disease by eradication of nasopharyngeal colonisation, or to prevent bacterial invasion leaving colonisation relatively unaffected and hence preventing the occurrence of replacement colonisation and disease. To illustrate the importance of pneumococcal colonisation in relation to pneumococcal disease and prevention of disease, we discuss the mechanism and epidemiology of colonisation, the complexity of relations within and between species, and the consequences of the different preventive strategies for pneumococcal colonisation.

Macrolide resistance: an increasing concern for treatment failure in children

BACKGROUND

Antimicrobial treatment of pediatric respiratory tract infections has evolved during the past 30 years as a result of antimicrobial resistance. The focus of antimicrobial therapy in these conditions has shifted from penicillins to other agents because of the dramatic increase in antimicrobial resistance among common respiratory pathogens, including Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. It is important for clinicians to understand how resistance develops so that they can help prevent this phenomenon from occurring with other antimicrobials.

METHODS

This article reviews the published literature on resistance to macrolide antimicrobials among common pediatric respiratory tract pathogens and clinical and bacteriologic outcomes of infections with these pathogens.

RESULTS

Resistance among common pediatric respiratory tract pathogens to macrolides occurs through two main mechanisms, alteration of the target site and active efflux. Although resistance patterns vary by geographic region, the widespread use of macrolides has contributed to the emergence of both types of macrolide-resistant organisms. Conditions that favor the selection and proliferation of resistant strains include children with repeated, close contact who frequently receive antimicrobial treatment or prophylaxis, such as children who attend day care. Recent US surveillance data show that 20 to 30% of S. pneumoniae are resistant to macrolides, with approximately two-thirds of macrolide-resistant strains associated with an efflux mechanism and the remainder associated with a ribosomal methylase. Additionally, although less well-known, virtually all strains of H. influenzae have an intrinsic macrolide efflux pump. As resistance to macrolides has increased, clinical failures have resulted, and these agents are no longer considered appropriate for empiric first line antimicrobial therapy of acute otitis media and sinusitis unless patients are truly penicillin-allergic. Therefore, other antimicrobials are recommended for the empiric treatment of children with respiratory tract infections, including higher doses of amoxicillin and amoxicillin/clavulanate (90 mg/kg/day amoxicillin), cefuroxime axetil and intramuscular ceftriaxone.

CONCLUSIONS

As resistance to macrolides increases and clinical failures in children become more common with this class of antimicrobials, judicious use of antimicrobials is needed. This includes limiting antimicrobial use for viral infections and using the most effective agents when antimicrobials are clinically indicated, such as higher doses of amoxicillin and amoxicillin/clavulanate. Application of these principles may prevent proliferation and further development of resistance.

Worldwide trends in antimicrobial resistance among common respiratory tract pathogens in children

BACKGROUND

Respiratory tract infections among children are a common reason for health care provider visits and the primary reason for antimicrobial prescribing in this population. The increased prevalence of resistance among Streptococcus pneumoniae and Haemophilus influenzae pathogens poses a serious challenge in the successful treatment of respiratory tract infections caused by these pathogens.

METHODS

This paper reviews worldwide trends in antimicrobial resistance among common respiratory tract pathogens, highlighting data obtained from the pediatric population where available.

RESULTS

S. pneumoniae resistance to beta-lactams is mediated through alterations in the penicillin-binding proteins and macrolide resistance to acquisition of efflux or methylation genes. The mechanisms of resistance to the fluoroquinolones include target enzyme alterations via genetic mutations and transport out of the bacterial cell via an efflux pump. Beta-lactamase production is the primary mechanism of resistance to penicillins among H. influenzae isolates. Although S. pneumoniae with reduced susceptibility to penicillin was first documented > 30 years ago, resistance has increased at an alarming rate worldwide in the past decade. According to recent surveillance data, the worldwide prevalence of S. pneumoniae with reduced susceptibility to penicillin is 18.2%. Beta-lactamase production among H. influenzae ranges from approximately 4% in Russia to 26% in the United States and to 31% in France. The prevalence of beta-lactamase-negative, ampicillin-resistant H. influenzae remains very low (< 1%) worldwide, except in Japan, where the incidence is higher. In general, the highest rates of resistance are observed in isolates obtained from children, and risk factors for infection with a resistant pathogen include young age, the site of infection, day-care center attendance and recent antimicrobial use.

CONCLUSIONS

Increased prevalence of antimicrobial resistance among respiratory tract pathogens isolated from children and adults is evident worldwide. Treatment of infections caused by S. pneumoniae and H. influenzae with older agents or ineffective dosing regimens may not eradicate infections and may contribute to the spread of resistance. These observations confirm the need for appropriate antimicrobial use to halt or at least limit the spread of resistance.

Antibacterial cleaning and hygiene products as an emerging risk factor for antibiotic resistance in the community

Antibiotic resistance within the community setting is an emerging public-health concern. Infection with antibiotic-resistant organisms in the community among people lacking traditional risk factors has been reported. In addition, prevalence studies have identified individuals carrying antibiotic-resistant organisms in the absence of known risk factors. These studies strongly suggest the presence of contributing factors that have yet to be identified. In this paper we review the burden of antibiotic resistance and known risk factors within the community setting, assess the potential role of antibacterial cleaning and hygiene products containing triclosan in the emergence of resistance, and recommend future research on the assessment of household cleaning and hygiene products containing triclosan.

Vaccination of day-care center attendees reduces carriage of Streptococcus pneumoniae among their younger siblings

AIM

We conducted a study to determine whether administration of a pneumococcal conjugate vaccine to toddlers attending day-care centers (DCCs) could prevent acquisition of Streptococcus pneumoniae of the vaccine serotypes (VT) by their younger siblings.

METHODS

In a double blind study, 262 DCC attendees ages 12 to 35 months were randomized to receive a 9-valent pneumococcal conjugate vaccine (PnCRM9; n = 132), or a control vaccine (meningococcus C vaccine; n = 130). It was planned to follow the groups for 2 years with monthly nasopharyngeal pneumococcal cultures during the first follow-up year and every 2 months during the second year. Forty-six younger siblings of the above described children, age <18 months (23 siblings of the PnCRM9 recipients and 23 of the controls), were also enrolled, and nasopharyngeal cultures were obtained monthly until the children reached the age of 18 months or started to attend DCC, if before the age of 18 months. Pneumococcal isolates were serotyped and tested for antibiotic susceptibility.

RESULTS

Of the 3748 cultures obtained from the DCC attendees, 2450 (65%) were positive for S. pneumoniae. Of 306 cultures obtained from the younger siblings, 151 (49%) were positive. Among the PnCRM9 recipients, cultures were significantly less frequently positive for the VT S. pneumoniae than among the controls (13% vs. 21%, respectively; P < 0.001). The same pattern was seen in the younger siblings of PnCRM9 recipients vs. the siblings of controls (21% vs. 34%, respectively; P = 0.017). The reverse trend was seen for non-VT strains in both the DCC attendees (44% vs. 34%, respectively; P < 0.001) and their younger siblings (19% vs. 13%, respectively; P = 0.15). There was a significant decrease in the carriage rate of antibiotic-resistant S. pneumoniae in both the PnCRM9 recipients and their younger siblings. The relative risks (and 95% confidence intervals) to carry S. pneumoniae penicillin-nonsusceptible, resistant to > or =1, > or =2 and > or =3 antibiotic categories among younger siblings of PnCRM9 recipients vs. siblings of controls were 0.47 (0.31 to 0.70), 0.49 (0.33 to 0.71), 0.46 (0.30 to 0.73) and 0.49 (0.21 to 1.17), respectively. When acquired, VT and antibiotic-resistant S. pneumoniae were carried for a significantly shorter period of time among siblings of PnCRM9 recipients than in siblings of controls.

CONCLUSION

The marked effect of PnCRM9 administration to DCC attendees on carriage of VT and antibiotic-resistant S. pneumoniae among their younger household close contacts demonstrates a herd effect of the vaccine.

Effect of a nonavalent conjugate vaccine on carriage of antibiotic-resistant Streptococcus pneumoniae in day-care centers

BACKGROUND

In the developed societies, day-care centers (DCCs) play an important role in the spread of antibiotic-resistant pneumococci both within the facility and from the facility to the community. This study was conducted to determine the effect of a nonavalent pneumococcal conjugate vaccine (PCV-9) on the carriage of antibiotic-resistant pneumococci in the DCC.

SUBJECTS AND METHODS

Healthy DCC attendees ages 12 to 35 months were randomized to receive either PCV-9 or a control vaccine (conjugate meningococcus C vaccine) in a double blinded manner. Nasopharyngeal Streptococcus pneumoniae cultures were obtained from each subject before vaccination, monthly during the first year of follow-up and every 2 to 3 months during the second year of follow-up. For each isolate the serotype and antibiotic susceptibility were determined.

RESULTS

A total of 132 and 130 evaluable toddlers received either PCV-9 or the control vaccine, respectively. In total 3748 cultures were obtained, of which 2450 (65%) were positive for S. pneumoniae. The resistance rates to penicillin, trimethoprim-sulfamethoxazole and erythromycin were 36, 35 and 16%, respectively. Resistance rates to > or =1 and > or =3 antibiotic categories were 52 and 9%, respectively. Antibiotic resistance was found mainly in the 5 serotypes included in the pneumococcal conjugate vaccines (6B, 9V, 14, 19F and 23F) and in 2 related serotypes (6A and 19A). In the vaccinated group a clear and significant reduction of the carriage rate of the serotypes included in the vaccine and the related serotype 6A as well as an increase in the carriage rate of the serotypes not included in the vaccine were observed. In parallel a significant decrease in carriage rate of antibiotic-resistant pneumococci was observed. The reduction of carriage of antibiotic-resistant pneumococci was seen in all age windows but was greater in the age window <36 months.

CONCLUSIONS

The carriage rate of antibiotic-resistant S. pneumoniae, including multiply resistant S. pneumoniae, in DCC attendees is high. Pneumococcal conjugate vaccines seem to be an important tool for reducing the carriage rate of antibiotic-resistant pneumonia in DCCs.

Recurrent respiratory tract infections in pediatric age: a population-based survey of the therapeutic role of macrolides

In order to evaluate the efficacy of macrolides in pediatric patients with recurrent respiratory tract infections (RRTIs), we enrolled 1,706 children (783 females) aged between 6 months and 14 years (median: 4 years) with an acute respiratory infection and a history of RRTIs (> or = 8 episodes per year if aged < 3 years; > or = 6 episodes per year if aged > or = 3 years). The therapies were chosen by the primary care pediatricians and their effects on respiratory relapses were blindly analyzed. Regardless of age and clinical diagnosis, the children treated with macrolides showed a significantly higher rate of short- and long-term clinical success than those receiving beta-lactams (p<0.0001) or symptomatics alone (p<0.0001). These data show that macrolide therapy of acute respiratory infections influences the natural history of RRTIs, probably because of their elective activity on atypical bacteria. They also suggest the possible importance of these pathogens in causing recurrences of respiratory infections in children and show that the infections they cause may have a more complicated course unless treated with adequate antibacterial drugs.

Bacterial eradication in the treatment of otitis media

Drugs differ in their ability to eradicate various pathogens from the middle-ear cavity during acute otitis media (AOM), and these differences clearly affect clinical outcome. Outcome is derived from differences in the association between concentrations of the drugs at the site of infection and the antimicrobial effect (termed pharmacodynamics). These differences are even more marked in the present era of antimicrobial resistance. However, since AOM is a self-limiting disease in most cases, difference in clinical outcome is more difficult to ascertain than that of bacteriological outcome, which is measured within 3-5 days. A favourable clinical outcome regardless of the bacteriological effect of the drug can result in false optimism when less-effective antibiotic drugs are used. Inappropriate study design and manipulation of clinical results add to this confusion. In this review we attempt to highlight the evidence regarding bacteriological response to antibiotics in AOM and to draw attention to potential flaws that may mislead clinicians.

Pneumococcal vaccination of children

Streptococcus pneumoniae is the most frequent cause of invasive bacterial infection in children younger than 2 years of age, reaching a peak incidence at 6 to 12 months of age. Pneumococci also cause many cases of pneumonia, sinusitis, and otitis media. Incidence rates of invasive infection in children with sickle cell disease, acquired or congenital splenectomy, or human immunodeficiency virus infection are 20- to 100-fold higher than are those of healthy children during the first 5 years of life. Other healthy children, such as those of American Indian, Native Alaskan, or African American descent, also have high rates of invasive infection, and those children enrolled in out-of-home care may have modestly increased risks. Pneumococcal polysaccharide polyvalent vaccines have been available for more than 2 decades but are limited in their usefulness for children because of their inability to induce protective antibody responses in children younger than 2 years of age and lack of immunologic memory. In contrast, pneumococcal protein conjugate vaccines induce presumptive protective responses in infants younger than 6 months, and immunologic memory further enhances responses after booster doses are given. Currently, a single heptavalent pneumococcal protein conjugate vaccine is licensed for use in the United States and is recommended for routine administration to all children, beginning at 2 months of age. It also is recommended for children between 24 and 59 months of age who are at high risk of acquiring invasive disease.

Nasopharyngeal penicillin-resistant Streptococcus pneumoniae strains among young children in Japan

OBJECTIVE

A rapid increase of penicillin resistance in Streptococcus pneumoniae has recently been reported in most areas of the world. Penicillin-resistant S. pneumoniae and other resistant bacteria are the principal causes of recurrent acute otitis media (AOM). Penicillin-resistant S. pneumoniae was examined so that we could investigate the bacteriologic and clinical interpretations of nasopharyngeal flora from healthy children.

METHODS

We obtained nasopharyngeal swab specimens from healthy children attending a day care center and from children attending a public health examination in Kanazawa, Japan. We also obtained clinical specimens from children with AOM who visited the Kanazawa University Hospital and 4 other hospitals in Ishikawa Prefecture in Japan.

RESULTS

The chief bacteria from the children were S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Penicillin-resistant S. pneumoniae was identified in 75% of children attending a day care center. On the other hand, S. pneumoniae was identified in 37% of children who were not attending day care. Of the children with AOM, penicillin-resistant S. pneumoniae was identified in 77%.

CONCLUSION

Our results suggest that there is a strong relationship between day care attendance and nasopharyngeal carriage of S. pneumoniae. The carriage rate of penicillin-resistant S. pneumoniae in healthy children in day care centers was very high and similar to the carriage rate of young patients with AOM in Japan.

Nasopharyngeal carriage of Streptococcus pneumoniae in healthy children: implications for the use of heptavalent pneumococcal conjugate vaccine

We assessed the prevalence of Streptococcus pneumoniae serotypes in the nasopharynx of healthy children, antimicrobial susceptibility patterns, risk factors for carriage, and the coverage of heptavalent pneumococcal conjugate vaccine. In 2,799 healthy infants and children, the S. pneumoniae carrier rate was 8.6% (serotypes 3, 19F, 23F, 19A, 6B, and 14 were most common). Most pneumococci (69.4%) were resistant to one or more antimicrobial classes. The rate of penicillin resistance was low (9.1%); macrolide resistance was high (52.1%). Overall, 63.2% of the isolates belonged to strains covered by the heptavalent pneumococcal vaccine. This percentage was higher in children <2 years old (73.1%) and in those ages 2-5 years (68.9%). Sinusitis in the previous 3 months was the only risk factor for carrier status; acute otitis media was the only risk factor for the carriage of penicillin-resistant S. pneumoniae. Most isolated strains are covered by the heptavalent conjugate vaccine, especially in the first years of life, suggesting that its use could reduce the incidence of pneumococcal disease.

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.

Carriage of penicillin-resistant Streptococcus pneumoniae by children in day-care centers during an intervention program in Malmo, Sweden

BACKGROUND

An increasing incidence of penicillin-resistant Streptococcus pneumoniae (PRP) was detected in Malmo in 1994.

OBJECTIVE

To evaluate clonality and factors facilitating the spread of PRP among children in day-care centers (DCCs).

METHODS

We used phenotypic and DNA-fingerprinting methods in conjunction with epidemiologic data from the South Swedish Pneumococcal Intervention Project's investigation of 63 DCCs during a 3-year period (1995 to 1997) in the Malmo region.

RESULTS

A questionnaire about building and hygiene standards disclosed no statistically significant risk factor for carriage of pneumococci. However, age younger than the mean age at the DCC or in the child group was positively associated with carriage. Contrary to expectations no association with the number of children, either at the DCC or in the individual groups, was found. Of 2912 investigated children 1224 (42%) were carriers of S. pneumoniae, and 373 (12.8%) were PRP carriers (MIC > or = 0.1 microg/ml). Among isolates with MIC > or = 0.5 microg/ml 9 serogroups and 30 genetic types were found. Two clones in serogroups 9 (33%) and 19 (24%) were dominant in most municipality districts, and dominance was sustained during the whole study period. The previously internationally recognized serotype 9V clone seemed to be very stable, with a single DNA type and resistance pattern during the study period. In contrast the serogroup 19 isolates and other serogroups had diverse DNA types and resistance patterns, supporting the hypothesis that DCCs have a unique microenvironment facilitating the recombination of penicillin-binding protein genes among streptococci. In five DCCs we found PRP isolates with two different serogroups but an identical genetic type, indicating that serotype shift may be a common phenomenon in DCCs.

CONCLUSION

Multivariate logistic regression of risk factors disclosed that young age of the children in the child groups was a significant risk factor for carriage of S. pneumoniae.

Pneumococcal conjugate vaccine serotypes of Streptococcus pneumoniae isolates and the antimicrobial susceptibility of such isolates in children with otitis media

The ability of the recently licensed 7-valent pneumococcal conjugate vaccine to cover isolates that cause otitis media, especially drug-resistant ones, was assessed using 500 recently obtained US isolates. Of these isolates, 418 (84%) belonged to vaccine-related serogroups, whereas 82 (16%) belonged to non-vaccine-related serogroups. Serotype 3 accounted for 48 (59%) of the non-vaccine-related serogroups. In addition, 93% of the isolates from patients < or =3 years of age belonged to serotypes that were included in or related to the heptavalent vaccine, compared with 49% of the isolates from older patients (P=.001). Most of the isolates (98%-100%) that were resistant to the antimicrobial agents tested were covered by the heptavalent vaccine, including 95.1% of the isolates from patients <2 years of age. The 7-valent pneumococcal conjugate vaccine could therefore potentially provide protection against all but 1 (type 3) of the common otitis media-associated pneumococcal serogroups identified in this study as well as against 98% of antibiotic-resistant isolates.

Nasopharyngeal carriage of antimicrobial-resistant Streptococcus pneumoniae among young children attending 79 kindergartens and day care centers in Hong Kong

Resistance to penicillin and multiple antimicrobial agents among Streptococcus pneumoniae strains is becoming an increasing problem worldwide and in Asia. To determine the prevalence of carriage of S. pneumoniae isolates not susceptible to penicillin in young children, we obtained nasopharyngeal swab specimens from 1,978 children (ages, 2 to 6 years) attending 79 day care centers or kindergartens. Three hundred eighty-three strains of S. pneumoniae were isolated from these children. Fifty-eight percent of these isolates had reduced susceptibility to penicillin, 123 (32.1%) were intermediate, and 100 (26.1%) were resistant. A very high penicillin MIC (4 microg/ml) was found in 3.3% of the isolates. The isolates also demonstrated high rates of resistance to other antimicrobial agents (51.2% to cefaclor, 50.2% to cefuroxime, 42.8% to cefotaxime, 80.7% to trimethoprim-sulfamethoxazole, 77% to erythromycin, 60% to clindamycin, and 33.7% to chloramphenicol). No isolate was resistant to fluoroquinolone. Multidrug resistance (not susceptible to the beta-lactams and three or more other classes) was found in 39.4% of the isolates. Risk factors for the carriage of S. pneumoniae not susceptible to penicillin were multiple physician visits in the preceding 3 months and use of antimicrobial agents by the individual or by household members in the preceding 3 months. In the logistic regression analysis, only the use of antimicrobial agents in the preceding 3 months was an independent risk factor (P = 0.004; odds ratio, 2; 95% confidence interval, 1.2 to 3.2). This study demonstrated the high prevalence of antibiotic-resistant S. pneumoniae in healthy young children in the community in Hong Kong.

Effect of a conjugate pneumococcal vaccine on the occurrence of respiratory infections and antibiotic use in day-care center attendees

BACKGROUND

Incidence and severity of respiratory infections are increased in day-care center attendees. Streptococcus pneumoniae is an important contributor to these infections.

OBJECTIVE

To examine whether the use of a pneumococcal conjugate vaccine could reduce the occurrence of respiratory infections and the ensuing antibiotic drug use in the day care.

METHOD

In this double blind, randomized, controlled study performed in 8 day-care centers located in Beer-Sheva, Israel, 264 toddlers ages 12 to 35 months at enrollment were randomized to receive either a 9-valent conjugate pneumococcal vaccine (conjugated to CRM197) or a control vaccine [conjugate meningococcus C vaccine (conjugated to CRM197)] and were followed for an average of 22 months. The main outcome measures were respiratory morbidity and antibiotic use.

RESULTS

An overall reduction of 7% in child months with > or = 1 reported illness episodes was observed among vaccinees (P = 0.008), and 85% of all episodes were related to the respiratory tract. Reductions of 15, 16 and 17% were observed in upper respiratory infections, lower respiratory problems and otitis media, respectively. An overall reduction of 17% in antibiotic days was observed [10% for upper respiratory infections, 20% for otitis and 47% for lower respiratory problems (P < or = 0.005 for each entity)]. The reduction in episodes and antibiotic use was greater for those <36 months of age than for the older children.

CONCLUSION

The reduction of respiratory problems, including those not traditionally considered of pneumococcal origin and the ensuing lowered antibiotic use in day-care center attendees by pneumococcal conjugate vaccination suggest a broader benefit from the vaccine than preventing invasive disease only.

Mathematical models as tools for evaluating the effectiveness of interventions: a comment on Levin

Possible interventions to minimize resistance rates are numerous and can involve reduction and/or change in antimicrobial use, infection control, and vaccinations. As mathematical models are becoming more realistic they can be useful to quantitatively evaluate the relative contribution of individual risk factors and for the planning of future intervention strategies. The fitness cost associated with resistance is an important parameter and small differences can have a profound effect on the results. The mathematical models presented for communities predicted that even with cessation of antibiotic use, the decline in resistance frequency would be slow. This contrasts with successful interventions in Finland and Iceland. Future models have to include important variables such as herd immunity and take into account the heterogeneity of open communities. Provision of susceptible strains from areas with low resistance rates to areas with high resistance rates can have a profound effect on the success of interventions to minimize resistance.

A decade (1989-1998) of pediatric invasive pneumococcal disease in 2 populations residing in 1 geographic location: implications for vaccine choice

During 1 decade (1989-1998), data on invasive pneumococcal disease were collected prospectively to assess the burden of disease among Jewish and Bedouin children in southern Israel and the potential reduction in illness that can be achieved by using conjugate vaccines. Data on 513 children <15 years old with bacteriologically proven invasive pneumococcal disease were obtained. Among Jewish and Bedouin children <5 years old, incidence rates were 45 and 139 cases per 100,000 child-years of observation, respectively. Jewish and Bedouin children differed in clinical manifestations, seasonal patterns of disease, serotype distribution, and antibiotic susceptibility rates. The potential coverage by 7-, 9-, and 11-valent conjugate vaccines is 41%, 67%, and 71%, respectively, for Jewish children and 22%, 63%, and 65%, respectively, for Bedouin children. The 9- and 11-valent pneumococcal conjugate vaccines have the potential to substantially decrease invasive pneumococcal disease in southern Israel.

Antibiotic-resistant pneumococci carried by young children do not appear to disseminate to adult members of a closed community

Although antibiotic-resistant pneumococci have been frequently detected among day care center (DCC) attendees, the transmission of these organisms to other members of the community has not been adequately studied. Nasopharyngeal cultures were obtained from 152 children and 244 adult members of a closed community (a kibbutz) in Israel. Serotyping, antibiogram, and pulsed-field gel electrophoresis were performed to determine the relatedness of isolated pneumococci. Twenty (30%) of the 66 isolates from children showed decreased susceptibility to penicillin and 9 isolates (14%) were resistant to > or =3 drugs. Of the 16 isolates from adults, 5 (31%) were intermediately resistant to trimethoprim-sulfamethoxazole. Resistant strains carried by DCC attendees were not isolated either from their parents or from other adult members of the community. Despite the high degree of interpersonal contact occurring in a closed community, resistant pneumococcal strains carried by DCC attendees do not appear to be easily transmitted to the adult population, which suggests the existence of an immunological barrier.

Treatment of acute otitis media - challenges in the era of antibiotic resistance

The last decade is characterized by the increase in antibiotic resistance among respiratory bacterial pathogens in the presence of only modest progress in the development of new antibacterial agents to overcome this resistance. A series of recent studies show clearly that the increased resistance among the main AOM pathogens (namely Streptococcus pneumoniae and Haemophilus influenzae) is associated with a dramatic decrease in bacteriologic response to antibiotic treatment, which in turn has an impact on clinical response. Thus, the individual patient is affected by the increasing antibiotic resistance. Moreover, the society as a whole is now also affected because the carriage and spread of antibiotic resistant AOM pathogens is remarkably impacted by antibiotic treatment. New studies show the remarkable ability of antibiotics to rapidly promote nasopharyngeal carriage and spread of antibiotic-resistant AOM pathogens. In these studies, the increase in carriage of antibiotic resistant S. pneumoniae is shown already after 3-4 days from initiation of antibiotic treatment and may last for weeks to months after treatment. Children carrying antibiotic-resistant organisms transmit those organisms to their family and to their day care centers and thus a vicious cycle is created in which increased antibiotic resistance with decreased response leads to increased antibiotic use, which in turn leads to further increase in resistance. New antibiotics are not likely to improve this situation. It is clear that the challenge in the next decade is to prevent AOM rather than to treat it. Efforts to prevent AOM include improved environmental factors, immunization with bacterial and viral vaccines and some creative measures such as prevention of colonization and attachment to epithelium of AOM pathogens. Whether these efforts will prove successful or, even if successful, will only modify the clinical and bacteriologic picture presenting new challenges, only time will tell.

American Academy of Pediatrics. Committee on Infectious Diseases. Technical report: prevention of pneumococcal infections, including the use of pneumococcal conjugate and polysaccharide vaccines and antibiotic prophylaxis

Pneumococcal infections are the most common invasive bacterial infections in children in the United States. The incidence of invasive pneumococcal infections peaks in children younger than 2 years, reaching rates of 228/100,000 in children 6 to 12 months old. Children with functional or anatomic asplenia (including sickle cell disease [SCD]) and children with human immunodeficiency virus infection have pneumococcal infection rates 20- to 100-fold higher than those of healthy children during the first 5 years of life. Others at high risk of pneumococcal infections include children with congenital immunodeficiency; chronic cardiopulmonary disease; children receiving immunosuppressive chemotherapy; children with immunosuppressive neoplastic diseases; children with chronic renal insufficiency, including nephrotic syndrome; children with diabetes; and children with cerebrospinal fluid leaks. Children of Native American (American Indian and Alaska Native) or African American descent also have higher rates of invasive pneumococcal disease. Outbreaks of pneumococcal infection have occurred with increased frequency in children attending out-of-home care. Among these children, nasopharyngeal colonization rates of 60% have been observed, along with pneumococci resistant to multiple antibiotics. The administration of antibiotics to children involved in outbreaks of pneumococcal disease has had an inconsistent effect on nasopharyngeal carriage. In contrast, continuous penicillin prophylaxis in children younger than 5 years with SCD has been successful in reducing rates of pneumococcal disease by 84%. Pneumococcal polysaccharide vaccines have been recommended since 1985 for children older than 2 years who are at high risk of invasive disease, but these vaccines were not recommended for younger children and infants because of poor antibody response before 2 years of age. In contrast, pneumococcal conjugate vaccines (Prevnar) induce proposed protective antibody responses (>.15 microg/mL) in >90% of infants after 3 doses given at 2, 4, and 6 months of age. After priming doses, significant booster responses (ie, immunologic memory) are apparent when additional doses are given at 12 to 15 months of age. In efficacy trials, infant immunization with Prevnar decreased invasive infections by >93% and consolidative pneumonia by 73%, and it was associated with a 7% decrease in otitis media and a 20% decrease in tympanostomy tube placement. Adverse events after the administration of Prevnar have been limited to areas of local swelling or erythema of 1 to 2 cm and some increase in the incidence of postimmunization fever when it is given with other childhood vaccines. Based on data in phase 3 efficacy and safety trials, the US Food and Drug Administration has provided an indication for the use of Prevnar in children younger than 24 months.