Bacteraemic pneumococcal infections in Southern Sweden 1981-96: trends in incidence, mortality, age-distribution, serogroups and penicillin-resistance

The ratio of single to co-colonization is key to complexity in interacting systems with multiple strains

The high number and diversity of microbial strains circulating in host populations have motivated extensive research on the mechanisms that maintain biodiversity. However, much of this work focuses on strain-specific and cross-immunity interactions. Another less explored mode of pairwise interaction is via altered susceptibilities to co-colonization in hosts already colonized by one strain. Diversity in such interaction coefficients enables strains to create dynamically their niches for growth and persistence, and "engineer" their common environment. How such a network of interactions with others mediates collective coexistence remains puzzling analytically and computationally difficult to simulate. Furthermore, the gradients modulating stability-complexity regimes in such multi-player endemic systems remain poorly understood. In a recent study (Madec & Gjini, Bulletin of Mathematical Biology, 82), we obtained an analytic representation for N-type coexistence in an SIS epidemiological model with co-colonization. We mapped multi-strain dynamics to a replicator equation using timescale separation. Here, we examine what drives coexistence regimes in such co-colonization system. We find the ratio of single to co-colonization, µ, critically determines the type of equilibrium and number of coexisting strains, and encodes a trade-off between overall transmission intensity R 0 and mean interaction coefficient in strain space, k. Preserving a given coexistence regime, under fixed trait variation, requires balancing between higher mean competition in favorable environments, and higher cooperation in harsher environments, and is consistent with the stress gradient hypothesis. Multi-strain coexistence tends to steady-state attractors for small µ, whereas as µ increases, dynamics tend to more complex attractors. Following strain frequencies, evolutionary dynamics in the system also display contrasting patterns with µ, interpolating between multi-stable and fluctuating selection for cooperation and mean invasion fitness, in the two extremes. This co-colonization framework could be applied more generally, to study invariant principles in collective coexistence, and to quantify how critical shifts in community dynamics get potentiated by mean-field and environmental gradients.

Sustained reductions of invasive infectious disease following general infant Haemophilus influenzae type b and pneumococcal vaccination in a Swedish Arctic region

AIM

Vaccine-preventable pathogens causing severe childhood infections include Haemophilus influenzae type b (Hib), Streptococcus pneumoniae and Neisseria meningitidis. In this study conducted in a Swedish Arctic region, we evaluated the effects of general infant Hib and pneumococcal vaccination on invasive infectious diseases among children and assessed the need of meningococcal vaccination.

METHODS

We identified cases of bacterial meningitis and sepsis from diagnosis and laboratory registers in the Västerbotten Region, Sweden, during 1986-2015. We then reviewed medical records to confirm the diagnosis and extract data for assessing incidence changes, using an exploratory data analysis and a time-series analysis.

RESULTS

Invasive Haemophilus disease declined by 89.1% (p < 0.01), Haemophilus meningitis by 95.3% (p < 0.01) and all-cause bacterial meningitis by 82.3% (p < 0.01) in children aged 0 to four years following general infant Hib vaccination. Following pneumococcal vaccination, invasive pneumococcal disease declined by 84.7% (p < 0.01), pneumococcal meningitis by 67.5% (p = 0.16) and all-cause bacterial meningitis by 48.0% (p = 0.23). Incidence of invasive meningococcal disease remained low during the study period.

CONCLUSION

Remarkable sustained long-term declines of invasive infectious diseases in younger children occurred following infant Hib and pneumococcal vaccinations in this Swedish Arctic region. Despite not offering general infant meningococcal vaccination, incidence of invasive meningococcal disease remained low.

Streptococcus pneumoniae bacteremia: clinical and microbiological epidemiology in a health area of Southern Spain

Streptococcus pneumoniae remains an important cause of bacteremia worldwide. Last years, a decrease of S. pneumoniae penicillin-resistant isolates has been observed. The objective of this study was to describe the episodes of bacteremia due to S. pneumoniae during a period of 11 years. Epidemiological and clinical data, serotypes causing bacteremia, antibiotic susceptibility and prognosis factors were studied. Over a period of 11 years, all the episodes of S. pneumoniae bacteremia were analysed. Their clinical and microbiological features were recorded. Statistical analysis was carried out to determine risk factors for pneumococcal bacteremia and predictors of fatal outcome. Finally, 67 S. pneumoniae bacteremia episodes were included in this study. The majority of cases were produced in white men in the middle age of their life. The main predisposing factors observed were smoking, antimicrobial and/or corticosteroids administration, chronic pulmonary obstructive disease and HIV infection, and the most common source of bacteremia was the low respiratory tract. The main serotypes found were 19A, 1, 14 and 7F. Seventy-seven percent of these isolates were penicillin-susceptible, and the mortality in this serie was really low. Statistical significance was observed between age, sex and race factors and the presence of bacteremia, and there was relationship between the patient's condition and the outcome. In our study, S. pneumoniae bacteremia is mainly from community-acquired origin mainly caused in men in the median age of the life. 40% of bacteremias were caused by serotypes 19A, 1, 7F and 14. During the period of study the incidence of bacteremia was stable and the mortality rate was very low.

Antimicrobial susceptibility of invasive pneumococcal isolates from a region in south-west Sweden 1998–2001

Invasive disease caused by antibiotic resistant pneumococci is a worldwide problem. All invasive pneumococcal strains in an area of south-west Sweden with 1.7 million inhabitants were collected prospectively during 1998-2001. Minimum inhibitory concentrations (MICs) were determined by E-test and correlated to serotypes and clinical characteristics. Of 827 strains, 744 (90%) were susceptible (S) to all agents tested and 83 (10%) were indeterminate (I) or resistant (R) to at least 1 agent. 22 isolates (2.7%) were I to penicillin (MIC >0.06 to < or = 1.0 mg/l), but none were R (MIC >1.0 mg/l). Numbers and proportions of decreased susceptibility against other agents tested were as follows: erythromycin R: 30 (3.6%), clindamycin R: 6 (0.7%), tetracycline R: 16 (1.9%), moxifloxacin R: 1 (0.1%), cotrimoxazole I: 17 (2%) and R: 31(4%). Non-susceptibility to at least 1 agent was not correlated with age, clinical manifestation, underlying diseases and outcome. The serotype distribution differed between non-susceptible and susceptible strains. The serotypes in the 7-valent pneumococcal conjugate vaccine covered 42% of all infections and 73% of those caused by non-susceptible strains. In conclusion, the impact of antibiotic resistance in invasive pneumococcal disease remains limited in south-west Sweden.

Streptococcus pneumoniae in western Europe: serotype distribution and incidence in children less than 2 years old

We did a systematic search and synthesis of evidence on the incidence of invasive pneumococcal disease, symptomatic disease, and circulating Streptococcus pneumoniae serotypes in western Europe. Using data from studies published between 1992 and 2005 we calculated a weighted mean invasive pneumococcal disease and pneumococcal meningitis incidence rate per 100,000 children aged 2 years or younger within 95% confidence intervals, together with the prevalence of S. pneumoniae serotypes and resistance to penicillin. Invasive pneumococcal disease incidence was 27.03 cases per 100,000 children under 2 years (95% CI 21.85-33.43) [corrected] Heptavalent conjugate vaccine serotypes account for 43.18-75.32% of isolates among people aged under 18 years of age. 11% of isolates in individuals aged under 18 years were penicillin resistant. The incidence of invasive pneumococcal disease appeared consistently lower in western European countries compared with studies from the USA. Thus the use of studies of vaccine effectiveness based on the US population may lead to an overestimation of the benefits of its introduction in Europe.

Occurrence of invasive pneumococcal disease and number of excess cases due to influenza

Background

Influenza is characterized by seasonal outbreaks, often with a high rate of morbidity and mortality. It is also known to be a cause of significant amount secondary bacterial infections. Streptococcus pneumoniae is the main pathogen causing secondary bacterial pneumonia after influenza and subsequently, influenza could participate in acquiring Invasive Pneumococcal Disease (IPD).

Methods

In this study, we aim to investigate the relation between influenza and IPD by estimating the yearly excess of IPD cases due to influenza. For this purpose, we use influenza periods as an indicator for influenza activity as a risk factor in subsequent analysis. The statistical modeling has been made in two modes. First, we constructed two negative binomial regression models. For each model, we estimated the contribution of influenza in the models, and calculated number of excess number of IPD cases. Also, for each model, we investigated several lag time periods between influenza and IPD. Secondly, we constructed an "influenza free" baseline, and calculated differences in IPD data (observed cases) and baseline (expected cases), in order to estimate a yearly additional number of IPD cases due to influenza. Both modes were calculated using zero to four weeks lag time.

Results

The analysis shows a yearly increase of 72–118 IPD cases due to influenza, which corresponds to 6–10% per year or 12–20% per influenza season. Also, a lag time of one to three weeks appears to be of significant importance in the relation between IPD and influenza.

Conclusion

This epidemiological study confirms the association between influenza and IPD. Furthermore, negative binomial regression models can be used to calculate number of excess cases of IPD, related to influenza.

Nosocomial bloodstream infections caused by Streptococcus pneumoniae

A retrospective study of Streptococcus pneumoniae bacteraemia among adult patients in two large teaching hospitals in Spain identified 108 (10.6%) of 1,020 episodes as nosocomial pneumococcal bloodstream infections (NPBIs). Seventy-seven clinical records with sufficient data were available for analysis. The interval between admission and a positive blood culture was 3--135 days (median 17 days; interquartile range 8--27). The main underlying and predisposing conditions for NPBI were malignancy (31%), chronic obstructive pulmonary disease (28.6%), heart failure (16.9%), chronic renal failure (15.6%), liver cirrhosis (13%) and infection with human immunodeficiency virus (13%). Overall, 31.2% of patients developed severe sepsis, 11.7% septic shock, and 3.9% multi-organ failure. The main portals of entry were pneumonia (70.1%), meningitis (5.2%) and primary peritonitis (5.2%). Of the responsible serogroups, 78% were included in the 23-valent polysaccharide vaccine. Thirty-five (45.5%) patients died, with death considered to be related to the NPBI in 21 (27.3%) cases. Following multivariate analysis, factors that independently predicted death after adjusting for age were: ultimately fatal underlying disease (OR, 8.9; 95% CI, 0.8--94.3; p<0.001); rapidly fatal underlying disease (OR, 15.0; 95% CI, 2.8--81.3; p<0.001); heart failure (OR, 8.11; 95% CI, 1.1--60.8; p<0.03); inadequate empirical therapy (OR, 10.6; 95% CI, 1.2--97; p<0.003); a severe sepsis score (OR, 9.5; 95% CI, 1.9--47.0; p<0.001); and septic shock or multi-organ failure (OR, 63.7; 95% CI, 4.9--820.7; p<0.001). Adequate empirical therapy was an independent protective factor (OR, 0.05; 95% CI, 0.04--0.58; p<0.005), but the use of more than one antimicrobial agent was not.

Bacteraemia in the elderly: predictors of outcome in an urban teaching hospital

OBJECTIVES

To analyze the underlying factors of mortality in elderly adults with bacteraemia.

METHODS

The study included 238 episodes of bacteraemia in an urban public teaching hospital. Retrospective chart review recorded demographic information, comorbid conditions, length of stay, source of infection, and physiologic and laboratory data on admission.

RESULTS

Of the 238 episodes of bacteraemia, 128 patients were 65-74 years of age and 110 patients were > or =75 years of age. Eighty-one percent came from home. Fifty-four percent had Gram positive cocci detected in blood cultures and 36% had Gram negative bacilli. Factors associated with increased odds of mortality included underlying renal disease, admission to MICU, hypotension and hypoalbuminemia. Decreased odds of mortality were associated with being admitted from home and receiving appropriate antibiotics.

CONCLUSIONS

Bacteraemia in the elderly has a high mortality rate, but is not significantly increased in those >or =75 years of age. The recent microbiology has shifted from Gram negative bacilli to Gram positive cocci. Physiologic abnormalities on admission predict worse outcomes in the elderly bacteraemic patient. Hypoalbuminemia on admission is associated with higher mortality rates in the elderly.

Differences in presentation and outcome of invasive pneumococcal disease among patients with and without HIV infection in the pre-HAART era

Invasive pneumococcal disease (PD) occurs frequently among HIV-infected patients, but it is unclear whether its manifestations and outcome are different compared to those observed among patients without HIV-1 infection. Because the immune reconstitution that accompanies antiretroviral therapy may change some of these features and because most cases of HIV- 1 infection occur in resource-poor settings of the world where access to antiretroviral agents is limited, we compared PD among patients with and without HIV-1 infection in a North American population before the introduction of highly active antiretroviral therapy (HAART). The records of all pneumococcal cultures processed at this medical center over a period of 20 months were used to identify patients with invasive PD. Hospital records were reviewed for 103 of these patients (52 with and 51 without HIV-1 infection) and demographic, clinical, laboratory, radiographic, and microbiologic information was abstracted and subsequently analyzed. Despite similarities in presenting signs and symptoms, we found a higher incidence of bacteremia but a more favorable outcome with less frequent requirements for intubation and admission to intensive care units and better survival among individuals with HIV infection. Factors such as less advanced age, the presence of fewer comorbid conditions, or a less florid inflammatory response among HIV-infected individuals may account for differences in outcome of invasive PD.

Changes in the epidemiology of pneumococcal bacteremia in a Swiss university hospital during a 15-year period, 1986-2000

OBJECTIVE

To evaluate changes in epidemiological characteristics and outcome of patients with pneumococcal bacteremia during a 15-year period in a Swiss university hospital.

PATIENTS AND METHODS

We reviewed the medical records of all hospitalized adults at the University Hospital Basel, Basel, Switzerland, whose blood culture yielded Streptococcus pneumoniae from January 1, 1986, through December 31, 2000.

RESULTS

We analyzed 405 episodes of pneumococcal bacteremia in 394 patients. The mean annual incidence of 1.78 episodes per 1000 hospital admissions was inversely related to the mean atmospheric temperature of the area. During the study period, penicillin nonsusceptibility increased from 0% to 17%. The overall case-fatality rate was 25%, which decreased from 33% to 17% between the first and the second half of the study period (P<.001). The proportion of women with pneumococcal bacteremia increased from 37% to 52%. Independent risk factors for fatal outcome were coronary artery disease (P<.001; relative risk [RR], 4.3; 95% confidence interval [CI], 3.4-5.1), neutropenia (P=.001; RR, 3.2; 95% CI, 1.9-4.8), and age 65 years or older (P=.001; RR, 2.9; 95% CI, 1.8-4.2), whereas prior respiratory tract infection (P=.03; RR, 0.3; 95% CI, 0.1-0.5) and the occurrence of pneumococcal bacteremia in the second half of the study period (P=.01; RR, 0.4; 95% CI, 0.2-0.6) were independent predictors of survival. The case-fatality rate in human immunodeficiency virus (HIV)-infected patients was significantly lower than in patients not infected with HIV or in those with unknown HIV status (9% vs 27%; P=.006), which correlated with the younger mean +/- SD age of HIV-infected patients (33.2+/-6.6 years) compared with patients not infected with HIV (63.1+/-18.1 years) (P<.001).

CONCLUSIONS

The case-fatality rate of patients with pneumococcal bacteremia decreased significantly between the first and second half of the study period, despite the increased prevalence of penicillin-nonsusceptible isolates. Independent risk factors for fatal outcome were coronary artery disease, neutropenia, and age 65 years or older, whereas prior respiratory tract infection and the occurrence of pneumococcal bacteremia in the second half of the study period were independent predictors of survival. HIV infection was a predisposing factor for pneumococcal bacteremia but was not a risk factor for fatal outcome.

Clinical and microbiological epidemiology of Streptococcus pneumoniae bacteremia in eight French counties

OBJECTIVE

To describe the incidence of pneumococcal bacteremia not associated with infection of the central nervous system, investigate the susceptibility of bacterial isolates to beta-lactams, evaluate risk factors for antibiotic resistance, and determine factors predicting patient outcome.

METHODS

Over a period of 1 year, 919 Streptococcus pneumoniae isolates were collected from 919 patients with bacteremia in eight French counties. Their clinical and microbiological features were recorded. Univariate and multivariate analyses were used to determine risk factors for penicillin-non-susceptible pneumococcal bacteremia and predictors of fatal outcome.

RESULTS

Of the 919 patients in the study, 27% were infected with penicillin-non-susceptible pneumococci (PNSP): 17.8% of the isolates were intermediate to penicillin, 7.2% were resistant to penicillin, 16% were intermediate to amoxicillin, and 11% were intermediate to cefotaxime; no PNSP were resistant to either of the last two antibiotics. The most common PNSP serotypes isolated were 14 (41%) and 23 (24%). A statistically significant relationship between PNSP infection and age below 5 years or above 60 years in the different counties was observed by univariate and multivariate analysis. Gender, origin of bacteremia, co-morbidity, immunodeficiency, previous hospitalization and nosocomial infection were not predisposing factors associated with PNSP. The mortality rate was 20.6%: there was no increase in mortality among patients with PNSP bacteremia. Age was the strongest risk factor for mortality, but immunodeficiency also seemed to have had an impact on mortality. Clinical outcome was more closely related to clinical conditions than to the susceptibility status of S. pneumoniae.

CONCLUSION

Among cases of bacteremia, 27% were caused by PNSP, but this level varies according to the counties and the age of the patients. Infection-related mortality was high, but there was no increase related to penicillin G non-susceptibility of the infecting strain.

The burden of invasive pneumococcal disease and the potential for reduction by immunisation

Streptococcus pneumoniae causes invasive disease world-wide and in all age groups. The reported incidence varies geographically and is increased in certain population groups. The incidence is highest in children less than 2 years and is also increased in the elderly. Mortality remains substantial even in the developed world despite appropriate antimicrobial therapy. The emergence of penicillin-resistant pneumococci highlights the importance of immunisation as a means to prevent disease. This review discusses the burden of invasive pneumococcal disease, identifies high-risk patients and analyses evidence for vaccine efficacy and cost-effectiveness.

Geographical differences in invasive pneumococcal disease rates and serotype frequency in young children

The development of glycoconjugate vaccines for Streptococcus pneumoniae that are effective in very young children has renewed interest in identification of which among the more than 90 pneumococcal serotypes are most likely to cause invasive pneumococcal disease (IPD). Serotype distribution is thought to vary geographically, even between regions as socioeconomically similar as western Europe and North America. To explain these variations, we note the considerable variation that exists between reported rates of IPD in young children in the USA and west European countries. We postulate that this variation is attributable to different blood-culture rates and practices, and that mild IPD is probably underdiagnosed and under-reported in western Europe. On the basis of a comparison of serotype distributions between the two regions, we also postulate that those serotypes found at similar frequencies in both regions are virulent and rarely cause mild disease. As a result, reported distributions of IPD serotypes, especially when expressed as percentages, might be strongly skewed by the distribution of clinical presentations in a particular study population.

The epidemiology of hospitalization of elderly Americans for septicemia or bacteremia in 1991-1998. Application of Medicare claims data

PURPOSE

To describe the epidemiology of hospitalization of elderly Americans for septicemia or bacteremia.

METHODS

Medicare claims data for discharges from 1991 through 1998 were used to study 75,920 hospitalizations with the principal diagnosis of septicemia or bacteremia in patients aged 65 years or older.

RESULTS

"Unspecified septicemia" was the commonest principal diagnosis, followed by septicemia due to Escherichia coli or staphylococci. From 1991 through 1997, annual discharges for "unspecified septicemia" increased 108%, and those for pneumococcal septicemia increased 310%. Decreases in reported septicemia were seen after increases in the proportion of beneficiaries in Medicare health maintenance organizations. Discharge rates for septicemia principal diagnoses increased steeply with age. Age-specific discharge rates were usually highest for black men and lowest for white women. Exceptions included septicemia due to E. coli, with white men at low risk, and pneumococcal septicemia, without significant differences between races or sexes. The case-fatality rate in hospital ranged from 4.2% with "bacteremia" and 6.9% with E. coli septicemia to 22.2% with "septicemia due to gram-negative organism, unspecified," and 26.8% with "unspecified septicemia." Staphylococcal septicemia, septicemia due to pseudomonas, and septicemia due to anaerobes were the costliest common principal diagnoses in terms of the mean duration of hospital stay.

CONCLUSIONS

Unexplained sharp increases were reported in hospitalization for septicemia or bacteremia in elderly Americans. Marked variation by race and sex were evident in discharge rates with these principal diagnoses. Prognosis and average cost of treatment also differed substantially among common rubrics. Further investigation of individual diagnoses should concentrate on explaining secular trends, exploring the basis for variation by race and sex, and elucidating risk factors for poor clinical outcomes.

Epidemiology of invasive pneumococcal infections in children aged 0-6 years in Denmark: a 19-year nationwide surveillance study

The impact of the new pneumococcal conjugate vaccines on invasive disease burden in Danish children was evaluated by analysing the results from the last 19 years of a nationwide surveillance of invasive pneumococcal infections. During 1981-1999, the Streptococcus Unit at Statens Serum Institut, Copenhagen, received 1123 invasive pneumococcal isolates from children aged 0-6 years. Nearly 72% (71.8%) of the pneumococcal isolates were from children aged <2 y. The median ages of children with pneumococcal meningitis and bacteraemia were 10.2 mo and 15.9 mo, respectively. The incidence of pneumococcal meningitis remained stable during the study period. The mean annual incidence rates of pneumococcal meningitis among children aged <1, <2, and <7 years were 17.4, 12.4, and 4.3 per 100,000, respectively, during 1981-1999 (overlapping age groups are used throughout this article to facilitate the comparison of incidence data from different countries or among different studies). The annual incidence of pneumococcal bacteraemia increased from 1981 to 1996, after which a slight fall was noted. During the last six years of the study period, the mean annual incidence rates of bacteraemia were 30.1, 32.5, and 14.0 per 100,000 children aged < 1, < 2, and < 7 years. In the 1990s, pneumococcal isolates with reduced sensitivity to penicillin (0-5% each year) and erythromycin (7.4% in 1999) emerged as a cause of invasive infections in children aged 0-6 years in Denmark. During 1981-1999, 10 serotypes (1, 4, 6A, 6B, 7F, 9V, 14, 18C, 19F, 23F) caused 82% of invasive infections in Danish children. Importantly, no significant temporal changes in overall serotype distribution or differences in serotype distributions between girls and boys could be documented during the study period.

CONCLUSION

According to the Kaiser Permanente trial, the 7-, 9-, and 11-valent pneumococcal conjugate vaccines will probably cover around 60%, 70%, and 80%, respectively, of all invasive pneumococcal infections in Danish children aged 0-6y, corresponding to 12-14 episodes of meningitis and 40-60 episodes of bacteraemia per year.

Epidemiology of pneumococcal infections in Swedish children

OBJECTIVE

This paper provides an overview of pneumococcal infections in Swedish children.

METHOD

Data supplied by the Swedish Institute for Infectious Disease Control (SMI) provided information on invasive pneumococcal isolates and on isolates with reduced susceptibility to penicillin. Disease burden was estimated from data collected in northern Stockholm and Malmöhus County.

RESULTS

Only 3-6% of the total number of invasive pneumococcal isolates came from children 0-15 years of age. Predominant serotypes in descending frequency were 7, 6, 14, and 23. Strains from all sources with reduced sensitivity to penicillin (MIC > or = 0.5 mg/l) were found in 3% of children and varied between 0.2% and 11%, with the highest value found in Southern Sweden (predominating strains were 9, 19, 15, 6, and 23). A 10-year review of all cases of meningitis in Northern Stockholm reflected an incidence of 10/100,000 (0-2 years) or 5.8/100,000 (0-5 years), with severe sequelae occurring in 20% of children. This information can be used to predict an annual incidence of 30 cases of meningitis in Sweden.

CONCLUSION

The large proportion of serotype 7 among invasive isolates is distressing since this serotype is not represented in the present 7- and 9-valent protein-conjugated vaccines under development. However, the heptavalent vaccine, including serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F would (at a serotype level) provide coverage against 83% of the resistant isolates in Southern Sweden.

Frequency of penicillin-resistant pneumococci in children is correlated to community utilization of antibiotics

OBJECTIVE

To study the impact of the utilization of antibiotics in children at the population level on the frequency of penicillin-nonsusceptible pneumococci (PNSP).

DESIGN

Children ages 0 to 6 years with a nasopharyngeal culture of PNSP were registered on place of residency in the 20 municipalities of the former Malmöhus County (since 1998 a part of Skåne County). Where possible the total number of nasopharyngeal cultures with growth of pneumococci was registered as well. All antibiotic prescriptions for 0- to 6-year-old children were analyzed in the 20 municipalities.

MAIN OUTCOME MEASURES

Correlation between the utilization of antibiotics and the frequency of PNSP in children at the municipality level.

RESULTS

The proportion of PNSP among all isolates of pneumococci from nasopharyngeal cultures varied between 0 and 49.5%. The antibiotic utilization in children varied among the 20 neighboring municipalities from 8.5 to 19.7 defined daily doses per 1000 children per day. The municipalities with high total utilization also had more frequent use of macrolides and broad spectrum antibiotics. The was a significant correlation between antibiotic use and the proportion of PNSP (correlation coefficient, 0.96; P = 0.002), and the correlation coefficients for trimethoprim-sulfamethoxazole, amoxicillins, macrolides and cephalosporins were significant at the 0.001 level. There was no significant correlation between the use of penicillin V and the frequency of PNSP. CONCLUSIONS. There was a significant correlation between the frequency of PNSP and the utilization of antibiotics in children at the population level.

Penicillin-resistant pneumococci in southern Sweden, 1993-1997

In Malmöhus County, Southern Sweden, the frequency of penicillin-resistant pneumococci in nasopharyngeal specimens of outpatients with respiratory tract infections increased from 3.1% in 1993 to 7.6% in 1995, and was thereafter rather stable. Over the period, 82-85% of the patients with penicillin-resistant strains were children 0-6 years of age. Ten groups/types constituted 96-100% of the penicillin-resistant isolates. Grouping/typing of 200 consecutive isolates in October and November each year indicated that the distribution of groups/types amongst patients with respiratory tract infections was rather constant over the period. The frequency of penicillin-resistant pneumococci of groups/types 6, 14, and 19 roughly corresponded to the occurrence of these groups/types amongst the consecutive isolates. Other groups/types 9, 15, 21, and 23 either showed a pronounced increase or decrease, which could not be related to the prevalence of these groups/types among the consecutive isolates or degree of antibiotic resistance. Penicillin-resistant group 9, introduced in the area in 1993, consisted of one single clone, 9V. The stabilized level of penicillin resistance since 1995 may be related to the preventive measures implemented in the area, including day-care interventions, and measures to reduce the prescription rate of antibiotics to outpatients with respiratory tract infections.

Which pneumococcal serogroups cause the most invasive disease: implications for conjugate vaccine formulation and use, part I

We analyzed >70 recent data sets to compare the serogroups causing invasive pneumococcal disease (IPD) with those represented in conjugate vaccine formulations. Five to 8 and 10-11 serogroups comprise at least 75% of pneumococcal isolates from young children and older children/adults, respectively, in each geographic region. Serogroups in the 7-valent formulation (4, 6, 9, 14, 18, 19, and 23) cause 70%-88% of IPD in young children in the United States and Canada, Oceania, Africa, and Europe, and <65% in Latin America and Asia. Serogroups in the 9-valent formulation (7-valent+1, 5) cause 80%-90% of IPD in each region except Asia (66%). Serogroup 1 accounts for >6% of IPD in each region, including Europe, except the United States and Canada and Oceania. In contrast, several serogroups not found in 7-, 9-, and 11-valent conjugate formulations are significant causes of disease in older children/adults. Nevertheless, each conjugate formulation could prevent a substantial IPD burden in each region and age group.