Capsular types and susceptibility to penicillin of pneumococci isolated from cerebrospinal fluid or blood in Denmark, 1983-1988

Invasive pneumococcal infections in Denmark from 1995 to 1999: epidemiology, serotypes, and resistance

Danish nationwide surveillance data on invasive pneumococcal disease from the 5-year period from 1995 to 1999, including 5,452 isolates, are presented and described. Annual overall incidence rates, serotype distribution, and antimicrobial susceptibility patterns of the isolates were monitored. Major changes in the total annual incidence rate from 27/100,000 in 1996 to 17/100,000 in 1999 and a significant change in the proportion of invasive isolates belonging to types 1 and 12F were observed. The serotype coverage rate by the 23-valent polysaccharide vaccine among the elderly was 92.9%, and the serotype coverage rate by the 7-, 9-, and 11-valent pneumococcal conjugate vaccines among children less than 2 years old were 71.7, 75.2, and 81.4%, respectively. Invasive isolates with reduced susceptibility to penicillin or erythromycin increased from 1995 to 1999, with a high proportion of the penicillin-nonsusceptible invasive isolates originating from people 60 years old or older (57.0%). These observations underline the importance of adequate surveillance systems of invasive pneumococcal disease to introduce and maintain national vaccine strategies and adequate antibiotic policy.

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.

Distribution of capsular types and penicillin-resistance of strains of Streptococcus pneumoniae causing systemic infections in Argentinian children under 5 years of age. Streptococcus pneumoniae Working Group

Streptococcus pneumoniae (SPN) is the most common cause of invasive infections in children, with high levels of mortality in developing countries. An increase in frequency of penicillin-resistant strains is reported in most parts of the world. A study was undertaken in Argentina and 5 other countries of the region, to determine the type distribution and penicillin resistance rate of SPN isolated from invasive infections in children less than 5 years old. Between June 1994 and March 1996, a total of 505 SPN isolated from sterile sites were collected from 15 hospitals located in 9 cities of different geographic areas. Clinical and epidemiological data from 443 children were analyzed. Sixty five percent SPN were isolated from children less than 2 years old. Pneumonia was the clinical diagnosis in 58% of the cases, meningitis in 22%, and sepsis in 10.6%. Isolates were recovered from blood (51.2%), pleural fluid (22.7%), CSF (20.7%), and other sterile sites (5.4%). Thirty different pneumococcal capsular types were identified and the 10 most frequent in descending order were: 14, 5, 1, 6A/6B, 7F, 9V, 19F, 19A, 16F y 23F, representing 89.3% of the total. Overall, 13.1% of isolates showed intermediate resistance to penicillin while 11.3% showed high resistance. Lethality was 8.8%, without correlation with penicillin-resistance and/or type. These result should be used in selecting the optimal combination of specific types for a conjugate vaccine, useful in children less than 2 years old and for considering therapeutic strategies for invasive pneumococcal 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.

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

In a survey of pneumococcal blood isolates from patients in Southern Sweden, 560 isolates were found between 1981 and 1996. Between these years, the incidence of pneumococcal bacteraemia increased from 5.2 to 15.2/100,000/y. The eight most common serogroups/types (14, 7, 9, 6, 23, 3, 4 and 19) accounted for > 75% of the isolates, and 96.4% of the isolates were of serogroups/types represented in the present vaccine. A male preponderance (1.17:1) was noted, and the men were younger than the women (mean 57 vs 63 y of age; p < 0.05). The overall case-fatality rate during the period was 19%. Seven isolates with reduced susceptibility to penicillin were noted, all from 1991 to 1996. The increasing incidence of pneumococcal bacteraemia could not be explained by any of the following factors; age or sex of the patients, changes in prevailing serogroups/types, variations in vaccine use, emergence of penicillin-resistance, more liberal indications for blood cultures or improved culture methods.

Pneumococcal vaccination: an important strategy to prevent pneumonia in Aboriginal and Torres Strait Island adults

The objective of the study was to examine the appropriateness of the National Health and Medical Research Council (NHMRC) recommendations concerning pneumococcal vaccination for Aboriginal and Torres Strait Island adults. Laboratory surveillance of invasive pneumococcal disease identified 95 cases acquired by adults 15 years of age and over in Far North Queensland from 1992 to 1995. The most common diagnosis was pneumonia (77 per cent). Sixty-one cases (64 per cent) occurred in Aboriginal and Torres Strait Island adults, who acquired the disease at a younger age (mean 40 years) than did other adults (mean 50 years). Most (93 per cent) of the Aboriginal and Torres Strait Island adults had at least one of the pre-existing medical conditions in the NHMRC criteria for pneumococcal vaccination. The most common was 'alcohol abuse' (62 per cent). Fifty-three (93 per cent) of the pneumococcal isolates from the Aboriginal and Torres Strait Island adults who had pre-existing conditions were serotyped. Fifty (94 per cent) belonged to types included in the currently available pneumococcal vaccine. We conclude that the NHMRC recommendations for pneumococcal vaccination are appropriate, considering the pattern of invasive pneumococcal disease that occurs in Aboriginal and Torres Strait Island adults in Far North Queensland. Because pneumococcal vaccination can reduce the pneumonia-associated morbidity and premature mortality experienced by Aboriginal and Torres Strait Island adults, the vaccine should be offered routinely to those considered to be at risk, particularly young men who have recently begun to consume hazardous amounts of alcohol, and recently diagnosed diabetics.

Incidence of invasive pneumococcal disease and distribution of capsular types of pneumococci in Denmark, 1989-94

During the period 1989-94, 4620 strains of Streptococcus pneumoniae (4063 from blood and 557 from cerebrospinal fluid), from cases of invasive disease in Denmark, were received for capsular typing and penicillin susceptibility testing. During the study period the incidence of bacteraemic pneumococcal disease increased from 10 to 18 cases per 100000 inhabitants per year. The highest rates were seen in the very young, age less than 5 years (23/100000/year, in 1994), and in the elderly, age greater than 60 years (55/100000/year, in 1994). The annual number of cases of meningitis did not vary. Overall, 92% (93% blood, 87% CSF) of isolates and 94% of all childhood isolates belonged to the 23 vaccine types. The capsular types occurring most commonly among the 4123 pneumococcal strains from adults were types 1, 4, 14, 6A + 6B, 7F, 9V, 3, 12F, and 8 (in order of frequency). The ten most frequently occurring types from children (6A + 6B, 18C, 14, 1, 7F, 19F, 9V, 4, and 23F) covered 84% of the cases of bacteraemia and meningitis. Reduced susceptibility to penicillin was rare (< 1%).

Bacteraemic pneumococcal disease in a teaching hospital in Finland

A total of 94 adult patients with bacteraemic pneumococcal disease were retrospectively analyzed for the factors associated with a fatal outcome. Included there were 61 males and 33 females with a mean age of 54.1 =/- 17.7 years. Of all patients, 28 (29.8%) were previously healthy, 66 (70.2%) had at least one chronic underlying disease and 29 (30.9%) were classified as alcohol abusers. The total case-fatality rate was 34%, which is higher than in the other recent Scandinavian studies. The disease was fulminant in 13 patients who died within 24 hours of admission. The mortality was significantly higher among those patients who had underlying diseases than among those who were previously healthy (p = 0.03). In addition, unfavourable prognosis was associated with septic shock on arrival (p = 0.03) respiratory insufficiency requiring mechanical ventilation (p < 0.05) and nosocomial infection (p = 0.03). The patients who succumbed were significantly older that those who survived (p < 0.01). Moreover, the absence of leucocytosis, thrombocytopenia and elevated serum creatinine levels predicted an unfavourable outcome. Contradictory to some previous reports, increased mortality was associated neither with the male sex, alcohol abuse nor the focus of infection. The continuously high mortality and rapid lethality of bacteraemic pneumococcal disease underscore the importance of following the present recommendations on the use of pneumococcal vaccine in high-risk patients.

Evidence of recombination and an antigenically diverse immunoglobulin A1 protease among strains of Streptococcus pneumoniae

The genetic relationships among 114 isolates of Streptococcus pneumoniae representing mainly nine serotypes that frequently cause severe childhood disease in Northern Europe were examined by use of multilocus enzyme electrophoresis. A comparison was made of the corresponding antigenic variations of excreted immunoglobulin A1 (IgA1) proteases detected by enzyme neutralization assays. Allelic variation at 13 gene loci among 70 electrophoretic types disclosed a comparatively low mean genetic diversity per locus (H = 0.319). In contrast, IgA1 proteases showed extensive antigenic diversity as 17 different inhibition types were distinguished. A lack of overall clonality was apparent from the linkage equilibrium of alleles harbored by 28 isolates chosen to represent the genetic diversity of the study population. However, certain clones, such as those marked by identical electrophoretic type, serotype, and IgA1 protease type, persisted for a sufficiently long time to enable clonal spread between distant geographic areas. Among clonally related isolates, examples illustrating a shift of capsular serotype or IgA1 protease type supported the view that recombination occurs in vivo in corresponding genes. In conclusion, over time, horizontal genetic exchange appears to be sufficiently frequent to disrupt the clonal structure otherwise generated by binary fission in natural populations of S. pneumoniae. The clonal instability combined with considerable antigenic heterogeneity renders the pneumococcal IgA1 protease less attractive as a potential component of future vaccines.

Comparative study of five different DNA fingerprint techniques for molecular typing of Streptococcus pneumoniae strains

The aim of this study was to identify the strengths and weaknesses of five DNA fingerprint methods for epidemiological typing of Streptococcus pneumoniae. We investigated the usefulness of (i) ribotyping, (ii) BOX fingerprinting with the BOX repetitive sequence of S. pneumoniae as a DNA probe, (iii) PCR fingerprinting with a primer homologous to the enterobacterial repetitive intergenic consensus sequence, (iv) pulsed-field gel electrophoresis of large DNA fragments, and (v) restriction fragment end labeling to detect restriction fragment length polymorphism of small DNA fragments. Twenty-eight S. pneumoniae strains isolated from the blood and/or cerebrospinal fluid of 21 patients were analyzed. Genetic clustering among the 28 strains was independent of the DNA fingerprint technique used. However, the discriminatory power and the similarity values differed significantly among the individual techniques. BOX fingerprinting, pulsed-field gel electrophoresis, and restriction fragment end labeling provided the highest degree of discriminatory power. Furthermore, the ease with which computerized fingerprint analysis could be conducted also varied significantly among the techniques. Ribotyping, BOX fingerprinting, and restriction fragment end labeling were very suitable techniques for accurate computerized data analysis. Because of their high discriminatory potential and ease of accurate analysis, we conclude that BOX fingerprinting and restriction fragment end labeling are the most suitable techniques to type pneumococcal strains.

Serotypes and resistance patterns of Streptococcus pneumoniae causing systemic disease in northern Norway

During the period 1985-1990, Streptococcus pneumoniae was isolated form 97 patients with systemic pneumococcal disease in Northern Norway. Systemic disease occurred most frequently in the age groups 0-4 years and > 60 years. An increasing incidence was observed, especially among children less than five years old. Serotypes covered by the 23-valent pneumococcal polysaccharide vaccine were found in 86 of 97 (88.7%) isolates. The vaccine did not cover 16.7% of the systemic isolates from children less than five years old. Reduced sensitivity to penicillin was found in one isolate (1.0%) which was resistant to ampicillin, doxycycline and chloramphenicol. The E-test and the Rosco agar diffusion test differed in sensitivity to penicillin, chloramphenicol, ciprofloxacin and erythromycin. Three serotype 12F strains showed unusual cross-resistance to chloramphenicol and erythromycin.

Detection of pneumococcal polysaccharide antigens in the urine of patients with bacteraemic and non-bacteraemic pneumococcal pneumonia

Countercurrent-immunoelectrophoresis (CIE) was used to detect pneumococcal capsular polysaccharide and C-polysaccharide (C-Ps) antigens in urine. The neutral capsular polysaccharides of types 7F and 14 were detected by coagglutination. We found pneumococcal polysaccharide in urine with the same frequency in two groups of patients, i.e. a non-bacteraemic pneumonia group (68%) and a group of patients with pneumococcal bacteraemia (66%). C-Ps was detected in the urine of two patients (4%) and, therefore, this test has no value in the diagnosis of pneumococcal infections. Since there is no sensitive, non-invasive, single procedure for the diagnosis of non-bacteraemic pneumococcal pneumonia we conclude that attempts to detect pneumococcal capsular polysaccharide by CIE in combination with coagglutination (types 7F and 14) may be a useful diagnostic supplement in the search for the etiological agent in pneumonia in adults until new, more sensitive diagnostic methods have been developed.

Resistance, drug failure, and disease progression

The clinical significance of the reduced in vitro susceptibility of HIV to antiretroviral agents has been difficult to elucidate for nucleoside analogs such as zidovudine. However, the virological significance of resistance to nevirapine and other HIV-1-specific reverse transcriptase inhibitors has been established. With antiretroviral therapy, disease progression is not equivalent to drug failure, which is not equivalent to drug resistance. Clinical disease progression is only indirectly linked to HIV replication. Drug resistance is complex, and combining drugs does not appear to delay emergence of resistant strains of HIV although it may affect the specific amino acid substitutions. Drug resistance does appear to contribute to drug failure. The clinical trial ACTG 116B/117 found that the duration of prior zidovudine therapy was not related to the relative benefit of switching to didanosine. Preliminary results of analysis of resistant strains of HIV isolated from ACTG 116B/117 patients revealed that the relative hazard of progression was about threefold higher for patients with high-level resistance to zidovudine, syncytium-inducing biological phenotype, and an AIDS diagnosis at baseline. This study showed clearly that acquisition of an HIV strain with high-level resistance to zidovudine was a poor prognostic factor. Although nevirapine resistance emerges rapidly, preliminary data suggest that high dosages may be active against HIV even in the presence of resistant HIV strains. At the present time, viral resistance and biological phenotype are not useful in the management of individual patients.

Pneumococcal meningitis in adults

A retrospective study was conducted to examine the clinical features and outcome of 31 adult pneumococcal meningitis patients during the years 1981-92. The incidence was 1.0/100,000 adults/year. The case fatality rate was 16% (5/31), and in patients older than 70 years, 33% (3/9). Sequelae were seen in 29% (7/24), mostly otoneurologic symptoms. In 27/28 bacterial isolates the serotypes found were included in the 23-valent unconjugated polysaccharide vaccine in current use. All 28 isolates were fully sensitive to penicillin. 49/51 non-meningitis blood isolates had MIC values < or = 0.06 mg/l, 2 isolates had MIC values of 0.125 mg/l and 0.25 mg/l, and 50/50 were serotypes included in the 23-valent vaccine. Pneumococcal meningitis is a disease causing considerable mortality and morbidity. The relatively low case fatality rate found in the present study may be due to the patients' good health prior to admission, rapid specific microbiological diagnosis, absence of penicillin-resistant pneumococci among the meningitis strains, and immediate institution of specific and supportive therapy.