Epidemic Pneumococcal Pneumonia

Hodges, Richard G.; MacLeod, Colin M.

doi:10.1093/oxfordjournals.aje.a119092

Cited by 19 publications

(13 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, we believe that this value is probably an underestimate. In fact, in most surveillance studies such as ours, a single pneumococcal-like colony is routinely picked from a primary culture for further purification and characterization, although it is well known that mixed cultures are frequently found in nasopharyngeal samples (Hodges et al, 1946;Sá-Leão et al, 2002;St Sauver et al, 2000). Since many NTPn exhibit rough and small colonies resembling those of viridans streptococci, they may be neglected when smooth and bigger colonies typical of capsulated pneumococci are also present.…”

Section: Discussionmentioning

confidence: 99%

Identification, prevalence and population structure of non-typable Streptococcus pneumoniae in carriage samples isolated from preschoolers attending day-care centres

et al. 2006

View full text Add to dashboard Cite

The authors aimed to get insights into the population structure of non-(sero)typable pneumococci (NTPn), a specific group of natural atypical pneumococci whose identification is often difficult, and which has remained insufficiently studied. A total of 265 presumptive NTPn, isolated between 1997 and 2003 from the nasopharynx of children, were characterized. Strains were confirmed to be pneumococci on the basis of bile solubility, and PCR detection or Southern blotting hybridization of lytA and psaA, genes ubiquitous in this species. Multilocus sequence typing (MLST) was used to exclude two isolates that gave ambiguous results. Non-typability was confirmed by the Quellung reaction using Omniserum. A total of 213 isolates were considered to be true NTPn. The molecular analysis of the true NTPn by PFGE and MLST showed that this population was genetically diverse, although a dominant cluster, accounting for 66 % of the isolates, was identified. Antimicrobial resistance was observed in most genetic backgrounds, and multidrug resistance to penicillin, erythromycin, clindamycin, tetracycline and sulfamethoxazole-trimethoprim was associated with strains belonging to the dominant cluster. Comparison with PFGE fingerprints and sequence types of large collections of serotypable strains showed that the genetic backgrounds of all but two NTPn were different from those found in serotypable strains. In addition, we found that NTPn strains with similar genetic backgrounds to those identified in our study had been isolated from disease sources in other countries. These observations seem to indicate that NTPn have diverse genetic backgrounds and may have evolved as a distinct group of pneumococcal isolates. INTRODUCTIONStreptococcus pneumoniae is a respiratory pathogen that colonizes asymptomatically the nasopharynx of humans. Although the mortality and morbidity associated with pneumococci are high, they are considered to be facultative pathogens: colonization is the rule, and disease the exception (Centers for Disease Control and Prevention, 2000).Most pneumococci are shielded by a polysaccharide capsule, a major virulence factor that hinders phagocytosis. Up to now, at least 90 different capsular types have been described (Henrichsen, 1995). The capsule can be detected by reaction with specific antisera. However, although some isolates are presumptively identified as pneumococci by routine identification tests, a negative result with type-specific antisera for the 90 serotypes is obtained. These atypical isolates are designated non-typable pneumococci (NTPn), and their correct discrimination from commensal viridans streptococci is often difficult (Carvalho et al., 2003;Hanage et al., 2005;Shayegani et al., 1982;Whatmore et al., 2000). The distinction between these closely related species is clinically important, since S. pneumoniae can cause serious disease and viridans streptococci are commensal organisms. Some NTPn have been described as extremely contagious and have been associated with pneumococcal conjunctivitis, causing ...

show abstract

Section: Discussionmentioning

confidence: 99%

Identification, prevalence and population structure of non-typable Streptococcus pneumoniae in carriage samples isolated from preschoolers attending day-care centres

et al. 2006

View full text Add to dashboard Cite

show abstract

“…As Huebner et al report, if the less common serotype represents only 5% of the total pneumococcal population, 59 colonies from each specimen would need to be serotyped to have a 95% probability of picking the second pneumococcal type (10). The need to develop a method that would allow a feasible analysis of minority strains in a pneumococcal population is confirmed by studies on the carriage of multiple pneumococcal capsular types (9,10,24). Preliminary results point to the possibility of using a modified version of our technique to analyze heterogeneous bacterial samples, which would not only eliminate the need to isolate multiple colonies but also give a more realistic perspective on the coexistence of different serotypes in the nasopharynx.…”

Section: Discussionmentioning

confidence: 99%

Serotyping Streptococcus pneumoniae by Multiplex PCR

2003

View full text Add to dashboard Cite

The capsule is a major virulence factor of pneumococci, and it was shown that some capsular variants are associated with antimicrobial resistance and certain types of disease. Moreover, pneumococcal capsular typing has received renewed interest since the availability of conjugate vaccines, which include serotypes frequently associated with pediatric disease. Our aim was to develop a simple, reliable, and economical method for detecting epidemiologically important serotypes present in the proposed 11-valent conjugate vaccine. We designed primers based on the sequences available for the capsular types 1, 3, 4, 6B, 14, 18C, 19F, 19A, and 23F and combined them into seven multiplex PCRs. The method involves streamlined DNA template preparation and agarose gel electrophoresis to analyze the amplification products. A total of 446 pneumococci selected from among isolates colonizing the nasopharynx of children attending day care centers in Lisbon, Portugal, were typed both by conventional immunological techniques and by multiplex PCR. Capsular types identified by the PCR method invariably produced results concordant with the conventional serotyping technique. Even when the method presented does not fully type an isolate, the PCR data can guide the experimenter when using immunological serotyping. Multiplex PCR for the analysis of pneumococci provides an accurate, expeditious, and cost-effective way of reducing the number of strains that have to be serotyped by conventional immunological techniques.

show abstract

“…By picking six to eight colonies from each primary (11) studied an epidemic of pneumococcal pneumonia in an Army Air Force technical school and found that 15% of the subjects simultaneously carried more than one serotype of pneumococcus. In 1980, Gray et al (8) described that more than one serotype of pneumococcus was found in 8% of the cultures of NP samples obtained from 82 children studied from birth to 24 months of life.…”

Section: Discussionmentioning

confidence: 99%

“…Although some studies have described the serotype diversity among carriage pneumococcal isolates in cultures (8,11,12), to our knowledge, only two recent studies have addressed their genetic diversity (16,28). We further characterized the strains isolated from heterogeneous samples for genetic determinants involved with DNA transfer and for susceptibility to lysis by antimicrobial agents.…”

mentioning

confidence: 99%

Pilot Study of the Genetic Diversity of the Pneumococcal Nasopharyngeal Flora among Children Attending Day Care Centers

et al. 2002

View full text Add to dashboard Cite

A pilot study was conducted to determine the genetic diversity of multiple colonies of pneumococci recovered from 37 nasopharyngeal (NP) samples of children. A total of 239 pneumococcal isolates (typically, six to eight colonies per sample) were typed by pulsed-field gel electrophoresis (PFGE). In most NP samples (89%) the multiple colonies shared common PFGE types and serotypes. However, four samples were heterogeneous (samples A through D): each contained two strains with different PFGE types, antibiotypes, and serotypes. Samples A and B each contained one strain of a vaccine capsular type and another expressing a non-vaccine type (according to the currently licensed seven-valent conjugate vaccine). In samples B and C the penicillin MIC for one strain was elevated and the other strain was susceptible. In each of the heterogeneous samples, one of the strains was a representative of an internationally disseminated clone. Samples A, C, and D contained strains which carried prophages that were inducible by mitomycin C and that could be visualized by electron microscopy. The comC gene allele (which encodes the competence-stimulating peptide) was the same in both strains found in each of samples A, B, and D. Carriage of multiple pneumococci with distinct properties should favor genetic exchange and provide a dynamic population structure for pneumococci in their ecological reservoir. Quantitative resolution of majority and minority components of the pneumococcal NP flora will be of importance for evaluation of the impact of intervention strategies such as vaccination or introduction of new antimicrobial agents.Streptococcus pneumoniae is a major cause of morbidity and mortality among young children worldwide (1). With the emergence of antimicrobial resistance in this bacterium, it has become increasingly important to monitor the prevalence of drug-resistant strains carried by young children since the nasopharynx of individuals in this age group is known to be a major reservoir of this bacterial species (13).Several projects are going on worldwide to monitor the prevalence of drug-resistant pneumococci among invasive and carried isolates. In Portugal, since 1996 we have been studying S. pneumoniae strains isolated from nasopharyngeal (NP) samples of a large group of children attending day care centers (4, 26). To evaluate the overall genetic diversity of over 2,000 NP samples we have routinely picked a single colony of pneumococci from each positive sample, and these were characterized for antibiotic susceptibility, serotype, and molecular type (pulsed-field gel electrophoresis [PFGE]). An interesting finding made in those studies was the high prevalence of eight clones that accounted for over half of drug-resistant pneumococci colonizing children attending day care centers (26). Subsequently, each one of the eight epidemic clones was also identified in international samples (24,25).The purpose of the pilot study described in this report was to use molecular typing techniques to determine the homogeneity of S. pneumon...

show abstract

Epidemic Pneumococcal Pneumonia

Cited by 19 publications

References 0 publications

Identification, prevalence and population structure of non-typable Streptococcus pneumoniae in carriage samples isolated from preschoolers attending day-care centres

Identification, prevalence and population structure of non-typable Streptococcus pneumoniae in carriage samples isolated from preschoolers attending day-care centres

Serotyping Streptococcus pneumoniae by Multiplex PCR

Pilot Study of the Genetic Diversity of the Pneumococcal Nasopharyngeal Flora among Children Attending Day Care Centers

Contact Info

Product

Resources

About