E R Moxon

Detection of Pneumocystis carinii with DNA amplification.

Oligonucleotide primers and probes were used in the polymerase chain reaction to amplify Pneumocystis carinii specific DNA sequences from alveolar lavage samples from 47 diagnostic bronchoscopies. No P carinii DNA was found in lavage from 10 immunocompetent patients; only low levels were found in 3 of 13 samples from immunosuppressed individuals without P carinii pneumonia (PCP), and the highest levels, readily demonstrated by simple ethidium bromide staining, were found in all of 16 samples from immunosuppressed patients with PCP confirmed by means of standard silver staining and in 4 from patients with clinical PCP but negative silver staining. DNA amplification provides a highly sensitive and specific technique for the identification of P carinii that should be valuable in epidemiological studies on this parasitic infection and in diagnosis.

Amplification of mitochondrial ribosomal RNA sequences from Pneumocystis carinii DNA of rat and human origin

Pneumocystis carinii specific DNA sequences have been cloned from the experimental rat model. The sequence of the gene coding for the large subunit of mitochondrial ribosomal RNA has been used to construct P. carinii specific oligonucleotide primers for the polymerase chain reaction. These oligonucleotides produced amplification of specific sequences from both P. carinii infected rat and human lung samplings, but none from a range of other organisms including potential pulmonary pathogens. Comparison of the sequence of amplified products from the infected rats and humans demonstrated limited but consistent differences between P. carinii from these two hosts and allowed for the construction of a human specific internal oligonucleotide. The application of the specific oligonucleotides for DNA amplification and subsequent Southern hybridisation affords extremely sensitive and specific detection of P. carinii in human samples, which may be applicable to both epidemiological research and clinical studies.

Underestimation of meningococci in tonsillar tissue by nasopharyngeal swabbing

The relation between carriage of Neisseria meningitidis and progression to invasive disease is not fully understood. We assessed the rate of N. meningitidis carriage by conventional swabbing and immunohistochemistry in patients undergoing tonsillectomy. Swabbing detected only a quarter of carriers, and bacteria were identified beneath the mucosal surface in tonsillar tissue by immunochemical testing. Our results indicate that N. meningitidis is more widespread in the population than previously thought, and have broad implications for disease prevention and cure.

Lack of serum bactericidal activity in preschool children two years after a single dose of serogroup C meningococcal polysaccharide-protein conjugate vaccine.

Background: There is an increased risk of invasive meningococcal disease during the teenage years. A cohort of children vaccinated with a single dose of meningococcal C protein-polysaccharide conjugate (MenC) vaccine in early childhood during the U.K. catch up campaign will enter this age group during the coming decade. The duration of protective immunity against invasive meningococcal C disease provided by this single dose regimen is uncertain. A serum bactericidal titer of <1/8 correlates with susceptibility to invasive meningococcal disease. We assessed this correlate of protection in a cohort of children ∼2 years after a single dose of vaccine. Methods: Serum bactericidal activity was assessed in 94 children (median age, 4.0 years) at a median time of 1.8 years after vaccination. Results: Of the 94 children, 59 (63%) had a serum bactericidal titer <1/8. Conclusion: The data from this study add to previous evidence indicating that immunity wanes rapidly after vaccination with serogroup C meningococcal glycoconjugate vaccines in infancy and early childhood. Such observations suggest that booster doses of MenC vaccine may be needed to maintain the successful contribution this vaccine has made to child health in the United Kingdom.

Population-based study of non-typable Haemophilus influenzae invasive disease in children and neonates

The extent of non-capsulate, non-serotypable Haemophilus influenzae (NST) as a cause of serious invasive disease in children has not been fully defined. We describe the epidemiology of these childhood infections from cases identified during a continuing prospective survey of invasive H influenzae disease in the Oxford region, UK. 408 strains of H influenzae were isolated from cases of invasive disease. 383 (94%) were H influenzae type b (Hib), 24 (6%) were NST strains, and 1 was a type f strain. 3 of the NST strains were non-capsulate type b mutants (b-), but the remaining 21 strains were from the phylogenetically distinct and heterogeneous population of non-capsulate H influenzae (NC). 10 of the NC strains were isolated from neonates with sepsis; crude mortality rate was 40%, with an incidence of 4.6 cases per 100,000 livebirths. 11 NC strains were isolated from children after the neonatal period and under 10 years of age, 4 (36%) of which had severe, unrelated, predisposing conditions. The incidence of NC invasive diseases in these children was 0.5 per 100,000 per year. The attributable mortality for these infections was 10%. Infections due to these H influenzae strains are, after the implementation of Hib vaccines, likely to persist and represent a substantial proportion of the serious infections caused by this species.

The Role Familiarity With Science and Medicine Plays in Parents’ Decision Making About Enrolling a Child in Vaccine Research:

Parental consent to children’s participation in vaccine research has resulted in the licensure of essential vaccines. Recruitment to this type of research is typically difficult, however, and many parents decline. In this study, the authors interviewed parents about their decision for or against enrolling their child in a vaccine study. The data analysis suggests that parents’ ability to evaluate a vaccine study depends on how attuned they are with science and medicine, either professionally or as consumers of health services. Familiarity does not predispose parents to enrolling their child in research; rather, it is a predictor of parents’ confidence in their decision making. Many parents were motivated by altruism and trust, which, if uninformed, can leave the parents prone to exploitation. It is vital to ensure that parents are confident in their judgment of a study and its potential benefit to their child and society.

Immunogenicity and immunologic memory of meningococcal C conjugate vaccine in premature infants.

Background: Protein-polysaccharide conjugate vaccines against Neisseria meningitidis serogroup C were introduced into the U.K. routine immunization schedule in 1999. This study is the first to describe both persistence of antibody and evidence for induction of immune memory using meningococcal C conjugate (MCC) vaccine in preterm infants. Methods: Immunogenicity and induction of immunologic memory by as MCC vaccine was assessed in premature infants; 62 preterm and 60 term controls received MCC at the accelerated schedule (2, 3 and 4 months of age). A meningococcal C polysaccharide challenge was administered at 12 months of age. Results: Both groups achieved similar protective titers after primary immunization that then waned significantly by 1 year of age. Postchallenge serum bactericidal activity was significantly lower in preterm infants (P = 0.03); 73% of preterm versus 88% of term controls achieved a 4-fold rise in serum bactericidal activity (P = 0.07). Conclusions: MCC vaccine is immunogenic and primes for immunologic memory in preterm infants. The decreased memory responses in these preterm infants in conjunction with waning clinical efficacy data for all U.K. infants suggest a role for a routine booster dose of vaccine in all infants receiving MCC, especially those born preterm.

CONSERVATIVE MANAGEMENT OF AN ECHOVIRUS 11 OUTBREAK IN A NEONATAL UNIT

Two babies in a neonatal unit presented on the same day with meningitis due to echovirus 11, which was thought to have been introduced by staff. At this time echovirus 11 was also isolated from the stools of eight other babies; five of them did not have signs of infection. No intervention was made except to emphasise the importance of handwashing. There was evidence of secondary spread to two babies who were both clinically well. The attack rate was twelve (29%) of forty-one babies exposed. Seven of the twelve infected babies were born before 30 weeks gestation and would have had little or no maternal antibody, yet only two of the seven babies had signs of infection. Despite lack of special measures, all babies recovered. Most cases of horizontally acquired neonatal echovirus infection are mild: extreme measures in the management of outbreaks are unnecessary.

Anti-Polyribosylribitol Phosphate Antibody Concentrations and Avidities in Children since the Start of Haemophilus influenzae Type b Immunization of Infants in the United Kingdom

ABSTRACT The introduction of routine infant immunization with Haemophilus influenzae type b (Hib) conjugate vaccines in the United Kingdom in 1992 led to a significant reduction in invasive disease due to this organism. Subsequently, between 1999 and 2003 there was an increase in the number of immunized children with Hib infection. We investigated whether the rise in cases was related to changes in anti-polyribosylribitol phosphate (PRP) antibody concentration or avidity. Using stored sera, we analyzed temporal changes in antibody levels among 3- to 5-year-old children immunized between 1991 and 2000. Anti-PRP antibody concentrations were higher in 3- to 5-year-olds who received infant immunization in 1991 than those in subsequent years. This difference may be related to changes in either the mode of administration of Hib conjugate vaccines or the rates of Hib nasopharyngeal carriage. This study emphasizes the factors affecting anti-PRP antibody concentration following immunization with conjugate vaccines and the importance of these in long-term protection from invasive disease.