Serotype incidence and antibiotic susceptibility of Streptococcus pneumoniae causing invasive disease in Scotland, 1999–2002

Pneumococcal disease remains an important cause of invasive and non-invasive disease in Scotland and elsewhere. The Scottish Meningococcus and Pneumococcus Reference Laboratory receives isolates of Streptococcus pneumoniae from diagnostic laboratories around Scotland. Here, the serogroups/types and antibiotic-susceptibility patterns of invasive isolates received between 1999 and 2002 are described. There were a total of 1741 invasive isolates received, the most common serogroups/types being 14 (19.8 %), 9 (10.2 %), 6 (8.3 %), 19 (7.9 %), 23 (7.9 %), 4 (6.5 %), 8 (6.4 %), 3 (5.7 %), 1 (3.8 %), 7 (3.8 %) and 18 (3.4 %). Importantly, serotypes 7 and 8 are not represented in the 7-, 9- and 11-valent pneumococcal conjugate polysaccharide vaccines. There were 67 (3.8 %) isolates considered penicillin non-susceptible, although no penicillin resistance (MIC ⩾ 0.002 mg ml−1) was recorded. One hundred and ninety-four (11.1 %) isolates, predominantly of serotype 14, were resistant to erythromycin, and 12 (0.7 %) were resistant to ciprofloxacin. This information provides an important dataset that will prove essential prior to and during the implementation of pneumococcal conjugate vaccines in the UK.

Molecular epidemiology of pneumococcal colonization in response to pneumococcal conjugate vaccination in children with recurrent acute otitis media

A randomized double-blind trial with a 7-valent pneumococcal conjugate vaccine was conducted in The Netherlands among 383 children, aged 1 to 7 years, with a history of recurrent acute otitis media. No effect of vaccination on the pneumococcal colonization rate was found. However, a shift in serotype distribution was clearly observed (R. Veenhoven et al., Lancet 361:2189-2195, 2003). We investigated the molecular epidemiology of 921 pneumococcal isolates retrieved from both the pneumococcal vaccine (PV) and control vaccine (CV) groups during the vaccination study. Within individuals a high turnover rate of pneumococcal restriction fragment end labeling genotypes, which was unaffected by vaccination, was observed. Comparison of the genetic structures before and after completion of the vaccination scheme revealed that, despite a shift in serotypes, there was clustering of 70% of the pneumococcal populations. The remaining isolates (30%) were equally observed in the PV and CV groups. In addition, the degree of genetic clustering was unaffected by vaccination. However, within the population genetic structure, nonvaccine serotype clusters with the serotypes 11, 15, and 23B became predominant over vaccine-type clusters after vaccination. Finally, overall pneumococcal resistance was low (14%), and, albeit not significant, a reduction in pneumococcal resistance as a result of pneumococcal vaccination was observed. Molecular surveillance of colonization in Dutch children shows no effect of pneumococcal conjugate vaccination on the degree of genetic clustering and the genetic structure of the pneumococcal population. However, within the genetic pneumococcal population structure, a clear shift toward nonvaccine serotype clusters was observed.

Erythromycin resistance in invasive serotype 14 pneumococci is highly related to clonal type

Sixty-seven serotype 14 pneumococci, isolated from invasive disease in Scotland during the first 6 months of 2003, were characterized. Serotype 14 pneumococci accounted for 18.2 % of the total number of cases. Serotyping, multilocus sequence typing and antibiotic susceptibility testing revealed 10 different sequence types (STs), predominantly ST 9 and ST 124; most ST 9 pneumococci were erythromycin-resistant whilst those of ST 124 were not.

Genetic relatedness of antibiotic-resistant pneumococci isolated during case clusters

Multilocus sequence typing of Streptococcus pneumoniae associated with two case clusters of disease is reported here for the first time. Isolates from the first cluster were serotype 19F, resistant to penicillin and erythromycin, and were characterized as ST 320. Isolates from the second cluster were serogroup 4, resistant to ciprofloxacin, and were characterized as ST 206. Therefore, the isolates from these clusters were antibiotic-resistant, of serotypes infrequently isolated, and of uncommon sequence types.

A single nucleotide polymorphism identification assay for the genotypic characterisation of Neisseria meningitidis using MALDI-TOF mass spectrometry

The ability of matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF) to identify virulent clones of meningococci quickly and accurately is investigated. A single nucleotide polymorphism (SNP) within the fumC gene which differentiates between the hypervirulent ET-15 strain and other ET-37 complex strains is used to determine the usefulness of this method. In this study, MALDI-TOF proved to be a fast, effective alternative to traditional DNA sequencing for the identification of an individual nucleotide.

Serotypes and sequence types of pneumococci causing invasive disease in Scotland prior to the introduction of pneumococcal conjugate polysaccharide vaccines

Pneumococcal conjugate polysaccharide (Pnc) vaccines are now available, and the need for an improved understanding of circulating pneumococcal serotypes and sequence types (STs) is recognized. Three hundred sixty-eight pneumococci isolated in cases of invasive disease in Scotland in the first 6 months of 2003 were analyzed. The isolates belonged to 30 serotypes, and there was a strong correlation between serotype and ST, although only nine serotypes consisted of a single ST. The following serotypes coexisted with the following numbers of STs: serotype 14, 10 STs, serotype 8, 8 STs; serotype 4, 6 STs; serotype 22F, 8 STs; serotype 9V, 7 STs; serotype 23F, 6 STs; serotype 6B, 6 STs; serotype 1, 3 STs; serotype 3, 3 STs; and serotype 7F, 3 STs. Our data also showed a strong association between ST and serotype, although 19 STs contained multiple serotypes. Of the 10 most common STs, 6 coexisted with a single serotype each. Vaccine coverage in all age groups was 94.9% for the 23-valent polysaccharide vaccine and 50.7, 55.4, and 64.1% for the 7-, 9-, and 11-valent Pnc vaccines, respectively. For those under the age of 2 years, 79% coverage would be provided by the 7-, 9-, and 11-valent Pnc vaccines.

The changing pattern of coronary perforation during percutaneous coronary intervention in the new device era

We report the incidence, management and clinical outcome of coronary perforations in 39 of 12,658 patients (0.3%) undergoing percutaneous coronary intervention (PCI). Coronary perforation occurred more frequently with debulking techniques than with non-debulking (percutaneous transluminal coronary angioplasty and stent) techniques (1% versus 0.2%; p<0.001). There were 8 type I (20.5%), 15 type II (38.5%) and 16 type III (41%) perforations. Importantly, fifty-one percent of the coronary perforations were guide-wire related. Major adverse clinical outcomes occurred more frequently in patients who experienced type III perforations. Conventional strategies to treat perforations (i.e., prolonged balloon inflation and reverse of the anticoagulated state) were used. There was one death (2.6%), two emergency surgeries (5.2%) and no Q-wave myocardial infarctions. Pericardial effusion occurred in 18 of 39 patients (46.2%), with cardiac tamponade occurring in 7 patients. In the current device era, the incidence of coronary perforation remains low; it occurs more frequently with debulking devices and is often a consequence of guidewire injury. Its outcome is not affected with the use of IIb/IIIa antagonists. Treatment of coronary perforation requires early detection, angiographic classification, immediate occlusion of coronary vessel extravasation and relief of hemodynamic compromise, reversal of heparin anticoagulation, platelet transfusion in those patients treated with abciximab and cover stents.

Nucleotide sequence analysis of the sialyltransferase genes of meningococcal serogroups B, C, Y and W135

A rapid method for serogrouping meningococci is essential for the characterization of phenotypically non-groupable meningococcal isolates and clinical samples, particularly for public health management purposes. The Scottish Meningococcus and Pneumococcus Reference Laboratory (SMPRL) provides serogrouping results of meningococcal isolates and clinical samples using a PCR assay which detects restriction fragment length polymorphisms in meningococcal serogroups B, C, Y and W135. Although this PCR system was invaluable when first introduced, it has several drawbacks and lacks the required sensitivity for detecting DNA in clinical samples. Due to the recent introduction of the meningococcal group C conjugate vaccine and an impending group B vaccine, a more robust and informative method for serogroup determination is required. A protocol was devised allowing PCR amplification of the siaD gene of serogroup B, C, Y and W135 meningococci. This system was multiplexed and allowed serogroup differentiation between serogroups B and C and also between B/C and Y/W135 by product size analysis. A nested stage was incorporated into the system for enhanced detection of meningococci in clinical samples, and finally a sequencing protocol was designed allowing detection of any nucleotide changes within the siaD gene. This system allows rapid serogrouping results for use within an agarose gel system as well as more informative results when used for sequencing within the siaD gene.

Virulence of enteropathogenic Escherichia coli, a global pathogen

Enteropathogenic Escherichia coli (EPEC) remains an important cause of diarrheal disease worldwide. Research into EPEC is intense and provides a good virulence model of other E. coli infections as well as other pathogenic bacteria. Although the virulence mechanisms are now better understood, they are extremely complex and much remains to be learnt. The pathogenesis of EPEC depends on the formation of an ultrastructural lesion in which the bacteria make intimate contact with the host apical enterocyte membrane. The formation of this lesion is a consequence of the ability of EPEC to adhere in a localized manner to the host cell, aided by bundle-forming pili. Tyrosine phosphorylation and signal transduction events occur within the host cell at the lesion site, leading to a disruption of the host cell mechanisms and, consequently, to diarrhea. These result from the action of highly regulated EPEC secreted proteins which are released via a type III secretion system, many genes of which are located within a pathogenicity island known as the locus of enterocyte effacement. Over the last few years, dramatic increases in our knowledge of EPEC virulence have taken place. This review therefore aims to provide a broad overview of and update to the virulence aspects of EPEC.

Cyclospora cayetanensis infection in Lagos, Nigeria

Although reports of Cyclospora infection continue to increase globally, few cases have been reported from the African continent. We present 11 cases of cyclosporiasis detected from stool samples submitted to seven major hospital laboratories in Lagos, Nigeria between March 1999 and April 2000.

Analysis of PorA variable region 3 in meningococci: implications for vaccine policy?

Outer membrane protein (OMP) vaccines are being developed against Neisseria meningitidis serogroup B which may provide protection against common circulating serotypes and serosubtypes in some countries. However, limited data is available in Europe from genosubtyping meningococci. We therefore undertook a retrospective analysis of the three main variable regions, VR1, VR2 as well as VR3, of the porA gene from N. meningitidis isolated from different countries, mainly from Scotland and Sweden. Analysis of this gene showed that, amongst 226 strains studied, there were a total of 78 different strains. No new VR1 or VR2 alleles were found but five new VR3 alleles are described. Our data indicates the importance of analysing the VR3 region of PorA in addition to VR1 and VR2 and also highlights, in general terms, the need for genosubtyping meningococci. Such analyses have major implications for the design of new meningococcal vaccines.

Comparison of commercial DNA extraction kits for extraction of bacterial genomic DNA from whole-blood samples

The demand for molecular diagnostic tests in medical microbiology has highlighted the need for efficient methods of DNA extraction. In addition, it is preferable for these methods to be automated. An example of such a requirement is for the confirmation of meningococcal disease where rapid, sensitive, and specific procedures are required for public health management purposes. Previous studies have shown that whole blood is the preferred method for the isolation of bacterial DNA in meningococcal disease, and in this study, we compare five commercially available kits for the extraction of bacterial genomic DNA from whole-blood samples. These include kits in a 96-well binding plate, 96-well filter plate, and metallic bead formats. The method for all five kits is described, and the sensitivity, specificity, ease of automation, and overall efficiency are determined.

Identification of Neisseria meningitidis serogroups Y and W135 by siaD nucleotide sequence analysis

Rapid serogrouping of meningococci is essential for the effective public health management of cases of the disease and the contacts of infected patients. Here we describe an accurate nucleotide-sequencing method for the confirmation of serogroup Y and W135 meningococci by siaD gene analysis from cultures of Neisseria meningitidis.

Bioterrorism: an overview

Bioterrorism has reached the forefront of the public imagination following recent events across the world. The disaster of 11 September 2001, followed by anthrax letters sent via the US postal system and now renewed tension over Iraq have all brought the possibility of bioterrorism closer. A number of biological agents could be used in a terrorist attack, including anthrax, plague, smallpox and botulinum toxin. The serious diseases that these agents produce have been brought under control in the developed world; however, a lack of protective immunity against such diseases could cause considerable morbidity and mortality if used in a terrorist attack. This essay provides a background to bioterrorism, discusses many of the current points of interest and gives an update to the economic consequences of such an attack.

Evaluation of a fluorescence-based PCR method for identification of serogroup a meningococci

Standard and fluorescence-based PCR assays were developed for the identification of serogroup A meningococci by detection of the mynA gene. This assay was evaluated using bacterial cultures but provides the sensitivity required for the detection of the mynA gene from bodily fluids during meningococcal disease.

Percutaneous myocardial laser revascularization in patients with refractory angina pectoris

This study aimed to determine the safety and efficacy of percutaneous myocardial laser revascularization (PMLR). Seventy-three patients with stable angina pectoris (class III or IV) who were unsuitable for conventional revascularization and had evidence of reversible ischemia by thallium-201 scintigraphy, ejection fraction of > or =25%, and myocardial wall thickness > or =8 mm were randomized to optimal medical therapy alone (n = 37) or PMLR with optimal medical therapy (n = 36). Patients were followed up at 3, 6, and 12 months. The primary end point was exercise time. Secondary end points included angina scores, left ventricular ejection fraction, quality of life, changes in medical therapy, and hospitalizations. All 36 patients randomized to PMLR underwent the procedure successfully with no periprocedure deaths. One patient developed sustained ventricular tachycardia that required electrical cardioversion, and 1 patient developed cardiac tamponade that required surgical drainage. At 12 months, exercise times improved by 109 seconds in the PMLR group but decreased by 62 seconds in the control group (p <0.01). Angina scores improved by 2 classes in 36% of PMLR-treated patients at 12 months compared with 0% of the control patients (p <0.01). We conclude that PMLR is a relatively safe procedure that provides patients with symptomatic angina relief and improvement in exercise capacity and quality of life.

Detection and genotyping of meningococci using a nested PCR approach

An effective vaccine against Neisseria meningitidis serogroup B is required. Outer-membrane protein vaccines have been developed, which may provide protection against common circulating serotypes and serosubtypes in some countries. However, limited genosubtyping data are available because most laboratories use mAbs directed against a limited number of specific serotypes and serosubtypes and laboratories do not genosubtype directly from body fluids due to the lack of a sensitive PCR method. A nested PCR was therefore developed that enables the amplification of the porA gene directly from clinical samples and has the required sensitivity for nucleotide sequencing of the three main variable regions, VR1, VR2 and VR3. Data were compared with those from culture-based nucleotide sequencing, and the use of this method increased the availability of genosubtype information by 45 %, thereby indicating the impact that this methodology has on the data provided and the implications for vaccine design.

Cyclospora cayetanensis in stools submitted to hospitals in Lagos, Nigeria

BACKGROUND

Cyclospora cayetanensis is an emerging human pathogen associated with gastrointestinal disease. The epidemiology and biology of the parasite are poorly understood, and numerous outbreaks of cyclosporiasis have been recorded from around the world since 1990, but the incidence of the parasite in Nigeria has not been described.

DESIGN AND METHODS

A cross-sectional, laboratory-based study was conducted in Lagos-metropolis state in southwestern Nigeria. All stool samples submitted to the Microbiology and Parasitology Department between March 1999 and April 2000 were processed for the presence of Cyclospora cayetanensis. Data from each patient were obtained from health records and via questionnaires, including age, sex and reason for hospital visit.

RESULTS

In total, 1109 stool samples were collected during the period of study. Eleven (0.99%) were confirmed to be positive for Cyclospora cayetanensis oocysts. Other parasites were also detected, including Cryptosporidium sp., Entamoeba sp., Ascaris, Trichuris, Strongyloides sp., and hookworm.

CONCLUSIONS

Cyclospora cayetanensis is an infrequent but important cause of gastrointestinal disease in Lagos, Nigeria. This is the first report of Cyclospora infection in Nigeria and suggests that medical practitioners and laboratory scientists should be made more aware of the infection.

Clinical aspects of pneumonia

Pneumonia is a serious medical condition and a major cause of morbidity and mortality worldwide. It has many infectious aetiologies, although bacterial and viral forms are most common. Our understanding of pneumonia has improved significantly during the course of the 20th century but the overall disease burden has changed little. Although antibiotics have helped to reduce the mortality associated with some types of pneumonia, the level of morbidity remains constant. Furthermore, the existence of antibiotic-resistant bacteria worldwide is becoming an increasing problem in treatment. This essay describes the different types of pneumonia from a clinical perspective and highlights the problems associated with the condition.

Semi-automation of the polymerase chain reaction for laboratory confirmation of meningococcal disease

Demand for accurate high-throughput detection and characterisation of medically important bacteria has increased dramatically within research and clinical laboratories. Liquid-handling robots have been developed to achieve high levels of accuracy and reproducibility. Assay automation can play a key role in the modern diagnostic laboratory and the data presented here shows that automated PCR is comparable with manual methods. Importantly, automation is preferred when high-quality results cannot be guaranteed using manual methods. This is particularly important when results are required quickly for public health management.