- Volume 57, Issue 11, 2008

Scientific knowledge of meningococcal infection has increased greatly since the epidemic nature of the illness was first described by Vieusseux at the dawn of the nineteenth century. In fact, revolutionary advances have been made in public-health measures, antimicrobial therapy, diagnostic procedures, anti-inflammatory drugs and supportive care facilities. Based on the knowledge accumulated to date, it is generally accepted that the pathogenesis of meningococcal infection involves multiple links that interconnect in a complex web of phenomena from Neisseria meningitidis attachment to meningococcal sepsis or meningitis. In fact, a myriad of strongly interacting inflammatory molecules and cells have been implicated in neisserial infection, illustrating the complexity of meningococcal pathogenesis. In addition, many of these signallers are critically involved in outcomes in the human host. Deciphering the pathogenesis of meningococcal infection could expand our knowledge and provide important clues to the host–pathogen interaction, as well as leading to the development of new therapeutic tools. Herein, we review the history of the discovery and characterization of meningococcal disease, epidemiological features of the disease with an emphasis on recent developments in Brazil, the cellular and molecular basis of disease, and discuss diagnosis and therapy.

Penicillium marneffei is an intracellular dimorphic fungus that can cause a fatal disseminated disease in human immunodeficiency virus-infected patients. The factors that affect the pathogenicity of this fungus remain unclear. Here, we report the isolation and characterization of the gpdA cDNA and genomic clones encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in P. marneffei. Phylogenetic analysis of GAPDH amino acid sequences demonstrated the evolutionary relationship of P. marneffei to other fungi, including the intracellular pathogen Ajellomyces capsulatus. To assess the central importance of phagocytic cells in defence against P. marneffei infection, we used Northern blotting to investigate the response of the isocitrate lyase-encoding gene (acuD) and gpdA to nutrient deprivation inside macrophages. The results revealed that after macrophage internalization, the gene involved in the glyoxylate cycle, acuD, showed higher expression levels as early as 2 h from the start of co-incubation, and the differential expression could be observed again at 8 h after infection. In contrast, the expression of gpdA was downregulated in the yeast phase, as well as during macrophage infection after 2, 4 and 8 h of infection. The induction of P. marneffei acuD was shown to be coordinated with the downregulation of the glycolytic gpdA gene, implying that the cytoplasmic environment of macrophages is deficient in glucose and the glyoxylate pathway could be used by this pathogen to allow subsistence on two-carbon compounds within the host cell following its intracellular persistence.

In the present study, we examined the roles of natural killer T (NKT) cells in host defence against Legionella pneumophila in a mouse model. The survival rate of NKT cell-deficient Jα281 knock-out (KO) mice was significantly higher than that of wild-type mice. There was no bacterial overgrowth in the lungs, but Jα281 KO mice showed enhanced pulmonary clearance at a later stage of infection, compared with their wild-type counterparts. The severity of lung injury in L. pneumophila-infected Jα281 KO mice was less, as indicated by lung permeability measurements, such as lung weight and bronchoalveolar lavage fluid albumin concentration. Recruitment of inflammatory cells in the lungs was approximately twofold greater in Jα281 KO mice on day 3. Interestingly, higher values of interleukin (IL)-1β and IL-18, and increased caspase-1 activity were noted in the lungs of Jα281 KO mice from an early time point (6 h). Exogenous α-galactosylceramide, a ligand of NKT cells, induced IL-12 and gamma interferon at 6 h, but suppressed IL-1β at later time points in wild-type, whereas no effects were evident in Jα281 KO mice, as expected. Systemic administration of heat-killed L. pneumophila, but not Escherichia coli LPS, reproduced exaggerated production of IL-1β in the lungs of Jα281 KO mice. These results demonstrate that NKT cells play a role in host defence against L. pneumophila, which is characterized by enhanced lung injury and decreased accumulation of inflammatory cells in the lungs. The regulation of IL-1β, IL-18 and caspase-1 may be associated with the modulating effect of host responses by NKT cells.

The TUBEX test for typhoid fever detects serum antibodies in a simple and rapid assay system based on the inhibition of binding between two types of reagent particles — magnetic particles coated with an antigen (Salmonella O9 LPS) and coloured indicator particles coated with an anti-O9 mAb. A magnet is used to separate the colour indicator particles bound to the magnetic particles from the unbound indicator particles. Specific colour changes following magnetic separation are indicative of antibodies in the patient's serum; however, because results are interpreted based on changes in the colour red, haemolytic or icteric specimens cannot be used. This study describes a simple modification of the protocol to accommodate such specimens, including whole blood. This involves the addition of a quick and simple washing step after mixing the specimen with the antigen-bound magnetic particles. This modification has the advantage of allowing larger sample volumes to be used, thus enhancing the assay sensitivity, and also enables cases considered to be borderline positive by the original method to be re-assessed.

To determine the prevalence of macrolide antibiotic and levofloxacin resistance in infections with Streptococcus pyogenes (group A streptococcus or GAS), strains were collected from 45 medical institutions in various parts of Japan between October 2003 and September 2006. Four hundred and eighty-two strains from patients with GAS infections were characterized genetically. Strains were classified into four groups according to the type of infection: invasive infections (n=74) including sepsis, cellulitis and toxic-shock-like syndrome; acute otitis media (AOM; n=23); abscess (n=53); and pharyngotonsillitis (n=332). Among all strains, 32 emm types were identified; emm1 was significantly more common in invasive infections (39.2 %) and AOM (43.5 %) than in abscesses (3.8 %) or pharyngotonsillitis (10.2 %). emm12 and emm4 each accounted for 23.5 % of pharyngotonsillitis cases. Susceptibility of GAS strains to eight β-lactam agents was excellent, with MICs of 0.0005–0.063 μg ml−1. Macrolide-resistant strains accounted for 16.2 % of all strains, while the percentages of strains possessing the resistance genes erm(A), erm(B) and mef(A) were 2.5 %, 6.2 % and 7.5 %, respectively. Although no strains with high resistance to levofloxacin were found, strains with an MIC of 2–4 μg ml−1 (17.4 %) had amino acid substitutions at either Ser-79 or Asp-83 in ParC. These levofloxacin-intermediately resistant strains included 16 emm types, but macrolide-resistant strains were more likely than others to represent certain emm types.

From 1997 to 2007, the Laboratory of Enteric Pathogens (LEP), Health Protection Agency, UK, received sera from 2148 patients for testing for antibodies to the LPS of verocytotoxin-producing Escherichia coli (VTEC) O157. A total of 676 (31.5 %) sera had antibodies binding the LPS of E. coli O157 and the majority of patients were below the age of 10 years, a trend observed for both males and females. Antibody-positive patients had haemolytic uraemic syndrome (HUS) in 79.3 % of cases and most of these presented with the atypical (D−) form of HUS. Nine patients were shown to have antibodies to the LPS of E. coli belonging to serogroups O26 (4), O103 (2), O111 (1) and O145 (2) and one patient had antibodies to the somatic antigens of both E. coli O26 and O103. The serodiagnosis of infections with E. coli O157 and other VTEC continues to be an important adjunct to bacteriology. Where clinicians suspect the involvement of a VTEC in disease, patients' sera should be submitted to the LEP for analysis without delay.

Pathogenic strains of the genus Acanthamoeba are causative agents of a serious sight-threatening infection of the eye known as Acanthamoeba keratitis. The prevalence of this infection has risen in the past 20 years, mainly due to the increase in number of contact lens wearers. In this study, the prevalence of Acanthamoeba in a risk group constituted by asymptomatic contact lens wearers from Tenerife, Canary Islands, Spain, was evaluated. Contact lenses and contact lens cases were analysed for the presence of Acanthamoeba isolates. The isolates' genotypes were also determined after rDNA sequencing. The pathogenic potential of the isolated strains was subsequently established using previously described molecular and biochemical assays, which allowed the selection of three strains with high pathogenic potential. Furthermore, the sensitivity of these isolates against two standard drugs, ciprofloxacin and chlorhexidine, was analysed. As the three selected strains were sensitive to chlorhexidine, its activity and IC50 were evaluated. Chlorhexidine was found to be active against these strains and the obtained IC50 values were compared to the concentrations of this drug present in contact lens maintenance solutions. It was observed that the measured IC50 was higher than the concentration found in these maintenance solutions. Therefore, the ineffectiveness of chlorhexidine-containing contact lens maintenance solutions against potentially pathogenic strains of Acanthamoeba is demonstrated in this study.

Campylobacter fetus subsp. fetus infection can occur in female sheep, causing infertility or abortion. Despite extensive research on the effect of these bacteria on female fertility, little research has been done on the influence of C. fetus subsp. fetus on the male factor. Our objective was to examine the influence of C. fetus subsp. fetus on ram sperm. Motility index, percentage of live spermatozoa, mean αt value (an indication of the chromatin stability of the sperm cell) and percentage of sperm cells expressing the FAS receptor were measured in sperm incubated in the presence or absence of C. fetus subsp. fetus. The motility index and viability of sperm incubated with the bacteria were lower than those of untreated sperm samples after 5 h. In bacteria-incubated sperm cells, the percentage expressing FAS receptor was already significantly elevated at 15 min. Bacteria-incubated sperm showed a greater prevalence of morphological damage. The bacteria were attached to tail and acrosome regions, and the sperm damage was concentrated in both the motility and chromatin regions. Bacteria-infected sperm cells showed a decrease in motility, increase in early acrosome reaction and chromatin damage. Similar effects were induced by incubation of the sperm with supernatants from C. fetus subsp. fetus cultures. Thus this study demonstrates that C. fetus subsp. fetus has a detrimental effect on the quality of ram sperm.

Hydrogen sulfide (H2S) is a toxic gas that induces the modification and release of haemoglobin in erythrocytes; however, it also functions in methionine biosynthesis in bacteria. βC–S lyase, encoded by the lcd gene, is responsible for bacterial H2S production through the cleavage of l-cysteine. In this study, 26 of 29 crude extracts from reference and clinical strains of Streptococcus intermedius produced H2S from l-cysteine. The capacities in those strains were not higher than those in strains of the other anginosus group of streptococci, Streptococcus anginosus and Streptococcus constellatus, but were much greater than those in strains of Streptococcus gordonii, which is known to have an extremely low capacity for H2S production. Incubation of the remaining three extracts with l-cysteine did not result in H2S production. Sequence analysis revealed that the lcd genes from these three strains (S. intermedius strains ATCC 27335, IMU151 and IMU202) contained mutations or small deletions. H2S production in crude extracts prepared from S. intermedius ATCC 27335 was restored by repairing the lcd gene sequence in genomic DNA. The kinetic properties of the purified recombinant protein encoded by the repaired lcd gene were comparable to those of native proteins produced by H2S-producing strains, whereas the truncated protein produced by S. intermedius ATCC 27335 had no enzymic activity with l-cysteine or l-cystathionine. However, real-time PCR analysis indicated that the lcd gene in strains ATCC 27335, IMU151 and IMU202 is transcribed and regulated in a manner similar to that in the H2S-producing strain.

Alveolar echinococcosis (AE) of the liver with cerebral and pulmonary metastasis was diagnosed in a Tibetan monk who initially presented with severe headache to an emergency department in Germany. Multiple lesions with perifocal oedema and severe compression of the third ventricle were seen with computed tomography (CT) of the brain. Glioma or cerebral metastasis of a hitherto undiagnosed abdominal or pulmonary malignancy was suspected. CT scans of the lung and liver demonstrated further tumorous masses. Magnetic resonance imaging of the brain revealed the cystic nature of the cerebral lesions and the patient had a highly positive serology for AE. The echinococcal aetiology of the brain lesions was confirmed by PCR for this refugee from an area where two disease entities, AE and cystic echinococcosis, are hyperendemic.