Outbreak of serogroup C meningococcal disease caused by a variant of Neisseria meningitidis serotype 2a ET-15 in a community of men who have sex with men

We describe an outbreak, in a community of men who have sex with men, of serogroup C meningococcal disease caused by a genetic variant of the serotype 2a ET-15 Neisseria meningitidis characterized by a point mutation in the gene coding for the serotype 2a antigen. A microbiological characterization of the outbreak strain is presented in this report.     

Protection against infection with Neisseria meningitidis group B serotype 2b by passive immunization with serotype-specific monoclonal antibody

Hybridomas derived from mice immunized with Neisseria meningitidis serogroup B serotype 2b (B,2b) outer membrane preparations produced monoclonal antibodies (MAbs) specific for major outer membrane proteins of classes 1, 2, and 5. The MAbs were examined by enzyme-linked immunosorbent assay against a selected panel of seven strains of N. meningitidis (B,2b) of different sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns, a serotype 2a, and a nontypable strain. The five MAbs selected were all bactericidal and of different immunoglobulin subclasses. None of the MAbs reacted with other bacterial strains in a dot-enzyme immunoassay. The corresponding antigenic determinant for each MAb was localized on a specific outer membrane protein by immunoblotting of sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns of major outer membrane proteins. MAbs M5-11 and M5-30 bound to the class 2 protein and were serotype 2b specific. MAb M2-20 bound to the class 1 protein, and MAbs M5-16 and M5-19 bound to the class 5 protein. A mouse model of infection was established whereby a local infection progressed to lethal bacteremia over 3 days, and 50% of the animals were killed with an intraperitoneal injection of 10 meningococci plus 4% mucin and 1.6% hemoglobin. The ability of the MAbs to provide passive protection against experimental infection with N. meningitidis (B,2b) was examined. Both serotype-specific MAbs M5-11 and M5-30 were highly protective even though they were of different immunoglobulin subclasses. The class 5-specific MAb offered no protection, while the class 1-specific MAb gave limited protection. It may therefore be possible to provide protection against serotype 2b infection by using as vaccine the class 2 serotype-specific surface-exposed outer membrane protein epitopes defined by MAb M5-11 or M5-30.     

Systemic oxidative and antioxidative status in Chinese patients with asthma

BACKGROUND: Patients with asthma generate an increased amount of reactive oxygen species from peripheral blood cells. Reactive oxygen species produce many of the pathophysiologic changes associated with asthma and may contribute to its pathogenesis. OBJECTIVE: We investigated changes in antioxidant enzyme activities and oxidized glutathione (glutathione disulfide; GSSG) levels in erythrocytes from a group of healthy control Chinese subjects (n=135) and patients with asthma (n=106). METHODS: Baseline pulmonary function was measured for all subjects. Antioxidant status was evaluated by measuring erythrocyte superoxide dismutase, catalase, and glutathione peroxidase activities. Oxidative stress was also measured in terms of GSSG in erythrocytes with a kinetic microassay. RESULTS: Patients with asthma had significantly increased erythrocyte superoxide dismutase and catalase activities compared with controls (61.10 +/- 1.30 U/g hemoglobin [Hb] vs 55.51 +/- 1.82 U/g Hb [P=.018] and 0.0637 +/- 0.0021 U/g Hb vs 0.0257 +/- 0.0120 U/g Hb [P <.001] for the asthma and control groups, respectively). Conversely, erythrocyte glutathione peroxidase activity decreased (44.21 +/- 1.33 mU/g Hb vs 50.07 +/- 1.39 mU/g Hb for the asthma and control groups, respectively; P=.003). Patients with asthma also had significantly higher GSSG levels in erythrocyte hemolysates compared with controls (167.40 +/- 2.93 micromol/L vs 44.98 +/- 0.44 micromol/L for the asthma and control groups, respectively; P <.001), indicating increased oxidative stress. CONCLUSIONS: Asthma is accompanied by an alteration in systemic antioxidant status due to possible oxidative stress in this disease.     

Intimin from enteropathogenic Escherichia coli restores murine virulence to a Citrobacter rodentium eaeA mutant: induction of an immunoglobulin A response to intimin and EspB.

The formation of attaching and effacing (A/E) lesions is central to the pathogenesis of enteropathogenic Escherichia coli (EPEC)-mediated disease in humans and Citrobacter rodentium (formerly C. freundii biotype 4280)-mediated transmissible colonic hyperplasia in mice. Closely related outer membrane proteins, known as intimins, are required for formation of the A/E lesion by both EPEC (Int(EPEC)) and C. rodentium (Int(CR)). A secreted protein, EspB (formally EaeB), is also necessary for A/E-lesion formation. Here we report that expression of a cloned Int(EPEC), encoded by plasmid pCVD438, restores murine virulence to an intimin-deficient mutant of C. rodentium DBS255. Replacement of Cys937 with Ala abolished the ability of the cloned EPEC intimin to complement the deletion mutation in DBS255. Ultrastructural examination of tissues from wild-type C. rodentium and DBS255(pCVD438)-infected mice revealed multiple A/E lesion on infected cells and loss of contact between enterocytes and basement membrane. Histological investigation showed that although both wild-type C. rodentium and DBS255(pCVD438) colonized the descending colon and induced colonic hyperplasia in orally infected 21-day-old mice, the latter strain adhered to epithelial cells located deeper within crypts. Nonetheless, infection with the wild-type strain was consistently more virulent, as indicated by a higher mortality rate. All the surviving mice, challenged with either wild-type C. rodentium or DBS255(pCVD438), developed a mucosal immunoglobulin A response to intimin and EspB. These results show that C. rodentium infection provides a relevant, simple, and economic model to investigate the role of EPEC proteins in the formation of A/E lesions in vivo and in intestinal disease.     

Comparison of screening methods for detection of extended-spectrum beta-lactamases and their prevalence among Escherichia coli and Klebsiella species in Hong Kong

Three tests, the disk diffusion test, the double-disc synergy test and the inhibitor-potentiated disc diffusion test, were compared for their abilities to detect production of extended-spectrum beta-lactamases (ESBL) in 702 Escherichia coli and 472 Klebsiella spp. strains from four hospitals. Eleven percent E. coli and 13% Klebsiella spp. were found to produce ESBL. As an indicator of ESBL activity, the sensitivities of the five extended-spectrum beta-lactams were as follows: cefotaxime (100%), cefpodoxime (99.3%), ceftriaxone (98.6%), aztreonam (93%) and ceftazidime (57.7%) when interpreted using the National Committee for Clinical Laboratory Standards criteria. Their positive predictive values ranged from 67.8-83.8%. Both the inhibitor-potentiated disc diffusion test and the double-disc synergy test (at three inter-disc widths of 20, 25 and 30 mm) were capable of identifying all the ESBL-producers. However, at a single inter-disc width of 30 mm, the double-disc synergy test has limited sensitivity (83.8%). As a second test for confirming ESBL activity in strains with reduced susceptibility to beta-lactams, the inhibitor-potentiated disc diffusion test is therefore a simple and reliable option.     

Mycobacterium avium complex pseudobacteriuria from a hospital water supply.

From July 1983 through November 1985, organisms belonging to Mycobacterium avium complex were isolated from the urine of 29 patients. Strains recovered from the urine of nine patients from July 1983 through August 1984 were serotyped. Eight of the nine samples belonged to serovar 4. M. avium complex was isolated from the urine of 21 patients during the period from November 1984 through November 1985. While the possibility of a point source contamination was investigated, M. avium complex was recovered from the phenol red solution used for processing urine specimens in the mycobacteriology laboratory and the deionized tap water of that laboratory that is used to make the reagent. M. avium complex serovar 4 was subsequently recovered from the tap water of the laboratory and four hospital wards. During the year following the installation of a microbiological filter for the mycobacteriology laboratory deionized tap water, 2 urine isolates were recovered, compared to 26 the previous year. This study demonstrates the importance of filtration devices at tap water sites that are used to make laboratory reagents and the value of serotyping as a marker for the detection of a specific source of M. avium complex contamination.     

Crossed immunoelectrophoretic analysis of anti-Salmonella typhi antibodies in sera of typhoid patients and carriers: demonstration of the presence of typhoid-specific antibodies to a non-O, non-H, non-Vi antigen

A veronal buffer extract of Salmonella typhi was used as the reference antigen and its corresponding rabbit antiserum as the reference antibody in crossed immunoelectrophoresis to analyze antibodies in sera obtained from typhoid patients and carriers. Four precipitating antibodies were regularly detected. Three were against antigens common to other gram-negative bacteria and one appeared to be typhoid specific. Of the three common antigens, one (antigen no. 7) formed a precipitin resembling in mobility and morphology the lipopolysaccharide antigen seen in crossed immunoelectrophoresis analysis of other gram-negative bacteria. The other (antigen no. 19) was heat labile and antigenically similar to the reported common antigen of Pseudomonas aeruginosa. The third (antigen no. 14), also heat labile, was present in members of the family Enterobacteriaceae but not the family Pseudomonas. The typhoid-specific precipitating antibody present in sera of most typhoid patients and carriers but not patients infected with nontyphoid salmonella was directed to a heat-labile, non-O, non-H, and non-Vi antigen (antigen no. 28), probably protein in nature.     

Flagella as a potential marker for Campylobacter jejuni strains associated with Guillain-Barré syndrome

Campylobacter jejuni recovered from patients with Guillain-Barré syndrome (GBS) in different geographical locations and bearing different heat-labile and heat-stable antigens were found to have identical amino acid sequences in their flagellar flaA short variable region, suggesting that it may be a potentially useful marker for GBS association.     

Amplification of MGC2177, PLAG1, PSMC6P, and LYN in a malignant mixed tumor of salivary gland detected by cDNA microarray with tyramide signal amplification

Gene amplifications have been observed in many different tumor cells, and many of these changes are related to tumor pathogenesis. Comparative genomic hybridization (CGH) using metaphase chromosomes can detect changes in chromosome copy number with a resolution of 10-20 Mb. Current advances in CGH analysis in a microarray format allow us to refine such changes down to the gene level. We applied microarray technology to detect novel gene amplification in a malignant mixed tumor of salivary gland. Besides detecting previously known gene amplifications (MDM2 and MYC), we identified four other highly amplified genes located at 8q11.2 approximately q13: MGC2177, PLAG1, PSMC6P, and LYN. The amplification was further validated with real-time quantitative polymerase chain reaction.     

Partial purification and characterization of B cell growth factor constitutively secreted by human T-cell hybridoma

Human T cell hybridomas were established by fusion of PHA-activated PBL with the 8-azaguanine resistant human T-leukemic cell line CEM-CM3. High levels of B cell growth factor (BCGF) activity were detected in the supernatants of hybridoma C8-2B2 and its subclones. Hybridoma C8-2B2, in addition to the Leu 3a, also expressed the OKT11 surface marker which was not detectable on the parent CEM-CM3 cells. BCGF from the culture supernatant was purified by combined use of salt fractionation and gel filtration to 36.6 fold with 23.9% recovery of activity. The BCGF produced by hybridoma C8-2B2 has a molecular weight range of 16,000–20,000 in two major electrophoretically different forms with pI values of 6.4 and 7.4.