Hybrid & El Tor variant biotypes of Vibrio cholerae O1 in Thailand.

BACKGROUND & OBJECTIVES: El Tor Vibrio cholerae O1 carrying ctxB C trait, so-called El Tor variant that causes more severe symptoms than the prototype El Tor strain, first detected in Bangladesh was later shown to have emerged in India in 1992. Subsequently, similar V. cholerae strains were isolated in other countries in Asia and Africa. Thus, it was of interest to investigate the characteristics of V. cholerae O1 strains isolated chronologically (from 1986 to 2009) in Thailand. METHODS: A total of 330 V. cholerae O1 Thailand strains from hospitalized patients with cholera isolated during 1986 to 2009 were subjected to conventional biotyping i.e., susceptibility to polymyxin B, chicken erythrocyte agglutination (CCA) and Voges-Proskauer (VP) test. The presence of ctxA, ctxB, zot, ace, toxR, tcpA C , tcpA E, hlyA C and hlyA E were examined by PCR. Mismatch amplification mutation assay (MAMA) - and conventional- PCRs were used for differentiating ctxB and rstR alleles. RESULTS: All 330 strains carried the El Tor virulence gene signature. Among these, 266 strains were typical El Tor (resistant to 50 units of polymyxin B and positive for CCA and VP test) while 64 had mixed classical and El Tor phenotypes (hybrid biotype). Combined MAMA-PCR and the conventional biotyping methods revealed that 36 strains of 1986-1992 were either typical El Tor, hybrid, El Tor variant or unclassified biotype. The hybrid strains were present during 1986-2004. El Tor variant strains were found in 1992, the same year when the typical El Tor strains disappeared. All 294 strains of 1993-2009 carried ctxBC ; 237 were El Tor variant and 57 were hybrid. INTERPRETATION & CONCLUSIONS: In Thailand, hybrid V. cholerae O1 (mixed biotypes), was found since 1986. Circulating strains, however, are predominantly El Tor variant (El Tor biotype with ctxB C).

[Simultaneous detection by multiplex PCR of atypical bacterial pathogens involved in infections of respiratory tract. Is it useful for the microbiological diagnosis of respiratory infections]. / La détection par une PCR multiplex de bactéries responsables de pneumopathies atypiques améliore-t-elle les performances du diagnostic microbiologique des infections du tractus respiratoire?

The aim was to evaluate the "strategical place" of the new commercial test Chlamylege (Argene-Biosoft-France) which allows the simultaneous detection in respiratory samples of Chlamydophila pneumoniae, Mycoplasma pneumoniae and most Legionella species using a PCR multiplex. 41 patients with an atypical pneumonia were included, all standard procedures of diagnosis were done and in addition the chamylege test. A pathogen was identified in 12 patients, an other microorganisms than the 3 targeted by our study was found in 8 patients. 4 positive PCR were obtained, 3 with M. pneumoniae and 1 with Legionella pneumophila 1. That means that for 29 patients no aetiology was found. Among them 23 clearly improved under antibiotic treatment. Though that PCR multiplex is an attractive test, easy to perform, sensitive, specific and convenient, we need further studies to approach the place of this PCR test in the diagnosis of multifaceted atypical pneumonia. We also need to know if the cost associated with the microbiological diagnosis (culture, serology, immunofluorescence, urinary antigen test, PCR...) for atypical pneumonia worth value? An algorithm as to be drawn to determine the value of intensive microbiological investigation. An other point to discuss, may be this kind of rapid and multiplex PCR technique could lead to spare the use of some antibiotics.

Alpha-proteobacteria cultivated from marine sponges display branching rod morphology.

Most isolates recovered from marine environments are Gram-negative proteobacteria, even with the use of various media and media additions to enhance recoverability. Cultivation studies with two genera of deep-water sponges yielded nine isolates that demonstrated bulbous branching rod morphology, which is usually associated with microorganisms staining Gram-positive. Gram reactions indicated that the isolates were Gram-negative, which was confirmed by partial 16S rDNA sequencing. All nine isolates were shown to be alpha-proteobacteria most closely related to other alpha-proteobacteria isolated from various sponges.

Escherichia coli CS31A fimbriae: molecular cloning, expression and homology with the K88 determinant.

CS31A is a plasmid-encoded K88-related fimbrial antigen. A Sau3AI library was constructed from p31A, a 180 kb CS31A encoding plasmid, in the pSUP202 vector. Bacterial recombinant clones expressing CS31A were isolated. A 8.5 kb EcoRI-HinIII DNA fragment from one of them was subcloned in pBR322 and pHSG575 vectors, leading to pAG315 and pEH524 recombinant plasmids respectively. Escherichia coli harboring pAG315 or pEH524 expressed CS31A fimbrial antigens on their cell surface. Analysis of these plasmids in minicells showed that at least seven mature polypeptides were encoded by the EcoRI-HindIII DNA fragment, with apparent molecular masses of 76,000, 54,000, 30,000, 29,000, 28,000, 15,500 and 13,500 daltons respectively. The genetic organization of the CS31A gene cluster was determined and showed to be similar to that of the K88 operon. The nucleotide sequence homology between CS31A and K88 determinants was investigated by Southern blot hybridization at high stringency. This indicated that extensive nucleotide sequence homology exists throughout both gene clusters except for the subunit structural genes.