SXT constin among Vibrio cholerae isolates from a tertiary care hospital.

BACKGROUND & OBJECTIVES: The SXT element, also known as 'constin' (conjugable, self transmissible, integrating element) is an integrating conjugative element (ICE) in Vibrio cholerae discovered in the chromosome of epidemic V. cholerae O139 strain MO10 (SXT MO10 ) which arose in late 1992 in Chennai, India. SXT related ICEs have become widespread and currently, most if not all Asian V. cholerae clinical isolates contain SXT related ICEs. The present study attempts to determine the presence of SXT Int gene in V. cholerae recovered between 2005 to 2007 in a tertiary care hospital, demonstrate its conjugal nature and also detect co-presence and co-transfer of plasmids in representative isolates. METHODS: This prospective study was done on 116 V. cholerae isolates [114- O1 (107 ogawa and 7 inaba) and 2 - Non O1 Non O139 V. cholerae] from watery stools between 2005 to 2007 recovered from equal number of patients. PCR was carried out using SXT Int specific primers that produced a 592 bp internal fragment of SXT element, and rifampicin resistant strain of E.coli K-12 was used as recipient in conjugation experiments to study transfer of SXT, as also co-transfer of resistance to tetracycline, erythromycin, and nalidixic acid. Antibiotic susceptibility was performed against various antibiotics. RESULTS: Of the 116 isolates, 110 (94.8%) were positive for SXT element by PCR. It was demonstrated in 94.7 per cent of the O1, and 100 per cent of non O1 non O139 V. cholerae. All 2005 isolates, 25 per cent of 2006 isolates and 96.6 per cent of 2007 isolates were positive for SXT. Thirty two drug resistance patterns were observed and the 2007 isolates showed resistance to as many as eight antibiotics. The resistance of SXT positive isolates was higher than those of SXT negative and the typical drug resistance pattern corresponding to SXT ET and SXT MO10 was shown by only one V. cholerae O1 isolate. Successful conjugal transfer of SXT was seen in 31 (88.6%) of the 35 isolates studied without any co-transfer while, presence of plasmids was observed in two of the 31 donor V. cholerae studied. INTERPRETATION & CONCLUSIONS: The demonstration of SXT element and its successful horizontal transfer in V. cholerae isolates studied emphasizes the need for its detection to monitor antibiotic resistance and dissemination in V. cholerae.

Inhibition of Mycobacterium tuberculosis secretory serine protease blocks bacterial multiplication both in axenic culture and in human macrophages.

To study the possible importance of mycobacterial ES-31 serine protease for bacterial cell growth, the effect of serine and metalloprotease inhibitors, anti-tubercular drugs such as isoniazid and anti-ES-31 antibody, was evaluated on mycobacterial ES-31 serine protease in vitro and on bacilli in axenic and macrophage cultures. Serine protease inhibitors such as pefabloc, 3,4 dichloroisocoumarin, phenyl methyl sulfonyl fluoride (PMSF) and metalloprotease inhibitors such as ethylene diamine tetracetic acid (EDTA) and 1,10 phenanthroline inhibited 65-92% serine protease activity in vitro. Isoniazid showed 95% inhibition on mycobacterial ES-31 serine protease. These inhibitors also showed decreased bacterial growth in axenic culture and inhibition was further confirmed by a decreased amount of ES-31 serine protease in culture filtrate. In human macrophage culture, highly inhibitory pefabloc, 1,10 phenanthroline and isoniazid inhibited infectivity of virulent as well as avirulent M. tuberculosis bacilli to macrophages. It was observed that addition of mycobacterial ES-31 serine protease to macrophage culture enhanced the entry of bacilli and their multiplication in human macrophages. However, the addition of anti-ES-31 serine protease antibody strongly inhibited the mycobacterial growth as observed by decreased CFU count, showing the importance of mycobacterial ES-31 serine protease for entry of bacilli and their multiplication.

Acrophialophora fusispora: an emerging agent of human mycoses. A report of 3 new clinical cases.

Acrophialophora fusispora is a soil-borne fungus, which is emerging as a human pathogen. Only four cases of human infection had been described previously. We describe three more cases, two from Europe and one from India. Since this fungus has been misidentified in several other cases, it is probably more frequent than first thought.