Copper, Zinc-Superoxide Dismutase from Clinically Isolated Escherichia coli: Cloning, Analysis of sodC and Its Possible Role in Pathogenicity.

Superoxide dismutase has been discovered within the periplasm of several Gram-negative pathogens. We studied the Cu,Zn-SOD enzyme in Escherichia coli isolated from clinical samples (stool samples) collected from patients suffering from diarrhea. Antibiogram studies of the isolates were carried out to determine the sensitive and resistant strains. The metal co-factor present in the enzyme was confirmed by running samples in native gels and inhibiting with 2 mM potassium cyanide. A 519 bp sodC gene was amplified from resistant and sensitive strains of Escherichia coli. Cloning and sequencing of the sodC gene indicated variation in the protein and amino acid sequences of sensitive and resistant isolates. The presence of sodC in highly resistant Escherichia coli isolates from diarrheal patients indicates that sodC may play role in enhancing the pathogenicity by protecting cells from exogenous sources of superoxide, such as the oxidative burst of phagocytes. The presence of SodC could be one of the factors for bacterial virulence.

Degradation of h-acid by free and immobilized cells of Alcaligenes latus

Alcaligenes latus, isolated from industrial effluent, was able to grow in mineral salts medium with 50 ppm (0.15 mM) of H-acid as a sole source of carbon. Immobilization of Alcaligenes latus in Ca-alginate and polyurethane foam resulted in cells embedded in the matrices. When free cells and immobilized cells were used for biodegradation studies at concentration ranging from 100 ppm (0.3 mM) to 500 ppm (1.15 mM) degradation rate was enhanced with immobilized cells. Cells immobilized in polyurethane foam showed 100 percent degradation up to 350 ppm (1.05 mM) and 57 percent degradation at 500 ppm (1.5 mM). Degradation rate of Ca-alginate immobilized cells was less as compared to that of polyurethane foam immobilized cells. With Ca-alginate immobilized cells 100 percent degradation was recorded up to 200 ppm (0.6 mM) of H-acid and only 33 percent degradation was recorded at 500 ppm (1.5 mM) of H-acid. Spectral analysis of the products after H-acid utilization showed that the spent medium did not contain any aromatic compounds indicating H-acid degradation by A. latus.

Detection, amplification & sequence homology of sodC in clinical isolates of Salmonella sp.

BACKGROUND & OBJECTIVES: Periplasmic copper and zinc superoxide dismutase (Cu,Zn-SOD or SodC) is an important component of the antioxidant shield which protects bacteria from the phagocytic oxidative burst. Cu,Zn-SODs protect Gram-negative bacteria against oxygen damage which have also been shown to contribute to the pathogenicity of these bacterial species. We report the presence of SodC in drug resistant Salmonella sp. isolated from patients suffering from enteric fever. Further sodC was amplified, cloned into Escherichia coli and the nucleotide sequence and amino acid sequence homology were compared with the standard strain salmonella Typhimurium 14028. METHODS: Salmonella enterica serovar Typhi (S. Typhi) and Salmonella enterica serovar Paratyphi (S. Paratyphi) were isolated and identified from blood samples of the patients. The isolates were screened for the presence of Cu, Zn-SOD by PAGE using KCN as inhibitor of Cu,Zn-SOD. The gene (sodC) was amplified by PCR, cloned and sequenced. The nucleotide and amino acid sequences of sodC were compared using CLUSTAL X. RESULTS: SodC was detected in 35 per cent of the Salmonella isolates. Amplification of the genomic DNA of S. Typhi and S. Paratyphi with sodC specific primers resulted in 519 and 515 bp amplicons respectively. Single mutational difference at position 489 was observed between the sodC of S. Typhi and S. Paratyphi while they differed at 6 positions with the sodC of S. Typhimurium 14028. The SodC amino acid sequences of the two isolates were homologous but 3 amino acid difference was observed with that of standard strain S. Typhimurium 14028. INTERPRETATION & CONCLUSIONS: The presence of SodC in pathogenic bacteria could be a novel candidate as phylogenetic marker.

Degradation of h-acid by free and immobilized cells of Alcaligenes latus.

Alcaligenes latus, isolated from industrial effluent, was able to grow in mineral salts medium with 50 ppm (0.15 mM) of H-acid as a sole source of carbon. Immobilization of Alcaligenes latus in Ca-alginate and polyurethane foam resulted in cells embedded in the matrices. When free cells and immobilized cells were used for biodegradation studies at concentration ranging from 100 ppm (0.3 mM) to 500 ppm (1.15 mM) degradation rate was enhanced with immobilized cells. Cells immobilized in polyurethane foam showed 100% degradation up to 350 ppm (1.05 mM) and 57% degradation at 500 ppm (1.5 mM). Degradation rate of Ca-alginate immobilized cells was less as compared to that of polyurethane foam immobilized cells. With Ca-alginate immobilized cells 100% degradation was recorded up to 200 ppm (0.6 mM) of H-acid and only 33% degradation was recorded at 500 ppm (1.5 mM) of H-acid. Spectral analysis of the products after H-acid utilization showed that the spent medium did not contain any aromatic compounds indicating H-acid degradation by A. latus.

Faecal carriage of CTX-M-15-producing Klebsiella pneumoniae in patients with acute gastroenteritis.

BACKGROUND & OBJECTIVE: Data on extended-spectrum beta-lactamases (ESBLs) produced by Gram-negative bacteria including Klebsiella pneumoniae especially molecular types of ESBL genes from India are limited. The present study was conducted to investigate the carriage and ESBL contents of multidrug-resistant K. pneumoniae recovered from patients with gastroenteritis in a rural village in southern India. METHODS: Nine K. pneumoniae isolates obtained from 45 stool samples from patients with gastroenteritis from one rural and two urban sites, in southern India were included in the study. Antibiotic susceptibility testing, PCR analysis and sequencing were conducted to characterize the ESBL genes. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE). RESULTS: All the isolates were found to be resistant to at least one of the third generation cephalosporins tested. All the study isolates were confirmed to produce ESBLs. PCR and sequencing revealed the responsible gene to be bla(CTX-M-15). bla(TEM) and bla(SHV) were absent. PFGE indicated that fi ve of seven isolates from villagers were genetically closely related, and in turn were related to isolates from patients in two urban areas in this region. INTERPRETATION & CONCLUSION: Our findings showed that genetically-related isolates of K. pneumoniae producing CTX-M-15 were present in multiple areas in southern India. Larger studies need to be done in various geographical regions of the country to better define the molecular epidemiology of ESBL-producing K. pneumoniae and its clinical implications.

Carriage of capsulated strains of Staphylococcus aureus: a population-based study performed in Gulbarga, South India.

Staphylococcus aureus is a common human pathogen in community- and hospital-acquired infections and its capsule is involved in pathogenesis. We report here the identification of type-5 and type-8 capsular antigens of S. aureus and the prevalence of such strains among volunteers in various age and population groups from different locations in India. S. aureus carriage rates varied between 18 and 50% with the highest values among university students and the lowest in schoolchildren, aged 6-20 years. There was no difference in carriage rates for males vs. females (P=0.415) or in the socioeconomic status of carriers vs. non-carriers or age dependence. Among the carriage isolates 21% were type-5, 52% were type-8 and the remaining 27% were non-typable. Among invasive isolates these percentages were 6, 64 and 30 respectively. This implies that type-5 strains may be less invasive than type-8 strains (P=0.0015).

The effect of temperature on the growth and biochemical activities of Escherichia coli in sewage.

Studies on the role of individual species of bacteria in wastewater treatment methods, especially the effect of environmental factors and enzyme activities, are limited. In the present investigation Escherichia coli, isolated from a stabilisation pond, was grown in sterile sewage at various temperatures, ranging from 10 degrees to 50 degrees C, and its growth and associated biochemical activities were studied. A temperature of 30 degrees C was found to be optimum for the growth, BOD removal, NH(3)-N release and the activities of protease and catalase. E. coli which was once considered to be of little value in wastewater treatment, also accounted for a considerable reduction in BOD and NH(3)-N release. At optimum and lower temperatures, the catalase activity was proportional to the viable cell count of the bacterium. Dissolved oxygen exhibited an inverse relationship with bacterial growth and protease activity was more pronounced during the declining phase of bacterial growth.