Effect of iron on the survival of Vibrio cholerae in water.

Effect of iron in the form of ferric oxide (Fe2O3) on the survival of V. cholerae O1 was studied. V. cholerae O1 survived for 8 days in plain water whereas in presence of Fe2O3 it survived up to 15 days. Presence of organic material in the water further promoted the bacterial survival by at least 4 days. There was no difference between the behaviour of El Tor and classical biotype. These results indicate that the presence of iron in water could promote the survival of V. cholerae O1 in water and may play a significant role in the epidemiology of cholera.

Copper resistance & its correlation to multiple drug resistance in Salmonella typhi isolates from south Karnataka.

A study was conducted to ascertain the prevalence of copper resistant Salmonella typhi isolates in south Karnataka. Of the 186 strains studied, 26 (13.97%) were found to be copper resistant. Among the copper resistant strains 19 (73.08%) were found multi drug resistant. All copper resistant strains remained uniformly sensitive to ceftriaxone, ciprofloxacin and norfloxacin. Multiple drug resistance was exclusively associated with E1 phage types.

Evaluation of laboratory techniques for diagnosis of amoebiasis.

Evaluation of 82 cases of amoebiasis including 4 of liver abscess was done. Microscopy of 62 stool samples revealed trophozoites in 19 (30.6%) and cysts in 8 (12.9%). PVA preserved samples were stained by iron-hamatoxylin and trichrome. Twenty-nine samples (46.7%) were positive by culture on Endamoeba, NIH and Charcoal agar. Additional two culture positive cases were negative by direct microscopy. Three (75%) samples of liver abscess pus were culture positive. Of the sera screened for amoebic antibodies by ELISA, 13 (17.3%) were positive. Stool and blood of healthy controls and 25 gastroenteritis cases were similarly analysed. Of healthy controls one had a high ELISA titre.

Antimicrobial susceptibility of Salmonella typhi to quinolones & cephalosporins.

Antimicrobial sensitivity testing was carried out for 85 isolates of S. typhi by disc diffusion and microbroth dilution for estimation of minimum inhibitory concentration (MIC). The drugs used included amoxycillin, chloramphenicol, ciprofloxacin, ofloxacin, gentamicin, netilmicin, cefuroxime, ceftizoxime, cefoperazone and ceftazidime. Ninety three per cent of our isolates were resistant to amoxycillin and chloramphenicol but total susceptibility was seen to quinolones and aminoglycosides. We also found that 3 per cent of our isolates were resistant to cephalosporins and 23 per cent were in the intermediate range with an MIC of 12.5 or 25 micrograms/ml to these drugs. In spite of decreased efficacy, the strains continued to be fully susceptible to ciprofloxacin as could be seen from the extended dilutions in microbroth dilution tests. The study also revealed that there was lack of correlation between the two methods of sensitivity testing for cephalosporins. We feel that the development of resistance of S. typhi to third generation cephalosporins is a finding worth consideration for further studies.

Neonatal bacteremia due to high level aminoglycoside resistant (HLAR) enterococci.

A study was conducted to determine the drug resistance pattern of enterococci isolated from cases of neonatal bacteremia. A total of 41 strains of enterococci were isolated of which 35 (85.4%) were Enterococcus faecalis and 6 (14.6%) were Enterococcus faecium. A total of 3 (8.6%) strains of E. faecalis and 2 (33.3%) E. faecium strains showed high level aminoglycoside resistance (HLAR). None of the enterococci tested were vancomycin resistant. Drug resistance was more common among E. faecium strains. All clinically significant isolates of enterococci should be tested for their antibiotic sensitivity pattern including HLAR, and for treatment, antibiotics are selected based on in vitro antibiotic sensitivity test results.

High level aminoglycoside resistance in enterococci isolated from hospitalized patients.

Drug resistance in enterococci isolated from hospitalized patients is reported. Out of 421 strains tested, 45 (10.7%) showed high level aminoglycoside resistance (HLAR). At the species level, 8.2 per cent of Enterococcus faecalis and 33.3 per cent of E. faecium were HLAR. While all the strains of E. faecalis were sensitive to vancomycin, one strain of E. faecium was vancomycin resistant.

Effect of trace metals on synthesis of exoproteins and exotoxins by Staphylococcus aureus.

Staphylococcus aureus did not grow in chemically defined medium completely free of trace metals. At low concentrations all the trace metals showed stimulating effect on growth and exoprotein production. Increasing concentrations of Ca2+ and Mg2+ were growth stimulatory whereas Co2+, Cu2+, Fe3+, Mn2+, Ni2+ and Zn2+ were inhibitory. The amount of exoprotein and haemolytic exotoxins produced in relation to final viable count increased with increasing concentrations of growth inhibitory trace metals whereas it decreased with increasing concentrations of Ca2+ and Mg2+. Trace metals did not show significant influence on amount of haemolytic exotoxins produced in relation to total exoproteins. The results indicate presence of a common regulatory mechanism for all types of exoproteins produced by S. aureus.

Immunohistochemical localization of riboflavin carrier protein in testicular cells of mammals.

Using specific polyclonal antibodies against chicken riboflavin carrier protein (cRCP), immunocytochemical localization of riboflavin carrier protein was carried out in testicular sections and isolated cells of mammals. A positive reaction was observed in the developing germ cells of rat testis, especially in meiotic and post-meiotic germ cells such as pachytene spermatocytes, round spermatids and spermatozoa. In addition both the somatic cells of the testis, viz. Leydig and Sertoli cells with vital function in germ cell proliferation and differentiation, displayed a moderate to strong staining reaction. This was further confirmed using in utero X-irradiated rat testis devoid of germ cells. Different types of cells isolated from testis when subjected to immunostaining showed similar patterns of reaction as in the intact tissue. Mature spermatozoa from different mammals (rat, bull and monkey) exhibited strong staining reaction in their head regions localized mainly in acrosomal caps. It is suggested that the testicular riboflavin carrier protein has a role in cell to cell communication and may be crucial during development of germ cells especially at the meiotic and post-meiotic stages.

Effect of trace metals on production of exoprotein and beta-lactamase by Staphylococcus aureus.

A minimum concentration of 0.01 mM of Mg2+ was essential for any growth of S. aureus. Of the trace metals, Mg2+ and Ca2+ were highly stimulatory for growth. All trace metals except Ni2+ in small concentrations were stimulatory for growth and exoprotein production. Amounts of exoprotein and beta-lactamase produced relative to the number of viable cells were maximum during the period of suboptimal proliferation of bacteria. Trace metals did not significantly influence the amount of beta-lactamase produced relative to exoprotein.

Effect of magnesium on the physiology of Staphylococcus aureus.

The role of magnesium (Mg2+) in the metabolism of Staphylococcus aureus was studied using a chemically defined medium. At least 0.01 mM Mg2+ was required for any growth of S. aureus. Increasing concentration of Mg2+ up to 1.6mM steadily increased the bacterial growth. Glucose utilisation and acid production were also influenced by Mg2+. Excessive cobalt (Co2+) and zinc (Zn2+) were inhibitory to S. aureus growth and Mg2+ could reverse the inhibitory effect.

A modified chemically defined medium for Staphylococcus aureus.

A chemically defined medium has been described which supported good growth of S. aureus. Optimal production of different exoproteins, viz. coagulase, acid phosphatase, proteinase, lipase, beta-lactamase and alpha-toxin was recorded in the medium.

New microbiological method for the detection of staphylococcal beta-lactamase.

The method has been designed as such to include the induction and testing of beta-lactamase in a single procedure. This method compares favourably with the existing method.