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Biomedical subjects

S Ratnam

Publications and source records attributed to S Ratnam.

At least 109 records · Page 6Linked to original sources
PubMed1986

Sorbitol-MacConkey medium for detection of Escherichia coli O157:H7 associated with hemorrhagic colitis.

Escherichia coli serotype O157:H7 is a recently recognized human pathogen associated with hemorrhagic colitis. Unlike most E. coli strains, E. coli O157:H7 does not ferment sorbitol. Therefore, the efficacy of MacConkey agar containing sorbitol (SMAC medium) instead of lactose as a differential medium for the detection of E. coli O157:H7 in stool cultures was determined in comparison with MacConkey agar. The relative frequency of non-sorbitol-fermenting (NSF) organisms other than E. coli O157:H7 in feces was low at 10 to 20% (95% confidence limits), and NSF organisms also occurred mostly in small numbers. In a field trial involving over 1,000 diarrheal stools, E. coli O157:H7 was isolated from 18 stools, all of which were from patients with bloody diarrhea. In every instance, the growth of E. coli O157:H7 on SMAC medium was heavy and occurred in almost pure culture as colorless NSF colonies in contrast to fecal flora, which are mostly sorbitol fermenting and hence appear pink on this medium, whereas on MacConkey agar cultures, the growth of E. coli O157:H7 was indistinguishable from fecal flora. SMAC medium permitted ready recognition of E. coli O157:H7 in stool cultures. Detection of E. coli O157:H7 on SMAC medium had a sensitivity of 100%, a specificity of 85%, and an accuracy of 86%. SMAC medium stool culture is a simple, inexpensive, rapid, and reliable means of detecting E. coli O157:H7, and we recommend routine use of SMAC medium especially for culturing bloody stools.

Bacterial Toxins↗
PubMed1985

Postabortion insertion of the Nova T and MLCu250: preliminary results of a comparative study.

This 4-year prospective randomized study is designed to compare the effectiveness and complication rates of the Nova T and MLCu250 inserted immediately postabortion. At the cut-off date (30 November 1983), all patients in the first cohort of 400 women had completed at least 12 months of use. At this stage of the trial, no significant differences had emerged between the two devices in any of the standard termination categories.

Abortion, Induced↗
PubMed1985

Occurrence of Cryptosporidium oocysts in fecal samples submitted for routine microbiological examination.

During a 7-month period, 2,252 fecal samples submitted for routine microbiological examination from 1,621 patients were screened for Cryptosporidium oocysts by the auramine staining method with Kinyoun acid-fast stain as the confirmatory stain. Cryptosporidium oocysts were detected in fecal samples from 19 (1.2%) patients, 18 of whom had gastroenteritis. Diarrheic stools from 14 of these 18 patients were negative for the usual enteropathogens but contained the oocysts in moderate to large numbers. Although Cryptosporidium oocysts were found in patients of all ages, they occurred slightly more frequently in infants and children than in the rest. Cryptosporidium species was one of the common enteropathogens identified in fecal samples submitted for routine parasitological examination during the period of the survey and was second only to Giardia species in terms of frequency. Considering cryptosporidiosis in the differential diagnosis of gastroenteritis in immunocompetent persons and including a search for Cryptosporidium oocysts in routine parasitological examinations of fecal samples appear warranted.

Adolescent↗
PubMed1984

Humoral and cell-mediated immune responses to leptospires in different human cases.

Humoral and cell-mediated immune responses (CMI) to leptospirosis were studied in different groups of human patients. These included clinically suspected cases of leptospirosis, patients with jaundice (HBsAg negative), cases of pyrexia of unknown origin (PUC) (Widal and blood culture negative for typhoid) and healthy blood donors. Humoral immune response was evaluated with nine live strains representing different serogroups of leptospires and CMI with lysates of four strains. The study showed that the CMI appeared earlier than the humoral response which might be useful in the early detection of the disease. As in the humoral immune response, cross reactions to different leptospires were also seen in CMI response.

Antibody Formation↗
PubMed1983

Serological evidence of leptospirosis in a human population following an outbreak of the disease in cattle.

A serological study of leptospirosis in a human population, mainly children of a village near Madras City in Tamilnadu State, India, was undertaken following an outbreak of the disease in cattle as evidenced by clinical symptoms and serology. 27 (68%) of the 40 animal sera tested were positive for leptospiral antibodies. Though cross reactions were present, higher titres and a greater number of positive reactions were seen against autumnalis antigen. 35 (47%) of the 75 human sera gave positive antibody titres and, of these, 22 showed the presence of antibodies to autumnalis antigen.

Adolescent↗
PubMed1983

Isolation of leptospires and demonstration of antibodies in human leptospirosis in Madras, India.

Among 25 clinically suspected cases of leptospirosis, organisms could be isolated from blood and urine of only 10 cases but demonstrated in 15 cases. Antibody titres at a low level were observed to one or more leptospiral antigens in all 25 cases. Nine of the repeated samples from 12 cases showed a four-fold rise in titre. The highest antibody titres were seen against autumnalis. The predominant clinical picture was of fever, myalgia, conjunctival suffusion and jaundice with renal involvement.

Antibodies, Bacterial↗
PubMed1983

Semiquantitative culture of Gardnerella vaginalis in laboratory determination of nonspecific vaginitis.

To evaluate the usefulness of quantitative cultures of Gardnerella vaginalis in the laboratory determination of nonspecific vaginitis, the actual and relative numbers of G. vaginalis in genital cultures of a general patient population were assessed semiquantitatively, and the laboratory results were then correlated with the clinical findings. Of the 1,585 women studied, 417 (26.3%) yielded G. vaginalis in culture. Of these, only 113 (27.1%) were found to have symptoms and signs consistent with nonspecific vaginitis. G. vaginalis was obtained in pure or predominant growth from 87 of 100 consecutive cases with nonspecific vaginitis and 32 of 100 consecutive cases without the symptoms or signs of vaginitis (P less than 0.001). Hence, the positive predictive value of isolation of G. vaginalis in pure and predominant growths was determined to be 73% (87 of 119). Conversely, G. vaginalis was isolated in mixed or light growth significantly more often from asymptomatic women than from symptomatic patients, i.e., 68 versus 13 cases. Therefore, the negative predictive value of isolation of G. vaginalis in mixed and light growths was found to be 84% (68 of 81). Quantitation of the relative amount of G. vaginalis growth had higher predictive values as compared with the assessment of G. vaginalis growth alone. We conclude that quantitative culture of G. vaginalis is essential to obtain maximum reliability of culture results in the laboratory determination of nonspecific vaginitis. Although quantitated cultures of G. vaginalis have high predictive values, laboratory results must be interpreted in conjunction with the clinical findings.

Adolescent↗
PubMed1983

Lack of efficacy of alkali treatment for isolation of Yersinia enterocolitica from feces.

The efficacy of KOH treatment to enhance isolation of Yersinia enterocolitica from stools containing fecal flora which is not adequately suppressed by selective media was tested by direct plating and enrichment techniques. Although a distinct difference in the level of alkali tolerance was observed between Y. enterocolitica and the fecal organisms included in the study, the selective suppression of the fecal flora from stools could not be consistently achieved on this basis. By direct plating, the isolation rates ranged from 4 to 32% for untreated control samples and 11 to 40% for KOH-treated samples, varying with the medium used for culture. The maximum overall recovery rate was 34% by overnight enrichment of fecal samples in Selenite F, tetrathionate, Trypticase soy, and gram-negative broths or by 2-day enrichment in modified Rappaport broth. Alkali treatment of fecal samples did not significantly enhance the isolation rates by these methods. One hundred percent recovery was achieved by prolonged cold enrichment, and alkali treatment made no difference in the recovery rate by this method. Cefsulodinirgasan-novobiocin agar generally yielded higher isolation rates of Y. enterocolitica than did cellobiose-arginine-lysine agar and MacConkey agar, both by direct plating of fecal samples and through subcultures of enrichments, regardless of KOH treatment.

Chemical Phenomena↗
PubMed1982

A nosocomial outbreak of diarrheal disease due to Yersinia enterocolitica serotype 0:5, biotype 1.

An outbreak of diarrheal disease due to Yersinia enterocolitica serotype 0:5 , biotype 1, involved nine hospitalized patients. The possible source of this infection was two patients who were both hospitalized with a history of several weeks of intermittent diarrhea. Person-to-person contact was the probable mode of transmission of the disease. The present report describes the second known nosocomial outbreak of infection due to Y. enterocolitica, Serotype 0:5 of Y. enterocolitica is not commonly encountered, and its involvement in an outbreak of gastroenteritis has not been previously reported. The importance of the enrichment technique in the isolation of Y. enterocolitica is demonstrated.

Adult↗
PubMed1982

Comparative study of selective media for recovery of Yersinia enterocolitica.

To determine the relative efficacy of pectin agar, cellobiose-arginine-lysine (CAL) agar, Y medium, cefsulodin-irgasan-novobiocin (CIN) agar, MacConkey (MAC) agar, and salmonella-shigella (SS) agar for the recovery of Yersinia enterocolitica, 35 strains of this organism representing the serotypes most commonly associated with human disease in Canada and the United States were inoculated on test media in pure cultures and mixed in fecal specimens. Randomly picked stool specimens were also cultured on these media to determine their selectivity. The ability of test media to support the growth of Y. enterocolitica strains varied markedly. Several strains failed to grow on Y medium, and a few failed to grow on SS agar. There were no significant differences in cultural characteristics and the recovery rates of Canadian and American strains. The combined recovery of the pure cultures of Y. enterocolitica on test media as compared with blood agar was MAC, 75%; SS, 48%; pectin, 70%; CAL, 62%; Y, 15%; and CIN, 85%. The selectivity of the test media expressed as the percent difference of the fecal colony counts obtained on blood agar and the selective media was MAC, 7%; SS, 50%; pectin, 4%; CAL, 65%; Y, >/=99.9%; and CIN, 95%. When stool suspensions containing 10(2) colony-forming units of the test strains were plated, CIN medium yielded 100% recovery of all 35 strains from all fecal samples. The combined recovery rate for other media was CAL, 63%; Y, 14%; and SS, 11%. With 10(1) colony-forming units, CIN yielded a 100% recovery of the test strains, whereas CAL, Y, and SS agar showed a 0% recovery. None of the test organisms was recovered on either MAC or pectin agar at either dilution. The inhibitory effect of Y medium for Y. enterocolitica could be overcome to some extent by reducing the sodium oxalate and sodium desoxycholate content of the medium. One such modified Y medium offered optimum selectivity and ensured greater recovery of Y. enterocolitica when compared with the Y medium. We found CIN agar by far the most effective medium for the recovery of Y. enterocolitica. This medium was highly selective and almost completely inhibited the fecal flora, while at the same time supporting luxuriant growth of Y. enterocolitica. On CIN agar, Y. enterocolitica colonies were distinctive in appearance and measured 1.5 to 4 mm in diameter within 20 to 40 h of incubation.

Culture Media↗
PubMed1981

Elevated sialyltransferase activity in the intestinal lymph of colchicine-treated rats.

There is a marked increase in sialyltransferase activity (EC 2.4.99.1) in serum and a profound change in the endogenous acceptor property of sialyltransferase in the intestine of colchicine treated rats (Fraser, Ratnam, Collins and Mookerjea, (1980) J. Biol. Chem. 255, 6617-6625). To ascertain the contribution of intestine as a source of this elevated serum enzyme, sialyltransferase and other enzymes activities were measured in intestinal lymph before and after colchicine treatment. There was a 4-fold increase of the enzyme activity in lymph 3 h after treatment. The lymph flow rate, protein concentration and composition as measured by polyacrylamide gel electrophoresis were not affected. The kinetic properties of lymph sialyltransferase (protein and time dependence, pH optima and Km values for the substrate CMP-sialic acid) were essentially unchanged after treatment and were similar to the serum sialyltransferase. Alkaline phosphatase and lactic dehydrogenase activities remained unchanged. Although intestinal lymph sialyltransferase was increased by colchicine, enterectomy did not prevent the rise of serum sialyltransferase suggesting that the intestine is not a major source of the serum enzyme.

Animals↗
PubMed1980

Effect of phosphatidylinositol and phosphatidylserine on membrane-bound galactosyltransferase.

Membrane-bound galactosyltransferase is solubilized and activated by exogenous lysolecithin or Triton X-100. A study on the effect of different phospholipids on the lysolecithin-solubilized enzyme showed that two charged phospholipids (i.e., phosphatidylinositol and phosphatidylserine) inhibited the membrane-bound enzyme in the presence of a wide range of lysolecithin concentration (up to 6 mumol/mg protein). In contrast, these phospholipids produced a biphasic effect on the enzyme solubilized with Triton X-100. In lower concentration of Triton (up to 2 mumol/mg protein), the charged phospholipids somewhat reduced the enzyme activity but a reversal of this effect was observed when Triton concentration was gradually raised (from 2 to 8 mumol/mg protein). This biphasic effect of the phospholipids was also demonstrated on purified membrane-bound galactosyltransferase in presence of low and high concentration of Triton. Electron microscopic evidence suggested that an increased concentration of phosphatidylinositol prevented membrane solubilization by lysolecithin or retained the membrane vesicular organization concurrent with a restraining effect on the enzyme. The results lend support to the hypothesis that the phospholipid microenvironment of the membrane may exert a control on the membrane-bound glycosyltransferases.

Animals↗
PubMed1978

Ultrastructure of Rhizobium japonicum in relation to its attachment to root hairs.

In Rhizobium japonicum strain Nitragin 61A76, morphologically distinct types of bacteria were found to occur in yeast extract-mannitol broth cultures, at both mid-log and stationary phases. Of these only the capsular form, characterized by a smooth cell envelope, storage granules (glycogen and poly-beta-hydroxybutyric acid), and an amorphous extracellular capsule, bound soybean lectin. The binding site was localized in the capsular material. Less than 1% of the bacterial population differentiated into these capsular forms, which were also able to attach to the soybean root hair surface.

Cell Membrane↗