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Biomedical subjects

C Krishnan

Publications and source records attributed to C Krishnan.

At least 37 records · Page 2Linked to original sources
PubMed1991

Selective medium for isolation of Arcanobacterium haemolyticum and Streptococcus pyogenes.

Sheep blood agar using tryptic soy agar base and containing 3.5% sodium chloride was found to facilitate isolation of Arcanobacterium haemolyticum and improve isolation of Voges-Proskauer negative group A (Streptococcus pyogenes) and group C and G beta-haemolytic streptococci. Commensal oropharyngeal flora such as viridans streptococci, Neisseria species, non-haemolytic streptococci and beta-haemolytic streptococci not belonging to groups A, B, C or G were significantly inhibited.

Agar↗
PubMed1991

Emergence of quinolone resistance among clinical isolates of methicillin-resistant Staphylococcus aureus in Ontario, Canada.

One hundred two isolates of methicillin-resistant Staphylococcus aureus (MRSA) randomly selected from across the Canadian province of Ontario were tested for their susceptibility to ciprofloxacin, norfloxacin, and nalidixic acid by the agar dilution method. Forty-nine percent (50 of 102) had high levels of resistance to these quinolone compounds. For the 50 resistant isolates, ciprofloxacin and norfloxacin had high MICs for 90% of isolates (MIC90s) of 128 micrograms/ml and greater than 128 microgram/ml, respectively; for these isolates, the nalidixic acid MIC90 was greater than 640 micrograms/ml. The majority (98%) of the 50 isolates were also resistant to tobramycin (MIC90, greater than 128 micrograms/ml), while 42% of the isolates were resistant to gentamicin (MIC90, 64 micrograms/ml). Quinolone-resistant MRSA isolates were susceptible to bacteriophages from several groups, indicating independent selection of resistant strains. These results suggest that a reappraisal of the use of fluoroquinolones against MRSA in Canada is necessary.

4-Quinolones↗
PubMed1987

A severe outbreak of Escherichia coli O157:H7--associated hemorrhagic colitis in a nursing home.

In September 1985, an outbreak of Escherichia coli O157:H7 enteritis affected 55 of 169 residents and 18 of 137 staff members at a nursing home. The outbreak was characterized by two phases: a primary wave whose source was probably a contaminated sandwich meal and a secondary wave compatible with person-to-person transmission of infection. Among the elderly residents, the incubation period was 4 to 9 days (mean, 5.7 +/- 1.2). Older age and previous gastrectomy increased the risk of acquiring the infection (P = 0.01 and 0.03, respectively). Antibiotic therapy during exposure was associated with acquiring a secondary infection (P = 0.001). Hemolytic uremic syndrome developed in 12 affected residents (22 percent), 11 of whom died. Overall, 19 (35 percent) of the affected residents died, 17 (31 percent) from causes attributable to their infection. Antibiotic therapy after the onset of symptoms was associated with a higher case fatality rate in the more severe cases, possibly because patients with more severe disease tended to be treated with antibiotics. There were no complications or deaths among the affected members of the staff. Evidence of infection by verotoxin-producing E. coli O157:H7 was detected in 30 of 70 cases on the basis of isolation of this organism or demonstration of free verotoxin in stools. All isolates belonged to the same phage type. The high morbidity and mortality associated with this condition emphasize the need for proper food hygiene, rapid identification of outbreaks of disease, and prompt institution of infection-control techniques among the institutionalized elderly.

Adolescent↗
PubMed1987

Laboratory investigation of outbreak of hemorrhagic colitis caused by Escherichia coli O157:H7.

A severe outbreak of hemorrhagic colitis occurred in London, Ontario, during the month of September 1985. A total of 55 residents and 18 employees of a nursing home developed diarrhea, and 17 residents (age range, 78 to 99 years) died. Specimens from 38 patients, 37 employees and contacts, and 10 autopsies were investigated for all enteric pathogens. Specimens were also planted on MacConkey-sorbitol agar. Fecal extracts were tested on Vero cells for cytotoxin (FVT). Escherichia coli isolates were serotyped and tested for verotoxin and beta-glucuronidase production. Of the 38 symptomatic patients, 26 were positive for FVT, verotoxin-producing E. coli (VTEC), or both. Of the 105 specimens that were examined from these 38 patients, FVT and VTEC were both positive in 30 specimens, FVT only was positive in 13 specimens, and VTEC only was positive in 4 specimens. None of the 27 specimens from 10 autopsies was positive for FVT or VTEC. No other enteric pathogen was found in any of the cases. All asymptomatic individuals were negative for both FVT and VTEC. Of 19 VTEC strains that were isolated, 18 belonged to serotype O157:H7. These 18 strains and 2 more strains that were obtained from sporadic cases that had occurred within the 2 previous months were found to give similar biochemical reactions in a 36-test identification system. All isolates of serotype O157:H7 were beta-glucuronidase negative and susceptible to the antimicrobial agents that are used to treat E. coli infections. Testing for FVT and VTEC was found to be the most sensitive and specific technique for the laboratory diagnosis of this disease. Negative sorbitol, positive raffinose, and negative beta-glucuronidase tests appeared to be consistent markers for aiding in the detection of E. coli O157:H7.

Aged↗
PubMed1987

Sporadic hemorrhagic colitis associated with Escherichia coli, type O157:H7: unusual presentation mimicking ischemic colitis.

Hemorrhagic colitis is a bacterial infection of the colon, associated with a verotoxigenic strain of Escherichia coli, commonly serotype O157:H7. This recently described disease is usually self-limiting. Because fecal cultures are negative for the usual pathogens and the clinicopathologic features closely mimic ischemic colitis, the patient is exposed to the risk of unnecessary surgery. One such situation is described and differentiation between hemorrhagic and ischemic colitis is discussed.

Colitis↗
PubMed1986

Detection of Clostridium difficile toxins by enzyme immunoassay.

An enzyme-linked immunosorbent assay (ELISA) for the rapid diagnosis of antibiotic-associated colitis (AAC) is presented. Commercially available antisera to Clostridium difficile toxins contain antibodies to other antigens found in non-toxigenic C. difficile and other bacteria. Removal of these unwanted antibodies by absorption increased the specificity of ELISA for detection of C. difficile toxins. Specimens tested included 40 faecal extracts positive for cytotoxicity from cases of AAC, 30 diarrhoeic and 30 well-formed stools negative for cytotoxicity and 50 culture filtrates of toxigenic and non-toxigenic C. difficile and other clostridial species. Use of absorbed sera reduced false-positive reactions observed with faecal specimens from 23 to 8%. About 90% of specimens that were positive by the tissue culture cytotoxicity test were positive by ELISA using the absorbed sera. The relative merits of ELISA and other methods for the rapid diagnosis of AAC are discussed.

Bacterial Proteins↗
PubMed1984

Use of an ammonia electrode to study bacterial deamination of amino acids with special reference to D-asparagine breakdown by campylobacters.

A method using an ammonia electrode is being developed for investigating the deamination of amino acids and amides by bacteria. Application of this method to Campylobacter jejuni and C. coli has led to the demonstration of D-asparaginase activity in some strains. This has allowed the subdivision of both species into D-asparaginase-positive and -negative biotypes. Even though the method is in the developmental stage, it was found to be generally reproducible and easy to perform. Areas for further improving the procedure have been identified. The ammonia electrode offers the theoretical possibility of investigating the breakdown of any amino acid by bacteria. It thus opens up a new and practical approach for separating species and strains, particularly in those bacterial groups that are difficult to subdivide by conventional means.

Amino Acids↗
PubMed1978

Prognosis for survival in neonatal meningitis: clinical and pathologic review of 52 cases.

A retrospective review of 52 cases of neonatal meningitis diagnosed and treated at the Hospital for Sick Children, Toronto, was undertaken to determine which clinical or laboratory features were useful in predicting survival. Escherichia coli and group B streptococci were the most common bacteria isolated. Ventriculitis, cerebritis and arteritis were seen at autopsy with either gram-positive or gram-negative infection. Features associated with a good prognosis for survival were (a) peripheral neutrophil count greater than 2,000 x 10(9)/L; (b) normal platelet count or estimate (more than 100 x 10(9)/L), (c) birth weight greater than 2500 g and (d) age at the time of diagnosis more than 1 day. Information on all four features was available for 44 newborn infants. Of those with three or four of the features 87% survived, while of those with one or two features 14% survived. The overall mortality was 48%. The features outlined are useful in determining the severity of disease and therefore may alert the attending physician to the need for more intensive therapeutic and supportive care.

Female↗
PubMed1978

Pathogenesis of mucosal injury in the blind loop syndrome.

Bacterial extracts were prepared from cultures originating in chronic self-filling intestinal blind loops in rats. Their ability to remove active maltase molecules from isolated brush border membranes was studied in vitro. Twelve strains in 51 tested, belonging to one of three species, Bacteroides fragilis, Clostridium perfringens, and Streptococcus fecalis, possessed maltase-releasing activity. The ability to remove maltase correlated well with the ability to hydrolyze p-nitrophenyl-tert-butyloxycarbonyl-l-alaninate (NBA), an ester substrate rapidly hydrolyzed by elastase, but not with substrated favored by tryhsin and chymotrypsin. Maltase-releasing activity from C. perfringens was strongly inhibited by soybean trypsin inhibitor and to a lesser extent by lima bean trypsin inhibitor. Of four chloromethylketone active-site directed inhibitors tested with specificities for elastase, trypsin, and chymotrypsin, inhibition was maximal with elastase-specific inhibitors. In two species, activity was shown to be heat sensitive, and to be inhibited by concentration of the extract. In one species maltase-releasing activity was shown to be due to an enzyme of molecular weight at least 66,000 with the capacity to remove lactase, sucrase, and alkaline phosphatase, as well as maltase. The results indicate that anaerobic or facultatively anaerobic species, previously identified with the pathology of of the blind loop syndrome, contain proteases which are capable of removing components of the intestinal surface membrane. These proteases appear to have elastase-like substrate specificity and may be involved in the etiology of disaccharidase deficiency in bacterial overgrowth syndromes.

Animals↗