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Biomedical subjects

C Krishnan

Publications and source records attributed to C Krishnan.

At least 19 recordsLinked to original sources
PubMed2005

Transverse myelitis after lumbar steroid injection in a patient with Behcet's disease.

STUDY DESIGN: Case report. OBJECTIVE: We describe a patient who developed transverse myelitis (TM) following a nerve root injection of steroids and anesthetic at L2 for radicular pain. SETTING: Baltimore, MD, USA. CLINICAL PRESENTATION: A 42-year-old woman developed progressive lower extremity weakness and paresthesias, a T12 sensory level and urinary urgency 8 h following the injection of Marcaine and Celestone into the left L2 nerve root. Magnetic resonance imaging showed T2 signal abnormality with gadolinium enhancement from T12 to the conus medullaris and there was no evidence of traumatic injury to the spinal cord. The patient had undiagnosed Behcet's disease (BD) and had experienced multiple episodes of pathergy: hyper-responsiveness of the skin to local trauma, resulting in inflammation and edema. Intravenous steroids were initiated and the patient experienced a near total clinical resolution and a complete radiologic resolution. CONCLUSION: Since the spinal cord inflammation developed after and immediately adjacent to local spinal trauma, we suggest that the TM in this patient was related to BD and was a pathergy response in the spinal cord.

Adult↗
PubMed2004

Recurrent transverse myelitis associates with anti-Ro (SSA) autoantibodies.

Transverse myelitis (TM) is an idiopathic inflammatory disorder of the spinal cord. The authors observed cases of recurrent TM in patients where anti-Ro (SSA) antibodies were present and therefore performed a case-control study to examine the frequency of anti-Ro autoantibodies in patients with recurrent TM and control subjects. Antibodies to 52-kd Ro were demonstrated in 77% of cases (10/13) compared with only 33% of control subjects (4/12).

Adolescent↗
PubMed2004

Venous hypertensive myelopathy as a potential mimic of transverse myelitis.

STUDY DESIGN: Case report. OBJECTIVE: We describe a patient who developed a myelopathy associated with a noncompressive herniated cervical intervertebral disc at the same level. We provide clinical and radiological evidence that reveals that even though the disc herniation did not compress the spinal cord, it diminished venous blood flow out of the spinal cord, possibly resulting in a venous hypertensive myelopathy (VHM). SETTING: Baltimore, MD, USA. CLINICAL PRESENTATION: A 29-year-old woman developed a cervical radiculopathy, followed by a slowly progressive cervical myelopathy associated with a herniated C5-C6 disc. Magnetic resonance imaging showed a noncompressive disc herniation, a swollen spinal cord with increased T2 signal most prominent at the site of the herniated disc, extending several levels above and below the disc. The patient was diagnosed with acute transverse myelitis (ATM) and was started on IV steroids. However, unlike most cases of transverse myelitis, spinal fluid analysis was noninflammatory. In contrast, several features suggested that the patient instead had VHM. We suggest that the disc herniation resulted in impaired drainage of blood from the spinal cord through compression of the venous plexus near the intervertebral foramen. INTERVENTION: Although the patient did not recover function following high-dose steroid administration, she recovered completely following C5-C6 discectomy and fusion. CONCLUSION: To our knowledge, this is the first report of likely VHM in the absence of a spinal arteriovenous malformation. We suggest that some patients diagnosed with ATM in the setting of extrinsic spinal column abnormalities may actually have a noninflammatory myelopathy associated with impaired spinal venous drainage.

Acute Disease↗
PubMed2000

Morning glory disk anomaly, choroidal coloboma, and congenital constrictive malformations of the internal carotid arteries (moyamoya disease).

PURPOSE: To report a patient with congenital constrictive malformations of the internal carotid arteries and a morning glory disc anomaly (MGDA). METHODS: Descriptive case report. RESULTS: A 14-year-old girl underwent serial ophthalmologic examinations since the age of seven years because of blurred vision and floaters. A right optic disk anomaly was present that was most compatible with an MGDA accompanied by an inferior choroidal coloboma. Because of the association of such disc malformations with moyamoya disease, the patient underwent cerebral MRI and MRA that showed narrowing of both internal carotid arteries, a finding consistent with early-stage moyamoya disease. CONCLUSION: This case illustrates the importance of recognizing the association of MGDA with moyamoya disease, a treatable condition that may have devastating neurological consequences.

Adolescent↗
PubMed1998

Infection due to Yersinia enterocolitica in a series of patients with beta-thalassemia: incidence and predisposing factors.

Over 15 years, 14 patients with yersiniosis in two North American comprehensive thalassemia clinics (0.6 cases per 100 patient-years) presented with fever (100%), diarrhea (86%), right-lower-quadrant abdominal pain (71%), bacteremia (57%), a palpable abdominal mass (36%), and pharyngitis (28%). Clinically apparent infection occurred within 10 days of blood transfusion in 57% of patients. Nine patients (64%) had only a modest elevation in serum level of ferritin (< 2,000 micrograms/L). Patients with focal abdominal findings had a higher body iron burden, as estimated by the serum ferritin level, and significant intraabdominal suppurative complications. Two patients were not receiving iron-chelating therapy with deferoxamine; one patient was receiving the experimental chelator deferiprone (L1). Iron-loaded patients with beta-thalassemia are at greatly increased risk for severe yersiniosis, even when their body iron burden (as indicated by the serum ferritin level) is only moderately elevated and they are not receiving iron-chelating therapy with deferoxamine.

Adolescent↗
PubMed1998

Molecular characterization of multiresistant strains of Salmonella typhi from South Asia isolated in Ontario, Canada.

Two hundred and fourteen isolates of Salmonella typhi submitted to our laboratory between 1992 and 1996 were tested for susceptibility to 20 antimicrobial agents. Forty-eight of the 214 isolates (22.4%), recovered from individuals who had travelled in South Asia, were multiresistant. Forty-four of the 48 isolates were resistant to ampicillin, chloramphenicol, tetracycline, streptomycin, sulfamethoxazole, trimethoprim, cotrimoxazole, ticarcillin, and piperacillin; the other four isolates were resistant to four to six agents. Forty-two of the multiresistant isolates belonged to Vi phage type E1, two isolates from the Punjab State belonged to phage type A, another from the Punjab State belonged to phage type E3, one isolate from Pakistan belonged to type M1, and one isolate from India belonged to type J1. Plasmids from 45 of 48 isolates showed a temperature-sensitive mechanism of transfer to Escherichia coli K-12 strains, characteristic of H1 incompatibility group plasmids. The majority of plasmids had an estimated molecular weight of 120 MDa and encoded both citrate utilization and mercury resistance. Plasmids from three isolates had an estimated molecular weight of 112-115 MDa; one of these isolates encoded citrate utilization but not mercury resistance. Analysis of isolates by pulsed-field gel electrophoresis after digestion with XbaI and SpeI indicated that the majority of multiresistant isolates shared a common restriction profile, while four isolates had unique patterns.

Adolescent↗
PubMed1997

High-level tetracycline-resistant Neisseria gonorrhoeae in Ontario, Canada--investigation of a cluster of isolates, showing chromosomally mediated resistance to penicillin combined with plasmid-mediated resistance to tetracycline.

Between 1991 and 1994, plasmid-mediated, tetracycline-resistant Neisseria gonorrhoeae (TRNG) increased from 61.8% to 85.96% of all resistant isolates in Ontario, Canada. Ninety-nine isolates with tetracycline MICs >32 mg/L were characterized by auxotype/serovar (A/S) class, plasmid profile, hybridization with eight tetracycline-resistant probes, and pulsed-field gel electrophoresis (PFGE) of genomic DNA after digestion with NheI and SpeI restriction endonucleases. A cluster of 82 isolates with penicillin MICs of 2-4 mg/L and tetracycline MICs of 128 mg/L (chromosomally mediated resistance) belonged to A/S class NR/IB-1 and had identical or closely related PFGE profiles. Seventeen isolates, TRNG (10) and penicillinase-producing TRNG (7), with tetracycline MICs of 64-256 mg/L, belonged to eight A/S classes and displayed 12 different PFGE profiles. The 99 isolates hybridized only with the TetM probe. Phenotypic and molecular characterization indicated a diverse population throughout the Province of Ontario.

Chromosomes, Bacterial↗
PubMed1997

Analysis of Neisseria gonorrhoeae in Ontario, Canada, with decreased susceptibility to quinolones by pulsed-field gel electrophoresis, auxotyping, serotyping and plasmid content.

The incidence of Neisseria gonorrhoeae with reduced susceptibility to quinolones increased from 0.18% (63 of 3285) in 1992 to 0.56% (15 of 2663) in 1993 and 0.62% (46 of 2846) in 1994. In all, 65 of the 67 isolates of Neisseria gonorrhoeae with decreased susceptibility to quinolones were characterised by pulsed-field gel electrophoresis (PFGE), auxotyping, serotyping and plasmid content. The strains were distributed among 14 auxotype/serovar (A/S) classes. Thirty isolates (46.2%) which were penicillin-susceptible with ciprofloxacin MIC90 of 0.12 mg/L and norfloxacin MIC90 of 1.0 mg/L belonged to a single A/S class, OUHL/IA-2. All but two of the 30 isolates had identical PFGE restriction profiles with NheI restriction endonuclease. Fifteen isolates (23.1%) with MICs in the intermediate (or resistant) categories for penicillin and with ciprofloxacin and norfloxacin MIC90 of 0.25 and 4.0 mg/L and (0.5 and 4.0 mg/L) respectively, belonged to A/S class P/IB-1. The 15 isolates showed nine different patterns with NheI and eight patterns with SpeI restriction endonucleases. Two of three beta-lactamase-producing (PPNG) isolates belonged to A/S class P/IB-5 and had a dissimilar PFGE restriction profile with NheI endonuclease; the other isolate belonged to A/S class P/IB-8. The remaining 17 isolates were distributed among 11 A/S classes. Three isolates within the common A/S class NR/IB-1 were subdivided into two types by PFGE as were three isolates belonging to A/S class NR/IB-2. Overall the 65 isolates of N. gonorrhoeae were distributed into 30 NheI and 26 SpeI macrorestriction profiles. All but one isolate harboured the 2.6-MDa cryptic plasmid and 18 isolates carried the 24.5-MDa transferable plasmid. The three PPNG isolates carried the 4.5-MDa Asian beta-lactamase-producing plasmid and a 25.2-MDa conjugative plasmid was found in the two TRNG isolates.

4-Quinolones↗
PubMed1996

Thermosensitive transfer of antimicrobial resistances and citrate utilization and cotransfer of hydrogen sulfide production from an Escherichia coli isolate.

A hydrogen-sulfide producing, citrate-positive strain of Escherichia coli isolated from urinary tract infection was found to be resistant to chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm), trimethoprim (Tmp), sulfamethoxazole (Smx), and cotrimoxazole (Tmp/Smx). The strain contained 7 plasmids of molecular sizes 120, 35, 5.0, 3.2, 3.0, 2.6, and 2.4 megadaltons (Md), as detected by agarose gel electrophoresis of plasmid DNA. Thermosensitive transfer of Cm, Tc, and citrate utilization occurred conjugally to E. coli K-12 recipient strains at a frequency of approximately 10(-6) per donor cell after an 18 hour incubation. The transconjugants were also resistant to Sm and Smx and produced hydrogen-sulfide. Two plasmids of about 120 Md, pNH222, and 35 Md, pNH223, were detected in these transconjugants. Transformation or 1-hour conjugal transfer experiments at 26 degrees C with selection for Cm or Tc yielded only the 120 Md species. Plasmid pNH222 showed one way incompatibility with F plasmids, a characteristic shown previously to be typical of Inc HI1 plasmids. Transformation experiments with selection for Sm yielded transformants with one plasmid species, (pNH223), 35 Md in size, which carried the gene(s) for H2S production but not for raffinose fermentation. The fact that characteristics such as citrate utilization and hydrogen sulfide production, used in the identification of enteric bacteria, can be transmitted to E. coli by plasmids is of important taxonomic significance.

Anti-Bacterial Agents↗
PubMed1996

Detection of pathogenic Yersinia enterocolitica using the multiplex polymerase chain reaction.

A multiplex polymerase chain reaction (PCR) was developed to detect the presence of the ail, yst, and virF genes of Yersinia enterocolitica simultaneously, quickly and accurately. The amplified fragment sizes were 356 base-pairs (bp) for the ail gene, 134 bp for the yst gene, and 231 bp for the virF gene. The specificity of the amplified products was confirmed by hybridization with digoxigenin-labelled oligonucleotide probes. Amplification was successful whether the template was derived from a single colony of bacteria, aliquots of boiled bacterial suspensions, from DNA extracted from pure or mixed cultures or from stool specimens. Amplification of the virF gene was also achieved from strains of Y. pseudotuberculosis carrying the 70 kb plasmid but not with preparations from other related Yersinia species or from other members of the family Enterobacteriaceae. The detection limit we established was 5-10 colony forming units per millilitre (cfu/ml) and 1.0 pg of DNA.

Animals↗
PubMed1994

Antimicrobial susceptibility of pathogenic Yersinia enterocolitica isolated in Canada from 1972 to 1990.

Yersinia enterocolitica has emerged as an enteropathogen associated with several types of human infections that often require antimicrobial therapy, but little is known about the antimicrobial susceptibilities of pathogenic strains isolated from humans in Canada. To determine the present patterns of antimicrobial susceptibility, to identify changes in these patterns that occurred during the past two decades, and to investigate the relationships between O serotypes and patterns of susceptibility, we tested a total of 1,105 pathogenic Y. enterocolitica strains isolated during 1972 to 1976, 1980, 1985, and 1990 for their susceptibilities to 22 antimicrobial agents. Susceptibility testing was performed by using a single breakpoint concentration in agar procedure. The results showed that all strains were susceptible to ciprofloxacin and piperacillin, and 98% or more of the strains from each period were susceptible to trimethoprim, sulfamethoxazole, cotrimoxazole, tetracycline, chloramphenicol, cefamandole, cefotaxime, aztreonam, and four aminoglycosides. In contrast, all strains were nonsusceptible to erythromycin, furazolidone, and clindamycin and 90% or more of the strains from each period were nonsusceptible to ampicillin, carbenicillin, ticarcillin, and cephalothin. Strains belonging to serotypes O:3, O:5,27, and O:8 had different patterns of susceptibility to ampicillin, carbenicillin, ticarcillin, and amoxicillin-clavulanic acid. No major difference in susceptibility was observed between any of the groups of human or animal strains included in the study, but nonsusceptibility to tetracycline increased from 0.4% in 1985 to 2% in 1990 in human strains isolated in those years. Our results indicate that between 1972 and 1990 there was no marked decrease in susceptibility to agents commonly used for therapy among pathogenic Y. enterocolitica strains isolated in Canada.

Animals↗
PubMed1993

Isolation of a nicotinamide-requiring clone of Escherichia coli O18:K1:H7 from women with acute cystitis: resemblance to strains found in neonatal meningitis.

During a study of the nutritional requirements of clinical isolates of Escherichia coli, we found that 21 (7.0%) of 301 strains required nicotinamide to grow in minimal medium. The nicotinamide-requiring strains were present in 16 (15.8%) of 101 cultures of urine from young women with acute cystitis, in 5 (5.0%) of 100 stool specimens from healthy adults, and in none of 100 blood samples from adult patients with bacteremia. Most of the strains belonged to serogroup O18:K1:H7, were hemolytic, possessed type 1 fimbriae, and exhibited similar patterns of antibiotic susceptibility. Two of the urinary isolates expressed S fimbriae, and all 16 urinary isolates contained the sfaS homologue gene on their chromosomes. One of the stool isolates contained the sfaS gene. The urinary isolates closely resembled a large clone of E. coli that is reportedly associated with neonatal meningitis and sepsis. It may be possible to detect this and related clones by their requirement for nicotinamide and to screen strains for S fimbriae by relatively inexpensive hemagglutination methods, including the use of avian P1 antigens to detect mannose-resistant, non-P-fimbriated E. coli; the agglutination of bovine erythrocytes; and the use of bovine mucin to detect sialyl galactosides in S fimbriae.

Acute Disease↗
PubMed1993

Do temperature-sensitive auxotrophs of Escherichia coli have special virulence?

To determine whether temperature (42 degrees C)-sensitive auxotrophs of Escherichia coli have special virulence properties (W. D. Welch, D. Kitts, H. S. Moyed, and L. D. Thrupp, J. Clin. Microbiol. 13:606-608, 1981), we examined 301 strains isolated from patients with bacteremia or acute cystitis and from the stools of healthy subjects. Of these strains, 49.5% grew at 42 degrees C without supplements, 39.2% required a nutritional supplement, and 11.3% failed to grow even with selected nutrients. Nicotinamide restored growth for 35.2% of strains at either 37 or 42 degrees C. Some of strains required methionine, glutamic, aspartic, and amino acid mixtures or NaCl for growth at 42 degrees C. Temperature-sensitive strains were significantly more abundant in isolates from blood and urine than in stool, but temperature-sensitive auxotrophs were isolated at about the same frequency from each site. There were no discernible clonal patterns, by serotype, among of the nicotinamide-requiring temperature-sensitive auxotrophs. Resistance to trimethoprim-sulfamethoxazole was associated with ability to grow at 42 degrees C. This was not observed with any other antimicrobial drug. Temperature-sensitive strains are a heterogenous group. The relationship of temperature-sensitive auxotrophy to virulence is uncertain.

Bacteremia↗