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Biomedical subjects

R M Chan

Publications and source records attributed to R M Chan.

15 recordsLinked to original sources
PubMed2001

Risk factors for acquisition of levofloxacin-resistant Streptococcus pneumoniae: a case-control study.

A case-control study was conducted to identify the risk factors associated with levofloxacin-resistant Streptococcus pneumoniae (LRSP) colonization or infection. Twenty-seven case patients (patients with LRSP) were compared with 54 controls (patients with levofloxacin-susceptible S. pneumoniae). Risk factors that were significantly associated with LRSP colonization or infection, according to univariate analysis, included an older age (median age, 75 years for case patients versus 72.5 years for controls), residence in a nursing home (odds ratio [OR], 7.2), history of recent (OR, 4.6) and multiple (OR, 4.4) hospitalizations, prior exposure to fluoroquinolones (OR, 10.6) and beta-lactams (OR, 8.6), presence of chronic obstructive pulmonary disease (COPD; OR, 5.9), and nosocomial origin of the bacteria (OR, 5.7). Multivariate analysis showed that presence of COPD (OR, 10.3), nosocomial origin of the bacteria (OR, 16.2), residence in a nursing home (OR, 7.4), and exposure to fluoroquinolones (OR, 10.7) were independently associated with LRSP colonization or infection. Thus, a distinct group of patients with COPD is the reservoir of LRSP.

Aged↗
PubMed2001

Immunorestitution diseases in patients not infected with HIV.

The aim of this study was to assess the clinical spectrum of immunorestitution disease (IRD) in hospitalized patients over a 12-month period. In nine of 18 patients who presented with clinical deterioration during reduction or cessation of immunosuppressants (n = 6) or bone marrow engraftment (n = 3), IRD cases included the following infections: scabies infestation (n = 1); gastric strongyloidiasis (n = 1); hepatosplenic candidiasis (n = 1); methicillin-resistant Staphylococcus aureus abscess formation (n = 2); polyomavirus-related hemorrhagic cystitis (n = 3); and influenza A pneumonitis (n = 1). Immunopathological damage during withdrawal of immunosuppression is an incidental way to uncover an asymptomatic infectious disease. Serial monitoring of hematological and clinical profiles is essential in making a diagnosis of IRD.

Adult↗
PubMed2000

Immunorestitution disease involving the innate and adaptive response.

Immunorestitution disease (IRD) is defined as an acute symptomatic or paradoxical deterioration of a (presumably) preexisting infection that is temporally related to the recovery of the immune system. We report the temporal sequence of events that led to IRD caused by Pneumocystis carinii and Aspergillus terreus in 2 human immunodeficiency virus (HIV)-negative patients soon after the recovery of adaptive and innate immunity, respectively, and we review episodes noted in the English-language literature that fit the definition of IRD (109 episodes in 107 patients). The median time from the recovery of neutrophil counts or termination of steroid therapy to the development of IRD was 8 days in cases of pulmonary aspergillosis (23 episodes) and hepatosplenic candidiasis (8) and 21 days for viral diseases such as hepatitis B (24) and viral pneumonitis (6). For IRD due to mycobacteriosis (27 episodes) and cryptococcosis (4) in HIV-positive patients, the median interval between the initiation of highly active antiretroviral therapy (HAART) and the onset of IRD was 11 days; for viral infections, including those due to cytomegalovirus (14), hepatitis B virus (1), and hepatitis C virus (2), the median interval was 42 days. As an emerging clinical entity, IRD merits further study to optimize treatment of immunosuppressed patients.

Adult↗
PubMed1997

A direct repeat (DR-1) element in the first exon modulates transcription of the preproenkephalin A gene.

The preproenkephalin A gene is regulated by upstream cis-acting elements which respond to various signals, such as cAMP, calcium, and phorbol esters. An additional regulatory element was detected downstream of the transcription start site of the human preproenkephalin A gene in transfection experiments. The element was localized by DNAse I footprinting and methylation interference assays to a direct repeat (DR-1) element in the first (untranslated) exon. Deletion or mutation of this site reduced transcriptional activity of promoter-reporter constructs by over 50%. Antibodies against COUP-TF beta/ARP-1 and RXR transcription factors altered the pattern seen on electrophoretic mobility shift assays using double-stranded oligonucleotide containing the exon 1 protein binding site. This suggests that the factors that bind this site and modulate transcription of the PPE gene include members of the COUP-TF and retinoid X receptor families.

Animals↗
PubMed1995

Chemical modification and site-directed mutagenesis studies of rat 3-hydroxyisobutyrate dehydrogenase.

Rat 3-hydroxyisobutyrate dehydrogenase shares sequence homology with the short-chain alcohol dehydrogenases. Site-directed mutagenesis and chemical modifications were used to examine the roles of cysteine residues and other residues conserved in this family of enzymes. It was found that a highly conserved tyrosine residue, Y162 in 3-hydroxyisobutyrate dehydrogenase, does not function catalytically as it may in other short-chain alcohol dehydrogenases. Of the six cysteine residues present in 3-hydroxyisobutyrate dehydrogenase, only cysteine 215 was found to be critical to catalysis. C215A and C215D mutant enzymes were catalytically inactive but produced CD spectra identical to wild-type enzyme. C215S mutant enzyme displayed a lowered Vmax than wild-type enzyme, but Km values were similar to those of wild-type enzyme. The C215S mutant enzyme was inactivated by treatment with phenylmethanesulfonyl fluoride but was not inactivated by treatment with iodoacetate, whereas the wild-type enzyme was inactivated by treatment with iodoacetate but not inactivated by treatment with phenylmethanesulfonyl fluoride. The present data suggest that 3-hydroxyisobutyrate dehydrogenase differs in mechanism from other short-chain alcohol dehydrogenases studied to date and that cysteine 215 has a critical function in catalysis, possibly as a general base catalyst.

Alcohol Oxidoreductases↗
PubMed1995

Soft tissue tuberculosis: a series of 11 cases.

OBJECTIVE: To describe the clinical characteristics of soft tissue tuberculosis (TB). METHODS: Retrospective review of all cases of soft tissue TB seen by the authors. RESULTS: Eleven cases were seen between 1988 and 1994. All patients but one were foreign born. Six patients had collagen vascular disorders and another had a kidney transplant. Five were taking immunosuppressive therapy and/or prednisone. Three had preceding trauma to the affected area. Five had evidence of previous TB by history or chest radiograph. Symptoms (mean duration 4.4 months) included swelling and pain and often mimicked the underlying disease. Six patients had definite or suspected active TB at other sites. Good initial responses were seen with debridement or drainage and multiple drugs for 6 to 12 months. Two patients have had possible relapses at other sites. Medication intolerance was frequent. CONCLUSION: TB should be considered in patients who present with unexplained soft tissue swelling and pain, particularly if they are immunosuppressed, were foreign born in an endemic area, have an abnormal chest radiograph, or have had trauma to the affected area.

Adult↗
PubMed1992

A multicenter, open comparative study of parenteral cefotaxime and ceftriaxone in the treatment of nosocomial lower respiratory tract infections.

A multicenter Canadian study enrolled 74 persons to compare low-dose cefotaxime at 1 g every 8 hr to ceftriaxone 1 g every 12 hr in patients with nosocomial pneumonia. Of 57 evaluable patients (30 cefotaxime and 27 ceftriaxone) in this preliminary report, 93% responded to therapy in both groups. Ceftriaxone patients tended to have more side effects (14.2%). This study is continuing to accrue patients to achieve 100 evaluable patients. Interim data, however, support the continued use of low-dose cefotaxime as an appropriate alternative for clinically effective and cost-effective management of nosocomially acquired pneumonia.

Adult↗
PubMed1987

Multiple enteric pathogens in a patient with diarrhoea.

A woman who recently arrived in Canada from India developed a febrile, diarrhoeal illness. Stool culture revealed the presence of Salmonella typhi, Campylobacter fetus subspecies jejuni and Shigella flexneri. Concurrent infection with these three pathogens does not appear to have been previously reported. The possibility of multiple pathogens should be considered in travellers who fail to respond to treatment of a single organism.

Adult↗
PubMed1985

Treatment of Pseudomonas and Serratia infections with ceftazidime.

The effectiveness and safety of parenterally administered ceftazidime were assessed in 20 patients with infections caused by Pseudomonas aeruginosa or Serratia marcescens. There were six infections involving the urinary tract, six wound infections, one respiratory tract infection, three septicaemias, one empyema, one mastoiditis and two infections of the epididymis. Sixteen of the isolates were resistant to at least one aminoglycoside antibiotic. Fifteen patients were clinically and bacteriologically cured, two patients improved, but had relapses and three patients showed no response. The lack of clinical response was due to the development of resistance by P. aeruginosa in two patients with osteomyelitis, one of whom also had diabetes mellitus. The third patient who had chronic lymphocytic leukaemia developed post-operative osteomyelitis and septicaemia with serratia. She did not respond to treatment. Side effects consisted of a positive direct Coomb's test without evidence of haemolysis in two patients and a mild maculopapular rash in one patient.

Adult↗
PubMed1984

Reticulum cell sarcoma with unusual presenting features: fever and low cerebrospinal fluid glucose levels.

Reticulum cell sarcoma of the central nervous system usually presents as a focal mass lesion. A patient is described who presented with declining intellectual function, fever, and low glucose levels and pleocytosis in the cerebrospinal fluid, which initially suggested an infectious process. This clinical presentation has not been documented previously. The patient's condition improved following treatment with dexamethasone and radiation.

Brain Neoplasms↗
PubMed1984

Chylopericardium in a drug addict.

Nontraumatic chylopericardium without chylothorax is rare. We describe a patient with chylopericardium associated with intravenous drug addiction. To our knowledge, this association has not been reported previously. The patient underwent total pericardiectomy and had had no recurrence 24 months after surgery.

Adult↗
PubMed1983

Toxic shock syndrome in a patient with systemic lupus erythematosus.

A case is presented of toxic shock syndrome in a patient with systemic lupus erythematosus. Toxic shock syndrome is rarely reported in patients who are immunosuppressed, perhaps because such patients are often treated vigorously with antibiotics at the earliest sign of infection. The association in this case may have been coincidental.

Adult↗
PubMed1983

Drug resistance in malaria: three cases and a review.

Drug resistance has been well documented in two species of malarial parasites. Of greatest concern are the rapid developments in the resistance of Plasmodium falciparum to commonly used therapeutic and chemoprophylactic agents. This species, which is capable of producing life-threatening disease, has shown various levels of resistance in different parts of the world. Also, some strains of the most common species causing relapsing disease, P. vivax, exhibit resistance to primaquine. Three cases of malaria that demonstrate various types of drug resistance are presented in this paper.

Adult↗