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Biomedical subjects

G Lum

Publications and source records attributed to G Lum.

At least 19 recordsLinked to original sources
PubMed2005

A cluster of culture positive gonococcal infections but with false negative cppB gene based PCR.

OBJECTIVES: To describe the prevalence and characteristics of isolates of Neisseria gonorrhoeae grown from urine samples that produced negative results with nucleic acid amplification assays (NAA) targeting the cppB gene. METHODS: An initial cluster of culture positive, but cppB gene based NAA negative, gonococcal infections was recognised. Urine samples and suspensions of gonococci isolated over 9 months in the Northern Territory of Australia were examined using cppB gene based and other non-cppB gene based NAA. The gonococcal isolates were phenotyped by determining the auxotype/serovar (A/S) class and genotyped by pulsed field gel electrophoresis (PFGE). RESULTS: 14 (9.8%) of 143 gonococci isolated were of A/S class Pro(-/)Brpyut, indistinguishable on PFGE and negative in cppB gene based, but not other, NAA. CONCLUSIONS: This cluster represents a temporal and geographic expansion of a gonococcal subtype lacking the cppB gene with consequent loss of sensitivity of NAA dependent on amplification of this target. Gonococci lacking the cppB gene have in the past been more commonly associated with the PAU-/PCU- auxotype, a gonococcal subtype hitherto infrequently encountered in Australia. NAA based on the cppB gene as a target may produce false positive as well as false negative NAA. This suggests that unless there is continuing comparison with culture to show their utility, cppB gene based NAA should be regarded as suboptimal for use either as a diagnostic or supplemental assay for diagnosis of gonorrhoea, and NAA with alternative amplification targets should be substituted.

Bacterial Outer Membrane Proteins↗
PubMed2001

Antibiotic susceptibility of Burkholderia pseudomallei from tropical northern Australia and implications for therapy of melioidosis.

From a prospective melioidosis study commencing in 1989 at Royal Darwin Hospital, 170 initial isolates of Burkholderia pseudomallei were available for susceptibility testing. Of these 163 (96%) were susceptible to meropenem/imipenem, ceftazidime, trimethoprim-sulphamethoxazole (SMX/TMP) and doxycycline. Seven (4%) showed primary resistance; three had low-level resistance to SMX/TMP, one to ceftriaxone and amoxycillin/clavulanate (AMOX/CA) and three to doxycycline. Of 167 patients who survived their initial presentation, seven (4%) had culture positive infections which persisted for greater than 3 months after start of therapy. All ultimately cleared carriage of B. pseudomallei though three required changing to SMX/TMP after development of doxycycline resistance. Nineteen (11%) of the initial survivors clinically relapsed and 17 of these had repeat isolates available for testing. Four of these had acquired resistance: one to doxycycline, one to AMOX/CA and ceftazidime, one to SMX/TMP and one to both SMX/TMP and doxycycline. Molecular typing using randomly amplified polymorphic DNA and pulsed-field gel electrophoresis showed all but one relapse isolate to be the same as the original strain. These data are similar to published data from Thailand. As melioidosis has a high mortality (21% in this series) these results emphasize the need for prolonged eradication therapy and regular clinical and microbiological monitoring so that the emergence of resistance can be detected early and appropriate treatment modifications made.

Amoxicillin-Potassium Clavulanate Combination↗
PubMed2001

Surveillance of antibiotic resistance in invasive isolates of Neisseria meningitidis in Australia 1994-1999.

A total of 1434 strains of Neisseria meningitidis isolated from cases of invasive meningococcal disease (IMD) in Australia between 1994 and 1999 were examined by standard methods for susceptibility to antibiotics used for treatment and prophylaxis. The proportion of isolates fully susceptible to penicillin decreased from 45% in 1994 to 26% in 1999 (P<0.001). All the other isolates were less sensitive to penicillin except for two meningococci with a penicillin MIC of 1 mg/l. The geometric mean penicillin MIC increased from 0.045 to 0.065 mg/l from 1994 to 1999. There was no significant difference in the geometric mean penicillin MICs of serogroup B and serogroup C meningococci. Penicillin susceptibility was significantly associated with a poorer outcome. Isolates from survivors of IMD had a higher geometric mean penicillin MIC (0.06 mg/l) than those from fatal cases (0.048 mg/l) (P< 0.001). This suggests that factors other than the decrease in susceptibility to penicillin observed were more relevant to outcome in IMD. All isolates were fully susceptible to ceftriaxone. Rifampicin resistance was infrequent (eight isolates in 6 years) and sporadic. A single isolate had decreased quinolone susceptibility. Despite the significant shift in susceptibility to penicillin recorded, this group of antibiotics remains a suitable treatment for IMD in Australia.

4-Quinolones↗
PubMed2000

How effective are screening tests for microalbuminuria in random urine specimens?

The effectiveness of four urine screening tests-microalbumin (MAlb), total protein (TProt), total protein/creatinine ratio (TProt/Cr R), and dipstick (DPalb) test for albumin-were evaluated for the detection of MAlb in random urine specimens. The following criteria were used to assess the effectiveness of each urine screening test: 100% specificity (no false positive results); cost effectiveness; rapidity and ease of performing the screening test; and increased laboratory efficiency. A "gold standard" for presence of MAlb in random urine samples was defined as a microalbumin/creatinine ratio (MAlb/Cr R) of > or = 30 mg/g. The least costly urine screening test was the DPalb, which, if assigned a value of 1.0, allowed a cost ranking order for the screening tests-DPalb (1.0) < urine TProt (1.03) < urine TProt/Cr R (2.1) < urine MAlb (7.0). Two hundred urine samples from diabetic inpatients and outpatients were tested. Only two screening tests--MAlb and DPalb--achieved 100% specificity without increasing laboratory costs (small net savings), whereas the other two screening tests--TProt and TProt/Cr R-only achieved 100% specificity with increased laboratory costs. Theoretical prevalence rate analysis showed that urine MAlb screening would be effective at all prevalence rates for overt nephropathy. TProt and DPalb urine screening testing would be most effective in populations with prevalence rates of > or = 15% for overt nephropathy. The TProt/Cr R ratio would only be effective in populations with prevalence rates of > or = 30%. Of the four urine screening tests, only DPalb would significantly streamline the process of measuring urine MAlb. The dipstick test is inexpensive, easy and rapid to perform, does not delay measuring the ratio, since there is no wait for the screening test result, and can be used by referring laboratories to screen urine specimens before they are submitted to a central laboratory, thereby reducing laboratory workload.

Albuminuria↗
PubMed1999

CSF bacterial antigen detection tests offer no advantage over Gram's stain in the diagnosis of bacterial meningitis.

While bacterial antigen detection (BAD) tests have been used on cerebrospinal fluid (CSF) with success in the diagnosis of bacterial infection in developing countries, their value in the developed world has been recently questioned. In Darwin, Northern Territory (NT), there are good diagnostic resources but high rates of infectious disease, so it was unclear which findings were applicable to our own population. This study aimed to determine the utility of the BAD tests in detection of bacterial meningitis from CSF in patients studied at Darwin, using a retrospective review of hospital case records and microbiology laboratory reports, over a 19 month period, and utilising a clinical component in the case definition of bacterial meningitis. The sensitivity of the BAD test in the diagnosis of acute bacterial meningitis was 28.6%, with a specificity of 98.7% and a positive predictive value of 85.7%. The cost per positive test was computed at $240. No cases of bacterial meningitis which were positive on the BAD test were missed on Gram's stain of CSF. We conclude that in our setting BAD tests alone are not sensitive enough to confidently diagnose bacterial meningitis. BAD tests are more costly and offer no advantage in speed of diagnosis or in antibiotic pre-treated patients, compared to routine Gram's stain.

Antigens, Bacterial↗
PubMed1998

Failure of azithromycin therapy in gonorrhea and discorrelation with laboratory test parameters.

BACKGROUND: Azithromycin is efficacious in the treatment of chlamydial genital tract infection but less so in gonorrhea. However, MICs of azithromycin for gonococci from previously reported azithromycin treatment failures were consistently below the 'susceptible' MIC level of 2 mg/L. GOAL OF THIS STUDY: To examine gonococci not eliminated with 1 g azithromycin therapy to establish treatment outcome/MIC correlates in gonorrhea. STUDY DESIGN: The MICs and phenotypes of gonococci isolated from five cases of treatment failure after 1 g azithromycin therapy were determined and compared with the MICs of a systematic sample of routine isolates. RESULTS: Azithromycin MICs of gonococci from five cases of failed 1 g azithromycin treatment were 0.125 or 0.25 mg/L, well within the current 'susceptible' MIC range. None of the isolates were of the mtr phenotype. The MIC90 of a systematic sample of 219 gonococcal isolates was 0.25 mg/L. CONCLUSION: The antibiotic MIC/treatment outcome correlates that are usually found in gonorrhea do not apply for azithromycin. Current MIC criteria do not accurately define susceptibility or resistance of gonococci to azithromycin and by themselves do not predict the likely outcome of therapy. Pharmacokinetic factors may decrease the predictive value of MIC data.

Adult↗
PubMed1997

Culture of the causative organism of donovanosis (Calymmatobacterium granulomatis) in HEp-2 cells.

We report successful culture of Calymmatobacterium granulomatis by standard cell culture methods. Swabs were obtained from lesions in three patients with a clinical diagnosis of donovanosis. For two patients, there was histological confirmation of the disease (i.e., the presence of Donovan bodies in Giemsa-stained smears). Specimens were inoculated onto cycloheximide-treated HEp-2 cell monolayers in RPMI 1640 medium (supplemented with fetal calf serum, NaHCO3, vancomycin hydrochloride, and benzylpenicillin). At 48 h, organisms resembling Donovan bodies were identified in monolayer cultures from all three specimens. The organisms appeared as pleomorphic bacilli with characteristic bipolar staining and "safety pin" appearance. Using a PCR designed to differentiate C. granulomatis from the Klebsiella species (which have a high degree of molecular homology), we were able to demonstrate that the cultured organisms produced a PCR product identical to that obtained from the original swab specimens. It is now possible to test in vitro susceptibility of C. granulomatis to antibiotics and to provide a ready source of DNA and antigenic material to enable the development of serological tests and, possibly in the future, a vaccine.

Cycloheximide↗
PubMed1996

Assessment of a critical limit protocol for point-of-care glucose testing.

A critical limit protocol requiring that all point of care glucose meter readings > 22.2 mmol/L (400 mg/dL) and < 2.2 mmol/L (40 mg/dL) be immediately confirmed by the laboratory was assessed. A total of 193 (2%) of 9,523 glucose meter determinations (63 patients) were > 22.2 or < 2.2 mmol/L. One hundred twenty-two (63%) of critically high and low glucose readings were followed up, and 71 (37%) results were not. Seventy-seven percent (55 of 71) of results without follow up were in patients with multiple glucose meter/central lab comparisons, suggesting that users may have thought it unnecessary to confirm such results. Split sample quality control specimens showed good correlation (r = 0.927) between glucose meter and central lab results, whereas correlation for follow-up glucose results was poorer (r = 0.793), perhaps reflecting time delay in obtaining a lab sample. For follow-up results, only 18% of high/low critical limit glucose meter readings were confirmed by drawing a lab specimen within 10 minutes. Fifty-eight percent were in 17 patients with multiple previous glucose meter readings, suggesting that users may have though it less urgent to confirm a sequence of such results. Eleven follow-up results (9%) showed a > 50% discordance between glucose meter/central lab with three (27%) glucose meter errors, emphasizing the need to confirm critically high/low glucose meter results to avoid potential errors. The critical limit protocol now requires that only the initial critically high/low glucose meter reading be confirmed by the lab and that these patients now be followed with lab values until glucose levels are between 5.6-16.7 mmol/L (100-300 mg/dL) before the glucose meter can again be used.

Adult↗
PubMed1996

Evaluation of a laboratory critical limit (alert value) policy for hypercalcemia.

OBJECTIVE: To evaluate a laboratory critical limit policy for hypercalcemia requiring the laboratory to notify the physician for any serum calcium level higher than 2.99 mmol/L (12.0 mg/dL). DESIGN: The protocol was assessed using the following criteria: recognition, treatment (fluids or drugs) or no treatment of hypercalcemia, and the effect of adopting lower (2.64 mmol/L) or higher (3.22 mmol/L) calcium critical limits. RESULTS: Patients were divided into four groups: group 1, 2.64 to 2.74 mmol/L (n = 131); group 2, 2.77 to 2.87 mmol/L (n = 33); group 3, 2.89 to 2.99 mmol/L (n = 16); and group 4, higher than 2.99 mmol/L (n = 11). Hypercalcemia was recognized in 48%, 55%, 56%, and 100%; treated with fluids in 0%, 0%, 6%, and 9%; treated with drugs in 0%, 0%, 0%, and 73%; and not treated in 100%, 100%, 94%, and 18% of patients in groups 1 through 4, respectively. Lower calcium critical limits of 2.64, 2.77, and 2.89 mmol/L would lead to an increase of 1371%, 442%, and 142% in telephone calls. A higher calcium critical limit of 3.22 mmol/L would have resulted in not notifying the physician of six patients (60%) who were treated for hypercalcemia. CONCLUSIONS: The present hypercalcemia policy is effective because patients with calcium levels below 2.99 mmol/L (< 1%) are rarely treated for hypercalcemia and because lowering the calcium critical limit alert value would not increase physician awareness of hypercalcemic patients. It would, however, result in a significant increase in telephone calls. A higher calcium critical limit (3.22 mmol/L) would potentially result in missing a significant number of hypercalcemic patients in need of therapy.

Adult↗