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Biomedical subjects

Allen C Cheng

Publications and source records attributed to Allen C Cheng.

At least 19 recordsLinked to original sources
PubMed2007

Outcomes for Mycobacterium ulcerans infection with combined surgery and antibiotic therapy: findings from a south-eastern Australian case series.

OBJECTIVE: To describe the effect of antibiotics on outcomes of treatment for Buruli or Bairnsdale ulcer (BU) in patients on the Bellarine Peninsula in south-eastern Australia. DESIGN: Observational, non-randomised study with data collected prospectively or through medical record review. PATIENTS AND SETTING: All 40 patients with BU managed by staff of Barwon Health's Geelong Hospital (a public, secondary-level hospital) between 1 January 1998 and 31 December 2004. MAIN OUTCOME MEASURES: Epidemiology, clinical presentation, diagnosis, treatment and clinical outcomes. RESULTS: There were 59 treatment episodes; 29 involved surgery alone, 26 surgery plus antibiotics, and four antibiotics alone. Of 55 episodes where surgery was performed, minor surgery was required in 22, and major surgery in 33. Failure rates were 28% for surgery alone, and 19% for surgery plus antibiotics. Adjunctive antibiotic therapy was associated with increased treatment success for lesions with positive histological margins (P < 0.01), and lesions requiring major surgery for treatment of a first episode (P < 0.01). The combination of rifampicin and ciprofloxacin resulted in treatment success in eight of eight episodes, and no patients ceased therapy because of side effects with this regimen. CONCLUSIONS: Adjunctive antibiotic therapy may increase the effectiveness of BU surgical treatment, and this should be further assessed by larger randomised controlled trials. The combination of rifampicin and ciprofloxacin appears the most promising.

Adolescent↗
PubMed2006

Accuracy of enzyme-linked immunosorbent assay using crude and purified antigens for serodiagnosis of melioidosis.

Five enzyme-linked immunosorbent assays developed to detect antibodies to different Burkholderia pseudomallei antigen preparations were evaluated as diagnostic tests for melioidosis in northeast Thailand. The highest diagnostic indices were observed for an affinity-purified antigen (sensitivity, 82%; specificity, 72%) and crude B. pseudomallei antigen (sensitivity, 81%; specificity, 70%), an improvement over the indirect hemagglutination assay (sensitivity, 73%; specificity, 64%).

Antibodies, Bacterial↗
PubMed2006

Q fever outbreak at a cosmetics supply factory.

Q fever is a zoonotic disease that is most commonly associated with outbreaks in slaughterhouses. We describe an outbreak of 4 cases occurring in a factory that processes ovine fetal products for the cosmetics industry. It is important that industries typically not associated with risk of Q fever are made aware of potential health risks that workers might be exposed to so further outbreaks might be prevented.

Adult↗
PubMed2006

Indirect hemagglutination assay in patients with melioidosis in northern Australia.

Melioidosis is caused by the saprophytic organism Burkholderia pseudomallei. The use of the indirect hemagglutination assay (IHA) has found widespread use in areas endemic for this disease. Using this assay, we explored the serologic profile of 275 patients with culture-confirmed melioidosis in the Northern Territory of Australia. Based on a threshold titer of 1:40, the sensitivity of the IHA on admission was 56%. Female patients, those with positive blood cultures, and those with pneumonia independently predicted a negative IHA result. Most patients (68%) with negative admission IHA titers subsequently seroconverted. Most patients (92%) with positive admission IHA titers had persistently positive IHA titers. Relapses were not observed in 36 patients who had a negative IHA at least 1 month after admission, irrespective of initial admission IHA. The IHA has limited utility as a diagnostic test for acute disease, and most patients subsequently have persistently positive titers after recovery from illness.

Adolescent↗
PubMed2005

Extreme weather events and environmental contamination are associated with case-clusters of melioidosis in the Northern Territory of Australia.

BACKGROUND: Melioidosis, the infection due to the environmental organism Burkholderia pseudomallei, is endemic to northern Australia and South East Asia. It is associated with exposure to mud and pooled surface water, but environmental determinants of this disease are poorly understood. We defined case-clusters in northern Australia, determined their contribution to the observed rate of melioidosis, and explored clinical features and associated environmental factors. METHODS: Using geographical information systems data, we examined clustering of melioidosis cases in time and geographical space in the Top End of the Northern Territory of Australia between 1990 and 2002 using a scan statistic. DNA macrorestriction analysis, resolved by pulsed field gel electrophoresis, was performed on isolates from patients. RESULTS: We defined five case-clusters involving 27 patients that occurred within 7-28 days and/or a radius of 100-300 km. Clustered cases were associated with extreme weather events or environmental contamination; no difference in the clinical pattern of disease was noted from other patients not involved in clusters. Isolates from patients linked to environmental contamination were caused by isolates with similar DNA macrorestriction patterns, but isolates from patients linked to severe weather events had more diverse DNA macrorestriction patterns. CONCLUSION: Case-clusters of melioidosis where isolates exhibit diverse DNA macrorestriction patterns in our region are linked to extreme weather events and outbreaks where isolates are predominantly of the same DNA macrorestriction pattern are linked with contamination of an environmental source.

Burkholderia pseudomallei↗
PubMed2005

Prospective evaluation of a rapid immunochromogenic cassette test for the diagnosis of melioidosis in northeast Thailand.

A prospective study was performed to compare a rapid immunochromogenic cassette test (ICT) with the indirect haemagglutination assay (IHA) and clinical rules for the diagnosis of melioidosis in an endemic area. The sensitivity and specificity of the IgG ICT was 86% and 47%, and the IgM ICT was 82% and 47%, respectively. These were similar to the results for IHA (sensitivity 73%, specificity 64%) and clinical rules (73% and 37%). ICT lacks clinical utility as a result of high background rates of positive Burkholderia pseudomallei serology in this population. Low sensitivity and specificity of clinical rules is consistent with the protean manifestations of melioidosis and clinical difficulty in identifying patients with melioidosis.

Adolescent↗
PubMed2005

Two randomized controlled trials of ceftazidime alone versus ceftazidime in combination with trimethoprim-sulfamethoxazole for the treatment of severe melioidosis.

BACKGROUND: Two antibiotic regimens are used commonly in Thailand for the initial treatment of severe melioidosis: ceftazidime in combination with trimethoprim-sulfamethoxazole (TMP-SMX) and ceftazidime monotherapy. It is not known whether TMP-SMX provides an additional benefit. METHODS: Two prospective, randomized trials that compared these regimens for patients presenting with acute severe melioidosis were started independently at tertiary care hospitals in Ubon Ratchathani and Khon Kaen (in northeastern Thailand), and the results were analyzed together as a prospective, individual-patient data meta-analysis. The primary end point was in-hospital mortality rate. RESULTS: The in-hospital mortality rate among all enrolled patients (n=449) was not significantly different between those randomized to ceftazidime alone (25.1%; 56 of 223 subjects) and those randomized to ceftazidime with TMP-SMX (26.6%; 60 of 226 subjects; odds ratio [OR], 1.08; 95% confidence interval [CI], 0.7-1.7; stratified P=.73). Of the 241 patients with culture-confirmed melioidosis, 51 (21.2%) died. Of these 241 patients, 31 (12.9%) died > or =48 h after the time of study entry. Among patients with melioidosis, there was no difference in death rate between the 2 treatment groups for either all deaths (OR, 0.88; 95% CI, 0.48-1.6; stratified P=.70) or for deaths that occurred > or =48 h after hospital admission (OR, 0.88; 95% CI, 0.41-1.9; stratified P=.73). Conditional logistic regression analysis revealed that bacteremia, respiratory failure, and renal failure were independently associated with death and treatment failure. Drug regimens were not associated with death or treatment failure in this model. CONCLUSION: We conclude that the addition of TMP-SMX to ceftazidime therapy during initial treatment of severe melioidosis does not reduce the acute mortality rate.

Adult↗
PubMed2005

Trimethoprim/sulfamethoxazole resistance in clinical isolates of Burkholderia pseudomallei.

OBJECTIVES: Trimethoprim/sulfamethoxazole is commonly used to treat melioidosis. Antimicrobial susceptibility testing using the disc diffusion method is commonly used in melioidosis-endemic areas, but may overestimate resistance to trimethoprim/sulfamethoxazole. PATIENTS AND METHODS: We performed disc diffusion and Etest on isolates from the first positive culture for all patients presenting to Sappasithiprasong Hospital, Ubon Ratchathani, Thailand, with culture-confirmed melioidosis between 1992 and 2003. RESULTS: The estimated resistance rate for 1976 clinical Burkholderia pseudomallei isolates was 13% by Etest and 71% by disc diffusion. All isolates classed as either susceptible (n=358) or as having intermediate resistance (n=218) on disc diffusion were susceptible by Etest. Only 258 of the 1400 (18%) isolates classed as resistant on disc diffusion were resistant by Etest. CONCLUSIONS: Disc diffusion testing of B. pseudomallei may be useful as a limited screening tool in resource poor settings. Isolates assigned as 'susceptible' or 'intermediate' by disc diffusion may be viewed as 'susceptible'; those assigned as 'resistant' require further evaluation by MIC methodology.

Anti-Infective Agents↗
PubMed2005

Clinical profile and strain relatedness of recurrent enterococcal bacteremia.

We defined the molecular epidemiology of recurrent enterococcal bacteremia using pulsed field gel electrophoresis. We identified 27 patients, comprising 60 episodes; strain relatedness was demonstrated in 8 patients with isolates separated by up to 6 y. Carriage of pathogenic enterococci may be prolonged, although re-infection with novel strains is more commonly seen.

Adolescent↗
PubMed2005

Infectious diarrhea in developed and developing countries.

Diarrhea from gastrointestinal infection remains a common problem. In industrialized countries, management is aimed at reducing morbidity and defining groups that may benefit from further investigation. Most infectious diarrhea is self-limiting and only requires supportive management. Viral agents are increasingly recognized as causative agents of epidemic and sporadic diarrhea. In developing countries, diarrhea is a major cause of mortality in children. Oral rehydration therapy, guided by a clinical assessment of the degree of dehydration, is cheap, simple, and effective and remains the mainstay of management of infant diarrhea. Controversies focus on the optimal formulation of oral rehydration solution. A vaccine against rotavirus has the potential to save millions of lives worldwide.

Algorithms↗
PubMed2005

Open-label randomized trial of oral trimethoprim-sulfamethoxazole, doxycycline, and chloramphenicol compared with trimethoprim-sulfamethoxazole and doxycycline for maintenance therapy of melioidosis.

Melioidosis (infection caused by Burkholderia pseudomallei) requires a prolonged course of oral antibiotics following initial intravenous therapy to reduce the risk of relapse after cessation of treatment. The current recommendation is a four-drug regimen (trimethoprim [TMP], sulfamethoxazole [SMX], doxycycline, and chloramphenicol) and a total treatment time of 12 to 20 weeks. Drug side effects are common; the aim of this study was to compare the efficacy and tolerance of the four-drug regimen with a three-drug regimen (TMP-SMX and doxycycline). An open-label, randomized trial was conducted in northeast Thailand. A total of 180 adult Thai patients were enrolled, of which 91 were allocated to the four-drug regimen and 89 to the three-drug regimen. The trial was terminated early due to poor drug tolerance, particularly of the four-drug regimen. The culture-confirmed relapse rates at 1 year were 6.6% and 5.6% for the four- and three-drug regimens, respectively (P = 0.79). The three-drug regimen was better tolerated than the four-drug regimen; 36% of patients receiving four drugs and 19% of patients receiving three drugs required a switch in therapy due to side effects (P = 0.01). The duration of oral therapy was significantly associated with relapse; after adjustment for confounders, patients receiving less than 12 weeks of oral therapy had a 5.7-fold increase of relapse or death. A combination of TMP-SMX and doxycycline is as effective as and better tolerated than the conventional four-drug regimen for the oral treatment phase of melioidosis.

Adolescent↗
PubMed2005

Rapid immunofluorescence microscopy for diagnosis of melioidosis.

An immunofluorescent (IF) method that detects Burkholderia pseudomallei in clinical specimens within 10 min was devised. The results of this rapid method and those of an existing IF method were prospectively compared with the culture results for 776 specimens from patients with suspected melioidosis. The sensitivities of both IF tests were 66%, and the specificities were 99.5 and 99.4%, respectively.

Antigens, Bacterial↗
PubMed2005

Melioidosis: epidemiology, pathophysiology, and management.

Melioidosis, caused by the gram-negative saprophyte Burkholderia pseudomallei, is a disease of public health importance in southeast Asia and northern Australia that is associated with high case-fatality rates in animals and humans. It has the potential for epidemic spread to areas where it is not endemic, and sporadic case reports elsewhere in the world suggest that as-yet-unrecognized foci of infection may exist. Environmental determinants of this infection, apart from a close association with rainfall, are yet to be elucidated. The sequencing of the genome of a strain of B. pseudomallei has recently been completed and will help in the further identification of virulence factors. The presence of specific risk factors for infection, such as diabetes, suggests that functional neutrophil defects are important in the pathogenesis of melioidosis; other studies have defined virulence factors (including a type III secretion system) that allow evasion of killing mechanisms by phagocytes. There is a possible role for cell-mediated immunity, but repeated environmental exposure does not elicit protective humoral or cellular immunity. A vaccine is under development, but economic constraints may make vaccination an unrealistic option for many regions of endemicity. Disease manifestations are protean, and no inexpensive, practical, and accurate rapid diagnostic tests are commercially available; diagnosis relies on culture of the organism. Despite the introduction of ceftazidime- and carbapenem-based intravenous treatments, melioidosis is still associated with a significant mortality attributable to severe sepsis and its complications. A long course of oral eradication therapy is required to prevent relapse. Studies exploring the role of preventative measures, earlier clinical identification, and better management of severe sepsis are required to reduce the burden of this disease.

Animals↗
PubMed2005

Comparison of Ashdown's medium, Burkholderia cepacia medium, and Burkholderia pseudomallei selective agar for clinical isolation of Burkholderia pseudomallei.

Ashdown's medium, Burkholderia pseudomallei selective agar (BPSA), and a commercial Burkholderia cepacia medium were compared for their abilities to grow B. pseudomallei from 155 clinical specimens that proved positive for this organism. The sensitivity of each was equivalent; the selectivity of BPSA was lower than that of Ashdown's or B. cepacia medium.

Agar↗