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Comparison of imipenem and ceftazidime as therapy for severe melioidosis.

An open, prospective, randomized, comparative treatment trial was conducted to compare the therapeutic efficacy of high-dose intravenous imipenem and ceftazidime for acute severe melioidosis. Adult Thai patients with suspected acute, severe melioidosis were randomized to receive either imipenem, at a dosage of 50 mg/(kg x d), or ceftazidime, at a dosage of 120 mg/(kg x d), for a minimum of 10 days. The main outcome measures were death or treatment failure. Of the 296 patients enrolled, 214 had culture-confirmed melioidosis, and 132 (61.7%) of them had positive blood cultures. Mortality among patients with melioidosis was 36.9% overall. There were no differences in survival overall (P = .96) or after 48 hours (P = .3). Treatment failure after 48 hours was more common among patients treated with ceftazidime (P = .011). Both treatments were well tolerated. Imipenem is a safe and effective treatment for acute severe melioidosis and may be considered an alternative to ceftazidime.

Adolescent↗

Antilipopolysaccharide II: an antibody protective against fatal melioidosis.

This was a study of IgG antibody responses to two S-type lipopolysaccharides (LPS I and LPS II) and flagellin of Burkholderia pseudomallei in patients with melioidosis. The specificity of these antibodies was 91.7%, 90.3%, and 93.8%, respectively, when compared to responses in a population where the organism is not endemic. Only the level of antibody to LPS II (anti-LPS II) was significantly higher in patients who survived than in those who died, as well as in patients with nonsepticemic vs. septicemic melioidosis. Results of logistic regression analysis, controlled for confounding factors such as duration of illness before treatment and bacteremic status, confirmed that a high level of anti-LPS II was a significant factor protective against fatal melioidosis. Thus, LPS II of B. pseudomallei would be a potentially useful component of a vaccine developed against fatal melioidosis. Further studies are in progress to determine the level of this antibody among those with asymptomatic infection in areas where melioidosis is endemic.

Adult↗

Neurological melioidosis: seven cases from the Northern Territory of Australia.

Pseudomonas pseudomallei, which causes melioidosis, is most commonly associated with pulmonary infection. We describe seven patients who developed a neurological syndrome as the predominant manifestation of melioidosis: this syndrome was characterized by peripheral motor weakness (mimicking Guillain-Barré syndrome), brain-stem encephalitis, aseptic meningitis, and respiratory failure. Neurological melioidosis occurred in the absence of demonstrable foci of infection in the central nervous system (CNS) in five of six patients whose cerebrospinal fluid was available for culture. Computed tomography and magnetic resonance imaging of the brain and spinal cord of these patients were not suggestive of pyogenic infection, although the latter procedure detected brain-stem encephalitis. Autopsy findings in one case confirmed brain-stem encephalitis without evidence of direct bacterial infection. The clinical presentation of neurological melioidosis includes features of an exotoxin-induced neurological syndrome, with profound neurological disease occurring in the absence of apparent direct infection of the CNS. This syndrome appears to be a newly recognized clinical presentation of melioidosis.

Adult↗

Enzyme-linked immunosorbent assay for immunoglobulin M specific antibody for the diagnosis of melioidosis.

Indirect hemagglutination (IHA) is commonly used for serodiagnosis of melioidosis. However, in endemic areas, high background titers in normal populations and occasional low titers in patients with septicemic melioidosis prompted a search for a more sensitive and more specific method of serodiagnosis. An indirect fluorescent-antibody test for immunoglobulin M (IgM) specific antibody to Pseudomonas pseudomallei was more sensitive and more specific, but fluorescence microscopes are rarely available in the endemic areas. An enzyme-linked immunosorbent assay (ELISA) for IgM antibody is an attractive alternative. An indirect ELISA for IgM antibody (IgM ELISA) and an IgM antibody capture ELISA for melioidosis were developed. Both tests, together with IHA, were evaluated for 153 serum specimens from blood donors and 16 serum specimens from 16 melioidosis patients. It was found that IHA, the IgM ELISA, and the IgM antibody capture ELISA had sensitivities of 88, 88, and 75%, respectively, with specificities of 97.4, 92.2, and 91.5%, respectively. When IHA was combined with IgM ELISA, a sensitivity of 100% and a specificity of 95.4% were obtained. The IgM ELISA and IHA should be used in combination for serodiagnosis of melioidosis.

Antibodies, Bacterial↗

Further evaluation of a rapid diagnostic test for melioidosis in an area of endemicity.

Immunochromatographic test (ICT) kits for the rapid detection of immunoglobulin G (IgG) and IgM antibodies to Burkholderia pseudomallei were compared to the indirect hemagglutination (IHA) assay. In 138 culture-confirmed melioidosis cases, sensitivities were 80, 77, and 88% for IHA, ICT IgG, and ICT IgM, respectively. In a prospective study of 160 consecutive sera samples sent for melioidosis serology, respective specificities were 91, 90, and 69, positive predictive values were 41, 32, and 18, and negative predictive values were 99, 98, and 100%. ICT IgM kits are unreliable for diagnosis of melioidosis, but ICT IgG kits may be useful for diagnosing travelers presenting with possible melioidosis who return from regions where melioidosis is endemic.

Antibodies, Bacterial↗

Melioidosis: an important cause of pneumonia in residents of and travellers returned from endemic regions.

Melioidosis is endemic in South East Asia, Asia and northern Australia. Infection usually follows percutaneous inoculation or inhalation of the causative bacterium, Burkholderia pseudomallei, which is present in soil and surface water in the endemic region. While 20-36% of melioidosis cases have no evident predisposing risk factor, the vast majority of fatal cases have an identified risk factor, the most important of which are diabetes, alcoholism and chronic renal disease. Half of all cases present with pneumonia, but there is great clinical diversity, from localised skin ulcers or abscesses without systemic illness to fulminant septic shock with multiple abscesses in the lungs, liver, spleen and kidneys. At least 10% of cases present with a chronic respiratory illness (sick > 2 months) mimicking tuberculosis and often with upper lobe infiltrates and/or cavities on chest radiography. As with tuberculosis, latency with reactivation decades after infection can also occur, although this is rare. Confirmation of diagnosis is by culture of B. pseudomallei from blood, sputum, throat swab or other samples. Microbiology laboratories need to be informed of the possibility of melioidosis, as those not familiar with it can misidentify the organism. Antibiotic therapy is initial intensive therapy with i.v. ceftazidime or meropenem or imipenem +/- cotrimoxazole for > or = 10 days, followed by eradication therapy with cotrimoxazole +/- doxycycline +/- chloramphenicol (first 4 weeks only) for > or = 3 months. Melioidosis has been increasingly recognised in returning travellers in Europe and recently melioidosis and colonisation with B. pseudomallei have been documented in cystic fibrosis patients visiting or resident in endemic areas.

Alcoholism↗

Proteomic-based identification of novel EV-derived protein antibodies biomarkers for melioidosis diagnosis.

Melioidosis, caused by Burkholderia pseudomallei (Bp), is a life-threatening disease characterized by diverse clinical manifestations and limited diagnostic capabilities. Extracellular vesicles (EVs) have emerged as critical carriers of novel antibody targets for serodiagnosis. In this study, we established a Bp-infected BEAS-2B cell model (Bp/BEAS-2B) and isolated EV from both Bp and Bp/BEAS-2B cells to generate EV proteome, identifying potential antigenic biomarkers for melioidosis diagnosis. Bioinformatics analysis identified PPEP and POMCR proteins as candidate antigens, with BLF1 and omp A serving as positive controls. Using a self-developed IgM-ELISA, serum samples from 43 melioidosis patients and 47 healthy volunteers were analyzed to detect antibodies against these antigens. Anti-POMCR IgM demonstrated exceptional diagnostic performance, with an AUC of 0.9872 (95% CI: 0.9713-1.003), sensitivity of 93.02% and specificity of 97.92% at a cutoff value of OD450 = 0.118. Similarly, IgM against PPEP, BLF1, and omp A also showed high diagnostic accuracy, with AUC values of 0.969, 0.9621, and 0.976, respectively. The accuracy of anti-POMCR and anti-PPEP were 96.43% and 95.54%, respectively, equivalent to anti-omp A (93.75%) and anti-BLF1 (91.96%). Antibodies to EV-derived proteins effectively differentiated melioidosis patients from other bacterial infections and healthy volunteers, highlighting their clinical potential as diagnostic tools for melioidosis.

Humans↗

Detection of Pseudomonas pseudomallei antigen in urine for the diagnosis of melioidosis.

An enzyme-linked immunosorbent assay using a fluorescein isothiocyanate (FITC)-anti-FITC amplification system, has been developed to detect Pseudomonas pseudomallei antigen in urine. The assay was evaluated in 135 patients with acute melioidosis, 194 hospitalized patients with other disorders, and 40 healthy controls. Antigen was detected in the urine of 123 (91%) patients with melioidosis. Urinary antigen was found in 85 (96%) of 89 patients with septicemic melioidosis, all six patients with P. pseudomallei urinary tract infection, and 32 (80%) of 40 patients with other localized infections. Antigen was not detected in the urine of 40 healthy individuals, but the urine of 16 (8%) of 194 hospitalized patients with diagnoses other than melioidosis gave a positive result. Of the false-positive results, 13 of 16 were associated with bacteriuria > or = 10(4) colony-forming units/ml. At a cutoff titer of 1:10, the sensitivity and specificity of the test were 81% and 96%, respectively. Enzyme immunoassay detection of urinary antigen is a valuable and rapid laboratory test for the early diagnosis of acute melioidosis.

Acute Disease↗

Melioidosis in the Northern Territory of Australia.

Melioidosis is being diagnosed with increasing frequency in the northern part of the Northern Territory, but the mortality rate remains high in the acute septicaemic form of the disease largely because of associated chronic debilitating illnesses. This paper reviews epidemiological and clinical features of human melioidosis in 37 cases seen between 1960 and 1979. Infection with Pseudomonas pseudomallei is most often contracted during the wet season by persons who have regular contact with soil or ground water, probably through pre-existing skin lesions or penetrating wounds and, occasionally, through the genitourinary tract. The clinical features of melioidosis are protean, and definitive diagnosis can only be made by bacterial culture. Certain strongly indicative features, however, may justify vigorous early treatment with antibiotics (tetracycline or doxycycline in some combination with chloramphenicol, kanamycin or trimethoprim/sulphamethoxazole) which can be life-saving in fulminant septicaemic melioidosis. These indicative features are a severely prostrating fever with signs of respiratory tract infection in a patient with a chronic debilitating condition (particularly chronic alcoholism, diabetes mellitus, malnutrition or leprosy), with regular soil contact, and with chronic or recurrent skin lesions or a recent history of a penetrating wound. In subacute or chronic forms of melioidosis, which usually localize in an organ system, the diagnosis is commonly an unexpected bacteriological finding and the prognosis is generally good.

Adolescent↗

Pseudomonas pseudomallei and melioidosis, with special reference to the status in Thailand.

Melioidosis is a long-known disease since 1912, but only quite recently we have obtained the knowledges about its actual clinical and epidemiological features. The disease is so unique in having a wide spectrum of disease course and clinical manifestation. The causative agent, P. pseudomallei, is free-living bacterium in the natural environments (soil and surface water) of tropical and subtropical areas. Just like legionnaires' disease, melioidosis is a good example of infectious disease in which pneumonia is produced by inhalation of contaminated soil dusts or water droplets. The infection becomes dormant for years, but with a chance of recrudescence under a variety of insults to the host resistance. The disease, may it be acute or chronic, will be symptomatically confused with malaria, typhoid fever, leptospirosis, septicemia caused by other gram-negative bacteria, tuberculosis and mycotic infections. Isolation of the causative agent from clinical specimens is the only reliable method for diagnosis. Because of the increasing clinical awareness and the development of diagnostic methods, the reported cases of melioidosis have numbered almost one thousand in Thailand during the past 20 years. This country has now the most ample clinical experiences on melioidosis. We have reviewed the history of melioidosis research from bacteriological, immunological, clinical and epidemiological viewpoints, especially including the recent reports in Thailand.

Humans↗

An indirect ELISA for the diagnosis of melioidosis.

BACKGROUND & OBJECTIVES: Very little information is available on melioidosis in India. This disease caused by Burkholderia pseudomallei is not often considered as a differential diagnosis and patients are not usually investigated for it. Thus we are unaware of its prevalence in India. This study was undertaken to detect the presence of melioidosis in patients presenting with pyrexia of unknown origin (PUO) using an indirect ELISA. METHODS: The well established ELISA technique was adapted to detect melioidosis in patients attending the Christian Medical College and Hospital, Vellore and to provide a serological test using reagents with a reasonable shelf-life. The ELISA is designed to detect IgG antibodies to B. pseudomallei in serum samples. RESULTS: A cut-off optical density (OD) of 0.36 (mean +/- 2 SD of healthy controls) was chosen as diagnostic criterion for the diseased group. The mean OD values in the sera of patients with culture proven melioidosis was significantly (P < 0.001) higher than that of healthy controls. INTERPRETATION & CONCLUSION: The indirect ELISA was simple to perform and may be recommended as a diagnostic serological test when melioidosis is considered as a differential diagnosis.

Adolescent↗

Serodiagnosis of melioidosis by a competitive enzyme-linked immunosorbent assay using a lipopolysaccharide-specific monoclonal antibody.

Burkholderia pseudomallei is the causative agent of melioidosis, a severe and potentially fatal infectious disease in humans known to be endemic in Southeast Asia and northern Australia. The infection is also increasingly recognized in various animal species with a potential to spread to humans. With the potential as a biological warfare agent, specific serodiagnosis of melioidosis for surveillance in large populations at risk, humans or animals, would be highly valuable. In this study, a competitive enzyme-linked immunosorbent assay (ELISA) using a lipopolysaccharide-specific monoclonal antibody was developed. The assay provides high specificity, based on a previously described monoclonal antibody to a specific epitope on the lipopolysaccharide (LPS) of B. pseudomallei. The assay sensitivity of 96.0% and specificity of 100% were achieved at a cutoff value of 50% inhibition in human culture-proven melioidosis cases. An optimal cutoff value of 65% inhibition for sera from a melioidosis endemic area was obtained by ROC analysis and resulted in an assay specificity of 86.2%, while maintaining assay sensitivity of 92.0%. A potential application of the assay in the serodiagnosis of melioidosis in animal species was also evaluated usina dolphin sera with satisfactory results.

Animals↗

Melioidosis in the Americas.

Melioidosis is a potentially severe bacterial infection caused by Burkholderia pseudomallei. There has been growing awareness of the disease in the Americas, particularly since the Vietnam conflict when it was diagnosed in returning service personnel. Accidental laboratory exposure indicates the difficulty making a culture-based diagnosis when melioidosis has not been considered in the differential diagnosis. Melioidosis is most likely underdiagnosed in tropical Central and South America where conditions are more suited to persistence of B. pseudomallei in the environment. Recent melioidosis case clusters in northeastern Brazil highlight the threat posed to rural populations located far from specialist services. Increased clinical awareness of the disease and improvements in laboratory diagnostic methods are likely to bring wider recognition of melioidosis in the Americas.

Americas↗

Discriminant analysis among septicemic melioidosis and other bacterial septicemia.

The clinical manifestations of septicemic melioidosis and other bacterial septicemia were studied at Srinagarind Hospital, Khon Kaen University. Forty-three cases of septicemic melioidosis and 68 non-melioidosis septicemia cases were analysed. By univariate analysis, the following clinical features are associated with septicemic melioidosis: male patients; age below 45 years; underlying diabetes mellitus or renal failure; pulmonary infection, impending respiratory failure and multiorgan involvement, while abdominal pain and urinary tract infection were more common in non-melioidosis septicemia. By using discriminant analysis and logistic regression, 3 features (diabetes mellitus, multiorgan involvement, and no abdominal pain or pulmonary infection) could discriminate the two groups with the accuracy of more than 85 per cent.

Adult↗

BALB/c and C57Bl/6 mice infected with virulent Burkholderia pseudomallei provide contrasting animal models for the acute and chronic forms of human melioidosis.

Burkholderia pseudomallei is the aetiological agent of melioidosis, a life-threatening bacterial disease occurring in many species of animals, including man. Infection in humans commonly manifests as one of three clinical presentations: acute, subacute or chronic disease. Investigations were undertaken to assess the suitability of BALB/c and C57Bl/6 mice as animal models for the different forms of human melioidosis. The course of infection in BALB/c mice was similar to that which occurs in acute human infection. By contrast, infection of C57Bl/6 mice appeared to mimic chronic human melioidosis. While BALB/c mice suffered a rapidly-progressive bacteraemia which resulted in host death by 96 h, C57Bl/6 mice were able to prevent this, and typically remained asymptomatic for up to 6 weeks. LD50 values of 4 cells and 2.5 x 10(4) cells for BALB/c and C57Bl/6 mice, respectively, reflect these observations. The heightened level of resistance to B. pseudomallei observed in C57Bl/6 mice was suggested to have a genetic basis, when the susceptibilities of first filial and reciprocal backcross generations were examined. Growth kinetics of B. pseudomallei within BALB/c and C57Bl/6 peritoneal exudate cell (PEC) cultures were examined to investigate PEC microbicidal efficiency as a determinant of host susceptibility. C57Bl/6 PEC cultures exhibited greater microbicidal efficiency towards B. pseudomallei when compared to BALB/c cells, indicating that susceptibility may be determined by non-specific, cellular mechanisms. Collectively, these results suggest that the BALB/c and C57Bl/6 strains of mice may provide excellent models for acute and chronic human melioidosis, respectively.

Animals↗

Blood culture techniques for the diagnosis of melioidosis.

The effects of variations in laboratory technique on the speed and sensitivity of isolation of Pseudomonas pseudomallei from blood were evaluated prospectively. Pseudomonas pseudomallei was isolated from 154 of 546 cultures from 325 patients with suspected or confirmed melioidosis. Subcultures after 12 to 24 and 36 to 48 hours of incubation were positive in 52.3% and 80.8% respectively. The yields from 20 ml (blood to broth ratio 1:4) and 50 ml (blood to broth ratio 1:10) brain heart infusion broth bottles were equivalent in patients not receiving treatment for melioidosis. During therapy, the 50 ml bottles grew Pseudomonas pseudomallei significantly faster than the 20 ml bottles (p less than 0.01), and gave a higher overall yield for cultures processed in antimicrobial removal devices (p less than 0.05). These devices themselves increased the speed of isolation of the organism from treated patients (p less than 0.01). In most cases, all bottles collected from a patient before treatment were positive, and a single 20 ml bottle had an estimated relative sensitivity of 85.7% (95% confidence interval 77.1-94.3%). Early subculture should be employed routinely for the laboratory diagnosis of septicaemic melioidosis. However, blood culture techniques do not need to be sophisticated. Culture of 5 ml blood in 20 ml broth is a simple and sensitive procedure suitable for regions where melioidosis is currently under-diagnosed.

Bacteriological Techniques↗

Amoxycillin-clavulanic acid treatment of melioidosis.

Melioidosis is a serious infection with high acute mortality, and a high rate of relapse despite protracted antimicrobial treatment. The current recommended conventional oral treatment regimen is a 4-drug combination of high-dose chloramphenicol, doxycycline and trimethoprim-sulphamethoxazole given for between 6 weeks and 6 months. We have evaluated prospectively the use of amoxycillin-clavulanic acid, to which Pseudomonas pseudomallei is consistently sensitive in vitro, for the oral maintenance treatment of melioidosis. Amoxycillin-clavulanic acid was used either as sole treatment of localized disease, or as maintenance therapy following either parenteral ceftazidime or the conventional 4-drug regime; 20 patients with localized infections and 26 with septicaemic melioidosis received a median of 7.5 (2-12) weeks treatment. After a mean follow-up period of 6 months (range 1-19), 31 patients (67%) remain free of disease. The drug was well tolerated. Three patients had fatal relapses, one other died suddenly at home, and another died from underlying promyelocytic leukaemia. The remaining 10 relapses were treated successfully. Resistance developed in one case. Amoxycillin-clavulanic acid is a safe alternative to the conventional 4-drug antimicrobial combination for the oral treatment of melioidosis. It may be of particular value in children, pregnant women, and in infections with Ps. pseudomallei resistant to the potentially toxic conventional regimen, but the optimum dose and duration of therapy need to be established.

Adolescent↗

Burkholderia pseudomallei strain type, based on pulsed-field gel electrophoresis, does not determine disease presentation in melioidosis.

Melioidosis, the infection due to Burkholderia pseudomallei, may present with a spectrum of severity and may affect any site in the body. Differential strain virulence and tropism suggested by previous studies would have implications for virulence and vaccine work. We explored clinical correlations using pulsed-field gel electrophoresis (PFGE) typing in a well-characterised clinical collection. Two methods of analysis were used based on band-based similarity values: first, a conventional cluster analysis formed by the unweighted paired group mean analysis, and second, an analysis of the distribution of the "within-group" and "between-group" Dice coefficient. Clinical isolates from 114 cases of melioidosis occurring in the Northern Territory, Australia were studied; 71 strain types were defined with a Simpson's index of 0.91. No correlation was found between strain type and disease severity or site of melioidosis on presentation, with no differences in similarity values found when comparing within and between-groups. In particular, isolates from patients with neurological melioidosis were not clustered. There was evidence of geographical localisation. This study suggests that the variation in strain type may not be as important as host and environmental factors in determining the pattern of disease.

Australia↗