Fatal Chromobacterium violaceum septicaemia in northern Laos, a modified oxidase test and post-mortem forensic family G6PD analysis

<p>Abstract</p> <p>Background</p> <p><it>Chromobacterium violaceum </it>is a Gram negative facultative anaerobic bacillus, found in soil and stagnant water, that usually has a violet pigmented appearance on agar culture. It is rarely described as a human pathogen, mostly from tropical and subtropical areas.</p> <p>Case presentation</p> <p>A 53 year-old farmer died with <it>Chromobacterium violaceum </it>septicemia in Laos. A modified oxidase method was used to demonstrate that this violacious organism was oxidase positive. Forensic analysis of the glucose-6-phosphate dehydrogenase genotypes of his family suggest that the deceased patient did not have this possible predisposing condition.</p> <p>Conclusion</p> <p><it>C. violaceum </it>infection should be included in the differential diagnosis in patients presenting with community-acquired septicaemia in tropical and subtropical areas. The apparently neglected but simple modified oxidase test may be useful in the oxidase assessment of other violet-pigmented organisms or of those growing on violet coloured agar.</p

Urine Antibiotic Activity in Patients Presenting to Hospitals in Laos: Implications for Worsening Antibiotic Resistance

Widespread use of antibiotics may be important in the spread of antimicrobial resistance. We estimated the proportion of Lao in- and outpatients who had taken antibiotics before medical consultation by detecting antibiotic activity in their urine added to lawns of Bacillus stearothermophilus, Escherichia coli, and Streptococcus pyogenes. In the retrospective (N = 2,058) and prospective studies (N = 1,153), 49.7% (95% confidence interval [CI] = 47.4–52.0) and 36.2% (95% CI = 33.4–38.9), respectively, of Vientiane patients had urinary antibiotic activity detected. The highest frequency of estimated antibiotic pre-treatment was found in patients recruited with suspected central nervous system infections and community-acquired septicemia (both 56.8%). In Vientiane, children had a higher frequency of estimated antibiotic pre-treatment than adults (60.0% versus 46.5%; P < 0.001). Antibiotic use based on patients histories was significantly less frequent than when estimated from urinary antibiotic activity (P < 0.0001)

An improved selective culture medium enhances the isolation of Burkholderia pseudomallei from contaminated specimens.

Burkholderia pseudomallei is a Gram-negative environmental bacterium found in tropical climates that causes melioidosis. Culture remains the diagnostic gold standard, but isolation of B. pseudomallei from heavily contaminated sites, such as fecal specimens, can be difficult. We recently reported that B. pseudomallei is capable of infecting the gastrointestinal tract of mice and suggested that the same may be true in humans. Thus, there is a strong need for new culture techniques to allow for efficient detection of B. pseudomallei in fecal and other specimens. We found that the addition of norfloxacin, ampicillin, and polymyxin B to Ashdown's medium (NAP-A) resulted in increased specificity without affecting the growth of 25 B. pseudomallei strains. Furthermore, recovery of B. pseudomallei from human clinical specimens was not affected by the three additional antibiotics. Therefore, we conclude that NAP-A medium provides a new tool for more sensitive isolation of B. pseudomallei from heavily contaminated sites

Evaluation of consensus method for the culture of Burkholderia pseudomallei in soil samples from Laos.

Background: We have previously shown that PCR following enrichment culture is the most sensitive method to detect Burkholderia pseudomallei in environmental samples. Here we report an evaluation of the published consensus method for the culture of B. pseudomallei from Lao soil in comparison with our conventional culture method and with PCR with or without prior broth enrichment. Methods: One hundred soil samples were collected from a field known to contain B. pseudomallei and processed by: (i) the conventional method, (ii-iii) the consensus method using media prepared in either Laos or Thailand, and (iv) the consensus method performed in Thailand, as well as by (v) PCR following direct extraction of DNA from soil and (vi) PCR following broth pre-enrichment. Results: The numbers of samples in which B. pseudomallei was detected were 42, 10, 7, 6, 6 and 84, respectively. However, two samples were positive by the consensus method but negative by conventional culture, and one sample was negative by PCR following enrichment although B. pseudomallei was isolated by the conventional culture method. Conclusions/Discussion: The results show that no single method will detect all environmental samples that contain B. pseudomallei. People conducting environmental surveys for this organism should be aware of the possibility of false-negative results using the consensus culture method. An approach that entails screening using PCR after enrichment, followed by the evaluation of a range of different culture methods on PCR-positive samples to determine which works best in each setting, is recommended

The Utility of Blood Culture Fluid for the Molecular Diagnosis of Leptospira: A Prospective Evaluation.

Leptospirosis is an important zoonosis worldwide, with infections occurring after exposure to contaminated water. Despite being a global problem, laboratory diagnosis remains difficult with culture results taking up to 3 months, serology being retrospective by nature, and polymerase chain reaction showing limited sensitivity. Leptospira have been shown to survive and multiply in blood culture media, and we hypothesized that extracting DNA from incubated blood culture fluid (BCF), followed by quantitative real-time polymerase chain reaction (qPCR) could improve the accuracy and speed of leptospira diagnosis. We assessed this retrospectively, using preincubated BCF of Leptospira spp. positive (N= 109) and negative (N= 63) febrile patients in Vientiane, Lao PDR. The final method showed promising sensitivities of 66% (95% confidence interval [CI]: 55-76) and 59% (95% CI: 49-68) compared with direct or direct and indirect testing combined, as the respective reference standards (specificities > 95%). Despite these promising diagnostic parameters, a subsequent prospective evaluation in a Lao hospital population (N= 352) showed that the sensitivity was very low (∼30%) compared with qPCR on venous blood samples. The disappointingly low sensitivity does suggest that venous blood samples are preferable for the clinical microbiology laboratory, although BCF might be an alternative if leptospirosis is only suspected postadmission after antibiotics have been used

Burkholderia pseudomallei Bacteria in Ornamental Fish Tanks, Vientiane, Laos, 2023

In 2019, a melioidosis case in Maryland, USA, was shown to have been acquired from an ornamental fish tank contaminated with Burkholderia pseudomallei bacteria, likely derived from Southeast Asia. We investigated the presence of B. pseudomallei in ornamental fish tanks in the endemic area of Vientiane, Laos