Determinants of Recurrent Melioidosis

Recurrent melioidosis represents relapse following failure to eradicate bacteria responsible for the primary infection or re-infection with a new strain. The first results chapter (chapter 3) evaluates the proportion of recurrent melioidosis due to relapse versus re-infection. Isolates from the same patient with an identical genotype were considered as relapse and those with a different genotype as re-infection. Three quarters of recurrent cases were due to relapse and one quarter were due to re-infection. There are two ways in which this approach could be confounded. First, ‘re-infection’ could actually represent relapse if primary infection was caused by simultaneous infection with multiple B. pseudomallei strains, followed by chance selection of different strains from the two episodes for genotyping. The chance of this mistake occurring is based on the rate of polyclonal B. pseudomallei infection. Chapter 4 describes the rate of polyclonal infection in a large group of unselected patients in northeast Thailand, which was very low (2/133 cases, 1.5%). Second, ‘relapse’ could actually represent reinfection in the event that re-infection was caused by a B. pseudomallei strain that was by chance identical to the primary strain. The probability of this happening is based on the degree of genetic diversity of B. pseudomallei in the environment. Chapter 5 demonstrates that the population of B. pseudomallei in even a small sampling site is extremely diverse. Thus, it is unlikely that the assessment of the causes of recurrent melioidosis contained significant errors due to polyclonal infection or low genetic diversity of the organism. Chapter 6 examines specific risk factors of relapse and reinfection. Duration and choices of antibiotics used for the primary episode were major determinants of relapse. Chapter 7 compares the clinical manifestations of relapse and re-infection and develops a simple scoring index to predict relapse or re-infection in patients presenting with recurrent melioidosis

Global Burden and Challenges of Melioidosis

This is a reprint of articles from the Special Issue published online in the open access journal Tropical Medicine and Infectious Disease (ISSN 2414-6366) from 2018 to 2019 (available at: https://www. mdpi.com/journal/tropicalmed/special issues/melioidosis

Impact of low blood culture usage on rates of antimicrobial resistance

Abstract Objectives The magnitude of impact caused by low blood culture utilization on estimates of the proportions and incidence rates of antimicrobial-resistant (AMR) bacterial infections is largely unknown. Methods We used routine electronic databases of microbiology, hospital admission and drug prescription at Sunpasitthiprasong Hospital, Ubon Ratchathani, Thailand, from 2011 to 2015, and bootstrap simulations. Results The proportions of Escherichia coli and Klebsiella pneumoniae bacteraemias caused by 3rd generation cephalosporin resistant isolates (3GCREC and 3GCRKP) were estimated to increase by 13 and 24 percentage points (from 44% to 57% and from 51% to 75%), respectively, if blood culture utilization rate was reduced from 82 to 26 blood culture specimens per 1,000 patient-days. Among patients with hospital-origin bloodstream infections, the proportion of 3GCREC and 3GCRKP whose first positive blood culture was taken within ±1 calendar day of the start of a parenteral antibiotic at the study hospital was substantially lower than those whose first positive blood culture was taken later into parenteral antibiotic treatment (30% versus 79%, p<0.001; and 37% versus 86%, p<0.001). Similar effects were observed for methicillin-resistant Staphylococcus aureus, carbapenem-resistant Acinetobacter spp. and carbapenem-resistant Pseudomonas aeruginosa. Conclusion Impacts of low blood culture utilization rate on the estimated proportions and incidence rates of AMR infections could be high. We recommend that AMR surveillance reports should additionally include blood culture utilization rate and stratification by exposure to a parenteral antibiotic at the hospital

Development of ceftazidime resistance in an acute Burkholderia pseudomallei infection.

Burkholderia pseudomallei, a bacterium that causes the disease melioidosis, is intrinsically resistant to many antibiotics. First-line antibiotic therapy for treating melioidosis is usually the synthetic β-lactam, ceftazidime (CAZ), as almost all B. pseudomallei strains are susceptible to this drug. However, acquired CAZ resistance can develop in vivo during treatment with CAZ, which can lead to mortality if therapy is not switched to a different drug in a timely manner. Serial B. pseudomallei isolates obtained from an acute Thai melioidosis patient infected by a CAZ susceptible strain, who ultimately succumbed to infection despite being on CAZ therapy for the duration of their infection, were analyzed. Isolates that developed CAZ resistance due to a proline to serine change at position 167 in the β-lactamase PenA were identified. Importantly, these CAZ resistant isolates remained sensitive to the alternative melioidosis treatments; namely, amoxicillin-clavulanate, imipenem, and meropenem. Lastly, real-time polymerase chain reaction-based assays capable of rapidly identifying CAZ resistance in B. pseudomallei isolates at the position 167 mutation site were developed. The ability to rapidly identify the emergence of CAZ resistant B. pseudomallei populations in melioidosis patients will allow timely alterations in treatment strategies, thereby improving patient outcomes for this serious disease

Consensus on the development of vaccines against naturally acquired melioidosis.

Several candidates for a vaccine against Burkholderia pseudomallei, the causal bacterium of melioidosis, have been developed, and a rational approach is now needed to select and advance candidates for testing in relevant nonhuman primate models and in human clinical trials. Development of such a vaccine was the topic of a meeting in the United Kingdom in March 2014 attended by international candidate vaccine developers, researchers, and government health officials. The focus of the meeting was advancement of vaccines for prevention of natural infection, rather than for protection from the organism's known potential for use as a biological weapon. A direct comparison of candidate vaccines in well-characterized mouse models was proposed. Knowledge gaps requiring further research were identified. Recommendations were made to accelerate the development of an effective vaccine against melioidosis

Local and timely antimicrobial resistance data for local and national actions: the early implementation of an automated tool for data analysis at local hospital level in Thailand

Background In low- and middle-income countries (LMICs), hospitals can rarely utilize their own antimicrobial resistance (AMR) data in a timely manner. Objectives To evaluate the utility of local AMR data generated by an automated tool in the real-world setting. Methods From 16 December 2022 to 10 January 2023, on behalf of the Health Administration Division, Ministry of Public Health (MoPH) Thailand, we trained 26 public tertiary-care and secondary-care hospitals to utilize the AutoMated tool for Antimicrobial resistance Surveillance System (AMASS) with their own microbiology and hospital admission data files via two online meetings, one face-to-face meeting and online support. All meetings were recorded on video, and feedback was analysed. Results Twenty-five hospitals successfully generated and shared the AMR reports with the MoPH by 28 February 2023. In 2022, the median frequency of hospital-origin bloodstream infections (BSIs) caused by carbapenem-resistant Escherichia coli (CREC) was 129 (range 0–1204), by carbapenem-resistant Klebsiella pneumoniae (CRKP) was 1306 (range 0–5432) and by carbapenem-resistant Acinetobacter baumannii (CRAB) was 4472 (range 1460–11 968) per 100 000 patients tested for hospital-origin BSI. The median number of all-cause in-hospital deaths with hospital-origin AMR BSI caused by CREC was 1 (range 0–18), by CRKP was 10 (range 0–77) and by CRAB was 56 (range 7–148). Participating hospitals found that the data obtained could be used to support their antimicrobial stewardship and infection prevention control programmes. Conclusions Local and timely AMR data are crucial for local and national actions. MoPH Thailand is inviting all 127 public tertiary-care and secondary-care hospitals to utilize the AMASS. Using any appropriate analytical software or tools, all hospitals in LMICs that have electronic data records should analyse and utilize their data for immediate actions

What’s wrong in the control of antimicrobial resistance in critically ill patients from low- and middle-income countries?

Critical care environments are magnets for drug-resistant organisms. Patients are extremely vulnerable to nosocomial infections due to the severity of their clinical condition, the siting of multiple invasive medical devices and their proximity to other infected patients. Use of broad spectrum antibiotics is high in intensive care units (ICUs) compared to other hospital departments, making selection of drug-resistant bacteria more likely. In low- and middle-income countries (LMICs), nosocomial infections are thought to be more common than in high-income countries (HICs), although objective incidence rates are unknown, since routine bacteriological surveillance does not usually occur. In tropical settings, severe malaria is a common cause of sepsis, and antimalarial drug resistance is an increasing problem. Here, we give our perspective on the important threat of antimicrobial drug resistance (AMR) in critical care patients in LMICs, contributing factors and initiatives to address this. For further reading, we refer to the supplement listing additional references

Development of a prototype Lateral Flow Immunoassay (LFI) for the rapid diagnosis of melioidosis

Burkholderia pseudomallei is a soil-dwelling bacterium and the causative agent of melioidosis. Isolation of B. pseudomallei from clinical samples is the &ldquo;gold standard&rdquo; for the diagnosis of melioidosis; results can take 3&ndash;7 days to produce. Alternatively, antibody-based tests have low specificity due to a high percentage of seropositive individuals in endemic areas. There is a clear need to develop a rapid point-of-care antigen detection assay for the diagnosis of melioidosis. Previously, we employed In vivo Microbial Antigen Discovery (InMAD) to identify potential B. pseudomallei diagnostic biomarkers. The B. pseudomallei capsular polysaccharide (CPS) and numerous protein antigens were identified as potential candidates. Here, we describe the development of a diagnostic immunoassay based on the detection of CPS. Following production of a CPS-specific monoclonal antibody (mAb), an antigen-capture immunoassay was developed to determine the concentration of CPS within a panel of melioidosis patient serum and urine samples. The same mAb was used to produce a prototype Active Melioidosis Detect Lateral Flow Immunoassay (AMD LFI); the limit of detection of the LFI for CPS is comparable to the antigen-capture immunoassay (~0.2 ng/ml). The analytical reactivity (inclusivity) of the AMD LFI was 98.7% (76/77) when tested against a large panel of B. pseudomallei isolates. Analytical specificity (cross-reactivity) testing determined that 97.2% of B. pseudomallei near neighbor species (35/36) were not reactive. The non-reactive B. pseudomallei strain and the reactive near neighbor strain can be explained through genetic sequence analysis. Importantly, we show the AMD LFI is capable of detecting CPS in a variety of patient samples. The LFI is currently being evaluated in Thailand and Australia; the focus is to optimize and validate testing procedures on melioidosis patient samples prior to initiation of a large, multisite pre-clinical evaluation

Misidentification of Burkholderia pseudomallei as Acinetobacter species in northern Thailand

Background Burkholderia pseudomallei is the causative agent of melioidosis, a disease endemic throughout the tropics. Methods A study of reported Acinetobacter spp. bacteraemia was performed at Chiang Rai provincial hospital from 2014 to 2015. Isolates were collected and tested for confirmation. Results A total of 419 putative Acinetobacter spp. isolates from 412 patients were re-identified and 5/419 (1.2%) were identified as B. pseudomallei. Four of the five patients with melioidosis died. An estimated 88/419 (21%) isolates were correctly identified as Acinetobacter spp. Conclusion Misidentification of Acinetobacter spp. as B. pseudomallei or other bacteria is not uncommon and programmes to address these shortfalls are urgently required