Ho, Cassandra

Freeman, Kevin

Woerle, Celeste

Mahoney, Mila

Mayo, Mark

Baird, Robert

Meumann, Ella

Currie, Bart

2025-02-08

Melioidosis, an infection with the bacterium , is highly endemic in the Top End of the Northern Territory of Australia. The indirect haemagglutination assay (IHA) is the most widely used serology test globally, but it is not standardised among the limited number of laboratories that perform it. While concerns have been raised about the sensitivity of IHA early in melioidosis infections, the advantage of IHA over more recently developed ELISAs is that testing serial dilutions allows a titre to be recorded. While in Australia a titre of 1:40 or higher is considered positive, the specificity at these low positive titres remains uncertain. However, a high titre is considered to represent recent or past true infection with , rather than cross-rection with other environmental species. Also, the natural history of IHA titres over time, in both asymptomatic infection and melioidosis has been little studied. We have assessed the clinical status and serology time courses of all 534 patients who had an IHA titre of 1:640 or higher, over a 20-year period. Of these, 324 (60.7%) were diagnosed with culture-confirmed melioidosis, with varying time courses of diagnosis of melioidosis in relation to the high serology. Of the 210 without confirmed melioidosis, 22 (10.5%) were considered highly likely to be melioidosis despite being culture-negative, and these were all treated as melioidosis. In the remainder, titres mostly gradually decreased over time, but the majority remained seropositive. A small number who had not been treated for melioidosis continued to have high IHA titres over years and activation from latency with a new diagnosis of melioidosis was occasionally documented. This study highlights the importance of a full clinical workup in those found to have high titre melioidosis serology as well as subsequent close clinical surveillance and where resources allow, yearly IHA in those not confirmed or treated as melioidosis.

Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT 0811, Australia.

Northern Territory Medical Program, Flinders University, Darwin, NT 0811, Australia.

Territory Pathology, Royal Darwin Hospital, Darwin, NT 0811, Australia.

Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT 0811, Australia.

Territory Pathology, Royal Darwin Hospital, Darwin, NT 0811, Australia.

Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT 0811, Australia.

Territory Pathology, Royal Darwin Hospital, Darwin, NT 0811, Australia.

Department of Infectious Diseases, Royal Darwin Hospital, Darwin, NT 0811, Australia.

Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT 0811, Australia.

Territory Pathology, Royal Darwin Hospital, Darwin, NT 0811, Australia.

Department of Infectious Diseases, Royal Darwin Hospital, Darwin, NT 0811, Australia.

Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT 0811, Australia.

Northern Territory Medical Program, Flinders University, Darwin, NT 0811, Australia.

Department of Infectious Diseases, Royal Darwin Hospital, Darwin, NT 0811, Australia.

Pathogens . 2025 Feb 8;14(2):165. doi: 10.3390/pathogens14020165.

2076-0817

0000-0001-7993-820X

0000-0002-8878-8837

https://pubmed.ncbi.nlm.nih.gov/40005540/?otool=iaurydwlib

https://hdl.handle.net/10137/14170

Burkholderia pseudomallei

indirect haemagglutination assay

latency

melioidosis

neglected tropical disease

serology

Melioidosis

Humans

Retrospective Studies

Northern Territory

Hemagglutination Tests

Burkholderia pseudomallei

Male

Female

Antibodies, Bacterial

Middle Aged

Adult

Aged

Adolescent

Young Adult

Sensitivity and Specificity

Clinical Implications of High Melioidosis Serology Indirect Haemagglutination Assay Titre: A 20-Year Retrospective Study from the Top End of the Northern Territory, Australia.

Journal Article

Publication