Authors (including presenting author) :
Wu WG(1), Luk S(1), Lee KP(1), To WK(1), Ho Alex YM(1), Hung MF(1)
Affiliation :
(1)Department of Pathology, Princess Margaret Hospital
Introduction :
From January 2015 to October 2022, we identified 38 patients with the first episode of culture-confirmed melioidosis in the Kowloon West Region, Hong Kong, of which 29 patients were admitted to the Caritas Medical Centre (CMC); seven were admitted to Princess Margaret Hospital (PMH) and two were admitted to Yan Chai Hospital (YCH). The majority of cases (30/38, 78.9%) were highly clustered in the Sham Shui Po (SSP) district. Notably, an upsurge of 18 new cases were identified from August to October 2022 after heavy rainfalls and typhoons. Pneumonia was the most common site of involvement (63.2%) among our patients. Nevertheless, melioidosis patients often present with indistinguishable features from community-acquired pneumonia and pose a significant diagnostic challenge to clinicians. Although sputum culture remains the major method of melioidosis diagnosis, the reported sensitivity varied from 51.7 to 68.5%. Prior use of beta-lactam antibiotics, for which B.pseudomallei is susceptible, further jeopardizes the culture yield. Enhanced surveillance by means of selective culture (normal flora suppressed) and real-time PCR for confirmation of B.pseudomallei was adopted in response to the upsurge of melioidosis in SSP district. Melioidosis has now become a statutorily notifiable disease in Hong Kong. Enhanced surveillance has not only improved the diagnostic yield, but also allows rapid confirmation of melioidosis to facilitate communication with the clinical team and public health authorities.
Objectives :
(1) To improve the diagnosis of melioidosis for appropriate clinical management
(2) To facilitate the laboratory confirmation of melioidosis and communication with clinical team and public health authorities
Methodology :
Selective culture by Ashdown agar is routinely added to respiratory specimens of inpatients from CMC. Ashdown agar plate was screened for the morphotype of B.pseudomallei colonies with wrinkled and pink appearance. Additionally, real-time PCR assay targeting Type III secretion system is used for detection of B.pseudomallei from culture colonies or directly from specimens.
Result & Outcome :
From 6 October 2022 to 8 January 2023, there were 7 B.pseudomallei isolates identified from 5 undiagnosed patients out of a total number of 2829 respiratory specimens (0.25%, 7/2829) from CMC using selective culture on Ashdown agar. Real-time PCR for B.pseudomallei was tested directly on 6 clinical samples with positive culture (5 sputum, 1 blood culture) and PCR was positive in all samples (100%, 6/6), with CT value ranging from 31.78 to 39.06. This can serve as a potential rapid diagnostic tool. Real-time PCR was also used to confirm the identification of B.pseudomallei colonies, and shortened the time needed for confirmation of melioidosis within one day and facilitated the reporting of results to clinicians and public health authorities.
