Epidemiology and clinical presentation of patients with melioidoisis at the District General Hospital, Chilaw

Melioidosis is a potentially fatal infection caused by the Gram negative, non-fermentative,soil bacterium,Burkholderiapseudomallei. B. pseudomalleiisan important cause of community acquired sepsis in Southeast Asia and Northern Australia [1]. Infection is acquired by inoculation of soil via breaches in the skin, inhalation of aerosolized soil or water or ingestion of natural sources of water containing the bacterium [2]. People with occupational exposure to soil, such as rice farmers, are at highest risk. However, any person exposed to soil and water containing the bacterium can be infected. Infection is morecommon in males, probably due to greater contact with soil. The commonest underlying risk factors for acquiring infection are diabetes mellitus and chronic kidney disease in adults and thalassaemia in children. Clinical presentation is variable, leading to difficulty in establishing the diagnosis. Relapses may be seen, months to years after initial infection and follow up is mandatory [3]. Melioidosis has emerged as an important infection in Sri Lanka in the recent past [4]. The District General Hospital (DGH) Chilaw is situated in the North Western Province (NWP) of Sri Lanka where the majority of the population is engaged in agriculture and fisheries.


Introduction
Melioidosis is a potentially fatal infection caused by the Gram negative, non-fermentative,soil bacterium,Burkholderiapseudomallei.
B. pseudomalleiisan important cause of community acquired sepsis in Southeast Asia and Northern Australia [1].Infection is acquired by inoculation of soil via breaches in the skin, inhalation of aerosolized soil or water or ingestion of natural sources of water containing the bacterium [2].People with occupational exposure to soil, such as rice farmers, are at highest risk.However, any person exposed to soil and water containing the bacterium can be infected.Infection is morecommon in males, probably due to greater contact with soil.The commonest underlying risk factors for acquiring infection are diabetes mellitus and chronic kidney disease in adults and thalassaemia in children.Clinical presentation is variable, leading to difficulty in establishing the diagnosis.Relapses may be seen, months to years after initial infection and follow up is mandatory [3].Melioidosis has emerged as an important infection in Sri Lanka in the recent past [4].The District General Hospital (DGH) Chilaw is situated in the North Western Province (NWP) of Sri Lanka where the majority of the population is engaged in agriculture and fisheries.

Case series
The Department of Microbiology, District General Hospital Chilaw, isolated B. pseudomalleifrom clinical specimens from 15 patients between May 2014 and December 2017.Nine isolates were identified from blood and six were identified from pus.The isolates were identified by their characteristic colony appearance on routine culture media, bipolar or "safety pin" appearance on Gram stain (Gram negative bacilli with densely staining ends and a pale centre), late oxidase positivity and unique antibiotic sensitivity pattern [5].The colony appearance of isolates was variable, ranging from smooth to dry on blood agar and non-lactose fermenting to lactose fermenting on MacConkey agar.The earthy smell of colonies was prominent in some isolates.The identity of the isolates was confirmed by polymerase chain reaction (PCR) at the Department of Microbiology, Faculty of Medicine, Colombo [6].

Results
The age range of the patients was wide, ranging from one year and four months to 67 years.The majority of patients (n=10) were middle aged (between 45-65 years) while three were children (Table 1).Out of the 12 adult patients, eight were male.Nine had diabetes mellitus while other underlying risk factors included chronic obstructive pulmonary disease, chronic kidney disease, chronic liver cell disease and pathological alcohol use.None of the children had any underlying risk condition.There were no farmers in this case series but two housewives gave a history of soil exposure through gardening.One patient was exposed to soil and water when he fell into a drain.One gave a history of tooth extraction prior to contracting parotitis.No specific exposure to soil or natural sources of water could be elicited in the other cases.
Clinical presentations ranged from septicaemia (n=3) and lung infection (n=2) with a high mortality to localized abscess with good prognosis (n=7).Four patients presented with salivary gland abscesses and two with cervical lymphadenitis.Other presentations included liver abscess, splenic abscess, cellulitis, osteomyelitis and septic arthritis.The overall case fatality rate in this series was 40% (6/15).All the patients were from the NWP (Figure 1), with the majority residing in the Puttalum District.Patients presented throughout the year and there was no seasonal preponderance.

Discussion
This case series demonstrates that melioidosis is endemic in the NWP and is a cause of community acquired infection, ranging from severe sepsis to localized abscess formation.The varying clinical presentations of melioidosis require that the clinician has a high index of suspicion and includes melioidosis in the differential diagnosis of a wide variety of community acquired infections in children and adults.
Although rice farming is the most prominent high risk occupation for acquisition of melioidosis, this case series shows that melioidosis may infect other persons, such as housewives, fishermen and even toddlers.A tradition of walking barefooted and drinking water from natural, untreated sources such as wells may contribute to increased risk.
Confirmation of the diagnosis necessitates bacterial culture of patient specimens or detection of high antibody levels.It is vital that patient specimens are submitted to the clinical microbiology laboratory early in the acute phase of the infection.It is likely that many cases of melioidosis remain undiagnosed due to failure to submit specimens for microbiology.This is particularly true in relation to suppurative lymphadenitis where biopsy specimens are often sent only for histology and not for bacterial culture.
Rapid diagnosis is the key to early, effective therapy, which may reduce the high case fatality rate seen in this case series.The majority of patients, however, had a favorable outcome when treated appropriately (intravenous ceftazidime or meropenem for 2-6 weeks, with or without cotrimoxazole, followed by long term oral antibiotics during the eradication phase) [8].Follow up to ensure compliance with the eradication phase and to detect relapses is recommended.
Similar to most studies, the most prominent underlying risk factor in this case series was diabetes.Effective, community-based diabetes detection and control may reduce the incidence and severity of melioidosis.

Figure 1 .
Figure 1.Geographic location of melioidosis patients from Puttalam District presenting to DGH Chilaw