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Published Date: 2012-08-14 16:18:44
Subject: PRO/EDR> Melioidosis - Australia (04): (NT) cases increase
Archive Number: 20120814.1243818

MELIOIDOSIS - AUSTRALIA (04): (NORTHERN TERRITORY) CASES INCREASE
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Date: Sun 12 Aug 2012
Source: The Australian, Australian Associated Press (AAP) report [edited]
http://www.theaustralian.com.au/news/breaking-news/spike-in-deadly-soil-bacteria-in-nt/story-fn3dxiwe-1226448547848

There has been an alarming increase in the Northern Territory of Australia of people infected with deadly bacteria found in the soil.

Infectious disease physician Bart Currie from Royal Darwin Hospital has aggregated data from the last 23 years and has found a significant spike in cases of people infected with melioidosis. The bacteria [_Burkholderia pseudomallei_] enter the body often through cracks in feet. They can also become airborne when soil is disturbed. The organism infects the blood, leads to pneumonia, and has a high mortality rate of 15 per cent.

Since 1989, there have been 783 cases, with 107 deaths. However, data analysis showed that 252 of the 783 cases and 30 deaths occurred over the last 3 years.

It used to be that only 25 people were diagnosed with the bacterium each year but that's jumped to almost 90 a year over the last 3 years, with most cases recorded in Darwin.

Director of emergency medicine at Royal Darwin Hospital Dr Didier Palmer presented Dr Currie's data at an emergency medicine symposium held in Cairns on Sun 12 Aug 2012. "That is a massive increase for a disease that has a massive mortality," Dr Palmer told AAP.

He said immunocompromised people mainly became infected, for example people suffering from chronic alcoholism, diabetes, or those being treated for cancer. He believes there has been an increase in Darwin because of increased construction, which mobilizes the bacteria and exposes people to more soil.

The influx of indigenous people to Darwin because of the intervention is also believed to contribute to the spike as well as increased rainfall in the Top End. About 50 per cent of people diagnosed with the bacteria are Aboriginal.

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[Most of the reports of melioidosis from Australia originate in the Northern Territory; however, the disease is also endemic in Queensland, which is east of the Northern Territory. The disease usually occurs during the rainy season and may be accentuated by extreme flooding from rain and also from tsunamis, as occurred in 2005 in Thailand. A few cases were diagnosed after survivors returned to their home country of Finland.

_Burkholderia pseudomallei_ exists as an environmental saprophyte living in soil and surface water in endemic areas (South East Asia and northern, tropical Australia), particularly in rice paddies. In endemic countries, the organism exists primarily in focal areas and is not equally distributed throughout the landscape. Sporadic cases have been reported to have been acquired in parts of Africa and the Americas. The organism may exist in a viable, non-cultivable state in the environment, interacting with other organisms, particularly protozoa, which might explain its adaptation to an intracellular niche. 2 outbreaks in Australia have also implicated potable water supplies rather than surface water as a potential source of the infection.

Melioidosis is a disease of the rainy season in the endemic areas. It mainly affects people who have direct contact with soil and water. Many have an underlying predisposing condition such as diabetes (commonest risk factor), renal disease, cirrhosis, thalassemia, alcohol dependence, immunosuppressive therapy, chronic obstructive lung disease, cystic fibrosis, and excess kava consumption. Kava is an herbal member of the pepper family that can be associated with chronic liver disease.

Melioidosis may present at any age, but peaks in the 4th and 5th decades of life, affecting men more than women. In addition, although severe fulminating infection can and does occur in healthy individuals, severe disease and fatalities are much less common in those without risk factors.

The most commonly recognized presentation of melioidosis is pneumonia, associated with high fever, significant muscle aches, chest pain, and -- although the cough can be nonproductive -- respiratory secretions can be purulent, significant in quantity, and associated with on-and-off bright, red blood. The lung infection can be rapidly fatal -- with bacteremia and shock -- or somewhat more indolent.

Acute melioidosis septicemia is the most severe complication of the infection. It presents as a typical sepsis syndrome with hypotension, high cardiac output, and low systemic vascular resistance. In many cases, a primary focus in the soft tissues or lung can be found. The syndrome, usually in patients with risk factor comorbidities, is characteristically associated with multiple abscesses involving the cutaneous tissues, the lung, the liver, and spleen, and a very high mortality rate of 80 to 95 per cent. With prompt optimal therapy, the case fatality rate can be decreased to 40 to 50 per cent.

The melioidosis bacillus is intrinsically insensitive to many antimicrobials. It should be noted that bioterrorism strains may be engineered to be even more resistant. _B. pseudomallei_ is usually inhibited by tetracyclines, chloramphenicol, trimethoprim-sulfamethoxazole (SXT), antipseudomonal penicillins, carbapenems, ceftazidime, and amoxicillin/clavulanate or ampicillin/sulbactam. Ceftriaxone and cefotaxime have good in vitro activity but poor efficacy; and cefepime did not appear, as well, to be equivalent to ceftazidime in a mouse model. The unusual antimicrobial profile of resistance to colistin and polymyxin B and the aminoglycosides but sensitivity to amoxicillin/clavulanate is a useful tool to consider in treatment of infection with the organism.

The randomized and quasi-randomized trials comparing melioidosis treatment have been reviewed, and it was found that the formerly standard therapy of chloramphenicol, doxycycline, and SXT combination had a higher mortality rate than therapy with ceftazidime, imipenem/cilastatin, or amoxicillin/clavulanate (or ampicillin/sulbactam). The betalactam-betalactamase inhibitor therapy, however, seemed to have a higher failure rate.

Source: Tolaney P, Lutwick LI: Melioidosis. In: Lutwick LI, Lutwick SM (eds). Bioterror: the weaponization of infectious diseases. Totowa NJ: Humana Press, 2008 pp 145-58. - Mod.LL

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