The rising problem of Acinetocbacter baumannii in the healthcare environment and the growing research into novel treatment solutions to combat it

Acinetobacter baumannii is an opportunistic pathogen which has grown to international attention over the last 15 years due to its rapid infiltration of the healthcare environment becoming a common nosocomial infective agent. Whilst also gaining fame through the infection of soldiers wounds returning from the Iraq and Afghanistan conflicts, providing it the nickname ‘iraqibacter’. It is now a highly multi drug resistant pathogen which has had reports of bacteria resistant to all current antibiotics. This review will look at the virulence factors behind its success and the struggling treatments currently being used and investigating where the scientific community are taking the field of research for new and effective treatments against this pathogen. Introduction Acinetobacter baumannnii is a gram negative bacillus that is a pleomorphic, nonmotile, nonfermenting, oppotunistic pathogen that has risen to international significance in the last 15 years. [1-4] It is a major cause of nonsocomial infections and has a particularly high incidence among patients who are immunocompromised. [4,5] It frequently causes outbreaks in hospitals worldwide and is reportedly responsible for over 7,000 hospitalacquired infections and 500 deaths in the United States alone yearly. [4,6-11] Generally A baumannii infections manifest in the form of respiratory tract infections, urinary tract infections, meningitis, endocarditis, wound infection, bacteraemia and pneumonia. [4,10-15]) It has recently been reported however, of cases of necrotising faasciitis in severe cases of wound infection. [16] Normally associated with aquatic environments, it has gained notoriety recently due to its prevalence in infections of injured service personnel from the recent desert conflicts of Iraq and Afghanistan, gaining it the nickname of ‘iraqibacter’ . [9,2] Due to its prolific biofilm producing virulence factors it causes major problems in healthcare settings where it can adhere and remain alive for days on surfaces such a polystyrene, glass and metal. [17-23] Confounding this is its many other virulence factors which help the bacteria avoid or negate the immune system of the host, and or induce apoptosis or necrosis, increasing the significance of the infection. [24] Antibiotic resistance ,especially multi drug and pan resistance, has furthered the international concern around the A baumannii as traditional treatment options become increasingly ineffective. In recent years the marked rise if multidrug resistant strains of the bacterium have lead to its designation as a red alert human pathogen [6] and the Centres for disease control and prevention (CDC) classifying a baumannii as a serious threat to hospitals. [11] With antibiotic resistance being identified as one of the three most important problems facing human health. [25] However the international attention provided to a baumannii has lead to research and novel treatment concepts that hope to bring about an effective solution to the problem from novel vaccine concepts [3] to the use of chelating agents to disrupt biofilm formation and bacterial colonisation of abiotic surfaces. [1]. In this review paper we will discuss the virulence factors that make this opportunistic pathogen so successful and dangerous, specifically antibiotic resistance and biofilm formation and discuss some of the treatment options available to fight it. Virulence Mechanisms A.baumannii is a notoriously effective organism at surviving in both hostile environments and surfaces, as well as avoiding host defences/ immune system. This ability is down to a.baumannii’s many virulence factors. Biofilm formation in A. baumannii is likely to be one of the most important virulence factors in its ability to survive on abiotic and biotic surfaces for substantial periods of time. [26] This will aid in its ability and success in nonsarcomial transmission and host infection. Biofilm formation is highly prevalent in the A.baumannii species with some studies suggesting it is three times more likely to form a biofilm than any other member of the Acinetobacter genus. A biofilm is generally a collection or colony of bacteria embedded in a self produced extracellular matrix made of polysaccharides and proteins. [26] Biofilms allow increased resistance to antibiotics, phagocytosis and both the