Rhamnolipid production among clinical and skin isolates of healthy individuals of Acinetobacter species: The first report.

Sir,

Acinetobacter species are gram-negative, non-fermentative coccobacilli that has emerged as an important nosocomial pathogen incriminated in outbreaks of hospital-acquired infections in recent times.[1] Increasing reports of non-baumannii Acinetobacter spp.-associated infections are emerging nowadays. However, these bacteria are frequently refused as contaminants from environment, thus they are of little clinical importance.[2] Choi et al., (2006) stated that the mortality rate of other Acinetobacter spp. is not less than that of A. baumannii.[3] Rhamnolipids (RLs) are glycolipids comprising of L-rhamnose and 3-hydroxylalkanoic acid and is produced by several bacteria, most importantly Pseudomonas aeruginosa. It is an important virulent factor as it can inactivate tracheal cilia of mammalian cells and reduce the phagocytic activity of macrophages by altering the F actin network.[4] Virulence determinants of Acinetobacter spp. are ill-defined and, so far, previous literatures have not yielded any information regarding RLs-producing Acinetobacter spp. Hence, we planned to investigate the RL production in Acinetobacter spp. from clinical sources and from the skin of healthy individuals. We adopted Siegmund and Wagner plate method for the detection of RL of Acinetobacter spp.[5] A total of 108 clinical isolates of A. baumannii and 28 commensal isolates of Acinetobacter spp. (24 A. lwoffii and 4 A. junii) from the skin of healthy individuals were assessed in this study. Out of 108 A. baumannii isolates, 38 were from endotracheal aspirates, 20 from blood, 15 from pus, 10 from urine, 8 from sputum, 5 from bronchoalveolar lavage, 5 from wound swabs, 3 from oropharyngeal aspirates, 2 from nasopharyngeal aspirates, and one each from diabetic foot ulcer and central vein tip. The results showed that 12/108 (11.1%) clinical isolates of A. baumannii and 2/28 (7.1%) A. lwoffii from the skin of healthy individuals were positive for RL production. This is the first report of Acinetobacter spp. from clinical source and from the skin of healthy individuals producing RL. Although Acinetobacter spp. have become well-established nosocomial pathogens, not much is known about their virulence factor. This is the preliminary study conducted on Acinetobacter spp. It may be hypothesized that this RL production can also be one of the virulent factors of Acinetobacter spp. However, further studies need to be conducted on this virulent trait to elucidate the actual mechanism of Acinetobacter in relation with pathogenicity.