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| Year : 1981 | Volume
: 27
| Issue : 4 | Page : 218-21 |
Acinetobacter calcoaceticus-an opportunistic pathogen.
Pal RB, Kale VV
How to cite this article:
Pal R B, Kale V V. Acinetobacter calcoaceticus-an opportunistic pathogen. J Postgrad Med 1981;27:218 |
Acinetobacter calcoaceticus formerly known as Achromobacter anitratus. Bacterium anitratum, Herellea vaginicola, Moraxella glucodolytica var nonliquifaciens and Pseudomonas calcoacetica is ubiquitous in nature. These microorganisms are present as normal flora of the skin and throat of human beings along with other saprophytes. However, it is proved beyond doubt that these are opportunistic pathogens with a highly variable degree of virulence.[13], [21] These organisms appear to have little invasive power and depend upon a pre-existing break in the normal body defenses like a surgical wound to cause disease. They may also cause infections in debilitated patients or those administered immunosuppressive drugs.
Acinetobacter as a human pathogen has been reported sporadically since DeBord's original description of the group in 1939.[6] Thereafter, several reports appeared in the literature describing these organisms as a causative agent of meningitis,[8] fulminating septicaemia,[11] pulmonary[12] and ophthalmic infections,[28] chronic sinovitis,[15] skin diseases[7] and wound infections.[4] From India there are a few reports. Prakash et al[18] and Mukherji[17] reported isolation of this organism from different clinical materials. Prakash et al[19] described these organisms as causing septicaemia and Sujata et al[24] reported fatal infections caused by Acinetobacter calcoaceticus. Dalal et al[3] reported a case of postoperative urinary tract infection and also attempted the detection of humoral antibody against the organism. Madhavan and Jayakrishnan[16] found these organisms to be the causative agents of meningitis. The present report describes our experiences of clinical materials and cases from which strains of Acinetobacter calcoaceticus were isolated.
A total of 37 strains of Acinetobacter calcoaceticus were encountered from various clinical materials over a period of two years. The sources of clinical sampling were sputum (15 samples), urine (10 samples), blood and venous catheter tips (5 samples each) and pus (2 samples). These were collected in sterile containers and processed immediately. Sterile cotton swabs dipped in normal saline were used for collecting scanty exudate. Gram staining was done with each sample. The sample was then inoculated on blood agar and MacConkey agar. After 24 hours' incubation, the characteristic colonies were looked for and identified.[10] In the case of blood culture, 5 ml blood was collected and inoculated in 25 ml of Hartley's broth. After 24 hours' incubation, the solid media mentioned above were used for sub-culture and identification of organisms. In case of "No growth" from the first sub culture the process was repeated on alternate days for 10 days. For urine samples, a colony count was done. The characteristics of Acinetobacter calcoaceticus were as follows: On blood agar, there were large, opaque, mucoid, glistening and non-hemolytic colonies. On MacConkey's agar the colonies were pale and mucoid. The organisms were nonmotile, Gram negative cocci and coccobacilli. All the strains were catalase positive and oxidase negative. They did not cause any change in the triple sugar iron medium; citrate was utilised and tests for urease and indole were negative. Seller's medium showed an acid butt, alkaline slant and a yellow band due to production of acid from 10% dextrose. Gluconate was not utilised. Each strain was tested for its antibiotic sensitivity by disc diffusion method.[1]
The organisms caused urinary tract infection in 10 cases and in each case the colony count showed more than 105 organisms/ml of urine. Of these, 5 patients had been catheterised and this was the predisposing cause. Three cases were of chronic renal failure and two cases were of post-operative infections. In 2 of the cases of urinary tract infection Acinetobacter was isolated with Escherechia coli and in 3 cases Proteus mirabilis was the associated organism. The same organisms were isolated twice from 3 cases. With regards to the respiratory tract, Acinetobacter was isolated from 6 samples of sputum and 9 tracheal swabs. The tracheal swabs were collected from cases in whom a tracheostomy had been carried out on account of diverse reasons like tetanus or barbiturate poisoning. Other cases were of chronic obstructive pulmonary disease and respiratory tract infection. In one case the infection followed bronchoscopic removal of a foreign body in the right bronchus. The organism was isolated from the blood in 5 cases. Two of these septicaemias were following aortogram; one was from a premature baby, one from a case of anaemia and one following heart surgery. The samples of pus yielding Acinetobacter calcoaceticus included a guinea worm abscess and an abscess on the foot in a diabetic patient. [Table 1] describes the antibiotic sensitivity pattern of these 37' strains of Acinetobacter calcoaceticus. All the strains were sensitive to gentamycin. The next most effective drugs were streptomycin and chloramphenicol. All the strains were resistant to sulphadiazine.
Acinetobacter group of organisms are saprophytes. They have been isolated even from water and soil,[2] and normal skin and mucous membranes.[25], [27] At the same time these organisms have been reported to have caused serious and sometimes fatal infections.[9], [23], [26] Their pathogenicity has also been proved repeatedly in animals.[5] Most of the infections caused by Acinetobacter are associated wish iatrogenic entry or impaired host resistance.[13] In the present series most of the cases comprised of debilitated patients or individuals who had been interfered with to provide an entry for organisms into the tissues.
In five of the cases of urinary tract infections catheterisation might have been the source of infection. Two of the patients had chronic renal failure. This condition is well known as a predisposition to opportunistic pathogens. In incriminating the organism as a pathogen in the urine, care should be exercised in demonstrating the organism at levels of significant bacteriuria.[21]
The pathogenicity of Acinetobacter in the respiratory tract and as a cause of- septicaemia is well recognised.[11], [12], [14], [19], [22] A recent report on infective endocarditis caused by the organism has described occurrence of antibodies in the serum of the patients.[20]
Acinetobacter has often been disregarded as a potential pathogen. However, these organisms are assuming increasing importance perhaps because many of the pathogens of earlier days are being brought under control. The present study emphasises the changing pattern of opportunistic pathogens. Great attention should be paid to species previously regarded as non-pathogenic or simply as bacteriological curiosities for a possible role as opportunistic invader.
We are thankful to Dr. C. K. Deshpande, M.D., F.R.C. Path. (London), Dean, Seth G.S. Medical College and K.E.M. Hospital, Bombay-12 for permission to publish this paper.
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