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Infective endocarditis due to Acinetobacter calcoaceticus.
Of the several causes of infective endocarditis an important predisposing cause is a pre-existing heart disease. In the pre-antibiotic era, Streptococci accounted for 70 to 80% of cases. However, after the advent of antibiotics there appears to be a change in the etiological flora. Presently, other organisms that were considered as commensals like some saprophytic gram negative bacilli,[3] Candida albicans's have become responsible for this septicaemic condition. Here are described 4 cases of sub acute bacterial endocarditis from whose blood Acinetobacter calcoaceticus was isolated and agglutinating antibodies to these demonstrated. To our knowledge, there have been very few cases of endocarditis due to Acinetobacter reported so far in the world literature,[5], [16], [22], [27] and none so far from India.
Blood cultures were carried out from cases clinically diagnosed as sub acute bacterial endocarditis admitted to the Kasturba Medical College Hospital, Manipal, during January 1973 to December, 1978. Eight hourly samples of blood were collected round the clock from patients on two consecutive days i.e. a total of 6 samples, were cultured. Extra care was exercised to prepare the venipuneture area.[1] Prepuncture swabs taken from the prepared area were also cultured. Dry sterile syringes were used to draw blood. Five ml of blood were directly inoculated through the rubber diaphragm, into 50 ml of serum glucose and thioglycollate broths. In cases 1 and 2, bone marrow aspiration material was also cultured in the same media. All antibiotic therapy was withheld for 72 hours before blood was drawn for culture. Throat swabs and sputum samples were also obtained and cultured. In case No. 2, because of the chronic otitis media, ear swabs were also cultured. Subcultures from glucose serum broth and thioglycollate broth were done at 24 hour intervals on blood agar and were incubated aerobically and anaerobically respectively. These were incubated at 37°C and aerobic cultures observed every day and anaerobic, every third day for 6 days before discarding as negative. The isolates were identified as described by Cowan[6] and Buchanan and Gibbons;[4] all the isolates were put up for agglutination with the respective patient's serum. Their antibiotic sensitivity was determined by the disc diffusion method as described by Cruickshank.[7]
Case 1: A case of ventricular septal defect: A 3 year 8 months old girl, anaemic (Hb 9.5 grams%) and with delayed mile stones of development was admitted to K.M.C. Hospital, Manipal. She had a history of repeated attacks of breathlessness, ever since she was 6 months old. X-rays revealed an enlarged heart with prominent pulmonary conus and a straight left border. Patch opacities were seen in the right lower and the left upper zones. There was a deformity of the chest. Except for the total leucocyte count of 13,600 per cu.mm the rest of the findings were of no clinical value. The case was diagnosed as a case of ventricular septal defect and was operated for the same. Case 2: A case of `Tetrology of Fallot' with chronic respiratory infection and suppurative otitis media: An eleven year old girl with 8 year history of breathlessness, proceeding on to dysponea and cyanosis on severe exertion plus a chronic left ear discharge of five years' standing. At the time of admission she was cyanotic with clubbed fingers. A precordial bulge was also present. Cardio vascular system examination revealed a blood pressure of 110/80 mm of Hg and a pulse rate of 80 per minute; apex, beat was in the 4th intercostal space in the midclavicular line with an observable mild parasternal heave and an auscultatable ejection murmur over mitral, pulmonary and Erbs areas E.C.G. was interpreted as right ventricular hypertrophy. She had a leucocyte count of 14,700 per cu mm with 67% polymorphs. Other findings were unequivocal. Case 3: A case of patent ductus arteriosus, aortic stenosis and aortic incompetance: This 22 year old unmarried female diagnosed as a case of "patent ductus arteriosus" when she was 12, and as a case of "rheumatic fever" when she was 17, has been in and out of several hospitals. She was admitted to this hospital for intermittant fever of about a month's duration, ushered in by a chill and relieved by sweating. There was productive cough with a non-offensive whitish sputum. Knee joints were painful but not swollen. She was anaemic (Hb. 7.5 grams%) with a total leucocyte count of 13,500 with 86% polymorphs. ASLO titre was within normal limits. Conclusion drawn from her ECG was sinus bradycardia with left ventricular hypertrophy. Case 4: A case of acute rheumatic carditis: An 8 year old boy was admitted for complaints of progressive breathlessness of 3 days' duration, attended with unproductive cough. He gave a history of joint pain of 20 days' duration pre-admission. He had a high respiratory rate (64/min.) with increased resonance on percussion and equal air entry on either side. X-rays were suggestive of pulmonary oedema. His other salient findings were tachycardia, ESR 10/mm fall 1st hour (Westergren), hemoglobin of 12 grams%, total leucocyte count of 15,800 per cu mm, with polymorphs 77%, lymphocytes 27%, eosinophil 1%, ASLO titre was 833 Todd units and no cardiomegaly. Heart sounds were muffled in all areas; a long systolic murmur (grade 4/6) was heard best over the apex area and conducted to the axilla. A soft mid-diastolic murmur was also heard over the apex. ECG reading suggested sinus tachycardia. Liver was enlarged 5 cm below the costal margin and tender. Other investigations were within normal limits.
All pre-puncture swabs were sterile. The results of isolation of A. calcoaceticus from blood as well as from other sites are given in [Table 1]. The isolates from Case No. 3 differed in certain characters from others isolates i.e. from cases 1, 2 and 4 and are shown in [Table 2]. The anti microbial drug sensitivity pattern is given in [Table 3]. Sera from all four patients gave a positive agglutination titre of 1:125 or more with the respective corresponding isolates [Table 4].
The ubiquitous organisms Acinetbacter calcoaceticus and Acinetobacter lwoffii are considered as saprophytic, usually found in water and soil.[2] These organisms can also exist as commensals and have been isolated from skin and mucous membranes.[29], [39] Amongst all gram negative bacilli seen in normal pharyngeal flora the Acinetobacter species is found next only to other members of enterobacteriaeceae.[25] It is well documented that saprophytic bacteria may become opportunistic pathogens in debilitated patients. Some of the predisposing factors are congenital heart diseases, malignancies, premature birth, burn wound, or the indiscriminate use of antibiotics and immunosuppressive drugs. The role of Acinetobacter as an opportunistic pathogen causing variety of clinical conditions such as meningitis,[10] fulminating septicaemia,[13] pulmonary [14] and ophthahnic[31] infections, chronic synovitis,[17] skin diseases,[9] wound infections,[8] post burn sepsis[l5] and urinary tract infections[11] have been reported in the world literature. In India, various workers have reported the isolation of Acinetobacter from conditions other than endocarditis[21], [23], [24], [26], [28] All the cases described here were suffering from congenital heart diseases who developed subacute bacterial endocarditis. The increasing incidence of infections due to gram negative bacilli is evident in cases of post-surgical bacterial endocarditis.[20] In cases of endocarditis occurring after cardiac surgery, the combination of lowered host resistance and infection with resistant bacterial species results in a mortality from 20 to 90%. In case No.1 described above, the patient developed S.B.E. 15 days after the surgical correction for a ventricular septal defect. A. calcoaceticus was isolated from two blood samples as well as from a throat swab and sputum and bone marrow of this patient. In the second case, A. calcoaceticus was isolated from blood, sputum, bone marrow as well as from ear discharges. The endocarditis in this case was probably due to septicaemia preceded by pulmonary infections and otitis media. The third patient was diagnosed as a case of S.B.E. since she was 17 years of age. From an early age she had dental caries and had undergone surgical treatment for the same. A. calcoaceticus was isolated from her blood and sputum samples. It is documented that 25 to 50% of endocarditis patients had one or more teeth extracted some two months before the onset of valvular ailment.[18] Case No. 4 of the present series was a case of acute rheumatic carditis with respiratory infection plus pulmonary oedema. A. calcoaceticus was isolated from his blood and sputum. All the strains isolated in this series were resistant to Penicillin and Sulphadiazine and showed a variable antibiotic sensitivity pattern. The isolate from case No. 3 differed from the others in showing a high degree of resistance to the following-Ampicillin, Chloramphenicol, Erythromycin, Gentamycin, Kanamycin, and Streptomycin. It was however sensitive to Trimethoprim/Sulfamethoxazole. It also showed a variation in its biochemical activities from other isolates, as mentioned in the results. According to Cowan,[6] these variations in the biochemical activities are possible and existence of such variant strains range between 16 to 84% of the isolations of A. calcoaceticus. Agglutination tests with patient's serum and A. calcoaceticus were positive in diagnostic titre of 1:125 in all the cases. Serum samples from other pyrexial cases were also put up as controls and no agglutination was seen in any one of them, thus showing that infection with A. calcoaceticus had occurred. A. calcoaceticus can occur as a laboratory contaminant. Faris et al[12] reported its occurrence as a contaminant in the blood culture bottle when Penicillinase was added to it after sterilisation. In an investigation on the sterility of the operation theatres, we recovered A. calcoaceticus from soap solutions used in the operation theatres for scrubbing. Hence one has to be very careful to incriminate this organism as an aetiological agent. However, we are of the opinion that isolations of Acinetobacter from cases of endocarditis should not be ignored as a contaminant. The criteria for diagnosis of endocarditis due to this organism depended on repeated isolations from blood. bone marrow, demonstrations of antibodies in patient's serum and a clinicobacteriological correlation. A. calcoaceticus has little invasive power. However, it is suggested that like Streptococcus viridans, these usually commensal organisms found associated with human tissues, can also be transported by way of the blood stream due to some trauma and cause endocarditis-particularly in those debilitated patients with congenital heart diseases.
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