Letters to the Editor
104
metabolic diseases. Several species, including B. cereus, B. subtilis and B. circulans have been described in such diverse conditions as pneumonia, panophthalmitis, meningitis, wound infections, endocarditis and septicaemia. 1 Reports of infections due to B. licheniformis are less well-recorded. It has caused ventriculitis after removal of an intraventricular meningioma, 4 septicaemia after arteriography 5 and bacteraemia in a pregnant woman with acute fibrinolysis. 6 It may also cause a diarrhoeal illness following ingestion of cooked meat dishes. 1 In addition, Mitchell and Barton have reported an association between bovine abortion and B. licheniformis infection of the placenta and fetus.7 This case emphasises the potential of B. licheniformis as a pathogen. In diagnostic laboratories, the significance of aerobic, spore-bearing bacilli producing 'lichenif o r m ' colonies characteristic of B. licheniformis and B. subtilis should be more carefully considered in the light of further isolates and in the clinical context before they are discarded as contaminants. (We thank Mr I. R. Whittle for permission to report this case.)
Department of Bacteriology, Western Infirmary, Glasgow GI I 6 N T
B. L. Jones
Central Microbiological Laboratories, Western General Hospital, Crewe Road, Edinburgh
M. F. Hanson
Department of Biological Sciences, Glasgow College, Glasgow, Scotland, U.K.
N. A. Logan
References I. Logan NA. Bacillus species of medical and veterinary importance. J Med Microbiol I988; 25: I57-I65. 2. Tuazon CU, Murray HW, Levy C, Solny MN, Curtin JA, Sheagren JN. Serious infections from Bacillus species. J Am Med Assoc I979 ; 24I : I I37-I 14o. 3. Weidermann BL. Non-anthrax Bacillus infections in children. Paediatr Infect Dis J I987; 6:218-219. 4- Young RF, Yoshimori RN, Murray DL, Chou PJ. Post-operative neurosurgical infections due to Bacillus species. Surg Neurol 1982; 18: 271-273. 5- Hardy A, Feger JM, Peimont Y, Bareiss P. Sepsis following arteriography : the role of an organism considered to be non-pathogenic: Bacillus licheniformis. J Med Strasbourg 1986; 17:18-19 . 6. Peloux Y, Charrel Taranger C, Gouin F. Nouvelle affection opportuniste fi Bacillus : un cas de bact6ri6mie fi Bacillus licheniformis. Path Biol (Paris) 1976; 24: 97-98. 7. Mitchell G, Barton MG. Bovine abortion associated with Bacillus licheniformis. Aust Vet J 1986 ; 63: 16o-161.
Recurrent pneumonia
d u e to r i f a m p i c i n - r e s i s t a n t Rhodococcus equi in a patient infected with HIV
Accepted for publication 4 April I99I Sir,
Rhodococcus equi previously known as Corynebacterium equi is an aerobic, Grampositive coccobacillus well-described as a pulmonary pathogen in farm animals,
Journal of Infection
Plates I and 2
Plate i. Colonies of Bacillus licheniformis on nutrient agar after 36 h incubation at 37 °C. Bar marker represents 5 mm.
Plate 2. Vegetative cells and sporangia of Bacillus licheniformis viewed by phase contrast microscopy. Bar marker represents 2 #in. B. L. JONES ET AL. (Facing p. lO4)
Letters to the Editor
IO5
especially in foals. 1 Since its first isolation from a h u m a n being, an i m m u n o c o m p r o m i s e d patient, in I967, 2 an increasing n u m b e r of cases of pneumonia and lung abscess due to R. equi has been reported, mainly due to the dissemination of A I D S . 1 Based on the results of in vivo experimental treatment of pneumonia in foals, z rifampicin combined with erythromycin given for several weeks has been shown to cure such infections without rifampicin-resistant strains of R. equi having been reported. 1 In h u m a n infections with R. equi, however, various antibiotic combinations have been tried with inconstant success, sometimes with the need for complementary resective surgery. TM Taking into account the intramacrophagic persistence of R. equi, antibiotics with high intramacrophagic concentrations such as rifampicin, macrolides, tetracyclines, fluoroquinolones, chloramphenicol and co-trimoxazole could theoritically be useful. We report here the first case of recurrent pneumonia due to a rifampicin-resistant strain of R. equi which was selected during treatment with rifampicin. A 39-year-old white m a n infected with H I V was admitted to hospital at the end of I989 for p n e u m o n i a associated with persistent fever. Chest X-rays showed infiltration of the lower lobe of the left lung. Cultures of bronchoalveolar lavage f u i d and a b r u s h sample yielded R. equi (strain I). Despite treatment with vancomycin, rifampicin and amikacin in combination for I week followed by I m o n t h ' s treatment with rifampicin ( I z o o m g / d a y ) combined with ciprofoxacin (750 m g / d a y ) , the lung abscess did not resolve. T h e patient therefore underwent left-sided partial lobectomy. After surgery, he was re-treated with rifampicin plus ciprofloxacin for 2 months until he was readmitted due to a recurrence of pneumonia. T h e strain of R. equi (strain 2) isolated concomitantly from blood, s p u t u m and bronchoalveolar lavage fluid was as sensitive to the antibiotics as R. equi strain I with the exception of rifampicin. F r o m October T99o, the patient was treated with a combination of erythromycin (I2oo m g / d a y ) plus doxycycline (zoo m g / d a y ) . H e was still in remission in M a r c h I 9 9 I . Strains of R. equi were identified according to the following criteria : G r a m - p o s i t i v e coccobacillus, catalase-positive, oxidase-negative, non-motile, non-spore-forming, urease-negative, nitrate, reduction-negative, gelatin hydrolysis-negative, orange-pink colour and round to ovoid shape of the mucoid colonies after 3 days of culture at room t e m p e r a t u r e on M u e l l e r - H i n t o n agar. T h e M I C s of antibiotics against R. equi strains I and z (IOG C F U / m l ) were measured in M u e l l e r - H i n t o n broth with doubling dilutions in 5 ml glass tubes. T h e y were determined after 24 h of incubation at 37 °C without shaking. M I C s for R. equi strain I are shown in T a b l e I. T h e s e M I C s were in general accordance with those summarized for R. equi by Prescott et al. ~ M I C s for R. equi strain 2 were identical to M I C s for R. equi strain I with the exception of that for rifampicin which was IOOO-fold higher (400 mg/1). After inoculating IO8 C F U R. equi (strain I) on rifampicin-containing agar (at concentrations four- and to-fold the M I C in three independent experiments) the mutation rate for rifampicin was I'5 × IO-7. M I C s of rifampicin for rifampicin-resistant mutants were 400 mg/1. W h e n ciprofloxacin, at concentrations four- or Io-fold the ciprofloxacin M I C , was added to rifampicin-containing medium, rifampicin-resistant mutants were not selected
(
104
metabolic diseases. Several species, including B. cereus, B. subtilis and B. circulans have been described in such diverse conditions as pneumonia, panophthalmitis, meningitis, wound infections, endocarditis and septicaemia. 1 Reports of infections due to B. licheniformis are less well-recorded. It has caused ventriculitis after removal of an intraventricular meningioma, 4 septicaemia after arteriography 5 and bacteraemia in a pregnant woman with acute fibrinolysis. 6 It may also cause a diarrhoeal illness following ingestion of cooked meat dishes. 1 In addition, Mitchell and Barton have reported an association between bovine abortion and B. licheniformis infection of the placenta and fetus.7 This case emphasises the potential of B. licheniformis as a pathogen. In diagnostic laboratories, the significance of aerobic, spore-bearing bacilli producing 'lichenif o r m ' colonies characteristic of B. licheniformis and B. subtilis should be more carefully considered in the light of further isolates and in the clinical context before they are discarded as contaminants. (We thank Mr I. R. Whittle for permission to report this case.)
Department of Bacteriology, Western Infirmary, Glasgow GI I 6 N T
B. L. Jones
Central Microbiological Laboratories, Western General Hospital, Crewe Road, Edinburgh
M. F. Hanson
Department of Biological Sciences, Glasgow College, Glasgow, Scotland, U.K.
N. A. Logan
References I. Logan NA. Bacillus species of medical and veterinary importance. J Med Microbiol I988; 25: I57-I65. 2. Tuazon CU, Murray HW, Levy C, Solny MN, Curtin JA, Sheagren JN. Serious infections from Bacillus species. J Am Med Assoc I979 ; 24I : I I37-I 14o. 3. Weidermann BL. Non-anthrax Bacillus infections in children. Paediatr Infect Dis J I987; 6:218-219. 4- Young RF, Yoshimori RN, Murray DL, Chou PJ. Post-operative neurosurgical infections due to Bacillus species. Surg Neurol 1982; 18: 271-273. 5- Hardy A, Feger JM, Peimont Y, Bareiss P. Sepsis following arteriography : the role of an organism considered to be non-pathogenic: Bacillus licheniformis. J Med Strasbourg 1986; 17:18-19 . 6. Peloux Y, Charrel Taranger C, Gouin F. Nouvelle affection opportuniste fi Bacillus : un cas de bact6ri6mie fi Bacillus licheniformis. Path Biol (Paris) 1976; 24: 97-98. 7. Mitchell G, Barton MG. Bovine abortion associated with Bacillus licheniformis. Aust Vet J 1986 ; 63: 16o-161.
Recurrent pneumonia
d u e to r i f a m p i c i n - r e s i s t a n t Rhodococcus equi in a patient infected with HIV
Accepted for publication 4 April I99I Sir,
Rhodococcus equi previously known as Corynebacterium equi is an aerobic, Grampositive coccobacillus well-described as a pulmonary pathogen in farm animals,
Journal of Infection
Plates I and 2
Plate i. Colonies of Bacillus licheniformis on nutrient agar after 36 h incubation at 37 °C. Bar marker represents 5 mm.
Plate 2. Vegetative cells and sporangia of Bacillus licheniformis viewed by phase contrast microscopy. Bar marker represents 2 #in. B. L. JONES ET AL. (Facing p. lO4)
Letters to the Editor
IO5
especially in foals. 1 Since its first isolation from a h u m a n being, an i m m u n o c o m p r o m i s e d patient, in I967, 2 an increasing n u m b e r of cases of pneumonia and lung abscess due to R. equi has been reported, mainly due to the dissemination of A I D S . 1 Based on the results of in vivo experimental treatment of pneumonia in foals, z rifampicin combined with erythromycin given for several weeks has been shown to cure such infections without rifampicin-resistant strains of R. equi having been reported. 1 In h u m a n infections with R. equi, however, various antibiotic combinations have been tried with inconstant success, sometimes with the need for complementary resective surgery. TM Taking into account the intramacrophagic persistence of R. equi, antibiotics with high intramacrophagic concentrations such as rifampicin, macrolides, tetracyclines, fluoroquinolones, chloramphenicol and co-trimoxazole could theoritically be useful. We report here the first case of recurrent pneumonia due to a rifampicin-resistant strain of R. equi which was selected during treatment with rifampicin. A 39-year-old white m a n infected with H I V was admitted to hospital at the end of I989 for p n e u m o n i a associated with persistent fever. Chest X-rays showed infiltration of the lower lobe of the left lung. Cultures of bronchoalveolar lavage f u i d and a b r u s h sample yielded R. equi (strain I). Despite treatment with vancomycin, rifampicin and amikacin in combination for I week followed by I m o n t h ' s treatment with rifampicin ( I z o o m g / d a y ) combined with ciprofoxacin (750 m g / d a y ) , the lung abscess did not resolve. T h e patient therefore underwent left-sided partial lobectomy. After surgery, he was re-treated with rifampicin plus ciprofloxacin for 2 months until he was readmitted due to a recurrence of pneumonia. T h e strain of R. equi (strain 2) isolated concomitantly from blood, s p u t u m and bronchoalveolar lavage fluid was as sensitive to the antibiotics as R. equi strain I with the exception of rifampicin. F r o m October T99o, the patient was treated with a combination of erythromycin (I2oo m g / d a y ) plus doxycycline (zoo m g / d a y ) . H e was still in remission in M a r c h I 9 9 I . Strains of R. equi were identified according to the following criteria : G r a m - p o s i t i v e coccobacillus, catalase-positive, oxidase-negative, non-motile, non-spore-forming, urease-negative, nitrate, reduction-negative, gelatin hydrolysis-negative, orange-pink colour and round to ovoid shape of the mucoid colonies after 3 days of culture at room t e m p e r a t u r e on M u e l l e r - H i n t o n agar. T h e M I C s of antibiotics against R. equi strains I and z (IOG C F U / m l ) were measured in M u e l l e r - H i n t o n broth with doubling dilutions in 5 ml glass tubes. T h e y were determined after 24 h of incubation at 37 °C without shaking. M I C s for R. equi strain I are shown in T a b l e I. T h e s e M I C s were in general accordance with those summarized for R. equi by Prescott et al. ~ M I C s for R. equi strain 2 were identical to M I C s for R. equi strain I with the exception of that for rifampicin which was IOOO-fold higher (400 mg/1). After inoculating IO8 C F U R. equi (strain I) on rifampicin-containing agar (at concentrations four- and to-fold the M I C in three independent experiments) the mutation rate for rifampicin was I'5 × IO-7. M I C s of rifampicin for rifampicin-resistant mutants were 400 mg/1. W h e n ciprofloxacin, at concentrations four- or Io-fold the ciprofloxacin M I C , was added to rifampicin-containing medium, rifampicin-resistant mutants were not selected
(
