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Rhodococcus and Mycobacterium Tuberculosis: Masquerade Or Mixed Infection

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Rhodococcus and Mycobacterium Tuberculosis: Masquerade Or Mixed Infection INT J TUBERC LUNG DIS 10(3):351–353 CASE STUDY © 2006 The Union Rhodococcus and Mycobacterium tuberculosis: masquerade or mixed infection N. F. Mistry,* Y. Dholakia,* D. T. B. D’Souza,* M. Taylor,† S. Hoffner,‡ T. J. Birdi* * Foundation for Medical Research, Mumbai, India; † Imperial College School of Science, Technology and Medicine, London, United Kingdom; ‡ Swedish Institute for Infectious Disease Control, Stockholm, Sweden SUMMARY Rhodocci have a morphology similar to that of Myco- emergence of resistance. We present here a sputum smear bacterium tuberculosis (TB), and are indistinguishable AFB-positive case who, although clinically cured, re- from normal diphtheroid flora. Symptoms include fever, mains unresolved despite a series of technological inves- productive/non-productive cough and pleuritic chest tigations as to the cause of infection being purely rhodo- pain. Rhodococcal infections, being resistant to routine cocci or mixed infection with M. tuberculosis. anti-tuberculosis medications, may be misdiagnosed as KEY WORDS: Mycobacterium tuberculosis; Rhodococ- drug-resistant TB, thus prompting treatment for TB cus equi; rpo␤ mutations; mixed infections; IS1081; Oxy R with rifampicin-containing regimens that promote the ALTHOUGH they are resistant to routine anti- attacks and the smear results, anti-tuberculosis treat- tuberculosis treatment, rhodococci are morphologi- ment (HRZE*) was commenced on 18 May 2002 cally similar to Mycobacterium tuberculosis (TB), along with haematinics and ayurvedic immune mod- and are indistinguishable from normal diphtheroid ulators. The latter were temporarily withheld follow- respiratory flora.1,2 Symptoms include fever, productive/ ing a bout of acute bronchospasm. The paroxysmal non-productive cough and pleuritic chest pain. Rhodo- cough episodes persisted up to 9 weeks with fluctua- Q: “Although the” What word is missing? Q: “Although the” What word coccal infections, being resistant to routine anti- tions in respiratory symptoms. Drowsiness and fa- tuberculosis medications, may be misdiagnosed as tigue attributed to isoniazid developed over time. drug-resistant TB, thus prompting treatment for TB Weekly sputum samples were processed using the with regimens that include rifampicin (RMP), which modified Petroff’s method. The AFB count reduced promote the emergence of resistance.3 marginally until the third week after initiation of anti- We present a sputum smear acid-fast bacilli (AFB) tuberculosis treatment. The AFB, although rod shaped, positive case who, although cured, has remained un- appeared thicker, shorter and less curved in compari- resolved as to whether the cause of infection is purely son to M. tuberculosis, and the presence of intracel- rhodococci or mixed infection with M. tuberculosis. lular acid-fast cocci was also noted. Thereafter, the count peaked at 2 months at 246 AFB/100 fields. All routine mycobacterial growth media were culture- CASE REPORT negative. An 80-year-old male (weight 75 kg), resident of Mum- DNA analysis of the first sputum sample, conducted bai and Pune, India, presented with insidious onset of at Swedish Bacteriological Laboratory, Stockholm, dry cough unresponsive to extensive supportive treat- using the Inno Lipa Kit (Innogenetics, Ghent, Belgium), ment in May 2002. With no other constitutional symp- identified the organisms as M. tuberculosis complex, toms, clinical examination revealed only mild oropha- positive for the rpo␤ region, with the absence of band ryngeal congestion. S5 and the presence of a R5 band indicating RMP re- Routine investigations showed mild anaemia, re- sistance. The same sample tested blind at Imperial duced platelet count and lowered serum immunoglo- College, London, was also positive for rpo␤ and bulin G with normal chest X-ray. However, sputum IS1081, an insertion sequence present in the M. tuber- smears stained by Ziehl-Neelsen carbol fuchsin showed culosis complex. Oxy R sequencing also showed the 50 AFB/100 fields. These were confirmed by another reference laboratory. Given the intractable cough leading to vasovagal *H ϭ isoniazid; R ϭ rifampicin; Z ϭ pyrazinamide; E ϭ ethambutol. Correspondence to: Nerges F Mistry, Foundation for Medical Research, 84-A, R G Thadani Marg, Worli Sea Face, Worli, Mumbai 400 018, India. Tel: (ϩ91) 22 2493 4989/2876/8601. Fax: (ϩ91) 22 2493 2876. e-mail: [email protected] Article submitted 6 April 2005. Final version accepted 20 September 2005. 352 The International Journal of Tuberculosis and Lung Disease presence of nucleotide G at position 285 specific to M. samples collected after August 2002 were negative for tuberculosis. Rpo␤ gene sequencing showed the pres- AFB by the auromine O fluorescent method. Evidence ence of two strains, of which the main one was M. of a rhodococcal life cycle was noted when the coc- tuberculosis. On the basis of the above evidence, insti- coid colonies were inoculated into C57BL/6 mouse tution of second-line anti-tuberculosis treatment was peritoneal macrophages. Forty-eight hours post infec- considered. tion all intracellular organisms were noted to be AFB. A thorough clinical, immunological and radiologi- Rhodococci respond well to tetracycline, macrolides cal (including chest high resolution computed tomog- and cotrimoxazole, but rapidly develop resistance to raphy [HRCT]) examination was performed to facili- routine anti-tuberculosis treatment.5 A prolonged se- tate a clinical decision 3 months post anti-tuberculosis quential course of antibiotics (Figure) was prescribed treatment. No abnormality was detected except for between August and October 2002. Symptoms gradu- chronic sinusitis of the left maxillary sinus. Fiberoptic ally regressed, with normal lung function at 7 months bronchoscopy revealed a normal tracheobronchial post onset. To date there is no recurrence of symptoms. tree. Processed bronchoalveolar aspirate was AFB- positive. The untreated sample was incubated at 37ЊC in DISCUSSION chocolate blood agar, Saboraud’s agar and Löwenstein- Jensen as well as in Dubos broth and Mycobacteria Rhodococci have recently emerged as opportunistic Growth Indicator Tubes (Becton Dickinson, Sparks, pathogens and are sparsely reported.6 Infections in MD, USA). While there was no growth of acid-fast both immunosuppressed and immunocompetent hosts forms in routine mycobacterial growth media, colonies have been reported.7–9 obtained within 48 h on chocolate blood and Sabo- The organism can be mistaken for M. tuberculosis on rauds’ agar showed concurrent presence of acid-fast routine AFB stain, but can be differentiated by its colony cocci and short rods. On prolonged culture, however, characteristics. Rhodococci can also occur as mixed in- the colonies (2–4 mm in diameter, white, convex, fections with M. tuberculosis, which might explain the smooth and opaque) showed predominantly coccoid early detection of M. tuberculosis genes. Mycobacteria forms. DNA analysis showed strong IS1081 bands and rhodococci are also known to have common anti- and were again positive for the rpo␤ region. Sequence gens,10,11 and possibly identical or highly similar ge- analysis of this DNA using BLAST searches was pos- nomic sequences that lead to confounding results. itive for Rhodococcus equi-like organisms. In an endemic area, the patient had probably been Anti-tuberculosis treatment was discontinued at pre-exposed to M. tuberculosis infection. With evi- week 10 because of a stable clinical condition, lack of dence of a multidrug-resistant M. tuberculosis strain radiological and bronchoscopic evidence of pulmo- on the InnoLipa strip, it is doubtful that 3 months of nary TB and persistent side effects. anti-tuberculosis treatment would have resolved the Two properties subsequently tested also con- infection even in a relatively well-nourished patient. formed to those of the rhodococcus genus.4 Sputum Although test positivity could have originated from Figure Correlation between treatment, AFB counts and clinical status. Antibiotics given: 1) penicillin 15 days; 2) TMP ϩ SMX ϩ CLM 21 days; and 3) CPX ϩ CLM 5 days. AFB ϭ acid-fast bacilli; H ϭ isoniazid; R ϭ rifampicin; Z ϭ pyrazinamide; E ϭ ethambutol; CT ϭ computed tomography; TMP ϭ trimethoprim; SMX ϭ sulfamethoxazole; CLM ϭ clarithromycin; CPX ϭ ciprofloxacin. Rhodococcus and M. tuberculosis 353 DNA of bystander non-viable M. tuberculosis, the ini- References tial findings with sputum DNA suggest a mixed infec- 1 Giacometti A, Cirioni O, Ancarani F, Del Prete MS, Fortuna tion of M. tuberculosis and R. equi. However, the lack M, Scalise G. In vitro activities of polycationic peptides alone of response to anti-tuberculosis treatment, the deferves- and in combination with clinically used antimicrobial agents ence of clinical symptoms on prolonged non-anti-tuber- against Rhodococcus equi. Antimicrob Agents Chemother culosis chemotherapy and the absence of symptoms on 1999; 43: 2093–2096. follow-up is supportive of pure R. equi infection. Ad- 2 Takai S, Sasaki Y, Ikeda T, Uchida Y, Tsubaki S, Sekizaki T. Vir- ulence of Rhodococcus equi isolates from patients with and vanced age, mild immunodeficiency, chronic sinusitis without AIDS. J Clin Microbiol 1994; 32: 457–460. (constituting a persistent source of rhodococcus) along 3 Gray K J, French N, Lugada E, Watera C, C F. Rhodococcus with stress could have served as predisposing factors. equi and HIV infection in Uganda. J Infect 2000; 41: 227–231. The gene analysis from the broncholavage sample 4 Cornish N, Washington J A. Rhodococcus equi infections: clin- 3.5 months post anti-tuberculosis
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