Indian Journal of Medical Microbiology Medknow Publications on behalf of Indian Association of Medical Microbiology ISSN: 0255-0857 EISSN: 1998-3646 Vol. 28, Num. 4, 2010, pp. 387-389

Indian Journal of Medical Microbiology, Vol. 28, No. 4, October-December, 2010, pp. 387-389

Case Report

Isolation of Streptobacillus moniliformis from the blood of a child with acute lymphoblastic leukaemia

AS De¹, SM Baveja¹, PM Salunke¹, MV Manglani²

¹ Department of Microbiology, L.T.M. Medical College, Sion - 400 022, Mumbai, India
² Department of Paediatrics, L.T.M. Medical College, Sion - 400 022, Mumbai, India
Correspondence Address:
A S De, Department of Microbiology, L.T.M. Medical College, Sion - 400 022, Mumbai, India
dr_anuradhade@yahoo.com

Date of Submission: 22-Feb-2010
Date of Acceptance: 14-Jul-2010

Code Number: mb10113

PMID: 20966577
DOI: 10.4103/0255-0857.71826

Abstract

Keywords: Acute lymphoblastic leukaemia, Streptobacillus moniliformis, septcaemia

Introduction

Streptobacillus moniliformis (S. moniliformis) and Spirillum minus cause rat-bite fever in man, either through rat bite, or from food or water contaminated with rat excreta. Rat-bite fever is a systemic illness classically characterized by relapsing fever, rigors, rash on extremities and migratory polyarthralgias. ^[1],[2] If left untreated, it causes a mortality rate of 13%. ^[1] When infection occurs in absence of documented animal bite, but through contaminated milk, it is called Haverhill fever. ^[1] Streptobacillus moniliformis can also cause fulminant endocarditis, refractory pericardial effusion, pleural effusion, pneumonitis, overwhelming septicaemia, brain abscess, pancreatitis and focal abscess.^[1],[2],[3] Frank arthritis caused by this bacteria persists for years, even after resolution or treatment of the infection.^[2]

We present here an unusual case of S. moniliformis infection in a male child suffering from acute lymphoblastic leukaemia.

Case Report

A six-year-old male child residing at Mumbai was admitted on 24 February 2009 for his repeat induction chemotherapy. He was a known case of acute lymphoblastic leukaemia with Common Acute Lymphoblastic Leukaemia Antigen (CALLA)-positive, diagnosed in our hospital in October 2008. His first and second induction cycle of chemotherapy was in October-November 2008 and December 2008−January 2009, respectively, with interim maintenance cycle in January−February 2009. He developed loose motions along with fever and vomiting in March 2009 during his repeat induction chemotherapy. There was no history of joint pain. On examination, purpuric spots were present mainly in the lower extremities [Figure - 1], but no pallor was seen. No abnormality was detected in respiratory, cardiovascular and central nervous systems. Per-abdominal examination was also normal without any hepatosplenomegaly. Stool culture was sent to the laboratory, but it did not grow any enteropathogenic bacteria. The child was started on IV cefotaxime and amikacin, which was given for ten days and metronidazole for five days. Diarrhoea subsided within two days.

Simultaneously with the stool culture, a blood culture was also sent to the laboratory. We used the conventional method of blood culture containing trypticase soy broth without sodium polyanethol sulphonate (SPS), which was incubated at 37°C. On the next day, Gram stain from the broth showed gram-negative filamentous bacilli with bulbous or sausage-shaped (moniliform) swellings appearing along the filament, resembling a string of beads [Figure - 2]. A subculture was done on the second day on blood agar (BA) plate, which was placed in the candle jar and also on MacConkey agar (MA) plate and both the plates were incubated at 37°C for 48 h. There was no growth on MA. On BA, 1−2 mm diameter of discrete greyish yellow colonies were seen after 48 hours of incubation. Secondary smear from BA also confirmed the same morphology. The bacteria were non-motile and non-capsulated. It was catalase- and oxidase-negative, did not produce indole and did not reduce nitrates to nitrites. It fermented glucose and salicin with acid production only and also hydrolysed esculin. None of the other sugars were fermented. It was susceptible to penicillin and ampicillin. Based on the biochemical reactions, it was identified as S. moniliformis, which causes rat-bite fever. ^[2] There was no history of rat bite in this child, but his family members confirmed presence of rats in the house. The bacteria was susceptible to erythromycin, amikacin, amoxicillin-clavulanic acid, cefotaxime, cefuroxime, tetracycline, clindamycin, imipenem and vancomycin, but resistant to nalidixic acid, norfloxacin, ciprofloxacin and trimethoprim-sulphamethoxazole by Kirby-Bauer Disc Diffusion Method on Mueller Hinton agar according to Clinical Laboratory Standards Institute (CLSI) guidelines. ^[4]

After receiving our report, he was continued with IV cefotaxime twice a day for further five days. Fever subsided. His induction chemotherapy went on up to end of March, after which his consolidation cycle started. In first week of April, a repeat blood culture did not show growth of any organism. His complete blood count on three occasions are given in the [Table - 1]. Finally he was discharged in mid-April 2009. His condition was stable on discharge.

Discussion

There is absence of documented animal bite in the present case. But as rats were present in the house, infection through contaminated drinks may be a possibility in our case. Even simple contact with pet rats can cause rat-bite fever. ^[5] Cases have also been reported with no history of rodent bites or direct exposure to rodents. ^[6] Diagnosis definitely becomes problematic in such a situation.

Initially the child had diarrhoea, but no enteropathogen could be isolated from stool culture. Diarrhoea is often seen during chemotherapy, as the normal colonic flora changes with reduction of the anaerobic bacteria of the colon. ^[7]

In PubMed search with "S. moniliformis in leukaemia", no item was found. This may be the first case report from India in a leukaemic patient. First report of S. moniliformis endocarditis from India was in 2006. ^[8]

Its non-specific initial presentation, broad differential diagnosis, combined with difficulties in culturing the organism, produces a significant risk of severe invasive disease, if left untreated. But in our case, the bacteria grew on BA after 48 hours of incubation.

For proven or highly suspected cases of rat-bite fever, the drug of choice is Penicillin G. It is usually given in a dose of 400 000−600 000 IU per day IV for adults for at least seven days and 20 000−50 000 IU/kg of body weight per day for children for 5−7 days. ^[1] Cephalosporins have also been used successfully. ^[1] Our patient responded to IV cefotaxime for 15 days and IV amikacin for 10 days.

Streptobacillus moniliformis infection in our case may be another infection totally unrelated with leukaemia, probably due to food or water contamination with rat excreta. But it can also happen as a result of the depressed defense mechanism in the child due to leukaemia and ongoing chemotherapy. Streptobacillus moniliformis endocarditis has already been reported in an HIV-positive patient. ^[9] Whether this bacteria can cause opportunistic infection in immunocompromised patients, including patients suffering from leukaemia, need to be evaluated further. Therefore, a high index of suspicion is required, coupled with laboratory preparedness to isolate such unusual organisms like S. moniliformis.

References

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