Journal List > Korean J Clin Microbiol > v.13(3) > 1038192

Korean J Clin Microbiol. 2010 Sep;13(3):128-131. Korean.
Published online September 30, 2010.
Copyright © 2010 The Korean Society of Clinical Microbiology
Aberrant Forms of Escherichia coli in Urine Culture
Youngeun Ma, Jang Ho Lee, Seung-Tae Lee, Chang-Seok Ki and Nam Yong Lee
Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

Correspondence: Nam Yong Lee, Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Korea. (Tel) 82-2-3410-2706, (Fax) 82-2-3410-2719, Email:
Received February 07, 2010; Revised July 13, 2010; Accepted August 20, 2010.


Bacterial morphology can be altered by various factors, including antibiotics. Unusually shaped, large, swollen organisms were observed in a urine culture obtained from a patient who had no history of antibiotic therapy. The organism was identified as Escherichia coli by the Vitek 2 system and by DNA sequencing of 16S rRNA and gyrB. The patient had no symptoms except fever, which subsided without medication. Microbiology laboratories should be aware of the potential appearance of such bacilli to avoid confusion with fungi and other naturally occurring filamentous organisms.

Keywords: Atypical bacterial forms; Escherichia coli; Urine


Fig. 1
(A) Small, dry and purple colonies in MacConkey agar plate, 2 days, (B) Comparison with E. coli ATCC 25922, in MacConkey agar plate, 2 days (left: E. coli ATCC 25922).
Click for larger image

Fig. 2
Unusual shaped large, swollen organisms resembling fungus spore were mixed with a few normal sized bacilli. Long bacilli, filamentous form and elongated bacilli with bulge were also seen (Gram stain, ×1,000).
Click for larger image

Fig. 3
The organism reverted to normal Gram-negative bacilli. But, some are still larger than normal E. coli (Gram stain, ×1,000).
Click for larger image

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