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Journal of Bacteriology, July 2007, p. 4994-5001, Vol. 189, No. 14
0021-9193/07/$08.00+0     doi:10.1128/JB.00146-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Histidine Auxotrophy in Commensal and Disease-Causing Nontypeable Haemophilus influenzae{triangledown}

Patricia C. Juliao,1 Carl F. Marrs,1 Jingping Xie,1,2 and Janet R. Gilsdorf1,2*

Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, Michigan,1 Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, Michigan2

Received 29 January 2007/ Accepted 7 May 2007

Histidine biosynthesis is one of the best studied metabolic pathways in bacteria. Although this pathway is thought to be highly conserved within and between bacterial species, a previous study identified a genetic region within the histidine operon (his) of nontypeable strains of Haemophilus influenzae (NTHI) that was more prevalent among otitis media strains than among throat commensal NTHI strains. In the present study, we further characterized this region and showed that genes in the complete his operon (hisG, -D, -C, -NB, -H, -A, -F, and -IE) are >99% conserved among four fully sequenced NTHI strains, are present in the same location in these four genomes, and are situated in the same gene order. Using PCR and dot blot hybridization, we determined that the his operon was significantly more prevalent in otitis media NTHI strains (106/121; 87.7%) than in throat strains (74/137; 54%) (prevalence ratio, 1.62; P < 0.0001), suggesting a possible role in middle ear survival and/or acute otitis media. NTHI strains lacking the his operon showed attenuated growth in histidine-restricted media, confirming them as his-negative auxotrophs. Our results suggest that the ability to make histidine is an important factor in bacterial growth and survival in the middle ear, where nutrients such as histidine may be found in limited amounts. Those isolates lacking the histidine pathway were still able to survive well in the throat, which suggests that histidine is readily available in the throat environment.

* Corresponding author. Mailing address: Pediatric Infectious Disease, L2225 Women's Hospital, 1500 East Medical Center Dr., Ann Arbor, MI 48109-0244. Phone: (734) 763-2440. Fax: (734) 936-7635. E-mail: gilsdorf{at}umich.edu

{triangledown} Published ahead of print on 11 May 2007.

Journal of Bacteriology, July 2007, p. 4994-5001, Vol. 189, No. 14
0021-9193/07/$08.00+0     doi:10.1128/JB.00146-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • LaCross, N. C., Marrs, C. F., Patel, M., Sandstedt, S. A., Gilsdorf, J. R. (2008). High Genetic Diversity of Nontypeable Haemophilus influenzae Isolates from Two Children Attending a Day Care Center. J. Clin. Microbiol. 46: 3817-3821 [Abstract] [Full Text]  


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