Respiratory tract colonization with GNB Part 1

18 May

 It’s been a crazy last few months, we’ve been busy with many side projects with ASP.  Dan and I have been adding to our list of blog topics. I’m looking forward to Dan’s planned post on ‘why fluoroquinolones are evil.’

This is a 2 part post. The topic of this post comes from two recent interactions we had with our colleagues.  Two cases (two different hospitals) of suspected ICU HAP/VAP with gut/poo bacteria (Klebs + E coli).  Both patients grew these bugs from sputum cultures and the comment was made that these must be pneumonias because you can’t be colonized with poo in your respiratory tract.

A paper by Johanson et. al published in the New England Journal of Medicine in 1969[1] provides a great starting point to this discussion.  The group from Texas selected 5 groups of adults: non-hospitalized normal subjects (members of Dallas fire dept); hospital associated normal subjects (hospital staff); physically normal hospitalized patients (psych ward); moderately ill hospitalized patients (ortho); and near death (moribund) patients (critically ill medical).  They obtained oropharyngeal cultures from each of the groups.  They found that 57% of moribund patients were colonized with gram negative bacilli (GNB) and 16% of moderately ill patients (orthopedic) were colonized.  2% from the non-hospitalized normal subjects were also colonized.  This was a small study, and has its flaws.  There are other papers that explore colonization with GNBs.  (2,3,4)   It is possible to have poo bacteria in the mouth/oropharynx. 

In normal hosts >90% of GNB in the oropharynx is cleared by effective salivary flow and swallowing.  (5) Our sicker and elderly patients have impairment of these clearance mechanisms thus the increased risk of colonization by pathogenic GNBs. 

But how do GNBs get into the mouth/oropharynx to begin with? The answer is pretty wild.

[1]Johanson, W. G., Pierce, A. K., & Sanford, J. P. (1969). Changing pharyngeal bacterial flora of hospitalized patients. Emergence of gram-negative bacilli. The New England Journal of Medicine, 281(21), 1137-1140.

 [2] Garrouste-Orgeas, M., Chevret, S., Arlet, G., Marie, O., Rouveau, M., Popoff, N., & Schlemmer, B. (1997). Oropharyngeal or gastric colonization and nosocomial pneumonia in adult intensive care unit patients. A prospective study based on genomic DNA analysis. American Journal of Respiratory and Critical Care Medicine, 156(5), 1647-1655. Retrieved from

[3] Heyland, D., & Mandell, L. A. (1992). Gastric colonization by gram-negative bacilli and nosocomial pneumonia in the intensive care unit patient. Evidence for causation. Chest, 101(1), 187-193.

[4] Mackowiak, P. A., Martin, R. M., Jones, S. R., & Smith, J. W. (1978). Pharyngeal colonization by gram-negative bacilli in aspiration-prone persons. Archives of Internal Medicine, 138(8), 1224-1227.

[5] Palmer, L. B., Albulak, K., Fields, S., Filkin, A. M., Simon, S., & Smaldone, G. C. (2001). Oral clearance and pathogenic oropharyngeal colonization in the elderly. American Journal of Respiratory and Critical Care Medicine, 164(3), 464-468. Retrieved from

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: