Interactions
Streptococcus and Chemical Warfare
Our body is inhabited by trillions of bacteria, some of which
call the upper respiratory system home. Among the most common are
Streptococcus pneumoniae, Moraxella cattarrhalis, Haemophilus
influenzae,
Neisseria meningitis, and
Staphylococcus aureus
(Bogaert, 2004). S. pneumoniae has various relationships with some of
these bacteria. Seeing as the upper respiratory tract
provides an environment with limited resources, bacteria are likely
to have to compete with one another. One of the ways S. pneumoniae
dominates the upper respiratory system is by producing hydrogen
peroxide (H2O2) through its metabolic cycle. The production of H2O2
has been shown to inhibit the growth of Hameophilus influenzae,
Moraxella catarrhalis, and Neisseria meningitis in vitro (Pericone,
2000). In addition, Staphylococcus aureus was also shown to be
inhibited by the production of H2O2y S. pneumoniae (Regev-Yochay,
2006).
Within an organism, however, S. pneumoniae displays an
interesting relationship with Hameophilus influenzae. As stated
above, S. pneumoniae uses it’s hydrogen peroxide to kill off other
organisms it is competing against. When these two species compete,
Hameophilus influenzae will typically use an immune cell known as a
neutrophil to kill off the competing S. pneumoniae. This recruitment
of the bodies neutrophils leaves the H. influenzae to grow with less
competition. (Lysenko, 2005)
A Common and Deadly Pathogen
Streptococcus pneumoniae is a common nasopharyngeal colonizer
and is typically found in the upper respiratory system.
Estimates for how many people are typically infected range from 5% to 70% (Center for Disease Control, 2012). However, just
because we are infected with S. pneumoniae does not mean it is
actively harming us. Rather, S. pneumoniae is considered part of the
normal flora of upper respiratory organisms.
Below is Dr. Sarah Forgie explaining some of the pathogenic characteristics of S. pneumoniae
Despite this fact, Streptococcus pneumoniae is a deadly bacteria accounting for over 22,000 deaths and 445,000 hospitalizations a year from conditions such as meningitis, pneumonia, bacteremia, and ear infections (acute otitis media) within the United States (Cox, 2012). World wide, Streptococcus pneumoniae preys on children, killing as many as 700,000 to 1 million children a year. This accounts for about 11% of all child deaths world wide. Furthermore, it is estimated that 14.5 million cases of serious pneumococcal disease are caused by Streptococcus pneumoniae. (O’Brien, 2009).
Figure
1. Pneumococcal meningitis in an alcoholic patient
(Courtesy of the CDC)
When Streptococcus pneumoniae infects a human, they will
often experience a fever, cough, chest pains, and breathing
difficulties (MedicineNet, 2013). Most of these infections can be
treated with antibiotics however, Streptococcus pneumoniae has a
growing resistance to antibiotics and is becoming more difficult to
treat (this is detailed further in our
adaptions section). It should
be noted that fatality is much higher for patients with suppressed
immune systems, in particular HIV patients who do not have access to
care as is the case in many third world countries (O’Brien, 2009).