History: many different organisms. In this case,

History:

A 79-year-old female presented with shortness of breath and
a productive cough. The patient was brought to A&E in an ambulance after
falling and not having the strength to get up. Other associated symptoms
include fever, hoarseness and vomiting. No weight loss or haemoptysis reported.
No known allergies to any medication.

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Examination:

On examination, the patient was alert and talkative. The
findings were as follows, respiratory rate 24, pulse rate 81, blood pressure
107/57. On auscultation, faint crackles on the right lower lung and a wheeze on
expiration could be heard.

Diagnosis:

The patient was diagnosed with moderate community acquired pneumonia.

Pneumonia can be described as a disease of the lower
respiratory tract which is the result of infection. There are many different
types of pneumonia which are in turn caused by many different organisms. In
this case, we are dealing with moderate community acquired pneumonia which is
known to be caused by either Streptococcus pneumoniae, Haemophilus Influenzae
or Mycoplasma pneumonia. It is important to know which possible organisms are
causing the illness in order to treat it in the most effective and successful
way as not all organisms are sensitive to the same drugs.5 This
essay will discuss the most common pharmacological actions used to treat
moderate community acquired pneumonia.

Moderate community acquired pneumonia is usually treated
with oral antibiotics, most common of which is amoxicillin and a macrolide, usually
clarithromycin. 1 If the patient is allergic to penicillin,
doxycycline can be prescribed as an alternative 9– this is not
relevant in this case. The treatment would be given for five days. 2
The severity of the presenting community acquired pneumonia can be determined
by their CURB 65 score. This test takes into account if they are confused,
their urea, respiratory rate, blood pressure and if they are over 65. 5
It is vital to do a CURB65 score as different severity (either mild, moderate
or severe) as it suggests the possible different organisms causing pneumonia and
thus will aid the choice of antibiotic treatment.

Amoxicillin is the first line of treatment for pneumonia, it
is a member of the penicillin group. This means it cannot be given to patients
with a penicillin allergy. 3 This particular antibiotic acts by
inhibiting cell wall synthesis in bacteria. The resultant lack of cell wall
causes the bacteria to disintegrate. This drug is a relatively safe option as
food does not interfere with the absorption of the drug, therefore making this
therapy easier for the patient to follow the course prescribed. Studies have
also shown that pregnant patients are able to take this drug as there are no
known harmful effects to the foetus. It is also known that small amounts of the
drug can be excreted while breast-feeding and this can result in the child
becoming sensitized to amoxicillin, but no other long term harmful effects. 4
Although not relevant to this particular case, it does mean the drug is
accessible to a wider group of patients. 

Amoxicillin is an active agent that acts against gram
positive organisms – for example, staphylococcus species or streptococcus
species – and gram negative bacterial – such as haemophilus influenza or
Neisseria gonorrhoeae. 4 As the organisms mentioned before includes
the most common causes of community acquired pneumonia, amoxicillin is an
effective drug choice for treatment.

Amoxicillin acts by inhibiting penicillin binding proteins
(PBPs). PBPs are transmembrane surface enzymes, their role is to catalyse the
crosslinking between peptoglycans and the bacteria’s cell wall. PBPs normally
bind to D-alanyl-D-alanine, but amoxicillin is able to mimic the substrate and
bind instead. This results in an incomplete cell wall. However, it this does
limit the drug to only acting on growing cells that are actively synthesising
their cell wall. 4

Amoxicillin is often combined with a macrolide, for example,
clarithromycin, when treating more severe cases of community acquired
pneumonia. 5 A macrolide is an antibacterial drug similar to
penicillin. However, it is effective in many staphylococci strains which are
resistant to penicillin. 6 Clarithromycin is a bacteriostatic drug
which inhibits protein synthesis and therefore cell growth. This is done by
reversibly binding to the ribosomal subunit, 50s, of the sensitive organism. 7
This is illustrated in the diagram below.

(8)

 

When prescribing clarithromycin, it is important to be aware
that the pharmacokinetics can be changed in patients with renal or hepatic
dysfunction. However, this is not relevant in this case. 8

Clarithromycin is noted to work well against strains of
streptococcus, staphylococci and mycoplasma pneumoniae.8 These are
all of the most common organisms associated with moderate community acquired
pneumonia, therefore making it an effective combined treatment plan.

Doxycycline is an alternative to amoxicillin. It is
prescribed when the patient has an allergy to penicillin.9
Doxycycline is a structural isomer of tetracycline. It is noted to have very
good absorption and therefore can be prescribed in smaller doses, decreasing
the likelihood of adverse effects. Doxycycline acts in a similar way to
amoxicillin as it inhibits protein synthesis. 
Doxycycline stops the addition of amino acids to the growing peptide chain
by binding reversibly to the 30s subunit of the bacterial ribosome.10
Doxycycline is known to work effectively against organisms such as
staphylococci strains and mycoplasma pneumonia.10 This makes them
useful in treating moderate community acquired pneumonia, as these are common
organisms involved in this disease. Doxycycline should not be prescribed to
patients during pregnancy, as it is known to have adverse effects on foetal
development.11 This means that females of child birthing age should
be asked if it is possible that they could be pregnant before they receive the
drug. 

This case discussion describes the different drugs that are
commonly used to treat moderate community acquired pneumonia. It highlights the
importance of knowing the severity of the pneumonia by using the CURB65 score
as it helps to give a more specific and accurate guide as to which organism
could be the cause. Thus, allowing for the most effective course of treatment
for the patient. In the case of my clerking amoxicillin and clarithromycin
would be prescribed.

 

 

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