Pneumonia Bacteria

Robert C. Colgrove robin at cco.caltech.edu
Mon Jan 17 16:16:54 EST 1994


rpeter at nmsu.edu (Peter Herman x5495) writes:

>In article <758521734.AA05377 at rochgte.fidonet.org> David.Rye at f10.n3649.z1.fidonet.org (David Rye) writes:
>>    As a new microbio student I was pleased to be able to obtain a sputum
>>sample from a patient with pneumonia.  Supposing that the infection is
>>bacterial instead of viral, what types of bacteria am I likely to find in such
>>a culture?  I am expecting several types of coccus but was wondering if I
>>might be likely to see any others which are not just oportunistic "Johnie come
>>latelies".  Thanks.
>>                                                        Dave

>forgive me in advance for sounding like a crabby, conservative,
>safety concious old man but...
>If you have not got enough microbiology experience to know what
>kinds of bugs to expect in a sputum from a pneumonia patient, you
>have absolutely no business handeling such a sample.  
...
>Now, to answer what you asked.  Streptococcus pneumoniae is a common
>cause of bacterial pneumonias.  Klebsiella pneumoniae is less common
>as are a number of others.  You can expect to find all sorts of
>"normal flora " if the sample was not carefully collected, much 
>less if it is a " clean" sputum

Ok, no need to flame this poor fellow. I would guess I have obtained
a fair number more sputum samples from every variety of host than
the vast majority of bionetters so let me take a stab, or should I say
swab at this.

There are a gazillion different pathogens known to cause pneumonia
but relatively few are common in normal hosts. The first question to
ask when examining a sputum sample is whether it is a "good" sputum
[caution to the weak stomached, discussion of slimy bodily fluids
continues]. A deep cough of thick green yellow gunk is one of the 
great cheap, low-tech but highly informative tests in all of medical
diagnosis. Unfortunately, some folks, especially in distress have a
hard time making a good cough and instead give you a cup of spit.
As alluded in other posts, this is worthless since it just shows
you the normal abundant flora and fauna of the mouth: strep pyogenes,
strep mutans, peptococcus, peptostreptococcus, and the list goes on.
The key is that you should see on gram stain of the sputum lots of
white blood cells (usually neutrophils) and only rarte epithelial
cells. If your sample does not pass this test, toss it and get another.

The next question in the nature of the host. In otherwise healthy
young people, by far the most "typical" pneumonia is oddly enough
atypical pneumonia: viral (Influenza, RSV, adenovirus, etc), mycoplasma,
and certain chlamydia (so called TWAR agents). The hallmark of these
is relatively dry cough, usually no focal infiltrate on chest xray,
frequent sytemic signs of malaise and myalgias and an ABSENCE of visible
bacteria on the Gram stain. The high frequency of these agents explains
the choice of erythromycin as the old standby for "walking" 
pneuomia since ordianary antibiotics (eg penicillin) don't touch the 
atypicals. One suspects bacterial pneumonia when there is copious
green sputum and or consolidation audible with the stethoscope or
visible on the chest xray. Of the typical bacteria, by far the most
common is Strep pneumo, classically referred to as pneumococcus,
appearing as lancet-shaped gram-positive diplococci on the smear.
Clues that suggest pneumococcus are the abrupt onset of fever and
rigors often with blood tinged sputum. Treatment is penicillin
600,000 units every 4 hours though just this year we are beginning
to see increasing reports of resistance in this formerly exquisitely
sensitive strain. It is important to remember that this is the most
likely killer is most groups of people because some of the newer
aggressively marketed antibiotics, most notably ciprofolaxin,
are NOT -despite what the drug ads say- safe alternatives and show
a significant frequency of breakthough. 
	In a totally normal young lung, the next most common
typical bacterial pneumonia wwould probably be group A strep
(Jim Hensons killer). The hallmark here is the fearsome speed of
the infection. Although uniformly pen sensitive, sometimes you
just cannot institue treatment fast enough. I still have nightmares
about a young woman I admitted and helplessly watched die within
hours with a raging strep infection. Important points, don't take
these infections lightly, even in the era of antibiotics, they
still kill young strong people. For reasons not at all clear, strep
infections are making something of a comeback with some horrendous
strains appearing within the last few years. Slam 'em with 
penicillin and say your prayers. In the sputum you should see LOTS
of small black balls in chains and pairs. Do not wait for the 
culture, treat immediately. As an aside, it's also important
to treat group A strep in the throat (strep throat) not so much
to cure the sore throat (that will get better on its own) but to
head off the possibilty of rheumatic fever or glomerulonephritis
that may follow.

After that, there are lots of others that can appear from time to
time. I list below the major players  arranged by the hosts/exposures in which
they are the most common (but for almost all the groups below, the
numerically most frequent are still the "ordinary" bugs like
pneuomococcus, strep, staph and h. flu): 


MOST IMPORTANT: TUBERCULOSIS! In older, debilitated, immunocompromized
or foreign-born patients you must always consider TB. You will not
see these organisms on a gram stain and need to do an acid fast stain
or immunofluorescence and have an experienced person examine the smear.
Respiratory Isolation until TB is ruled out!

Neonates: e. coli  (slender gram negative rod)
Infants: group B strep (gram positive cocci in chains)
Kids: Hemophilus Influeza (tiny gram negative coccobacillary rods)
debilitated hosts: klebsiella (fat gram negative rods)
smokers: H. flu (see above)
chronic lung disease:  H. flu, Staph Aureus (fat gram positive "grape clusters")
			Legionella (white cells, no visible orgs)
old folks: staph A, various gram neg rods
hospitalized patients: Pseudomonas Aruginosa (long gram neg rods)
			enterococcus (group D strep)
			acinetobacter, citrobacter, other nasty gram negS
Central Valley, CA: Coccidiomycosis (fungal spores)
Mississippi Valley: histoplasmosis (spores)
Southeast: Blastomycosis (spores)
Southeast Asia: Meliodosis (Pseudomonas meliodii)
		Paragonimus Westernmani (lung fluke)
Sheep exposure: Q fever (coxiella burnettii) no orgs visible
Slaughterhouse: brucellosis -no orgs visible
Rabbits: tularemia, (francisella tularensis)
Contaminated animals: Anthrax  (gram positive bacillus)
Squirrels in Northern CA: Plague, (Yersinia Pestis)
Drunk, demented: Polymicrobial aspiation of Mouth flora
	(anaerobes if person has nasty teeth)
And last but not least, Immunocompromised Patients:
anything under the Sun! but most commonly all the common ones
(pneumococcus, strep, h. flu, staph) just meaner. Also:
Pneumocystis Carinii (need to stain with toluidene blue or antibody)
Toxoplasma (visualize with Giemsa stain)
Nocardia (modified acid fast stain)
Aspergillus (filimentous fungi on silver stain)
Atypical Mycobacteria (acid fast stain)
Cytomegalovirus (cytopathic effect on shite cells)

Despite the admonition of the last crabby poster, only TB
is both common and a risk to the lab personnel. If TB is not
an issue, the other dangerous airborne agents (tularemia, brucella,
anthrax) are very uncommon or like cocci, blasto, histo, 
geographically restricted. Many could pose a risk, though, to
immunocompromized individuals (AIDS, chemotherapy, congenital
immunodeficiencies, high dose steroids, etc). Ask the person
who gave you the sample to make sure noNe of the above is
at issue and then use normal common sense. Don't inlale the stuff,
wear gloves, flame your intstruments (no pun intended).

I could list many more but my cells are now ready to harvest and
I better go. Let me just sya theat I have seen and or treated all
of these at least once with the exception of plague and anthrax
but my best case was the time I got a frantic call from a medical
intern in the emergency  room at the Brigham and Women's hospital
in Boston, saying that the acid fast stain of the sputum of an AIDS
patient was full of snakes! He was only half kidding. I ran down
there (the guy was coughing blood), peeked at the scope and
sure enough it was loaded with brilliant acid-fast (bright red)
millimeter long serpents against the deep blue methylene-blue
counter-stained field. Pulmonary Stongyloides! Pinworm of the lung.
A wild dissemintated infection of the immunocompromized host.
Ten days of thiabendazole, special ordered from the CDC
and he was back on the street...

Hope this helps!
robin colgrove
fellow, joint program in infectious diseases
harvard school of medicine
colgrove at xtal10.harvard.edu




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