review of bacterial infection specimen

8/2/2019 Review of Bacterial Infection Specimen

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Review of Bacterial infection

specimenFor OSCE examination


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To Find more Mycobacterium TB

S. aureus

Klebsiella

Cell wall differences - +ve, -ve, Mycolicacid

AFB

MAFB

Burkhloderia pseudomellei


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Gram Stain


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Bacterial Cell Wall


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The cell wall of a bacteria(1) is found externally to the plasma membrane.(2) is semirigid.(3) protecting bacteria against osmotic lysis.

(4) consists of peptidoglycan.


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Lactobacillusspp..


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Gram positive bacilli


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Typical Gram stains

Gram-positive bacilli:

Thick: Clostridium

Thin : Listeria.

Branched:Nocardia,

Actinomycetes


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Clostridium perfringens

No surrounded RBC (Cell lysis)


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Clostridiumwith subterminal spores

Susan D. Caston


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Diphtheroids (Propionibacterium andCorynebacterium spp)

Susan D. Caston

The orientation of the bacteria in the clumps, at variable andrandom angles, sometimes called "Chinese letters" Many other

bacteria also have this appearance, includingRothia spp,


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Listeria monocytogenes


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Lactobacillus

Susan D. Caston

Chains of Gram-variable, but mostly Gram-positive, non-

sporing, regular small bacilli. This is characteristic of

Lactobacillus, especially in genital tract specimens.


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Nocardia


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Actinomyces

Susan D. Caston


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Mycobacterium

Susan D Coston

Mycobacterium species ,especially the rapidly growing

mycobacteria, such asM. fortuitum andM. chelonae can

sometimes be seen in Gram stains as beaded gram-positive=


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Mycobacterium marinum "ghosts"

Susan D Caston


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Hyphae

Susan D Coston


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Bacillus anthracis in CSF

Jernigan JA: EID 2001;7:933-944


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Bacillus cereus
http://www-micro.msb.le.ac.uk/video/Bcereus.mov


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Gram positive cocci


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Typical Gram stains

Gram-positive cocci:

Cluster: Staph. Aureus

Tetrad: Micrococcus spp.

Chain: Streptococcus


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Staph. Vs. Pneumococcus


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Pneumococcus

Lancet-shaped,

diplococci withcapsule


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S.pneumoniae


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Streptococcus

Susan D. Caston


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Viridans Streptococcus

Susan D. Caston

Usually forms short to long chains. The individual cells are

often elongated.


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Streptococcus pyogenes


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Gram negative cocci

T i l G t i


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Typical Gram stains

Gram-negative cocci :

Diplococci: usually characteristic ofNeiseria spp., such as

N gonorrhea orN meningitides. In addition,Moraxella spp.

andAcinetobacter spp.are often diplococcal in morphology.

Acinetobacter can be pleomorphic, and sometimes appear

as Gram-positive cocci.


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N. gonorrheae Acinetobacter spp.

Acinetobacter- A major characteristic of this species is itsgram stain morphology: they appear as gram-negative

coccobacilli but are frequently confused with gram-

negative diplococci characteristic ofNeisseriaspp.

Susan D. Caston

Acinetobacter spp


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Acinetobacter spp.

Acinetobacter often stains as Gram-variable cocci or coccobacilli. It

is not unusual for this bacterium to stain as a Gram-positive coccus

in blood cultures positive for the bacterium. Ifflattening of the"cocci" at their apposing surfaces is observed, then acinteobacter

should be high on the list. Too short a period of destaining with

acetone-alcohol can also present this picture, but in this case the red

color of the proteinaceous background suggests that this was not the

case here Susan D. Caston


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Acinetobacter spp.

Susan D. Caston


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Gram negative bacilli


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Typical Gram stains

Gram-negative coccobacilli :H influenzae


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Typical Gram stains

Gram-negative bacilli :

Thin rods:E coli


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An advancing colony of Klebsiella bacteria is halted when itencounters an antibiotic.

Source: : Gary Carlson,

www.gcarlson.com/microbial_krebsiella.htm
http://www.gcarlson.com/microbial_krebsiella.htmhttp://www.gcarlson.com/microbial_krebsiella.htm


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Typical Gram stains

Gram-negative bacilli :

Curved rods: Vibrio

Campylobacter

Thin needle shape:

Fusobacterium


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Seagull-wings

appearance

Campylobacter

Susan D. Caston


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Fusobacterium

Susan D. Caston

The needle-like tapering ends of the bacilli are specific forthis species. The only other commonly encountered

Fusobacterium species,F. necrophorum, does not possess

the tapering ends and tends to be much more pleomorphic.


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Candida

Susan D Caston


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Cryptococcus neoformans

Susan D Caston

\Cryptococcus neoformans in spinal fluid. These yeast can

be easily mistaken for blood monocytes, especially when

they are present in low numbers.

review of bacterial infection specimen

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