micro sheet # 22 by tara elias

micro sheet # 22 by tara elias
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part 1 :
http://www.mediafire.com/?m8zx5dn4ms5almk

part 2 :

http://www.mediafire.com/?i5hbh0bnnnt95id
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بسم الله الرحمن الرحيم
Part 2 lecture # 22

We will start with the non-fermentor:
If we remember, we mentioned that enterobacteriaceae all ferments glucose [by default when we say fermentor we mean glucose].
-These organisms that don’t ferment glucose are collectively classified into non-fermentors & the MOST important genera of organisms that cause human diseases and don’t ferment glucose are:
Pseudomonas, acintobacter, stenotrophomonas, moroxella, alcaligenes, Sorry I’m not sure about the names, I will try to know them as soon as I get the slides … en$Allah).
-So there are many organisms that belong to this category (non-fermentor glucose) BUT they may oxidase glucose which is a characteristic that isn’t present for enterobacteriaceae because they lack oxidase but these organisms may or may not have oxidase.
-They are usually opportunistic pathogens …..BUT pseudomonas & the most imp is aeruginosa species
-acinetobactar baumannii
-Moroxella  catarrhalis
In the past it was called branbovella but now moroxella is agreed upon classification.
**Remember we mentioned some words about it when we discussed neisseria
-Burkholderia species  cepacia is the most important.
Also we have an additional 2 species:
• Pseudomallei
• mallei
- Alcaligenes  pecallus.
- Stenotrophomonas  stenotrophomonas maltophilia….which was with burkorideria are classified as pseudomonas but not any more because stenotrophomonas maltophilia are oxidase negative.
- pseudomonas are abundant organisms that are found in different locations in the environment , soil, vegetation & water….so they are widely disseminated in nature, every where….because of their simple growth requirements also they can obtain carbon & nitrogen from different sources.
-More than 30 organic compound can be used as the only source of carbon & nitrogen.
-Some times they can grow at distilled water and this is due to their ability to utilize trace of elements for their growth, & additionally they may grow on disinfectant (they are highly resistant to disinfectants & antimicrobial agents)
-They are one of the most resistant organisms to antibiotics, & they have been recovered from hand washing soaps (liquid or solid) because they can even grow on disinfectant.

**The importance of these organisms:
1) Simple growth requirements.
2) Highly resistant organisms to disinfectant & antibiotics.

-They are found in hospitals & that’s why it’s the MAJOR cause of hospital acquired because they are recovered from almost all sites of the hospitals … like food, sinks, toilets, respiratory therapy equipments and disinfectant solution as we mentioned before.

-However, they are not part of the normal flora of humans or less than 5% of humans have them normally on their GI tract. [(3-5%) may have them as transient carrier]… (95-97% lacks them)

-Fortunately they are not part of the normal flora.
-Resistant carriage of normal flora is NOT common & these individuals are usually hospitalized (immunocomprimised).

-strange that they don’t form part of the normal flora, although they are abundant in the environment.

-Also they posses a number of structural particles & toxins that enhance the virulence potential of these organisms as well as making resistance to environmental & antimicrobial agents.

--As we mentioned that these organisms are just opportunistic pathogens meaning in healthy individuals they cause nothing….they ONLY cause diseases in hospitalized patients (immunocompromised patient) like burn individuals.

- Pseudomonas areginosa is the MAJOR common cause of infection among burn individuals (skin infection) or cystic fibrosa (lung abnormalities) or cancer…..BUT normal individuals don’t develop infection with pseudomonas.

- pseudomonas is an opportunistic pathogen meaning it doesn’t cause infection in normal healthy individual.

 NOW regarding their structural physiology:
• They are gram –ve
• Motile organisms , although they contain a single polar flagella
• They are actively mobile.
• SIM test for H2S & motility …they produce an umbrella like change in the semisolid media (SIM).
• The motility can be demonstrated in the form of an umbrella like structure in SIM.
• Non-fermentor (don’t ferment glucose) but they can use few carbohydrates like glucose by oxidation rather than fermentation ribose gluconate.
• Oxygen is determined as electron acceptor that is why they are aerobes NOT facultative anaerobes.
• They are obligatory aerobes.
• Presence of cytochrome oxidase is used to differentiate this group from enterobacteriaceae.
• They are oxidase +ve & this is one of the major characteristics that used to distinguish pseudomonas from enterobacteriaceae (oxidase –ve).



Now regarding their ability to produce toxin:
-Most strains are encapsulated & production of polysaccharides could be abundant (slime) & that is why they can be covering the plates because of the abundance of polysaccharides.

-Some strains produce sweet odors (very sweet) like grape odors!!
-Also they produce diffusible pigments that are why the colonies could be green produce (bioviridin) or blue produce (pyocyanin) or red dark (….??....) or dark [there are some words I’m not able to understand….!!! I will check it].
SO…the colonies could be bluish, greenish, blackish or reddish because of the production of diffusible strains in the plates & the sweet odors….that is why when you see it you will not miss it at all..(Some perfumes companies use it to produce perfumes!!)

-These pigments are lethal to the other strains that don’t produce pigments.

**That is why for pyocyanin (blue) in particular we have what is called  pyocyanin typing of pseudomonas …there are more than 250 different types of pyocyanin producing pseudomonas.

*The typing is done by adding pyocyanin into the colonies ..If it kills then it is not pyocyanin type… (Usually the strains that produce a substance are not affected by this substance).

*Pseudomonas aeruginosa are the MOST common clinically & best characterized among the 3rd species that belongs to this group.


**NOW about a pic….. The greenish & bluish with antibiotics suscibility test
-So organisms that produce pigments used to make a diagnosis of pseudomonas & as we mentioned before we have reddish & blackish pigments in additional to the green & bluish.
-Most research on antimicrobial agents is to produce new antimicrobial agent to treat pseudomonas...it is an intention for the search.
-We have isolates of pseudomonas & acinetobacter that are resistance to everything.

 Pathogenesis:
*Virulence factors:
1) Structural component……include:
A. Pilli for attachment.
B. The polysaccharide (capsule)which is anti phagocytotic (paralyze the ability to phagocyte .
C. Endotoxin… because it is gram –ve causes all biological effects associated with this substance.

2) Toxin.
3) Enzymes.
**Now about the TOXIN:
Exotoxin A blocks eukaryotic cell protein synthesis .


-Exoenzyme S  heat stable substance that inhibit protein synthesis
-Elastase, protease & phospholipase each of which has it is own function. SO
-Elastase catalyzes destruction of elastic fibers in blood vessels resulting in hemorrhage lesion (bleeding).
-Phospholipase C  breaks down lipids and vesicles this affects the cell membrane in particular.
-protease  tissue destruction because they digest proteins, they inactivate antibodies and they inhibit nutrophils (inhibit the attraction of nutrophils promoting the spread of infection.


Clinical syndrome:
{Remember that pseudomonas is opportunistic pathogens  so these infections are observed in imunocomprimised, it’s unlikely for a normal individual living in the community to develop pseudomonas}.
1. Bacteremia & endocarditis: Especially in patients in ICU, catheterized patients, many intramuscular devices and central line.

Similar to gram –ve but they are difficult to treat  high mortality rate because these patients lack normal immunity. (UTI, respiratory infection, skin infection, burn infections and cystic fibroses).

2. Pulmonary infection: range from colonization or benign bronchitis to severe necrotizing bronchopneumonia.

So the infection can be mild or severe causing necrotic changes in the lung, which is common with patients suffering from cystic fibroses and chronic pulmonary disease (smokers who develop COPD, cancer and cystic fibroses).

3. Ear infection: common and characteristic of pseudomonas aeruginosa.

** Pseudomonas aeruginosa is the most common cause of external otitis or otitis
Externa .Usually this is acquired from swimming with significant risk
factors. That’s why it’s called “swimmer’s ear”

 So immunocomprimized patients {like diabetes} may suffer from ear
Infection from swimming in contaminated pools.
 A more virulent form … Malignant external otitis can invade the
Underlying tissues also associated with chronic otitis.
 Ear discharge may last for months to years {characteristic of ear infection caused by pseudomonas}. The pus is greenish or bluish because it’s caused by organisms that produce these pigments. Also it can be carcinogen.

4. Burn infection: are very common
Burn patients can be infected either by:
a) Pseudomonas aeruginosa.
b) Staphylococcus aureus
But contamination by both is common.
**As you know burn removes the skin which predisposes the infection {the continuity of the skin is lost}.
**One of the most important reasons for resistance to infections is intact skin but here the skin is burned (removed)  depending on the severity of the burn the patient develop skin infection that may be disseminated and complicated with bacteremia and in such cases the pseudomonas infection is very fatal (in addition to staph).


5. Ecthemya gangulosum: a special infection of the skin that develops into black color and become gangrened.
** So it’s a specific skin infection developing among immunocomprimized patients with blackish lesions that develops into gangrene. The organisms can be recovered from such cases.

6. UTI: with prolong catheterization.
7. Eye: due to trauma, surgery. Panophthalmitis can develop
8. CNS infection: meningitis and other.
9. GI infection: rare but colonization can take place especially among children {immunocomprimized children}.



Burkholderia:
Was classified in the past as pseudomonas but careful examination reveled significant differences at the molecular level between pseudomonas and Burkholderia. That’s why they have been classified in different genus.
** Species of cepacia are the most important form that cause hospital acquired diseases. It causes necrotizing pneumonia and bacteremia especially in neonatal units. (In intensive care units of neonates). But it can cause adult diseases as well.

**We had an outbreak in Burkholderia among neonates with high mortality rate. (60-70%).
**It’s very similar to pseudomonas to the fact it’s oxidase +ve , producing highly mucoid colonies.
**It’s another pathogen of hospitalized patients.

 Burkholderia mallei and pseudomallei are less common and usually are animal pathogen  they cause glanders ( a disease of animals that can be transmitted into humans, usually begins as an ulcer of the skin and mucus membrane followed by ….? And sepsis).
 Pseudomallei cause melioidosis ( localized supportive pus infection that may lead to septicemia and the most common form of it is pulmonary {chronic}).


 Note that in Wikipedia  Burkholderia mallei is responsible for glanders, while pseudomalleus is responsible for melioidosis.


Stenotrophomons maltophilia:
Organism that was also classified as pseudomonas but it differs significantly in the GC content and DNA level that’s why it’s reclassified separately.
** It’s a free living oxidase –ve rods  so it lacks the oxidase enzyme.
** It’s the 2nd most common organism isolated as opportunistic pathogen after pseudomonas.


**It’s multi resistant to antimicrobial but its characteristic feature is suscibility to co-trimoxizole, which is 1-5 combination of sulfamethoxazole with trimethoprim. Each alone is bacteriostatic as you can remember but their combination is bactericidal.
**So this organism is resistant to most antimicrobial agents, but is suscbitile to co-trimoxizole.


Acinetobacter:
Has emerged in the recent years as one of the most important hospital pathogen.
**In the past it was regarded as a benign organism.
Most infection in intensive care units in hospitals are now caused by acinetobacter  so is a highly resistant organism and a common cause of hospital acquired infection.

**Usually it cause respiratory tract infection (a contaminate of the hem modifier in artificial respirator from where infections spread to those patients causing infection but it can be disseminated to blood stream causing septicemia.

**an individual who undergo neurosurgical operations may develop meningitis caused by acinetobacter, which is difficult to treat  so it’s is another cause of meningitis and respiratory tract infection.

**Normally the organism is present in most environments have been found from contaminated respiratory therapy equipment, normally present in the skin, GI, distal tip of urethra  the distal part of urethra is inhibited by acinetobacter, that’s why isolation of acinetobacter from urine does NOT mean UTI because it’s normally present their. The patients are asked to collect the mid stream urination in cases of UTI to establish diagnoses not the fist portion, because the 1st portion can contain acintobacter which confuse diagnoses.

**This organism is difficult to treat, highly resistant to antimicrobial agents and common among infected individuals.

We will start a new family
Pasteurellaceae: a family other than non-fermentor that consist of 3 genera
 Haemophilus
 Actinobacillus
 Pastorella

**Haemophilus is the most common and the most important pathogen in the family, which are gram –ve, non-motile bacilli that are either aerobes or facultative anaerobes and they are the most fastidious organism requiring enrichment with blood and other components to isolates.



-- Good Luck --

Done By: Tara Elias
Lecture NO. : 22
Date of lecture: 7-11-2010


good luck all

part 2 of the sheet.........added