Pseudomonas aeruginosa

Ans.A. Pseudomonas  aeruginosa (non-mucoid) 

• The incidence of pseudomonas aeruginosa infections in cystic has not diminished. Pseudomonas aeruginosa is the most common cause of respiratory failure in cystic .fibrosis patients.

• Acquisition of pseudomonas infection begins early in childhood. The initial acquisition of P.aeruginosa in the CF lung is with non-mucoid strains and occurs early in life. Over time there is a transition to mucoid strain.

• Haemophilus  influenzae, Staphylococcus  aureus and Pseudomonas  aeruginosa are the most prevalent early pathogen in patients with cystic fibrosis.

• Mucoid pseudomonas is much more difficult to treat and eradicate because it lives in a defensive mode of growth called “biofilm”.

• Infants and children experience transient pseudomonas aeruginosa infection within 1 year although they have no symptoms.

• The infection eventually becomes chronic with nonmucoid pseudomonas aeruginosa. This happens in teenage years.

Pseudomonas aeruginosa is a gram-negative rod.

It can easily be distinguished from the family Enterobacteriaceae because Pseudomonas is oxidase positive.

It is an opportunistic pathogen that has an increased chance of causing urinary tract infections in patients with indwelling catheters, or who are on antibiotics.

Candida albicans is a yeast that can cause urinary tract infections in poorly controlled diabetics, because glucose in the urine enhances its growth.

Enterococcus faecalis is a gram-positive coccus that commonly causes urinary tract infections in elderly men with prostate problems.

Escherichia coli is a lactose-positive, oxidase-negative, gram-negative rod that is the most common cause of community acquired urinary tract infections.

Pseudomonas aeruginosa causes malignant otitis externa, which is a severe necrotizing infection of the external ear canal.

Infection tends to spread to the mastoid bone, temporal bone, sigmoid sinus, base of the skull, meninges, and brain.

Patients at increased risk include the elderly, those with diabetes, and the immunocompromised.

Ans. is ‘a’ i.e., Dettol 

• Pseudomonas species grow comparatively well in Dettol.

Cetrimide and dettol have been incorporated in the media for the selective isolation of pseudomonas

Ans. is ‘b’ i.e., P. aeruginosa

Intravascular catheter related infections

.           Indwelling vascular catheters are a leading source of bloodstream infections.

.          Amongst indwelling vascular catheters, central venous catheters are the most common culprits. Pathogenesis

.          There are four potential sources for catheter related infections ‑

1)       The skin insertion site

2)       The catheter hub

3)       Hematogenous seeding from a distant infection

4)       Contaminated infusate

.     The skin insertion site and the catheter hub are by for the two most important sources.

.    Approximately 65% of catheter related infections originate from the skin flora, 30% from the contaminated hub and 5% from other pathways.

.    For short term catheters, skin contamination is the most likely mechanism of pathogenesis.

.    On the other hand, for long term catheters, hub contamination is more frequent because such catheters often have to be intercepted and manipulated.

.   Skin organisms migrate from the skin insertion site along the external surface of catheter, colonizing the distal intravascular tip of the catheter, and ultimately causing blood-stream infection. On the other hand, in hub related infections, organisms are usually introduced into the hub from the hands of medical personnel and the organisms migrate along the internal surface of the catheter, where they can cause a bloodstream infection.

Microbiology

.    Most of the micro-organisms implicated in CRIs arise from the skin flora.

.   Staphylococci are the most frequently isolated pathogens, particularly coagulase-negative staphylococci.

Etiology of catheter related infection

Ans. is ‘d’ i.e., Impipenem + Amikacin

Ans. is ‘a’ i.e., Vancomycin

o Vancomycin is NOT active against pseudomonas.

Ans. is ‘b’ i.e., Pseudomonas aeruginosa

The optimum temperature for growth of pseudomonas aeruginosa is 37 degree and can grow at a temperature as high as 42° C

Pseudomonas aeruginosa

Morphology

• Gram-negative bacilli

• Motile by the polar flagellum

•  Non-capsulated but many strains have mucoid slim layers especially the organisms which are isolated from cystic fibrosis patients.

Culture

• Obligate aerobe

• Colonies emit a distinctive, musty, mawkish, earthy or sweet grape-like odour or corn-like odour.

• Cetrimide agar is a selective media.

• Pseudomonas aeruginosa produces several pigments. The production of these pigments accounts for the colour of colonies.

• Pyocyanin is produced only by P.aeruginosa and it inhibits the growth of many other bacteria.

• Pyoverdin may be produced by many other species.

Ans. is ‘b’ i.e., Ampicillin

Drugs acting against Pseudomonas.

• Penicillins – Piperacillin, Carbenicillin, Ticarcillin, Mezlocillin.
• Cephalosporins – Ceftazidime, Cefoperazone, Cefepime.
• Carbapenems – lmipenem, meropenem
• Monobactams – Aztreonam.
• Aminoglycosides – Tobramycin, Gentamycin, Amikacin.
• Fluroquinolones – Ciprofloxacin, Levofloxacin, Norfloxacin.
• Other – Polymixin B, Colistin.

For most of the infection of pseudomonas, treatment of choice is the combination of an antipseudomonal p­lactam and an aminoglycoside.

Ans. is ‘a’ i.e., P. aeruginosa

• Although otitis externa is also known as swimmer’s ear, malignant otitis externa isn’t due to water remaining in the ear canal.
• Bacteria such as Pseudomonas aeruginosa and Staphylococcus aureus often cause malignant otitis externa.
• The most frequent pathogen is Pseudomonas aeruginosa.

Ans. is’ i.e., Cetrimide agar

Cetrimide and Dettol have been incorporated in the media for the selective isolation of pseudomonas.

Cetrimide agar is a selective media.  

Ans. is ‘a’ i.e., Cephadroxil

Cephalosporins with antipseudomonal activity :- Ceftazidime, Cefoperazone, Cefepime

Ans:A.)Pseudomonas Aeruginosa

• Ecthyma gangrenosum is an infection of the skin typically caused by Pseudomonas aeruginosa.
• It is often seen in immunocompromised patients such as those with neutropenia.
• Ecthyma gangrenosum presents as a round or oval lesion, 1.0 to 15 cm in diameter, with a halo of erythema.
• A necrotic center is usually present with a surrounding erythematous edge, representing where the organism invaded blood vessels and caused infarctions.
• These ulcerative lesions are single or multiple and heal with scar formation, although sepsis resulting from other Gram-negative bacteria can also cause this condition

Ans. a. Piperacillin-Tazobactum

Piperacillin is used in
Pseudomonas infection
Klebsiella infection
Anaerobic-Bacteroides infection

Ans. a. It formed a biofilm on bronchial walls