Klebsiella species - Infection Management & Treatment
The most clinically important species of this genus is Klebsiella pneumoniae. This large, non-motile bacterium produces large sticky colonies when plated on nutrient media. Klebsiella's pathogenicity can be attributed to its production of a heat-stable enterotoxin. K. pneumoniae infections are common in hospitals where they cause pneumonia (characterized by emission of bloody sputum) and urinary tract infections in catheterized patients. In fact, K. pneumoniae is second only to E. coli as a urinary tract pathogen. Klebsiella infections are encountered far more often now than in the past. This is probably due to the bacterium's antibiotic resistance properties. Klebsiella species may contain resistance plasmids (R-plasmids) which confer resistance to such antibiotics as ampicillin and carbenicillin. To make matters worse, the R-plasmids can be transferred to other enteric bacteria not necessarily of the same species.
Klebsiella pneumonia tends to affect people with underlying diseases, such as alcoholism, diabetes and chronic lung disease. Classically, Klebsiella pneumonia causes a severe, rapid-onset illness that often causes areas of destruction in the lung.
Infected persons generally get high fever, chills, flu-like symptoms and a cough productive of a lot of mucous. The mucous (or sputum) that is coughed up is often thick and blood tinged and has been referred to as "currant jelly" sputum due to its appearance.
Mortality in Klebsiella pneumonia is fairly high due to the underlying disease that tends to be present in affected persons. While normal pneumonia frequently resolves without complication, Klebsiella pneumonia more frequently causes lung destruction and pockets of pus in the lung (known as abscesses).
--Cause of lobar pneumonia (major syndrome), urinary tract infections, biliary and surgical wound infections (often in association with other organisms), rhinoscleroma (rare).
--Gram-negative, aerobic bacilli of the family Enterobacteriaceae. Major pathogens: K. pneumoniae, K. oxytoca.
--Often, but not always, nosocomial pathogen.
--Lobar pneumonia due to K. pneumoniae typically in debilitated, elderly, alcoholic or diabetic patients.
--Lobar pneumonia often necrotic, associated with "currant jelly" sputum and abscess/cavity on chest Xray, classic "bowed fissure sign" caused by swollen upper lung lobe impinging on lower lobe.
--Klebsiella spp. often resistant to many abxs, including cephalosporins (eg extended spectrum beta-lactamase/ESBL) and aminoglycosides; empiric coverage should be tailored to local resistance patterns.
--Primary pyogenic liver abscess due to K. pneumoniae is a newly recognized syndromew which includes monomicrobial infection with no underlying cause, often associated with gas formation.
SITES OF INFECTION
Nasal passages: Rhinoscleroma (Mikulwicz cells--foamy macrophages with ingested bacilli) due to K. rhinoscleromatis
Liver: primary monomicrobial pyogenic liver abscess due to K. pneumoniae, may be associated with gas production; may be either single large abscess or multiple small abscesses
Lung - both nosocomial and community acquired in elderly, debilitated, alcoholic, diabetic patients
Urinary tract - bladder and kidney, usually nosocomial, often catheter-related, may lead to sepsis
Bloodstream - usually associated with primary organ system infection; can be peripheral IV or central venous catheter associated; neutropenic fever due to intestinal source
Eye - endophthalmitis (rare), in association with liver abscess, diabetes
Bone and joints - in association with decubitis ulcers leading to polymicrobial infection
Monotherapy sufficient. Concern of ESBL in toxic patient may prompt empiric choice of carbapenem +/- aminoglycoside.
Ceftazidime 2g IV q8h
Cefepime 2g IV q12h
Piperacillin 4g IV q4h
Ticarcillin 3-4g IV q6h
Aztreonam 1g IV q8h
Imipenem 500mg IV q6h
Ciprofloxacin 400mg IV q8-12h or other fluoroquinolones in standard maximum doses
Adjunctive: Gentamicin 5-7 mg/kg IV qd
Urinary tract infection
Uncomplicated UTI: empiric oral fluoroquinolone, change according to in vitro sensitivities.
Complicated UTI: cephalosporins, advanced penicillins, fluoroquinolones as for pneumonia
Complicated UTI: gentamicin or tobramycin 1.5mg IV q8h or 5-7 mg IV qd or amikacin 7.5mg/kg IV q12h or 15 mg/kg IV qd
Pig-tail catheter drainage for single, large abscess.
Monotherapy appropriate, as described above for pneumonia and sepsis; uncommonly need anaerobic coverage unless presence of stones or anatomical abnormalities predisposing to polymicrobial infection.
How are gene sequence analyses modifying bacterial taxonomy?
The case of Klebsiella