Microbiology
Summary
Klebsiella pneumoniae, Enterobacter spp., and Serratia marcescens are members of the Enterobacter family of bacteria that play a significant role as nosocomial infections and share the notable trait of multidrug resistance. These bacteria are commonly associated with pneumonia and urinary tract infections (UTIs).
Another shared feature of these bacteria is that they all ferment lactose, a characteristic often used to differentiate between the various Enterobacteriaceae. These lactose fermenters form pink colonies on MacConkey agar. However, it is important to note that Serratia ferments lactose slowly and may sometimes show up negative on a lactose fermentation test. The motility of these bacteria varies, with Enterobacter spp. and Serratia marcescens being motile, whereas Klebsiella pneumoniae is immotile. Additionally, Klebsiella pneumoniae is known for infecting alcoholics, creating abscesses, and causing infections resulting from aspiration. It also has a polysaccharide capsule and is urease-positive.
Lesson Outline
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FAQs
Klebsiella pneumoniae, Enterobacter spp., and Serratia marcescens are gram-negative bacteria that can cause various types of infections. K. pneumoniae is commonly associated with pneumonia, urinary tract infections (UTIs), bloodstream infections, and wound infections. Enterobacter spp. can cause UTIs, skin and soft tissue infections, lower respiratory tract infections, and intra-abdominal infections. Serratia marcescens is known for causing UTIs, wound infections, and respiratory tract infections, including pneumonia.
MacConkey agar is a selective and differential culture medium that is used to isolate and differentiate lactose-fermenting and non-lactose fermenting gram-negative bacteria. Klebsiella pneumoniae and Enterobacter spp. are both lactose fermenters, which means they will utilize lactose as a source of carbon. On MacConkey agar, they will produce pink or red colonies (indicating lactose fermentation). Serratia marcescens, on the other hand, ferments lactose very slowly, and can form pink colonies after extended incubation.
Nosocomial infections, also known as healthcare-associated infections (HAIs), are infections acquired in hospitals or other healthcare settings. Klebsiella pneumoniae, Enterobacter spp., and Serratia marcescens are opportunistic pathogens, meaning they can cause infections in patients with weakened immune systems or invasive medical devices. These bacteria are often found in hospital environments and can be transmitted to patients through contaminated hands or instruments. Their ability to cause serious infections in vulnerable populations makes them significant contributors to nosocomial infections.
One of the major concerns in treating infections caused by Klebsiella pneumoniae, Enterobacter spp., and Serratia marcescens is their increasing multidrug resistance. These bacteria have developed resistance mechanisms against a wide range of antibiotics, including _-lactams, fluoroquinolones, aminoglycosides, and carbapenems. The emergence of multidrug-resistant strains poses a significant challenge in the management of infections caused by these bacteria, as it limits the effectiveness of available treatment options and increases the risk of treatment failure.
