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Jul 4, 2023 · Listeria monocytogenes is a facultative, intracellular, gram-positive rod that is responsible for causing the infection listeriosis. Listeria causes severe infection in the elderly, neonates and the immunocompromised with only a self-limited gastrointestinal infection in the immunocompetent.
Jul 22, 2024 · Listeria is a short gram-positive rod that occurs singly or in short chains. However, the identification of Listeria on Gram stain may be challenging. Listeria may resemble pneumococci (diplococci) or diphtheroids (Corynebacteria) or be gram variable and confused with Haemophilus species .
Aug 23, 2023 · The Gram stain indicates a bacterial pathogen consistent with Listeria monocytogenes. L. monocytogenes is usually transmitted by ingestion of contaminated foods such as raw vegetables, dairy products and meat.
Named for Joseph Lister, Listeria monocytogenes is a Gram-positive bacterium, in the phylum Bacillota. Its ability to grow at temperatures as low as 0 °C permits multiplication at typical refrigeration temperatures, greatly increasing its ability to evade control in human foodstuffs.
Listeria monocytogenes Identification Chart. Summary. Major pathogen found in Cerebral Spinal Fluid (CSF) and Blood only. Characteristics. CSF showing Polymorphonuclear leukocytes (PMNs), Monocytes, and Gram-positive rods (may be intracellular). (a-c)Regular small Gram (+) rods. May be short or longer.
Sep 10, 2023 · Small Gram-positive rod, non-spore-forming [ Fig 1 ]. O and H antigens designate Listeria serotypes. Sero-types 1/2a, 1/2b, and 4b cause almost all human infections, and serotype 4b is associated with outbreaks. Isolated from environmental sources such as water, sewerage and foodstuffs.
Listeria monocytogenes is a Gram-positive rod-shaped bacterium. It is the agent of listeriosis, a serious infection caused by eating food contaminated with the bacteria. Listeriosis has been recognized as an important public health problem in the United States.
Nov 20, 2023 · Listeria occurs singly or in short chains. On Gram stain, Listeria may resemble pneumococci (diplococci), enterococci, or diphtheroids (Corynebacteria) or be gram variable and be confused with Haemophilus species .
Gram’s stain of specimens of sterile spinal fluid, peritoneal fluid, or joint aspirates occasionally, but unpredictably, reveals Gram-positive coccobacilli, characteristic of L. monocytogenes. In some forms of central nervous system infection, particularly rhombencephalitis, several samples may have to be obtained to isolate the organism.
Listeriosis is bacteremia, meningitis, cerebritis, dermatitis, an oculoglandular syndrome, intrauterine and neonatal infections, or rarely endocarditis caused by Listeria species. Symptoms vary with the organ system affected.
