Gram-Negative Bacteria and Neisseria Overview

Study Notes

Lipid A in the bacterial cell wall can lead to disseminated intravascular coagulation and potential endotoxic shock.

Neisseria gonorrhoeae and Neisseria meningitidis are important pathogens.
Neisseria gonorrhoeae only infects humans and can evade the immune system.
It causes ophthalmia neonatorum, a serious eye infection in newborns.
Gonorrhea can lead to sterility in women and is difficult to treat due to resistance.
Neisseria meningitidis is a common cause of meningitis in individuals under 20 years old.
It can cause death within 6 hours of symptoms and is spread through respiratory droplets.
Vaccination protects against some serogroups but not serogroup B.

Enteric bacteria are the most common gram-negative pathogens in humans, often opportunistic.
They are ubiquitous and commonly found in the environment.
They can be identified using O antigen and H antigen on the surface.
Enterobacteriaceae are distinguished by their ability to reduce nitrate to nitrite and ferment glucose.
They are typically diagnosed by finding enteric bacteria in urine, blood, and cerebrospinal fluid.
Coliform opportunistic enterobacteriaceae are indicator organisms, used to assess water quality.
They can cause gastroenteritis.
E. coli O157:H7 is a prevalent pathogenic strain that produces Shiga-like toxin.
Truly pathogenic Enterobacteriaceae include Salmonella, Shigella, and Yersinia, which often cause human infections through contaminated food.
Salmonella causes typhoid fever, while Shigella causes dysentery.
Yersinia is responsible for bubonic and pneumonic plague.

Pasteurellaceae are oxidase positive.
Haemophilus influenzae is a common cause of meningitis in young children.
Bordetella pertussis causes whooping cough, characterized by violent coughing and gasping for air.

Pseudomonas aeruginosa is an opportunistic pathogen that can cause infections in immunocompromised individuals.
It is ubiquitous in the environment and forms biofilms for protection.