Gram Negative Bacteria - Microbiology - Lecture Slides, Slides for Microbiology. Aliah University
jojy30 January 2013

Gram Negative Bacteria - Microbiology - Lecture Slides, Slides for Microbiology. Aliah University

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Gram Negative Bacteria, Medical Importance, Cocci, Family Neisseriaceae, Blooded Animals, Acinetobacter, Neisseria Gonorrhoeae, Neisseria Meningitidis, Primary Human Pathogens, Pili are some points from these slides of M...
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Foundations in Microbiology

The Gram-Negative Bacteria of Medical Importance

1 Chapter 20

Gram Negative Bacteria


Family Neisseriaceae

• Gram-negative cocci • Residents of mucous membranes of warm-

blooded animals • Genera include Neisseria, Moraxella,

Acinetobacter • 2 primary human pathogens

Neisseria gonorrhoeae Neisseria meningitidis


Neisseria • Gram-negative, bean-shaped, diplococci • No flagella or spores • capsules on pathogens • pili • Strict parasites, do not survive long outside of

the host • Aerobic or microaerophilic • Pathogenic species require enriched complex

media and CO2 4

Neisseria gonorrhoeae • Causes gonorrhea, an STD • Virulence factors: pili, other surface molecules, IgA

protease • Strictly a human infection • In top 5 STDs • Does not survive more than 1-2 hours on fomites • Infection is asymptomatic in 10% of males and 50%

of females


Neisseria gonorrhoeae



• Males – urethritis, yellowish discharge, scarring & infertility

• Females – vaginitis, urethritis, salpingitis (PID), common cause of sterility & ectopic tubal pregnancies

• Extragenital infections – anal, pharygeal, conjunctivitis, septicemia, arthritis




Potential scar tissue blockage infertility



Potential for PID (pelvic inflammatory disease)

Gonorrhea in newborns • Infected as they pass through birth canal • Eye inflammation, blindness • Prevented by prophylaxis after birth


Gonorrhea diagnosis


Neisseria meningitidis

• Virulence factors – capsule, pili, IgA protease • Many strains exist • Prevalent cause of meningitis • Disease begins when bacteria enter bloodstream,

pass into cranial circulation, multiply in meninges; very rapid onset; endotoxin causes hemorrhage and shock; can be fatal

• Treated with penicillin, chloramphenicol • Vaccines exist


Neisseria meningitidis


Spread of bacteria from a nasopharyngeal infection to blood and CSF

The Gram-Negative Bacilli of Medical Importance

14 Chapter 20

Septic Shock-Endotoxic shock • LPS (lipopolysacchardide)

Component of Gram negative cell wall is a potent immune stimulant.

• May lead to circulatory failure, tissue damage and death


Release of LPS as bacteria breaks apart

Aerobic Gram-Negative Bacilli

Pseudomonas – an opportunistic pathogen • Brucella & Francisella – zoonotic pathogens • Bordetella & Legionella – mainly human

pathogens • Alcaligenes – opportunistic pathogen



• small gram-negative rods with a single polar flagellum, produce oxidase & catalase

• highly versatile metabolism


Pseudomonas aeruginosa

18 Single polar flagellum

Pseudomonas aeruginosa • common inhabitant of soil & water (ubiquitous-wide spread) • intestinal resident in 10% normal people • grapelike odor • greenish-blue pigment (pyocyanin) • resistant to soaps, dyes, quaternary ammonium

disinfectants, drugs, drying • frequent contaminant of ventilators, IV solutions,

anesthesia equipment • opportunistic pathogen


Pseudomonas aeruginosa • common cause of nosocomial infections

in hosts with burns, neoplastic disease, cystic fibrosis

• Can cause: pneumonia, UTI, abscesses • Septicemia can lead to: endocarditis,

meningitis, bronchopneumonia • Corneal ulcers from contaminated lens

solutions • Ear infections (Otitis) “swimmer’s ear” • Skin rash (contaminated hot tubs,

saunas, swimming pools) • multidrug resistant


Pseudomonas aeruginosa

21 Skin rash/eruption

Pseudomonas aeruginosa

22 Pseudomonas aeruginosa Staphylococcus aureus

Multiple drug resistance

Brucella • tiny gram-negative coccobacilli • 2 species

Brucella abortus (cattle) – Brucella suis (pigs)

• Brucellosis (synonyms=malta fever, undulant fever, & Bang disease) – a zoonosis transmitted to humans from infected animals

• fluctuating pattern of fever –weeks to a year • combination of tetracycline & rifampin or streptomycin • animal vaccine available (efforts underway to eradicate

from cattle herds and swine) • potential bioweapon



24 Undulating fever

Francisella tularensis • causes tularemia, a zoonotic disease of mammals

endemic to the northern hemisphere, particularly rabbits

• transmitted by contact with infected animals, water & dust or bites by vectors

• headache, backache, fever, chills, malaise & weakness • 10% death rate in systemic & pulmonic forms • intracellular persistence can lead to relapse • gentamicin or tetracycline • attenuated vaccine available • potential bioterrorism agent


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