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


Description: 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 Microbiology. This is one of basic and important subject in Biological science. As a branch of Biology, we can say Microbiology covers half studies in Biology.
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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


Bordetella pertussis • minute, encapsulated coccobacillus • causes pertussis or whooping cough, a

communicable childhood affliction • acute respiratory syndrome • often severe, life-threatening complications in

babies • reservoir – apparently healthy carriers • transmission by direct contact or inhalation of

aerosols • May be relatively common in adults (as chronic

cough) and be misdiagnosed as a cold or the flu


Bordetella pertussis

• virulence factors – receptors that recognize & bind to ciliated respiratory

epithelial cells – toxins that destroy & dislodge ciliated cells

• loss of ciliary mechanism leads to buildup of mucus & blockage of the airways

• Hacking coughs followed by abrupt deep inhalation (whoop)

• Vaccine does not give long-term immunity so adults and older children can have a recurrence




Prevalence increasing due to decrease in vaccination rate in children as a result of concern over its publicised vaccine side effects


• live primarily in soil & water • may become normal flora • A. faecalis – most common clinical species

– isolated from feces, sputum, & urine – occasionally associated with opportunistic

infections – pneumonia, septicemia, & meningitis


Legionella pneumophilia


Legionella pneumophila

• widely distributed in water • 1976 epidemic of pneumonia afflicted 200

American Legion members attending a convention in Philadelphia & killed 29 (source was a contaminated air-conditioning system) Legionnaires disease

• Most prevalent in males over 50 • nosocomial disease in elderly patients • Symptoms: fever, cough, diarrhea, abdominal pain,

pneumonia fatality rate of 3-30% • azithromycin


Enterobacteriaceae Family

• enterics • large family of gram-negative bacteria • many members inhabit soil, water, & decaying matter

& common occupants of large bowel of humans & animals

• all members are small, non-sporing rods • facultative anaerobes, grow best in air • cause diarrhea through enterotoxins • divided into coliforms (lactose fermenters) and non-

coliforms (non lactose fermenters)


Dichotomous Key for the Enterobacteriaceae


Diarrheal Disease • Two Mechanisms

– Toxigenic • Organism itself does not invade the tissue • Enterotoxins released which cause cells to increase secretion

secretory diarrhea

– Invasive • Microbes breakdown epithelial cells and form ulcerations. May see


• Fluid and electrolyte loss may result in dehydration…death. • Diarrheal disease = 40% of infectious diseases

– 18% of death worldwide



Nosocomial Infections

Nosocomial infections from Gram negative enterics


Coliforms- Ferment lactose. (normal enteric flora but may cause infections)

Noncoliforms- Do not ferment lactose. (some are normal enteric flora others are true pathogens…Salmonella, Shigella)

Escherichia coli

• most common aerobic & non-fastidious bacterium in gut

• enterotoxigenic E. coli causes severe diarrhea due to heat-labile toxin & heat-stable toxin – stimulate secretion & fluid loss; also has fimbrae

• enteroinvasive E. coli causes inflammatory disease of the large intestine

• enteropathogenic E. coli linked to wasting from infantile diarrhea; O157:H7 strain causes hemorrhagic syndrome & kidney damage


Escherichia coli

• pathogenic strains frequent agents of infantile diarrhea – greatest cause of mortality among babies

• causes ~70% of traveler’s diarrhea • causes 50-80% UTI • indicator of fecal contamination in water


Escherichia coli O157:H7

The Ready-To- Eat Spinach outbreak of ‘06

E. Coli 0157:H7 outbreak

• September 28, 2006 : 187 people infected in 26 states (97 hospitalized…29 developed HUS)




15 +

2006 Spinach- associated outbreak

Newer Outbreaks

• Nestle Toll House cookie dough (E. coli) June 2009) (72 cases in 30 states)

• Ground beef (E. coli) ( July 2008) (49 cases in 7 states)

• Pepperoni pizza (E.coli) (Oct-Nov 2007) 7.html (21 cases in 10 states)

Other coliforms

Klebsiella pneumoniae– normal inhabitant of respiratory tract, has large capsule, cause of nosocomial pneumonia, mennigitis, bacteremia, wound infections & UTIs

Enterobacter – UTIs, surgical wounds • Serratia marcescens – produces a red pigment;

causes pneumonia, burn & wound infections, septicemia & meningitis

Citrobacter – opportunistic UTIs & bacteremia


43 Capsule of Klebsiella pneumoniare

Noncoliform lactose-negative enterics

Proteus Salmonella & Shigella


Proteus • Swarm on surface of moist agar in a concentric pattern • Cause UTI, wound infections, pneumonia, septicemia, &

infant diarrhea



S. typhi – typhoid fever – ingested bacilli adhere to small intestine, cause invasive diarrhea that leads to septicemia. Asymptomatic carriers perpetuate and spread the bacteria.

S. enteritidis – 1,700 serotypes (varieties)- salmonellosis – can be zoonotic (fecal contamination of food products) (1/3 of all chickens have Salmonella)

– Food Poisoning-gastroenteritis for 2-5 days


A recent Salmonella in peanut butter outbreak

(Late 2008 through 2009)


Phases of Typhoid Fever




50 Patches of mucus and blood

Shigellosis – bacillary dysentery •S. dysenteriae, S. sonnei, S. flexneri & S. boydii •Invades large intestine, can perforate intestine or invade blood (septicemia) •Virulence factors: endotoxin & exotoxins •Treatment – fluid replacement & ciprofloxacin & sulfa- trimethoprim


Yersinia pestis

• Nonenteric…tiny, gram-negative rod • virulence factors – *capsular & envelope proteins that

protect against phagocytosis & foster intracellular growth

*coagulase *endotoxin


Yersinia pestis


Yersia pestis in blood

Yersinia pestis

• humans develop plague through contact with wild animals (sylvatic plague) or domestic or semidomestic animals (urban plague) or infected humans

• found in 200 species of mammals – rodents without causing disease

• flea vectors – bacteria replicates in gut, coagulase causes blood clotting that blocks the esophagus; flea becomes ravenous 53


Yersinia pestis


Infection cycle

Pathology of plague

• bubonic – bacillus multiplies in flea bite, enters lymph, causes necrosis & swelling called a bubo in groin or axilla

• septicemic – progression to massive bacterial growth; virulence factors cause intravascular coagulation & subcutaneous hemorrhage. Necrosis and skin blackening occur – black plague

• pneumonic – infection localized to lungs, highly contagious; fatal without treatment

• treatment: streptomycin, tetracycline or chloramphenicol

• Killed or attenuated vaccine that gives a short-term protection exists


57 Classic bubo (painful nodule that can rupture to the surface)

Pasteruella multocida

• zoonotic genus • opportunistic infections • animal bites or scratches cause local abscess

that can spread to joints, bones, & lymph nodes (septicemia)

• treatment: penicillin & tetracycline


Hemophilus • tiny gram-negative pleomorphic rods • Fastidious. can’t grow on blood agar without special

techniques. • some species are normal colonists of upper

respiratory tract or vagina (H. aegyptius, H. parainfluenzae)

• others are virulent species responsible of conjunctivitis, childhood meningitis, & chancroid



H. influenzae – acute bacterial meningitis, epiglottitis, otitis media, sinusitis, pneumonia, & bronchitis – meningitis symptoms: fever, vomiting stiff neck neurological

impairment. High fatality is untreated – subunit vaccine Hib

H. aegyptius –conjunctivitis, pink eye • H. ducreyi – chancroid STD • H. parainfluenzae & H. aphrophilus – normal oral &

nasopharyngeal flora; infective endocarditis


61 Bacterial meningitis from H. influenzae

62 Pinkeye (infectious conjunctivitis) H. aegyptius

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