Chapter 20: Gram negative Bacilli

Psuedomonas aeruginosa

Psuedomonas aeruginosa

• Small gram negative rod with a singular polar flagellum

• Common inhabitant of soil and water

• Multidrug resistant; Resistant to soaps, dyes, quaternary ammonium disinfectants drugs or dyes

• Opportunistic; contaminant of ventilators, IV solutions, and anesthesia equiptment

Complications caused by pseudomonas aeruginosa

• Nosocomial infections in burn patients, neoplastic disease, and cystic fibrosis

• Pneumonia

• UTI

• Abscesses

• Otitis

• Corneal disease

• Endocarditis

• Meningitis

• Bronchopneumonia

Pyocyanin

Greenish-blue pigment produced by pseudomonas aeruginosa

Francisella tularensis

• Causes tularemia

• Often considered one of the most infectious of all bacteria

• Potential bioterrorism agent

Tularemia

• A zoonotic disease of mammals endemic to the northerns hemisphere

• Particularly rabbits; “rabbit-fever”

• Transmitted by contact with infected animals, water, dust, or bites from vectos (ticks, flies, mosquitoes)

Effects of tularemia

• Headache

• Backache

• Fever

• Chills

• Malaise

• Weakness

• Ulcerative skin lesions

• Swollen lymph glands

• Conginctival inflammation

• Sore throat

• Intestinal disruption

Bordella pertusis

• Minute encapsulated coccobacillus

• Causes pertussis or whooping cough

Pertussis

• whooping cough

• Communicable childhood affliction

• Acute respiratory syndrome

• Carriers are healthy (reserviours)

• Transmission by direct contact of inhalation

• Vaccina available - DTaP

Virulence factors of bordella pertussis

• Receptors that recognize and bind to ciliated respiratory epithelial cells

• Toxins that destroy and dislodge ciliated cells

• Loss of ciliary mechanisms leads to buildup of mucus and blockage of the airways

Legionella pneumophila

• Widley distributed in water; ameobas

• Causes legionnaires disease and pontiac fever

Legionellosis

• Legionnaires disease and pontiac fever

  • Pontiac fever is milder

• Prevalent in males over 50

• Not transmissible

• Causes fever, cough, diarrhea, and abdominal pain

• Treated with levofloxacin and azithromycin

Enteric bacteria

• Gram negative bacteria

• Non-spore-forming rods

• Inhabits soil, water, decaying matter, and are occupants of an animal’s large intestine

• Cause of diarrhea through enterotoxins

Characteristics of enteric bacteria

• Glucose fermentation

• Nitrate reduction

• Oxidase negative

• Presence of flagella

• Regular, straight rods

• Coliforms = lactose fermenters; fecal matter

• Noncoliforms = non-lactose fermenters; no fecal matter

Virulence factors of enterics

• Complex surface antigens

  • H = flagellar antigen

  • K = capsule and/or fimbrial antigen

  • O = somatic or cell wall antigen

• Production of endotoxins and exotoxins

Escherichia coli

• Most common aerobic and non fastidious bacterium in the gut

• Transmitted among humans

EHEC

• Enterohemorrhagic e. coli

• Shiga toxin producing

• Hemorrhagic syndrome and kidney damage

ETEC

• Enterotoxigenic e. coli

• Severe diarrhea due to heat labile toxin and heat stable toxin

• Stimulates secretion and fluid loss

EIEC

• Enteroinvasive e. coli

• Inflammatory disease of the large intestine

EPEC

• Enteropathogenic e. coli

• Linked to wasting from infantile diarrhea

EAEC

• Enteroaggregative e. coli

• Common cause of pediatric diarrhea

DAEC

• Diffusely adherent e. coli

• Minor cause of pediatric diarrhea

O157:H7

• Somatic O type 157 and flagellar H type 7

• Enterohemorrhagic strain

• Virulence from cell wall receptor fusing with host cell membrane, creating a direct port for bacterial toxin secretion

• Toxin enters the host cell, binds ribosomes, and disrupts protein synthesis = death

• Shiga toxin producing

Hemolytic uremic syndrome

• Severe from of e. coli

• Caused by O157:H7

• Kidney damage and failure

Klebsiella pneumoniae

• Normal inhabitant of the respiratory tract

• Large capsule

• Causes nosocomial pneumonia

• Meningitis

• Bacteremia

• Wound infections

• UTI

Serratia marcescens

• Produces red pigment

• Causes pneumonia, burn wound infections, septicemia, and meningitis

Salmonella enterica

• Species of salmonella divided into 6 subspecies

  • Enterica

  • Salamae

  • Arizonae

  • Diarizonae

  • Houtenae

  • Indica

• Flagellated

• Resistant to chemicals

Salmonella serotype typhi

Causes typhoid fever

Typhoid fever

• Caused by salmonella serotype typhi; 1,000-10,000 bacilli

• Bacillus enters with food and water contaminated with faces

• Asymptomatic carriers ; chronic carriers shed bacilli from their gallbladder

• Bacilli adhere to the small intestine, causing invasive diarrhea that leads to septicemia

• Treated with ciprofloxacin or ceftriazone

Shigellosis

• Common incapacitating dysentery

• Caused by shigella dysenteriae and shigella sonnei

• Causes fever, nausea, painful abdominal cramps, and frequent defecation of watery stool filled with mucus and blood

• Invades the villus of the large intestine but does not perforate or invade the blood

• Treated with fluids, ciprofloxacin and sulfatrimethoprim

Endo and exo toxins of shigellosis

• Enters peyer’s patches

• Instigates inflammatory response

Yersinia pestis

• A nonenteric bacteria

• Tiny, gram negative rod that has unusual bipolar staining and capsules

Virulence factors of yersinia pestis

• Capsular and envelope proteins protect against phagocytosis and foster intracellular growth

• Coagulase

• Endotoxin

• Murine toxin (rodent transmitted)

Plague

• Caused by yersinia pestis (3-50 bacilli)

• Develops through contact with wild animals (sylvatic), domestic or semi-domestic animals (urban), or infected humans

• Fleas are vectors

  • Bacteria replicates in the gut

  • Coagulase causes clotting that blocks the esophagus

  • Flea becomes ravenous

Bubonic plague

• Yersinia pestis

• Direct bite from flea

• Bacillus multiplies in flea bite, enters the lymph

• Causes necrosis and swelling of lymph nodes in the groin or axilla

Septicemic plague

• Yersinia pestis

• Enters the blood stream

• Progression to massive bacterial growth

• Virulence factors cause intravascular coagulation, subcutaneous hemorrhage, and purpura

• Black plague

Pneumonic plague

• Yersinia pestis

• Transmitted via respiratory

• Infection localized to the lungs, highly contagious

• Fatal without treatment

Haemophilus influenzae

• Species of pasteurella (zoonotic)

• Tiny, gram negative pleomorphic rods

• Fastidious, sensitive to drying, temperature extremes, and disinfectants

• Causes acute bacterial meningitis, epiglottitis, otitis media, sinusitis, pneumonia, and bronchitis

Haemophilius influenzae subtype aegyptius

• Primary causitive agent of communicable conjunctivitis

• Pink eye

Haemophilus ducreyi

• Species of pasteurella (zoonotic)

• Tiny, gram negative pleomorphic rods

• Fastidious, sensitive to drying, temperature extremes, and disinfectants

• Causative agent of chancroid STD