Gram Negative Rods II Flashcards
Yersinia grow at
4 degrees celcius
Penetrate intestine via M cells and multiply inside phagocytic vacuole, spread throughout body
Typhoidal Salmonella
Typhoidal Salmonella does not cause
Macrophage apoptosis
The capsule of Typhoidal Salmonella is the
Virulence antigen
Can establish chronic carrier state in gall bladder [scars, stones pre-dispose]
Typhoidal Salmonella
The gallbladder carrier can then shed Salmonella for years and
Infect others
Urinary Tract Infections [UTI], Septicemia and Meningitis, Nosocomial [Hospital-Acquired] Infections, and Opportunistic Infections are all examples of
Extra-intestinal infections
Causes >80% of uncomplicated UTIs
E. coli
Urinary tract infections can lead to infection of the bladder, which is called
Cystitis
P-fimbrae –bacteria adhere to UT epithelium and can cause
Pyelonephritis
What are the three characteristic symptoms of UTIs?
Urgency, Frequency, and Dysuria
Causes neonatal infections of sepsis and meningitis
E. coli K1
Adhere to endothelium, choroid plexus
S fimbrae
Polymer of sialic acid
-not immunogenic and resembles the host
K1 capsule
The K1 capsule does not activate
Compliment
Patients rapidly colonized by hospital flora
-More frequently antibiotic-resistant than community-acquired isolates
Nosocomial Infections
What are three nonsocomial pathogens?
Enterobacter spp, Klebsiella spp, Serratia
Multiple antibiotic resistance mechanisms (ESBL, carbapenemases, etc)
Enterobacter spp.
Multiple antibiotic resistance mechanisms (ESBL, carbapenemases, etc)
Klebsiella spp.
Highly encapsulated organisms that can cause necrotizing pneumonia
Klebsiella spp.
Have a bloody “currant jelly” sputum
Klebsiella spp.
Colonies with red pigment, often multi-drug resistant
Serratia
Haemophilus, Bordetella, and Legionella are all
Respiratory pathogens
Brucella, pasteurella, francisella, and yersinia are all
Zoonotic bacteria
An opportunistic Gram negative Rod is
Pseudomonas aeruignosa
Haemophilus influenzae has special growth requirements and requires
NAD and hemin, and chocolate agar
Slender, pleiomorphic Gram negative rods
Haemophilus influenzae
Only colonizes/infects humans
-Common in upper respiratory tract (unencapsulated)
Haemophilus influenzae
What are the three virulence factors for Haemophilus influenzae
Capsule, IgA protease, and Iron acquisition mechanisms
Type b was most frequently encountered until the introduction of the “Hib” conjugate vaccine
Haemophilus influenzae capsule
In individuals, bacteria may spread locally from URT to middle ear, sinuses and lungs
Haemophilus influenzae
Haemophilus influenzae can result in a life threatening
URT infection (epiglottis)
Given to all children beginning at 2 mos of age
Hib conjugate vaccine
25% of H. influenzae produce
-as a result are resistant to ampicillin
B-lactamase
Essentially all isolates of Haemophilus influenzae
are susceptible to
3rd generation cephalosporins
Has a school of fish Gram stain morphology
- Chancroid
- Affects penis
Haemophilus ducreyi
Only colonizes/infects humans
-Survives for only short periods in the environment
Bordetella pertussis
Seen as small colonies on blood agar
Bordetella pertussis
The best diagnostic method for Bordetella pertussis is
NAAT
Highly infectious, cold like prodrome, followed by period of paroxysms of coughing
Pertussis
The pertussis cough is also called the
Whooping cough
Spread by the respiratory route and has a 2 week incubation period
Pertussis
Bordetella pertussis Virulence factors are
Adhesins and Toxins
Promote attachment and prevent clearance by phagocytes
Bordatella pertussis Adhesins
Binds integrins on ciliated epithelial cells
Filamentous Hemagglutinin
Give Bordatella pertussis resistance to complement
BrkA protein
What are the three Bordatella pertussis toxins?
Tracheal toxin, adenylate cyclase toxin, and pertussis toxin
Stimulates IL-1 mediated killing of ciliated epithelial cells
Tracheal cytotoxin
Inhibits phagocyte function
Adenylate cyclase toxin
Has system effects such as lymphocytosis, sensitization to histamine and enhanced insulin secretion
Pertussis toxin
Due to concerns about reactogenicity, an acellular vaccine is currently used for
Bordatella pertussis (DTaP vaccine)
The aP component was rationally designed to include parts of proteins considered to be
Virulence factors
Causes respiratory infection in humans but unlike Haemophilus and Bordetella it is acquired from an environmental source
L. pneumophila
Serology later revealed a milder form of legionella pneumophila termed
Pontiac Fever
What are the growth requirements for Legionella pneumophila?
Highly fastidious and BCYE agar
Slender Gram negative rod
-Hard to see in stained sputum smears
Legionella pneumophila
We use a direct fluorescent antibody stain to test for
Legionella pneumophila
Helpful for Serotype 1 infection of Legionella pneumophila
Urine Ag test
Heavily colonizes warm bodies of water in the environment as well as potable sources
Legionella pneumophila
Legionella pneumophila multiplies in
Protozoan (amoebae) host and in macrophages
Legionella pneumophila multiplication in macrophages actively blocks
Phgosome/lysosome function
Usual source of exposure is aerosal from water supply
Legionella pneumophila
What is required to control growth of Legionella pneumophila?
Hyperchlorination and high heat
Pathogens transmitted from animals directly or by insect vector
Zoonoses
Small Gram-negative rods or coccobacilli
Zoonotic bacteria
Little or no human to human transmission
Zoonotic bacteria
Zoonotic bacteria multiply in
Phgocytes
Small Gram-negative coccobacillus
-Source: Livestock, unpasteurized dairy
Brucella spp.
Poses a significant threat to laboratory workers
-Can cause systemic febrile illness
Brucella spp.
Small Gram-negative coccobacillus
-Normal oral flora of domestic animals (cats and dogs)
Pasteurella multocida
In rabbits, Pasteurella multocida causes the
Snuffles
Pasteurella multocida infection is associated with
Animal bites
Rapidly progressive soft tissue infection
Pasteurella multocida
Small Gram-negative coccobacillus
-Transmission from wild animals, especially rabbits, by direct contact or via an insect vector
Francisella tularensis
Highly infectious organism with low infectious dose required (~3 organisms)
Francisella tularensis
Most labs lack facilities for culture, diagnosis based on serology or NAAT at special labs
Francisella tularensis
What are the 4 points of entry for Francisella tularensis disease?
Ulceroglandular, oculoglandular, oral or pharyngeal, respiratory infection
Ulcer at site of inoculation
–Lymphadenopathy
–Most common
Ulceroglandular entry
Eye is site of inoculation
–Lymphadenopathy
Oculoglandular entry
The cause of the bubonic plague
-Transmitted from rodents to human by flea bite
Yersinia pestis
Enter human host through flea bite wound
Yersinia pestis
Multiplies in lymph nodes which become enlarged (buboes)
Yersinia pestis
After it infects the lymph nodes, the Yersinia pestis bacteria is then spread to the
Blood, lung, and meninges
Lung involvement can lead to human to human transmission, This is then classified as the
Pneumonic plague
Diagnosis made by NAAT and/or culture in specially equipped laboratory
-Grows on a variety of media
Yersinia pestis
An opportunistic pathogen that is ubiquitous in the environment
Pseudomonas Aeruginosa
Has multiple mechanisms of antimicrobial resistance
Pseudomonas Aeruginosa
Gram-negative rod, polar flagella
Pseudomonas aeruginosa
Pseudomonas aeruginosa
creates no acids from sugars on test media. This it is an
Obligate oxidizer
Many Pseudomonas aeruginosa isolates produce
Siderophores (pyoverdin)
Community acquired infections in immunocompetent people
P. aeruginosa Disease
Also results in nosocomial infections and cystic fibrosis
P. aeruginosa Disease
Burkholderia spp. Stenotrophamonas maltophila, and Acinetobacte are other examples of
Gram negative Rods
