Haemophilus influenzae and listeria monocytogenes

what does haemophilus influenzae require to grow?

preformed growth factors that are present in blood that are released from red blood cells upon heating, found in chocolate agar

why is haemophilus influenzae named that if it doesn’t cause the flu?

it was first isolated during the influenza pandemic of 1890 and mistakenly thought to be the cause of influenza

list some fun facts about listeria monocytogenes

common contaminant of meat, vegetables, fruit, and unpasteurized milk

it is pretty hardy

killed by adequate cooking

does not cause serious disease in most healthy people

what is the gram status of haemophilus influenzae?

gram negative

what is the shape of haemophilus influenzae?

small, rods/coccobacilli

what is the oxygen preference of haemophilus influenzae?

facultative anaerobes

what are the different strains of haemophilus influenzae?

encapsulated and non-encapsulated

encapsulated strains have 6 antigen serotypes (types a-f)

non-encapsulated strains are referred to as non-typeable

is it easy to grow haemophilus influenzae?

no, need special growth conditions

what can non-encapsulated haemophilus influenzae cause?

can spread locally to cause otitis media, sinusitis, and bronchitis/pneumonia but disseminated disease is uncommon with these strains

commonly colonizes the upper respiratory tract of almost all individuals within the first few months of life

is encapsulated haemophilus influenzae common in human microflora?

no, but it can be carried asymptomatically

how is encapsulate haemophilus influenzae spread?

direct contact with respiratory droplets

haemophilus influenzae type B (Hib)

exclusively a human pathogen (no animal reservoirs), most common cause of invasive disease, high risk groups include unimmunized individuals, especially in children under 4 and those with waning immunity

what are high risks groups that would have more severe disease when infected with haemophilus influenzae?

sickle cell disease, asplenia, HIV, complement deficiency, recipients of hematopoietic stem cell transplants, radiation therapy for cancer

asplenia

absence of a spleen

what damage can non-encapsulate haemophilus influenzae commonly cause?

otitis media, sinusitis, bronchitis, can cause invasive disease like pneumonia in at risk patients

what damage can encapsulated haemophilus influenzae (most commonly Hib) cause?

commonly associated with invasive disease like URT infections, meningitis, epiglottitis, pneumonia, bacteremia, septic arthritis

epiglottitis

swelling of the epiglottis, life threatening emergency

what are virulence factors that all strains of haemophilus influenzae possess?

pili and non-pilus adhesions- mediates colonization of oropharynx

LPS- acts as an endotoxin

outer membrane proteins- mediate attachment and promote colonization of the human respiratory tract

IgA protease- enables survival within respiratory epithelial cells

what is a virulence factor of encapsulate strains of haemophilus influenzae (like Hib)?

polyribitol phosphate (PRP) polysaccharide capsule, which is anti-phagocytic

what is the treatment for haemophilus influenzae?

anti-bacterial agents

how can you prevent haemophilus influenzae infections?

maternally transferred antibodies directed against PRP capsule stimulate phagocytosis and complement-mediated bactericidal activity, active immunization, purified capsular polysaccharide haemophilus influenzae type B PRP that is conjugated to diphtheria toxoid (carrier protein), or PRP vaccine, prophylaxis with anti-bacterial agents for close contacts of patients with Hib

who is the PRP vaccine recommended for?

all infants and vaccines/boosters for older persons depending on risk factors

Vaccines are currently available and recommended in the United States to prevent diseases caused by which organisms?

A. Haemophilus influenzae and Staphylococcus

agalactiae.

B. Streptococcus pyogenes and Chlamydia pneumoniae.

C. Treponema pallidum and Borrelia burgdorferi.

D. Corynebacterium diphtheriae and Neisseria

gonorrhoeae.

E. Haemophilus influenzae, type b and Bordetella

pertussis.

E. Haemophilus influenzae, type b and Bordetella pertussis.

and if on an exam one answer is just Haemophilus influenzae and the other is Haemophilus influenzae type B, type B is the better answer!

what is the gram status of listeria monocytogenes?

gram positive

what is the shape and grouping of listeria monocytogenes?

coccobacilli/short rods, often in pairs or short chains

what is the oxygen preference of listeria monocytogenes?

facultative anaerobe

where does listeria monocytogenes infect?

facultative intracellular pathogen- so intra and extracellular infection

what temperature range can listeria monocytogenes grow at?

1C to 45C

can survive at -20C (temperature in freezer)

where is listeria monocytogenes found?

ubiquitous in environment, including soil and animal feces, transient colonization of humans is common as 1-5% of people carry it asymptomatically in GI tract

how is listeria monocytogenes transmitted?

contaminated food, or can be transmitted during pregnancy to fetus transplacentally or to newborn perinatally

what groups of people are at higher risk for severe disease from listeria monocytogenes?

neonates, elderly (over 65), certain pregnancies, severely cell-mediated immunodeficient people

what damage can listeria monocytogenes cause?

listeriosis- ranges in severity and clinical presentation depending on the patient, healthy adults are usually asymptomatic, but ingestion of large inoculum can result in a febrile gastroenteritis

what damage can listeria monocytogenes cause in pregnant women?

non-specific flu-like illness, can lead to fetal death, premature birth, or neonatal disease (often meningitis)

what kind of damage can listeria monocytogenes cause in immunocompromised and elderly adults?

meningoencephalitis

what virulence factors are associated with listeria monocytogenes?

exotoxin- listeriolysin O which is activated by acidic pH inside the phagolysosome, is a pore forming exotoxin, and lyses phagolysosomes

phospholipase C enzyme which enables bacteria to escape into the cell cytoplasm

bacterial protein ActA which creates actin tails, helps in cell to cell spread

how can you treat listeria monocytogenes?

anti-bacterial agents

how can you prevent listeria monocytogenes?

wash raw fruits/vegetables, keep raw fruits/vegetables away from raw meat, clean anything that comes in contact with uncooked food, clean up spills on counters or in refrigerator, cook meat thoroughly, store foods properly in the fridge, do not drink unpasteurized milk

is there a vaccine for listeria monocytogenes?

no

Listeriosis is:

A. caused by an organism that can grow in food stored in the refrigerator.

B. fatal in nearly all cases.

C. caused by a Gram-negative bacterium that forms actin tails.

D. can be prevented in a newborn if the pregnant mother is vaccinated.

E. most commonly transmitted by refried rice.

A. caused by an organism that can grow in food stored in the refrigerator.