Lecture 11: chronobacter

Question 1

Chronobacter is a gram ___, ___, ____ bacteria

Answer 1

negative, non spore forming, straight, rod shape bacteria

Question 2

the group most vulnerable-at risk for chronobacter infection is

Answer 2

immunocompromised and neonates younger than 28 days old, also low birth weight neonates

Question 3

what makes premature neonates more susceptible to chronobacter?

Answer 3

secrete less gastric acid than older infants and this may be important in the long term survival of chronobacter

Question 4

incidence of disease is very (high/low) for chronobacter

Answer 4

low

Question 5

cronobacter infection may cause severe ___ &____ in survivors

Answer 5

neurological and developmental disorders

Question 6

infected infants suffer from

Answer 6

1. necrotizing enterocolitis
2. septicaemia
3. meningitis

Question 7

neurological sequelae are common and include

Answer 7

1. brain abscess
2. necrosis of brain tissue
3. liquefaction of white cerebral matter

Question 8

foods found to harbour chronobacter include;

Answer 8

milk powder, cheese, herbs, spices and rice

Question 9

chronobacter has also been reported from clinical sources, including cerebrospinal fluid, blood, intestinal and respiratory tracts, bone marrow and skin wounds.

Answer 9

cerebrospinal fluid, blood, intestinal and respiratory tracts, bone marrow and skin wounds

Question 10

T or F: current processing technology is unable to completely eliminate the potential for microbial contamination without affecting organoleptic and nutritional requirements

Answer 10

True

Question 11

why is the elimination of chronobacter in PIF very hard

Answer 11

PIF is highly regulated in terms of nutritional requirements and based on our current knowledge sterilization of PIF seems to only be possible using irradiation. However, the doses required to kill all cronobacter are not feasible due to organoleptic deterioration.

Question 12

explain the process of cronobacter pathogenesis in terms of manufacturer, infant, and organism

Answer 12

1. the organism survives on the equipment, may survive via biofilm formation and improper temp in facility/storage areas.
2. infants who then have a high stomach pH, low GI microbiome complexity and may also be immunocompromised allow for a suitable growth environment for chrono.
3. the organism can then cross the blood brain barrier, OmpA facilitates invasion of brain cells and the enterotoxins produced can also cross the GI barrier.

Question 13

name the 4 ways in which crono may cause virulence

Answer 13

1. apical attachment
2. apical invasion
3. basolateral invasion
4. disruption of tight and adherens junction.

Question 14

name 9 virulence factors associated with crono

Answer 14

1. outer membrane proteins
2. enterotoxin
3. outer membrane protease
4. stalic acid utilization
5. iron aquisition system
6. efflux system
7. proteolytic enzymes
8. lipopolysaccharides
9. type 3 hemolysin

Question 15

which virulence factor is of greatest interest and why?

Answer 15

• the outer membrane proteins because of their cell surface exposure and contribution in export of extracellular virulence factors and in anchoring the structures that mediate adhesion and motility.
• OmpA helps cells adhere to GI epithelial cells.
• only OmpA positive Cronobacter breech the blood brain barrier.
• OmpX helps invasion on the apical side of GI epithelial cells, but also helps crono survive on the basolateral side as well.

Question 16

what does cpa stand for

Answer 16

presence of a plasmid (pESA3) encoding an outer membrane proteases (cpa)

Question 17

what is special about cpa

Answer 17

This protease has an ability to render serum resistance by cleaving complement components, activating plasminogen and inactivating a plasmin inhibitor.

Question 18

the pESA3 also encodes….

Answer 18

a type 6 secretion system and some adhesion factors

Question 19

sialic acid is found in ____ in the form of ___

Answer 19

human milk and infant formulae in the form of sialyloligosaccharides

Question 20

the intestinal microvilli of neonates contain (increased/decreased) levels of sialic acid

Answer 20

increased

Question 21

T or F: is plausible that there is a linkage between sialic acid metabolism and the pathogenicity of C. sakazakii as it is the only Cronobacter species possessing the nanAKT gene cluster encoding for sialic acid utilization

Answer 21

True

Question 22

how may cronobacter be prevented

Answer 22

1. refrigerate prepared infant formula to 4 deg C within 1 hour of prep
2. prepare only small volumes of IF to reduce the “hang time” at room temp before consumption. the hang time should never exceed 4 hours.
3. use only chilled, sterile water for IF preparation.
4. discard any IF remaining in the bottle after feeding
5. use the PIF within 4 weeks of opening
6. sterilize bottles.

Question 23

what are the strains of cronobacter associated with neonatal infection?

Answer 23

C sakazakii, C turicensis and C malonaticus.

Question 24

why are cronobacter infections under reported?

Answer 24

due to being diagnosed as SIDs

Question 25

what is critical in the pathogenesis of cronobacter?

Answer 25

the outer membrane proteins

Question 26

mortality rates associated with crono infection are very ___ and even survivors will likely have ___

Answer 26

high, permanent brain damage