Micro Lecture 23 - Enterobacter spp., Serratia marcescens, Bordetella pertussis, Haemophilus influenzae

Enterobacter spp. biochemical identification

-Oxidase negative

-Indole negative

-Catalase positive

-Citrate positive

-High levels of drug resistance – carbapenem-resistant Enterobacter or CRE

-cause of nosocomial infections

Serratia marcescens

-S. marcescens most common member of genus

-Environmental source (water, soil, plants, insects)

-Motile, often producing red pigment

Serratia marcescens virulence

-Extracellular enzymes (elastase, lecithinase, caseinase)
-LPS
-Biofilm formation
-Some incidence of drug resistance

Serratia marcescens disease

Often healthcare-associated infections with spread being on hands of hospital staff

Bordetella pertussis (Whooping cough)

-Causes severe cough in children

-Morphology and structure: Small rods. Aerobe, Non-motile, Fastidious (requires enriched medium)

Bordetella pertussis (Whooping cough) disease

-Transmitted by inhalation of aerosol and highly infectious

-Emerging disease!!

-Occurs in the vaccinated individuals when immunity wanes

Bordetella pertussis

-Whooping cough (pertussis)

Bordetella pertussis: Catarrhal stage

Mild upper respiratory tract infection, sneezing, slight cough, low fever, runny nose.

Bordetella pertussis: Paroxysmal stage

Lower respiratory tract. Severe cough (5 to 20 forced hacking coughs per 20 seconds).

Bordetella pertussis: Convalescent stage

Less severe but persistent cough.

Bordetella pertussis: adherence

-Filamentous Hemagglutinin (FHA), pertactin, and pili
-Allows bacterium to bind to ciliated respiratory epithelium
-Initiates phagocytosis by binding PMNs (survives intracellularly)

Bordetella pertussis: Pertussis Toxin

-An A/B toxin
-The active portion is ADP ribosyl transferase
-dysregulates cAMP -> increase cAMP and increase respiratory secretions and inhibiting neutrophil functioning

Haemophilus influenzae

-Small Gram-negative rod/coccobacillus; facultative anaerobe

-Transmission: aerosolized respiratory secretions

-Diagnosis: culture on chocolate agar and microscopic detection of bacteria in CSF

-Prevention: Vaccine

H. Influenzae Virulence Factors

-Required growth: chocolate agar

-Capsule

-Endotoxin

-IgA protease

-Pili and fimbriae

-LPS

-Colonization of nasopharynx

-Invasion of nasal mucosa

H. influenzae susceptibility factors

-Age – elderly and young children

-Immune status – patients with complement deficiency, asplenic patients

-Prior infection – esp. viral and otitis

Haemophilus influenzae Disease

-Epiglottitis

-Cherry-red epiglottis

-Life-threatening emergency!

-Begins as pharyngitis, fever, and difficulty breathing which can rapidly progress to airway obstruction and death → “thumb print sign”

Haemophilus influenzae: Meningitis

-Due to hematogenous spread of bacteria from nasopharynx to CNS
-With appropriate treatment, mortality is <10%

Haemophilus influenzae: Cellulitis

Fever and cellulitis which presents as reddish-blue patches on cheeks and periorbital areas

Haemophilus influenzae affect what population

Mostly pediatric, but adults are also susceptible

Haemophilus influenzae prevention and treatment

-We have a conjugated Hib vaccine reduced infections in children (<5 yr old) by >95%
-Cefpodoxime or ceftriaxone (for life-threatening infections) or amoxicillin-clavulanate

unique features of serratia marcescens

-produce red pigment
-often spread on hands of hospital staff

morphology of pertussis

small rods, aerobe
-non motile
-

Catarrhal stage of pertussis

mild URT, first stage

Paroxysmal stage of pertussis

LRT infection
-middle stage
-5-20 coughs per 20 secondss

convalescent stage of pertussis

less severe but persistent cough; final staage

pertussis virulence factors

-AB tooxin
-active portion is AADP ribosyl transferase
-dysregulates cAMP

how can you grow H. influenza on an agar?

chocolate agar supplemented with factors X and V

Epiglottitis

-disease of H. influenza
-cherry red epiglottis presentation, life threatening emergency!
-begins as pharyngitis, rapidly progresses to airway obstruction