Gram (-) Bacteria Flashcards by Deleted Deleted

Virulence factor of H. Influenzae

Polysaccharide capsule (type B)

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H. influenza requires what factors for growth on CAP

Factor X [hemin] and V [NAD]

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Habitat &reservoir of H. influenzae

URT
Human nasopharynx

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Pathogenesis of H. influenzae requires which enzymes

-Type b [polyribitol phosphate]
-IgA Protease

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H. influenzae affects what age group

6 months to 1 year

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Most common disease caused by H. influenzae
-sign?
-demographics?

Epiglottitis
■ Thumb sign
■ Most especially to UNVACCINATED children

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Tx for H. influenzae infection

Ceftriaxone

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Prevention of H. influenzae infection?
-given when?

HiB Vaccine containing the type b capsular
polysaccharide conjugated to dipheroid toxoid
○ Given between 2 and 18 months of age

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STD, Encapsulated, pleomorphic rods
-causes what disease?

-Haemophilus ducreyi
● Chancroid (genital ulcers)

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Small gram negative rods, strictly aerobe
-Cultured on?

Bordetella pertussis
-Bordet-Gengou Media or Regan-Lowe Charcoal

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Habitat & transmission of B. pertussis

Upper respiratory tract
-respiratory droplet

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Pathogenesis of B. pertussis?

○ Filamentous hemagglutinin
■ Mediates attachment

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Causes ADP-ribosylation
■ Activates G protein 3
■ Extracytoplasmic [false] adenylate cyclase - moa??

Pertussis toxin
-inhibit phagocytosis

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Damages ciliated cells → causes whooping
cough

Tracheal cytotoxin

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➔ It is a very contagious respiratory disease
➔ It is characterized as a severe hacking cough followed by a high pitched sound

Whooping Cough

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➔ Paroxysmal pattern of hacking coughs accompanied by production of copious amounts of mucus that end with an
inspiratory “whoop”

➔ S/sx
◆ Difficulty of Breathing
◆ Vomiting
◆ Dehydration

➔ Incubation Period: ?

Pertussis or Tuspirina
-7-10 days

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Phase of pertussis that
○ lasts for 1-2 weeks
○ s/sx: rhinorrhea, malaise, fever, sneezing (contagious), anorexia
○ Mngt: ??

Catarrhal stage
-antibiotics

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Phase of pertussis that
○ lasts for 2-4 weeks
○ “??” → bursts of non-productive coughs
○ Increased number of ?? in blood smear
○ Note: Antibiotics is ?? during this stage

Paroxysmal stage
-whoops
-lymphocytes
-ineffective

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Phase of pertussis that
○ lasts for 3 to 4 weeks [or longer]
○ Diminished paroxysmal cough
○ Development of secondary complications
■ ??, Seizure, ??

Convalescence stage
-pneumonia, encephalopathy

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Treatment for B. pertussis

Erythromycin

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Prevention of B. pertussis

Acellular vaccine in combination with diphtheria and tetanus toxoids [DTaP]

Poorly / Weakly gram negative rods
● Facultative intracellular pathogen

● Habitat:
○ ?? in man and natural water environment
○ Freshwater amoebae → natural reservoir

● Transmission:
aerosols from ??
○ no human to human transmission

Legionella pneumophila
-ubiquitous
-airconditioning systems

Pathogenesis of L. pneumophila:

○ Endotoxin: ??
● Protect the bacteria from
macrophage superoxide and
hydroperoxide oxidative burst

○ ??
■ Promote attachment and invasion

○ RNAse, Phospholipase A and Phospholipase C

○ Organism replicate intracellularly
■ Inhibits ??

Cu-Zn superoxide dismutase and
Catalase peroxidase
-pili and flagella
-phagolysosomal fusion

Predisposing factors for L. pneumophila

○ Smokers
○ >55 yrs old
○ High alcohol intake
○ immunocompromised/ immunosuppression

Diagnostics for L. pneumophila: ○ Visualized using ?? ○ Culture on ?? ■ Fastidious, require iron & cysteine ○ Organisms are dormant ?? and are killed at temperatures ?? ○ ?? Test: ■ can be detected by RIA with high sensitivity and specificity and will remain positive for months after infection

Silver stain - Charcoal Yeast Extract Agar -<20C, >60C -Rapid Urinary Antigen test

Diseases caused by L. pneumophila: ?? ■ Pneumonia + Confusion + Non-bloody diarrhea + Hyponatremia ■ Urinalysis: Proteinuria and Hematuria ?? ■ Pneumonitis ■ Mild, flu-like illness

Legionnaires' disease (atypical pneumonia) Pontiac fever

Treatment for L. pneumophila

Fluoroquinolones OR Macrolides: Azithromycin, Erythromycin

● Gram negative rods, in singly ○ Large, heterogeneous group of gram-negative rods whose natural habitat is the ?? of humans and animals ● All are ??? ● Most of them are Motile → they have a ?? ○ motile enterobacteriaea?? Can grow on ordinary culture media ○ They are not ?? [i.e. not difficult to grow] ● Ferment ?? ● Catalase ??, Oxidase ??

Enterobacteriacaea/coliforms -intestinal tract -Facultative anaerobes -peritrichous flagella -Klebsiella, Shigella, Yersina [KeYS] -fastidious -glucose -cat +, oxidase -

Oxidase (+) gram negative bacilli/rods like ??

V. cholera and Campylobacter

Enterobacteriacaea antigen ■ the most external part of the cell wall lipopolysaccharide ■ consist of repeating units of polysaccharide ■ resistant to heat and alcohol and usually are detected by ?? ■ predominantly ??

O: cell envelope -bacterial agglutination -IgM

Enterobacteriacaea antigen ■ located on flagella ■ denatured or removed by heat or alcohol ■ agglutinate with ?? antibodies, mainly ??

H: flagellar -anti-H -IgG

Enterobacteriacaea antigen ■ external to O antigens on some but not all Enterobacteriaceae ■ may be associated with virulence: ● E coli strains producing ?? antigens are prominent in ?? ● ?? antigens of E coli cause attachment of the bacteria to epithelial cells before GI or UT invasion

K: capsular polysaccharide -K1 -neonatal meningitis

Enterobacteriacaea antigen of Salmonella

Vi: capsular antigen

Enterobacteriacaea that are LF

Citrobacter Escherichia Enterobacter Klebsiella

Enterobacteriacaea that are NLF

Shigella Yersinia Proteus Salmonella

Facultative anaerobe -LF -Iridescent green sheen on EMB “??” -+/- capsule

Escherichia coli -greenish metallic sheen on EMB

Habitat of E. coli ● Transmission of E. coli ○ most common ?? ○ During birth in ?? ○ ?? in cases of diarrhea

Human colon (also vagina, urethra) -Ascending infection in UTI -neonatal meningitis -Fecal oral route

Virulence Factors of E. coli: 1. ?? ■ Attachment, colonization factor associated with UTI 2. ?? 3. ?? ■ Associated with pneumonia and neonatal meningitis 4. ?? 5. Enterotoxins ■ ?? → activates the enzyme guanylate cyclase ■ ?? → activates the enzyme adenylate cyclase ■ These events in turn cause watery diarrhea → increasing the activity of ?? [similar to the mechanism of Cholera toxin] 6. ?? ■ Bloody diarrhea [??] ■ Inhibits protein synthesis by inactivating the 60S Subunit of Eukaryotic cells ■ E.coli O157:H7, STEC, EHEC

-Pili or fimbriae -Flagellum [H] -Capsule [K] -Endotoxin [O] -ST [Stable Toxins A and B] -LT [Labile Toxins I and II] -cAMP -Verotoxin [Shiga-like toxin] -HUS

Diseases caused by E. coli: ○ ?? ■ Most common cause of community acquired __ ■ ?? (adherence to uroepithelium) ■ Treatment: ● ?? OR ● ?? ○ ?? ■ 2nd most common cause ■ capsule & endotoxin ■ Treatment: ● ?? for meningitis and sepsis ○ Diarrhea ■ ?? is effective in traveler’s diarrhea

Urinary Tract Infection -P-pili -Ampicillin, Sulfonamides Neonatal septicemia & meningitis -3rd gen cephalosphorins Rehydration

E. coli strain Epidemiology: traveler's, children Clinical syndrome: ??

ETEC -watery diarrhea

E. coli strain Epidemiology: occ epidemics, children Clinical syndrome: ??

EIEC -dysentery

E. coli strain Epidemiology: infants in developing countries Clinical syndrome: ??

EPEC -watery diarrhea

E. coli strain Epidemiology: outbreaks in all ages Clinical syndrome: ??

EHEC -bloody diarrhea

E. coli strain Epidemiology: children Clinical syndrome: ??

EAEC DAEC -persistent diarrhea

Prevention of E. coli infection

○ Limiting urinary catheterization ○ Switching IV lines promptly ○ Drinking boiled water

Facultative gram-negative rods ● Habitat ○ Human colon only! [??] ○ Enteric tract of humans and animals, chickens and domestic livestock [??]

Salmonella -S. typhi and S. paratyphi -S. enteritidis

Salmonella infection induces carcinogenesis potentially through 4 paths namely: ★ The host is preconditioned by DNA damage caused by ?? factors (Western diet, obesity and physical inactivity) and ?? factors (tumor susceptibility) ★ Salmonella effector protein ?? stabilizes the expression of tight junction proteins (e.g., ZO-1) and decreases inflammation. ○ Meanwhile, Salmonella targets the “leaky protein” ?? to facilitate bacterial invasion. ○ The balance between protection and injury contributes to chronic infection and leads to sustained epithelial cell injury and DNA mutation. ★ Salmonella competes with indigenous microbiota for intestinal ??, thereby disrupting the gut microbiome and overcoming colonization resistance ★ ?? effectors enter epithelial cells and activate signaling pathways leading to chronic inflammation, host cell transformation, and carcinogenesis.

-epigenetic, genetic -AvrA, claudin-2 -epithelial attachment sites and nutrients -T3SS

Diagnosis of Salmonella ○ ??-fermenting ○ Produces ?? ○ ?? ■ Detects antibodies in patient’s serum ○ Cultured in ??

-Non lactose -H2S -Widal Test -XLD medium

○ Most common form → due to animal acquired salmonella ○ Most common serotype: ?? ○ Incubation period: 8-48 hours ○ S/sx: ■ Nausea, Vomiting ■ Headache ■ ?? diarrhea ○ Often self-limited ○ Mngt: ■ Give fluid and electrolyte replacement ■ Not required to give antibiotics ■ Infection limited to the gut → infective dose is ??

Gastroenteritis / Enterocolitis or Salmonellosis -Typhimurium -Profuse non bloody -10^5

Clinical symptoms and excretion of salmonellae may be ?? by antimicrobial therapy

prolonged

○ Typhoid and Paratyphoid fever ○ Typhoid caused by Salmonella typhi ○ Paratyphoid ■ Salmonella Paratyphi A ■ Salmonella ?? ● Formerly Paratyphi B ■ Salmonella ?? ● Formerly Paratyphi C ■ ?? is milder than Typhoid

Enteric fever -Schottmuelleri -Hirschfeldii -Parathyroid