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Flashcards in Emerging diseases Deck (23):
1

C. difficile: Bacteriology and Pathogenesis

• Ingested spores survive gastric acid barrier and germinate in the colon

• Associated with acid-reducing agents

• Colonization occurs after alteration of normal

intestinal microbiota, usually by antibiotics

• 1/3 to 2/3 of colonized patients develop clinical

symptoms

2

Bacillus spp. characteristics 

 Aerobic Gram-positive, large rods

• Spore forming

• Predominantly found in soil

• Can be contaminants in laboratory cultures but can also cause infection in compromised hosts

• B.cereus group includes Sub-sp B.cereus, B.thuringiensis, B.anthracis.

2

Necrotising Soft Tissue Infections pathogens

• Group A strep is principal cause

• Klebsiella spp.

• Clostridium perfringens

• E. coli

• Staphylococcus aureus

3

Noroviral acute gastroenteritis timeline 

• Incubation period 24- 48h

• Infectious period – 4h before symptoms to

48h after resolution of symptoms

3

Noroviral acute gastroenteritis sx

• Clinical features: nausea, abdominal pain, vomiting ( projectile), watery diarrhoea, fever, myalgia, headache..

• Sometimes just nausea and ? indigestion,

sometimes only diarrhoea, and sometimes

no symptoms but still infected (asymptomatic infection)

4

Chikungunya Virus: Epidemiology

• Humans and Primates are the reservoir

• Usually endemic in Africa, India, Fiji Islands, Mauritius and SE Asia

5

Chikungunya Virus: Diagnosis, prevention and control

• Diagnosis by virus isolation, RT-PCR and serology

• Prevention, No Vaccine is available, mosquito control

• Asprin is not recommended

5

C. difficile prevention

• Rational Anti-infective prescribing

• Reduced use of acid-reducing agents

• Commodes & the environment must be clean...

• Hand washing by staff

• Hands of patients can be the vector

• Food services including food from relatives

6

NDM-1 organism characteristics 

Gram-negative bacteria like Klebsiella

6

C.difficile tx

metronidazole or vancomycin

8

New Opportunities for Pathogens: Ecological Changes

A image thumb
9

What is NDM-1?

New Delhi metallo-ß-lactamase-1, or NDM-1 for short, is a gene carried by bacteria that makes the strain resistant to carbapenem antibiotics. 

10

C. difficile structure

Gram-positive, spore-forming anaerobic bacillus

12

Chikungunya Virus: Pathogenesis

• Incubation, 1-12 days (2-3 days common)

• Causes fever (400C/ 1040F), arthritis, Rashes (maculopapular or petechial) and encephalitis

• Counters type I(α andβ) INF by viral NS2 protein

13

BSE- vCJD characteristics 

Origin is scrapie infected sheep or by mutation in cattle

• Either way, animal concentrates fed to cattle triggered the outbreak of BSE

• BSE jumped the species barrier ( if from scrapie) and triggered vCJD

14

Chikungunya Virus characteristics 

Ss+ polarity RNA (Baltimore class IVb)

• Family: Togaviridae

– Genus: Alphavirus (Semliki Forest virus

complex

– Virus:Chikungunya virus

15

Norovirus another name

Norwalk

16

MERS-CoV: Epidemiology

4 groups;

– Alpha: Bats

– Beta: Bats

– Gamma: Birds

– Delta: Birds

18

MERS-CoV: Pathogenicity

• Infects bronchial epithelium

• Evades immune attack

• Antagonistic to INF

• Attaches to CD26 (DPP4) peptide expressed in the bronchial epithelium and the kidneys

19

Norovirus characteristics 

possess single-stranded positive sense RNA genomes.

• Now detected by nucleic acid amplification

21

MERS-CoV: Virus characteristics 

• Ss+ Polarity RNA (Baltimore class IV)

Possibly zoonotic in nature 

22

Hospital water-borne infections

• P. aeruginosa

• Enteric gram-negatives

• Legionella

23

Opportunities increasing emerging diseases 

–Changes in land use

–Rural to urban migration

–Internal displacement

–Globalization of people and goods, travel, international migration

–Medical technologies