BMSC207 Lecture Notes - Lecture 8: Metronidazole, Clindamycin, Endocarditis
Bacterial infections - GIT and airway:
The decline in infectious diseases, particularly in the younger age groups, was the
drivi ng force behind the decline in mortality in the first half of the 20th century.
•
In 1908 infectious diseases comprised approximately 25% of all deaths for both
and females; the death rate for males from infectious diseases was 300 per 100,000
persons, and for females 233.
•
In 1920 three of the leading causes of death for children under five years of age were
infectious diseases: diarrhoea & enteritis; diphtheria; and measles (United Nations
1982).
•
By 1998 infectious diseases comprised approximately 1% of all deaths.•
Causes of decreased death from infectious diseases:
Antibiotics, anti-malarials•
Water and sewage management○
Public works•
Better nutrition•
Better hygiene in homes, schools, hospitals•
Less crowded living standards•
Separation of animals and people •
Bacterial infections - GIT:
Major issue is infectious diarrheal diseases•
If general sanitation is low○
Epidemics of bacterial gastroenteritis○
High morbidity & mortality among infants, children and elderly○
Common cli ni cal manifestations of bacterial gastrointestinal infections are
diarrhoea, vomiting, abdominal pain and fever
○
Causes:•
Bacterial intestinal infection via water/food contamination
○
Incubation period 8-24 hrs○
Rarely involve other organs and systems○
Recovery in 2 days○
Small and la rge intestine
Watery diarrhoea:○
Dysentery - mostly large intestine
Bloody diarrhoea:○
Both small and large intestines, watery bloody diarrhoea (both bacteria
toxin in pathogenesis)
Enterocolitis inflammation:○
General features:•
.
○
Prevention:•
Diarrhoea organism tests:•
Typhoid fever
Typhoid fever is a severe multi-systemic illness•
Salmonella invade & multiply within intestinal mucosa•
Peyer patches: enter intestinal lymphoid follicles•
Macrophages carry cells to reticuloendothelial system causing lymphoid
hypertrophy
•
Death rates by selected years and age groups
Salmonella group:
Gram-negative bacilli, Facultative anaerobes○
Only one major species of Salmonella: S. Enterica○
Numerous serovars (serotypes) - Approximately 2000 types○
Salmonellae group:•
O (cell wall)○
H (flagellar)○
Vi (virulence)○
Serovars classified by specific set of antigens:•
Human salmonellosis:
Enteric Fever Salmonellas (Typhoid fever)•
Enterica subtype Typhi & Paratyhi A, B, C○
Infect only humans caused by:•
Cause severe human systemic diseases•
GIT invasion via contaminated water•
Less commonly via fresh food•
Rarely by direct contact•
Incubation period of 1-3 weeks•
Lecture 4.1 - 22/8/16
Monday, 22 August 2016
10:48 AM
Lectures Page 1
hypertrophy
Later spread to blood, liver and other internal organs•
Characterized by prolonged high fever and headache, malaise•
Liver & spleen enlargement•
Skin rash (Rose spots)•
Mostly watery- bloody diarrhoea•
Proteinous capsule (S. typhi VI antigen), cell wall lipopolysaccharides, release
specific cytotoxin
○
Pathogenicity - virulence factor:•
Following necrosis of liver, spleen, gallbladder○
Salmonella re-enter intestinal tract○
Causing severe intestinal inflammation
○
Bloody diarrhoea, enterocolitis and intestinal ○
perforation
Approx. 10-30% of those affected might die if ○
antibiotic treatment not used
Typhoid fever: has been associated with meningitis○
Mostly in chil dren and the immunocompromised○
Rare complications incl ude pneumonia, endocarditis,
○
osteomyelitis, septic arthri tis and hepatic abscesses
Salmonella - typhoid fever:•
Approx. 5% of those infected become carriers○
Occurs more in females than males
○
Infection becomes chronic○
Bacteria remains in the gallbla dder and to a lesser degree in Peyer patches○
Execrate bacteria excreted in faeces○
Healthy carriers maintai n cycle of Typhoid disease in the community○
Host response to infection is production of specific antibodies (Anti-O &
○
These antibodies may prevent severe complications and death in the host○
Typhoid Fever - Carriers:•
Antibiotics if clinical evidence of infection
○
Ciprofloxacin 4 weeks○
Ceftriaxone for pregnant women and children○
Chloramphenicol & Amoxicillin, Augmentin is currently less used due to ○
Fatality is high without antibiotic treatment○
Safe drinking water, proper sewage disposal
Public health measures:○
Detection of human carriers○
Education programs on food hygiene
○
Oral live attenuated Typhoid vaccine○
Injectable vi
-
capsular polysaccharide vaccine is used for short protection
(military personnel in endemic regions)
○
Treatment and prevention:•
Toxigenic bacteria:
Produce several heat-stable protein exotoxins○
Transmission via ungloved hands○
Absorbed rapidly by GIT and affects CNS (vomiting centre)○
Food poisoning commonly associated with food not kept at correct
(chicken) (think of Nudgee school gravy example)
○
Resistant to salt -
pickles and salted meats foods, dairy products, milk formula
○
30 minutes-6 hours following consumption of food
Vomiting, nausea, stomach cramps
Rarely watery diarrhoea
No fever and recovery within 1-2 days
Self-limited – but danger of dehydration
Symptoms:○
Staphylococcus aureus:•
Toxigenic bacteria
Bacillus cereus:
G+ve aerobic spore-forming Bacilli•
Common in soil•
Spores survive boiling and cooling/refrigeration of food•
Chinese food○
Spores survive steaming/frying•
Germinate when food reheated•
Various exotoxins/ enterotoxins produced during sporulation
•
Lectures Page 2
Document Summary
Death rates by selected years and age groups. The decline in infectious diseases, particularly in the younger age groups, was the driving force behind the decline in mortality in the first half of the 20th century. In 1908 infectious diseases comprised approximately 25% of all deaths for both and females; the death rate for males from infectious diseases was 300 per 100,000 persons, and for females 233. In 1920 three of the leading causes of death for children under five years of age were infectious diseases: diarrhoea & enteritis; diphtheria; and measles (united nations. By 1998 infectious diseases comprised approximately 1% of al l deaths. High morbidity & mortality among infants, children and elderly. Common clini cal manifestations of bacterial gastrointestinal infections are diarrhoea, vomiting, abdominal pain and fever. Both small and large intestines, watery bloody diarrhoea (both bacteria toxin in pathogenesis) Only one major species of salmonella: s. enterica. Serovars clas sified by specific set of antigens:
