Lecture 8 - Gram Negative bacteria 1 Flashcards
What are the classes of gram negative bacteriaceae?
Enterobacteriaceae
Nonfermentative gram negative rods
Oxidase positive fermenters
Miscellaneous, fastidious gram negative rods
Campylobacter and helicobacter
Legionella
Haemophilus
Gram negative coccobacilli
What are the morphologies that can be found in gram negative bacteria?
Bacilli (enterobacteriaceae)
Cocci, diplococci
Coccobacilli
Fusiform (typically anaerobes)
How are enterobaceae arranged?
In tribes
Are enterobacteriaceae pathogenic?
Many are commensals but some are not.
Some are very common pathogens others are pathogenic in certain clinical settings
What are the 3 biochemical characteristics shared by all enterobacteriaceae?
They utilize glucose fermentatively
They are negative in oxidase test
They reduce nitrate to nitrite
Where is escherichia normally found?
In the human bowel as a commensal
What diseases can E.coli do?
They are uropathogenic and are the most common cause of UTIs
Some strains are enteropathogenic causing diarrhoea
What are the strains of diarrhoea causing E.coli strains called?
Enterohaemorrhagic (EHEC)
Enteropathogenic (EPEC)
Enteroinvasive (EIEC)
Enteroaggregative (EaggEC)
Enterotoxigenic E.coli (ETEC)
What does shigella do?
Causes bacterial dysentery a severe form of diarrhoea in which stool contains blood and pus
What are the species of shigella?
Shigella dysenteriae
Shigella flexneri
Shigella boydii
Shigella sonnei
What are the species of salmonella?
Salmonella enterica
Salmonella bongori
How are salmonella differentiated?
> 2500 serotypes within species.
They are differentiated based on antigenic differences in cell envelope structures “O” and “H”
Where are the H antigenic differences located?
On the flagella
Where are the O antigenic differences located?
on the LPS
Why is salmonella that causes typhoid fever called salmonella typhi?
It is the serotype name that often is used instead of species name.
What is the actual name of salmonella typhi?
Salmonella enterica subsp. enterica, serovar typhi
What do the non-typhoidal serotypes do in humans?
Commensals of various animal species
Self-limiting diarrhoea
How long does salmonella fever take?
its a long term illness often taking close to a month.
What are the diseases caused by salmonella called?
typhoid and paratyphoid fever
What does salmonella do?
abdominal symptoms
diarrhoea
bacteria in blood
Can cause rupture in the bowel
May or may not be found in species
Found in blood
What are the important citrobacter species?
Citrobacter freundii
Citrobacter diversus
What are the diseases caused y citrobacter species?
UTIs
Infections such as pneumonia and neonatal meningitis
What are the klebsiella species?
Klebsiella pneumoniae
Klebsiella oxytoca
Klebsiella ozaenae
Klebsiella rhinoscleromatis
Klebsiella granulomatis
What does klebsiella pneumoniae do to people?
Necrotising pneumonia that is severe
Rapid in onset
creates sputum known as currant jelly
Who does klebsiella pneumoniae typically affect?
Causes disease in people who are debilitated, homeless, and alcoholic
What kind of pneumonia does klebsiella cause?
Lobar pneumonia
What are the types of infections caused by klebsiella oxytoca, ozaenae and pneumoniae?
Nosocomial infections such as UTIs Respiratory tract infections and surgical wound infections
What is a huge issue with klebsiella strains?
They are resistant to multiple antibiotics.
What disease does klebsiella granulomatis cause?
Sexually transmitted infection of the tropics
What is the sexually transmitted disease of the tropics called?
Donovanosis or granuloma inguinale
What are the types of donovanosis?
Starts as an ulcer on the genitals then becomes chronically disfiguring
A patient comes to you with an ulcer on his genitals and tells you he was in a tropical region. What is the reason for his symptoms and what is the condition called?
Klebsiella granulomatis and the disease is called donovanosis
What are the enterobacter species?
Enterobacter aerogenes
Enterobacter cloacae
What are members of the genus serratia?
Serratia marcescens
Serratia liquefaciens
What are the members of the genus morganella?
Morganella morganii
What are the members of the genus providencia?
Providencia stuartii
Providencia rettgeri
What are members of the genus Proteus ?
Proteus mirabilis
Proteus vulgaris
What disease are proteus mirabilis linked to?
Most common cause of UTIs after E.coli
What are enterobacteriaceae associated with?
Hospital infections
Debilitated patients
UTIs
Respiratory tract infections
Surgical wound infections
(caused by serratia, klebsiella, proteus, Morganella, providencia, and enterobacter)
Why are hospitals carriers of so many bacteria?
Due to multiple antibiotic resistance
What enterobacteriaceae does not cause hospital infections?
Yersinia
What kind of disease is caused by yersinia pestis?
The plague
What are the types of plague?
Bubonic plague
Pneumonic plague
Septicaemic plague
What is the untreated mortality rate of the plague?
50 - 90%
How many people were killed in Europe by the plague in the middle ages?
1/4 of Europe’s population in the middle ages
How often do people die from the plague today?
Its rare but does happen often in return travellers from areas like madagascar
What does yersinia enterocolitica do?
Mesenteric adenitis (affects lymph nodes in mysentery and mimics appendicitis)
Pseudoappendecitis
Enterocolitis (infection of colon)
What are the important non-fermentative gram negative rods?
Pseudomonas
Stenotrophomonas
Burkhoideria
Acinetobacter
What is interesting about pseudomonas aeruginosa?
It is a major pathogen
It is very resistant to antibiotics
How do pseudomonas look on a clear agar?
Green coloured
What condition does pseudomonas aeruginosa cause in the ear?
Otitis externa caused by inflammation as a result of inflammation due to narrow ear canal and prolonged pseudomonas
How does pseudomonas aeruginosa affect burn patients?
Colonises their skin and prolongs healing
How does pseudomonas aeruginosa affect urinary tract?
causes UTIs
What are all the conditions caused by pseudomonas aeruginosa?
Otitis externa
UTIs
Colonises skin of burn victims
Lung infection in people with cystic fibrosis
lung infection in patients that are mechanically ventilated
Septicaemia in those with leukaemia, organ transplants, and IV drugs
How does pseudomonas aeruginosa affect people in hospitals?
Exacerbates their condition
What does stenotrophomonas maltophilia cause?
Nosocomial infection in debilitated patients
Lower respiratory tract infections in debilitated patients and those with cystic fibrosis
Septicaemia in debilitated patients (especially neutropaenic cancer patients)
What does Burkholderia pseudomallei do?
Tropical infection melioidosis
Severe pneumonia
soft tissue abscesses
septicaemia (high fatality)
What countries typically contain Burkholderia?
in South east Asia and Nothern Australia
Where is Burkholderia typically found?
In soil, infects humans through contamination of abrasions or through inhalation
How does burkholderia pseudomallei deal with antibiotics?
It is very antibiotic resistant
Where is acinetobacter typically found?
In soil and aquatic environments
What part of the body does acinetobacter typically colonize?
Colonises human skin and respiratory tract
Are acinetobacter nosocomial infections
Yes but they are also opportunistic and resistant to multiple antibiotics
Who does acinetobacter baumannii typically affect?
Immunocompromised patients and it causes nosocomial infections, intravenous catheter related bacteraemia and UTI
What is acinetobacter baumannii infection associated with (lifestyle)?
Smoking and alcohol
What is acinetobacter baumannii infection associated with (conditions)?
Chronic obstructive pulmonary disease
Diabetes
What is acinetobacter lwoffi a cause of?
nosocomial infection in immunocompromised patients.
pneumonia
intravenous catheter related bacteraemia
UTI
What are the enterobacteriaceae that are common causes of urinary tract infections?
E.coli (most common cause of UTIs)
Klebsiella
Proteus (second most common cause after E.coli)
What are the enterobacteriaceae that are bacteria which inhabit hospitals?
Citrobacter (freundii and diversus)
Klebsiella
What are the enterobacteriaceae that are responsible for diarrhoeal illness?
E.Coli (4 strains cause diarrhoeal illness they are EHEC, ETEC, EIEC, EPEC, EaggEC)
Shigella
Salmonella
Yersinia enterocolitis
What are the enterobacteriaceae that are responsible for typhoid and paratyphoid fever?
Salmonella (Typhoidal serotypes:
• Salmonella Typhi (eg. S. enterica subsp. enterica, serovar Typhi
• Salmonella Paratyphi types A, B & C)
What are the enterobacteriaceae that are responsible for plague?
Yersinia pestis
What are the non-fermentative Gram negative rods that are responsible for nosocomial illness?
Pseudomonas aeruginosa
Stenotrophomonas maltophilia
Acinetobacter baumannii
Acinetobacter lwoffii
What are the non-fermentative Gram negative rods that are responsible for UTI illness?
Pseudomonas aeruginosa (generally hospital acquired rather than community acquired)
Acinetobacter baumannii
What are the non-fermentative Gram negative rods that exhibit antibiotic resistance?
Pseudomonas aeruginosa
Stenotrophomonas maltophilia
Burkholderia pseudomallei
Acinetobacter baumannii
What is the defining feature of gram negative rods?
They don’t metabolise glucose by fermentative pathways (or don’t utilize it at all)
What are the types of Vibrio?
Vibrio cholera species
Non-cholera vibrio species
What kind of disease do Vibrio cholerae produce?
Certain strains produce severe diarrhoeal illness
What is the fatality rate like in cholera?
High particularly in undernourished people and people ill with other illnesses
Which strains of vibrio cholera produce severe illness?
The strains that produce the cholera toxin
How is cholera acquired?
faecal oral contamination and often through water
What does cholera toxin do?
Enters enterocytes which control electrolyte and fluid balance of the body.
This results in an impairment of electrolyte and water regulation.
Result is very profuse dehydration is the result.
What is used to classify vibrio cholera?
The antigens of the cell wall
What serotype causes most epidemics/pandemics of cholera?
Type-01
What are the other types of Vibrio cholerae?
Non type-01
How many non type-01 serotypes are there?
139
What infections are vibrio alginolyticus typically seen in?
Skin and soft tissue infections following wounds in marine environments
Otitis externa in ear
What does vibrio parahaemolyticus cause?
gastroenteritis from contaminated seafood
What is the most virulent disease of the non-cholera vibrios?
Vibriovulnificus
What kind of illness does vibrio vulnificus cause?
Severe septicaemic illness in immunocompromised hosts
Severe cellulitis and skin necrosis after contamination of wounds with seawater
What are the important genera of oxidase positive fermenters?
Vibrio spp.
Aeromonas spp.
What are the important genera of oxidase positive fermenters?
Vibrio spp.
Aeromonas spp.
What are aeromonas?
genus of curved gram negative rods found in aquatic environments
Where do aeromonas live?
Aquatic environments and the gut of leeches
What kind of disease do aeromonas cause?
Aggressive skin and soft tissue infection complicating wounds in marine environments and following leech therapy
What are aeromonas species like?
vibrio alginiticus
Do aeromonas species and alginiticus species react to antibiotics?
Yes but they also spread really quickly
