Microbiology, Parasitology & Entomology – Gram negative bacteria session
Read the complete lesson in an organized slide-by-slide format. This topic contains 42 learning sections from the source presentation.
LESSON CONTENTS — 42 SECTIONS
Learning Objectives
- Define gram negative bacteria
- List gram negative bacteria of medical importance
- Identify morphological appearance of gram negative bacteria of medical importance.
- Mention diseases caused by gram negative bacteria of medical importance
Identify specimens which can be collected to identify gram negative bacteria of medical importance
Explain techniques used to identify gram negative bacteria of medical importance
Identify drugs of choice of choice for treating diseases caused by gram negative bacteria of medical importance
Learning Objectives cont…
Definition of Gram Negative Bacteria
Gram negative bacteria: These are bacteria which appears red, after losing the colour of primary Stain and adapting the colour of a counter stain (dilute carbofuchsin or safranin, or neutral red) when stained by gram stain.
List of gram negative bacteria of medical importance
Neisseria gonorrhea,
Neisseria meningetidis,
Salmonella ssp,
Shigella spp,
Escherichia coli,
Haemophylus spp,
Brucella spp,
Yersinia pestis,
Vibrio cholera,
Bordetella spp
List of gram negative bacteria of medical importance cont…
Morphological appearance of gram negative bacteria of medical importance.
Gram-negative are bacteria which have a rod or bacillus, comma shape, and are also gram negative as a result of having a thin layer of peptidoglycan and an outer membrane. Due to their rod shape, bacilli can only be arranged in a few ways, in contrast to round cocci, which can have several different arrangements.
Characteristics of Gram Negative Cocci
Bean shaped cocci
The pathogenic are intracellular (they live inside the host cell normally
polymorphonuclear cells like macrophages)
Oxidase positive
Have pilli
Non motile
Non sporing
Slide 9
NEISSERIA GONORRHEA
Neisseria gonorrhoea, also known as gonococci, or gonococcus, is a species of Gram-negative coffee bean-shaped diplococci bacteria responsible for the sexually transmitted infection gonorrhea
Neisseria gonorrhea
Classification of Gram Negative Bacilli (rods) of Medical Importance
Those related to gastrointestinal tract
Examples, Escherichia coli, Salmonella species, Shigella species, Vibrio species (Enterobacteriaceae)
Those related to respiratory tract
Example, Haemophilus species
Related to Reticulo endothelial organs like liver and spleen
Example, Brucella species
•According to animals sources
According to animals sources
Those which are transmitted from animals to humans (zoonotic organisms)
Examples Brucella species and Yersinia species
Classification of Gram Negative Bacilli (rods) of Medical Importance
diseases caused by gram negative bacteria of medical importance
Gonorrhea
Conjuctivitis in infants (Conjuctivitis neonatorum)
Pelvic inflammatory disease (PID)
URTI Culture
Cholera
UTI
Sepsis
Neonatal Meningitis
Osteomyelitis
Enterocolitis
Septicemia
Food poisoning
Shigellosis
Plague
Neonatal Meningitis
diseases caused by gram negative bacteria of medical importance
Undulant fever
Pneumonia
Acute epiglottitis
Cellulitis Chancroid
Diarrhea
Typhoid fever
Meningitis
diseases caused by gram negative bacteria of medical importance
specimens which can be collected to identify gram negative bacteria of medical importance
HVS
Blood
Urethral discharge
Eye swab
Synovial (Joints) fluid
CSF
Rectal swab
Stool
Vomitus
Food sample
Urine
Sputum
Bubo aspirate
Nasal pharyngeal swabs
specimens which can be collected to identify gram negative bacteria of medical importance
techniques used to identify gram negative bacteria of medical importance
Gram staining
Culture
Serology
drugs of choice of choice for treating diseases caused by gram negative bacteria of medical importance
Ceftriaxone
Doxcycline
Ciprofloxacine
Azithromycin
Erythromycin
Penicillin G
Benzylpenicillin
Tetracycline
Nitrofurantoin
Amoxicillin
Cephalosporins
Gentamicin
Chloromphenical
Co-trimoxazole
Nalidixic acid
Streptomycin
drugs of choice of choice for treating diseases caused by gram negative bacteria of medical importance
Characteristics of vibrio cholera and Escherichia coli
V.Cholerae
Curved, comma shaped gram negative rod
Oxidase positive
Motile
Tolerant to alkaline environment
Grows rapidly in the ph range of 7.4 to 9.6
Facultative anaerobe
Vibrio Cholera
Characteristics of E.coli
Motile with or without capsule
Facultative anaerobe
Capable of growing at 44 degree centigrade
Lactose fermentors
E.coli
Vibrio and E. Ccaused, laboratory diagnosis and drug of choiceoli: diseases
Species
Diseases they Cause
Lab Diagnosis
Drug of Choice
cholerae
Cholera
Specimen
Rectal swab
Stool
Vomitus
Food sample
Technique
Culture
Serology
Tetracycline
Erythromycin
Doxycycline
coli
UTI
Sepsis
Neonatal Meningitis
Diarrhoea
Specimen
CSF
Blood
Urine
Stool
Techniques
Gram stain
Culture
Cotrimoxazole
Nitrofurantoin
Amoxicillin
Cephalosporins
Gentamicin
Characteristics of shigella and salmonella
Gram negative rods
Non spore forming
Capable of aerobic and anaerobic respiration
Salmonella Bacteria
Species
Diseases They
Cause
Lab Diagnosis
Drug of Choice
S.typhi
Capsulated
Non lactose
fermentor
Typhoid fever
Meningitis
Diarrhoea
diseases
Osteomyelitis
Specimens
Stool
Blood
Urine
Techniques
Gram stain
Culture
Serology ( widal
and rapid test)
Chloromphenical
Co-trimoxazole
Ciprofloxacin
S.paratyphi
Motile
Non lactose
fermentor
Produces
hydrogen
sulphide
(H2S)
Enterocollitis
Septicemia
Food poisoning
Specimens
Stool
Blood
Vomitus
Food remains
Techniques
Gram stain
Chloromphenical
Co-trimoxazole
Ciprofloxacin
Shigella Bacteria
Culture
Serology
boydii
dysenteriae
flexneri
sonnei
Non motile
Shigellosis
Specimens
Stool
Techniques
Gram stain
Culture
Co-trimoxazole
Nalidixic acid
Ciprofloxacin
Characteristics of Yersinia and Brucella
Genus yersinia
The genus yersinia includes species which are short, pleomorphic gram-negative rods that can exhibit bipolar staining.
Catalase-positive, oxidase-negative, and microaerophilic or facultatively anaerobic.
Most have animals as their natural hosts, but they can produce serious disease in humans.
Yersinia species of medical importance includes
yersinia pestis, cause of plague in human
yersinia pseudotuberculosis cause of disease which resembles tuberculosis
yersinia enterocolitica, important causes of human diarrhea diseases
Characteristics of Yersinia Pestis
Pestis is a gram-negative rod that exhibits striking bipolar staining with special stains giving its characteristic safety pin appearance.
not motile
grows as a facultative anaerobe on many bacteriologic media
growth is more rapid in media containing blood or tissue fluids and fastest at 30 °C
aerobic
oxidase positive
Morphological Appearance of Giemsa Stained Yersinia Pestis
Yersinia: Diseases They Cause, Laboratory Diagnosis and Drug of Choice
Species
Diseases they Cause
Lab Diagnosis
Drug of choice
pestis
Plague
Specimen
Blood
Sputum
Bubo aspirate
CSF
Techniques
Gram stain
Culture
Gentamicin
Streptomycin
Characteristics of Breucella Group
Gram negative rods
Intracellular
Aerobic
Oxidase positive
Non capsulated
Brucella Group: Diseases Caused, Laboratory Diagnosis and Drug of Choice
Species
Diseases they
Cause
Lab Diagnosis
Drug of Choice
abortus
Melitensis
suis
Undulant fever
Specimen
Blood
Pus
Technique
Serology
Gram staining
Culture
Doxycycline
Gentamicin
Streptomycin
Haemophilus Species [Haemophilus Influenza and Haemophilus Ducreyi]
General Characteristics
Small non motile gram negative coccobacillae (rods with round ends)
Aerobic
Capsulated
Brucella Group: Diseases they Cause, Laboratory Diagnosis and Drug of Choice
Species
Diseases They Cause
Lab Diagnosis
Drug of Choice
influenza
Meningitis in young
children under 5 years
Pneumonia
Acute epiglotitis
Cellulitis
Specimen
CSF
Nasal pharyngeal
swabs
Blood
Technique
Culture
Gram staining
Ceftriaxone
ducreyi
Chancroid
Specimen
Pus
Technique
Culture
Gram staining
Ceftriaxone
Co-trimoxazole
Doxycycline
Key Points
Gram negative bacteria lose the colour of primary stain and adapt the colour of secondary (Counter stain) stain.
There is a large group of gram negative bacteria but only some causes diseases to man, Including neisseria spp, haemophilus spp, vibrio. Gonorhoea, N.Meningitids, vibrio Cholera.
Most of these organisms are diagnosed by doing gram staining, culture, serological tests
Evaluation
What is the gram negative bacteria related to gastrointestinal tract?
Which specimen is collected in order to diagnose cholera?
What are the diseases caused by neisseria gonorrhoea?
References
- Becker, F.J. & Silverton, R.E. (1985). Introduction to medical laboratory technology (6th ed.) London: butterworth.
- Brooks, g.F., Butel, J.S., Morse, S.A. Et al, (2007). Medical microbiology (24th ed.). NewYork: mcgraw- hill.
- Cook, g. (2000). Manson’s tropical diseases (22nd ed.). London: wb saunders Company ltd.,
- Greenwood, d., Richard, C.B.S, & john, F.P. (1992). Medical microbiology (4th ed).
- Hong kong: uk: elbs with churchill livingstone, medical division of longmanGroup, UK ltd.
- Jawetz, melnick, & adelberg’s. (2007). Medical microbiology (4th ed.). United states of America: the mcgraw-hill companies,
Get These Notes as a Well-Formatted PDF
Want a clean PDF copy for easier revision, printing, or offline reading? Request the notes directly through WhatsApp.
