Gram +Ve Bacilli
* There are 2 important clinically species :
1-
Bacillus (( aerobic and
faculitative anaerobic , spore forming ))
2- Clostridium (( obligate anaerobic , spore forming ))
|
Bacillus anthracis |
|
|
Characteristics |
*larg Gr+Ve bacilli. usually arranged in chain *spore forming ,non motile bacilli. *spores are oval , central& non-projecting *capsule consists of polypeptide glutamic acid. *
polysaccharide cell wall . *faculitative anaerobic . *
nonfastidious growth (( not need complex media )) *highly infection organism |
|
Habitat |
*infected animals, human are accidental host . *spores remain viable for
years in contaminated soil & resistant heat up to 150 C for hour . |
|
Transmission |
*direct contact *airborne route |
|
Pathogenesis |
*capsule =antiphagocytosis * There are 3 extotoxin :- - Edma toxin . – lethal toxin . *antrax
exotoxin = CNS distress , respiratory failure & anoxia * Spore can survive in soil for years . |
|
Diseases |
*cutaneous anthrax ( malignant pustule ) . fatal rate 10% *
gastrointestinal anthrax . *
inhalation anthrax . *enteric anthrax (fatal rate 50%) *pulmonary
anthrax (woolsorters disease ) (fatal rate 50%) *meningitis following anthrax bacteremia . |
|
Laboratory Identification |
(medusa head ) colonies on blood agar . *McFadyean
reaction (capsule stains red – mauve with loeffler polychrome methylene blue
. *catalase *
DFA Test : Positive . (( Direct Fluorescent
AntiBody )) *non hemolytic colonies . * capsule
not observed in culture . but
observed with Indian ink stain |
|
Bacillus anthracis |
|
|
Characteristics |
·
larg Gr+ Ve bacilli , usually arranged in chain ·
Spore forming & motile bacilli ·
Spores are oval , central & non
–projecting . ·
Non capsulated bacilli ·
faculitative anaerobes ·
nonfastidious growth(( not need complex media
)) ·
Opprtunistic infection . |
|
Habitat |
* soil
,vegetation , water , food includes cerals meat & spices |
|
Transmission |
Foodborne route |
|
Pathogenesis |
·
heat stable enterotoxin =
causes emetic gastroenteritis . ·
heat- labile enteroxin =
causes diarrheal gastroenteritis . ·
spore can survive in soil . ·
cytotoxic enzyme : Destruction Tissues . |
|
Diseases |
* toxic food poisoning includes 2 types of infections :
1-emetic gastroenteritis ( severe nausea & vomiting ) 2- diarrheal
gastroenteritis ( abdominal pain & profuse
watery stool ) * ocular infection *
intravenous catheter . |
|
Laboratory Identification |
·
( medusa head ) colonies . ·
complete hemolysis on
blood agar .(( Beta Hemolytic )) |
Corynebacterium
·
gram +Ve bacilli (( club shaped )) .
·
aerobic and faculitative anaerobic .
·
non spore forming .
·
non Acid fast .
·
non motile .
·
catalase +Ve
.
·
most (( but
not all )) Ferment carbohydrate .
·
high guanine and cytocine content .
·
meta chromatic granulces .
|
Corynebacterium diphtheriae |
|
|
Characteristics |
*Gr+ Ve Polymorphic bacilli (club-shaped) . *cells appear in
chineses-letter arrangement . *
non capsulate , non sporing , non motile . *Facultative anaerobes . *Ferment carbohydrate . *
Most grow well in lipid free media . |
|
Habitat |
Nasopharynx & occasionally skin of human |
|
Transmission |
·
droplets
spread ·
direct contact |
|
Pathogenesis |
·
Diphtheria exotoxin = block protein synthesis ·
Unknown Virulance Factors. |
|
Diseases |
·
diphtheria : 1- localized
inflammation of the throat 2-
infecting organisms do not
invade but rather elaborate an exotoxin that spreads through blood 3-
pharynx , larynx , & nose are main sites 4-
pseudo – membrane is formed & may lead to respiratory obstruction 5- mainly affecting infants over 1 year old children & young
adults 6-
Endocarditis |
|
Laboratory Identification |
·
Specific media for C.diphtheria :- 1- cysteine
tellurite agar 2- serum tellurite agar . ·
back colonies on blood tellurito agar ·
Use loeffler medium to recover C.diphtheria . ·
detection toxin by Elek test . ·
teelurite inhibit
growth of most upper respiratory bacteria and gram negative rods . |
Mycobacterium
·
gram +Ve bacilli .
·
non motile .
·
fastidious growth (( Need Complex media )) .
·
acid fast .
·
non spore forming .
·
aerobic .
·
Cell Wall Rich With Lipid ((
making the organism resistant to most disinfects , detergents , common antibacterial
)) .
|
Mycobacterium tuberculosis |
|
|
Characteristics |
·
acid fast bacilli ,
slightly curved (ziehl – neelsen stain : red cooler ) ·
cell wall rich with lipid
(( making the organism resistant to most disinfects , detergents , common
antibacterial )) . ·
non-capsulate , non –sporing , non –motile ·
obligate aerobes ·
highly infection organism |
|
Habitat |
·
Strict human pathogen |
|
Transmission |
·
droplets
spread ·
direct contact ·
foodborn route (rarely) |
|
Pathogenesis |
·
capsule = Antiphagocytois . ·
Ability to
multiply inside macrophages . |
|
Diseases |
·
tuberculosis : 1- primary
tuberculosis in lungs & lymph nodes 2- progressive primary tuberculosis -tuberculous
bronchopneumonia -
military
tuberculosis -tuberculosis
meningitis -
bone & joint tuberculosis -
genito- urinary tuberculosis 3- post –primary
tuberculosis : -T.B.remains
dormant for years after primary tuberculosis -it
reactivates due to delayed hypersenseitivity - it may
involve all manifestation in progressive Primary tuberculosis |
|
Laboratory Identification |
·
rough , dry & yellow
colonis on Lowenstein – Jensen
medium after 2-3 weeks at 37 C ·
detection of acid fast
bacilli under light microscope . ·
tuberculin skin test +
kuantiferon-TB test = sensitive marker |
|
Mycobacterium leprae |
|
|
Characteristics |
·
acid fast bacilli ,
slightly curved (ziehl –neelsen stain : red cooler ) ·
cell wall rich with lipid
(( making the organism resistant to most disinfects , detergents , common
antibacterial )) . ·
non-capsulate , non –sporing , non –motile ·
obligate aerobes |
|
Habitat |
Strict human pathogen |
|
Transmission |
·
direct contact ·
airborne spread ·
incidence of disease in contact is low ·
spread in
the community is slow |
|
Pathogenesis |
·
principal target cell for
this bacterium is schwann cell ·
this bacteria causes
anaesthesia & miscle paralysis |
|
Diseases |
·
leprosy
: 1- slow
, chronic &progressive infection 2- minaly
affects the skin & peripheral nerves 3-
long incubation period ,
usually form 3- 5 years 4- tow
forms of leprosy : -lepromatous
(lesions spread & involve mucous membrane . this form is progressive
& severe , large number of bacteria are found in the body which acts as
kind of unlimited culture medium ) - tuberculoid (lesions are localized &
tend to be bening , this form is self – healing ) |
|
Laboratory Identification |
·
no growth on Lowenstein –
Jensen medium ·
detection of acid fast
bacilli in smears or secretion
from lesions ·
diagnosis with specific skin test . ·
Microscope sensitive to : lepromatous . |
Clostridium SPP
(Anaerobic,
spore-forming,Gram-positive Rods)
-All anaerobic,
gram-positive rods capable of forming endospores was placed in the genus (Clostridium).
-Clostridium spp
was defined by four properties 1)presence of endospores.
2)strict(obligate) anaerobic.
3)inability to reduce sulfate to sulfite. 4)gram-positive cell wall structure.
-the Clostridium
are ubiquitous in soil, water, and sewage and part of the normal flora in
gastrointestinal tract of animal and human.
|
Clostridium tetani |
|
|
Characteristics |
·
larg Gr+ Ve bacilli ·
sporing , motile bacilli ·
spores are spherical , terminal ( drumstick ) ·
non capsulate bacilli ·
obligate anaerobes ·
difficult to grow.because
the organism is extremely
sensitive to oxygen toxicity. ·
Not ferment carbohydrates. |
|
Habitat |
·
soil & commensal in intestinal tract of animal . ·
spore remain viable after
dry heat up to 160 C for 1 hour . |
|
Transmission |
Via major or minor wounds . |
|
Pathogenesis |
·
tetanolysin ( exotoxin) = lyses
erythrocytes . ·
tetanospasmin ( exotoxin )
= neurotoxin that affects CNS causing muscular rigidty and spasns . ·
spore formation. |
|
Diseases |
*tetanus
( human & animals) 1- generalized tetanus 2-localized
tetanus 3-neonatal tetanus |
|
Laboratory Identification |
·
swarming colonies on blood agar ·
detection of neurotoxin by serological
method . |
|
Clostridium perfringens |
|
|
Characteristics |
·
relatively larg Gr + Ve
bacilli , usually arranged in chain ·
non motile bacilli & capsulate bacilli ·
spores are oval , subterminal & non – projecting ·
spores rarely seen in infected materials ·
anaerobes , but it can tolerate exposure to air for short time ·
hemolytic in culture. ·
Replicate rapidly ·
Type A is
responsible for most human disease. |
|
Habitat |
·
soil & water &
intestinal tract of human and animals ·
bacteria & spores
common contaminants of raw meats ·
spores remain viable after heat up to 100 C
for up to 3 hours |
|
Transmission |
·
direct contact ·
endogenous
spread ·
foodborne
route |
|
Pathogenesis |
·
alpha toxin = destroys cell membranes ·
enterotoxin = associated with food – poisoning ·
DNAse = hydrolyses DNA |
|
Diseases |
·
gas gangrene ·
food poisoning ·
septicemia. ·
Soft- tissue infections. |
|
Laboratory Identification |
·
beta hemolytic colonies on blood agar ·
entire edge for colonies on blood agar ·
detection of alpha toxin via the nagler reaction |
|
Clostridium difficile |
|
|
Characteristics |
·
larg Gr+ Ve bacilli usually arranged in chain ·
sporing , motile bacilli ·
spores are
oval ·
obligate anaerobes ·
part of the normal intestinal flora |
|
Habitat |
Soil
& water & intestinal contents of various animals . Faeces of 3-5 % of
healthy adults. Regularly , present in faeces of healthy adult infant . |
|
Transmission |
Endogenous spread . Faecal – oval route |
|
Pathogenesis |
·
toxin A ( enterotoxin) = antiphagocytosis ·
toxin B ( cytotoxin ) |
|
Diseases |
·
pseudo – membranous colitis ·
antibiotic- associated diarrhoea |
|
Laboratory Identification |
·
difficult to isolate in ordinary media ·
detection toxins in faeces |
|
Clostridium botulinum |
|
|
Characteristics |
·
larg Gr +Ve bacilli ·
sporng , motile bacilli ·
sporing are oval ,
terminal or subterminal & projecting ·
non capsulate bacilli ·
obligate anaerobes ·
fastidious
growth. |
|
Habitat |
·
soil , vegetable & fruits are the
normal habitat ·
canned products ·
spores remain viable after
heat up to 100 C for up to 3 hours |
|
Transmission |
Foodborne route |
|
Pathogenesis |
·
spore formation ·
Botulinum
toxin ·
Binary toxin. |
|
Diseases |
·
botulism 1- this food poisoning is intoxication rather than an
infection . *Food borne botulism *infant botulism *inhalation botulism |
|
Laboratory Identification |
*irregulary round colonies on blood agar *
detection of toxin in the food or serum from the patient is the way of confirming
the diagnosis |
