Intracellular bacteria Flashcards
mycoplasma
Smallest bacteria
Smallest genome of any free-living organism
Many nutritional deficiencies
* Cannot synthesize amino acids or vitamins or lipids
* Some (hemotropic) cannot be cultivated in vitro
* clinical importance: need special growth conditions for diagnosis
No cell wall
* Beta-lactams have no effect (penicillins and cephalosporins), clinical importance: antimicrobial selection
* Gram staining: poorly staining (clinical importance: increased diagnostic difficulty)
* Cell membrane contains cholesterol – need serum in media to culture (clinical importance: need special conditions for diagnosis)
Colonize mucosal surfaces or RBC
* Respiratory and urogenital tract
* May attach to RBC (= hemotropic Mycoplasmas)
* Some can invade host cells
Hemotropic Mycoplasmas
bind to surface of RBC
Source: Carrier animals
Transmission: Blood to blood contact
Target Cell: Erythrocytes
Pathogenesis: Primarily extravascular hemolysis
Clinical signs: Hemolytic anemia, Icterus
Hemotropic Mycoplasmas diagnosis and treatment
Diagnosis
* Serology
* Blood smear
* PCR
Treatment
* Tetracyclines
* Supportive care
Mycoplasma haemofelis
Disease name: feline hemotrophic mycoplasmosis
Cats
Transmission: Blood, Fleas, Placental
Clinical signs: icterus (hyperbilirubenemia)
diagnosis: Blood smear (Bacteria on RBCs, Agglutination, Ghost cells, Spherocytes), PCR
Non-hemotropic Mycoplasmas
Source: Mucosal epithelia, Carriers
Transmission: Direct contact, inhalation of aerosols, Vertical
Target Cell: Epithelium, Mesothelium
Clinical signs depend on target cells affected (Conjunctivitis, Sinusitis, Pneumonia, Polyserositis, Polyarthritis, Mastitis, Urogenital disease)
Diagnosis: Presumptive, Direct examination, Serology, Culture
(Diagnostic standard, Special culture requirements, Delicate and needs quick transport to lab, Low sensitivity, ‘Fried-egg’ colonies)
Detection: PCR
Treatment: tetracyclines
Mycoplasma bovis
Cattle
Clinical signs
* Mastitis
* Pneumonia – part of BRDC
* Polyarthritis
* Otitis media (calves)
USA economic losses
Beef—$32 million/year
Dairy—$108 million/year
Persists for months in environment
Obligate intracellular bacteria
Require host cells for replication
Elaborate mechanisms for acquiring and invading host cells
Have multiple systems for surviving within host cells
Dependence on host cells is usually nutritional
Obligate Intracellular Bacteria: Invasion
Some pathogenic bacteria can invade epithelial, endothelial, red blood or white blood cells
Bacteria surrounded by host cell membrane (vacuole)
Mechanisms of persistence and proliferation in the host cell
* Multiply inside the vacuole (Chlamydia, Mycobacterium)
* Survive the conditions in the phagolysosome (Salmonella, Yersinia, Coxiella)
* Escape from the vacuole and proliferate in the cytoplasm (Rickettsia)
Coxiella burnetii
“Q fever”
Reportable & zoonotic
Select agent – potential bioterrorism agent
2 transmission sources
* Wildlife/tick cycle
* Sheep, goats, cattle
Target cells: Monocytes, macrophages, & placental epithelial cells
Infection:
1. infects target cells
2. becomes large cell variant (Noninfectious, Labile, Replicating Form, Intracellular)
3. becomes small cell variant (Infectious, Highly resistant, spore-like, Non-replicating, Extracellular)
Clinical signs
* Late-term ruminant abortions
* Other repro signs
* Can shed even if not clinically affected
Sources
* Secreted in milk, urine, feces, reproductive secretions
* Inhalation
* Ingestion
* Direct/venereal contact
* Arthropods (>40 tick species)
* SCV are very resistant in environment
Diagnosis
Presumptive – necropsy & histopathology
Fetus (may be autolyzed)
Placenta (leathery w/ white exudate)
Direct detection: Cannot culture in vet diagnostic lab
Immunohistochemistry
PCR
chlamydia
Need host cells in order to replicate!
Infection:
1. invade epithelial cell
2. reticulate body: non infectious, replicating
3. elementary body: infectious, resistant
Target Cell: Epithelium
Source: Carrier animals (Cats, cattle, small ruminants, birds, others), Diseased animals
Transmission: Direct contact, Inhalation, Ingestion, Sexual, Vertical
Clinical Signs: Conjunctivitis, Sinusitis, Polyarthritis, Polyserositis, Hepatitis, Enteritis, Encephalomyelitis, Urogenital disease
Diagnosis: Often presumptive, Serology, Direct detection, PCR, Cytology + stains, Fluorescent antibody
Treatment: Tetracyclines
Public health - zoonotic
Chlamydia psittaci
Reportable and Zoonotic
Birds (Especially psittacines)
Transmission
* Inhalation, ingestion, Respiratory, feces
* Transmission to young via feeding
* 2 months viability in environment
Clinical signs (epithelial cells)
* Respiratory: Nasal and ocular discharge, Sneezing, Conjunctivitis
* Gastrointestinal: Diarrhea
* Liver (yellow droppings)
* Neurologic
Treatment
* Doxycycline or tetracycline (restrict calcium access, no oyster shell, mineral blocks, cuttlebones)
Rickettsia rickettsii
Intracellular, escape vacuole
“Rocky Mountain Spotted Fever” (RMSF)
Hosts: dogs, humans (Zoonotic)
Reservoir
* Small wild mammals
* Dogs (in some regions)
Transmission by Dermacentor ticks, other tick species
Target Cell: Endothelium
* fever, vasculitis, hemorrhage, thrombocytopenia
Treatment:
* palliative, doxycycline
Erlichia canis (and ewingii)
Dogs (also cats)
Vector: Rhipicephalus ticks
Target Cell: WBCs
* Pancytopenia (incl. megakaryocytes> decrease platelets)
* CNS signs
Diagnosis:
* Thrombocytopenia
* Serology: 4dx snap, titers
* PCR
Ehrlichia ruminatium
“Heartwater”
Exotic to US: Reportable
Ruminants
Vector: Amblyoma ticks
Target Cell: Endothelial cells & WBC
Anaplasma phagocytophilum
granulocytic anaplasmosis
Horses, Dogs , Humans too (zoonotic)
Target Cells = Neutrophils and endothelium
* Leukopenia
* Arteritis / phlebitis
* Thrombocytopenia
* Limb edema
* Neuritis / ataxia
Diagnosis
* morulae (inclusion body) in neutrophils
* PCR
Treatment
* Palliative
* Doxycycline, minocycline
Anaplasma marginale
Cattle, other ruminants
Suseptibility: varies
* old, naive more suseptible
Vector: ticks
Target cell: erythrocytes
Clinical signs:
* Fever
* Hemolytic anemia
* Abortion
Diagnosis: Blood smear, PCR, Necropsy
Treatment: Tetracyclines
Neorickettsia helminthoeca
“Salmon poisoning disease”
Fluke vector (fluke infected with bacteria)
Dogs (is DH of fluke)
Intermediate hosts: Snail, Salmonids
Target Cell = macrophages +/- enterocytes
Clinical signs
* Intestinal (vomiting, diarrhea, inappetence)
* Mesenteric LN (lymphadenopathy)
* Enteropathy due to cytokines (edema, inflam, hemorrhage)
Diagnosis: fluke eggs, LN FNA
Treatment: tetracycline, praziquantel
