microbiology 3020 Assignment 4,5
egypt1Riordan 2011
Infectious diseases
James T. Riordan, PhD
General Microbiology, Fall 2017
CMMB
University of South Florida
1
Part I: ID primer
2
3
ID 101
Infectious diseases (ID) are with us daily and are a major contributor to global morbidity and mortality
The need for investigations into ID mechanisms and the body’s ability to combat infectious agents—this has been heightened by:
The emergence of new pathogens, increasing drug resistance, and threats of bioterrorism
In addition, effective diagnostics are needed to quickly identify IDs and prevent their spread
Riordan 2011
3
ID diagnosis
IDs may be classified based on several criteria:
By species/strain
By organ system*
By portal of entry
Riordan 2011
4
5
Diagnosis, cont’d
Many IDs display similar symptoms, making diagnosis difficult—knowledge of a patient’s history is vital:
Ex. Travel information for (diarrhea), hunting and tularemia Francisella tularensis, farming and Q fever, Coxiella burnetii—both cause flu-like symptoms
Both tularemia (rodents) and Q fever (ungulates) are zoonotic diseases
Riordan 2011
5
Part II: Skin and soft-tissue infections
7
Skin infections
Riordan 2011
Ex. Staphylococcus aureus—Gram positive cocci, nonmotile
7
8
S. aureus
Riordan 2011
Causes abscesses walled off from body with fibrin
Can produce many toxins—ex. toxic shock superantigen—immunopathologic shock and organ failure
Many strains are multidrug resistant—MRSA are methicillin-resistant S. aureus—a major cause of nosocomial infections (in hospitals)
Some strains make exfoliative toxin (scalded skin syndrome)—erythroderma
8
9
Skin infections, cont’d
Riordan 2011
Streptococcus pyogenes—Gram positive cocci, nonmotile
9
10
S. pyogenes
Riordan 2011
Best known for causing sore throats (pharyngitis) and immunological sequelae, such as rheumatic fever
Also necrotizing fasciitis (“flesh-eating” disease) and cellulitis
Many virulence factors are encoded on bacteriophages and thus are laterally-acquired
10
11
Viral diseases of the skin
Riordan 2011
Many viral infections present as maculopapular or erythematous skin rashes
Usually infect through respiratory tract—ingress
Ex. Rubeola (measles), Herpesvirus (chickenpox), and Rubella (German measles)
11
Integumental infections
Common bacterial IDs of the skin
Riordan 2011
12
Integumental, cont’d
Common viral IDs of the skin
Riordan 2011
13
Q & A
Questions?
Riordan 2011
Part III: Respiratory tract infections
16
Respiratory infections 101
Riordan 2011
The mucociliary clearance is primary defense
Bordetella pertussis (cause of whooping cough) inhibits it by binding to lung cilia—primary pneumonia
Pneumonia is a disease, not a specific infection—caused by many different microbes
16
17
S. pneumoniae
Riordan 2011
Streptococcus pneumoniae is the most common etiology—has capsule that prevents phagocytosis and can invade the bloodstream (bacteremia) and the covering of the brain (meningitis)
17
18
M. tuberculosis
Riordan 2011
An acid-fast bacillus (mycolic acid)—ancient and re-emergent pathogen
Forms calcified tubercles in the lung—can disseminate hematogenously
High rates of mortality in systemic disease and increasing multidrug resistance
18
19
Viral diseases of the lungs
Riordan 2011
Numerous viruses can cause lung infections:
Influenza A virus and rhinovirus?
SARS (severe acute respiratory syndrome)
Respiratory syncytial virus (RSV)—the most common cause of pneumonia among infants and children under 1 year of age
19
Part V: Central nervous system infections
Meningitis—infection of membrane surrounding brain
Common etiologies include: Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis
Meningitis
Riordan 2011
21
N. meningitidis
N. meningitidis—has thick capsule and type IV pili
High mortality associated with bloodstream infections—also crosses from capillary into cerebrospinal fluid
Riordan 2011
22
Clostridium neurotoxins
Clostridium toxins—botulinum and tetanospasmin
C. botulinum: botulinum toxin—anaerobe, grows in canned food—spores survive unless autoclaved
Toxin blocks release of acetylcholine causing flaccid paralysis
C. tetani: tetanospasmin—anaerobe grows in puncture wounds
Blood flow interrupted; tissue becomes anaerobic—toxin blocks release of gamma-aminobutyric acid (GABA), inhibitory transmitter
Causes spastic paralysis
Riordan 2011
23
Clostridium toxins
Botulinum toxin, BoNT
Riordan 2011
24
Q & A
Questions?
Riordan 2011