Normal Microbiota of the Respiratory System
A. Upper
respiratory system
Staphylococci
Streptococci
Diphtheroids
Are also many potentially pathogenic microbes but are
normally outcompeted by predominant flora
B. Lower
respiratory system
Normally sterile due to ciliary escalator
Bacterial Diseases of the Upper Respiratory System
A.
Streptococcal Pharyngitis (Strep Throat) (Fig. 24.3)
Etiology: Streptococcus
pyogenes (Group A beta-hemolytic streptococcus)
Transmission:
Respiratory secretions
Pathogenesis:
Infect and replicate in pharynx
Produce toxins that lyse cells
Characteristics:
fever, inflammation of mucus membranes of the pharynx
Treatment:
Penicillin (to prevent complications)
Complications:
Pneumonia,
Rheumatic fever
Scarlet Fever
B. Scarlet
Fever (Fig. 24.4)
Etiology: Streptococcus
pyogenes lysogenized by a bacteriophage
Transmission:
Respiratory secretions
Pathogenesis:
Bacteria produces Erythrogenic (reddening) toxin
Characteristics:
High fever, “strawberry tongue”, red skin rash à skin peels off.
Treatment:
penicillin
C. Diphtheria
(Fig 24.5)
Etiology: Corynebacterium
diphtheriae lysogenized by a bacteriophage
Transmission:
Direct contact – respiratory droplets
Pathogenesis:
Produce exotoxin à
inhibits protein synthesis à nerve, heart, liver, kidney damage
Characteristics:
Sore throat, fever, swelling of neck
Pharynx has diphtheria membrane (dead tissue,
bacteria, fibrin) (Fig 24.6)
Treatment:
Active disease:
passive immunization with antibodies to neutralize toxin
Penicillin, erythromycin to eliminate bacteria
Immunization:
DPT vaccine
Viral Diseases of the Upper Respiratory System
A. The Common
Cold
Etiology: 200
different viruses
50% rhinoviruses
20% coronaviruses
Transmission:
Respiratory route
Pathogenesis:
Infect and replicate in upper respiratory mucosa
Characteristics:
sneezing, nasal secretion, congestion
Treatment:
none
Bacterial Diseases of the Lower Respiratory System
A. Pertussis
(Whooping Cough) (Fig. 24.8)
Etiology: Bordetella
pertussis
Transmission:
Respiratory route
Pathogenesis: Endotoxin destroys ciliated epithelial
cells and inhibits immune system
Characteristics:
Mild cough à
violent coughing (enough to break ribs) à vomiting, convulsions
Treatment:
Active infection: none
Immunization:
DPT vaccine
B.
Tuberculosis (Fig. 24.9)
Etiology: Mycobacterium
tuberculosis
Transmission:
Inhaling bacilli on droplet nuclei
Pathogenesis: (Fig. 24.10)
1. Bacteria
reach alveoli and infect alveolar macrophages
2. More
macrophages surround and wall off area, form a tubercle
3. Many
macrophages die and form caseous center, symptoms appear. Disease may be arrested and tubercles
calcified
4. In some
cases, liquefaction occurs à caseous center enlarges and forms air filled
tuberculous cavity. Bacteria multiply
outside macrophages
5. Tubercle
ruptures, bacteria released into bronchiole, then to circulatory and lymphatic
systems
Characteristics:
Weight loss, bloody cough à death
Diagnosis: Positive
tuberculin skin test (Fig. 24.11), chest x-rays
Treatment:
Active infection:
Isoniazid + Rifampin for months
Immunization:
BCG vaccine (used outside the U.S.)
C. Bacterial
Pneumonias
1.
Pneumococcal Pneumonia (Fig. 24.13)
(Most common type of pneumonia)
Etiology: Streptococcus
pneumoniae
Transmission:
Respiratory route
Pathogenesis:
à bacteria introduced into bronchi and alveoli
à capsule prevents phagocytosis by macrophages
à infection in lower lungs
à pneumonia
Characteristics:
high fever, breathing difficulty, chest pain
Treatment:
Active infection:
Penicillin
Immunization:
Pneumovax vaccine (from capsular material)
2. Haemophilus
influenzae Pneumonia
Etiology: Haemophilus
influenzae
Transmission:
Respiratory Route
Pathogenesis:
Affects immune suppressed, esp. patients with
alcoholism, poor nutrition, cancer or diabetes
Infection in lower lungs à pneumonia
Characteristics:
high fever, breathing difficulty, chest pain
Treatment:
cephalosporin
3.
Mycoplasmal Pneumonia (Fig. 24.14)
Etiology: Mycoplasma
pneumoniae
Transmission:
Respiratory route
Pathogenesis:
infection in lower lungs
Characteristics: fever, cough, headache, pneumonia
(esp. in children)
Treatment:
Erythromycin, Tetracycline
4.
Legionellosis
Etiology: Legionella
pneumophila
Transmission:
Respiratory Route (airborne from water cooling towers of a/c units)
Pathogenesis:
compromised immune system à infection of lower lungs
Characteristics:
pneumonia
Treatment:
Erythromycin
Viral Diseases of the Lower Respiratory System
A.
Respiratory Syncytial Virus (RSV)
Etiology:
Respiratory Syncytial Virus
Transmission:
Respiratory Route
Pathogenesis:
Infects lower Respiratory system
Most common viral respiratory disease in infants
Virtually all children infected by age 2
Characteristics:
Coughing and wheezing that last more than one week
Treatment:
Ribavirin for seriously ill
B. Influenza
Etiology:
Influenza virus
Structure:
(Fig 24.16)
Hemagglutinin (H) – viruses attachment site
Neuraminidase (N) – Functions in release of viral
progeny
Three types based on internal nucleoproteins
Type A influenza virus – causes severe illness
Type B influenza virus – causes milder illness
Type C influenza virus – rarely causes disease
Recover from flu à have immunity,
but not for long because of …
1. Antigenic
drift – mutations that cause minor changes in H or N
à immune system can’t recognize as well
2. Antigenic
shift – major change in H or N (ex: H1 à H2)
à immune system can’t recognize at all
Mechanism of antigenic shift
Pigs, ducks, and humans can have different strains of
influenza
Pigs are good “mixing vessels”
Pig can be infected with duck and human influenzas at
the same time
The two different strains of virus infect same cell
and swap segments of viral genomes
New virus had different H or N genes
Naming: named
according to variety of H and N have and where and when initially isolated
(Table 24.1)
Ex: H3N2
Hong Kong flu (1968)
Transmission:
Respiratory Route
Pathogenesis:
viral destruction of cells lining the respiratory tract
Characteristics:
Fever, chills headache à mild upper
resp. infections to pneumonia and death.
No diarrhea
Treatment:
Active infection:
Relenza and Tamiflu (Neuraminidase inhibitors à shorten duration)
Immunization:
flu vaccine, also Amantadine
Chemoprophylactic: Amantadine
Historic note:
1918 influenza epidemic killed 20 million. This is more than all the people killed in WWI. (Fig 21-13)
Fungal Diseases of the Lower Respiratory System
A.
Histoplasmosis
Etiology: Histoplasma
duboisii
Transmission:
(Fig. 24.18)
Seen in states adjoining Mississippi and Ohio Rivers
(Fig. 24.18)
Respiratory Route
White mold in soil, esp. bird droppings (room temp.,
low moisture)
Human inhales spores
Pathogenesis:
Grow as yeast in body (body temp., high moisture)
(Fig. 24.17)
à lung tissue damage and lesions in other organs
Characteristics:
Poorly defined
Mostly subclinical, but can vary from mild
respiratory distress to severe generalized disease
Treatment:
Antifungals (azoles)
B.
Pneumocystis Pneumonia
Etiology: Pneumocystis
jiroveci (formerly P. carinii) (Fig. 24.22)
Transmission:
Normal flora in healthy lungs
Pathogenesis:
Infection in lower lungs of immune suppressed à pneumonia
Primary indicator of AIDS
Characteristics:
breathing difficulty, chest pain
Treatment:
Trimethoprim-sulfamethoxazole (Bactrim)
Chapter
25 Microbial Diseases of the Digestive
System
Normal microbiota of the digestive system
A. Mouth
Many bacteria
Staphylococci
Streptococci
Diphtheroids
B. Stomach
and small intestine
Few microbes because of acid and rapid movement of
food
C. Large
intestine
Enormous microbial population à 40% of fecal mass is microbes
Lactobacillus
E. coli
Enterobacter
Two Types of Diseases of the Digestive System
A.
Intoxications
True food poisonings
Follow consumption of preformed microbial toxins
Usually short time to produce symptoms (few hours)
Usually no fever
B. Infections
Due to multiplication of viable microorganisms in
host
Longer time to produce symptoms (8 – 48hrs)
Usually fever
Bacterial Diseases of the Lower Digestive System
A.
Staphylococcal Food Poisoning
Etiology:
Intoxication from toxic strain of Staphylococcus aureus
Transmission:
(Fig. 25.6)
Infected food handler infects protein rich foods
(custards, cream pies, ham)
Food stored at room temperature à bacteria grows and produces heat-resistant toxins
with no obvious spoilage
Food ingested
Pathogenesis:
toxin triggers brain’s vomiting reflex center, abdominal cramps,
diarrhea
Characteristics:
In 1-6 hours à
severe nausea, vomiting, cramps, occasional diarrhea à recovery in 24 hours
Treatment:
none
B.
Salmonellosis
Etiology: Salmonella
enteriditis
Transmission:
Fecal (animal)/ oral (human)
à eating undercooked poultry contaminated during
slaughter, undercooked eggs
à pets, esp. reptiles (90% of turtles, iguanas are
carriers)
à Also raw mung bean sprouts and alfalfa sprouts
Pathogenesis:
invade intestinal mucosa and multiply à inflammation
Characteristics:
12-36 hour incubation
à fever, diarrhea, abdominal pain, nausea for 2-4 days
Treatment: none
C. Typhoid
Fever
Etiology: Salmonella
typhi
Transmission:
Fecal (humans) / oral (humans) (Fig 25.10)
Pathogenesis:
invade mucosa of intestine à systemic infection
Characteristics:
2 weeks incubation à high fever, continual headache, diarrhea,
perforation of intestines à
10 % mortality (untreated)
Treatment: Cephalosporin
D. Cholera
Etiology: Vibrio
cholerae (Fig. 25.12)
Transmission:
fecal-oral (usually from contaminated water)
Pathogenesis:
attaches and grows on intestinal epithelium
à releases cholera enterotoxin
à triggers transport of ions to lumen of intestine
à large quantities of water transported to lumen due
to osmosis
Characteristics:
severe diarrhea (lose 5 gallons water per day), “rice water” stool,
severe dehydration, shock, death (50% mortality if untreated)
Treatment:
Active infection:
oral rehydration solution (water, sugar, salts)
Immunization:
cholera vaccine, but limited effectiveness and duration
E. Escherichia
coli Gastroenteritis
1. E. coli
Gastroenteritis (travelers diarrhea)
Etiology: Escherichia
coli
Transmission:
fecal-oral (water and food)
Pathogenesis:
grow in intestine à
produce enterotoxin similar to but less toxic than Vibrio cholerae
Characteristics:
diarrhea
Treatment: short duration à usually do not use antibiotics
2. E. coli
Gastroenteritis (severe cases)
Etiology: Escherichia coli O157:H7
Transmission:
fecal-oral (normal flora in 50% of feedlot cattle à contaminate beef during processing, or raw alfalfa
sprouts)
Pathogenesis:
grow in intestine à
produce Shiga toxin
Characteristics:
bloody diarrhea, severe abdominal cramps, and kidney damage
Treatment:
Antibiotics
F. Stomach
Ulcers
Etiology: Helicobacter
pylori (discovered 1982)
Transmission:
Fecal/oral
Pathogenesis: (Fig. 25.13)
Infects stomach lining
à Survives by producing ammonia
à local neutralization of stomach acid.
Damages mucus producing cells
à no mucus
à gastric juice damages epithelium
Characteristics:
Acute gastritis (inflammation of stomach)àlesionsà ulcers
Treatment: Antibiotics
Viral Diseases of the Digestive System
A. Mumps
Etiology: Paramyxovirus
Transmission:
Respiratory Route (in saliva or respiratory secretions)
Pathogenesis: Infects salivary glands
Characteristics:
Fever and swollen salivary glands (Fig 25.14)
Complications:
orchitis (inflammation of testes) in 20 – 35% of males past puberty à possible sterility
Treatment:
Active infection:
none
Immunization:
MMR vaccine
B. Hepatitis
1. Hepatitis
A
Etiology:
Hepatitis A virus
Transmission:
Fecal-oral
Pathogenesis:
Incubation 2-6 weeks
invades liver à hepatitis (inflammation of liver)
Characteristics:
Fever, headache, malaise, diarrhea, abdominal discomfort, jaundice,
recover in 3 weeks
Treatment (immunization): Immunoglobulin for temporary protection
2. Hepatitis
B
Etiology:
Hepatitis B virus (HBV) (Fig. 25.15)
Transmission:
Parenteral (puncture wounds or cuts) and sexual contact
Pathogenesis:
infects liver à
hepatitis (inflammation of liver)
Characteristics:
90 day incubation
Nausea, vomiting, fever, abdominal pain, jaundice
1% mortality
90 % of acute infections à complete recovery
Treatment: Hepatitis B Vaccine
3. Hepatitis
C
Etiology:
Hepatitis C virus (HCV)
Transmission:
Parenteral and sexual contact
(80% of intravenous drug users infected)
(in one third of cases mode of trans. Can’t be
identified)
Pathogenesis:
Infect liver à
hepatitis
Characteristics:
Nausea, vomiting, fever, abdominal pain, jaundice
85% progress to chronic hepatitis
à 20% of these develop cirrhosis or liver cancer
Kills more people than AIDS in the U.S.
Treatment: none
4. Hepatitis
D
Etiology:
Hepatitis D virus (HDV)
Transmission:
Parenteral and sexual contact
Pathogenesis:
HDV can’t infect by itself, must be a coinfection
with HBV
Infect liver à hepatitis
Characteristics:
Several times higher incidence of severe liver damage
and mortality than HBV alone
Treatment: HBV vaccine
5. Hepatitis
E
Etiology:
Hepatitis E virus
Transmission:
Fecal-oral (mainly in India and Asia)
Pathogenesis:
Incubation 2-6 weeks, invades liver à hepatitis
Characteristics:
Fever, headache, malaise, jaundice, recover in 6 weeks
Treatment: Immune globulin
C. Viral
Gastroenteritis
1. Rotavirus
Etiology:
Rotavirus (Fig. 25.17)
Transmission:
Fecal/Oral
90% of children in US infected
Pathogenesis:
Viral replication in GI tract
Characteristics:
Slight fever, diarrhea, vomiting for one week
Treatment:
vaccine but recalled due to cases of bowel obstruction
2. Norwalk
viruses
Etiology:
Norwalk viruses
Transmission:
Fecal/oral (one of the most common causes of gastroenteritis)
Pathogenesis:
Viral replication in GI tract
Characteristics:
Nausea, vomiting, abdominal cramps for 1 – 3 days
Treatment:
oral rehydration
Protozoan Diseases of the Digestive System
A. Giardiasis
Etiology: Giardia
lamblia (Fig. 25.18)
Transmission:
Fecal – oral (usually water contaminated by people or animals)
Pathogenesis: Infect intestines
Characteristics:
prolonged diarrhea, flatulence, weight loss, abdominal cramps
Treatment:
Metronidazole (Flagyl)
B. Amoebic
Dysentery
Etiology: Entamoeba
histolytica
Transmission:
Fecal – oral
Pathogenesis:
Releases enzymes à
breakdown intestinal tissues (Fig. 25.20)
Characteristics:
bloody diarrhea. Can cause fatal
abscesses in organs
Treatment:
Metronidazole (Flagyl)
Chapter
26 Microbial Diseases of the Urinary
and Reproductive Systems
Normal Microbiota of the Urinary and Reproductive
System
In both males and females, normal urinary system is
sterile except near the opening of the urethra
The vagina has many microbes, but Lactobacilli is
predominant
Bacterial Diseases of the Urinary System
A. Cystitis
Etiology:
usually E. coli
Transmission:
Autoinnoculation with intestinal bacteria
Pathogenesis:
Infection and inflammation of the urinary bladder
Characteristics:
difficult, painful, urgent urination
Treatment:
Trimethoprim-sulfamethoxazole (Bactrim)
Bacterial Diseases of the Reproductive System
A. Gonorrhea
Etiology: Neisseria
gonorrhoeae (Fig. 26.7)
Transmission:
Sexual contact (Fig. 26.5)
Pathogenesis:
Attaches its pili to genital epithelial cells and multiplies
à inflammation à scarring
Characteristics:
Males – urethritis and discharge à sterility (Fig. 26.6)
Females – usually asymptomatic early on, but can
cause Pelvic Inflammatory Disease later à sterility (Fig. 26.8)
Can pass on to newborn à eye infections à blindness
Treatment:
Ciprofloxacin
B.
Nongonococcal Urethritis (NGU)
Etiology:
Most often Chlamydia trachomatis
Transmission:
Sexual contact (most common sexually transmitted pathogen in U.S.)
Pathogenesis:
Slightly milder disease than gonorrhea.
Infect and ascend the reproductive tractà inflammation à scarring
Characteristics:
Males – urethritis and discharge à sterility
Females – usually asymptomatic but can cause PID à sterility
Treatment: doxycycline
C. Syphilis
Etiology: Treponema
pallidum (Fig 26.10)
Transmission: Sexual contact (Fig. 26.9)
Pathogenesis:
invade bloodstream à
systemic infection
Characteristics: (Fig 26.11)
Primary stage
7 – 21 days after infection
à Painless chancre at site where pathogen entered body
à disappears in a few days
Secondary stage
Several weeks later
à widespread skin rash à gone in a few weeks
Tertiary stage
Many years later
à gummas (devastating lesion) on skin, internal
organs, nervous system
à insanity, blindness, partial paralysis, organ
failure
Complication:
Congenital syphilis à Bacteria transmitted across placenta à mental retardation, or stillbirth
Treatment: penicillin
Viral Diseases of the Reproductive System
A. Genital
Herpes
Etiology:
Usually Type 2 Herpes Simplex Virus (HSV-2), but can
be Type 1 Herpes Simplex Virus (HSV –1)
Transmission:
Sexual contact
Pathogenesis: Latent infection of local nerve fibers
Characteristics:
Ulcers on or around genitalia (Fig. 26.13)
Complications:
Neonatal herpes
à Virus can cross placental barrier or be transmitted
during childbirth
à Spontaneous abortion, mental retardation, defective
hearing and vision
à Usually deliver by Cesarean section
Treatment: Acyclovir shortens duration and frequency
of recurrences
B. Genital
Warts
Etiology:
Human Papillomavirus (HPV)
Transmission:
Sexual contact
Pathogenesis:
Infection causes benign tumors (warts) (Fig. 26.14)
Characteristics:
Warts on genitals
Complications:
More than 60 serotypes, a few can cause cervical cancer and cancer of
the penis
Treatment: Surgery or cryotherapy
Fungal Disease of the Reproductive Systems
A.
Candidiasis (“yeast infections”)
Etiology:
Usually Candida albicans