Topic # 7: Bacterial and Viral
Diseases and their Treatment
Bacterial Disease
Pneumonia, Tonsillitis, Tuberculosis, Botulism, Toxic Shock Syndrome,
Syphilis, Lyme disease
Bacterial Diseases: Bacterial Pneumonia
Streptococcus pneumoniae (Most common cause; Infection of the lungs;
Fluid build up preventing oxygen uptake
Top ten causes of death; 30% mortality if untreated; Spread by
breathing infected air
Medical treatment: antibiotics
Bacterial Diseases: Tonsillitis
Caused by either Streptococcus bacteria or virus; Red sore throat
, high temperature, bad breath
Treated with antibiotics; Tonsillectomy is rare
Bacterial Diseases: Tuberculosis (TB)
an infection primarily of the lungs (a pneumonia); caused by
bacteria called Mycobacterium tuberculosis
spread by breathing infected air (close contact)
dormant for years without symptoms or spreading to other people; Walled
off by scar tissue
Can reactivate when the immune system is weakened; causes infection in
the lungs or other parts of the body.
Symptoms: fatigue, fever, weight loss, coughing, and night sweats;
Without treatment TB can be lethal
diagnosis: skin tests, chest x-rays, and sputum analysis
HIV responsible for an increased frequency of TB; Isoniazid, INH is the
anti bacterial drug of choice (often with Streptomyocin)
Selective for S. pneumoniae; INH Drug-resistant TB is serious
Bacterial Diseases: Botulism
3 Types: food poisoning in canned goods; puncture wounds; Infant
botulism; Clostridium botulinum produces nerve toxin; most potent,
lethal substance known.; Botulism is a disease caused by this toxin;
The toxin paralyzes muscles
grows best in low oxygen conditions e.g. canned food, puncture wounds,
babies’ intestines (no competition)
toxin is destroyed by high temperature ; Medical treatment: induce
vomiting, effective antitoxin
Bacterial Diseases: Toxic Shock
Syndrome
Caused by toxin producing strains of Staphylococcus aureus;
colonizes skin and mucous membranes in humans
associated with use of super absorbent tampons; Incidence: 1-2/100,000
women 15-44 years of age
5% of all cases are fatal; Symptoms: sudden onset of fever, chills,
vomiting, diarrhea, muscle aches and rash
can rapidly progress to severe and intractable hypotension (low blood
pressure) and multisystem dysfunction
Medical treatment: antibiotics and intravenous fluid
Bacterial Diseases: Syphilis
STD; Caused by cork-screw shaped spirochete: Treponema pallidum;
Begins as chancre
Without treatment can clear up or recur months later as secondary
syphilis.
Secondary syphilis is a systemic stage of the disease; arthritis,
kidney problems, and liver abnormalities
may persist or resolve (go away) without treatment; May reoccur
as tertiary syphilis
Tertiary syphilis is also a systemic stage of the disease;
More serious: nodule formation causing blindness, heart problems,
stroke, deafness
Medical treatment: antibiotics (injected penicillin)
Bacterial Diseases: Lyme disease
Borrelia burgdorferi; Spread by ticks; Causes bull’s-eye rash; Common
in NE US, Nova Scotia, Ontario (areas of white tailed deer)
12 deer tick in Newfoundland, one with Lyme disease; Can cause
arthritis, heart disease, nervous disorders
Must be treated within a month with antibiotics
Viral Diseases
Immune Deficiency: AIDS
HIV targets T helper cells; Retrovirus attaches to CD4 receptors on
membrane of T helper cells
Transmission: Body fluids, i.e., blood, semen, breast milk, vaginal
secretions
HIV Replication Cycle
HIV binds to CD4 receptor site; Enters cells; Capsid removed releasing
viral RNA
Reverse transcriptase catalyses synthesis of single strand of DNA from
viral RNA
Reverse transcriptase catalyses synthesis of second single strand of
DNA from viral RNA
Double strand viral DNA inserts into the chromosome of host cell called
provirus
Uses host protein synthesis mechanism to produce capsid proteins and
viral RNA
Assembles viruses; Exits T helper cell by budding; Takes a piece of
host membrane with it
Immune Deficiency: AIDS progression:
Phase I: few weeks to a few years; flu like symptoms, swollen
lymph nodes, chills, fever, fatigue, body aches.
Virus is multiplying, antibodies are made but ineffective for complete
virus removal
Phase II: within six months to 10 years; opportunistic infections
present, Helper T cells affected;
5% may not progress to next phase
Phase III: helper T cells below 200 cells/mm; Has AIDS
opportunistic infections and /or cancers present, clinical AIDS, death
AIDS Pandemic
More than 36 million infected with HIV worldwide; Most infections (65%)
in sub-Sahara of Africa
Increasing spread in Asia and India; Most often spread by heterosexual
contact outside U.S.
Safer Sex
Abstinence; Reduce number of sexual partners; Choose sexual partners
with low risk behavior
Use latex or polyurethane condoms or barriers; GET TESTED
AIDS Test
Test for antibodies to AIDS
Not the virus itself
About 6 months to produce enough antibodies to show up positive
Not just one strain of HIV
2 genetically different viruses (HIV1, HIV2)
3 major strains M,N,O of HIV1
M (main) strain has 11 different subtypes
HIV2 less virulent (6 strains)
New AIDS Treatments
Reverse Transcriptase inhibitors: AZT, ddI, d4T, 3TC; Protease
inhibitors: ritonavir, saquinavir
Early treatment may delay/prevent clinical AIDS; Vaccine: virus mutates
rapidly preventing effective vaccine production at this time
Promising research tested in monkeys: vaccine to promote killing of
infected helper cells by killer T cells (never used in any other
disease); Works in monkeys. Will it work in people?
SARS: Severe Acute Respiratory Syndrome
Appeared in Guangdong province, Southern China in late 2002; February
2003 – 305 cases and 5 deaths
Chinese physician spread disease to Hong Kong 21 February 2003
10 secondary-infected guests of the hotel where Chinese physician
stayed carried the infection to Singapore, Vietnam, Canada and the US;
Epidemic raged for more than 100 days; 774 deaths worldwide; A brand
new coronavirus was identified as the culprit
Three independent sequences of SARS coronavirus were identified in less
than a month
July 2004 New Method Enables Researchers to Make Human SARS Antibodies
Quickly
The SARS Genome
+ strand RNA virus; ~29,740 bp genome
SARS in Toronto
During February 23--June 361 SARS cases were reported; 33 (9%) persons
died.
no new cases of SARS in Toronto since June 12, 2003
SARS cost the province of Ontario $84 million in medical costs
alone
The Canadian economy lost an estimated $1.5 billion in lost tourism and
other effects