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