CONTROL OF MICROBES

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• CONTROL OF MICROBES

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• A. Microbicidal agents kill microbes
• B. Microbistatic agents inhibit microbes.
• C. Germicidal microbicidal
• We can further divide these chemicals
  bactericidal or bacteristatic, fungicidal or
  fungistatic, and virucidal or virustatic.

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Some mechanisms of microbial control

• Sterilization - the elimination of all forms of
  the life cycles of microbes (e.g., vegetative
  cells, spores). Toxins and prions however, are
  not necessarily removed.
• Disinfection - the reduction of the vegetative
  forms of most potentially hazardous and
  pathogenic microbes from inanimate objects.
• Sanitization - a supplemental disinfection by
  cleaning that is used for food preparation
  equipment.
• Antisepsis - the inhibition or destruction of
  microbes on the surfaces of living organisms.
• Decontamination - the inactivation or removal of
  both toxins and microbes.
• Preservation the process that delays spoilage
  (food and other perishables).
• Degerming- decreasing the number of microbes in
  an area.

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The ideal disinfectant

• Would be fast acting
• Would be broadspectrum w/o causing damage to the
  person
• Would easily penetrate material to be disinfected
  without damaging it.
• Would be easy to prepare, and would be stable
  despite exposure to light, heat, and other
  environmental factors
• Would be cost efficient and easy to obtain and
  use
• Would not have an unpleasant odor

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Factors that affect the activity of antimicrobial
agents

• includes types of microbes
• number of microbes
• concentration of the antimicrobial
• time of exposure
• risk of infection
• environmental conditions

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• PHYSICAL WAYS TO CONTROL MICROBES

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HEAT

• 1. Pasteurization - the use of mild heat for
  relatively long periods of time or the use of
  high heat for very short periods of time.
• 2. Boiling for 10 minutes at 100 C eliminates
  most vegetative cells.
• 3. Autoclaving is a common method of
  sterilization (see fig. 5.3). It is the use of
  steam under pressure. The pressure increases the
  boiling point of water and thus increases the
  temperature to which water can be heated.
• 4. Dry heat involves three methods flaming,
  incinerating, or baking.

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RADIATION

• 1. Ionizing radiation (e.g., gamma rays, X-rays)
  involves rays that have such high energy that
  they cause biologically active molecules to lose
  electrons. High doses kill every organism they
  strike. It can be used for sterilization.
• 2. UV radiation causes the formation of
  pyrimidine dimers.

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OTHER METHODS

• Filtration
• The Mechanical Scrub
• Cold temperatures slow microbial growth
• Desiccation (drying out) is effective against
  many vegetative cells
• High Pressure processing is a relatively new way
  of pasteurizing foodS

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• CHEMICAL METHODS OF CONTROLLING MICROBES

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• chemicals that sterilize (see Table 5.2). Very
  few chemicals are recommended for sterilization.
  These include ethylene oxide, hydrogen peroxide,
  formaldehyde, and gluteraldehyde
• Disinfectants and Antiseptics
• Chemical preservatives

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• ANTIBIOTICS

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• Considerations for choosing an antibiotic
• 1. The antibiotic must be soluble in body
  fluids to be transported in the body or be
  dissolved in the fluids of injured tissues.
• 2. Selective toxicity is a critically important
  property of abs. The therapeutic index is the
  dose per kg of body wt./the minimum dose per kg
  of body wt. that will cure the disease (the
  higher the TI, the better). The Therapeutic
  index is the highest dose a patient can tolerate
  without toxic effects, divided by the dose
  required to control a microbial infection.
• 3. Interactions with other substances (
• 4. Allergic reactions
• 5. Stability
• 6. There should be minimal resistance to the
  drug
• 7. Long shelf life
• 8. Affordable.

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Other drugs for other infections

• Antivirals
• Antifungals
• Antiparasitic
• etc

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• INFECTIONS OF THE SKIN

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SKIN
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NORMAL FLORA

• Staphylococci
• Diptheroids
• Fungi

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Folliculitis (infections of hair follicles small
bumps or pimples) furuncles (AKA boils, when
infection of hair follicle spreads to adjacent
tissue, see figure 19.5), and Carbuncles (a group
of boils).

• Causative organism(s) - Staphylococcus aureus
• These infections are not always limited to the
  cutaneous and subcutaneous tissues and can lead
  to very serious conditions such as septicemia
  (blood poisoning).
• diagnosis - the presence of the infected tissues
• treatment - drainage of the pus and antibiotics
  (topical or systemic)
• prevention is difficult because of the ubiquitous
  nature of S. aureus

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Folliculitis
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Furuncles
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Carbuncles
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Staphylococcal Scalded Skin Syndrome AKA Ritters
disease

• Causative organism- S. aureus (5 of strains)
• A painful red flush over the body (covering
  20-100) which blisters followed by the sloughing
  of the skin. Other symptoms include malaise,
  irritability, and fever. This disease is very
  serious and mortality may be as high as 40
  depending on how promptly the disease is
  diagnosed and the patients age and general
  health. It involves the production of toxins.
  Newborns, the elderly, and the immunocompromised
  are more susceptible and secondary infections are
  possible.
• diagnosis - Gram stain and culture from the
  primary site of infection or from blood, skin, or
  nose (but not the blister fluid)
• treatment - antibiotics, and removal of dead
  tissue.
• prevention no prevention except isolation of
  patient

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Staphylococcal scalded skin syndrome
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Streptococcal impetigo

• Causative organisms -Streptococcus pyogenes ( but
  also can be caused by S. aureus)
• Pyodermas are skin infections characterized by
  pus production and the most common type of this
  skin infection is impetigo. Impetigo can result
  for infection of an insect bite, burn, scrape or
  other wound. It is most prevalent among poor
  children of the tropics or elsewhere during the
  hot, humid season. It is characterized by the
  formation of blisters which open and weep causing
  a buildup of yellow crusts (see figure 22.6).
  These infections are usually found in children
  2-6 years of age and are generally not too
  serious, but are very contagious person to person
  or by fomites, however, a rare but very serious
  sequel can occur Acute Glomerulonephritis
  (figure 22.7)
• diagnosis- culture of fluid from lesions or
  lesions
• treatment - oral or topical antibiotic,
  anti-itch creams
• prevention- good hygiene, prompt cleaning of
  wounds and avoiding people with pyodermas.

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Impetigo
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Rocky Mountain Spotted Tick Fever

• Causative organism - Rickettsia rickettsia (an
  obligate intracellular pathogen Gram negative
  coccobacillus), vector ticks of the genus
  Dermacentor.
• This zoonosis is characterized by a serious
  headache, muscle and joint pain, and fever,
  followed by a distinctive spotted rash (figure
  22.8) that develops starting on the wrists and
  ankles and moving to the arms and legs and
  eventually covering the entire body. In severe
  untreated cases, gangrene may develop, as well as
  cardiovascular disruption, delirium, convulsions,
  deafness, DIC, and coma. This disease can be
  rapidly fatal and thus rapid diagnosis is
  critical. Mortality without treatment is _at_ 20
  but with early treatment it is reduced to less
  than 5. See distribution figure 22.10 and tick
  22.11
• Diagnosis - fluorescent antibody staining,
  serological methods, DNA probe, or sometime early
  biopsies. It is hard to grow and moreover it is
  dangerous to culture.
• Treatment early antibiotics (even without
  confirmation based on rash and other symptoms)
• Prevention - avoidance of ticks, using
  repellents, wearing protective clothing,
  carefully inspecting the body for ticks and
  carefully removing any that are found (without
  crushing them). No vaccination is available but
  one is under development

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Rocky Mountain Spotted Tick Fever
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Lyme disease

• Causative organism - Borrelia burgdorferi, a
  large microaerophilic spirochete, vector- tick
  (genus Ixodes)
• The disease is not normally fatal but can be
  disabling. It is a zoonosis that is
  characterized by three phases. The first phase
  involves a rash at the site of the bite erythema
  chronicum migrans that looks like a bulls eye
  (present in 2/3s of the cases), figure 22.12,
  and flu-like symtoms fever, enlarged lymph
  nodes, headache, joint and muscle pains, and
  stiff neck. The second phase (after rash, 2-8
  wks later) is characterized by neurological and
  cardiovascular involvement (due to impairment of
  the conduction system and thus sometimes
  requiring a pace maker temporarily) and may be
  characterized by dizziness and fainting and one
  or more of the following paralysis of the face,
  severe headache, pain on moving the eye,
  emotional instability, concentration problems,
  fatigue, and impairment of nerves of the arms and
  legs. The third phase, if it develops involve
  joint pain, arthritis, swelling and tenderness
  about 6 months after the ECM. In 60 of cases,
  chronic nervous system impairments occur
  (localized pain, paralysis, and depression) See
  figures 22.14-22.16
• Diagnosis - Serological testing, also erythema
  chronicum migrans is diagnostic when present
• Treatment - early treatment with antibiotics
• Prevention see above. There is a vaccine, but
  it is recommended only for those at high risk.

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Lyme Disease
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Chicken pox or varicella

• Causative organism - Varicella-zoster virus (a
  herpesvirus dsDNA, unique in that it has a
  linear chromosome in multiple copies)
• Chicken pox is usually mild but more serious in
  adults and characterized by the presence of a
  rash beginning as small, red macules (spots),
  papules (bumps), and vesicles (blisters) that
  itch. In adults the symptoms are more severe and
  pneumonia may develop (in about 20 of cases).
  In addition, if a pregnant woman gets chicken pox
  five prior to and up to two days after birth, the
  newborn may have serious complications
  (congenital varicella syndrome). Also infection
  earlier in pregnancy may result in congenital
  varicella syndrome. If the virus becomes latent
  and is then reactivated, shingles or herpes
  zoster (figure 22.18), which involves a rash and
  pain that may last for months occurs. The
  incidence was previously as high as 3.7 million
  cases/year, but has decreased since the vaccine
  became available. Humans are the only
  reservoirs.
• Diagnosis - characteristic rash, fluorescent
  antibody tests, and culture
• Treatment - anti-itch medicines (without aspirin)
  and if severe, acyclovir, also ZIG zoster
  immunoglobulin can partially protect a patient
  from serious disease if immunocompromised.
• Prevention vaccination for healthy children but
  not for the immunocompromised (they can receive
  antibodies instead upon exposure)

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Chicken pox
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Rubeola (hard or red measles).

• Causative organism - a paramyxovirus, ssRNA virus
• Measles is characterized first by a fever, runny
  nose, cough, and swollen, red, weepy eyes and
  then a rash develops. The portal of entry is the
  respiratory system. Although the disease
  normally is self-limited (duration about one
  week), secondary infections (e.g., pneumonia and
  otitis media) often develop and occasionally the
  virus itself causes a pneumonia (5 of cases).
  Rarely, an encephalitis forms which results in
  permanent brain damage. Another rare sequel is
  subacute sclerosing panencephalitis which occurs
  2-10 years after the initial infection and which
  is characterized by a slow degeneration of the
  brain resulting in death within 2 years. In
  addition, measles during pregnancy increases the
  chance of miscarriage, premature labor and low
  birth weight but does not cause birth defects.
  In the U. S. there are now fewer than 100
  cases/year and a decline world-wide has resulted
  in a low of 30 million cases and 8o0,000 deaths
  annually. Thus it is on the decline but it was
  hoped to have been eradicated. It is highly
  contagious. In the US, death occurs in about 1-2
  of every 1,000 cases, but worldwide the mortality
  rate is much higher (15 and even 85 if there
  are complications from secondary infections).
• Diagnosis - serological methods or culture,
  presence of Kopliks spots usually in the mouth
  (see figure 22.21).
• Treatment - treat symptoms, antibiotics if
  secondary infections develop
• Prevention vaccination. There is hope that
  this disease will be eradicated by 2015

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Rubeola
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Rubella (German measles or three day measles.

• Causative organism - a togavirus
• Rubella is normally a mild disease characterized
  by mild cold like symptoms and a rash. The
  portal of entry is the respiratory system. The
  major complications involve effects on the fetus
  of infected moms. Congenital rubella syndrome
  involves combinations of the following
  cataracts, brain damage, deafness, heart defects,
  stillbirth. These babies are also reservoirs for
  infection. Rubella is highly contagious. Humans
  are the only natural hosts. Currently there are
  less than 250 cases annually in the US.
• Diagnosis - tissue cultures and serology but it
  is difficult to diagnose
• Treatment - treat symptoms
• Prevention vaccination

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Rubella
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Warts
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Cutaneous mycosis
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Fifth disease
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Roseola
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Small pox