Quick Review of Microbiology

Dental Caries:  Streptococcus mutans 

- Gram pos. cocci

 Part of normal flora of mouth.  Ferments sucrose ® acid ® dissolves enamel, tooth structures.

  

 Contagious parotitis (Mumps) - Mumps virus

 Virulence:  invades parotid salivary glands, and sometimes brain, meninges, pancreas, testes,       ovaries.  

Common in children before vaccine - epidemics in Fall.  

20-40% subclinical.                

Develop permanent immunity.

Transmission:  Saliva, nasal secretions - direct, indirect contact - not highly contagious.

 Disease:  Inc. pd. 2 - 3 wks. ® virus multiples in nasopharynx ® bloodstream (viremia) ®    invades parotid salivary glands ® acute inflammation.  Accompanied by marked swelling behind ears, difficulty swallowing, fever, headache, pain when eating acetic foods.  

Swelling        reaches maximum in 2 - 3 days (may be unilateral or bilateral ), subsides in       about 1 wk.  Illness more acute in adults.

 Complication:  In children - meningoencephalitis, pancreatitis.  In adult males - orchitis (may    cause sterility).

 Vaccine:  MMR - viable attenuated virus

Peptic Ulcers of Stomach, Duodenum  -  Helicobacter pylori

 Gram neg. short spiral

 Virulence: Urea (product of protein metabolism) ® ammonia which neutralizes stomach acids.

 Disease: Migrates thru mucus coating of stomach lining ® attaches to cells ® reduces production of mucus ® inflammation.

 Complication: ­ stomach cancer

  

Cholera - Vibrio cholera

 Gram neg., comma shaped

Virulence:  produces potent entero-exotoxin - causes cells m.m. of GI tract to lose large amts. fluids (up  to 22 L/day) ® severe electrolyte imbalance.

 Transmission: Fecal-oral route - contaminated H₂O, food

 Disease:  localizes in small & large intestine.  Onset sudden - vomiting, abdominal pain, severe    dysentery.  Stools - cloudy fluids with mucus, organisms ("rice water stools") ® severe    dehydration, electrolyte imbalance.  High mortality rate (60%) - due to shock.

 Carrier state can occur after infection.

  Immunity:  Temporary

  Vaccine: Toxoid - not very effective

              

Bacillary dysentery (Shigellosis) - Shigella species

 Gram neg. bacillus - 4 species pathogenic for man.  S. dysenteriae - most virulent. 

S. sonnei - least virulent, most common in U.S.

   S. dysenteriae - Virulence:  Endotoxins, exotoxins

  Transmission:  Fecal-oral route H₂O, food

  Disease:  Inc. pd. 1-4 d.  Organism localizes in large intestine ® multiplies ® invades m.m.    causing ulceration, bleeding intestinal lining (no perforation) ® severe inflammation ® fluid          loss ® dysentery (stools mostly fluids with blood, pus, mucus), vomiting.  Accom. by fever,       severe abdominal pain, extreme weakness.  Persists approx. 1 wk. - self-limiting.

         Complication:  Can cause severe dehydration, electrolyte imbalance.  Mortality rate high in    infants,            young children.

        No solid immunity.

       Vaccine:  viable, oral - limited use

Typhoid fever (enteric fever) - Salmonella typhi

  Gram neg. bacillus

  Virulence:  Endotoxins (cell wall lipids).  Organisms invade m.m. & other organs ® enteric fever    (begins in GI tract, enters blood, spreads throughout body).

  Transmission:  Fecal-oral route

P/E:  Oral cavity - contaminated food, H₂O

  Disease:  Inc. pd. 1 - 3 wks.  Organism localizes in small intestine ® invades m.m., lymphatic tissues (Peyers patches.  In first week - fever, headache, malaise, diarrhea.  In second week endotoxins cause ulceration intestinal wall (sometimes perforates)     ® bloodstream ® septicemia ® spreads to other organs: (liver, kidneys, spleen, bone marrow, skin, gall bladder).  Symptoms more acute - severe abdominal pain, severe diarrhea with blood, pus, weakness, abdominal distention.  Other symptoms depend on organs     infected. Rose spots in skin - due to multiplication organisms.

  Carrier state: Common following illness.  Organisms remain in gall bladder - must be                   surgically removed to eliminate. Sporadic outbreaks - traced to carriers - food handlers

   Vaccine:  Inactivated (killed) bacteria

    Control:  Proper hygiene, sanitation measures (proper sewage treatment)

                   

 Bacterial Food Poisoning  &  Food Infections                              

                Food Poisoning - Ingestion foods contaminated with exotoxins produced by bacteria (some fungi)     multiplying in food.  Caused by several different organisms.

         Food Infections - Ingestion of foods contaminated with viable organisms. Infect and cause    inflammation GI tract (enteritis).

   Nonfatal Food Poisoning  -  Staphylococcus aureus - Gram pos. cocci - most common

Virulence:  Strain capable of producing entero-exotoxin (exotoxin) - causes inflammation of GI tract.     Exotoxin heat stable (withstands boiling 30 min.), and acid stable.

         Source:  URT, skin human carriers

               Transmission:  Hands - most common vector.  Introduced into food during preparation.  Multiply       in previously cooked, undercooked or uncooked foods (usually ­ CHO) that have been    inadequately refrigerated - custard, cream pies, pastries, dairy products, cream sauces &    gravies, salads            (potato, meat), salad dressings, picnic or lunchbox foods (sandwiches).

Organisms multiply in food ® secrete entero-exotoxin ® food with exotoxin consumed ® exotoxin comes in contact with m.m. GI tract.

               Disease:  Inc. pd. 1-6 hrs.  Severe abdominal pain, vomiting, diarrhea (no fever).  Self-limiting -             lasts 8 -            12 hrs. No organisms isolated from stool; sometimes found in food.

  Botulism (fatal food poisoning) - Clostridium botulinum    

               Gram pos. bacillus, anaerobic, endospores, common in soil & GI track animals

               Virulence:  Potent neurotoxin.  Prevents release neurotransmitter acetylcholene

               P/E:  Introduced in contaminated foods (nonacid canned vegetables, smoked meats).     Processing (does not destroy endospores) ® anaerobic conditions produced ® endospores    germinate ® organisms multiply ® secrete neurotoxin ® consumed with food.  Causes no    change in color, odor, taste of food & can withstand boiling 10 min.

               Disease:  Inc. pd. 2-3 days.  Neurotoxin enters GI tract ® bloodstream ® CNS where interferes           with release acetylcholene ® no impulses transmitted to muscles ® flaccid paralysis

               Onset:  May or may not have GI disturbances ® headache, blurred or double vision ® difficulty             speaking, swallowing ® respiratory failure ® convulsions ® death.  Mortality rate 60 - 70%.

               Vaccine:  none

                           Antiserum available - only neutralizes toxin in bloodstream.

Infant botulism

               Infants consume endospore (ex: in honey) ® germinates in GI tract due to lack normal flora ®           produces neurotoxin ® blood ® CNS

Food Infection (Bacterial Enteritis) - Salmonella sp. (enteritidis, typhimurium)  

               Gram neg. bacilli.

         Virulence:  Endotoxins (cell wall lipids)

               Source:  GI tract animals: i.e., poultry, pork, pets, turtles, sometimes human carriers.

                           Meats - infection due to inadequate cooking.  Other foods infected during preparation - by        hands, utensils, cutting boards, etc.

               Disease:  Inc. pd. 8-36 hrs.  Organisms invade and damage intestinal mucosa ® inflammation.     Accomp. by abdominal pain, vomiting, diarrhea, fever.  Self-limiting - lasts several days       (approx. 3 days). Organism can be isolated from stool, food.

         Carriers common following infection.

Gastroenteritis (Travelers diarrhea, Infantile diarrhea)  -  Escherichia coli

               Gram neg. bacillus, lactose +, normal flora. 

               Virulence: Certain strains capable producing infections due to: 

                           1) Ability to produce enterotoxin (exotoxin) ® fluid loss. 

                           2) Ability to attach to and invade MM. ® endotoxins ® cell death ® inflammation.

               Diseases:  Traveler's diarrhea - consumption food, H₂O.  Varies in severity - diarrhea, vomiting. 

                                                               Self limiting.

                                           Infantile diarrhea - occurs in newborns (due to lack normal flora), young infants.                                                               Highly contagious - spreads rapidly in newborn nursery.  Transmission usually                                                     hands of employees.  Causes severe diarrhea, quickly dehydrates newborn.                                                    Can invade blood ® meningitis resulting in brain damage, death.

               Practical value:  used as indicator of fecal contamination water, milk, or inadequate sewage    treatment. Test further to identify any pathogens present.

Viral enteritis - Rotaviruses, ECHO, Coxackie, Norwalk viruses

               Large # viruses can infect m.m. GI tract ® diarrhea, vomiting, etc. - "intestinal flu or stomach flu."      Usually self limiting.  More severe in infants.

Hepatitis - Hepatitis Viruses

       Types:  A, B, C, D

       Virulence:  Invades cells of liver ® necrosis, inflammation

                           Type A:  Infectious hepatitis.  Transmitted by fecal-oral route - contaminated food                                               (shellfish), water. Can occur in epidemics

                                              P/E:  Oral cavity.  Inc. pd. ave. 30 d.

   Type B:  Serum hepatitis.   Transmitted by - body secretions (blood ,semen, vaginal secretions).

                           P/E:  Parenteral (tissues) - contaminated needles; anal or oral sex. Inc. pd. ave. 90 days.  Can cause chronic infections.

   Type C:  Post-transfusion hepatitis - Contaminated blood transfusion.  Inc. pd. up to 6 mo. Disease:  Spreads from P/E ® blood ® invades liver (A-spleen, kidneys; B-     lymphoid) ® causes necrosis, inflammation ® enlarged, tender liver ®        malfunctions.  Accom. by    fever, nausea, abdominal tenderness, jaundice,   weakness.  Persists several weeks ® recovery prolonged.  Milder in young children.

         Carrier state - following infection.

         Complication: In cases of chronic infections with B, ­ incidence liver cancer.

         Prevention:  If exposed to A - gamma globulin.  Not effective for B.

         Vaccine:  B - antigenic determinants produced by recombinant DNA techniques.  Required for    health care workers.

 Giardiasis - Giardia intestinalis

         Protozoan - flagellated 

         Transmission:  Fecal-oral route - ingest cysts in food, water.

               Disease:  Cysts release trophozoites ® small intestine ® attaches to wall (adhesive disc) ®    inflammation, diarrhea, blocks absorption of nutrients.

                           Becoming more common in U.S. lakes, etc.

Amoebic Dysentery - Entamoeba histolytica

        Protozoan - amoeba

       Transmission:  Fecal-oral - ingestion of cysts in food, water

         Disease:  Cysts ® trophozoites ® intestinal tract ® invade mucosa ® ulceration ® severe    diarrhea, abdominal pain, etc.

 Tapeworm infections - Taenia saginata - beef tape worm,  Taenia solium - pork tape worm.

       Life cycle:  Ingest cysts in raw, poorly cooked meat ® release larvae ® intestine ® develop into adult worms.  Embeds scolex in intestinal wall ® increases in length ® proglottids absorb nutrients leading to malnutrition. Proglottids, eggs deposited in soil ® consumed by animals ® hatch ® larvae encyst in muscles (meat).

Hookworm infections - Necator americanus

       Life Cycle:  Eggs passed in feces ® hatch in moist soil ® free living larvae ® burrow thru skin feet, legs ® blood vessels ® lungs ® coughed up, swallowed ® intestine ® mature into adults ® burrow head into intestinal wall - feed on blood.  Causes abdominal pain, loss           appetite, protein and iron deficiencies (anemia).

Pinworms - Enterobius vermicularis

     Life Cycle:  Eggs ingested, inhaled ® hatch in small intestine ® mature and reproduce in large    intestine - male & female mate ® gravid females migrate to perianal region during night to    deposit eggs on skin.  Causes itching, irritation in area.  Eggs easily spread to family         members - all are treated.  Reinfections common.

GENITOURINARY INFECTIONS

Urinary Tract Infections (UTI's)

        Urethritis - inflammation urethra

        Cystitis - inflammation bladder

        Pyelonephritis - inflammation kidneys

         Usually caused by Gram neg. bacilli of GI tract: (E. coli, Proteus, Pseudomonas, Klebsiella).

         Occur due to:

                           1)  Obstruction that prevents complete emptying of bladder - scarring urethra, compression                              bladder by uterus, enlarged prostate, paralysis, deformity sphincter muscle, infrequent                                 urination.  Upon standing pH urine neutralizes, can serve as reservoir for microbial                                       growth.

               2)  Nosocomial infection due to poor asepsis while inserting catheter or other instrument into urethra, bladder.

               Identification:  urinalysis, urine culture

Toxic Shock Syndrome TSS - Staphylococcus aureus

               Gram pos. cocci

Virulence:  Strain causing TSS produces an exfoliation exotoxin (scalded skin syndrome) and    entero-exotoxin (diarrhea, shock).

               Transmission:  From URT, skin of carriers.  Hands most common vector ® tampon ® vagina.

               Disease:  Organism ­ in numbers in blood & abrasions in m.m. of vaginal wall ® secretes toxins     ®        bloodstream.  Causes sunburn-like rash on skin ® skin and m.m. separate and slough    off ® inflammation.  Also accomp. by severe vomiting, diarrhea.  Blood pressure ¯, shock          ® can be fatal.

               Prevention:  Washing hands before handling, insertion of tampon; avoiding use of tampons.

                           Has also occurred in males following surgery, or with boils or other Staph infections.

SEXUALLY TRANSMITTED DISEASES

Gonorrhea - Neisseria gonorrhea

               Gram neg. diplococci, bean-shaped with indented sides facing

               Virulence:  Encapsulated, pili, endotoxins, catalase, intracellular parasite.

               Transmission:  Direct contact - sexual contact

               P/E:  M.m. of genitourinary tract: i.e., vagina, urethra in males.

               Disease:  Adheres to and invades m.m. ® causes damage to m.m. lining ® inflammation.

                           In males usually more acute - painful voiding, purulent discharge from urethra.  Can spread                to vas deferens, testes causing scarring, infertility.  Scarring in urethra leads to frequent                         UTI's.

                           In females infection often low grade, asymptomatic (chronic).  Spreads to uterus, cervix,                                        fallopian tubes, ovaries.  Scarring of fallopian tubes ® sterility.

               Identification:  Direct smear exudate - observe Gram neg. diplococci in PMN's                       follow with culture.

              
Complications:  Gonococcal Opthalmia Neonatorum

                           Infection of eyes of newborn - exposed during birth if organisms present in birth canal.                                         Causes destruction, scarring cornea ® blindness.  Prevent:  treat eyes with 1% silver                                    nitrate, antibiotics following birth.

                           In adults, bacteria can be transferred from genitals to eyes by hands, also see fig. pg. 606.

Syphilis - Treponema pallidum

               Gram neg. spiral, very small, tightly-coiled

               Transmission:  Direct contact - sexual intercourse, occasionally kissing.

               P/E:  M.m. genitourinary tract (occas. mouth).

               Disease:  Inc. pd. - 3 wks. ave.  Disease occurs in stages: 

                           1) Primary stage:  Usually single lesion - chancre - ulcer-like, about 1/2 inch dia.,                                                      asymptomatic .  Self limiting - heals after several (4-6) wks.  May                                                                              remain free of symptoms 2 wks. - several mo. before next stage. 

   2)  Secondary stage:  Multiple lesions occurring on skin, m.m. on face, in and around mouth, palms of hands, soles of feet, external genitalia.  Heals in few wks., but can recur over period of 2 - 5 yrs.  Accom. by fever, enlarged lymph nodes, malaise.  Then individual may remain free of symptoms (latent) 5 - 40 yrs. 

                           3)  Tertiary stage:  Internal lesions produced in bone, cardiovascular, CNS. Called gummas                                    - abscess-like lesions with central rubbery mass surrounded by connect. tissue -                                                probably develops due to delayed hypersensitivity.  Leads to crippling, aneurysm,                                       insanity, paralysis.  In this stage not very infectious.  This stage seldom seen today                                due to effective treatment.

               Complications:  Can cross placenta, infecting fetus ® congenital syphilis.  Causes congenital                            deformities or death.

               Identification:  Demonstration organism in exudate from lesions, serological tests.  Organism                                                                cannot be grown in lab.

Nongonococcal Urethritis (NGU) - Chlamydia trachomatis

               Virulence:  Obligate intracellular parasite (cannot produce ATP, leaky membrane)

               Transmission:  Sexual intercourse

               P/E:  m.m. genitourinary tract

               Disease:  Resembles gonorrhea, but milder.  Infects m.m. of vagina, urethra.  Low grade, scanty,  watery discharge.  May also be asymtomatic, causing chronic infections.  Can eventually cause scarring and infertility in males and females.

               Complication:  In pregnant females, can infect fetus causing death, congenital deformities.

               NGU is becoming more prevalent than any other sexually-transmitted disease.

 Herpesvirus Infections - Herpes simplex, type I, type II

         I - Recurrent fever blisters; II - Genital herpes.  Either virus can cause either infection.

               Virulence:  Invades m.m. ® ulcer-like lesion

               Transmission:  Direct contact, rarely indirect

               Type I:  Transmitted by oral nasal secretions

               P/E:  Oral m.m., skin

               Disease:  Painful vesicular lesions on m.m., skin ® shallow ulcer ® self limiting, heals     in 2-3 wks.  Virus remains in state of lysogeny in trigeminal nerve ganglia. Can be reactivated by trauma, UV, hormonal changes, etc.

               Type II:  Transmitted by sexual intercourse

               P/E:  genital m.m., skin

               Disease:  Painful vesicular lesion occurring on m.m., skin of genitalia, vagina ® small ulcer, self limiting, heals in several weeks.  Virus remains in latent state in spinal ganglia.  Can be reactivated by hormonal changes, stress, febrile illness, etc. 

               Complication:  Herpes encephalitis (neonatal herpes) in newborn. Can be transmitted to newborn in nursery by worker with fever blister, or from infected mother (active lesion in vagina)  during     birth; C-section recommended.  Infected newborns have high mortality rate, survivors have severe neurological damage.

                           Increased incidence cervical cancer in females with genital herpes.

   

Genital Warts (Condylomas) - Papilloma viruses

               Transmission: Sexual intercourse; increased incidence in sexually-active teens, young adults.

               Disease:  Warts occur on penis, anus or perineum in males, in females - vagina, cervix, perineum, anus. Causes irritation, itching, can become infected with bacteria. If persist can become malignant.

               Complications: Infants can become infected during delivery.

                        In females ­ ­ cervical cancer.

AIDS (ACQUIRED IMMUNODEFIENCY SYNDROME)

HIV (Human Immunodeficiency Virus

   Retrovirus  RNA virus ® DNA during replication
   Virulence: Invades T_H  lymphocytes, macrophages
   Transmission: Sexual intercourse, blood transfusions, shared needles (intravenous drug abusers), mother ® fetus (transplacentally) & nursing infants
    Disease: Virus infects T_H lymphocytes ® provirus permanently incorporated into host cell DNA ® infectious virions synthesized and released ® T_H lymphocyte dies, or is destroyed by cells & antibodies of immune system ® eventual failure of immune system.  Virus may also spread to macrophages ® virus carried to brain, bone marrow, intestinal mucosa
  Onset of Disease: Occurs in 3 stages:
                           1). Inc. pd. 6 days - 6 wks. ® Initial infection flu-like illness or asymptomatic.
                                    May be followed by long asymptomatic period.                                               
                           2). Frequent opportunistic infections: frequent URT infections, nausea, diarrhea, fever,     night sweats, enlarged lymph nodes, fungal skin infections, yeast infections of   gums, mouth, hepatitis, etc.
                           3). Severe opportunistic infections: pneumocystic pneumonia, TB, Toxoplasmosis, CMV, Herpes virus, Kaposi’s sarcoma, systemic fungal infections, brain lesions & dementia, chronic weight loss, muscle wasting syndrome.
        
 Identification: ELISA most widely used test. 

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