Bacteriology (part 1) Flashcards
Occurs when bacteria, viruses, fungi and parasites change over time and no longer respond to medicines making infections harder to treat and increasing the risk of disease spread, severe illness and death (WHO, 2020).
Antimicrobial resistance
Causes of Antimicrobial Resistance
• Over-prescribing of antibiotics
• Patients not finishing their medications
• Over-use of antibiotics in livestock and fish farming
• Poor infection control in hospitals and clinics
• Lack of hygiene and poor sanitation
• Lack of new antibiotics being developed
2 types of toxins
Exotoxin & Endotoxin
Produced by Gram (+) and Gram (-) and Has killed 50,000 soldiers by Clostridium tetani during WWII
Exotoxin
Vaccines made from exotoxins
Toxoids
Produced by Gram (-) bacteria
Endotoxin
Endotoxin produces
fever
hypotension
hypoglycemia
early leukopenia
Contact transmissions
- Direct – person-to-person
- Indirect – Fomite
- Congenital – mother to fetus or newborn at birth
- Droplet – Mucus droplet that only travels short distances
Vehicle transmissions
- Airborne – droplet nuclei in dust that travels more than 1 meter
- Waterborne – contaminated water
- Foodborne – incompletely cooked food, poorly refrigerated or prepared under
unsanitary conditions - Fecal-oral – Microbes enter the water or food after being shed in the feces of
people or animals
Vector transmissions
- Mechanical - fly
- Biological - mosquito & fleas
Types of transmission
Contact
Vehicle
Vector
Spore forming gram (+) bacilli
Bacillus anthracis
Bacillus cereus
Clostridium perfringens
Clostridium difficile
Clostridium botulinum
Clostridium tetani
large, aerobic; strikes primarily grazing animals
Bacillus anthracis
Virulence factors of Bacillus anthracis
Edema toxin
Lethal toxin
Causes local edema and interferes with phagocytosis by macrophages
Edema toxin
targets and kills macrophages
Lethal toxin
Diseases caused by Bacillus anthracis
Cutaneous
•Endospore enters at the minor skin lesion
•Papule appears and then eventually vesicles, which rupture and form a depressed, ulcerated area that is covered by a black eschar
•Mortality rate: 1%
Gastrointestinal
•Ingestion of undercooked food containing anthrax endospores
•S/S: Nausea, abdominal pain , bloody diarrhea
•Mortality rate: 50%
Inhalational
•S/S:
1st day: mild fever, coughing, some chest pain
2nd-3rd day: bacteria enter the bloodstream and proliferate; septic shock that usually kills the patient within 24 to 36 hrs.
•Mortality rate: 100%
Treatment for anthrax
Doxycycline
Ciprofloxacin
Raxibacumab
large, endospore-forming bacterium that commonly contaminates rice; when large amounts of rice are cooked and allowed to cool slowly, the B. cereus germinate and the vegetative cells produce toxin during sporulation
Bacillus cereus
Two Distinct Forms of Bacillus cereus
Emetic type: NV, abdominal cramps, occasionally diarrhea and is self- limiting with recovery occurring within 24 hours
Diarrheal type: profuse diarrhea with abdominal pain and cramps; fever and vomiting are uncommon; due to enterotoxins
Tx for Bacillus cereus
•Vancomycin and Clindamycin
•Ciprofloxacin for wound infections
Bacillus cereus is resistant to a variety of antimicrobial agents such as
Penicillins and Cephalosporins
Prevention for B. cereus
cook food thoroughly and cool rapidly
endospore-forming, obligately anaerobic rod; endospore survive most routine heating; grows in the intestinal tract and produces exotoxin that causes the typical symptoms of abdominal pain and diarrhea
Clostridium perfringens
Disease caused by Clostridium perfringens
Gas Gangrene
Causes of Clostridium perfringens
Improperly performed abortions
Contaminated wound
S/S: spreads in 1-3 days, crepitation in the SC tissue and muscle, foul-smelling discharge, rapidly progressing necrosis, fever, hemolysis, toxemia, shock, death
Clostridium perfringens
Tx for Clostridium perfringens
Amputation
PCN
Symptomatic care – food poisoning Hyperbaric chamber
MADLI TOF MS means
Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS)
Prevention for Clostridium perfringens
Early and adequate cleansing of contaminated wounds; surgical
debridement
Characteristics of Clostridium difficile
Endospore-forming anaerobe found in the stool of many healthy adults
Disease cause by Clostridium difficile
Pseudomembranous colitis
Inflammation of the large intestine
Pseudomembranous colitis
Cause of disease under clostridium difficile
Extensive use of antibiotics such as Ampicillin, Clindamycin and more
frequently Fluoroquinolones
Eliminates most of competing intestinal bacteria and permits rapid proliferation of the toxin
Results in proliferation of drug resistant C. difficile
S/S disease under Clostridium difficile
water or bloody diarrhea, abdominal cramps, leukocytosis, fever
Tx/Management under Clostridium difficile
•Discontinue administration of offending antibiotic
•Give oral Metronidazole, Vancomycin or Fidaxomicin
Characteristics of Clostridium botulinum
found in soil and occasionally in animal feces; highly resistant to heat, withstanding 100°C for several hours; heat resistance is diminished at acid pH or high salt concentration
Toxins under Clostridium botulinum
o 7 varieties of toxin (serotypes A-G)
o Type A, B, E and F causes human illness o Most toxic substance known
o Lethal dose – 1-2 μg/kg
Sources Clostridium botulinum
from spiced, smoked, vacuum packed or canned alkaline foods
that are eaten without cooking; improperly canned, preserved or
fermented foods
Source of infant botulism
Honey
Source of wound botulism
Seen primarily in drug users
S/S under Clostridium botulinum
Flaccid paralysis (toxin blocks release of acetylcholine at the synapses and
neuromuscular junctions)
Inability to swallow, speech difficulty, visual disturbances, death occurs
from respiratory paralysis or cardiac arrest
Infant develop poor feeding, weakness and signs of paralysis (floppy baby)
Treatment and Prevention for Clostridium botulinum
•Supportive care, especially intensive care; mechanical ventilation if
necessary
•Canned or preserved foods must be sufficiently heated to ensure
destruction of spores or must be boiled for 20 minutes before consumption
Characteristics of Clostridium tetani
found in soil and in the feces of horses and other animals; extremely small amount of toxin can be lethal for humans
Disease caused by Clostridium tetani
Tetanus
Spores are introduced through a devitalized tissue (wound, burn, injury, umbilical stump, surgical suture)
Toxin reaches the CNS and becomes fixed to the receptors in the spinal cord
S/S under Clostridium tetani
c. S/S:
o Trismus, lockjaw where mouth cannot be opened, sardonic smile
o Opisthotonos (spasm of the back muscles cause the head and heels to
bow backward)
o Tonic spasms then tetanic generalized muscle spasm
o Patient is fully conscious and pain may be intense; death occurs due to
interference with the mechanics of respiration
Prevention and treatment under Clostridium tetani
o Active immunization with toxoids (tetanus toxoids) o DTaP vaccine
o Aggressive wound care
o Prophylactic use of antitoxin
o Administration of PCN
o Muscle relaxants, sedation and assisted ventilation
DTaP means
Diphtheria Tetanus Pertussis
Aerobic Non-Spore Forming Gram (+) Bacilli
Corynebacterium diphtheria
Listeria monocytogenes
Erysipelothrix rhusiopathiae
Nocardia genus
“club-shaped” appearance; occurs in the respiratory tract in wounds or on the skin of infected persons or normal carriers
Corynebacterium diphtheria
Disease caused by Corynebacterium diphtheria
Diphtheria
Causes/Transmission of Diphtheria
droplet infection, unvaccinated individuals and developing countries
S/S of Diphtheria
o Begins with a sore throat, fever followed by general malaise and swelling of neck
o Formation of tough grayish membrane that forms in the throat which contains fibrin, dead tissue and bacterial cells and can totally block the passage of air to the lungs
Tx for Diphtheria
Penicillin & Macrolides
Prevention of Diphtheria
DTaP vaccine – an inactivated toxin that causes the body to produce antibodies against the diphtheria toxin
can survive at refrigerator temperature (4°C) under conditions of low pH and high-salt conditions; can overcome food preservation barriers; produces acid but not gas from utilization of variety of carbohydrates
Listeria monocytogenes
Disease caused by Listeria monocytogenes
Granulomatosis Infatiseptica; Listeriosis
Transmission under Listeria monocytogenes
ready-to-eat meat; contaminated food
S/S under Listeria monocytogenes
o Adult – causes meningitis for immunocompromised patients; can cause sepsis
o Pregnant woman – mother suffers no more than mild flu-like symptoms; fetus can be infected resulting in an abortion or stillborn infant; meningitis in infant resulting to death
Tx for Listeria monocytogenes
Ampicillin, Erythromycin
IV Trimethoprim-Sulfamethoxazole – DOC for CNS infections in patients
who are allergic to PCN)
produces small, transparent glistening colonies; alpha- hemolytic on blood agar; on gram stains, it sometimes looks garm (-) because it decolorizes easily
Erysipelothrix rhusiophathiae
Disease cause by Erysipelothrix rhusiophathiae
Erysipeloid
Treatment under Erysipelothrix rhusiopathiae
o Pen G
o It is intrinsically resistant to vancomycin
produce urease; cell walls contain mycolic acid; weakly acid fast
Nocardia genus
Disease caused by Nocardia genus
Nocardiosis – opportunistic infection with several risk factors; impairs
cell-mediated immune responses
o Risk factors: Corticosteroid treatment, immunosuppression, organ
transplantation, AIDS, alcoholism
Transmission of Nocardiosis
Transmission: inhalation, not transmitted from person-to-person
S/S of Nocardiosis
o subacute to chronic pulmonary infection that may disseminate to other organs
o Fever, night sweat, weight loss, chest pain, cough with or without sputum production, SOB, abscess formation
Treatment for Nocardiosis
o DOC: Trimethoprim—Sulfamethoxazole (TPM-SMX)
