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33 Cards in this Set
- Front
- Back
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Anaerobes
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• Anaerobes represent 5-10% of all clinical infections.
• Anaerobic infections usually have the following characteristics: • foul smelling discharge • proximity to mucosal membrane • necrotic tissue • gas formation in tissues or discharge • infection following a bite Anaerobic organisms require an oxygen free environment to grow normally Gram Positive Rods |
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CLOSTRIDIUM:
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• C. tetani, C. difficile,
• C.perfringens, and C. botulinum • General Characteristics of Clostridium: Spores • ubiquitous - especially found in soil • bacteria secrete powerful exotoxins that are responsible for such diseases as tetanus, botulism, and gas gangrene. • Anaerobic to aerotolerant Gram-positive and Gram-variable rods • Common in intestinal tracts of humans and domestic and wild animals • Spore forming • terminally, subterminally, or centrally located • extremely resistant • disinfectants & drying • can persist in environment for years • infection often begins with introduction of spores |
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Clostridium tetani
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• tetanus (lockjaw) in humans
• spores can be acquired from any type of skin trauma involving an infected device • Exotoxin - tetanospasmin • constant skeletal muscle contraction due to a blockage of inhibitory interneurons that regulate muscle contraction • leads to respiratory failure • Immunization four shots followed up with periodic booster shots given every ten years. |
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Clostridium botulinum
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• produces one of the most potent toxins in existence and cause of the deadly botulism food poisoning
• Clostridium spores can be airborne, they sometimes find their way into foods that will be placed in anaerobic storage such as cans or jars. Once the jars are sealed, the spores germinate and the bacteria release their potent toxin. • spores can be killed by boiling in hot water for 30 minutes. • toxins may be destroyed by moist heat at 80oC for the same period • Symptoms appear at about 18 to 36 hours after ingestion. |
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Infantile botulism
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• acquired from ingestion of honey or corn syrup and is the source of the spores which germinate in the child's intestinal tract.
• Bacterial proliferation and subsequent toxin production cause symptoms which last a few days and then subside without the use of an antitoxin. • The spores may be found in soil and certain foods (such as honey and some corn syrups). • This disease occurs mostly in young infants between 6 weeks and 6 months of age. Onsets as early as 6 days and as late as one year have been reported. |
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Symptoms of Infantile botulism
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• Infant appears "floppy"
• Tired all the time (lethargy) • Weak cry • Poor feeding and weak suckling • Loss of head control • Infant doesn't gag • Respiratory distress • Eyelids sag or partially close ( ptosis) • Paralysis that spreads downward • Respiratory failure • constipation |
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C. Botulinum: toxin
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• muscular paralysis
• blurred vision. • treatment with an anti-toxin • Use of toxin in therapy • Botox |
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CLOSTRIDIUM BOTULINUM
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• The toxin may affect the central nervous system and disturbs the nerve impulses
• difficulty in walking and swallowing, impaired vision and speech to occasional contraction of the muscles and finally paralysis of the respiratory muscles, suffocation, and death. • These symptoms can all occur within a few hours or days, depending on the amount of toxin taken. Botulism antitoxin can be used to cure this disease if treatment is given early. |
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C. perfringens
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• non-motile bacterium
• invasive pathogen • contracted from dirt via contaminated wounds. • cells proliferate after spore germination occurs • release their exotoxin. Many toxins produced (more than 20) - hemolysins, collagenase, proteases - hyaluronidase, DNase, lecithinase - neuraminidase, lipase, others |
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Gas Gangrene - Alpha toxin
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• Produced by nearly all strains/isolates
• Phospholipase C/sphingomyelinase C • Hemolytic (incomplete outer zone, with theta toxin causing inner zone) • Lethal in mice, dermonecrotic in guinea pigs |
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Gas Gangrene - Beta toxin
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• Pore-former
• Causes intestinal necrosis • Diffuses from intestine to cause toxemia Lethal, dermonecrotic • toxin causes necrosis of the surrounding tissue • The bacteria themselves produce gas which leads to a bubbly deformation of the infected tissues. |
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Clostridia causing Enteric Disease
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• C. perfringens is capable of necrotizing intestinal tissues and can release an enterotoxin that may lead to severe diarrhea.
• Enterotoxic in vivo: fluid accumulation with tissue damage (blood and mucus), cells can no longer control water movement • Causes diarrhea, intense inflammatory response when fed to hamsters • Associated with human food poisoning and diarrhea in domestic animals • Produced during sporulation |
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Cl. Perfringens
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• Wound contamination
• environmental organisms into surgical incisions, wounds, not causing infection • Anaerobic cellulitis • spores introduced into open wound • germinate, multiply rapidly • produce cellulitis in fascial planes: crepitus • local pain, edema, toxemia, healthy muscle not invaded |
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Therapy of Gas Gangrene
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• surgical intervention, antibiotics
• vaccine for high-risk populations • Hyperbaric chamber – promote healing, high levels of oxygen to inhibit growth of anaerobic organisms |
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Clostridium difficile
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• part of the natural intestinal flora - are colonized with C. difficile,which in healthy persons is metabolically inactive in the spore form. The assumption is that perturbation of the competing flora promotes a conversion to vegetative forms that replicate and produce toxins. The characteristic clinical expression is watery diarrhea and cramps, and the characteristic pathologic finding is pseudomembranous colitis.
• Infection occurs through the use of broad-spectrum antibiotics which lower the relative amount of other normal gut flora. C. difficile proliferates and infects the large intestine. Fluorquinolones and clindamycin • two enterotoxins that destroy the intestinal lining • cause diarrhea • The preferred method of treatment is vancomycin. • severe abdominal pain • water, nonbloody diarrhea • high number of neutrophils in stool |
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Pseudomembranous Colitis: Source
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• feces of nondiarrheic humans: 5- 10%
• hospital environment: up to 40% of patients • soil, marine sediments (mostly spores) • Disruption of intestinal flora by antibiotics, chemotherapeutics • clindamycin: most cases per amount used • ampicillin, cephalosporins: most commonly associated (more widely used) |
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C. difficile
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• Antibiotic levels fall, C. difficile grows rapidly in unoccupied niches
• Onset 4 - 10 days after start of antibiotic, up to 2 weeks after termination • Vegetative cells produce toxins • Damage to colonic mucosa • accumulation of fibrin, mucin, dead host cells (yellowish layer on surface = pseudomembrane) • separate lesions coalesce • detection of the organism: • culture of feces for C. difficile(48-72h) • immunological assay for somatic antigens • detection of toxins: tissue culture |
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Outcome and Treatment C. difficile
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• Affects 3.5 million North Americans /year
• Fatality rate: 27-44% if untreated • Treatment - cessation of antibiotic, if possible - treatment with anti-C. difficile-drugs: vancomycin, metronidazole - extended course may be required to prevent recurrence - restoration of normal intestinal flora - Prophylaxis - feeding of Saccharomyces boulardii (nonpathogenic yeast) - administration of toxin-neutralizing antibodies |
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- Prevention efforts should include fastidious use of barrier precautions, isolation of the patient, careful cleaning of the environment with sporicidal agents active against C. difficile, and fastidious use of hand hygiene. This last requirement should include washing hands with soap and water as a supplement to the use of alcohol-based sanitizers, since such sanitizers do not eradicate C. difficile. Particularly important is antibiotic stewardship with restraint in the use of epidemiologically implicated antimicrobial agents, usually second- and third-generation cephalosporins, clindamycin, or fluoroquinolones, or a
combination of the three. |
- a predominant strain of C. difficile associated with high rates of severe disease in a number of hospitals in Quebec. Resistance to fluoroquinolones may have selected for the spread of this organism, and the presence of binary toxin genes and a partial deletion of the tcdC regulatory gene may confer increased virulence, leading to the observed high rates of morbidity and mortality. This outbreak illustrates that known pathogens can change their behavior and emerge as new threats. Transmission of this predominant strain among hospitals could have occurred as the result of transfers of colonized or infected patients or, perhaps, from colonized health care workers who worked at multiple institutions. In these institutions, the majority of rooms have multiple beds, with shared toilets, facilitating transmission within hospitals. It has been demonstrated that patients housed in single rooms have a lower incidence of C. difficile– associated diarrhea than patients accommodated in double rooms.
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Bacteroides
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• This genus of anaerobic bacteria comprise the majority of microorganisms that inhabit the digestive tract. 50% of most fecal matter is actually Bacteroides fragilis cells
• The percentage of Bacteroides in the gingival crevice equals about 16-20% of total flora (8-17% in plaque). • Bacteroides predominate in the feces, reaching densities of 1011/g feces. • Bacteroides produce several exoenzymes. These enzymes may play a role in the pathogenesis of the organism, assisting the bacteria in the invasion of host tissues following an initial trauma. • Collagenase • neuraminidase • DNAse • heparinase • proteases |
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Pathogenesis: B. fragilus
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• 'autoinfection' by a normal flora, often with abscess formation
• Intraabdominal abscesses from abdominal trauma or surgery -> contamination of the peritoneal cavity with fecal contents; if bacteremia occurs, there is ~30% fatality rate • Pelvic abscesses from trauma during delivery, abortion, or malignancy |
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Treponema- Spriochete causes syphilis
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• Genus: Treponema Species: pallidum
• Characterized by distinct clinical stages. These stages are known as primary, secondary and tertiary. • The primary stage involves multiplication of the bacteria at the site of entry to produce a localized infection. • The secondary stage occurs following an asymptomatic period and involves dissemination of the bacteria to other tissues. • The tertiary stage may occur after 20-30 years. • The Treponema are highly invasive organisms • The Treponema are motile, helically coiled organisms having a corkscrew- like shape. |
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Syphilis
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• The primary stage occurs weeks to months following infection. The principal sign of infection is the hard chancre, generally found on the genitals. This lesion is essentially painless but filled with treponemes and is, therefore, highly contagious.
• The secondary stage occurs following an asymptomatic period of 2-24 weeks. In the secondary stage, a skin rash spreads from the palms and soles towards the trunk. This rash may last 2-6 weeks and is followed by recovery. • The tertiary stage may erupt following the period of latency (10-20 yrs) and can affect all areas of the body and be fatal. Cardiovascular and neurological involvements are the most frequent causes of death. Typically, however, the appearance of lesions called "gummas" mark the tertiary stage. These lesions are, in fact, large granulomas resulting from hypersensitivity reactions and they can be extremely disfiguring. • Syphilis that occurs in utero is termed congenital syphilis. About 50% of such fetuses abort or are stillborn. • Of those surviving birth, two scenarios are observed: - The "early" form shows symptoms that are apparent at birth; - in the "late" form, infants appear normal until they are about 2 years old and only then display the traits known as "Hutchinson's triad", which include interstitial keratitis, notched incisors and eighth nerve deafness. • Syphilis is found worldwide and is transmitted via sexual contact (ages 20-24 are most affected). |
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Lyme’s Disease
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• Borreliae produce a generalized infection following an incubation period of about 1 week. Symptoms include fever, headache and muscle pain that lasts 4-10 days and subsides. An afebrile period lasting 5-6 days follows and then there is a recurrence of acute symptoms.
• Epidemic relapsing fever (transmitted by lice) is generally more severe than endemic relapsing fever (transmitted by ticks) and has an approximately 40% mortality if untreated. Also, the epidemic form is generally characterized by having a single relapse, while the endemic form may have several relapses due to cyclic antigenic variation of the Borrelia. • Produce febrile diseases characterized by remittent fever. • The organisms are transmitted to humans by lice or ticks. • is the agent responsible for Lyme disease transmitted via ticks • the occurrence of a "bulls-eye" lesion on the skin (erythema chronicum migrans, ECM) is almost always (85%) associated with infection. This usually begins as a small red lesion that enlarges over several weeks to a reddened area that may cover several inches in diameter. Among cases that show ECM, about 20% progress to include arthralgia, about 50% involve intermittent episodes of arthritis and 10% progress to chronic arthritis. • serologic tests (ELISA) are a better determinant for Lyme disease. |
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Borrelia burgdorferi
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• The IgG/IgM ELISA is the most commonly used screening test for the primary diagnosis of Lyme disease.
• This test is recommended at least four weeks after exposure. • Patients with the diagnosis of Lyme disease based on clinical history have positive IgG/IgM serology results within one year of the tick bite approximately 70% of the time. • IgM antibodies appear early in response to infection, this test may be positive two to six weeks after exposure. The level of IgM rapidly declines over time. A positive or equivocal IgM antibody test must be confirmed by an IgM Western Blot. The sensitivity concerns mentioned for the IgG/IgM assay also affect this assay. • The IgM response may persist in patients with prolonged illness, and a new IgM response may appear late in persistent or recurrent disease, or from re-infection. |
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Chlamydia
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- lack cell wall
• The are obligate intracellular parasites. • C. trachomatis is responsible for the diseases trachoma, inclusion conjunctivitis, lymphogranuloma venereum (LGV) and nongonococcal urethritis (NGU). In other words, oculourogenital infections. • C. psittaci produces systemic diseases including psittacosis, ornithosis and pneumonitis. |
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Infections With Chlamydia Species
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• Chlamydia trachomatis
• obligately intracellular bacterial pathogen • chlamydial diseases of most importance • conjunctivitis • pneumonia in neonates • STD in adults • Collection of specimens • cervical and ocular specimens are best collected by scraping the mucosa • urethral and nasopharyngeal specimens may be collected with fine swab on a flexible wire • semen and purulent urethral discharge are not adequate specimens |
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Mycobacterium
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• measure 0.2-0.6 µm by 1-10 µm
• gram stain faintly gram-positive • acid-fast - Once stained with carbolfuchsin, they resist decolorization with acidified alcohol due to high concentration of waxy materials in cell walls • Most strains are slow growing (more than 5 days) • Obligate aerobes and require increased CO2 |
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Testing for Mycobacterium
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• Since most mycobacterioses involve the lung, the most common specimen is sputum for AFB stain
• Stool • Urine • Biopsy tissues • Spinal fluid • pleural and joint fluids • Gastric washings • may be occasionally submitted • must be processed ASAP as Mycobacteria are acid sensitive • Skin testing |
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Tuberculosis
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- Disease
• Slowly progressive inflammatory process in the lungs • chronic granulomatous inflammation • necrosis • caseation • propensity to break into bronchi |
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TB Today
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• In the 80's there has been significant increases due to more immunocompromised patients, particularly AIDS patients
• etiology has changed from Mycobacterium tuberculosis to Mycobacterium aviumintracellulare complex of organisms. • Mycobacterium avium is also known as the Battey Bacillus • progress of disease in these patients • is usually much more rapid • disseminated disease is more common • Only 27 percent of primary MDR-TB cases were in U.S. born persons. • The percentage of U.S. born persons with MDR-TB has remained stable at approximately 0.6 percent since 2000. The proportion of MDR-TB cases among foreign-born persons has increased from 26 percent in 1993 to 73 percent of MDR-TB cases in 2004. • M. leprae - Leprosy |
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Clostridium perfringens
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- high protein foods ex meats, poultry, and eggs
- hide out in soil, sewage, dust, crops, meat, and poultry. - symptoms: nausea, diarrhea, dust, gas pains (8-24 hours after eating) - prevenative meassures: cook high protein foods throughly, keep hot food hot, keep cold food cold, refrigerate in shallow containers |
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tick cylce
( the tick, lxodes scapularis, has a 2-year life cycle in which is requires three blood meals . The tick is infected by its first blood meal, and can pass on the infection to a human in a second blood meal) |
1. (Year 1 spring) Uninfected six-legged larva hatches from egg and develops
2. (Year 1 summer)larva feeds on small animal & becomes infected. 3. (Year 1 fall & winter) Larva is dormant 4. (year 2 spring) Larva develops into 8- legged nymph 5. (Year 2 summer) Nymph feeds on animal or human, transmitting infection 6. (Year 2 summer) Nymph develops into adult tick 7. (Year 2 fall & winter) Adult feeds on deer & mate 8. Female tick lays eggs |
