Q3: Micro: Anaerobic Infections

Front 1

What are the common features of ANAEROBIC INFECTIONS? (5)

Back 1

1) MANY ABSCESSES

2) ANAEROBIC INFECTIONS characterized by FOUL SMELLING discharge, GAS, and NECROTIC tissue

3) PREDISPOSING CONDITIONS: pulmonary aspiration, bowel surgery, poor dental hygiene, abortion, human bites, animal bites, trauma, malignancy

4) Most anaerobic infections occur in DEEP or NECROTIC tissues where you have LOW OXYGEN and acess to ENDOGENOUS bacteria- - so healthy tissue iwth a nomrally high oxidation- reduction potential will not support growth of anaerobes

5) ALL ANAEROBIC infections are mixed with one or more anaerobes or microaerophilic organisms (FACULTATIVE AEROBES)

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What are most ANAEROBIC INFECTIONS casued by?

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Most infections are caused by ENDOGENOUS FLORA.

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Which infections are found above/ below the waist?

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BACTEROIDES FRAGILIS, which is PENICILLIN- RESISTANT, is found in infections below the waist.

An important distinction that must be made.

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1) What aids in EMPIRICAL THERAPY?

2) What are characteristics of bacteria that cause ORAL INFECTIONS?

3) INTRAABDOMINAL INFECTIONS?

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1) Knowledge of local flora aids in empirical therapy

2) penicillin sensitive, gram- positive cocci, mixed anaerobic infections

3) penicillin- resisitent, gram- negative rods, mixed anaerobic infections

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How do you ID and characterize clinically important bacteria?

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1) GRAM STAIN
2) Look at MORPHOLOGY
3) Production of UNUSUAL FATTY ACIDS

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What are 3 INFECTIONS DUE TO ANAEROBIC GRAM- NEGATIVE RODS?

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1) BACTEROIDES FRAGILIS
2) PREVOTELLA (BACTEROIDES) MELANINOGENICUS
3) FUSOBACTERIUM SPECIES

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What are the characteristics of BACTEROIDES FRAGILIS? (8)

What is major virulence factor?

Is it more severe than E.coli?

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1) It's the most common anaerobic gram- negative rods

2) Found in large numbers in large intestine

3) Can resist bacteriocidal action of bile

4) Does not require very strict anaerobic conditions for survival in clinical specimens. It may tolerate traces of oxygen during growth, but is definitely an anaerobe.

5) Extraintestinal invasion resulting in septicemia (bacteria found in the blood) almost as common as C. perfringens. Both anaerobes cause about 80% of anaerobic septicemias. Only 10% of bacteremias are caused by anaerobes.

6) Common in intraabdominal and female genital infections (like pelvic abscesses following OB/GYN procedures including complicated delivery, induced abortion, infected IUD)

7) B. fragilis is most important anaerobe which is penicillin resistant**** remember this!!!

8) The capsule is the major virulence factor. only encapsulated strains produce abscesses in the animal models
** Infections with E.coli are more severe than B. fragilis

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What are the characteristics of PREVOTELLA MELANINOGENICUS?

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1) It's a GRAM- NEGATIVE ROD

2) It's more common in oral infections. and along with spirochetes and other anaerobes, is a serious etiologic agent of periodontal disease- - also found in GENITAL INFECTIONS- - interesting.

3) Name derives from BLACK PIGMENT (HEMIN- A PRECURSOR FOR CYTOCHROME SYNTHESIS) formed in colonies grown on blood agar plates an in infected tissues

4) Requires hemin for growth

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What are characteristics FUSOBACTERIUM species?

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1) Microscopically these bacteria have TAPERED ENDS and are very thin in contrast to the usual shape of gram negative rods

2) Penicillin and oxygen sensitive (more sensitive to traces of oxygen than B. fragilis)

3) Important in oral infections, lung abscess and other pleuropulmonary infections.

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What are 5 NONSPORE FORMING ANAEROBIC GRAM POSITIVE RODS?

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*

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1) BIFIDOBACTERIUM

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* It's present in large numbers in NORMAL LARGE INTESTINE, especially in breast-fed infants

1) It's GRAM POSITIVE ROD witha tendency to be PLEOMORPHIC and BRANCHING

2) Rarely involved in infections

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2) PROPIONIBACTERIUM (diptheroid) *KNOW*

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* A normal inhabitant of the skin, seen frequently as contaminants in blood cultures

1) Formerly termed "anaerobic diptheroid"

2) Some strains "aerotolerant" (so it'll grow in presence of low O2)

3) Not usually involved in infections (very rarely, it causes endocarditis in compromised patients)

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3) LACTOBACILLUS

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* Gram positive rod (not pleomorphic)

1) Normal flora of intestine and vagina, where it is present in very large numbers

2) A non- pathogenic, but frequently isolated from GU and GI tract

3) Important in maintaining low PH (converts lactic acid to sugar) and preventing growth of pathogens in vagina and intestine

4) Some strains are used for making yogurt, sour milk, saurkraut

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4) ACTINOMYCES **KNOW**

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* Gram- positve branching rods (common cause of dental abscess)

1) Some strains are aerotolerant

2) Found normally in oral pharynx and Gi tract

3) Involved in cervico- facial infections and abdominal infections with sinus tract

4) Sulfur granules are yellow granules seen in lesions that are composed of microcolonies of ACTIMOMYCES plus cellular debris **CHARACTERISTIC OF ACTINOMYCES INFECTIONS

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5) CLOSTRIDIA SPECIES

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*

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What is an example of ANAEROBIC GRAM POSITIVE COCCI?

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*Peptostreptococcus (resembles streptococci in morphology)

1) These bacteria are part of the normal flora of the mouth, urogenital area, and GI tract

2) Widely involved in infections (often in association with other anaerobes)

3) May be foudn in pure culture in pleuro-pulmonary infections, brain abscesses, and OB-GYN infections

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What is an example of ANAEROBIC OF GRAM NEGATIVE COCCI?

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*VEILLONELLA

1) It;s a commensual, not imp

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How do you detect ANAEROBES?

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If you suspect a patient has an anaerobic infection:

1) Collect specimen

2) Gram stain

3) Morphology on gram stain

4) Anticipate mixed infections

5) Technical difficulties may allow one to detect only one or two species of anaerobes

6) Do not submit ORAL or FECAL cultures for anaerobes

7) Antibiotic sensitive assays not reliable for anaerobic bacteria

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What is a common type of anaerobic media?

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1) Thioglycollate broth- - a reducing agent that removes oxygen from liquid media

Front 20

What is the most common treatment for TREATMENT OF ANAEROBIC INFECTION?o

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1) PENICILLIN **EXCEPT FOR BACTEROIDES FRAGILIS (so penicillin alone is not used for infections below the diaphragm)

2) Clindamycin

3) Newer cephalosporin

4) Chloramphenical (static drug)

5) Metronidazole

6) if mixed infection, use aminoglycosides with antibiotic with anaerobic coverage

7) Surgical drainage if abscesses are present (no Ab can kill bug in an abscess)

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NORMAL FLORA!!

What is the significance of NORMAL FLORA?

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1) Protective host defense mechanism- - to prevent colonization of pathogens

2) May cause disease in immunocompromised individuals

3) Nutritional function- - how intestinal bacteria produce B vitamins and vitamin K

4) Overgrowth lead to fat malabsorption and vitamin B12 deficiency ***KNOW***

5) Each anatomic location has its own distinct flora; knowledge of the local flora will follow judicious use of AB when the barrier within each normal anatomic location is violated

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How is normal flora DISTRIBUTED in the body?

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AEROBES AND ANAEROBES

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What are the 4 AEROBIC FACULTATIVE BACTERIA in MOUTH?

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1) STREPTOCOCCUS VIRIDANS
2) NEISSERIA SPECIES
3) DIPTHEROIDS
4) S. EPIDERMIDIS

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1) STREPTOCOCCUS VIRIDANS

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GRAM POSITIVE COCCI, may be in chains

present in large numbers- - 10^6 org/ml of saliva

predominant microorganisms in the mouth, and are most common cause of bacterial endocarditis; highly adherent to DENTAL TISSUE and CARDIAC VALVES

thrive on sugar and turn sucrose into polysaccharide- - important ing in dental plaque; a by product of sugar metabolism is lactic acid and it hastens dental caries

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2) NEISSERIA SPECIES

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GRAM NEGATIVE DIPLOCOCCI, coffee bean shaped

predominance in most individuals- - not like MENINGITIDIS, which colonizes nasopharynx

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3) DIPTHEROIDS

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common name for CORYNEBACTERIUM species which are generally non- pathogenic

PLEOMORPHIC, GRAM POSITIVE ROD

COMMON CONTAMINANT OF BLOOD CULTURES because also colonizes skin

RARE cases of infections in the absence of foreign bodies

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4) S. EPIDERMIDIS

What 2 bacteria are the most common contaminants of blood cultures?

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GRAM POSITIVE COCCI, ROUND, COAGULASE NEGATIVE in ORAL FLORA

not as numerous as viridans streptococci in the mouth

s. epidermidis and diptheroids are the most common contaminants of blood cultures

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1) * NOTE NORMAL FLORA IN ORAL CAVITY

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* FOUR SPECIES mentioned are prevalent in the oral cavity

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What is the role of normal aerobic flora in disease?

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1) Normal flora may be eliminated by antibiotics and colonized by gram- negative rods or yeast which are source of drug- resistant infections

2) a small percentage of health individuals have potential pathogens in low numbers in oral cavity

3) upon hospitalization AEROBIC GRAM NEGATIVE RODS may colonize oral cavity

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What are COMMON ORAL ANAEROBES?

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1) FUSOBACTERIUM- - penicillin sensitive

2) PREVOTELLA SPECIES- - penicillin sensitive

3) ANAEROBIC STREPTOCOCCI- - penicillin sensitive

Front 31

What is important to note about oral bacteria?

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BACTERIA DO NOT EXTEND INTO THE LOWER TRACHEA, which is nearly bacteria- free in HEALTHY INDIVIDUALS

Front 32

What diseases are related to anaerobes and/ or aerobes in oral cavity?

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1) Aspiration pneumonia- - caused by aspiration of own oral secretion

2) penicillin would be useful because many of the anaerobes and aerobes in the NTF are sensitve to penicillin

3) determination of causative organisms might not be fruitful becuase of the number of organisms involved

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2) * NORMAL STOMACH FLORA

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Because of high acidity, few organisms can be cultured in stomach, except immediately after meals- - except if you have gastric obstruction

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3) * UPPER SMALL INTESTINE

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Generally sterile, in most normal fasting subjects

bacteria are usually contaminants transported form the mouth and respiratory tract and low in number

some GRAM POSITIVE AEROBES, few ANAEROBES

relative sterility of the small intestine is largely a result of rapid onward movement of bacteria during peristalsis

unconjugated bile acids, as antibacterial agents may also prevent bacterial growth

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3) continued...
What is the role of upper small intestine microflora in disease

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bacterial counts in the upper small bowel may increase if anatomical alterations cause stasis

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4) * TERMINAL ILEUM

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In normal subjects usually 10^6 ml or less are present in the feces- - it's an area of the intestine where STASIS occurs and allows for an increase in bacterial numbers

Contain:

COLIFORMS
ANAEROBES

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5) * LARGE INTESTINE AND FECES

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Marked by bacterial proliferation due to STASIS

Front 38

What are 7 species of bacteria in normal feces?

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1) BACTEROIDES
2) BIFIDOBACTERIUM
3) LACTOBACILLI
4) CLOSTRIDIAL SPECIES
5) COLIFORMS
6)OTHER ANAEROBES
7) SOME LESS FREQUENT: S. aureus, pseudomonas, proteus, klebsiella

Front 39

What are characteristics of BACTEROIDES? (1)

What is an IMPORTANT fact to know regarding the METABOLIC ACTIVITY OF THESE BACTERIA?

Back 39

GRAM- NEGATIVE ANAEROBIC RODS, NON-SPORE FORMING, SOME SPECIES LOOK

*It's important to know that the metabolic activity of these bacteria generate ammonia, acid, and gas in the colon, and AMMONIA is formed by splitting urea and from proteins

Front 40

What species of BACTEROIDES is in fecal materials?

Back 40

BACTEROIDS FRAGILIS is the most common BACTEROIDES species in the stool

It's resistent to penicillin, and it grows readily under routine anaerobic conditions used in laboratories

It's a frequent cause of INTRAABDOMINAL INFECTIONS (TRAUMA OR BOWEL RUPTURE) infection due to mixed flora, anaerobic conditions are foul smelling, gas producing and necrotic in nature

Do not use penicillin for infections originating "below the diaphragm"
CLINDAMYCIN, CEFOXITIN, METRONIDAZOLE

Aminoglycoside antibiotics, such as gentamicin, useful in combination for treating "aerobic" gram-negative rods- - INTRAABDOMINAL INFECTIONS frequently with mixed flora

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*LOOK AT DETAIL FOR OTHER BACTERIA IN THE BOOK

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*

Front 42

What is the ESTABLISHMENT OF THE NORMAL INTESTINAL FLORA?

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1) Fetal intestine is sterile
2) At birth, intestine contains at most a few bacteria, but is colonized within several hours
3) Intestinal flora of breast- fed infants consist mostly of BIFIDOBACTERIUM, but with weaning and bottle-feeding leads to flora resembles that of the adult

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How do you maintain normal flora?

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Front 44

What is the METABOLIC ACTIVITY OF NORMAL FLORA and PHYSIOLOGICAL implications on the host?

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*

Front 45

What are the 4 types of bacteria found on the skin?

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Front 46

What are the different types of bacteria found in the RESPIRATORY TRACT?

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Front 47

What are the normal flora of the GENITO URINARY TRACT?

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