Anaerobic bacterial infection

Ike Irmawati P.AMikrobiologi FK Universitas Yarsi

• Medically important infections caused by anaerobic bacteria common

• The infections Polymicrobial

Introduction

Where Anaerobes are Found

• they are found in soil, fresh and salt water, and in normal flora of humans and animals

• Anaerobes that live outside the body are called “exogenous anaerobes” (Example: Clostridium species)

• Anaerobes that live inside the body are called “endogenous anaerobes” skin, mucosal surface & ↑ concentration in : mouth & GIT as normal flora

• Most anaerobic infections are from endogenous sources

Physiology & Growth Condition for anaerob

Do not require oxygen for growth - often extremely toxic

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Anaerobes require environments with :• low / negative oxidation-reduction potential

(Eh)• pH

• Do not have cytochrome system for O2 metabolism

• no oxidative phosphorylation• fermentation• killed by oxygen• lack certain enzymes

– superoxide dismutase * O2

-+2H+ H2O2 – catalase

* H2O2 H20 + O2– peroxidase

* H2O2 H20 /NAD to NADH

Obligate (strict) anaerobes

Strict anaerobe infectious disease

• Sites throughout body • Muscle, cutaneous/sub-cutaneous necrosis• Abscesses

Bacterial Flora of the BodySite Total Bacteria Ratio

(per/ml or gm) Anaerobes : Aerobes

Upper AirwayNasal Washings 103-104 3-5:1Saliva 108-109 1:1Tooth Surface 1010-1011 1:1Gingival Crevice 1011-1012 1000:1

 Gastrointestinal Tract

Stomach 102-105 1:1Small Bowel 102-104 1:1Ileum 104-107 1:1Colon 1011-1012 1000:1

 Female Genital Tract

Endocervix 108-109 3-5:1Vagina 108-109 3-5:1

Virulence Factors1. Anti-phagocytic capsule/ Polysaccharide

capsule– Also promote abscess formation

2. Tissue destructive enzymes– Bacterioides fragilis produces variety of enzymes

(lipases, proteases, collagenases) that destroy tissue Abscess Formation

3. Beta-lactamase production– B. fragilis – protect themselves and other species in

mixed infections

4. Superoxide dismutase production Protects bacteria from toxic O2 radicals as they move

out of usual niche

5. Lipopolysaccharide promotes abscess formation, enhanced

coagulation

6. Short chained fatty acids a. Butyrate - seen in dental plaque b. Succinic acid – reduces phagocytic killing

Characteristics of Anaerobic Infections

1. Most pathogenic anaerobes are usually commensals– Originate from our own flora

2. Predisposing Conditions

Characteristics of Anaerobic Infections

3. Complex Flora

• Multiple species– Abdominal Infection Average of 5 species

• 3 anaerobic• 2 aerobic

– Less complex then normal flora– Fecal flora 400 different species

• Those predominant in stool are not infecting species

– Veillonella, Bifidobacterium rarely pathogenic

4. Synergistic Mixture of Aerobes & Anaerobes

• E. coli Consume O2Allow growth of anaerobes

• Anaerobes promote growth of other bacteria by being antiphagocytic and producing β-lactamases

Characteristics of Anaerobic Infections

Indications of Anaerobic Infections• Usually purulent (pus-producing)• Close proximity to a mucosal surface• Infection persists despite antibiotic therapy• Presence of foul odor• Presence of large quantities of gas (bubbling or cracking sound

when tissue is pushed)• Presence of black color or brick-red fluorescence• Presence of “sulfur granules”• Distinct morphologic characteristics in gram-stained

preparation• Polimicrobial flora• Failure to grow in the lab

Anaerobic Bacteria of Medical Interest

Pathogenesis of anaerobic infections

• Contamination of site with spores

• Factors which promote anaerobiasis‘crush’ injuries with interruption of blood supply, contamination with foreign bodies (dirt), tissue damage

• Germination of spores

• Toxin release

• Binding of toxin to receptor

• Resulting effect produces symptom(s) of disease

Gram-positive anaerobes• Actinomyces (head, neck, pelvic infections; aspiration

pneumonia)

• Bifidobacterium (ear infections, abdominal infections)

• Clostridium (gas, gangrene, food poisoning, tetanus, pseudomembranous colitis)

• Peptostreptococcus (oral, respiratory, and intra-abdominal infections)

• Propionibacterium (shunt infections)

Gram-negative anaerobes

• Bacterioides (the most commonly found anaerobes in cultures; intra-abdominal infections, rectal abscesses, soft tissue infections, liver infection)

• Fusobacterium (abscesses, wound infections, pulmonary and intracranial infections)

• Porphyromonas (aspiration pneumonia, periodontitis)

• Prevotella (intra-abdominal infections, soft tissue infections)

Gram positive anaerob

Clostridium

General characteristics

• gram-positive, spore-forming bacilli

• obligate anaerobes

• motile -- peritrichous flagella

(exception: C. perfringens—nonmotile)

• Group :

- histotoxic clostridia invasive

- tissue infection wound infection

- neurotoxic clostridia not invasive

Clostridium

• C. tetani• C. botulinum• C. perfringens• C. difficile

C. tetaniCharacteristics

• anaerobic gram-positive rod that forms terminal spores

• motile with peritrichous flagella

• Eh +10 mV• tetanospasmin toxin

Pathogenicity portal of entry wound

conditions of infection regional anaerobic environmentdeep and narrow wound, contamination of soil

or foreign bodiesnecrotic tissuescontamination of aerobes or facultative

anaerobes

Pathogenicity

Virulence factors– Tetanospasmin

Protein (neurotoxin)Heat-labile (65 , 30min)℃Mechanisms

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Mechanisms of tetanospasmin

toxin → peripheral nerve fibers / lymph and blood → spinal cord and brain stem → inhibitory interneuron → blocks the release of neurotransmitters from the presynaptic membrane of inhibitory interneurons→ inhibit the motor neuron → spastic paralysis (rigid paralysis)

excitatory transmitter: acetylcholineinhibitory transmitter: glycine and γ–aminobutyric acid

Mechanisms of tetanospasmin

spastic paralysis (rigid paralysis)

Control • Proper care of wounds: surgical debridement • Active immunization: tetanus toxoid

* for children immunization: DPT(diphtheria toxoid, pertussis vaccine, tetanus toxoid) * for a high-risk group : toxoid booster

• Passive immunization: tetanus antitoxinurgent prevention (along with toxoid)

As soon as possible • Special treatment

– administration of antibiotics – supportive measures

C.perfringens

Characteristics

• Shape and structure– Subterminal endospore– Capsule– Nonmotile

• Classification

five toxigenic types (A through E)

α toxin: the most potent toxin exhibits lecithinase activity destroys erythrocytes, leukocytes, and platelets hemolysis, tissue necrosis

• Cultivation anaerobic double zones of hemolysis carbohydrate fermentation (lactose)

Inner zone: θ toxincomplete

Outer zone: α toxinIncomplete

Stormy fermentation

Virulence factors– α toxin

produced by all strainsacts as a lecithinase diagnosis: Nagler reaction--egg yolk agar

Virulence factors– Enterotoxin

produced by types A(most), C, and Dheat-labile

– Otherscollagenase, hemolysin, proteinase, DNase

(deoxyribonuclease)

Pathogenicity

Disease– Gas gangrene

• Transmission: trauma• Pathogens: 60 ～ 80 ％ cases by type

A• Bacteria contaminated wound

infection toxin caused tissue necrose CO2 & H2

Pathogenicity

– Food poisoning• transmission: gastrointestinal tract• pathogens: type A• manifestation: short incubation period (8-24

hrs)

acute diarrhea incubation time 8-24 hour

Pathogenicity

Control

• Care of trauma: debridement• Antimicrobial therapy • Antitoxin• Hyperbaric oxygen • Symptomatic care for food poisoning

C. botulinum

Characteristics• Gram positive rod• Subterminal

endospore• Noncapsule• Obligate anaerobe

• Virulence factor—botulinum toxin– neurotoxin– relatively heat-labile and resistant to protease– types: A, B, C, D, E, F, G– the most potent toxic material known

Pathogenicity

mechanism of actionToxin → gut → blood → cholinergic synapses → block the release of exciting neurotransmitter, e.g., acetylcholine → flaccid paralysis

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Mechanisms of botulinum toxin

flaccid paralysis

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• Disease—Botulism– from Latin botulus, "sausage"

Food poisoning Infant botulism Wound botulism

Sausages, seafood products, milk, and canned vegetables

Honey

Pathogenicity

• Disease– Food poisoning

• manifestation:

flaccid paralysis: double vision, dysphagia, difficulty in breathing and speaking

cause of death: respiratory failure

Pathogenicity

• Disease– infant botulism

• manifestation: constipation, poor feeding, difficulty in sucking and swallowing, weak cry, loss of head control.

Floppy baby• prevention: free of honey

Pathogenicity

• Disease – wound botulism

• Rare• Transmission: trauma

Pathogenicity

Botox treatment – relaxes muscle spasms

C. difficileNormal flora gut

Pathogenicity

• Virulence factor

exotoxin A: enterotoxin

exotoxin B: cytotoxin

• Disease

pseudomembranous colitis

antibiotic-associated diarrhea

* Diagnose cytotoxin in feses

Control • Treatment

discontinuation of causative antibioticsadministration of sensitive antibiotics

• Preventionno vaccineuse antibiotics only in necessary

• Normal flora : Upper respiratory tract, GI tract, female genital tract

• Low virulence• Produce disease mucosal barrier is breached• Caused actinomycosis• Species Actinomyces israelii• Gram positive bacilli• Beaded filament, Branched or unbranched, Diphtheroid-like• Grow slowly • Molar teeth colony• Diagnosis : gram stain of sulphur granule culture

Actinomyces

• Normal flora of the skin• Gram staining pleomorfic• Metabolic product propionic acid• Patogenesis acne

Propionibacterium

• Normal flora vagina & gastrointestinal

• Lactic acid product low pH normal adult female genital tract

• Rarely caused disease

Lactobacillus

• Pleomorphic

• Mixed infection with oropharyngeal & bowel flora

Eubacterium, Bifidobacterium & Arachnia

• Gram positive cocci• Normal flora skin & mucous membrane• mixed infection• Culture from breast, brain & pulmonary

infection

Peptostreptococcus

Gram negative anaerob

• Gram negative bacilli, coccobacilli• Many species reclasified genus prevotella & porphyromonas• Normal flora GIT normal stool B. fragilis 10 11 / gram• Spesies : - B. fragilis - B. ovatus - B. distaconis - B. vulgatus - B. thethaiotamicron

* Identification based : colony, biochemical reaction & characteristic of shorth-chain fatty acid

Bacteroides

• Manifestation : - intra-abdomen abcess - peritonitis trauma on tractus digestivus - B. fragilis & B. thetaiotaomicron pelvis inflamation disease & abses ovarium• Factor virulensi : 1. polisaccharida capsule antifagosit & abcess formation 2. lipopolisakarida /endotoksin << toxic than other gram negative

Bacteroides

• These bacteria are resistant to penicillins, mostly through the production of beta-lactamase.

• Enterotoxigenic B fragilis (ETBF) is also a potential cause of diarrhea.

Treatment is complicated by 3 factors: • slow growth, • increasing resistance to antimicrobial

agents• the polymicrobial synergistic nature of

the infection.

• Gram negative bacilli, cocobacilli• Species : - P. melaninogenica respiratory tract infection - P. bivia & P. disiens genital tract infection

• Manifestation : - brain abcess, pulmonary abcess - pelvic inflammatory diseases - abcess tubo-ovarian

Prevotella

• Gram negative bacilli• Normal oral flora• Isolation from : - gingival & periapical tooth infection - breast - perianal & male genital infection

Porphyromonas

• Pleomorphic gram-negative rods

• Produce butyric acid & convert threonin propionic acid

• Isolated from mixed bacterial infection caused by normal mucosa flora

Fusobacterium

• Gram negative cocci

• Normal flora mouth, nasopharyx, intestine

• Rarely cause infection

Veillonella

Problems in identification of anaerobic infections

• air in sample (sampling, transportation)– no growth

• identification takes several days or longer– limiting usefulness

• often derived from normal flora – sample contamination can confuse

• Clinical sign : 1. foul –smelling discharge short-chain fatty acid product 2. infection in proximity to a mucosal surface 3. gass in tissue CO2 & H2 4. negative aerobic culture• Anaerobic culture, transported specimen !!!• Identification : - colony morphology - pigmentation, fluorescence - biochemichal reaction - production of short-chain fatty acid gas-liquid chromatography

Diagnosis of anaerobic infection

LABORATORY DIAGNOSISA. COLLECTION

Anaerobes are endogenous in nature I. Appropriate specimens for anaerobic culture : 1. pus 2. pleural fluid 3. urine 4. pulmonary secretions 5. uterine secretions or sinus tract

material

Aspiration is ideal Avoid Swabs

II. Collection by needle aspiration is preferable than swab culture because of

a. better survival of pathogen

b. greater quantity of specimen

c. less contamination with extraneous organism are often achieved

Anaerobic Culture Methods• Anaerobic jar* Production of a vacuum•Displacement of Oxygen

with other gases•Absorption of Oxygen by

chemical or biological methods

•By using reducing agents

• Mixed anaerobic infection surgical drainage & antimicrobial therapy

• Antibiotic : - Penicillin G not for β-lactamase-producing bacteria - clindamycin - metronidazole

Treathment of anaerobic infection