NQN-CLQSTRiDiAL ANAEROBIC INFECTIONS

Anaerobic infections may be classified according to their microbial characteristics (Table 10.29) or oxygen tolerance, i.e. obligate and facultative anaerobes. Of these, clostridial infections have already been discussed in previous Ch 10.15.

Non-clostridial anaerobes are common colonizers of human flora and disease is usually caused by proli­feration of endogenous flora in anaerobic conditions. Clinical disease due to these infections is often non­specific and remains localized to colonized sites, e.g. GIT, respiratory tract, ears, sinuses, etc.

High-risk factors for non-clostridial anaerobic infec­tions include: (a) crush injuries with devitalized areas and reduced oxygen tension, (b) co-existing aerobic infection to utilizes oxygen, and (c) defective mucosal clearance, e.g. poor hygiene, aspiration and unconscious child.

Clinical spectrum of non-clostridial anaerobic infections is extremely wide, (Table 10.30), though some unique presentations are as follows:

• Vincent angina (trench mouth) is an acute, fulminant, necrotizing infection of oral cavity, characterized by painful ulcers, mucosal swelling, foul breath and pseudomembrane formation.

TABLE 10.29: Classification of anaerobic infections

Gram-positive bacilli

Clostridium tetani, C. botulinum, C. perfringens

Lactobacillus. Bifidobacterium

Gram-negative bacilli

Bacteroids, fusobacterium

Gram-positive cocci

Peptostreptococci, peptococci

Gram-positive cocci

Veillonella

• Ludwig angina is life-threatening cellulitis of sub­lingual and sub-mandibular spaces, characterized by sudden onset of tender neck swelling (bull-neck) and respiratory difficulty due to airway compression.

• Noma neonatorum (cancrum oris) is a rare serious anaerobic infection in newborns and severely mal­nourished infants; characterized by acute, rapidly progressive gangrene of buccal mucosa that rapidly progress to form perforating cheek ulcer.

Diagnosis of anaerobic infections depends on clinical suspicion and proper cultures. Anaerobic cultures should be collected from aspirates, abscesses or biopsies, and not from superficial sites of colonization, e.g. throat or stools. Cultures should be transported immediately to laboratory in specific transport media, which facilitates anaerobic growth.

Anaerobic cultures are indicated in presence of: (a) foul-smelling putrid odor, (b) severe tissue necrosis, gangrene or deep abscesses, (c) wound crepitus, (d) sterile aerobic cultures despite poor therapeutic response, and (e) clinical states compatible with anaerobic infections. Treatment of these infections requires adequate drainage of the site with removal of dead tissue and appropriate antibiotic therapy with either: (a) Metronidazole or clindamycin in milder cases or (b) Carbapenem or imipenem or ampicillin+sulbactum in severe cases.

TABLE 10.30: Common non-clostridial anaerobic infections

Oro-pharyngeal (poor oral hygiene)

Periodontal disease

Vincent angina or Ludwig angina

Peri-tonisllar abscess

Upper respiratory tract (extension from oral flora)

Chronic sinusitis

Chronic otitis or mastoiditis

Lower respiratory tract (poor mucus clearance)

Aspiration pneumonia

Lung abscess

CNS (extension from otitis, mastoiditis)

Brain abscess

Subdural/epidural empyema

Intra-abdominal (extension from gut flora)

Perforation peritonitis

Appendicitis, typhilitis

Necrotizing enterocolitis

Skin/soft tissue (bites, penetrating/crush injuries)

Cellulitis, fasciitis, myositis

Gas gangrene

Female genital tract (poor hygiene, local extension)

Vaginitis

Pelvic inflammatory disease (PID)

Chorioamnionitis and septic abortion (in pregnancy)

10.17