Which antimicrobials will you empirically prescribe for ulcers with infection

The decision concerning the prescribed antimicrobials is derived from an interrelation of the severity of infection and the presumed presence of resistant microbial strains. Infections of the diabetic foot are categorized as follows:

• Mild: Localized cellulitis without ulcer is observed, or cellulitis (redness, pain, increased temperature, sensitivity to touch) around the ulcer, or purulent exudate (Figure 17.7). The patient does not have systemic symptoms and is metabolically and haemodynamically stable. The majority of these infections are due to aerobic Gram positive pathogens (with most frequent Staphylococcus aureus) and often these are the only pathogens.

• Moderate severity: There is cellulitis of > 2 cm in diameter or deep tissue infection (abscess, septic arthritis, osteomyelitis, septic tenosy-novitis). Systemic symptoms are absent or mild and the patient is metabolically and haemodynamically stable. The principal pathogens are - as in mild infections - aerobic Gram positive microbes. When chronic ulcers are involved, or patients that have recently received antimicrobial agents, more than one pathogen is usually isolated.

• Severe: There are signs of systemic toxicity threatening the extremity or even the life of the patient (fever, rigours, confusion, hypotension) and metabolic instability (excessive hyperglycaemia, metabolic acidosis, azotaemia). Moreover, the involvement of deep tissues,

Figure 17.7. Deep neurotrophic ulcer on the plantar surface with dirty base and adjacent cellulitis. The ulcer was caused by a mild trauma 2 years prior when the patient walked barefoot in her house.

wet gangrene, extensive tissue necrosis and the fast extension of infection constitute (each one separately) signs of serious infection. When critical ischaemia of the lower extremities is present, a mild infection can very rapidly progress into a serious one. Other manifestations of a serious infection are the existence of vesicles, ecchymoses, undetermined pain, muscular weakness and sensory loss. Severe infections are polymicrobial with involvement of Gram (+), Gram (—) and anaerobic microbes.

The antimicrobial medicines that are prescribed, depending on the severity of the infection, are presented in Table 17.5 and the doses of the frequently used antimicrobials in Table 17.6.

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