Disorders of the Hair and Nail: Diagnosis and Treatment

Chapter 11: Bacterial Infections

Matilde Iorizzo; Marcel C. Pasch; Bianca Maria Piraccini

SUMMARY

Very common condition.
Usually occurring after a minor injury, trauma or superinfection of preexisting nail disorder.
Possible severe complications if left untreated.

TIPS FOR DIAGNOSIS

Consider always performing culture with sensitivities.
Consider also Tzanck test or viral culture in doubtful cases.
Use dermoscopy to magnify the clinical signs.

TIPS FOR TREATMENT

Early treatment is recommended.
Avoidance of wet environment, chronic microtraumas, and contact with irritants or allergens.
Consider a broad-spectrum antibiotic when culture test is not feasible.

DON’T FORGET

Check for predisposing conditions.
Treat underlying dermatological disorders.
Consider imaging or biopsy in cases not responding to treatment or frequently recurrent.

PITFALLS AND CAUTIONS

Don’t prescribe systemic antibiotics without a culture test.
Most herpetic paronychias are initially misdiagnosed as bacterial infections.
Don’t forget Treponema, Neisseria, and Bacillus anthracis as possible culprits.

EXPERT PEARLS

Drain an abscess only if you are sure it’s due to bacteria.
Follow the patient over time in presence of nail plate dystrophies.
The first prescribed successful treatment might not be effective for recurrences/relapses.

PATIENT EDUCATION POINTS

Don’t forget the general rules of hand/foot hygiene.
Take care of your nails to improve dystrophic signs.
Stop manicuring until you are cured.

INTRODUCTION

Bacterial infections of the nail unit are very common as primary infections, but they can also be superinfections complicating other nail disorders. Bacterial infections of the nail unit may involve the proximal and lateral nail folds (acute paronychia) but also the nail plate, the underlying nail bed (onycholysis), and the volar fat pad of the distal phalanx (blistering distal dactylitis, impetigo, erysipelas, cellulitis). Staphylococcus aureus or pyogenes and Pseudomonas species are the typical etiological agents, but also Streptococci and Gram-negative bacteria are possible culprits.^1–3 Less often Treponema pallidum, Neisseria gonorrhoeae, and Bacillus anthracis can affect the fingernails with more or less specific clinical pictures. In general, any bacterium affecting the hand can involve the nail unit. The most dangerous infection is probably the one by the Gram-positive Clostridium perfrigens, responsible through its toxins of gas gangrene.

Minor traumas, mechanical or chemical (finger sucking, nose picking, onychotillomania/fagia, pulled hangnails, overzealous manicuring with cuticle removal, a neglected wound, traumatic onycholysis) usually are the trigger that allows the infiltration of infectious organisms^4,5 (Fig. 11.1a/b). Artificial nails and nail polish of any kind are also a possible cause of bacterial infections due to their ability to harbor microorganisms inaccessible to routine handwashing^6,7 (Figs. 11.2 and 11.3).