Tularemia and Once-Daily Gentamicin

Tularemia has been a subject of interest over the last few years,as it can be used as a biological weapon (2). An aminoglycosidesuch as streptomycin has been the accepted treatment of choiceand can achieve a 100% cure rate. Gentamicin administered threetimes a day has been used as an alternative (5). The use ofonce-daily dosing has been recommended, but few data regardingits success rate against this infection are available. We reporttwo cases of glandular tularemia successfully treated with once-dailygentamicin.

Case 1.

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Case 1.

A 23-year-old white male sustained a bite on his index fingerwhile petting a kitten. Within 5 days, he developed fever, painfulaxillary lymph nodes, myalgia, and headache. He was treatedwith ceftriaxone for 2 days and then with amoxicillin-clavulanatefor 14 days with some improvement. However, symptoms recurredafter he finished the antibiotic course. He was referred forfurther workup and management. A tularemia agglutination testresult was 1:320. He was started on intravenous (i.v.) gentamicinat 5 mg/kg of body weight daily as outpatient therapy, whichwas adjusted to maintain a trough serum concentration of 0.5to 1.5 µg/ml and a peak serum concentration of 8 to 10µg/ml. His serum creatinine level before the initiationof therapy was 0.8 mg/dl. His condition improved significantlywithin 48 h. On day 7 of treatment, he underwent incision anddrainage of an axillary lymph node, as it was large and fluctuant.The culture was sterile. The patient finished 10 days of treatment.His serum creatinine level at the end of therapy was 0.8 mg/dl.

Case 2.

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Case 2.

A 28-year-old male, a brother of the first patient, was bittenby the same kitten and within three days developed generalizedmuscle aches and painful axillary lymph nodes. He was treatedwith ceftriaxone for 1 day followed by azithromycin for 5 days,with improvement. His symptoms recurred after the cessationof therapy. He was subsequently treated with ceftriaxone for2 days and then with amoxicillin-clavulanate for 10 days, withsome improvement. Upon referral, a tularemia agglutination testresult was 1:160. The serum creatinine level was 0.7 mg/dl.He was treated with i.v. gentamicin 5 mg/kg daily for 7 daysto keep peak and trough serum concentrations in the same rangeas for the first patient, with complete resolution of symptoms.The posttherapy serum creatinine level was 0.8 mg/dl.

Neither patient experienced side effects or relapse after 5months.

Discussion.

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Discussion.

Francisella tularensis is a gram-negative pathogen primarilyof animals and occasionally of humans. Tularemia continues tobe responsible for significant morbidity and mortality, despitethe availability of numerous antibiotics active against theorganism (5). Streptomycin has long been considered the drugof choice for tularemia, but it may be associated with significantside effects. Tetracycline, chloramphenicol, and quinolonesare useful alternatives, although relapse rates are higher.

Gentamicin is more widely available and can be given intravenouslyas an acceptable alternative (3, 4). Several case reports haveshown that gentamicin given as three doses daily for 7 to 10days has a cure rate of 86%, a relapse rate of 6%, and a failurerate of 8%. In these reports, only 41% of the patients had beenon gentamicin monotherapy, or they were treated with shortercourses of therapy (<6 days), or they suffered a delay inthe institution of treatment (1, 3). Although once-daily gentamicinhas been recommended, its efficacy has not been reported. Ourpatients were treated as outpatients with i.v. gentamicin andhad complete resolution of symptoms with no relapse and experiencedno significant side effects.

Conclusion.

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Conclusion.

Once-daily gentamicin therapy is an effective treatment forpatients with tularemia. Patients should be closely monitored,with gentamicin peak serum concentrations between 8 and 10 µg/mland trough serum concentrations of 0.5 to 1.5 µg/ml maintained.

REFERENCES

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