Savané Moussa, MD
Hospital of Dermatology of Bamako (HDB), B. P. 251, Bamako, Mali; Faculty of Health Sciences and Techniques, Conakry, Guinea; Tel. 0022399335376; E-mail: moussasavan@ymail.com
Citrobacter infections in immunocompetent subjects are rare and occur mainly in the urinary and respiratory tracts.1 Of all Citrobacter species, Citrobacter freundii is the most frequently isolated group in these patients.2 A mortality rate of 6.8% has beeń reported in patients hospitalized with Citrobacter infection, but it can increase dramatically to 17.8-56% with Citrobacter bacteremia. There is growing public concern about longer hospital stays and higher antibiotic costs because of the recent emergence of multidrug-resistant strains of Citrobacter.3 We report a case of Citrobacter skin infection in a treatment-resistant immunocompetent subject.
A 26-year-old Malian patient, working in a mining area in Kayes, with no particular medical or surgical history, consulted for diffuse papulo-pustules on the integument, for which he had consulted more than 3 times in local medical centres where the diagnosis of chickenpox had been made and each time he had received treatment (aseptic, antibiotics and antipyretics) which had led to slight improvement.
In view of the persistence and appearance of new lesions over the past 3-weeks, he consulted the dermatology hospital in Bamako on 2nd November 2021. On examination, he was in good general condition with a fever of 38.7 °C, a body mass index (BMI) of 20 and other normal vital parameters.
On the skin, there were papulo-pustules, some with central umbilication, others ulcerated, erosive and coalescent, diffuse. These lesions were predominant on the posterior trunk, forearms, buttocks and external genitalia. There were also pigmented scarring lesions at the sites of former lesions. The rest of the muco-phanerian examination and other systems were unremarkable (Figure 1).
Figure 1. Papulo-pustules, some with Central Umbilication, others Ulcerative, Erosive and Coalescing, and Pigmented Scars on the Sites of Old Lesions
A: Posterior trunk
B: Right forearm
C: External genitalia
D: Buttocks
The blood count, the transaminases, the creatinine, the blood sugar, the treponemal and viral serology (hepatitis B and C viruses, human immunodeficiency virus (HIV)) were normal but no polymerase chain reaction (PCR) was carried out for monkeypox. Urine cytobacteriological examination and abdominopelvic ultrasound were also normal. Pus collection (from a lesion on the buttocks, a lesion on the right forearm, and one on the external genitalia) for bacteriological analysis revealed the presence of Citrobacter freundii and the susceptibility test showed sensitivity to ceftazidime and gentamycin. The evolution was favourable after 7-days of treatment according to the patient (by telephone) who did not return for his check-up.
Citrobacter infections are rare. They usually affect patients with impaired host defenses.4 We report a case of Citrobacter freundii skin infection in an immunocompetent patient who was resistant to empirical treatments of common bacterial skin infections. Citrobacter spp are facultative anaerobic Gram-negative bacilli of the Enterobacteriaceae family,1 commonly found in water, soil, food, and intestines of animals and humans.5
One case was atypical in its clinical presentation, simulating chickenpox, but was clinically ruled out because chickenpox is never recurrent and these lesions usually have a cephalocaudal progression. Reported cases of Citrobacter infecting the skin have had the following clinical presentations: folliculitis, cellulitis, urticaria, gangrenosum-like ecthyma, ulcers and necrotizing fasciitis.2 Previously recognized as low virulence environmental contaminants or colonizers, they are now known to cause a broad spectrum of infections affecting the urinary tract, liver, biliary tract, peritoneum, intestines, bone, respiratory tract, endocardium, wounds, soft tissue, meninges and bloodstream,3 however, we did not observe any extracutaneous involvement in the patient on the clinical and paraclinical level. The comorbidities that could favor the occurrence of Citrobacter infection, notably malignant tumor, arterial hypertension, diabetes mellitus, hepatobiliary stones, and chronic renal disease, were not found in the patient. Our patient was not also under long-term immunosuppressive treatment which could also favor the occurrence of this infection as reported by Ferranti et al1 in a patient suffering from pemphigus and under immunosuppressive treatment who presented an ecthyma gangrenosum with Citrobacter freundii. These enterobacteriaceaes may possess an inducible AmpC gene, which codes for a beta-lactamase leading to potential antibiotic failure,1,6 Lavigne et al7 reported in their study that 28.9% of Citrobacter spp were resistant to extended-spectrum cephalosporins. After antibiotic susceptibility testing, our patient was treated with ceftazidime and gentamycin, the latter reported to be effective against these enterobacteriaceae in the literature.8
It is important for clinicians to be aware of both possible atypical presentations of certain bacterial infections, and of antibiotic resistance. Bacteriology and antibiotic susceptibility testing are essential in cases of bacterial infections that are thought to be common and resistant to empirical treatments.
The authors have received written informed consent from the patient.
The authors declare that they have no conflicts of interest.
1. Ferranti M, Cicogna GT, Sattin A, Alaibac M. Citrobacter freundii sepsis in an immunosuppressed patient with pemphigus vulgaris. BMJ Case Rep. 2018; 11(1): e227091. doi: 10.1136/bcr-2018-227091
2. Whalen JG, Mully TW, English JC. Spontaneous Citrobacter freundii infection in an immunocompetent patient. Arch Dermatol. 2007; 143: 124-125. doi: 10.1001/archderm.143.1.124
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7. Lavigne JP, Defez C, Bouziges N, Mahamat A, Sotto A. Clinical and molecular epidemiology of multidrug-resistant Citrobacter spp. infections in a French university hospital. Eur J Clin Microbiol Infect Dis. 2007; 26(6): 439-441. doi: 10.1007/s10096-007-0315-3
8. Chen C, Chen Y, Wu P, Chen B. Update on new medicinal applications of gentamicin: Evidence-based review. J Formos Med Assoc. 2014; 113: 72-82. doi: 10.1016/j.jfma.2013.10.002
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