Raoultella planticola: A Rare Cause of Wound Infection

Raoultella planticola is a gram-negative, aerobic, rod bacterium commonly found in the environment, particularly in water, soil, and fish. This organism has been found to cause a variety of infections, such as necrotizing fasciitis, cystitis, cholecystitis, pancreatitis, hepatic disease, and soft tissue infections. The authors report the case of a 73-year-old-woman who presented with a R planticola wound infection of her left lower extremity after a dog scratch.She was treated successfully with local wound care using dehydrated human amnion/chorion and oral levofloxacin. Her wound healed completely in 4 months but may have been delayed due to her comorbidities. Her chronic proton pump inhibitor use and trial of antibiotics prior to diagnosis of this infection may have selected for this particular organism. Although not commonly reported as a cause of wound infections, practitioners should consider R planticola as a differential diagnosis for a nonhealing wound as prompt identification can allow for timely treatment and decreased morbidity of this serious pathogen.

Raoultella planticola is a gram-negative, nonmotile, aerobic, encapsulated, rod bacterium commonly found in the environment, particularly in water, soil, and fish.^1,2 Human infections caused by R planticola rarely are reported, but in recent years the prevalence has been increasing.^3,4 Multiple infections caused by R planticola have been described in the literature,^3-8 including pneumonia, bacteremia, necrotizing fasciitis, cystitis, cholecystitis, pancreatitis, hepatic disease, and soft tissue infections.

The authors report the case of a 73-year-old woman who presented with a R planticola wound infection of her left lower extremity after a dog scratch. To the best of the authors’ knowledge, this is the first reported case of a R planticola wound infection after an animal scratch. 

A 73-year-old woman presented to the University of Texas Medical Branch Wound Care and Hyperbarics Clinic (Dickinson, TX) with a left lower extremity wound following a dog scratch 1 month earlier. She was seen at a local emergency department in Houston, Texas, where the wound was sutured, and she was placed on trimethoprim/sulfamethoxazole. Four days later, she followed up with a primary care physician who noted worsening cellulitis around the wound, added amoxicillin/clavulanic acid to her antibiotics, and removed her sutures. She then presented to the senior authors’ clinic 1 month after the initial dog scratch due to her concern that the wound was not healing despite concluding antibiotic treatment. 

She had a history of pulmonary embolism (PE), deep venous thrombosis (DVT), hypertension, gastroesophageal reflux disease (GERD), and squamous cell skin cancer. She was taking Xarelto (Bayer, Leverkusen, Germany) for her PE and DVT, a proton pump inhibitor (PPI) for her GERD, and atorvastatin for her cholesterol. 

On physical examination, she had a superficial anterior left lower extremity wound that measured 6 cm x 4.5 cm x 0.1 cm with granulation tissue, fibrinous slough, and a small eschar overlying the wound. There was scant drainage, no odor, and moderate blanching erythema around the wound with no heat or induration. The eschar was debrided gently, a wound culture was taken, and the wound was dressed with Dakin’s solution, a collagenase ointment, and a nonadherent dressing. The patient had completed her course of antibiotics and thus did not require antibiotics until the wound culture identified an organism. 

The wound culture was sent to the Microbiology Department of the University of Texas Medical Branch in Galveston for Gram staining, identification of the organism, and susceptibility testing of antibiotics. The results were a mix of gram-positive cocci, gram-positive bacilli, and gram-negative bacilli. The culture identified abundant R planticola and trace coagulase-negative staphylococci. The susceptibility testing of R planticola demonstrated multiple antibiotics to which the bacterium was susceptible, including intravenous and oral antibiotics. The oral antibiotics to which the organism was susceptible were levofloxacin and amoxicillin/clavulanic acid. Since the patient had already taken a course of amoxicillin/clavulanic acid with no improvement, she was placed on levofloxacin for 6 weeks. Local wound care was performed weekly with a dehydrated human amnion/chorion membrane allograft (EpiFix; MiMedx, Inc, Marietta, GA) until the wound was almost completely healed. Five weeks later, local wound care was initiated with daily soap and water washes, Bacitracin ointment for one month, and Vaseline (Unilever, Rotterdam, Netherlands) application; the wound healed completely in 4 months (Figure). 

This case describes a nonhealing wound in an elderly woman with medical comorbidities after a dog scratch to her left lower extremity. Until recently, the primary causative organism R planticola was only rarely described as the cause of infections in humans. Now, it has been found in the literature to have caused several different types of infections, including ones similar to the present case, soft tissue infections, and necrotizing infections.^1,3,5,6 

The present patient had several risk factors that may have increased the likelihood of developing a wound infection caused by R planticola. Although she was not immunocompromised, she was previously on an antimicrobial regimen which may have selected for the organism. In addition, she had a medical history of GERD for which she was concomitantly taking a PPI. Using a PPI has been associated with an increased risk of bacterial gastroenteritis as a result of a less acidic environment, allowing for increased survival of enteric pathogens.^9,10 Although there were no signs of systemic bacteremia, she may have had an occult bacteremia with this pathogen due to the local wound infection. If she had an occult bacteremia, the 6-week antibiotic course would have treated this, so the bacteremia was not significant for her outcome. 

The microbiology of infected dog bite wounds is similar to that of the organisms that colonize a dog’s oral cavity. The most common aerobic organisms isolated from infected dog bite wounds were Pasteurella (50%), Streptococcus (46%), Staphylococcus (46%), Neisseria (32%), and Corynebacterium (12%) species.¹¹ Similarly, wound infections caused by dog scratches likely involve saliva, which contain these same bacteria. The particular susceptibility pattern for the organism isolated from the present patient’s wound culture is similar to those reported in other case reports,^3,4 with the exception of a few antibiotics to which the organism is resistant (Table). 

In conclusion, R planticola may not be a benign environmental bacterium but rather the cause of a variety of serious infections in humans. Its potential to become a multidrug-resistant organism is evident by the susceptibility pattern isolated from the organism that infected the patient herein, which demonstrates some resistance to antimicrobials. Thus, prompt identification and treatment are necessary to avoid significant morbidity. The authors hope this presentation of a wound infection caused by R planticola following a dog scratch will urge practitioners who encounter a nonhealing wound to consider adding this organism to their differential.  

Affiliation: University of Texas Medical Branch at Galveston, Galveston, TX

Correspondence:
Linda G. Phillips, MD
301 University Blvd 
Galveston, TX 77555
lphillip@utmb.edu

Disclosure: The authors disclose no financial or other conflicts of interest.