DISCUSSION
Rothia mucilaginosa was formerly known as Staphylococcus salivarius , Micrococcus mucilaginosus , and Stomatococcus mucilaginosus . Reclassified into a new genus belonging to the familyMicrococcaceae in 2000 based on 16S rRNA sequencing3. It is an oxidase-negative, catalase-variable gram-positive coccus bacterium. Gram staining reveals non-spore-forming, encapsulated gram-positive cocci that can appear in pairs, tetrads, or irregular clusters. It is facultative anaerobic that grows well on most nonselective media and in standard blood culture systems. On sheep blood and chocolate agar, forms clear to gray/white, nonhemolytic, mucoid or sticky colonies that adhere to the agar surface4. Usually, it only causes dental plaque and periodontal disease1. Recently, cases of opportunistic infections in immunocompromised patients have been reported, including bacteremia, endocarditis, pneumonia, meningitis , peritonitis and dermatitis2,5. Remarkably, it has shown prominent adherence properties, which increase the colonization risk of catheters, damaged or prosthetic cardiac valves in bacteremic patients4. The main portal of entry is the oral cavity after mucosal disruption secondary to chemotherapy-induced mucositis or mild oral infections6. There are only a few reports onRothia mucilaginosa infections in immunocompromised children7. Chavan et al reported that those infections were associated with profound and prolonged neutropenia, use of CVC and mucositis. 40% had active or relapsed ALL2. Poyer et al . reported the same with the addition of steroids use1. In pediatric patients,Rothia mucilaginosa bacteremia has been associated to complications in up to 45%, including meningitis, pneumonia and respiratory failure and with a 36% mortality rate in one serie2. In other report, there were no complications and one patient died secondary to oncology disease relapse1. In adults, a mortality rate of 7% has been described8.
Rothia mucilaginosa is generally susceptible to penicillin, ampicillin, cefotaxime, imipenem, and vancomycin. It is frequently resistant to clindamycin, aminoglycosides, sulfamethoxazole/trimethoprim and ciprofloxacin. However, partial resistance to penicillin has also been reported in the literature4,9. Therefore, vancomycin is recommended as empirical therapy7. The duration of treatment will depend of the diagnosis. Bacteremia alone with good clinical response is treated for at least ten days2.
Endocarditis has been reported in 1/29 adults with Rothia mucilaginosa bacteremia 8 and in prosthetic devices users4,6. Treatment is valve replacement and intravenous vancomycin for six weeks4. If valve replacement is not performed, vancomycin has been associated to gentamicin or rifampin4. In other Rothia severe infections like meningitis or septic shock, vancomycin and concomitant betalactams has been used2.
In our first case, the patient had high risk ALL, prolonged neutropenia associated with CVC use and three weeks of mucositis. In the context of endocarditis with persistent fever, antibiotic regimen was changed to vancomycin plus ceftriaxone. We did not use rifampin or gentamicin because the patient had a native valve endocarditis. To our knowledge, this is the first report of Rothia endocarditis in pediatric patients. In the second case, ALL profound neutropenia and CVC use were the predisposing factors. There was a rapid clearance of blood cultures and clinical improvement with the initial treatment. Both patients had recent use of high steroids dose and the presence of predisposing factors for Rothia mucilaginosa infection. However, only the first case presented with prolonged grade III mucositis, which is crucial in the physiopathology of Rothia bacteremia. This may influenced the complication with endocarditis.
In summary, although traditionally believed to be an organism of low virulence, Rothia mucilaginosa is increasingly being recognized as an emerging opportunistic pathogen in immunocompromised patients. Predisposing factors has been described. If Rothia mucilaginosais isolated in blood cultures, we recommend the initial use of vancomycin until susceptibility testing results and the performance of an echocardiogram, because even if is infrequent, endocarditis is a severe complication that needs to be ruled out. Pediatricians should be aware of this organism when treating oncology pediatric patients, especially with predisposing described factors and in the context of a gram-positive bacteria bacteremia.