Rothia mucilaginosa

The Bacteria

Rothia belongs to the family Micrococcaceae – the same family as Micrococcus spp., Stomatococcus spp. and Kocuria spp.

There are 8 species of Rothia – but only Rothia dentocariosa and Rothia mucilaginosa has been associated with human disease.

It is a member of the mouth and upper respiratory tract flora.

Laboratory

• Gram-positive cocci may appear singly, in pairs, clusters, or chains – mostly pairs/clusters. However, Microcolonies on agar surfaces are composed of filamentous branched elements which rapidly fragment into bacillary or coccoid forms, resembling Actinomyces or Nocardia species [PHE SMI].

• Grow in aerobic or microaerophilic conditions but not anaerobically
• Weakly catalase-positive or catalase variable
• Oxidase-negative
• Colony – on blood agar clear/white, nonhemolytic, mucoid/sticky colonies – adherent to the agar surface
• It is susceptible to bacitracin and hydrolyses aesculin
• Unable to grow in the presence of 5% sodium chloride.

Infection

Rothia is an opportunistic pathogen and has been reported to cause –

• Bloodstream infection
• Skin and soft-tissue infections in children
• CNS infection – meningitis
• Pneumonia
• Necrotizing fasciitis
• Prosthetic joint infection
• Endocarditis and
• Peritonitis

Risk factors for Rothia infection – Immunocompromised state or some form of breach in host defence is associated with Rothia infection. A case series suggested a significant association was seen with steroid use (81% versus 13%; P= 0.0014) and fluoroquinolone use (86% versus 13%; P≤ 0.0001) preceding bacteremia in neutropenic patients. [Abidi, 2016]

Other risk-factors

• leukaemia 
• solid tumour 
• neutropenia
• Central venous access
• valvular heart disease
• continuous ambulatory peritoneal dialysis and
• intravenous drug abuse (IVDU)
• dental and head-neck surgery

Treatment

Rothia is uniformly susceptible to vancomycin (glycopeptides).

It is also sensitive to penicillin, amoxicillin, tetracyclines, rifampicin, 2nd/3rd generation cephalosporins, and carbapenems.

Following drugs tend to have higher MIC – fluoroquinolones, aminoglycosides, co-trimoxazole, erythromycin, clindamycin and fosfomycin.

There is no specific EUCAST/CLSI standard, but EUCAST non-species specific breakpoints can be used (Ekkelenkamp, Staphylococci and micrococci, Infectious Diseases 3e).

Glycopeptides are usually used in treatment, but combination therapy (beta-lactam with rifampicin/aminoglycosides) has also been reported.