Granulicatella adiacens
Granulicatella adiacens is a fastidious Gram-positive cocci (pairs, chains) and is part of the nutritionally variant streptococci (NVS).[2][3][4] Like other constituents of the NVS, it can cause bacteremia and infective endocarditis (IE), with significant morbidity and mortality.[4][2] NVS has less often been implicated in a variety of other infections, including those of the orbit, nasolacrimal duct and breast implants.[5] It is a commensal of the human mouth, genital, and intestinal tracts, although it is rarely implicated in infections,[5][2] in part due to it being a fastidious organism and rarely being identified in the laboratory environment.[5] However, its identification has become more frequent with use of commercial mediums and automated identification systems.[5] Because it has been difficult to identify, it has been considered one of the causes of culture negative IE.[2] Identifying G. adiacens can allow more appropriate selection of antibiotics, especially when susceptibility testing is not available.[4]
| Granulicatella adiacens | |
|---|---|
Scientific classification  | |
| Domain: | Bacteria |
| Phylum: | Bacillota |
| Class: | Bacilli |
| Order: | Lactobacillales |
| Family: | Carnobacteriaceae |
| Genus: | Granulicatella |
| Species: | G. adiacens |
| Binomial name | |
| Granulicatella adiacens Collins & Lawson, 2000[1] | |
Clinical relevance
| Antibiotic | Susceptible (%) |
|---|---|
| Penicillin | 38.9 |
| Cefotaxime | 18.9 |
| Ceftriaxone | 43.3 |
| Erythromycin | 52.2 |
| Levofloxacin | 84.5 |
| Clindamycin | 91.9 |
| Meropenem | 100 |
| Vancomycin | 100 |
Infective endocarditis
Of human diseases caused by G. adiacens, infective endocarditis (IE) is the most common.[5] Among the members of the genus Granulicatella, G. adiacens seems to be more capable of causing IE, possibly due to its capacity to bind to the cardiac valvular tissue.[2] IE from NVS species has been described as indolent-onset, often in the setting of preexisting heart valve damage.[2] The aortic and mitral valves are most commonly affected.[2] More often than not, IE due to NVS produces detectable vegetations, although other classic IE signs (e.g., Osler nodes) are usually not present.[2] Treatment failure is frequently observed, and approximately 1/4 of cases require prosthetic valve replacement.[2]
Antibiotic treatment
The Granulicatella genus is more resistant to antibiotics than viridans streptococci (another common cause of IE), although it is still often susceptible to clindamycin, erythromycin, rifampicin and vancomycin.[2]
Laboratory identification
It grows best on media supplemented with thiol or pyridoxal.[5] Phenotypic identification of this genus is difficult, but feasible with automated identification systems.[5] 16S rRNA gene sequencing is confirmatory.[5]
Classification history
In 1961, a new type of viridans streptococci was classified as "nutritionally variant streptococci" (NVS).[3] In 1989, NVS was subdivided into Streptococcus defectiva and Streptococcus adiacens, which in 1995 were relocated to create a new genus Abiotrophia.[3][2] In 2000, three members of the Abiotrophia genus were reclassified into the genus Granulicatella (Granulicatella adiacens, balaenopterae and elegans).[2]
References
- Collins, MD; Lawson, PA (January 2000). "The genus Abiotrophia (Kawamura et al.) is not monophyletic: proposal of Granulicatella gen. nov., Granulicatella adiacens comb. nov., Granulicatella elegans comb. nov. and Granulicatella balaenopterae comb. nov". International Journal of Systematic and Evolutionary Microbiology. 50 Pt 1: 365–369. doi:10.1099/00207713-50-1-365. PMID 10826824.
- Shailaja, TS; Sathiavathy, KA; Unni, Unni (July 2013). "Infective endocarditis caused by Granulicatella adiacens". Indian Heart Journal. 65 (4): 447–9. doi:10.1016/j.ihj.2013.06.014. PMC 3861137. PMID 23993006.
- Gardenier, JC; Hranjec, T; Sawyer, RG; Bonatti, H (June 2011). "Granulicatella adiacens bacteremia in an elderly trauma patient". Surgical Infections. 12 (3): 251–3. doi:10.1089/sur.2010.059. PMC 4702435. PMID 21524203.
- Alberti, Michael O.; Hindler, Janet A.; Humphreys, Romeny M. (26 February 2016). "Antimicrobial Susceptibilities of Abiotrophia defectiva, Granulicatella adiacens, and Granulicatella elegans". Antimicrobial Agents and Chemotherapy. 60 (3): 1411–1420. doi:10.1128/AAC.02645-15. PMC 4776019. PMID 26666926.
- Gupta, Sangita; Garg, Meenu; Misra, Sanjay; Singhal, Sanjay (Jan–Mar 2018). "Granulicatella adiacens abscess: Two rare cases and review". Journal of Laboratory Physicians. 10 (1): 121–123. doi:10.4103/JLP.JLP_58_17. PMC 5784284. PMID 29403221.