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NAME: Gemella spp.

SYNONYM OR CROSS REFERENCE: Gemella haemolysins (formerly Neisseria haemolysins before 1961) (1, 2), G. morbillorum (formerly Streptococcus morbillorum), G. bergeri, G. sanguinis, G. asaccharolytica; those recovered from animals include G. cuniculi and G. palaticanis.

CHARACTERISTICS: Gemella haemolysans and other Gemella species are Gram-positive cocci which currently have not been assigned to a named family (3). Cells easily decolourize in the Gram stain and appear Gram-negative or Gram-variable (2, 4). They can occur as diplococci with their adjacent sides flattened, resembling those of Neisseria, as in the case of G. haemolysans. Or they can occur as individual cells in pairs, short chains, or irregular clusters, as in the case of G. morbillorum. They tend to be surrounded by a “corona” of fibrous material arranged radially at the cell surface (5). Cells vary considerably in size with individual cells ranging approximately between 0.5 – 1 um. The species can grow at a wide rage of temperatures with optimum growth occurring between 35 – 37 °C. They are fermentative bacteria, and are catalase and oxidase negative. Members of Gemella are facultative anaerobics; however, G. haemolysans tend to prefer aerobic growth environments, while G. morbillorum tends to prefer anaerobic growth conditions (2, 4).


PATHOGENICITY/TOXICITY: G. haemolysans and G. morbillorum are part of the normal human flora in the oral cavity and upper respiratory tract (2, 5). G. haemolysans has been isolated from approximately 30% of nasopharyngeal swabs of sampled people (6), and from human dental plaque (5). G. morbillorum is also found within the intestinal tract of humans and is reported to represent 0.1% of the total viable content (5). G. bergeri and G. sanguinis have been isolated from human clinical sources, while G. palaticanis and G. cuniculi have only been isolated from animals so far (5). Gemella spp. functions as an opportunistic pathogen, particularly in immunocompromised hosts, where they are capable of causing severe localized or generalized infection in previously damaged tissue. G. haemolysans has been isolated as a pathogen from blood cultures of patients with endocarditis, cerebrospinal fluid (CSF) cultures of patients with meningitis and brain abscess, and in patients with total knee arthroplasty (2, 4, 5, 7). Although infrequent clinical isolates, G. morbillorum has been isolated from blood cultures of patients with endocarditis, measles, septic arthritis, various suppurative processes, and CSF cultures of patients with meningitis and/or brain abscess (5). G. bergeri and G. sanguinis have been suspected as agents of endocarditis (4, 5). Another recent study showed Gemella spp. as one of the four most common etiologic pathogens responsible for community-acquired lung abscess (CALA) in the West (9.8% of the cases) (8).

EPIDEMIOLOGY: Worldwide occurrence; part of the normal human flora (5).

HOST RANGE: G. haemolysans and G. morbillorum occurs primarily in humans and some warm-blooded mammals, including rabbits, pigs, goats, sheep, and horses (2, 5). In one case, G. haemolysans was isolated from poultry meat (9). G. bergeri and G. sanguinis occur primarily in humans (5). G. palaticanis has been found in dogs and G. cuniculi in rabbits.




COMMUNICABILITY: Not known to be transmitted from person-to-person due to low virulence.


RESERVOIR: Mammals are the main reservoir (for G. haemolysans and G. morbillorum) including humans, rabbits, pigs, goats, and sheep (2, 5).




DRUG SUSCEPTIBILITY: Both G. haemolysans and G. morbillorum are highly sensitive to penicillin, ampicillin, cephalosporins, tetracyclines, chloramphenicol, lincomycins (2, 5, 5, 10), and tetrasulfathiazole (11). They are strongly inhibited by macrolide antibiotics, vancomycin, ristocetin, novobiocin, and tyrothricin, and to some extent by bacitracin and fusidic acid.

DRUG RESISTANCE: G. haemolysans and G. morbillorum are resistant to sulfonamides and trimethoprim, and aminoglycosides to a lesser extent (i.e. streptomycin) (5).

SUSCEPTIBILITY TO DISINFECTANTS: Gram-positive bacteria are generally susceptible to a number of disinfectants including phenolic compounds, hypochlorites (1% sodium hypochlorite), alcohols (70% ethanol), formaldehyde (18.5 g/L; 5% formalin in water), glutaraldehyde, iodines (0.075 g/L) (12), and 6.5% salt broth (2, 5).

PHYSICAL INACTIVATION: Although Gemella spp. is capable of growing at a wide rage of temperatures, they do not grow at temperatures below 10 or above 45 °C (2, 5). Bacteria are also sensitive to moist heat and dry heat (13).

SURVIVAL OUTSIDE HOST: The organism does not survive well outside the host (5).


SURVEILLANCE: Monitor for symptoms, particularly endocarditis, meningitis, arthritis, and pneumonia. Confirmation of infection with Gemella spp. may involve obtaining bacterial isolations and performing phenotypic observation for general morphology. Tests reactions used for this organism include pyrrolidonyl arylamidase (PYR) and leucine aminopeptidase (LAP) production, both being positive in the majority of cases, and growth in 6.5% salt broth, being negative (2, 7). Immunological techniques are not currently available.

Note: All diagnostic methods are not necessarily available in all countries.

FIRST AID/TREATMENT: Wash the exposed area with soap and warm water (omit soap if mucous membrane exposure). Treat with appropriate antibiotic therapy if required.

IMMUNIZATION: No vaccines are currently available.

PROPHYLAXIS: No preventative drugs are currently available.


LABORATORY-ACQUIRED INFECTIONS: No cases of laboratory-acquired infections have been reported to date.

SOURCES/SPECIMENS: Sources for G. haemolysans include: blood cultures, cerebrospinal fluid, mucous membranes, abscess, wound specimens, or body fluids (4, 5). Sources for G. morbillorum include: blood cultures and cultures of respiratory, genitourinary, wound and abcess specimens (4). G. bergeri and G. sanguinis have been isolated from blood cultures of patients with subacute bacterial endocarditis (5).

PRIMARY HAZARDS: The hazard of infection is low due to low virulence; however, accidental parenteral inoculation, ingestion, and inhalation of infectious droplets should be avoided.



RISK GROUP CLASSIFICATION: Risk Group 2 pathogens. The risk group associated with “Gemella spp.” reflects the genus as a whole, and may not apply to every species within the genus.

CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures. These containment requirements apply to the genus as a whole, and may not apply to each species within the genus.

PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes (14).

OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC) (14). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities (14).


SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply suitable disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up (14).

DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism before disposing by autoclave, chemical disinfection, gamma irradiation, or incineration (14).

STORAGE: : In sealed containers that are appropriately labelled (14).


REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.

UPDATED: September 2010

PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada

Although the information, opinions and recommendations contained in this Pathogen Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.

Copyright ©

Public Health Agency of Canada, 2010



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  2. Facklam, R., & Elliott, J. A. (1995). Identification, classification, and clinical relevance of catalase-negative, gram-positive cocci, excluding the streptococci and enterococci. Clinical Microbiology Reviews, 8(4), 479-495.
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  6. Berger, U. (1985). Prevalence of Gemella haemolysans on the pharyngeal mucosa of man. Medical Microbiology and Immunology, 174(5), 267-274.
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