NAME: Micrococcus spp.
SYNONYM OR CROSS REFERENCE: M. luteus, M. lylae, M. antarcticus, and more recently M. endophyticus, M. flavus, M. terreus, and M. yunnanensis. Former members of the genus Micrococcus, now assigned to other genera, include Arthrobacter agilis, Nesterenkonia halobia, Kocuria kristinae, K. rosea, K. varians, Kytococcus sedentarius, and Dermacoccus nishinomiyaensis (1,2).
CHARACTERISTICS: Micrococcus spp. are gram-positive, oxidase-positive, and strictly aerobic cocci belonging to the family Micrococcaceae(2,3). They usually occur in irregular clusters, tetrads, and pairs(2,3), where individual cells are about 1 to 1.8 µm in diameter(2) and are usually non-motile and non-spore-forming(3).
PATHOGENICITY/TOXICITY: Micrococcus spp. and closely related genera are generally regarded as harmless saprophytes that inhabit or contaminate the skin, mucosa, and perhaps also the oropharynx; however, they can be opportunistic pathogens for the immunocompromised(2,3). They have been associated with various infections, including bacteremia, continuous ambulatory peritoneal dialysis peritonitis, and infections associated with ventricular shunts and central venous catheters(2). They have also been isolated from blood and surgical specimens in some patients with coronary and infectious conditions(3). M. luteus has been reported as the causative agent in cases of intracranial abscesses, pneumonia, septic arthritis, endocarditis, and meningitis(2).
EPIDEMIOLOGY: Micrococcus spp. and closely related genera, occur worldwide and are ubiquitous. They are found on the skin of humans and other animals and in soil, marine and fresh water, plants, fomites, dust, and air(2,3). In humans, they are most frequently found on the exposed skin of face, arms, hands, and legs. M. luteus is most common and is found in nature and in clinical specimens. One study (of 115 people) reports that up to 96% of people living in 18 states of USA carried micrococci, with the majority being M. luteus(3). The carriage rates were highest on the skin of the head, legs, and arms compared to those for nares and axillae.
INFECTIOUS DOSE: Unknown
MODE OF TRANSMISSION: Transmission is possible through contact with contaminated objects and/or surfaces (demonstrated by bacterial transfer associated with paper-towel dispensing)(4). Transmission via inhalation of contaminated droplets and/or aerosols may also be possible.
INCUBATION PERIOD: Unknown
COMMUNICABILITY: Not known to be transmitted directly from person-to-person. Transmission usually occurs through contaminated surfaces and/or objects.
DRUG SUSCEPTIBILITY: Micrococcus spp. are relatively susceptible to most antibiotics, including vancomycin, penicillin, gentamicin, and clindamycin, which have been successfully used for treating infections caused by these bacteria(2).
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)(7).
PHYSICAL INACTIVATION: Bacteria are generally sensitive to moist heat and dry heat(8) . Growth of micrococci may be significantly reduced at temperatures >45 °C, pH <6, and in high salt concentrations (>15%)(9).
SURVIVAL OUTSIDE HOST: Micrococci are relatively resistant to drying and to moderate temperature changes(2). They have been shown to persist on human skin for extended periods of time ranging from few months to at least one year (up to two and a half years for several strains of M. luteus)(3). They do not survive well and die quickly in natural soil.
SURVEILLANCE: Monitor for symptoms. Micrococcus spp. can be isolated from biological samples (taken from skin) using culture techniques (on agar media)(2,3). No immunological or biochemical detection techniques are currently available.
Note: All diagnostic methods are not necessarily available in all countries.
FIRST AID/TREATMENT: Appropriate antibiotic therapy should be administered as required, treatment should be supportive.
LABORATORY-ACQUIRED INFECTIONS: No cases of laboratory-acquired infections have been reported to date.
SOURCES/SPECIMENS: Skin (particularly in exposed regions of the body) of humans and animals, dairy products, and various environmental sources, including soil, marine and fresh water, plants, fomites, dust, and air(2,3).
PRIMARY HAZARDS: Likelihood of infection is low; however, avoid accidental parenteral inoculation, ingestion, and inhalation of infectious droplets.
SPECIAL HAZARDS: None
RISK GROUP CLASSIFICATION: Risk Group 1(10). This risk group applies to the genus as a whole, and may not apply to every species within the genus.
CONTAINMENT REQUIREMENTS: Containment Level 1 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials.
PROTECTIVE CLOTHING: Properly fastened protective laboratory clothing. Gloves when direct skin contact with infected materials or animals is unavoidable(11).
OTHER PRECAUTIONS: None(11).
SPILLS: Allow aerosols to settle. While wearing protective clothing, gently cover the spill with absorbent paper towel and apply appropriate disinfectant, starting at perimeter and working towards the centre. Allow sufficient contact time before clean up(11).
DISPOSAL: Decontaminate, either by steam sterilization, incineration, or chemical disinfection, before disposal(11).
STORAGE: The infectious agent should be stored in sealed containers that are appropriately labelled(11).
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: November 2010
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety 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.
Public Health Agency of Canada, 2010