NAME: Klebsiella spp.
SYNONYM OR CROSS REFERENCE: Human pathogens include K. pneumoniae subspecies pneumoniae, ozaenae, and rhinoscleromatis; K. oxytoca; K. granulomatis; K. variicola; and K. singaporensis. K. planticola, K. terrigena, and K. orinthinolytica have been transferred to the genus RaoultellaFootnote 1-Footnote 3. K. pnuemoniae was formerly known as Friedlander’s bacillus. K. granulomatis was previously known as Calymmatobacterium granulomatis. K. trevisanii, initially named in 1983, has been established as a heterotypic synonym for R. planticola and, therefore, is no longer recognized. K. mobilis (previously K. aerogenes) previously known as Enterobacter aerogenes is not confirmed as belonging to the genus Klebsiella and as such has been removed from the genusFootnote 1-Footnote 3.
CHARACTERISTICS: Klebsiella spp. are Gram-negative, nonmotile, usually encapsulated rod-shaped bacteria, belonging to the family EnterobacteriaceaeFootnote 1-Footnote 2. These bacteria produce lysine decarboxylase but not ornithine decarboxylase and are generally positive in the Voges-Proskauer test. Members of the Enterobacteriaceae family are generally facultatively anaerobic, and range from 0.3 to 1.0 mm in width and 0.6 to 6.0 mm in lengthFootnote 2. Klebsiella spp. often occur in mucoid coloniesFootnote 1-Footnote 2. The genus consists of 77 capsular antigens (K antigens), leading to different serogroups.
PATHOGENICITY/TOXICITY: Klebsiella spp. have been identified as important common pathogens for nosocomial pneumonia (7 to 14% of all cases), septicaemia (4 to 15%), urinary tract infection (UTIs; 6 to 17%), wound infections (2 to 4%), intensive care unit (ICU) infections (4 to 17%), and neonatal septicaemias (3 to 20%)Footnote 1. Klebsiella spp. can also cause bacteremias and hepatic infections, and have been isolated from a number of unusual infection, including endocarditis, primary gas-containing mediastinal abscess, peritonitis, acute cholecystitis, crepitant myonecrosis, pyomyositis, necrotizing fasciitis, psoas muscle abscess, fascial space infections of the head and neck, and septic arthritisFootnote 1. They are also important opportunistic pathogens, particularly among the immunocompromised. Pathogenicity factors of Klebsiella spp. include adhesins, siderophores, capsular polysaccharides (CPLs), cell surface lipopolysaccharides (LPSs), and toxins, each of which plays a specific role in the pathogenesis of these species. Depending on the type of infection and the mode of infectivity, cells of Klebsiella spp. may adhere and attack upper respiratory tract epithelial cells, cells in gastrointestinal tract, endothelial cells, or uroepithelial cells, followed by colonization of mucosal membranes. Common underlying conditions include alcoholism, diabetes mellitus, chronic liver disease (cirrhosis), chronic renal failure, cancer, transplants, burns, and/or use of cathetersFootnote 1.
K. pnuemoniae – a leading cause of community-acquired and nosocomial pneumonia and lung abscesses. Infection of the upper lobe is more common. Symptoms include: fevers, chills, and leukocytosis with red currant jelly-like sputumFootnote 1. Rare complications include lung infection involving necrosis and sloughing of the entire lobe.
K. ozaenae – causes ozena, a primary atrophic rhinitis (AR) which involves chronic inflammation of the noseFootnote 1.
K. rhinoscleromatis – causes rhinoscleroma (RS), a chronic granulomatous infection which predominantly affects the cavity of the noseFootnote 1.
Central nervous system (CNS) infections:
K. pneumoniae and K. oxytoca – cause community-acquired meningitis and brain abscesses. Clinical symptoms include: headaches, fever, altered conciousness, seizures, and septic shockFootnote 1.
K. ozaenae – associated with rare cases of cerebral abscess and meningitisFootnote 1.
Klebsiella spp. are a frequent cause of UTIs. Significant bacteriuria has been ascribed to K. ozaenae Footnote 1.
K. pnuemoniae – an important causative pathogen for pyogenic liver abscesses with symptoms including fever, right-upper-quadrant pain, nausea, vomiting, diarrhoea or abdominal pain, and leukocytosis. Abscesses occur predominantly in the right lobe and are solitary.
K. granulomatis – causes donovanosis or granuloma, a chronic ulcerative disease that primarily affects the genitaliaFootnote 1. Symptoms include development of small papule or ulcer at the site of inoculation that later develop into large red ulcers (lesions) that extend along the moist folds of the genitaliaFootnote 1.
EPIDEMIOLOGY: Klebsiella spp. occur worldwide, particularly in tropical and subtropical regions, and are ubiquitous, including forest environments, vegetation soil, water, and mucosal membranes of host speciesFootnote 1. Although they are common pathogens for community-acquired pneumonias and bacteremias, the majority of the infections are nosocomial (hospital-acquired; ~56% of all Klebsiella infections). Klebsiella spp. are considered endemic in neonatal wards and nosocomial outbreaks, particularly in neonatal wards, are common. Adult males are more susceptible to infection with Klebsiella spp. than adult femalesFootnote 1; however, Klebsiella spp. demonstrate higher colonization rates among neonates that may survive up to months as compared to a few days to weeks in adults. Risk of infection and carriage rates of Klebsiella spp. increases with increase in duration of stay within a hospital; 11% to 42% increase in carriage rate within 14 days of hospitalization according to one studyFootnote 1. Infection and carriage rates also increase with antimicrobial use; this usually leads to the development of extended-spectrum beta-lactamase (ESBLs) which provide resistance against antibioticsFootnote 1,Footnote 4.
K. pneumoniae is most pathogenic to humans among all Klebsiella spp., followed by K. oxytoca. K. ozaenae and K. rhinoscleromatis cause specific diseases in humansFootnote 4. K. granulomatis and K. variicola have also been indentified as being pathogenic to humans. K. singaporensis is still very novel and its pathogenicity to humans has yet to be determined. Although, the number of infections is lower than some other pathogens, infections by Klebsiella spp. demonstrate substantial morbidity and mortality. K. pneumoniae occurs in the nasopharynx and intestinal tract of humans, as a saprophyteFootnote 4. It is one of the leading causes of community-acquired pneumonia. It is important cause of primary liver abscess and of microbial fascial space infections among diabetic patients in Asia, predominantly in TaiwanFootnote 1. It is commonly isolated from infections of burns and human bites. Recently, it has become an increasing cause of chronic diarrhoea in HIV infected adults in Africa. K. pnuemoniae and K. oxytoca are important causative agents of community-acquired meningitis and brain abscesses in Asia, predominantly in Taiwan. According to some reports, Klebsiella spp. are responsible for 16 to 43% of central nervous system (CNS) infections and brain abscesses. Environmental strains of K. pneumoniae have been shown to be equally virulent as clinical strains; however, whether this is true or not for other Klebsiella spp. has yet to be determinedFootnote 5.
HOST RANGE: HumansFootnote 1,Footnote 2, mammalsFootnote 1 (including horses, bovines, rhesus and squirrel monkeys, guinea pigs, muskrats, lemurs, and bats), aquatic animals (including elephant seals, California sea lions, and harbour seals), reptiles (including snakes, crocodiles, and American alligators), birds, insects, and plants (banana, rice sugar cane and maize)Footnote 1,Footnote 2. Specifically identified sources for some Klebsiella spp. are listed below:
K. pneumoniae – humans, horses, bovines, raptors, and common in all Australian mammalsFootnote 1.
K. oxytoca – humans, mammals (ringtail possums, gliders, and bats) throughout Australia, and insectsFootnote 1.
INFECTIOUS DOSE: Unknown. According to one source, 108 Klebsiella organisms per gram of feces are required to produce damageFootnote 1.
MODE OF TRANSMISSION: Klebsiella spp. can be transmitted through skin contact with environmentally contaminated surfaces and/or objectsFootnote 1; examples include Loofah spongesFootnote 1, medical equipmentFootnote 4, and blood products. Fecal transmission has also been suggested for some cases of bacteremia caused by Klebsiella spp.Footnote 1.
K. rhinoscleromatis can be transmitted from person-to-person via airborne secretions; however, prolonged contact with infected individuals is required for infectionFootnote 1.
K. granulomatis are sexually transmitted. They may also be vertically transmitted (from mother to child) or by accidental inoculation. Transmission rates between partners are low (<50%) compared to other sexually transmitted diseases.
INCUBATION PERIOD: Not clearly understood. According to some sources, the incubation period for K. granulomatis is usually 1 to 6 weeksFootnote 1.
COMMUNICABILITY: Members of Klebsiella spp. can be transmitted from person-to-person; however, the communicability period is unknown. Approximately one-third of people carry Klebsiellae in their stoolsFootnote 1; detection rates according to different studies vary from 5% to 36%Footnote 4. Detection rates in nasopharynx vary from 1% to 6%. Hospital personnel have been shown to frequently carry Klebsiellae on their handsFootnote 1.
RESERVOIR: Infected humans (with or without symptoms of disease) are the primary reservoir for Klebsiella sppFootnote 1,Footnote 2,Footnote 4. Other sources include: infected infants (usually asymptomatic) colonized with invasive strains of Klebsiella spp.Footnote 1, hospital patients (for nosocomial infections), and certain plantsFootnote 6.
DRUG SUSCEPTIBILITY: Klebsiella spp. are known to show resistance to penicillins, especially ampicillin and carbenicillinFootnote 1. Since more and more strains of Klebsiella spp. appear to be developing and harbouring extended-spectrum beta-lactamases (ESBLs), cephalosporinases, and carbapenemases, resistance of Klebsiella spp. to current antibiotics appears to be increasingFootnote 1,Footnote 2,Footnote 4. According to results from some studies in Europe and USA, ranges of susceptibility were as followsFootnote 1: ceftazidime (92-95%), ceftriaxone (96-98%), cefotaxime (96%), piperacillin-tazobactam (90-97%), imipeneum (98-100%), gentamicin (95-96%), amikacin (98-99%), triethoprimsulfamethoxazole (SXT) (88-90%). Resistance values tend to be higher for strains isolated from ICU patients compared to non-ICU patients. Pan-resistant isolates have been identified in the Indian subcontinentFootnote 7.
SUSCEPTIBILITY TO DISINFECTANTS: Gram-negative 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, and iodines (0.075 g/L)Footnote 8.
PHYSICAL INACTIVATION: Reduction in the growth and metabolic activity of K. pneumoniae at temperatures >35 °C has been reportedFootnote 9. Significant growth reduction has been demonstrated at 60 °C; however, the bacteria still show some metabolic activity (i.e. not completely inactivated). Bacteria are also sensitive to moist heat and dry heatFootnote 10.
SURVIVAL OUTSIDE HOST: Klebsiella spp. grow rapidly on surfaces of potatoes and lettuce with counts exceeding 103 organisms per g of surfaceFootnote 1. They have been found in Loofah sponges made from vegetable gourds. They also survive well within wood and sawdust. They do not grow well on human skin and generally exists in infected individuals and/or surfaces, and the environment; surface water, sewage, soil, and on plants, where they can survive for extended periods of timeFootnote 4.
SURVEILLANCE: Monitor for symptoms. Other tests include isolating strains of the bacteria or typing different isolates. This is often necessary for investigation of endemic and epidemic nosocomial infections and also for epidemiological investigations from the environmentFootnote 1,Footnote 4. Klebsiellae can be isolated by growth in media. Although there are specific chromogenic media available for isolating these bacteria from specific samples, Klebsiellae grow well on blood and non-differential mediaFootnote 1. Biotyping and serotyping are two common forms of typing methods used for typing Klebsiella spp.Footnote 1,Footnote 4. Serotyping is the most widely used technique for typing these bacteria which involves detection of capsular antigens by means of antisera. Serotyping tests include: quelling reaction, immunofluorescence, double-diffusion gel precipitation, counter-current immunoelectrophoreses, Staphylococcus coagulation, and latex coagulation methodsFootnote 1. Biotyping is not preferred due to the large number of reactions and the amount of time required to complete these testsFootnote 1,Footnote 4. Molecular typing methods are also being developed, although they are not commonly used. These include: plasmid analysis, ribotyping, PFGE, and random amplified polymorphic DNA analysis, all of which have been successfully used to track strains epidemiologicallyFootnote 1.
Note: All diagnostic methods are not necessarily available in all countries.
LABORATORY-ACQUIRED INFECTIONS: 1 case of laboratory-acquired infection with K. pneumoniae up to 1976 has been reportedFootnote 11.
SOURCES/SPECIMENS: Sources for clinical samples of Klebsiella spp. primarily include samples from respiratory tract (RT; nasopharyngeal samples) and urinary tract (UT)Footnote 1,Footnote 2. Specific sources identified includeFootnote 2:
K. pneumoniae – all sites within the human body, RT and UT most common
K. ozaenae – nasal discharge most common, RT, UT, and blood
K. rhinoscleromatis – nasal discharge
K. oxycota – all sites within the human body
K. granulomatis – genital tract
K. variicola – blood, banana plantsFootnote 1, rice, sugar cane, and maize
PRIMARY HAZARDS: Direct contact of mucosal membranes with contaminated surfaces and/or object, and inhalation of infectious airborne secretions, accidental parenteral inoculation and/or ingestion.
SPECIAL HAZARDS: None.
RISK GROUP CLASSIFICATION: Risk Group 2Footnote 13. The risk group associated with “Klebsiella spp.” reflects the genus as a whole, but does not necessarily reflect the risk group classification of 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 culturesFootnote 14. The containment and operational requirements may vary with the species, subspecies, and/or strains.
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 splashesFootnote 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). 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 activitiesFootnote 14.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean upFootnote 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 incinerationFootnote 14.
STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelledFootnote 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 2011
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, 2011