Table 1.

Outbreak organisms

Organism, Type of Infection(s) Associated with Outbreak, Process	Common Reservoirs	Potential Sources and/or Sites Associated with Outbreaks	Method of Detection: P = Patients, E = Environmental Source	Comments
Acinetobacter species Wounds, bloodstream and respiratory tract Infection and/or colonization	Wounds, genitourinary tract (GU), peri-rectal (PR) area, skin	Instrumentation, burns, trauma, surgery, respiratory equipment, gloves, parenteral nutrition, water	P = micro cultures E = surface swabs and culture of potentially implicated items	Intensive care units, patients returning from war zones; immunocompromised population Contaminates the environment extensively and can be difficult to eradicate
Adenovirus Epidemic keratoconjunctivitis (EKC); disseminated infection, cystitis	Oral pharyngeal secretions, urine	Equipment (tonometers) and health care workers	P = viral cultures, PCR E = not known to be useful	Ophthalmology patients, NICU patients, immunocompromised patients
Aspergillus spp Bloodstream, lower respiratory tract Infection and/or colonization	Air, dust, mold	Building demolition, renovation or construction sites, ventilation systems, dust-generating activities	P = microbiologic clinical (micro) cultures E = air sampling, surface samples	Often pathogenic in immunocompromised populations, and premature infants Can see increases with floods, severe weather events such as hurricanes
Burkholderia cepacia Bloodstream Infection and/or colonization	Oropharynx, skin	Water, contaminated solutions and skin disinfectants, contaminated equipment	P = micro cultures, stool E = cultures of potentially implicated items	Disinfectants (especially those containing iodine), water, solutions
Candida species Bloodstream	Skin (intertriginous areas)	Hands, onycholysis, devices	P = micro cultures E = cultures of hands and nail beds	Immunocompromised population at increased risk
Campylobacter fetus	Gastrointestinal	Food	P = micro cultures E = cultures of potentially implicated items/personnel	NICU patients at risk
Enterobacter species Urinary tract, bloodstream Infection and colonization	PR, bloodstream, wounds	Contaminated IV fluids, total parenteral nutrition Hands/dermatitis	P = micro cultures E = cultures of potentially implicated items	Intensive care units, reuse of calibrated pressure transducers
Enterococcus faecalis and faecium (Enterococcus or Group D) Neonatal sepsis, cystitis, bacteremia Infection and/or colonization with resistant strains (VRE)	GU, PR, Gastrointestinal (GI) tract	Neonates/surgical patients/transplant patients	P = stool, peri-rectal vaginal cultures; hand cultures E = used for vancomycin-resistant strains, primarily surface samples	Vancomycin resistant strains (VRE) do contaminate the environment and hands of health care personnel; environmental cultures are not used for susceptible strains
Escherichia coli Epidemic diarrhea, wounds and surgical incisions, urinary tract, bloodstream, neonatal sepsis or meningitis Infection	GI tract, skin, wounds	Equipment or fluids contaminated with organisms from lower GI tract, contaminated fluids	P = micro cultures, stool E = cultures of potentially implicated items	Very common normal flora
E coli O157:H7 and other hemorrhagic species Diarrhea and hemorrhagic colitis Infection	GI tract of animals	Contaminated water, and foods (meat, salads)	P = micro cultures E = cultures of potentially implicated items	Hemolytic uremic syndrome and thrombotic thrombocytopenic purpura are sequelae, high mortality among elderly and extremely young, cross contamination described
Hepatitis A Infection	Liver, stool, blood	Hands/foods, transfusion	P = micro cultures E = not known to be useful, cultures of potentially implicated personnel	Cross contamination described
Hepatitis B Infection	Liver, blood, and sterile body fluids	Blood and secretions, transfusions, improperly cleaned equipment, poor infection control practices	P = serology E = not known to be useful, cultures of potentially implicated personnel	Patients with diabetes, on dialysis, patients in psychiatric units
Hepatitis C Infection	Liver, blood, and sterile body fluids	Blood and secretions, transfusions, improperly cleaned equipment, multidose vials, poor infection-control practices	P = serology E = not known to be useful although recently integrated into an outbreak investigation, cultures of potentially implicated personnel	Patients on dialysis, patients in psychiatric units
Herpes virus infection Skin, pneumonia, mucosal surfaces Infection and/or colonization	Skin, saliva	Patients and health care workers	P = micro cultures E = not known to be useful	Outbreaks reported when patients shed or with lesions in health care workers
Klebsiella pneumoniae Urinary tract, pneumonia, bloodstream and neonatal infections Infection and/or colonization	PR, nares, mouth, wounds, skin, blood	Urinary catheters, hand lotions, contaminated fluids, ventilators, eczema Foodborne outbreaks recently reported	P = micro cultures E = cultures of potentially implicated items	Can be resistant to extended beta lactamases and carbapenemase; cross contamination described; rarely contaminates the environment
Legionella pneumophila and other species Pneumonia Infection	Water	Potable water, air conditioning units, cooling towers, ice machines, construction	P = micro cultures E = cultures of potentially implicated items/personnel	Can be associated with intense media scrutiny; 1 health care–associated case should trigger an investigation
Listeria monocytogenes Bloodstream and central nervous system infections Infection	Food	Contaminated foods	P = micro cultures E = cultures of potentially implicated items	Immunocompromised and mother-infant pairs at highest risk
Mycobacterium tuberculosis Respiratory Infection	Lungs, can disseminate	Airborne, improperly cleaned equipment	P = culture and PCR E = not known to be useful, cultures of potentially implicated personnel	Health care transmission suggests poor infection control
Nontuberculous mycobacteria (Mycobacterium avium, Mycobacterium gordonae) Respiratory, skin, bloodstream Infection and/or colonization	Lungs, skin	Contaminated water, improperly cleaned and sterilized equipment	P = micro cultures E = cultures of potentially implicated items	Associated with pseudo-outbreaks Reuse of improperly cleaned dialyzers, contaminated ice machines and other equipment
Pseudomonas aeruginosa Burns, wounds, urinary tract, pneumonia Infection and/or colonization	Gastrointestinal tract	Ventilators, whirlpools, sitz baths, solutions (mouthwash), any other water sources	P = micro cultures, stool, E = cultures of potentially implicated items	Primarily seen in immunocompromised patients and can be normal flora
Ralstonia pickettii Bloodstream	Skin, oropharynx, blood	Water including sterile, skin disinfectants, incubator water baths	P = micro cultures, stool E = cultures of potentially implicated items	Deliberate contamination of sterile fluids has been reported Neonates and immunocompromised hosts
Salmonella species GI infections, bloodstream Infection and/or colonization	GI and biliary tract	Contaminated food, dairy, eggs/poultry, contaminated blood products	P = stool, blood cultures E = not known to be useful	Not normal flora, cross contamination reported
Serratia marcescens Urinary tract, bloodstream, respiratory Infection and/or colonization	GI and GU	Solutions, inhalation therapy equipment, disinfectants, plasma, EDTA collection tubes, air conditioning vents, improperly cleaned equipment, chlorhexidine	P = micro cultures E = cultures of potentially implicated items	Cross contamination well described, reuse of calibrated pressure transducers
Staphylococcus aureus includes methicillin-resistant strains Surgical site, bloodstream Infection and or colonization	Human skin, anterior nares, skin, throat and upper respiratory tract, rarely rectal	Nasal/skin carriage in health care workers Increased nurse-to-patient ratios	P = microbiologic cultures E = hand and anterior nares cultures; rarely environmental cultures are indicated including settle plates if looking for a cloud spreader	Usually associated with surgical site and bloodstream infections, molecular and genotypic typing can determine whether there is a point source or technical problems. Point source can be from a carrier and would require cultures of staff and other patients; technical failures can lead to rhinovirus infection may be a risk factor, cross contamination well described for human shedding
Staphylococcus species (coagulase negative) Blood	Human skin	IV fluids, contaminated hands of health care workers, implanted devices	P = microbiologic cultures E = not known to be useful	Pathogenic in immunocompromised hosts and premature infants; commonly a contaminant
Streptococcus pyogenes (Group A) Deep wounds or intra-abdominal abscess, bloodstream infections	Upper respiratory tract, perianal area (rectum and vagina)	Carriage among health care workers	P = wound, stool cultures E = settle plates	Not commonly normal flora; threshold for a health care–associated investigation: 1 case
Varicella infections Skin, respiratory Disseminated or localized infection	Secretions and skin lesions	Poor ventilation	P = viral cultures, PCR or serology E = not known to be useful	Children and immunocompromised patients at risk Unvaccinated exposed can develop disease
Yersinia enterocolitica Bloodstream, GI tract	GI tract	Packed red blood cells	P = micro cultures E = cultures of potentially implicated items	––

Abbreviations: IV, intravenous; NICU, neonatal intensive care unit; PCR, polymerase chain reaction; PFGE, pulse field gel electrophoresis.