Pseudoinfections and Pseudo-Outbreaks

Cheston B. Cunha

Burke A. Cunha

From an infection control and clinical perspective, pseudoinfections are interesting and important. On a daily basis, there are many concerns confronting infection preventionists (IPs) in reviewing clinical and microbiologic data. Given the high volume of microbiologic data generated per day, it is understandable that IPs particularly take notice of common microorganisms cultured/demonstrated from unusual body sites (for the microorganism) (e.g., Streptococcus pneumoniae from a wound culture) as well as unusual microorganisms cultured/demonstrated from any body site (e.g., Chromobacterium violaceum from respiratory secretion cultures). Potential pseudoinfection should be suspected either when an unusual microorganism is cultured from a usual body site (e.g., Alcaligenes [Achromobacter] xylosoxidans cultured from the urine) or when a common microorganism is isolated from an unusual body site (for the microorganism) (e.g., Bacteroides fragilis cultured from the cerebrospinal fluid [CSF]). The clue to possible pseudoinfection is a discrepancy between clinical findings and the typical manifestations of the isolate at the body site cultured/demonstrated (e.g., Pseudomonas fluorescens cultured from the blood in a patient with pneumonia). IPs should then determine by epidemiologic investigation whether the isolate represents a bona fide infection or pseudoinfection.

An abrupt increase in incidence of a microorganism relative to its prevalence in an institution should suggest a potential outbreak. Outbreaks are clusters of the same infection occurring over a limited period of time but must be differentiated from pseudo-outbreaks. A pseudo-outbreak may be defined as a cluster of pseudoinfections due to the same microorganisms cultured/demonstrated from the same site in multiple patients. Whenever a pseudoinfection is suspected, infection control should conduct an appropriate epidemiologic investigation to try and determine the common source of microbial contamination and mechanism of specimen contamination.

Infectious disease clinicians deal with other problems trying to correlate microbiologic results with clinical findings. On a daily basis, physicians must differentiate colonization from infection not only for accurate record keeping/diagnostic purposes but also to avoid unnecessary treatment of colonization, which may predispose to antimicrobial resistance.

Some patients with pseudoinfections are empirically treated with antimicrobial therapy before the diagnosis of pseudoinfection is realized. The more potentially serious the infection (e.g., bacteremia, meningitis, pneumonia), the more likely pseudoinfections will be treated empirically with antibiotics. In some cases, whenever an isolate is clearly unrelated to the clinical presentation (e.g., Bacillus subtilis isolated from the CSF in a patient with altered mental status), pseudoinfection is likely and empiric antibiotic therapy is used less often.

Epidemiologic investigations associated with pseudoinfections are one of the most interesting aspects of infection control. Pseudoinfections and pseudo-outbreaks should be reported to guide others facing similar epidemiologic quandaries. The pseudoinfection literature provides a wealth of information that is instructive and useful to IPs in conducting a focused epidemiology investigation to determine the potential source of microbial contamination.

PSEUDOBACTEREMIAS

The first type of pseudoinfection described was pseudobacteremia, which remains the most frequently reported pseudoinfection. Microorganisms associated with pseudobacteremias have been varied, but the most frequently implicated microorganisms have been Bacillus species, Pseudomonas species, or Streptococcus species. The most common sources of pseudobacteremia have been contaminated culture media, contaminated antiseptic solutions, or contaminated blood culture vials. Inadequate needle sterilization of blood culture autoanalyzer parts has also been responsible for some pseudobacteremias. Less commonly, pseudobacteremias have resulted from contamination of blood specimens in the laboratory. Rarely, actual infections have occurred from accidental reflux of microbial contaminated blood into patients during venipuncture (1,2,3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,32,33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,51,52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72) (Table 9-1).

PSEUDOMENINGITIS

Pseudomeningitis is the second most common type of pseudoinfection and should be suspected when nonneuropathogens are cultured from CSF in patients with altered mental

status. The microorganisms most often implicated in pseudomeningitis are aerobic gram-negative bacilli/coccobacilli. The recovery of nonneuropathogens from the CSF in patients with altered mental status should suggest pseudomeningitis. As with other types of pseudoinfections, pseudomeningitis should be suspected when there is a discrepancy between the clinical presentation and the findings typical of the neuropathogen (e.g., Candida albicans isolated from the CSF in a neonate with fever and neurologic findings). Since C. albicans is a rare cause of fungal meningitis, the C. albicans cultured from the CSF should suggest the possibility of pseudoinfection. In pseudomeningitis, the source of specimen contamination is usually due to extrinsic contamination of lumbar puncture kit materials (e.g., slides, CSF tubes, CSF culture media). Alternately, contamination of CSF has occurred during specimen processing in the laboratory. Because of the mortality/morbidity associated with bacterial meningitis, patients with pseudomeningitis are likely to be given empiric antimicrobial therapy (73,74, 75, 76,77,78,79,80, 81, 82, 83, 84, 85, 86, 87, 88,89,90, 91, 92, 93, 94) (Table 9-2).

TABLE 9-1 Pseudobacteremia

*(Reference) Year*	*Microorganisms*	*Number Affected*	*Number Infected*	*Number Treated*	*Cause/Source*
(1) 1969	Escherichia coli	7	0	7	Contaminated penicillinase in blood culture media
(2) 1972	Acinetobacter lwoffi	27	3	4	Contaminated penicillinase in blood culture media
(3) 1973	Moraxella nonliquefaciens	8	1	1	Contaminated tube holders of blood culture tubes
(4) 1974	Bacillus species	26	0	0	Contaminated blood culture media
(5) 1976	Pseudomonas cepacia	79	3	4	Contaminated benzalkonium chloride used for venipuncture
(6) 1976	Flavobacterium Meningosepticum	6	0	0	Contaminated chlorhexidine solution used for venipuncture
(7) 1976	Serratia marcescens	40	0	0	Cross-contamination of blood cultures with nonsterile blood collection tubes
(8) 1977	Acinetobacter lwoffi	11	0	2	Improper blood culture technique in a mist tent heavily contaminated with bacteria
(9) 1978	Pseudomonas maltophilia	25	1	3	Cross-contamination of blood cultures with bacteria from nonsterile blood collection tubes
(10) 1979	Staphylococcus aureus	11	0	5	Blood cultures contaminated by a colonized (nasopharynx) laboratory technician
(11) 1980	Clostridium sordellii	11	0	0	Contaminated thimerosal solution/diaphragms of blood culture media
(12) 1980	Acinetobacter lwoffi	22	0	0	Blood cultures contaminated
(13) 1980	Staphylococcus aureus	5	0	0	Blood culture media contaminated by physician
(14) 1980	Aerococcus viridans	7	0	0	Inadequately disinfected blood culture bottle stoppers
(15) 1981	Pseudomonas cepacia	30	0	0	Contaminated povidone-iodine solution used for venipuncture/disinfection of blood culture bottle stoppers
(16) 1981	Enterobacter cloacae	7	0	1	Contaminated thrombin in blood culture collection vials
(17) 1981	Klebsiella pneumoniae	13	7	6	Contaminated sampling needle in automated blood culture analyzer
(18) 1981	Gram-negative bacilli	75	0	NK^a	Improper blood culture collection technique
(19) 1981	Pseudomonas cepacia	16	0	2	Contaminated povidone-iodine solution
(20) 1982	Klebsiella pneumoniae Streptococcus pyogenes Staphylococcus epidermidis	2 1 1	0	1	Inadequate needle sterilization in automated blood culture analyzer
(21) 1982	Bacillus species	36	0	0	Contaminated syringes
(22) 1982	Serratia marcescens	17	0	NK	Improper blood culture collection technique
(23) 1982	Serratia marcescens	16	0	2	Cross-contamination with blood gas specimens
(24) 1982	Pseudomonas aeruginosa	17	0	0	Contamination of blood culture processing equipment
(25) 1983	Bacillus species	15	0	0	Contaminated cotton swabs used to disinfect blood culture bottles
(26) 1983	Pseudomonas stutzeri	24	1	21	Contaminated green soap solution
(27) 1983	Enterobacter faecalis	8	0	2	Cross-contamination in automated blood culture analyzer
(28) 1983	Pseudomonas maltophilia	5	0	0	Contaminated sodium citrate solution, improper blood culture technique
(29) 1983	Bacillus species	15	0	0	Contaminated brain-heart infusion broth
(30) 1984	Staphylococcus aureus Staphylococcus epidermidis Streptococcus species Escherichia coli	11 10 1 1	0	3	Inadequate needle sterilization in blood culture analyzer
(31) 1984	Streptococcus bovis	1	0	1	Inadequate cleaning of needle in automated blood culture analyzer
(32) 1984	Bacillus species	26	0	1	Spore contamination of needle in automated blood culture analyzer
(33) 1985	Streptomyces species	7	0	0	Airborne contamination of clinical specimens 2° to construction
(34) 1985	Pseudomonas cepacia	2	0	NK^a	Contaminated antiseptic handwash
(35) 1985	Pseudomonas pickettii	21	0	NK	Contaminated aqueous chlorhexidine solution
(36) 1985	Pseudomonas fluorescens	57	0	0	Cross-contamination from contaminated citrated blood collection tubes
(37) 1987	Enterococcus species Staphylococcus aureus	17 5	0 0	2 NK	Contaminated radiometric blood culture device
(38) 1987	Ewingella americana	20	0	14	Cross-contamination of blood culture bottles with bacteria from nonsterile tubes
(39) 1988	Pseudomonas cepacia	2	0	NK	Contaminated blood gas analyzer
(40) 1989	Streptococcus viridans	41	0	NK	Blood cultures contaminated by colonized laboratory technician with dermatitis
(41) 1989	Streptococcus species, Staphylococcus aureus	7	0	1	Blood cultures contaminated by a colonized laboratory technician with positive nasopharyngeal cultures
(42) 1990	Bacillus species	10	0	6	Blood cultures contaminated by nonsterile gloves used by phlebotomists
(43) 1991	Candida guilliermondii	17	0	2	Contaminated heparin vials used for blood culture collection
(44) 1991	Enterobacter cloacae	13	0	0	Nonaseptic processing of culture media
(45) 1993	Pseudomonas pickettii	27	0	0	Nonaseptic blood culture collection
(46) 1993	Pseudomonas cepacia	27	0	0	Contaminated EDTA in blood culture bottles
(47) 1993	Alcaligenes xylosoxidans, Xanthomonas maltophilia, Klebsiella oxytoca, Corynebacterium aquaticum	16	0	0	Nonsterile blood culture collection/processing
(48) 1994	Mycobacterium avium-intracellulare	30	0	1	Cross-contamination of culture media
(49) 1994	Pseudomonas fluorescens	11	0	0	Breakdown in aseptic technique
(50) 1994	Gram-variable bacilli	1	0	1	Contaminated culture plate
(51) 1994	Enterobacter agglomerans	37	0	0	Nonsterile blood collection tubes
(52) 1996	Burkholderia cepacia	13	0	4	Contaminated blood gas analyzer
(53) 1997	Mycobacterium abscessus	23	0	0	Probably due to contaminated lysis centrifugation tube
(54) 1998	Candida parapsilosis	29	0	0	Contamination of blood culture bottles by laboratory technician
(55) 1999	Pseudomonas fluorescens	12	0	8	Contaminated lithium heparin bottles
(56) 1999	Pseudomonas fluorescens	53	0	0	Contaminated lithium heparin bottles
(57) 1999	Serratia marcescens	2	0	2	Contaminated blood glucose/lactate analyzer
(58) 1999	Staphylococcus saccharolyticus	6	0	NK	Inadequate venipuncture skin site preparation
(59) 1999	Agrobacterium radiobacter	15	0	NK	Contaminated blood culture tubes
(60) 1999	Enterococcus faecium	4	0	NK	Phlebotomist contaminated blood culture bottles
(61) 1999	Pseudomonas fluorescens, Comamonas acidovorans	7	0	NK^a	Contaminated lithium heparin bottles
(62) 1996	Burkholderia cepacia	13	0	4	Contaminated blood gas analyzer
(63) 2000	Bacillus megaterium	1	0	0	Contaminated blood culture bottle tops
(64) 2001	Paenibacillus macerans	8	0	8	Contaminated blood culture bottles
(65) 2005	Volvox globator	1260	0	0	Contaminated blood culture media
(66) 2006	Ralstonia pickettii	6	0	2	Contaminated disinfectant solution
(67) 2007	Achromobacter xylosoxidans	58	0	8	Contaminated chlorhexidine containers
(68) 2007	Ochrobactrum anthropi	8	0	8	Contaminated ESR tubes
(69) 2007	Candida guilliermondii	149	0	8	Contaminated blood collection tubes
(70) 2007	Bacillus species	60	3	3	Dust contamination from ventilation system
(71) 2009	Pseudomonas oryzihabitans	4	0	0	None identified
(72) 2010	Alcaligenes faecalis	9	0	0	Contaminated blood collection tubes
^aNK, not known.

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Tags: Hospital Epidemiology and Infection Control

Jun 22, 2016 | Posted by drzezo in GENERAL & FAMILY MEDICINE | Comments Off

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