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Time to blood cultures positivity of microorganisms using a continuous-monitoring automated blood cultures system

Pajaree Krisanapan
Pajaree Krisanapan
 and 
Romanee Chaiwarith
Romanee Chaiwarith
   | Dec 19, 2019
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Article Category: Original article
Published Online: Dec 19, 2019
Page range: 61 - 69
DOI: https://doi.org/10.1515/abm-2019-0041
Keywords
© 2019 Krisanapan and Chaiwarith, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Figure 1

Blood cultures recruited for this study.
Blood cultures recruited for this study.

Clinical characteristics of 195 episodes of infections

CharacteristicsNumber (%) N = 195
Clinical presentations
  Fever143 (73.3)
  Dyspnea37 (19.0)
  Abdominal pain, diarrhea, nausea, vomiting35 (18.0)
  Altered mental status30 (15.4)
  Dysuria, flank pain, or cloudy urine14 (7.2)
Source of infection
  Genitourinary tract30 (15.4)
  Gastrointestinal and hepatobiliary tract29 (14.9)
  Central venous catheter related25 (12.8)
  Respiratory tract15 (7.7)
  Skin, bone, joint, and soft tissue12 (6.2)
  Endocarditis and vascular system8 (4.1)
  Unidentified72 (36.9)
Prior antimicrobial uses Type of antimicrobials63 (32.3)
  Antibiotics62 (31.8)
   Cephalosporins16 (8.2)
   Carbapenems14 (7.2)
   Quinolones14 (7.2)
   Vancomycin13 (6.7)
   Metronidazole12 (6.2)
   Penicillin9 (4.6)
   Trimethoprim/sulfamethoxazole5 (2.6)
   Colistin3 (1.5)
   Macrolides1 (0.5)
   Aminoglycosides1 (0.5)
   Others3 (1.5)
  Antifungals9 (4.6)
Current use of antimicrobials at the time blood cultures were taken55 (28.2)

The cumulative median time to positivity for particular microorganisms

MicroorganismsNNumber (%) of organisms recovered on hours
≤12≤24≤48≤72≤96≤120
Overall490142 (29)367 (75)462 (94.3)478 (97.6)489 (99.8)490 (100)
Bacteria433141 (32.6)347 (80.1)415 (95.8)425 (98.2)433 (100)433 (100)
   Gram-positive bacteria21449 (22.9)166 (77.6)202 (94.4)210 (98.1)214 (100)214 (100)
    Staphylococci12318 (14.6)94 (76.4)119 (96.8)123 (100)123 (100)123 (100)
    Coagulase-negative staphylococci675 (7.5)48 (71.6)65 (97)67 (100)67 (100)67 (100)
    Staphylococcus aureus5613 (23.2)46 (82.1)54 (96.4)56 (100)56 (100)56 (100)
    Streptococci5025 (0.5)46 (92)48 (96)49 (98)50 (100)50 (100)
    True pathogens14442 (28.2)124 (86.1)139 (96.5)143 (99.3)144 (100)144 (100)
    Contaminants707 (10)42 (60)63 (90)67 (95.7)70 (100)70 (100)
   Gram-negative bacteria21992 (42)181 (82.6)213 (97.3)215 (98.2)219 (100)219 (100)
    Escherichia coli5530 (54.6)48 (87.3)54 (98.2)54 (98.2)55 (100)55 (100)
    Klebsiella pneumoniae3525 (71.4)34 (97.1)35 (100)35 (100)35 (100)35 (100)
    Pseudomonas aeruginosa28020 (71.4)28 (100)28 (100)28 (100)28 (100)
    Acinetobacter baumannii1711 (64.7)17 (100)17 (100)17 (100)17 (100)17 (100)
    Aeromonas spp.1712 (70.6)16 (94.1)17 (100)17 (100)17 (100)17 (100)
    Salmonella spp.146 (42.9)13 (92.9)14 (100)14 (100)14 (100)14 (100)
    Burkholderia spp.1007 (70)8 (80)8 (80)10 (100)10 (100)
Yeast and other fungi571 (1.8)20 (35.1)47 (82.5)53 (93)56 (98.3)57 (100)

List of microorganisms and time to positivity

MicroorganismsNumber of blood cultures (%)Median time to positivity (hours) (IQR)
Overall490 (100)17 (11.5, 24.5)
Bacteria433 (88.4)15.5 (11.5, 22)
Gram-positive bacteria214 (43.7)17.5 (12.5,23)
    Staphylococci123 (25.1)19 (15, 23.5)
     Coagulase-negative staphylococci67 (13.7)20.5 (18, 25)
     Staphylococcus aureus56 (11.4)15.5 (12.5, 20.25)
    Streptococci50 (10.2)12.25 (9.5, 15.5)
     Streptococcus bovis15 (3.1)10 (8.5, 12.5)
     Streptococcus pneumoniae5 (1.0)10 (5, 12)
     Streptococcus pyogenes5 (1.0)11 (10, 12)
     Streptococcus agalactiae5 (1.0)5.5 (5.5, 6)
     Other Streptococci20 (4.1)15.5 (14, 17.25)
   Bacillus spp.22 (4.5)17.25 (12.5, 25.5)
   Enterococcus faecium7 (1.4)17.5 (16.5, 19)
   Corynebacterium spp.7 (1.4)26.5 (23, 58.5)
   Micrococcus spp.3 (0.6)87 (57, 90)
   Listeria monocytogenes2 (0.4)19.5 (19.5, 19.5)
Gram-negative bacteria219 (44.7)14 (10.5, 20)
    Escherichia coli55 (11.2)12 (10.5, 15)
    Klebsiella pneumoniae35 (7.1)10.5 (9.5, 13)
    Pseudomonas aeruginosa28 (5.7)21 (17.5, 25.25)
    Acinetobacter baumannii17 (3.5)11 (10, 12.5)
    Aeromonas sobria and A.hydrophilla17 (3.5)10.5 (9, 13)
    Salmonella spp.14 (2.9)12.5 (10.5, 16.5)
    Burkholderia cepacia10 (2.0)22.25 (20, 39)
    Enterobacter cloacae and Enterobactor spp.8 (2.0)22.5 (14.25, 54)
    Stenotrophomonas8 (1.6)18.5 (16.25, 26.5)
    maltophilia
    Proteus mirabilis5 (1.0)14 (13.5, 17)
    Elizabethkingia meningoseptica4 (0.8)13.75 (12.25, 15)
    Citrobacter freundii and C. koseri3 (0.6)10.5 (10.5, 13)
    Serratia marcescens3 (0.6)18 (17, 29)
    Neisseria gonorrhoeae2 (0.4)29.5 (29,30)
    Vibrio vulnificus2 (0.4)8.5 (8.5, 8.5)
    Campylobacter spp.1 (0.2)45
    Unidentified Gram-negative bacilli7 (1.4)32 (28.5, 43)
Yeast and other fungi57 (11.6)27.5 (22, 38)
   Candida spp.55 (11.2)27 (22, 36.5)
      Candida tropicalis14 (2.9)19.8 (19, 22)
      Candida albicans10 (2.0)40.5 (34, 54)
      Candida parapsilosis3 (0.6)41.5 (26.5, 87.5)
      Candida guilliermondii3 (0.6)28 (26, 30)
      Candida glabrata3 (0.6)61.5 (60.5, 71)
      Unidentified Candida spp.22 (4.5)27.8 (25.5, 31)
   Talaromyces (Penicillium) marneffei1 (0.2)110.5
   Unidentified dematiaceous fungi1 (0.2)82.5

Demographic characteristics of 181 patients whose blood cultures grew true pathogens

CharacteristicsNumber (%) N = 181
Male100 (55.2)
Age (years) (median, IQR)61 (50, 76)
Location where blood cultures were drawn
  Inpatient units164 (90.6)
   Critical care units42 (23.2)
   Noncritical care units122 (67.4)
     Medicine110 (60.8)
     Surgery43 (23.8)
     Orthopedics5 (2.8)
     Obstetrics and gynecology3 (1.7)
     Others3 (1.7)
 Outpatient department10 (5.5)
 Emergency department7 (3.9)
Underlying diseases145 (80.1)
 Malignancy63 (34.8)
   Hematologic malignancy18 (9.9)
   Solid organ malignancy45 (24.9)
  Advanced chronic kidney disease23 (12.7)
  (GFR <30 mL/min/1.73 m2)
   Diabetes21 (11.6)
   Disease result in neurocognitive impairment14 (7.7)
   Symptomatic heart failure or ejection fraction <40%13 (7.2)
   Cirrhosis12 (6.6)
   Hydronephrosis8 (4.4)
   HIV infection7 (3.9)
   Chronic obstructive lung disease5 (2.8)
   Gastrointestinal fistula5 (2.8)
   Rheumatologic disease3 (1.7)
   Post splenectomy3 (1.7)
   Post organ transplant3 (1.7)
   Aplastic anemia2 (1.1)
   Adult onset immunodeficiency syndrome1 (0.6)
Received immunosuppressive agents34 (18.8)

Median time to positivity comparing true pathogens and contaminant blood cultures

OrganismTotal numberTrue pathogenContaminant blood cultures
Number (%)TTP (IQR)Number (%)TTP (IQR)
Overall490420 (85.7)16 (11.5, 23)70 (14.3)23 (18.5, 28)
Gram-positive bacteria214144 (67.3)15.5(12, 19)70 (32.7)23(18.5, 28)
   Coagulase-negative staphylococci6729 (43.3)18.5 (16.5, 20.5)38 (56.7)22 (19.5, 25.5)
   Bacillus spp.220–22 (100)17.25 (12.5, 25.5)
   Corynebacterium spp.70–7 (100)26.5 (23, 58.5)
   Micrococcus spp.30–3 (100)87 (57, 90)

Clinical parameter of 195 episodes of infections

Sepsis parametersTotal number of available dataNumber (%)
Body temperature <36 or >38.3°C191134 (70.2)
Heart rate >90 beat/min191168 (88.0)
Respiratory rate >20/min190105 (55.3)
Hypotension or shock19156 (29.3)
Altered mental status19130 (15.7)
Acute lung injury15327 (17.6)
Decrease urine output14122 (15.6)
Creatinine >2.0 mg/dL or increase >0.5 mg/dL16243 (26.5)
Lactate level (mmol/L) (median, IQR)953.0 (1.7, 6.2)
Lactate level >1.0 mmol/L9591 (95.8)
White blood cells (×103 cells/mm3) (median, IQR)19512.5 (7.7, 17)
White blood cells <4,000 or >12,000 cells/mm3195136 (69.7)
Platelet count (×103 per/mm3) (median, IQR)194161 (70, 261)
Platelet count <100,000/mm319471 (36.6)
Clinical systemic inflammatory response syndrome191172 (90.0)

Comparisons of characteristics of patients with positive blood culture within 24 hours and >24 hours

CharacteristicsNumber of patients (%)P
TTP ≤ 24 hours (N = 367)TTP >24 hours (N = 123)
Male206 (56.1)75 (61.0)0.400
Underlying diseases300 (81.7)101 (82.1)1.000
  Malignancy134 (36.5)32 (26.0)0.037
   Hematologic malignancy50 (13.6)1 (0.8)<0.001
   Solid organ malignancy84 (22.9)31 (25.2)0.624
  Receiving immunosuppressive agents78 (21.2)13 (10.6)0.007
  Diabetes mellitus37 (10.1)9 (7.3)0.475
  Cirrhosis19 (5.2)4 (3.2)0.468
  HIV infection13 (3.5)2 (1.6)0.376
  Post splenectomy4 (1.1)1 (0.8)1.000
  Post organ transplant6 (1.6)3 (2.4)0.698
Clinical presentations
  Fever277 (76.5)90 (75.0)0.805
  Dyspnea79 (21.8)20 (16.7)0.243
  Altered mental status58 (16.0)9 (7.5)0.022
Source of infections
  Genitourinary tract41 (11.2)12 (9.8)0.739
  Gastrointestinal and hepatobiliary system44 (12.0)21 (17.1)0.167
  Catheter related52 (14.2)28 (22.8)0.034
  Respiratory tract23 (6.3)4 (3.2)0.258
  Skin, bone, joint, and soft tissue21 (5.7)5 (4.1)0.643
  Endocarditis and vascular system22 (6.0)1 (0.81)0.014
  Central nervous system2 (0.5)01.000
Prior antimicrobials uses within 72 hours129 (35.6)64 (53.3)0.001
  Carbapenems35 (9.5)22 (17.9)<0.001
  Vancomycin23 (6.3)25 (20.3)<0.001
  Antifungals17 (4.6)20 (16.3)<0.001
Current uses of antimicrobials at the time of blood culture taken115 (32.5)63 (51.2)<0.001
Indwelling intravascular catheters114 (31.1)55 (44.7)0.008
Clinical systemic inflammatory response syndrome337 (93.1)99 (83.2)0.003
  Body Temperature <36°C or >38.3°C246 (68.3)75 (63.6)0.367
  Heart rate >90 beats/min336 (91.6)110 (89.4)0.470
  Tachypnea213 (59.7)66 (55.5)0.452
  Hypotension or shock116 (32.0)46 (38.3)0.221
  Altered mentation62 (21.0)14 (14.9)0.233
  Acute lung injury51 (17.7)14 (14.3)0.532
  Lactate >3 mmol/L100(59.5)18 (32.7)0.001
  White blood cells <4,000 cells/mm368 (18.5)9 (7.4)0.003
  Platelet count <100,000/mm3127(34.6)24 (19.7)0.002
Gram-positive bacteria166 (47.8)48 (55.)0.228
Gram-negative bacteria181 (52.2)38 (44.2)0.228
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