CLIN. CHEM.
30/11, 1875-1876
(1984)
Lactate Production by Aerobic Bacteria Grown in Cerebrospinal Fluid
Frederick
L. Kiechle, Mary A. Kamela, and Robert W. Starnes
The source of the abnormally high concentration of lactate in
not known. It may represent a bacterial metabolite. To
The microtiter
tray was incubated in a moist chamber at
37 #{176}C.
Before and 2,4,6, and 24 h after the inoculation, CSF
lactate and glucose were determined.
determine whether cerebrospinalfluid possesses appropriate substratesto supportthe growth of pathogenicaerobic
Results and Discussion
the cerebrospinalfluid in patientswith bacterialmeningitisis
bacteria, three Gram-positive and nine Gram-negative bactena were separately inoculated in pooled normal cerebrospinal fluid.After incubationfor 24 h, all Gram-positive bacteria
increased lactate, eight Gram-negative bacteria decreased
lactate,and one Gram-negativebacteriafailed to significantly
change the lactate concentration. We conclude that lactate
produced in cerebrospinal fluid in patients with aerobic
bacterial meningitis is not necessarily a bacterial metabolite.
AddItIonal
Keyphrases:
bacteria! meningitis
An abnormally high concentration of lactate in cerebrospinal fluid (CSF) may aid in distinguishing bacterial or
fungal meningitis from viral meningitis
and aseptic processes (1-3). However, significant overlap of these diagnostic
groups has also been reported (4). There is a blood-brain
and blood-CSF barrier for lactate. CSF lactate originates in
the central nervous system and not in blood. However, the
source of lactate within the central nervous system in cases
of bacterial meningitis is unknown.
It may represent a
bacterial metabolite, a leukocyte
metabolite, leakage from
injured
cells lining the fluid spaces, or an increase in
anaerobic glycolysis secondary to tissue hypoxia. Not all
aerobic bacteria produce lactate when grown in a welldefined blood-culture medium (5). We wanted to determine
whether CSF possesses sufficient substrates for potential
pathogenic aerobic bacteria to produce lactate.
Materials and Methods
We inoculated
various aerobic bacteria in pooled CSF
from patients with lactate concentrations
witin the normal
range (0.5-2.2 mmol/L).
Twelve stock bacterial
Table 1 summarizes the results. After 2 h of incubation at
37 #{176}C,
three of three Gram-positive bacteria increased CSF
lactate and decreased CSF glucose concentrations as compared with the initial pre-inoculation values for pooled CSF.
The two pathogenicstreptococciusedin these experiments
and others are homolactate fermenters (6); i.e., they form
lactate as the major end product of glycolysis. Proteus
vulgaris failed to alter CSF lactate or glucose values significantly. Eight of mne Gram-negative bacteria decreased both
CSF lactate and glucose after 24 h, suggesting that after
glucose
was depleted as an energy source, lactate was
utilized (7).
Of the various pathogenic
aerobic bacteria tested, 75%
failed to produce lactate in CSF, possibly owing to insufficient substrate for these aerobic bacteria to generate this
organic acid. Many Gram-negative bacteria appear to utilize
lactate as a carbon source during intracellular metabolism.
We conclude that lactate produced in CSF in patients with
aerobic bacterial meningitis is not necessarily a bacterial
metabolite.
Table 1. Lactate and Glucose Concentration In
Pooled CSF at Various Intervals after Inoculation
with Aerobic Bacteria
Bacteria
Streptococcus
pyogenes
Streptococcus
faecai is
2
Hours Incubated
4
6
24
irrnol/L
Lactate
chanoe.
4.6(250)
+3.5
+318
1.0(440) 0.8(430)
3.6(120)
+2.5
+227
1.4(640) 1.6(660)
1.8(320)
+0.7
+
1.2(480)
1.5(640)
1.0(440)
Staphylococcus 1.1(470)
aureus
1.2(480)
Proteus
Change at
24 h,”
1.4(600)
t
64
1.5(640) 1.6(670) 1.6(530)
+0.5
+ 45
cultures were selected and incuvuigari S
bated in Trypticase Soy Broth (Baltimore BiologicalLabora0.8(460) 1.2(470) 1.5(680) 0.9( 10)
-0.2
tories, Cockeysville,
MD 21030) for 4 to 6 h at 37 #{176}C.[scherichia
coli
Dilutions were made in this medium and the number of
1.2(550)
1.2(500)
1.5(630)
Enterobacter
0.8(
0)
-0.3
colony-forming units per milliliter
(CFU/mL) was detercioacae
1.1(510) 1.3(620) 1.5(660) 0.7) 10)
-0.4
- 36
Enterobacter
mined. We chose a bacterial dilution in Trypticase Soy
aerogenes
Broth that would yield i0 to 108 CFU/mL, and used a 100.9(510) 1.3(580) 1.5(670) 0.5(230)
-0.6
Serratia
- 54
fold dilution of this in sterile saline for CSF inoculation.
marcoscent
Bacterial viability was confirmed in the saline dilutions.
1.3(550) 1.4(590) 1.3(550) O.3( 10)
Salmonella
-0.8
- 73
typhimurium
CSF lactate (3) and glucose were measured in an aca
Citrobacter
2.0(470) 1.4(640) 1.2(520) 0.1( 0)
-1.0
- 91
discrete analyzer (Dii Pont, Wilmington, DE 19898) by
freundiI
enzymic methods involving lactate dehydrogenase (EC
-1.1
-100
Pseudomonas 1.1(480) 1.4(640) 1.5(690) 0 ( 40)
aeruginosa
1.1.1.27) and hexokinase (EC 2.7.1.1), respectively. CSF was
1.2(540) 1.2(570) 1.0(410) 0 ( 40)
-1.1
-100
Klebsiella
pooled from patients with CSF lactate concentrations of
pneumoniae
<2.2 mmol/L and stored at 4#{176}C.
Pooled CSF (180 tL) was
+0.1
+9
1.2(540) 1.2(520) 1.2(500) 1.2(530)
Control
placed in the wells of a microtiter tray and inoculated with
20 tL of the appropriate bacterial dilution in isotonic saline.
The difference in the lactate value following 24 h of incubation minus the
pre-inoculation lactate value (1.1 mmol/L). The pre-inoculation pooled CSF
Department of Clinical Pathology, William Beaumont Hospital,
Royal Oak, MI 48072.
Received August 20, 1984; accepted September 7, 1984.
-
18
-
27
glucose was 500 mg/L. CSF glucose values are in parentheses (mg/L).The
controlwas inoculatedwith 20 pcLof a 10-folddilutionof Trypticase Soy Broth
in sterile saline.
CLINICAL CHEMISTRY,Vol. 30,
No.11,1984
1875
References
1. KnightJA, Dudek SM, Haymond RE. Early (chemical) diagnosis
of bacterial
meningitis-cerebrospinal fluid glucose,lactate and
lactate dehydrogenasecompared. Clin Chem 27, 1431-1434(1981).
2. Brook I. The importance of lactic acidlevelsin body fluids in the
detection of bacterial infections. Rev Infect Dis 3, 470-478 (1981).
3. Herold DA, Savory J, Bruns DE. Lactic acid in cerebrospinal
fluid: Evaluation and application of an automated enzymatic assay.
Ann Clin Lab Sci 11, 416-421 (1981).
1876
CLINICAL
CHEMISTRY,
Vol. 30, No. 11, 1984
4. Jordan GW, Statland B, Halsted C. CSF lactate in diseases of the
CNS. Arch Intern Med 143, 85-87 (1983).
5. Kiechle FL, Starnes RW, Colville JM. Production of lactate by
aerobic bacteria. Clin Chem 28, 1984-1986 (1982).
6. Doelle HW. Bacterial Metabolism, Academic Press, New York,
NY, 1969, pp 330-351.
7. Ludvigsen CW, Eckfeldt JH, Peterson LR. In vitro alteration of
lactate concentration in cerebrospinal fluid. Am J Clin Pathol 78,
136 (1982).