Quantitative blood cultures in the diagnosis of sepsis in infants with umbilical and Broviac catheters

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Clinical and laboratory observations

Jaff~ reaction: a comparison of three methods. Clin Chem 1968;14:222-38. 9. Ellis G, Diamandis EP, Giesbrecht EP, Daneman D, Allen LC. An automated high-pressure liquid chromatographic assay for hemoglobin Alc. Clin Chem 1984;30:1746-52. 10. Jefferson IG, Greene SA, Smith MA, Smith RF, Griffen NKG, Baum JD. Urine albuminto creatinine ratio response to exercise in diabetes. Arch Dis Child 1985;60:305-10. 11. Schmitz A. Microatbutest: a new screening method for

The Journal of Pediatrics May 1988 detecting microalbuminuria in diabetes mellitus. Uremia Invest 1985-86;9(2):79-84. 12. Cowell CT, Rogers S, Silink M. First morning urinary albumin concentration is a good predictor of 24-hour urinary albumin excretion in children with type l (insulin-dependent) diabetes. Diabetotogia 1986;29:97-9. 13. Ginsberg JM, Chang BS, Matarese RA, Garella S. Use of single voided urine samples to estimate quantitative proteinuna. N Engl J Med t983;309:1543-6.

Quantitative blood cultures in the diagnosis of sepsis in infants with umbilical and Broviac catheters J e a n n e W. R u d e r m a n , MD, M a r g i e A. M o r g a n , PhD, a n d A l a n H. Klein, MD From the Departments of Pediatrics and Microbiology, Cedars-Sinai Medical Center, University of California, Los Angeles, School of Medicine

Paired quantitative blood cultures drawn from an indwelling Broviac catheter and a peripheral vein have been shown to be helpful in diagnosing catheter-related sepsis in children j and adults. 2,3 Our current study was performed to investigate the usefulness of paired quantitative blood cultures in diagnosing catheter-related sepsis in infants with either an umbilical artery catheter or a Broviac venous catheter.

METHODS Over a 2-year period, 63 infants older than 1 week of age, with an indwelling Argyle polyvinyl chloride umbilical artery catheter or a single-lumen Broviac venous catheter, and suspected sepsis, were prospectively studied at the Cedars-Sinai Medical Center Neonatal Intensive Care Unit. A blood sample, 0.5 to 1 ml, was drawn from a peripheral blood vessel and from the central catheter. Aseptic technique at the peripheral site included three applications of povidone-iodine followed by one application of 70% isopropyl alcohol to the skin. A butterfly needle and a sterile syringe were used for phlebotomy. Aseptic technique at the catheter was as follows: (1) the catheter was clamped and the needle adapter removed, (2) the end of the catheter was swabbed three times with povidone-iodine and once with 70% isopropyl alcohol, (3) a sterile needle adapter was inserted into the end of the catheter, (4) the

Submitted for publication July 6, 1987; accepted Nov. 16, 1987. Reprint requests: Jeanne W. Ruderman, MD, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Pediatrics Room 4310, Los Angeles, CA 90048.

clamp was removed and 2 ml of blood was drawn through a sterile syringe to clear the catheter, (5) the blood for culture was then subsequently obtained in a separate sterile syringe, (6) the initial 2 ml of blood was returned to the patient, and (7) the catheter adapter was reattached to the intravenous tubing. The paired blood specimens were placed in separate Du Pont Isolator 1.5 microbial tubes (Du Pont Co., Wilmington, Del.) after the stopper was swabbed three times with povidone-iodine. The tube was processed on receipt in the laboratory. The volume of blood collected was estimated at the time of plating by comparing the patient tube with standard tubes containing known volumes. Contents of the Isolator tube were inoculated onto one plate of chocolate agar, Brucella agar, and Haemophilus isolation medium. During the second year of the study, an additional processing step was added: 0.1 ml of a 1:10 dilution (0.1 ml of blood in 0.9 ml of tryptic soy broth ) was also plated on a chocolate agar plate. This afforded a better estimation of colony-forming units per milliliter in blood cultures with high colony counts. The chocolate and Haemophilus isolation medium agar plates were incubated in 5% CO2 at 35 ~ C, and the Brucella agar plate was incubated in an anaerobic jar at 35 ~ C. Agar media were examined for growth at 7 A.M. and 3 V.M. each day. Colony counts were done on all positive blood cultures. The number of colony-forming units (CFUs) per milliliter of blood was determined with the following formula: CFU/ml =

Total No. of CFU, all plates No. of plates on which organisms should grow X

No. of plates inoculated Blood volume in Isolator

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Table I. Group 1: Infants with sepsis CFU/mL Catheter

Catheter

Peripheral

U U U U U B U U

4 148 266 >300 >300 >300 426 540; 440

1 87 50 18 200 220 128 48; 0

U B B U U U B B B B B B U

1650 >3000 400 >3OO >300 >30O >300; >300 >300 >30O >300 >30O >30O >300O

533 490 400 >3O0 >300 >300 >300; >300 >300 >30O >300 >3O0 >30O >3O00

Organism(s)

No. of days

Coagulase-negativestaphylococcus

2

Staphylococcus aureus

t

Coagulase-negativestaphylococcus

2

Candida parapsilosis

2

Coagulase-negativestaphylococcus

1

Klebsiella pneumoniae

2

Coagulase-negativestaphylococcus Coagutase-negative staphylococcus and Enterococcus

1 1

C. parapsilosis Pseudomonas aeruginosa Escherichia coli Candida albicans

1 2 1 1

Coagulase-negativestaphylococcus Coagulase-negativestaphylococcus Enterococcus, Escherichia coli

I 1

K. pneumoniae Enterobacter cloacae Pseudomonas aeruginosa C. albicans Enterobacter cloacae

2 1 1 2 1 1

Enterococcus

2

U, umbilical;B, Broviac.

Single colonies growing outside the original inoculum streak were disregarded as plate contaminants. A Gram stain was performed on growth from all plates. Standard methods were employed for identification and antibiotic susceptibility testing of the organisms. RESULTS Ninety-seven paired blood cultures from 63 infants were obtained over a period of 2 years. Both the catheter and peripheral blood cultures were positive for growth in 21 cases. Infants in this group (group 1) were considered to have sepsis. The catheter blood culture was positive for growth, and the peripheral blood culture was negative for growth in 10 cases. Infants in this group (group 2) were considered to have catheter colonization without sepsis. In the remaining 66 cases, in which neither sepsis nor catheter colonization occurred (group 3), both the catheter and peripheral blood cultures were negative for growth in 59~ cases, and either the catheter or peripheral blood culture was positive for growth but considered to be a contaminated specimen in three and four cases, respectively. Colony counts in group 1 (sepsis) were over 50% greater in the catheter than in peripheral specimens in 10 of 21 cases, suggesting~catheter-related sepsis. Colony counts were equal in both the catheter and the peripheral specimen in one case, suggesting sepsis that was not catheter

related. Confluent growth in the remaining 10 pairs prohibited precise colony counts (Table I). In group 2 (catheter colonization without sepsis), there were fewer than 100 C F U / m l of microbial growth in four of 10 cases (Table II). Microbial growth of more than 100 CFU/ml occurred more frequently in the catheter blood culture during episodes of sepsis than during episodes of catheter colonization alone (P < 0.05). In those cases with a blood specimen considered to be positive because of contamination (group 3), colony counts were _<10 C F U / m l in six of seven cases, and 30 C F U / m l in the seventh case; growth consisted of organisms known to be skin contaminants (coagulase-negative staphylococci, a-hemolytic streptococci, and diphtheroids); and the duration of incubation was 3 to 4 days, in contrast to 1 to 2 days in cases of sepsis or catheter colonization. DISCUSSION Establishing a diagnosis of catheter-related sepsis is clinically important because it may be difficult to achieve eradication of organisms from the bloodstream when a colonized catheter remains in situ. Although recent studies in children4,5 show that the majority of cases of catheterrelated sepsis may be successfully treated with antibiotic therapy alone, catheter removal is sometimes required. Because the concentration of organisms is greatest near

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The Journal of Pediatrics May 1988

T a b l e II. Group 2: Infants with a colonized catheter in the absence of sepsis

CFU/mL Catheter U U U U U B B U B U

Catheter 17 29 33 87 155 300 1720 3390 >300 >300

Peripheral

Organism

Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative

Coagulase-negative staphylococcus Coagulase-negative staphylococcus Coagulase-negative staphylococcus Coagulase-negative staphylococcus Coagulase-negative staphylococcus Coagulase-negative staphylococcus Group B streptococcus Coagulase-negative staphylococcus Coagulase-negative staphylococcus Enterobacter cloacae

Days

u, umbilical;B, Broviac.

the source of an infection, 6 the concentration of organisms should be greater in a blood culture specimen drawn through a catheter than from a peripheral site when sepsis is catheter related. This theory is confirmed in case reports of adults with Broviac catheter-related sepsis 2.3 and in a prospective study of children with Broviac catheter-related sepsis5 We performed this current study to determine whether paired quantitative blood cultures drawn from a central catheter and a peripheral vessel could identify catheter-related sepsis in infants. Catheter colonization in the absence of sepsis has been recognized as a problem since indwelling central catheters were introduced to neon~/tial care in the 1960s. Historically, the diagnosis was made on removal of the catheter. 7,8 There are several problems associated with establishing the diagnosis in this manner. First, the umbilical stump or Broviac exit site cannot always be reliably sterilized) so there is a chance that the catheter may become contaminated on removal. Second, routine culture and sensitivity testing is not as accurate as the more complicated semiquantitative culture method 9 and the direct Gram stain. ~~ In addition, removal of the catheter may not be optimal for patient care. It is the practice in our neonatal unit to remove a colonized catheter if the catheter is not thought to be critically needed; otherwise, sterilization of the catheter with antibiotic therapy is attempted. Thus the paired blood culture method is an attractive alternative for diagnosing catheter colonization in the absence of sepsis. Quantitative blood cultures in earlier studies were grown after inoculation of blood onto agar plates at the bedside.l. H We used commercially available Du Pont Isolator 1.5 microbial tubes to eliminate the need to perform bedside inoculations. Besides making quantitative blood cultures more feasible in the clinical setting, the microbial tube is useful in the neonatal intensive care unit because it is designed for small volumes of blood (0.5 to 1.5 ml). It is

superior to broth cultures because results are often available earlier, t2,~3 Costs of the two systems are comparable. to Our contamination rate of 3.6% was less than a contamination rate of 8.7% found in a prior trial study of the Isolator 1.5 microbial tube, ~2in which most contaminated specimens were characterized by growth of only one colony on a single plate or growth occurring off the inoculum streak. Most contaminated cultures in that study became positive at 3 to 4 days incubation. The majority of cases of contamination in several studies using the Isolator tube have been caused by coagulase-negative staphylococci? z, 13 Blood cultures diagnosed as contaminated specimens in our current study confirmed these various observations. We believe that the combined criteria of microbial growth of one colony on a single plate or growth off the inoculum streak, growth of an organism known to be a skin contaminant, and a prolonged duration of incubation of 3 to 4 days facilitates the establishment of a diagnosis of contamination. In summary, paired quantitative blood cultures from a central catheter and a peripheral vessel may be useful in identifying catheter-related sepsis in neonates when the Isolator 1.5 microbial tu~e is used and a 1:10 dilution of the specimen is obtained before inoculation. Contaminated blood specimens may also be readily identified by this method. An additional benefit of paired blood cultures is the identification of catheter colonization in the absence of sepsis.

REFERENCES 1. Raucher HS, Hyatt AC, Barzi!ai A, et al. Quantitative blood cultures in the evaluations of septicemia in children with Broviac catheters. J PEDIATR1984;104:29-33. 2. Whimbey E, Wong B, Kiehn TE, et al. Clinical correlations of serial quantitative blood cultures determined by lysis-centri-

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3.

4.

5.

6.

7.

8.

fugation in patients with persistent septicemia. J Clin Microbiol 1984;19:766-71. Wing E J, Norden CW, Shadduck RK, et al. Use of quantitative bacteriologic techniques to diagnose catheter-related sepsis. Arch Intern Med 1979;139:482-3. Prince A, Heller B, Levy J, et al. Management of fever in patients with central vein catheters. Pediatr Infect Dis 1986;5:20-4. Hiemenz J, Skelton J, Pizzo P. Perspective on the management of catheter-related infections in cancer patients. Pediatr infect Dis 1986;5:6- l 1. Pazin G J, Peterson KL, Griff FW, et al. Determination of site of infection in endocarditis. Ann Intern Med 1975;82:74650. Krauss AN, Albert RF, Kannan MM. Contamination of umbilical catheters in the newborn infant. J PEDIATR 1970;77:965-9. Anagnostakis D, Kamba A, Petrocbilou V. Risk of infection associated with umbilical vein catheterization. J PEDIATR 1975;86:759-65.

Clinical and laboratory observations

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9. Maki DG, Weise CE, Sarafin HW. A semiquantitative culture method for identifying intravenous catheter-related infection. N Engl J Med 1977;296:1305-9. 10. Cooper GL, Hopkins CC. Rapid diagnosis of intravascular catheter-associated infection by direct Gram staining of catheter segments. N Engl J Med 1985;312:1142-7. 11. Snydman DR, Murray SA, Kornfeld S J, et al. Total parenteral nutrition-related infections: prospective epidemiologic study using semiquantitative methods. Am J Med 1982; 73:695-9. 12. Carey RB. Clinical comparison of the Isolator 1.5 microbial tube and the BACTEC radiometric system for detection of bacteremia in children. J Clin Microbiol 1984;19:634-8. 13. Stutman HR, Welch DF. Comparison of lysis-direct plating and broth methods for pediatric blood cultures: clinical relevance and cost effectiveness. Pediatr Infect Dis 1985;4: 52-5.

Late-onset hypocalcemia, rickets, and hypoparathyroidism in an infant of a mother with hyperparathyroidism Aaron Hanukoglu, MD, Stuart C h a l e w , MD, a n d A, A v i n o a m Kowafski, MD From the Department of Pediatrics, University of Maryland School of Medicine, Baltimore

N e o n a t a l hypocalcemia resulting from m a t e r n a l hyperp a r a t h y r o i d i s m usually is detected clinically in the first 2 weeks of life. ~'2 The affected infants have suppressed parathyroid hormone secretion resulting from chronically elevated i n t r a u t e r i n e levels of Ca. W i t h short-term s u p portive therapy, the infant's parathyroid glands resume normal functioning. In rare instances, m a t e r n a l hyperparathyroidism with infantile parathyroid suppression has been associated with the onset of clinical hypocalcemia at several m o n t h s of age, particularly i n breast-fed infants?. 4 A more frequent cause of late-onset ( > 2 months) hypocalcemia in infants is nutritional vitamin D deficiency, which is associated with secondary elevation of the infant's P T H ? W e present a case of late-onset infantile hypocalcemia resulting from a combination of vitamin D deficiency a n d hypoparathyroidism due to m a t e r n a l hyperparathyroidism. Submitted for publication Oct. 9, 1987; accepted Nov. 16, 1987. Reprint requests: Aaron Hanukoglu, MD, Division of Pediatric Endocrinology, University of Maryland School of Medicine, Baltimore, MD 21201.

CASE REPORT A 5-month-old black male infant was transferred to the University of Maryland because of episodes of generalized seizure activity lasting several minutes on the day of admission. The infant was the 3500 g product of a normal pregnancy and vaginal delivery. He had been exclusively breast-fed without vitamin PTH TRP cAMP

Parathyroid hormone Tubular reabsorption of phosphate Cyclic adenosine monophosphate

I

f

supplementation until 4 months of age, when cereals and fruits were started. The patient's past medical history included a seizurelike episode lasting a few seconds at 4 months of age, and persistent hoarseness for 6 weeks before admission. The physical examination revealed a well developed, alert but somewhat irritable infant with mild inspiratory stridor. The temperature was 38.1 ~ C, heart rate 116 beats/min, respiratory rate 32/min, blood pressuie 110/60 mm Hg, length 64 cm (25th percentile), and weight 6.1 kg (1Dth percentile). The pertinent findings were craniotabes over the posterior parietal bones, prominent ~costochondral junctions, and mild widening of the wrists. The remainder of the findings were unremarkable.