Changes in the Incidence of Necrotizing Enterocolitis Associated With Variation of the Gastrointestinal Microf lora in Neonates
Martin J. Bell, MD,* St. Louis, Missouri Ralph D. Feigin MD,+ St. Louis, Missouri Jessie L. Ternberg, MD,* St. Louis, Missouri
A remarkable variation in the incidence of necrotizing enterocolitis in infants hospitalized in the neonatal intensive care unit (NICU) at St. Louis Children’s Hospital was noted during a recent period of observation. The gastrointestinal microflora acquired by the infants in this unit showed a coincident variation in the retrieval rate for certain enteric microorganisms. These observations suggest a possible epidemiologic association with the pathogenesis of necrotizing enterocolitis. The data generated from an investigation of these events as well as a review of other studies on the epidemiology of necrotizing enterocolitis are reported herein. Material and Methods
Randomly selected neonates were studied to determine the bacterial microflora of the gastrointestinal tract. All subjects were hospitalized in the NICU of St. Louis Children’s Hospital for a variety of neonatal disorders. The bacteriologic data were collected during three time periods: period A-March, April, and May 1976;period B-March, April, and May 1977; and period C-June, July, and August 1977. Infants enrolled during each of the three periods did not differ significantly in birth weight, gestational age, condition warranting hospitalization, type of formula or feeding technique, delivery route, or previous treatment with antibiotics. No infant had evidence of necrotizing enterocolitis. Gastric samples were obtained by nasogastric lavage of the stomach with 3 to 5 ml of sterile, nonbacteriostatic water and aspiration of the gastric content. Fecal samples were obtained by rectal swab. All samples were transported immediately to the laboratory using both aerobic and anFrom the Departments of Surgery and Pediatrics, Divisions of Pediatric Surgery’ and Infectious Di1seases.t Washington University School of Medicine, and St. Louis Children’s Hospital, St. Louis, Missouri. Requests for reprints should be addressed to Martin J. Sell, MD, Division of Pediatric Surgery, St. Louis Children’s Hospital, 500 South Kingshighway, St. Louis, Missouri 63110.
Volume 138, November 1979
aerobic transport systems. All bacterial species isolated from each infant were subjected to identification procedures. During periods A, B, and C, 22 infants were treated for necrotizing enterocolitis. Infants included in the study were hospitalized in the NICU for at least 48 hours before the onset of enterocolitis. Ten infants with signs and symptoms of necrotizing enterocolitis at the time of admission were excluded from the analysis. The criteria for diagnosis of necrotizing enterocolitis were abdominal distension, emesis, hematochezia, and appropriate radiographic abnormalities. Results
Figure 1 shows the incidence of necrotizing enterocolitis in our nursery during the 6 year period 1972 through 1977. The lower graph represents all patients treated for necrotizing enterocolitis, including those who had evidence of it at the time of admission. The upper graph represents only those patients in whom necrotizing enterocolitis developed after they had been in the NICU for at least 48 hours. There appears to be a periodic clustering of cases with intervening quiescent periods during which only sporadic cases occurred. During period A, 32 infants were cultured, representing 30 per cent of the 107 infants admitted. Five cases of necrotizing enterocolitis occurred during period A, an incidence of 4.7 per cent. During period B, 46 infants were cultured, representing 40 per cent of the 115 admissions, and there were no cases of necrotizing enterocolitis. During period C, 23 infants were cultured, or 14 per cent of the 156 admissions, and there were 7 cases of enterocolitis, for an incidence of 4.4 per cent. A decrease in the frequency of retrieval of both gastric and fecal Enterobacteriaceae occurred during
629
Bell et
al
32I n
hTll”
m
6 7
6
n
n
1972
1973
1974
341.
373
455
NEC
STAGEII
@?,,I
NEC
STAGEIIORIX
IN
NICU
ADMITTED
1955 534
48 HRS
WITH
OR
572
LONGER
DISEASE
Ill *
ANNUAL
ADM
1976
N=67
N ~43
period B, when the incidence of necrotizing enterocolitis decreased to zero. An increased frequency of colonization of infants in the neonatal intensive care unit with Enterobacteriaceae coincided with the return of necrotizing enterocolitis in period C. A significant decrease in the retrieval rate of gastric (p
Martin J. Bell, MD,* St. Louis, Missouri Ralph D. Feigin MD,+ St. Louis, Missouri Jessie L. Ternberg, MD,* St. Louis, Missouri
A remarkable variation in the incidence of necrotizing enterocolitis in infants hospitalized in the neonatal intensive care unit (NICU) at St. Louis Children’s Hospital was noted during a recent period of observation. The gastrointestinal microflora acquired by the infants in this unit showed a coincident variation in the retrieval rate for certain enteric microorganisms. These observations suggest a possible epidemiologic association with the pathogenesis of necrotizing enterocolitis. The data generated from an investigation of these events as well as a review of other studies on the epidemiology of necrotizing enterocolitis are reported herein. Material and Methods
Randomly selected neonates were studied to determine the bacterial microflora of the gastrointestinal tract. All subjects were hospitalized in the NICU of St. Louis Children’s Hospital for a variety of neonatal disorders. The bacteriologic data were collected during three time periods: period A-March, April, and May 1976;period B-March, April, and May 1977; and period C-June, July, and August 1977. Infants enrolled during each of the three periods did not differ significantly in birth weight, gestational age, condition warranting hospitalization, type of formula or feeding technique, delivery route, or previous treatment with antibiotics. No infant had evidence of necrotizing enterocolitis. Gastric samples were obtained by nasogastric lavage of the stomach with 3 to 5 ml of sterile, nonbacteriostatic water and aspiration of the gastric content. Fecal samples were obtained by rectal swab. All samples were transported immediately to the laboratory using both aerobic and anFrom the Departments of Surgery and Pediatrics, Divisions of Pediatric Surgery’ and Infectious Di1seases.t Washington University School of Medicine, and St. Louis Children’s Hospital, St. Louis, Missouri. Requests for reprints should be addressed to Martin J. Sell, MD, Division of Pediatric Surgery, St. Louis Children’s Hospital, 500 South Kingshighway, St. Louis, Missouri 63110.
Volume 138, November 1979
aerobic transport systems. All bacterial species isolated from each infant were subjected to identification procedures. During periods A, B, and C, 22 infants were treated for necrotizing enterocolitis. Infants included in the study were hospitalized in the NICU for at least 48 hours before the onset of enterocolitis. Ten infants with signs and symptoms of necrotizing enterocolitis at the time of admission were excluded from the analysis. The criteria for diagnosis of necrotizing enterocolitis were abdominal distension, emesis, hematochezia, and appropriate radiographic abnormalities. Results
Figure 1 shows the incidence of necrotizing enterocolitis in our nursery during the 6 year period 1972 through 1977. The lower graph represents all patients treated for necrotizing enterocolitis, including those who had evidence of it at the time of admission. The upper graph represents only those patients in whom necrotizing enterocolitis developed after they had been in the NICU for at least 48 hours. There appears to be a periodic clustering of cases with intervening quiescent periods during which only sporadic cases occurred. During period A, 32 infants were cultured, representing 30 per cent of the 107 infants admitted. Five cases of necrotizing enterocolitis occurred during period A, an incidence of 4.7 per cent. During period B, 46 infants were cultured, representing 40 per cent of the 115 admissions, and there were no cases of necrotizing enterocolitis. During period C, 23 infants were cultured, or 14 per cent of the 156 admissions, and there were 7 cases of enterocolitis, for an incidence of 4.4 per cent. A decrease in the frequency of retrieval of both gastric and fecal Enterobacteriaceae occurred during
629
Bell et
al
32I n
hTll”
m
6 7
6
n
n
1972
1973
1974
341.
373
455
NEC
STAGEII
@?,,I
NEC
STAGEIIORIX
IN
NICU
ADMITTED
1955 534
48 HRS
WITH
OR
572
LONGER
DISEASE
Ill *
ANNUAL
ADM
1976
N=67
N ~43
period B, when the incidence of necrotizing enterocolitis decreased to zero. An increased frequency of colonization of infants in the neonatal intensive care unit with Enterobacteriaceae coincided with the return of necrotizing enterocolitis in period C. A significant decrease in the retrieval rate of gastric (p
