Determinant of bacterial translocation in the newborn: small bowel versus large bowel colonization

Preceding Clinical Events in High-risk, Postoperative, Pediatric Cardiac Patients- A Novel Association With Bacteremia

Objective: Blood stream infections (BSIs) are well described in pediatric cardiac intensive care units (PCICU). We noted that postoperative high-risk patients may develop BSI after a preceding clinical event (PCE). The study aim was to investigate whether high-risk patients who developed bacteremia experienced more PCEs than a similar group of high-risk patients. Design: Retrospective case-control study. Setting: Referral pediatric center. Patients: We enrolled patients who developed bacteremia from March 2010 to November 2019, after undergoing open-heart surgery at a pediatric center. The control group was comprised of case-matched patients with immediate consecutive same surgery. Interventions: None. Measurements: We recorded operative data, common risk factors, postoperative indicators of organ dysfunction, mortality, and PCEs 72 to 24 h before bacteremia emerged. Main results: A total of 200 patients were included (100 with bacteremia and 100 controls). Key demographic and operative parameters were matched. Bacteremia emerged on average on postoperative day 12.8. Skin-associated Gram-positive bacteria were cultured in 10% and Gram-negative bacteria in 84% of the patients. Average central-venous lines (CVL) duration was 9.5 ± 8.4 days. Postoperatively (72 h), indicators of organ dysfunction were significantly worse in patients with bacteremia, with a higher rate of postoperative complications during PCICU length-of-stay (LOS). In the bacteremia group, 72 to 24 h prior to the development of bacteremia, 92 (92%) PCEs were recorded, as compared to 21 (21%) in controls during their entire LOS (odds ratio [OR] 43.3, confidence interval [CI] 18.2-103.1, P < .0001). Conclusions: We propose a 3-hit model demonstrating that high-risk patients undergoing open-heart surgery have significantly higher risk for bacteremia after a PCE.

Challenges in rabbit doe feeding, including the young doe

In this review is summarized the last knowledge on rabbit doe nutrition, to complement the current nutritional requirements and strategies for the young and adult rabbit does, considering the production, health, and welfare issues. The rabbit doe must reach an adequate maturity level (body condition) at first artificial insemination (AI) to face its productive life with minimal guarantees (around 7.0 mm of perirenal fat thickness, 2.8 ng/mL of plasma leptin concentration and around 18% and 15-20% of body protein and fat, respectively). This goal can be achieved by restricting feed intake from 12 weeks of age until first AI or feeding ad libitum with a fibrous diet (<10.5 MJ digestible energy/kg) from 60 d of age to first parturition. Once the doe is reproducing, the increase of the n-3 fatty acids (or reduction of the n-6/n-3 ratio), soluble fibre (under epizootic enteropathy) and the Arg/Lys and Gln/Lys ratios may help to improve the reproductive traits of rabbit does, although their optimal level of inclusion remain to be identified. It is recommended to limit an excessive negative energy balance before parturition, and the supplementation of glucose precursors to reduce the ketosis incidence could be useful. The formulation of different diets for the doe and the litter to fit better their requirements and assuring their health would be an option to consider when it would be applicable in the farm. The influence of the mother on the litter microbiota and immune status and its potential modulation through the diet open a new research area that will deserve more studies in the next future.

Shifting focus toward healthcare-associated bloodstream infections: The need for neonatal intensive care unit-specific NHSN definitions

OBJECTIVE

Healthcare-associated bloodstream infections (HABSIs) are a significant cause of mortality and morbidity in the neonatal intensive care unit (NICU) population. Our objectives were to review the epidemiology of HABSIs in our NICU and to examine the applicability of National Healthcare Safety Network (NHSN) definitions to the NICU population.

METHODS

We performed a retrospective review of all neonates admitted to the 54-bed, level IV NICU at Yale-New Haven Children's Hospital with a HABSI between January 1, 2013, and December 31, 2018. Clinical definitions per NICU team and NHSN site-specific definitions used for source identification were compared using the McNemar χ2 test.

RESULTS

We identified 86 HABSIs with an incidence rate of 0.80 per 1,000 patient days. Only 13% of these were CLABSIs. Both CLABSIs and non-catheter-related bloodstream infections occurred primarily in preterm neonates, but the latter were associated with a significantly higher incidence of comorbidities and the need for respiratory support. The NHSN definitions were less likely to identify a source compared to the clinical definitions agreed upon by our NICU treating team (P < .001). Furthermore, 50% of patients without an identified source of infection by NHSN definitions were bacteremic with a mucosal barrier injury organism, likely from gut translocation.

CONCLUSIONS

HABSIs occur primarily in premature infants with comorbidities, and CLABSIs account for a small proportion of these infections. With the increasing focus on HABSI prevention, there is a need for better NHSN site-specific definitions for the NICU population to prevent misclassification and direct prevention efforts.

Effect of pre- and post-weaning dietary supplementation with arginine and glutamine on rabbit performance and intestinal health

BACKGROUND

The purpose of the present study was to assess if the exposure to glutamine (Gln), arginine (Arg) or their combination from pregnancy, through the maternal diet, to a post weaning supplemented diet, can stimulate litter performance, gut development and immune function. To this end does and their litters were fed the same basal diet no supplemented (control C), or supplemented with 0.4% Gln, 0.4% Arg, or 0.4 Gln + 0.4 Arg. Rabbits were weaned at 25 d of age and fed the same experimental diet as their mothers for 10 additional days (35 d of age). Bacterial translocation to mesenteric lymph nodes (MLN) at 6 d of age and intestinal histology, enzymatic activity, phenotypical and functional analysis of intraepithelial lymphocytes (IEL) from the appendix were determined at 6, 25 and 35 d of age.

RESULTS

No significant differences on animal performance or mortality rates were observed among dietary treatments. However, kits from rabbit does supplemented with Gln tended (P ≤ 0.10) to reduce the translocation of total number of both aerobic and facultative anaerobic bacteria to the MLN. Also, rabbits fed the Gln supplemented diets maintained intestinal villous height at weaning compared to the non-supplemented diets (P < 0.05). The proportions of CD45+CD4+ and CD45+CD8+ IEL in the appendix were not affected by dietary means. However, in rabbits IEL at weaning dietary Gln significantly upregulated IL-2 and downregulated IL-6 expression.

CONCLUSIONS

Despite a lack of effect on performance and mortality the inclusion of 0.4% Gln has a positive effect by maintaining intestinal villous height and modulating the cytokine profile at weaning. The supplementation with Arg or Arg + Gln at the selected doses in this study did not exert positive effects on rabbit intestinal health.

Nutritional modulation of the gut microbiota and immune system in preterm neonates susceptible to necrotizing enterocolitis

The gastrointestinal inflammatory disorder, necrotizing enterocolitis (NEC), is among the most serious diseases for preterm neonates. Nutritional, microbiological and immunological dysfunctions all play a role in disease progression but the relationship among these determinants is not understood. The preterm gut is very sensitive to enteral feeding which may either promote gut adaptation and health, or induce gut dysfunction, bacterial overgrowth and inflammation. Uncontrolled inflammatory reactions may be initiated by maldigestion and impaired mucosal protection, leading to bacterial overgrowth and excessive nutrient fermentation. Tumor necrosis factor alpha, toll-like receptors and heat-shock proteins are identified among the immunological components of the early mucosal dysfunction. It remains difficult, however, to distinguish the early initiators of NEC from the later consequences of the disease pathology. To elucidate the mechanisms and identify clinical interventions, animal models showing spontaneous NEC development after preterm birth coupled with different forms of feeding may help. In this review, we summarize the literature and some recent results from studies on preterm pigs on the nutritional, microbial and immunological interactions during the early feeding-induced mucosal dysfunction and later NEC development. We show that introduction of suboptimal enteral formula diets, coupled with parenteral nutrition, predispose to disease, while advancing amounts of mother's milk from birth (particularly colostrum) protects against disease. Hence, the transition from parenteral to enteral nutrition shortly after birth plays a pivotal role to secure gut growth, digestive maturation and an appropriate response to bacterial colonization in the sensitive gut of preterm neonates.

Breast- v. formula-feeding: impacts on the digestive tract and immediate and long-term health effects

The health benefits of breast-feeding have been recognised for a long time. In particular, breast-feeding is associated with lower incidence of necrotising enterocolitis and diarrhoea during the early period of life and with lower incidence of inflammatory bowel diseases, type 2 diabetes and obesity later in life. The higher nutritional and protective degree of human milk is related to its nutritional composition that changes over the lactation period and to the biological activities of specific components while lower growth rate of breast-fed infants may be attributed to their self-regulation of milk intake at a lower level than formula-fed infants. Many results now suggest that the developmental changes in intestinal and pancreatic function that occur postnatally are modulated by the diet. Indeed, formula-feeding induces intestinal hypertrophy and accelerates maturation of hydrolysis capacities; it increases intestinal permeability and bacterial translocation, but does not induce evident differences in microbiota composition. Whether these changes would be beneficial for enhancing absorptive capacities and for educating the gut-associated immune system remains to be further studied. Moreover, it is evident that formula-feeding increases basal blood glucose and decreases plasma ketone body concentrations, while discrepancies on postprandial glycaemia, insulin and incretin responses in both human studies and experimental studies are inconclusive. Manipulating the composition of formula, by reducing protein content, adding prebiotics, growth factors or secretory IgA can modulate intestinal and pancreatic function development, and thereby may reduce the differential responses between breast-fed and formula-fed neonates. However, the developmental responses of the digestive tract to different feeding strategies must be elucidated in terms of sensitivity to developing diseases, taking into account the major role of the intestinal microbiota.

Diet-dependent mucosal colonization and interleukin-1beta responses in preterm pigs susceptible to necrotizing enterocolitis

OBJECTIVES

Intestinal colonization challenges the neonatal innate immune system, especially in newborns with an immature immune response lacking the supportive bioactive components from mother's milk. Accordingly, formula-fed preterm pigs frequently show bacterial overgrowth, mucosal atrophy, and gut lesions reflecting necrotizing enterocolitis (NEC) within the first days after birth. We hypothesized that NEC development is related to a diet-dependent bacterial adherence and a subsequent proinflammatory cytokine response in the gut mucosa immediately after introduction of enteral food.

MATERIALS AND METHODS

Premature piglets (92% gestation) received 2 to 3 days of total parenteral nutrition followed by 0, 8, or 17 hours of enteral formula or sow's colostrum feeding.

RESULTS

Following 8 hours, but not 17 hours, of colostrum feeding, a reduced number of intestinal samples with adherent bacteria (both Gram-negative and Gram-positive bacteria) was counted compared with 0 or 8 hours of formula feeding. Besides a more dense colonization, formula feeding leads to higher intestinal interleukin-1beta (IL-1beta) levels and more NEC-like lesions from 8 hours onward. The load of adherent bacteria was especially high in NEC lesions. Toll-like receptor 4 was detected in enteroendocrine, neuronal, and smooth muscle cells, potentially mediating the increase in IL-1beta levels by Gram-negative bacteria.

CONCLUSIONS

Formula feeding facilitates bacterial adherence and the development of a proinflammatory state of the intestine, which may be among the key factors that predispose formula-fed preterm neonates to NEC.

Supplementation with galactooligosaccharides and inulin increases bacterial translocation in artificially reared newborn rats

Supplementation of formulas with prebiotics enhances the growth of lactate producing bacteria, and fecal lactate, and acetate levels in infants. High concentrations of organic acids in intestinal lumen have, however, been shown to impair the intestinal barrier function. To determine whether stimulating the colonic microbiotal metabolism with prebiotics would impair the neonatal intestinal barrier function, artificially reared rats were fed milk formula with or without a mixture of galactooligosaccharides/inulin (GOS/Inulin, 88/12; 5.6 g/L) from the 7th d of life (d7) until weaning (d20). At d18, GOS/inulin supplementation had increased the concentrations of acetate and lactate in colonic lumen. Although neither ileum-associated microbiota nor colonic permeability (assessed in Ussing chambers), nor the expression of tight junction claudin-2 and claudin-3 mRNA were altered, GOS/inulin supplementation was associated with increased bacterial translocation (BT) toward spleen. None of these effects persisted at d40. We conclude that GOS/inulin supplementation may increase BT in an immature gut. The balance between the potential infectious risk of BT vs. its putative beneficial effect on the maturation of neonatal immune system clearly warrants further study.

Bacterial translocation in the normal human appendix parallels the development of the local immune system

Experimental modes and pathological conditions may result in bacterial translocation (BT), that is, the passage of indigenous bacteria colonizing the intestine through the intestinal mucosa to mesenteric lymph nodes. Yet no data are available on BT in the normal human gut. We determined the occurrence of BT and its extent in histologically normal, incidentally removed human vermiform appendices (VA) from individuals of different ages and correlated the findings with the development with age of associated lymphatic tissue. BT appears to pertain to normal antigen-sampling processes of the GALT in the VA. It also parallels the development of the GALT and its maintenance during adulthood. In the first two weeks after birth, when bacterial colonization of the gut evolves and when the VA lacks the protection of secretory IgA, BT was not detected. Thereafter, BT occurs along with development of the local GALT, which is fully built up after the first year. A physiological uptake of, or invasion by, bacteria may be instrumental (1) for tolerance induction against the indigenous flora and (2) for the stimulation and normal development of the GALT.

Total parenteral nutrition adversely affects gut barrier function in neonatal piglets

Sepsis is the most common morbidity in preterm infants, who often receive total parenteral nutrition (TPN). We hypothesized that gut barrier function is compromised in TPN-fed compared with enterally fed newborn piglets (ENT pigs). Colostrum-deprived newborn pigs were implanted with jugular venous and bladder catheters under general anesthesia. Pigs were either administered TPN (n = 15) or fed formula (ENT pigs, n = 15). After 6 days, pigs were gavaged a solution of mannitol, lactulose, and polyethylene glycol 4000 (PEG 4000) and urine was collected for 24 h. At 7 days, small bowel samples were assayed for myeloperoxidase activity, morphometry, and tight junction protein abundance. Intestinal contents and peripheral organ sites were cultured for bacteria. Urinary recovery (%dose) of mannitol (53 vs. 68) was lower, whereas that of lactulose (2.93 vs. 0.18) and PEG 4000 (12.78 vs. 0.96) were higher in TPN vs. ENT pigs, respectively (P < 0.05). Incidence of translocation was similar in TPN and ENT pigs. Myeloperoxidase activity was increased in TPN vs. ENT pigs in the jejunum (P < 0.001) and was weakly correlated with lactulose (R2 = 0.32) and PEG 4000 (R2 = 0.38) recovery. Goblet cell counts did not change, but intraepithelial lymphocyte numbers decreased with TPN. Only claudin-1 protein abundance was increased in the TPN group. We conclude that TPN is associated with impairment of neonatal gut barrier function as measured by permeability but not translocation.

The role of early enteral nutrition in protecting premature infants from sepsis

Care of critically ill, preterm infants is a major challenge. Because of their small size and complex health problems, preterm infants require long-term hospitalization in the intensive care unit where they are exposed to serious microorganisms and other antigens that can overwhelm their immature immune systems. As smaller and more fragile preterm infants are surviving NICU care, these infants are at increased risk for nosocomial infections. Although modern antimicrobial agents are invaluable in the management of infection, they can result in biologic stress to the immature physiology of the preterm infant. Nonpharmacologic strategies to enhance the immunocompetence of the preterm immune systems provide another alternative in the management of these infants. Because the gastrointestinal tract is one of the largest immune organs within the body, strategies to maximize its immune functions can improve the outcome of these infants and help prevent or minimize the risk of infection. One such strategy is the early introduction of enteral feedings designed to stimulate or prime the gut. Early introduction of enteral feedings in the acutely ill preterm infant appears to be well tolerated in a variety of small clinical studies. Although the studies vary considerably in design and variables measured, collectively they show a solid trend toward improved outcomes. By preventing the negative consequences of a prolonged period of NPO, early enteral feedings promote the normal processes of the gut as a physical, mechanical, physiologic, and immunologic barrier. A solid understanding of the pathophysiology of prolonged NPO status and the physiology of the gut's immune properties enables critical care nurses to improve care of these vulnerable NICU patients.

Confirmation of translocated gastrointestinal bacteria in a neonatal model

PURPOSE

The hypothesis that enteric bacteria translocate from the gastrointestinal (GI) tract to extraintestinal sites has been extensively studied. However, definitive evidence that spontaneous bacterial translocation and dissemination from the GI tract to extraintestinal sites occur in a neonatal model has been lacking. The aim of this study was to confirm this phenomenon by tracking enterally administered, plasmid-labeled bacteria to extraintestinal sites.

MATERIALS AND METHODS

Escherichia coli 07:K1 (E. coli K1) with and without a nontransferable, ampicillin resistance plasmid (pGEM-7) were used in this study. Newborn New Zealand white rabbit pups were separated into three treatment groups: transformed E. coli K1 (E. coli K1 + pGEM-7, n = 20), nontransformed E. coli K1 (n = 12), and control pups (no bacteria, n = 7). Pups were enterally fed 10% Formulac solution supplemented with a suspension of bacteria respective to their group. After the pups fed twice daily for 2 days, representative tissue specimens from the small bowel (SB), mesenteric lymph nodes (MLNs), spleen (SPL), and liver (LIV) were aseptically harvested and tested for culture growth in ampicillin-supplemented medium.

RESULTS

Positive growths of plasmid-induced ampicillin-resistant bacteria were detected in tissue specimens harvested from rabbits fed transformed E. coli K1, but were not detected in the other groups.

CONCLUSION

This experiment demonstrated conclusively that transformed E. coli K1 fed to healthy rabbit pups spontaneously translocated from the intestinal lumen and subsequently disseminated to the mesenteric lymph nodes, spleen, and liver.

Does probiotics administration decrease serum endotoxin levels in infants?

PURPOSE

The aim of this study was to examine whether administration of probiotics to infants can change the ratio of intestinal flora and thereby decrease serum endotoxin produced by potentially pathogenic microorganisms.

METHODS

Nine infants including five with of biliary atresia, two with omphalocele, one each with Hirschsprung's disease and imperforate anus were studied. All patients were stable, and no antibiotics were given during this study. A probiotic mixture consisting of Streptococcus faecalis, Clostridium butyricum and Bacillus mesentericus was administered orally to each infant at 2 g/day for 2 weeks. Fecal aerobic and anaerobic bacterial cultures, serum endotoxin level, and other biochemical parameters were examined.

RESULTS

In fecal cultures, anaerobic bacteria including Bifidobacterium increased significantly whereas Escherichia coli, Streptococcus, and Klebsiella tended to decrease. The ratio of anaerobic to aerobic bacteria increased five times as a result of administration of probiotics, and serum endotoxin levels decreased.

CONCLUSIONS

Probiotics affect intestinal bacterial flora by increasing anaerobic bacteria and decreasing the population of potentially pathogenic microorganisms. A decrease in luminal endotoxin may result in less endotoxin translocation or bacterial translocation.

Intestinal permeability to small- and large-molecular-weight substances in the newborn rabbit

BACKGROUND/PURPOSE

The authors have previously reported the occurrence of spontaneous bacterial translocation (BT) and its resolution with age in the newborn rabbit. They have also reported a close correlation between small bowel bacterial colonization (BC-SB) and BT at 1 week of age, suggesting that the presence of luminal bacteria and their production of endotoxins may increase the intestinal permeability. The aim of this study was to evaluate intestinal permeability to small and large molecules in the newborn rabbit and to correlate it with BT.

MATERIALS AND METHODS

New Zealand White rabbits (n = 96) 1, 7, 14, 21, and over 120 days (adult) of age were given either C14-labeled ethylene diamine tetraacetic acid (EDTA) (MW 290) or C14-Dextran (MW 70,000) via an orogastric tube at 1 mCi per 100 g of body weight. Five hours later, blood, urine, liver, and intestine were collected, and scintillation counting was performed after solubilization. In a separate series of rabbits (n = 136), the incidence of BT, BC-SB, and small intestinal surface area (SA) were measured.

RESULTS

Total permeability to Dextran decreased with age and was significantly reduced at 14 days of age. In contrast, total permeability to EDTA increased and was maximal in 7- to 14-day-old rabbits and began to decrease at 21 days of age. The incidence of BC-SB rapidly increased at 7 days of age and reached 100% at 14 days of age. The incidence of BT peaked at 7 days of life (30%) and then decreased with age. SA increased rapidly in the first 3 weeks and SA growth rate of 21-day-old rabbits was almost 1,400% compared with 1-day-old rabbits.

CONCLUSIONS

This study has shown an age-related reduction of intestinal permeability to large (Dextran) and small (EDTA) molecular weight particles. However, intestinal permeability to EDTA had a different pattern than Dextran, suggesting that there may be different mechanisms of intestinal permeability to different size molecules. Intestinal permeability to EDTA closely correlated with bacterial colonization and bacterial translocation, suggesting that changes in the intestinal bacterial environment may affect the intestinal permeability, possibly by activating the immune system secondary to increases in endotoxins and bacteria.

Longitudinal intestinal lengthening and tailoring: results in 20 children

Longitudinal intestinal lengthening and tailoring (LILT) is increasingly favoured as a treatment for short-bowel syndrome. In a personal series, 20 children underwent LILT between 1962 and 1997. There was negligible morbidity (hemiloop anastomotic stenosis in 2) and no operative mortality. At a mean follow-up of 6.4 years overall survival was 45%, and certain features were clearly related to outcome. Survivors had > 40 cm of residual small bowel (commonly jejunum) and had little hepatic dysfunction despite parenteral nutrition of similar time and nature as non-survivors. Children who did not survive had < 40 cm of residual small bowel and developed early lethal hepatic dysfunction of unclear aetiology. Outcome did not seem to be influenced by the presence of the ileocaecal valve or the length of residual colon. Children born with short-bowel should be offered LILT at an early stage when still in good physical condition, so as to avoid liver-damaging intraluminal stasis and bacterial translocation and to enhance intestinal adaptation and hepatoprotective factors.

Adverse metabolic and microbiological effects of tube feeding in experimental canine obstructive jaundice

BACKGROUND

Inadequate oral intake and poor absorption result in malnutrition in obstructive jaundice. Both malnutrition and obstructive jaundice promote bacterial translocation from the gut. This study was designed to test the efficacy of tube feeding in preventing malnutrition and in decreasing the metabolic and microbiological adverse effects in obstructive jaundice.

METHODS

Forty adult mongrel dogs were studied and were allocated into one of four groups: group I (PO-control) underwent sham ligation of the common bile duct (CBDL) and was fed ad libitum on Portagen (Mead Johnson, Evansville, IN); group II (PO-CBDL) underwent CBDL and was ad libitum fed on the same formula; group III (FEG-control) underwent sham CBDL and received forced esophagogastric feeding (FEG) with Portagen; and group IV (FEG-CBDL) underwent CBDL and received FEG. All the animals underwent insertion of a F-12 feeding tube to the stomach from an esophagotomy wound on day 1 and the tube was used for continuous enteral feeding with Portagen over 4 h/d from day 2 until day 13 in groups III and IV. Fourteen days later, blood samplings were done and a laparotomy was performed to obtain liver, mesenteric lymph nodes (MLN), and terminal ileum for quantitative bacterial culture. Bacterial translocation to MLN and liver was represented by log10 CFU/g of tissue in this study.

RESULTS

Both group II and IV animals with CBDL significantly lost body weight (p = .0001) and had a lower level of prealbumin (p = .0054). A significant increase in bacterial translocation to MLN and to liver occurred in groups II and IV (p = .0017 and .0268, respectively). Intestinal bacterial population was also higher in these two groups than in the other two controls (p = 0.0028). An increase in plasma ammonia level was found in dogs with CBDL (p = .0002) and in dogs with FEG (p = .003), compared with their respective controls. Three among 13 dogs in group IV died and no mortality occurred in the other groups (p = .223).

CONCLUSIONS

Tube feeding fails to improve malnutrition in obstructive jaundice and is associated with intestinal bacterial overgrowth, promoting bacterial translocation to MLN and liver, precipitating liver dysfunction and consequently a higher mortality.

The association of gut-associated lymphoid tissue and bacterial translocation in the newborn rabbit

The authors have previously demonstrated spontaneous bacterial translocation (BT) in newborn rabbits and its resolution with aging. It is hypothesized that this spontaneous BT was associated with an immature gut-associated lymphoid tissue (GALT). The aim of the present study was to characterize the cellular populations of the GALT in rabbits at various ages and to correlate this with the frequency of BT. Small bowel (SB) sections and mesenteric lymph nodes (MLN) were harvested and cultured (aerobically) from New Zealand White rabbits at 0, 6, 14, 28, and more than 90 days of age for determination of bacterial colonization (BC) and BT. Portions of ileum (n = 6 for each age) were simultaneously harvested for immunoperoxidase staining. Total T cells (CDS+), expressed as the number of positive cells/1000 nuclei and activated T cells (CD25+), expressed as the number of positive cells/1000 nuclei and as the ratio of CD25+/CD5+ cells, were analyzed for each tissue. Positive cells were counted in 30 villi by light microscopy. The incidence of BT rose as BC increased in the small bowel and peaked at 6 days of age; BT then decreased with age. CD5+ cells in the small bowel villi at 0 days of age were few (2.5 positive cells/1000 nuclei) and the number significantly increased with age (6 days, 6.5; 14 days, 19.0; 28 days, 31.6; adult, 136.6 positive cells/1,000 nuclei). The distribution of T cells started in the crypts, and with advancing age, cells were found all the way to the top of the villi. The number of CD25+ cells in the villi increased with age. The CD25+/CD5+ ratio in the small bowel villi peaked at 6 days of age. These results demonstrate an inverse relationship between the number of CD5+ cells in the intestinal villi and the incidence of bacterial translocation. The elevation of activated T cells (CD25+) at 6 days of age may be the result of an immunologic activation during the time of peak bacterial translocation. These data suggest that maturity of the GALT leads to a loss of spontaneous bacterial translocation in the newborn period. Modalities that supplement the GALT may help reduce bacterial translocation.

Acute hypoxia does not increase bacterial translocation in newborn rabbits

PURPOSE

We have previously demonstrated that spontaneous bacterial translocation (BT) occurs in newborn rabbits and correlates strongly with small bowel colonization (BC). Birth stress, specifically hypoxia, is believed to increase this pathologic process and thus lead to sepsis. This study investigated the relationship between BT and acute hypoxia in newborn rabbits.

METHODS

Four hundred seventeen rabbit pups (aged 0, 2 to 4, 6, and 28 days) were divided into four groups according to the type of hypoxic stress: 9% O(2) for 1 hour, 9% O(2) + 12% CO(2) for 1 or 4 hours, and 21% O(2) (control animals). The animals were killed 1.5 or 20 hours after the stress. Sterile specimens of mesenteric lymph nodes (MIN), spleen, liver, small bowel, and large bowel were incubated aerobically at 37 degrees C for 24 hours in thioglycolate broth, and subsequently plated on both MacConkey and Colistin Naladixic Acid media. After 24 hours, the growth on both plates was recorded. X(2) analysis was used, and P values of less than .05 were considered significant.

RESULTS

BC of the small bowel and BT to the MLN were low in the first 4 days of life in the hypoxic groups (range, 0% to 21% BC, 0% to 6% BT) and the control group (range, 4% to 30% BC, 3% to 12% BT). After an increase in BC at 6 days of age, the rate of BT increased to 25% to 29% in control animals. The rate of BT in the hypoxic groups (25%) did not differ significantly from that of the controls (P > .05). Additionally, killing at 20 hours (v 1.5 hours) was not associated with an increase in the incidence of BT. None of the stress groups had a significant increase in BT compared with the controls. Importantly, although 4 hours of 9% O(2) + 12% CO(2) resulted in a 30% mortality rate, the incidence of BT was no higher than that of the control animals (13% v 29%; P > .05).

CONCLUSION

Severe hypoxic stress in newborn rabbits does not increase the incidence of BT. Because the incidence of BT correlates with that of BC, and because BC is the same in the control and hypoxic animals, the sepsis observed in hypoxic newborns probably is not related to an increased incidence of BT.