Reappraisal of C-reactive protein as a screening tool for neonatal sepsis

AIMS: To assess the usefulness of C-reactive protein (CRP) [either alone or in combination with a full blood examination (FBE) and microbiology of gastric aspirate] in predicting the diagnosis of neonatal sepsis compared with routinely available markers of infection. METHODS: A prospective study of quantitative CRP, FBE, gastric aspirate and surface swab microscopy and culture in predicting neonatal sepsis in a level III perinatal referral hospital was performed. RESULTS: Of 301 episodes evaluated over a 5-month period, there was a 5% rate of major (culture proven) sepsis (3% early onset, <72 hours) and 10% rate of modified sepsis. No single test alone was sufficiently reliable as an indicator of infection to be a satisfactory screening tool for early onset sepsis [CRP sensitivity 67%, negative predictive value (NPV) 86%, FBE sensitivity 63%, NPV 80%, gastric aspirate sensitivity 57%, NPV 83%]. CONCLUSION: The three-test combination had a sensitivity of 97%, NPV 98% and likelihood ratio of 49, thus providing a useful diagnostic tool.     

Clinical microbiology of bacterial and fungal sepsis in very-low-birth-weight infants

Twenty percent of very-low-birth-weight (<1500 g) preterm infants experience a serious systemic infection, and despite advances in neonatal intensive care and antimicrobials, mortality is as much as threefold higher for these infants who develop sepsis than their counterparts without sepsis during their hospitalization. Outcomes may be improved by preventative strategies, earlier and accurate diagnosis, and adjunct therapies to combat infection and protect the vulnerable preterm infant during an infection. Earlier diagnosis on the basis of factors such as abnormal heart rate characteristics may offer the ability to initiate treatment prior to the onset of clinical symptoms. Molecular and adjunctive diagnostics may also aid in diagnosing invasive infection when clinical symptoms indicate infection but no organisms are isolated in culture. Due to the high morbidity and mortality, preventative and adjunctive therapies are needed. Prophylaxis has been effective in preventing early-onset group B streptococcal sepsis and late-onset Candida sepsis. Future research in prophylaxis using active and passive immunization strategies offers prevention without the risk of resistance to antimicrobials. Identification of the differences in neonatal intensive care units with low and high infection rates and implementation of infection control measures remain paramount in each neonatal intensive care unit caring for preterm infants.     

Breast milk causing neonatal sepsis and death

Breast milk can occasionally transmit serious viral and bacterial infections to preterm infants. We present three cases of late-onset neonatal sepsis, including one that resulted in death, occurring in preterm infants. The likely source of the microorganisms in all three cases was expressed breast milk.     

Inflammatory and immunological markers in preterm infants: correlation with disease

Newborn infants often suffer from bacterial and viral infections without presenting typical symptoms. Therefore, reliable methods for detecting and monitoring sepsis in the newborn would be beneficial. In older patients C-reactive protein (CRP) and neopterin have proved useful serum markers of infection and inflammation. Both of these markers are regulated by cytokines, and it has been proposed that cytokines themselves could be used to monitor immune activation and infection. This study has examined the levels of CRP, neopterin, soluble IL-2R, tumour necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) in cord blood samples from both pre-mature and term neonates. Having established reference ranges for these analytes, serial measurements were made in babies requiring intensive care support. The results suggest that in preterm infants the simultaneous measurement of CRP and neopterin, and possibly soluble IL-2R, may provide an accurate early diagnosis of sepsis and may be of use in differentiating between bacterial and viral etiologies. In addition, serial measurement of these markers may help in the early diagnosis of necrotizing enterocolitis (NEC).     

Comparison of 16S rRNA gene PCR and BACTEC 9240 for detection of neonatal bacteremia

Ten percent of infants born in the United States are admitted to neonatal intensive care units (NICU) annually. Approximately one-half of these admissions are from term infants (>34 weeks of gestation) at risk for systemic infection. Most of the term infants are not infected but rather have symptoms consistent with other medical conditions that mimic sepsis. The current standard of care for evaluating bacterial sepsis in the newborn is performing blood culturing and providing antibiotic therapy while awaiting the 48-h preliminary result of culture. Implementing a more rapid means of ruling out sepsis in term newborns could result in shorter NICU stays and less antibiotic usage. The purpose of this feasibility study was to compare the utility of PCR to that of conventional culture. To this end, a total of 548 paired blood samples collected from infants admitted to the NICU for suspected sepsis were analyzed for bacterial growth using the BACTEC 9240 instrument and for the bacterial 16S rRNA gene using a PCR assay which included a 5-h preamplification culturing step. The positivity rates by culture and PCR were 25 (4.6%) and 27 (4.9%) positive specimens out of a total of 548 specimens, respectively. The comparison revealed sensitivity, specificity, and positive and negative predictive values of 96.0, 99. 4, 88.9, and 99.8%, respectively, for PCR. In summary, this PCR-based approach, requiring as little as 9 h of turnaround time and blood volumes as small as 200 microl, correlated well with conventional blood culture results obtained for neonates suspected of having bacterial sepsis.     

Candidal and bacterial bloodstream infections in premature neonates: a case-control study.

Nosocomial bloodstream infections (BSI) in premature neonates are an important cause of morbidity and mortality. The early and efficient diagnosis of a neonatal BSI and the differentiation between bacterial and fungal BSI remains a challenging task. We compared the clinical features and blood test results in preterm infants with proven candidal or bacterial BSI in order to identify potential risk factors for developing a candidal BSI. Preterm infants with proven candidal BSI were significantly more prematurely born (mean age of gestation 27.7 vs. 29.8 weeks), had previously received significantly more antibiotics of multiple classes (mean 4.4 vs. 1.2) for significantly longer periods (mean 19.3 vs. 3.2 days), were ventilated more intensively, had a significantly longer stay at the neonatal intensive care unit before the onset of the BSI (mean 26.5 vs. 9.4 days), and had C-reactive protein values even higher than in preterm infants with a bacterial BSI (mean 90 vs. 71 mg l(-1)). The presence of thrombocytopenia ( < 150 x 10(9) cells l(-1)) in all the preterm infants with candidal BSI was a significant difference. No differences were seen with regard to birth-weight, use of central intravascular catheters, total parenteral nutrition, white blood cell count and differentiation. In conclusion, candidal BSI can be strongly expected after the third week of admittance in the most premature neonates on a respirator and treated with multiple classes of antibiotics for a prolonged period of time. The presence of these risk factors in a 'septic' premature infant on antibiotic treatment justifies the empiric use of antifungals.     

Usefulness of surveillance cultures in neonatal extracorporeal membrane oxygenation

Sepsis is difficult to identify in patients treated with extracorporeal membrane oxygenation (ECMO). This study evaluates the usefulness of surveillance cultures obtained during ECMO. We retrospectively reviewed the records of 187 patients from four ECMO centers with birth weights 1,574 to 4,900 gm and gestational ages 33-43 weeks, over a 4 year interval. Most patients had surveillance blood cultures daily, and tracheal aspirates and urine culture every other day. Charts were reviewed for culture results before, during, and for the 7 days after ECMO, and clinical response to the culture results. A total of 2,423 cultures were obtained during 1,487 days of ECMO, of which 155 were positive (6.4%): 13 of 1,370 blood cultures (0.9%), 137 of 850 tracheal aspirate cultures (16%), and 5 of 203 urine cultures (2.3%). After 72 hours, tracheal aspirate cultures became positive with nosocomial organisms in 33 of 131 patients. None of 153 bacterial urine cultures were positive, and only one of 34 viral urine cultures were positive (CMV). We conclude that routine daily blood cultures are not useful in neonatal ECMO. Tracheal aspirate cultures may be helpful in the management of antibiotic therapy in patients on ECMO for more than 5 days. Routine bacterial urine cultures did not provide useful information.     

Methicillin-resistant Staphylococcus aureus: a three-year epidemiological and microbiological survey of high-risk patients

In order to assess the frequency, and epidemiological and microbiological features, of respiratory and blood stream infection due to methicillin-resistant Staphylococcus aureus in high-risk patients, all S. aureus strains cultured from reliable clinical specimens (respiratory secretions obtained by tracheo-bronchial aspirate or bronchoalveolar lavage, or blood cultures), were prospectively evaluated over a three-year period, in six inpatient wards selected on the ground of an elevated frequency of severe and/or nosocomially-acquired infections, because of the prevalence of immunocompromised patients, organ transplant recipients, or need of intensive care. Repeatedly positive cultures obtained from a single patient within 30 days were considered as one isolate. Of 507 S. aureus strains responsible for pneumonia or sepsis in the selected wards, 317 (62.5%) proved methicillin-resistant, in absence of significant variations throughout the study period, and according to the specimen origin. Methicillin-resistant S. aureus strains prevailed over sensitive ones in all examined wards (from a 95% rate of the respiratory intensive care unit, to 55.9% of the pneumology department), save the neonatal and pediatric intensive care unit (41.4%). Most of methicillin-resistant S. aureus isolates were recovered from lower airways, compared with blood cultures (p<.0001). The majority of the 317 methicillin-resistant strains were found in the general intensive care unit (42.6%), followed by the pneumology department (18%), and the respiratory intensive care unit (16.4%). Among methicillin-resistant S. aureus strains, a broad variation of sensitivity to other antimicrobial agents was observed: from 3.3% of erythromycin, to 76.9% of chloramphenicol, and 79.7% of cotrimoxazole; glycopeptide antibiotics remained effective against all cultured strains. In our three-year survey of more than 500 episodes of documented staphylococcal infection involving high-risk patients, methicillin resistance was a very common feature, observed at a greater frequency than that reported in literature studies focusing on surgical, pneumological, or intensive care settings. A long-term microbiological monitoring of high-risk inpatient wards may allow a continued update of local antimicrobial susceptibility maps, and significantly add to both chemoprophylaxis and empiric treatment strategies of patients which are either immunocompromised or hospitalized for a long period.     

Connection between gut microbiome and brain development in preterm infants

Dysbiosis of the gut microbiome in preterm infants predisposes the neonate to various major morbidities including neonatal necrotizing enterocolitis and sepsis in the neonatal intensive care unit, and adverse neurological outcomes later in life. There are parallel early developmental windows for the gut microbiota and the nervous system during prenatal to postnatal of life. Therefore, preterm infants represent a unique population in which optimization of initial colonization and microbiota development can affect brain development and enhance neurological outcomes. In this review, we will first discuss the factors affecting the assembly of neonatal gut microbiota and the contribution of dysbiosis in preterm infants to neuroinflammation and neurodevelopmental disorders. We then will discuss the emerging pathways connecting the gut microbiome and brain development. Further we will discuss the significance of current models for alteration of the gut microbiome (including humanized gnotobiotic models and exposure to antibiotics) to brain development and functions. Understanding the role of early optimization of the microbiome in brain development is of paramount importance for developing microbiome-targeted therapies and protecting infants from prematurity-related neurodevelopmental diseases.     

Infections fongiques invasives du grand prématuré

Fungal infections were frequent in premature baby (<1500 g) and were associated with significant morbidity and mortality. In this paper we review the risk factors for invasive fungal infections and clinical settings. A better understanding of the mechanism of fungal infection in preterm infants is important in treatment and prevention. The early neonatal intensive care unit course favours colonization and proliferation of fungi since many preterm infants have central catheters and are exposed to broad spectrum antibiotics and parenteral nutrition. The majority of fungal infections in preterm neonates are due to Candida, with a small number due to other yeasts such as Malassezia. Candida is an opportunistic pathogen, which adheres to the skin, mucosal, and catheter surface. C. albicans account for 50% of cases of fungal sepsis. C. parapsilosis is the second most prevalent species in very low birth weight children; its frequency increased from 1995 to 2000. Risk factors for fungal colonization are: very low birth weight, exposure to broad spectrum antibiotics, parenteral nutrition and use of corticosteroids. Colonization of the skin, gastro-intestinal tract and respiratory tract and central vascular catheter precede infection. The majority of preterm infants with fungal infections develop thrombocytopenia, but this is a common feature shared with other sepsis. The evaluation of infants with fungal sepsis should include cerebrospinal fluid examination and culture of urine with surveillance for endocarditis, renal, liver and brain abscesses and endophthalmitis. The mortality rate can reach 30%, and is higher in very low birth weight infants.     

Respiratory Deleted in Malignant Brain Tumours 1 (DMBT1) levels increase during lung maturation and infection

Deleted in Malignant Brain Tumours 1 (DMBT1) is a secreted scavenger receptor cysteine-rich protein that binds and aggregates various bacteria and viruses in vitro. Studies in adults have shown that DMBT1 is expressed mainly by mucosal epithelia and glands, in particular within the respiratory tract, and plays a role in innate immune defence. We hypothesized that respiratory DMBT1 levels may be influenced by various developmental and clinical factors such as maturity, age and bacterial infection. DMBT1 levels were studied in 205 tracheal aspirate samples of 82 ventilated preterm and full-term infants by enzyme-linked immunosorbent assay. Possible effects of various clinical parameters were tested by multiple regression analysis. DMBT1 levels increased significantly with lung maturity (P < 0.0001 for both gestational and postnatal age) and in small-for-gestational-age infants (P = 0.0179). An increase of respiratory DMBT1 levels was detected in neonatal infections (P < 0.0001). These results were supported by Western blotting. Immunohistochemical analyses of archived newborn lung sections (n = 17) demonstrated high concentrations of DMBT1 in lungs of neonates with bacterial infections. Our data show that preterm infants are able to up-regulate DMBT1 in infection as an unspecific immune reaction.     

新生儿血小板减少症46例临床分析

目的分析新生儿血小板减少的临床特点及可能原因,探讨其预防和治疗措施。方法回顾性分析本院2008年1月～2009年7月诊断新生儿血小板减少症所有患儿的临床资料。结果早发型血小板减少患儿临床上多无特殊表现,预后较好;迟发型血小板减少症多发生于早产儿,小于胎龄儿,通常由于合并严重感染所致,病情严重,需要输注血小板来治疗。结论围产期有高危因素母亲,其新生儿出生后要常规监测血常规,对于宫内发育不良或低出生体质量儿生后一旦合并感染要警惕血小板减少,甚至DIC的发生。     

Molecular epidemiology of coagulase-negative staphylococci causing sepsis in a neonatal intensive care unit over an 11-year period

Coagulase-negative staphylococci (CoNS) are the major causative microorganisms in neonatal nosocomial sepsis. Previous studies have shown that CoNS sepsis in the neonatal intensive care unit (NICU) is caused by predominant molecular types that are widely distributed among both neonates and staff. Some of these molecular types may persist in the NICU for years. The purpose of the present study was to determine the dynamic behavior of CoNS strains causing sepsis over a prolonged period of time by determining the molecular types of all blood isolates from septicemic infants over a period of 11 years (1991 to 2001). The results show that neonatal CoNS sepsis is increasingly caused by a few predominant molecular clusters. The most striking finding was that in recent years one molecular cluster emerged as the predominant cause of neonatal CoNS sepsis, responsible for no less than 31% (20 of 65) of blood isolates in 2001. Antibiotic resistance, particularly beta-lactam resistance, is probably an important selective force considering the high mecA gene carriage of CoNS blood isolates (70 to 92%). We conclude that neonatal CoNS sepsis is increasingly caused by a limited number of predominant molecular CoNS types and that antibiotic resistance is probably a major selective force.     

Outbreak of necrotizing enterocolitis associated with Enterobacter sakazakii in powdered milk formula

We describe an outbreak of necrotizing enterocolitis (NEC) that occurred in the neonatal intensive care unit of our hospital. A total of 12 neonates developed NEC in June-July 1998. For two of them, twin brothers, the NEC turned out to be fatal. Enterobacter sakazakii, a known contaminant of powdered milk formula, was isolated from a stomach aspirate, anal swab, and/or blood sample for 6 of the 12 neonates. A review of feeding procedures revealed that 10 of the 12 patients were fed orally with the same brand of powdered milk formula. E. sakazakii was isolated from the implicated prepared formula milk as well as from several unopened cans of a single batch. Molecular typing by arbitrarily primed PCR (AP-PCR) confirmed, although partially, strain similarity between milk and patient isolates. No further cases of NEC were observed after the use of the contaminated milk formula was stopped. With this outbreak we show that intrinsic microbiological contamination of powdered milk formula can be a possible contributive factor in the development of NEC, a condition encountered almost exclusively in formula-fed premature infants. The use of sterilized liquid milk formula in neonatal care could prevent problems with intrinsic and extrinsic contamination of powdered milk formula.     

Cell-associated interleukin-8 in cord blood of term and preterm infants

To assess the effect of gestational age and labor on the interleukin-8 (IL-8) concentration in whole cord blood and serum, IL-8 levels were determined simultaneously in cord blood serum and lysate in 134 infants. Following the elimination of some of the samples due to exclusion criteria, the data for 99 uninfected infants (71 term and 28 preterm) and 9 infants with neonatal bacterial infection delivered either vaginally or by elective or emergency cesarean section were analyzed. The effects of labor and gestational age were tested by analysis of variance. IL-8 was not detectable in the serum of 25 infants, whereas IL-8 levels in whole blood were measurable in all of the samples. The median IL-8 conncentrations in whole cord blood lysate were 106 pg/ml (range, 20 to 415 pg/ml) in preterm infants and 176 pg/ml (range, 34 to 1,667 pg/ml) in term infants. In contrast to the IL-8 levels in serum, IL-8 levels in whole blood were reduced after ECS. Gestational age had no independent effect on the IL-8 concentrations in either serum or whole blood; these concentrations increased in infected infants after labor. We conclude that the neonatal proinflammatory response to labor stress was more evident in the concentrations of IL-8 in whole blood than in serum. The levels of IL-8 in whole-blood lysate reflect proinflammatory stimulation in neonates and may be a useful diagnostic tool for the early diagnosis of neonatal infection.     

Cell-Associated Interleukin-8 in Cord Blood of Term and Preterm Infants

To assess the effect of gestational age and labor on the interleukin-8 (IL-8) concentration in whole cord blood and serum, IL-8 levels were determined simultaneously in cord blood serum and lysate in 134 infants. Following the elimination of some of the samples due to exclusion criteria, the data for 99 uninfected infants (71 term and 28 preterm) and 9 infants with neonatal bacterial infection delivered either vaginally or by elective or emergency cesarean section were analyzed. The effects of labor and gestational age were tested by analysis of variance. IL-8 was not detectable in the serum of 25 infants, whereas IL-8 levels in whole blood were measurable in all of the samples. The median IL-8 conncentrations in whole cord blood lysate were 106 pg/ml (range, 20 to 415 pg/ml) in preterm infants and 176 pg/ml (range, 34 to 1,667 pg/ml) in term infants. In contrast to the IL-8 levels in serum, IL-8 levels in whole blood were reduced after ECS. Gestational age had no independent effect on the IL-8 concentrations in either serum or whole blood; these concentrations increased in infected infants after labor. We conclude that the neonatal proinflammatory response to labor stress was more evident in the concentrations of IL-8 in whole blood than in serum. The levels of IL-8 in whole-blood lysate reflect proinflammatory stimulation in neonates and may be a useful diagnostic tool for the early diagnosis of neonatal infection.     

A quantitative analysis of Ureaplasma urealyticum and Ureaplasma parvum compared with host immune response in preterm neonates at risk of developing bronchopulmonary dysplasia

Multiplex, real-time PCR for the identification of Ureaplasma urealyticum and Ureaplasma parvum was performed on nucleic acids extracted from sequential endotracheal aspirates obtained from preterm neonates born at <29 weeks of gestation and ventilated for more than 48 h admitted to two level 3 neonatal intensive care units. Specimens were obtained shortly after birth and sequentially up until extubation. One hundred fifty-two specimens (93.8%) contained material suitable for analysis. Ureaplasma spp. were identified in 5 of 13 neonates studied. In most cases, the DNA load of the detected Ureaplasma species was low and decreased over time. In addition, changes in detectable Ureaplasma species DNA did not relate to changes in the inflammatory marker C-reactive protein (CRP) or respiratory status. All but two blood samples obtained at times of suspected sepsis were culture positive for other microorganisms; the species cultured were typically coagulase-negative staphylococci and were associated with increased levels of CRP (>10 mg/liter). This study was limited by the small number of patients examined and does not have the power to support or contradict the hypothesis that postnatal lung infection with Ureaplasma parvum is causally related to bronchopulmonary dysplasia (BPD) or adverse respiratory outcomes after preterm birth. However, in this study, increases in CRP levels were not associated with patients in whom Ureaplasma parvum was detected, in contrast to the detection of other bacterial species.     

Colonization pattern of coagulase-negative staphylococci in preterm neonates and the relation to bacteremia

Coagulase-negative staphylococci (CoNS) are the major cause of sepsis in extreme preterm (EPT) newborns, but data on the CoNS colonization in EPT newborns prior to invasive infection are limited. Our aim was to describe the early establishment of the CoNS microflora in EPT newborns and to compare the colonization pattern in neonates with and without positive CoNS blood cultures. From a cohort of 46 EPT neonates, newborns with positive CoNS blood culture were identified (n = 10) and compared with matched controls. Samples for bacterial cultures were obtained repetitively from nares, perineum, and umbilicus. All CoNS isolates were characterized using the PhenePlate system for biochemical fingerprinting. Persistent CoNS strains were found on day 2–3 after delivery in 7/20 newborns, and there was a tendency for earlier colonization in nares than in the perineum or umbilicus. The CoNS blood strains were prevalent in superficial sites prior to positive blood culture (11/14 blood strains), but no single invasive pathway was identified. Most CoNS blood strains (9/14) persisted on superficial sites after antibiotic treatment. We hypothesize that the invasive pathways in neonatal CoNS sepsis are complex and that the colonization of mucosal membranes and umbilical catheters might be of equal importance.     

Antibiotic susceptibility of blood culture isolates after nearly two decades with netilmicin and ampicillin in neonatal septicaemia

The aim of the study was to investigate the in vitro antibiotic susceptibility of blood culture isolates after almost 20 years with ampicillin and methicillin as empirical treatment for neonatal septicaemia. All blood culture isolates and their antibiograms obtained in a single tertiary neonatal intensive care unit from 1 January 1989 to 31 December 1994 were reviewed. Two hundred and six blood cultures from 181 infants containing 223 bacterial and 11 fungal isolates were identified during 4416 admissions. Fifteen (6.7%) of the bacterial isolates were resistant to ampicillin and netilmicin. Fourteen per cent of the staphylococcal spp. were susceptible to penicillin while more than 90% were susceptible to netilmicin. The coagulase-negative staphylococci (CONS) were resistant to netilmicin, methicillin and gentamicin in 12%, 49% and 65%, respectively. Eighty-nine per cent of the methicillin-resistant CONS were susceptible to netilmicin as opposed to 17% to gentamicin (p<0.001). Except for one strain of Acinetobacter sp., all Gram-negative bacteria were susceptible to netilmicin. Our data show that the ampicillin-netilmicin combination still provides a high in vitro coverage (93%) against bacteria identified in blood cultures from newborns in our unit. Netilmicin has a significantly better in vitro effectiveness against CONS than gentamicin.     

Detection of anaerobic wound infection by analysis of pus swabs for volatile fatty acids by gas-liquid chromatography.

Swabs were able to absorb enough extractable volatile fatty acids from broth cultures of anaerobic organisms for detection and analysis by gas-liquid chromatography (GLC). Similarly, volatile fatty acids were often detected in swabs dipped into liquid pus. Fifty-three liquid pus specimens were then investigated fully to determine if GLC analysis of swab samples gave the same result as microbial culture of the specimens and GLC analysis of the liquid pus. Anaerobic bacteria failed to grow from 36 and volatile fatty acids were not extracted from swabs of 31 of these pus samples but were extracted from swabs of five. Anaerobic bacteria were isolated from 17 of the specimens, and in 15, volatile fatty acids were also detected in the swab samples; in two, volatile fatty acids were absent from both swab samples and liquid pus. In this study, results by culture and GLC analysis of swabs were similar in 87% of specimens.