Molecular characterization of the coagulase-negative staphylococcal surface flora of premature neonates.

A single point study was conducted to determine which surface sites best represent the density and composition of the coagulase-negative staphylococcal (CNS) colonizing flora in premature neonates. Five different surface sites of six randomly selected neonates hospitalized in a neonatal intensive care unit (NICU) for a month were examined. The individual strains and their clonal organization within CNS species were identified using restriction endonuclease fingerprinting of whole chromosomal DNA and ribosomal RNA genes. Cultures of the scalp, umbilicus, foot, nose and rectum were collected and quantitatively processed. Ten colonies were typed per surface culture. The most dense CNS colonization was noted on the umbilicus (mean 1.2 x 10(4) c.f.u. cm-2), foot (mean 1.6 x 10(3) c.f.u. cm-2) and nose (mean 1.7 x 10(3) c.f.u. cm-2) of NICU neonates. Scalp and rectum were scarcely colonized. Of all the CNS surface isolates, S. epidermidis accounted for 77.7% (219/282) and S. haemolyticus, S. warneri and S. capitis accounted for 20.6% (58/282), 1.4% (4/282) and 0.4% (1/282), respectively. Colonization of each surface site comprised a maximum of five different strains representing four CNS species. Overall, five clones of S. epidermidis, two of S. haemolyticus, one of S. warneri and one of S. capitis were noted among the 282 isolates. The most predominant were two clones of S. epidermidis and one of S. haemolyticus; they accounted for 94% (265/282). Cultures from the foot and scalp represented the most heterogeneous CNS colonization of the five sites examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Enteral feeding of premature infants with Lactobacillus GG.

The objectives of this study were to determine whether or not the probiotic Lactobacillus GG can colonise the immature bowel of premature infants and if so, does colonisation result in a reduction of the size of the bowel reservoir of nosocomial pathogens such as enterobacteriaceae, enterococci, yeasts or staphylococci, and does colonisation with Lactobacillus GG have any effect on the clinical progress and outcome. Twenty preterm infants with a gestational age of 33 weeks or less who were resident on a neonatal unit were studied from the initiation of milk feeds until discharge. The infants were randomised to receive either milk feeds or milk feeds supplemented with Lactobacillus GG 10(8) colony forming units twice a day for two weeks. The clinical features of the two groups of infants were similar. Orally administered Lactobacillus GG was well tolerated and did colonise the bowel of premature infants. However, colonisation with Lactobacillus GG did not reduce the faecal reservoir of potential pathogens and there was no evidence that colonisation had any positive clinical benefit for this particular group of infants.

Effects of feeding premature infants with Lactobacillus GG on gut fermentation.

The study aimed to find out whether gut colonisation of premature babies with a probiotic, Lactobacillus GG, modified enteric carbohydrate fermentation. Twenty preterm infants were randomised to receive Lactobacillus GG 10(8) colony forming units twice a day for two weeks or to a control group. Faecal short chain fatty acids (SCFAs), ethanol, and urinary 2,3-butanediol, were measured in parallel with microbiological studies. Lactobacillus GG colonised nine babies. From 1-28 days of age faecal SCFAs did not differ significantly from controls. Median and ranges were (treated and controls, respectively): acetic acid: 173 (trace-799), 166 (trace-700); propionic acid: 44 (trace-169), 37 (11-229); butyric acid: 31 (5-107), 37 (2-118) mumol/g dry weight. Ethanol was detected in more faecal samples from treated babies (65% v 37%), and at higher concentration (6.3 (trace-40) v 3.3 (0.6-8.8; one 229) mumol/g). 2,3-Butanediol was found in 66% of urine samples from treated babies and 58% from controls. On 83% of these occasions Klebsiella sp, Enterobacter sp, or Serratia sp were cultured from faeces. Lactobacillus GG had no obvious adverse effects on nutritionally important SCFAs. The small increase in ethanol excretion is unlikely to have clinical significance.

Leukocyte counts and colonization with Ureaplasma urealyticum in preterm neonates.

In this paper we review the literature, present previously unpublished case reports for a pair of twins, and provide data from two prospective cohort studies to determine whether nasopharyngeal and/or endotracheal colonization with Ureaplasma urealyticum in preterm neonates is associated with an elevated white blood cell (WBC) count. We observed an association between colonization of the respiratory tract and elevation in the WBC count caused by an increase in the number of mature and immature neutrophils. Such a response indicates that U. urealyticum is capable of eliciting an inflammatory reaction and may be a true pathogen in the neonate. If these increases in the WBC count are confirmed, the WBC count may be a useful marker in future trials of interventions directed at U. urealyticum.

Respiratory syncytial virus-specific immunoglobulins in preterm infants.

Incomplete transfer of maternal antibodies specific to respiratory syncytial virus (RSV) has been suggested as an explanation for the increased risk of RSV infections in preterm infants. Antibodies directed against the two major RSV envelope glycoproteins, F and G, are protective in vitro and in vivo. Our study was conducted to measure IgG, IgG1, IgG2, and IgG3 antibody titers against the RSV F and G glycoproteins in cord sera from infants born at different gestational ages. Titers of neutralizing antibody were measured in a subset of the subjects. The mean (+/- SEM) log2 titers of IgG antibodies directed against the RSV F and G glycoproteins were significantly lower in infants born at < or = 28 weeks of gestation (11.2 and 10.8 for F and G glycoproteins, respectively) than in term infants (12.6 and 12.8 for F and G, respectively) (p < 0.05). Preterm infants born at > or = 29 weeks had titers of antibodies against the F glycoprotein comparable to those of term infants. The highest titers of RSV-specific antibodies were in the IgG1 and IgG2 subclasses. Mean (+/- SEM) neutralizing antibody titers were lower in infants born at < or = 28 weeks (7.7 +/- 0.4) than in term infants (10.2 +/- 0.3) (p < 0.001). We conclude that (1) RSV-specific antibody titers were lower than in term infants only in the most premature infants (< or = 28 weeks) and (2) preterm infants born at > or = 29 or > or = 33 weeks of gestation had RSV-specific titers against F and G glycoproteins, respectively, that were comparable to those of term infants. Preterm infants born at < or = 28 weeks could represent a target population for passive immunoprophylaxis.

Prevalence and toxigenicity of Clostridium difficile isolates in fecal microflora of preterm infants in the intensive care nursery.

Fecal isolates of Clostridium difficile and its toxin B were followed prospectively in 50 preterm intensive care nursery (ICN) patients. The first stool specimen was obtained after 1 week of enteral feeding, at 15 +/- 1 days of life, and 2 more specimens were collected at 2-week intervals, 24 +/- 1 and 32 +/- 2 days of life. The stools were cultured for C. difficile, and tested for C. difficile toxin B. In the first specimen 15% of stools grew C. difficile. In the second specimen C. difficile isolation rates increased to 33% and plateaued. Toxin B was detected in 71, 93 and 100% of culture-positive stools in the first, second, and third specimens, respectively. C. difficile colonization was not associated with a higher incidence of necrotizing enterocolitis or diarrhea, and using precollected, frozen human milk did not protect from C. difficile colonization.

Prevention and control of nosocomial infection caused by methicillin-resistant Staphylococcus aureus in a premature infant ward--preventive effect of a povidone-iodine wipe of neonatal skin.

In early 1983 we experienced a small scale epidemic of Staphylococcus aureus coagulase type IV in the premature infants unit. Children had bacteraemia or impetigo. The microorganism was resistant to methicillin, erythromycin and lincomycin and was susceptible to tetracycline, chloramphenicol and cefmetazole. The results of coagulase typing and antimicrobial sensitivities indicated that these cases represented nosocomial infection with MRSA. The source and route of the infection were investigated, and measures were taken to prevent bacterial spread from carriers and to keep instruments and environments clean. As the source of infection was not identified, we tried wiping the body surface of the premature infants with a diluted IsodineR solution (10% povidone-iodine; 1:100 dilution) in order to prevent colonization of the microorganism on the body surface. As a result, no additional MRSA infection occurred in the premature infant unit. During the subsequent 6 years of frequent surveys of carriers and wiping the appropriate body surface with diluted IsodineR solution we have had no recurrence of MRSA. None of the premature infants wiped with IsodineR solution showed any objective abnormalities, although laboratory testing disclosed an elevated blood iodine level and a transient mild reduction of T4 in some infants.

An analysis of the microbial flora of premature neonates.

An analysis of the microbial flora of 10 premature neonates hospitalized in a neonatal intensive care unit (NICU) was made. The babies had received neither antibiotics nor antiseptics and nine out of 10 were born by caesarean section. Samples were collected on the fourth or fifth day of life from 18 skin or mucosal sites. Detailed bacterial counts were obtained by plating out suitable dilutions of the samples on to selective media. Representative samples of each colony type were then subcultured and identified, using standard laboratory methods. Two hundred and fifty-six isolates of staphylococci were obtained and their susceptibility to 23 antibiotics tested. Only 11% of the samples were sterile. Coagulase-negative staphylococci (CNS) were the commonest species isolated and were predominant in every site studied. They were found in 79% of the samples and represented almost 81% of the neonates' flora. Eight species and biotypes of CNS were identified. In decreasing order of frequency, they comprised S. epidermidis (biotypes 1 and 2), S. hominis (biotype 1), S. warneri, S. haemolyticus, S. capitis, S. cohnii and S. hominis (biotype 2). CNS distribution appeared to be highly heterogeneous with no significant specificity of any species for a particular body site. The main quantitative and qualitative variations seemed to relate to the method of delivery, and the intensity and nature of exposure of the neonate to its local environment. A high level of antibiotic resistance was found among the CNS isolates (especially S. epidermidis and S. haemolyticus): penicillin G (96%), oxacillin (31%), erythromycin (52%) and gentamicin (28%). Moreover, multiresistant strains were numerous, supporting the nosocomial origin of CNS.

Development of cutaneous microflora in premature neonates.

Coagulase-negative staphylococci (C-NS) are a frequent cause of bacteraemia in premature neonates. It is likely that the strains of C-NS causing bacterial sepsis in premature neonates have their origin on the patient's skin surface. We have studied the quantitative development of the skin microflora at eight sites on premature neonates. A swab wash method was used to sample and enumerate the cutaneous microflora of premature neonates admitted to an intensive care unit with respiratory distress syndrome. The numbers of bacteria present on the skin increased rapidly by 100-fold in the first week of life. The species of C-NS found on neonatal skin were similar to those found on adult skin. However, the bacterial population was 10(3) lower by comparison. There was considerable variation in numbers of bacteria and in the proportion resistant to antibiotics from day to day. There appeared to be no association between antibiotic usage and the proportion of isolates resistant to antibiotics, although the resident bacteria were in many cases resistant to a variety of antibiotics. C-NS were isolated from 92% of samples from which bacteria were isolated. Staphylococcus epidermidis was found at all sites and accounted for 82% of each colonial type of staphylococcus isolated. Other organisms isolated included Propionibacterium sp, alpha-haemolytic streptococci, aerobic spore-bearing bacilli, aerobic coryneforms, Candida albicans, Klebsiella oxytoca, Pityrosporum sp, Klebsiella pneumoniae, and Escherichia coli. The results of this study suggest that the skin of premature neonates is colonised with antibiotic resistant C-NS during the first week of life and that the chance of contamination of an intravascular catheter at insertion increases during this period.

Fungal gut colonization with Candida or Pityrosporum sp. and serum Candida antigen in preterm neonates with very low birth weights.

To evaluate the diagnostic value of gut colonization by yeasts and of candida antigen in serum for predicting fungal infection in very premature neonates, faecal and serum samples were obtained biweekly from 27 newborn babies treated at our neonatal intensive care unit. Altogether 82 sets of serum and faecal samples were obtained. 17 babies were followed for > or = 4 weeks. Blood cultures, both by routine and lysis centrifugation techniques, were performed for bacteria and fungi if infection was suspected. All children were given systemic broad-spectrum antibiotic treatment. Five of the children died, all without evidence of fungal infection. No systemic antifungal treatments were given. Quantitative faecal cultures demonstrated Candida albicans in 3 (11%) (10(3)-10(5) colony forming units/g) and Pityrosporum sp. in 8 (30%) of the preterm neonates. Candida antigen in titre 4 was detected in 1/82 serum samples. The child subsequently died with no other evidence of candida infection. In 56 full term neonates treated at the intensive care unit during the same period and tested by 1 set of samples, faecal colonization with Candida sp. was detected in 2 (4%) and with Pityrosporum sp. in 4 (15%). None were positive for candida antigen. Fungal gut colonization did not lead to clinical infection in the preterm neonates studied. The false positivity rate of the candida antigen test was low (0.7%). The predictive value of the test could not be determined in this study group with no systemic fungal infections. The role of pityrosporum as an inducer of neonatal infections remains to be evaluated.

Candida strains from neonates in a special care baby unit.

Carriage and acquisition of Candida spp and Candida albicans biotypes were studied among 163 neonates and 90 staff in a neonatal intensive care and surgical unit during a 17 week period. Twenty one neonates carried yeasts in the mouth, rectum or groin when first sampled, and a further 25 were positive later. C albicans accounted for 94.7% of 431 yeast isolates from neonates but only 67.4% of 43 isolates from staff. The first isolated C albicans biotype persisted in 13 babies monitored longitudinally. Simultaneous colonisation with two Candida spp was found in 2/46 neonates and 5/33 staff. The prevalence of candida was significantly higher among babies of gestational age less than 28 weeks (65%) than those of higher gestational age (26%). Oral and/or crural candida infection was observed in 14 of the babies but none developed deep seated candidosis. Routine antifungal prophylaxis did not affect the frequency of yeasts among the neonates.

Comparison of blood cultures with corresponding venipuncture site cultures of specimens from hospitalized premature neonates.

We compared the presence and identities of isolates from blood culture samples obtained by percutaneous venipuncture with those of commensal skin organisms cultured from respective venipuncture sites after skin cleansing; 677 blood and skin site culture pairs from 488 infants were compared. Organisms grew in 58 blood cultures; nine of these cultures had corresponding venipuncture site cultures that also grew organisms. Forty-two blood culture isolates were coagulase-negative staphylococci; five of these were associated with similar venipuncture site cultures. According to restriction-endonuclease fingerprinting of chromosomal DNA and plasmid analysis, three pairs of blood and venipuncture site cultures were identical and two pairs were different. Thus only 7% (3/42) of coagulase-negative staphylococcal blood isolates were associated with identical contamination at the venipuncture site. We conclude that, if the venipuncture site has been carefully cleansed, the growth of coagulase-negative staphylococci in blood cultures of specimens from premature neonates indicates bacteremia rather than skin contamination in the vast majority of cases.

Acute phase reactants in neonatal bacterial infection.

The C-reactive protein (CRP) level was evaluated in 142 infants requiring investigation for suspected infection. After excluding two neonates because of incomplete data, there remained 140 neonates, of whom 16 had septicemia. Fifteen of 16 had increased CRP levels. The CRP value was not elevated in any baby (n = 5) who had positive blood cultures for Staphylococcus epidermidis, all of whom had an uneventful clinical course. The CRP level was elevated in all six babies with meconium-aspiration syndrome, but was normal in five infants whose viral cultures were positive. Ninety-nine percent of uninfected babies had normal CRP values. Overall, CRP was a valuable test for diagnostic confirmation of bacterial infection. Elevated CRP level was always accompanied by at least one abnormality in the other tests performed. Although the study was not intended to predict clinical onset of bacterial disease, our results suggest that the CRP level, because of a high negative predictive value, may be useful in ruling out bacterial infection.

[Value and limits of research on Mycoplasma hominis and Ureaplasma urealyticum in the gastric fluid of newborn infants]. / Intérêt et limites de la recherche de Mycoplasma hominis et Ureaplasma urealyticum dans le liquide gastrique des nouveau-nés.

Mycoplasma hominis and Ureaplasma urealyticum were cultured and counted in the gastric fluid of 153 neonates divided into three groups: 28 preterm neonates managed in an intensive care unit (Group I); 83 full term neonates with suspected infection (Group II); and 42 full term neonates with no evidence of infection (Group III). The colonization rate (17.85%) in the intensive care unit group was not significantly different from the rates seen in the two other groups. These results do not militate against the pathogenic role of the two organisms studied but rather suggest a contributory role of other factors.

Coagulase negative staphylococcal septicemia in newborns.

The case records of 2177 newborn infants admitted in the Neonatal Intensive Care Unit (NICU) from January, 1989, through July, 1990, with positive blood cultures for coagulase-negative staphylococci (C-NS) were evaluated. Seventy four (3.4%) neonates yielded C-NS in blood cultures during the study period. Of these, 58 (2.7%) infants had clinical and hematological features compatible with the diagnosis of septicemia. Remaining 16 babies with positive cultures had no evidence of sepsis, and were designated as "C-NS bacteremia". The age at which positive cultures were obtained differed between the bacteremic and septicemic groups. In bacteremic group, the onset occurred between one to four days of age. In contrast, in septicemic group the range was 6-20 days, with a mean of 10.22 (+/- 3.53) days. More than two third of total cases of C-NS sepsis were premature and low birth weight (LBW). Prominent clinical features included lethargy, poor feeding and fever. Besides this apneic spells were seen predominantly in babies weighing less than 1500 g. Further, before the diagnosis of C-NS sepsis, more than half of neonates had received prolonged intravenous fluid therapy, a quarter had undergone umbilical catheterization and a further quarter needed a ventilator support. Overall mortality in C-NS sepsis was 17.24%, distinctly higher in neonates with RDS and those requiring mechanical ventilation (p less than 0.05). Only 1.34% C-NS isolates were resistant to all routinely used antibiotics and sensitivity was maximum with newer cephalosporins, ciproflox and amikacin.

Genital mycoplasmas in preterm infants: prevalence and clinical significance.

The genital mycoplasmas: Ureaplasma urealyticum and Mycoplasma hominis have recently assumed an increasing importance as neonatal pathogens. The aim of the present survey was to determine the prevalence of infections with these organisms in preterm infants in two neonatal intensive care units in Israel. Among 99 preterm infants, 24 (24%) harboured mycoplasmas in their throats shortly after birth. U. urealyticum was the most common organism. M. hominis was isolated only from 3 infants. Six out of 27 (22%) mechanically ventilated infants secreted U. urealyticum in their lower airways. The rate of colonization was inversely correlated with gestational age; 80% of infants younger than 28 weeks gestation were found to be colonized as opposed to 17.9% at 28-36 weeks of gestation. No mycoplasmas were isolated in blood cultures drawn from 146 infants and CSF cultures obtained from 47 preterm infants. Neonatal mortality, respiratory complications and intraventricular haemorrhage grade 3-4 were significantly increased in colonized infants. However, above gestational age of 27 weeks, colonization with mycoplasmas was not associated with a worse prognosis. We conclude that colonization with U. urealyticum is common in Israeli preterm infants, correlates inversely with gestational age and has no detrimental effect on neonatal morbidity and mortality of infants older than 27 wks of gestation.

Coagulase-negative staphylococcal infection in the neonate.

During the last decade, improved neonatal care has permitted the survival of extremely low birthweight infants who are at increased risk for the development of nosocomial infection. The coagulase-negative staphylococci currently represent the most frequent nosocomial pathogen isolated from infants in the newborn intensive care unit. This article details pathogenesis, clinical manifestations, diagnosis, treatment, and prevention of neonatal infection with this organism.