Determinants of acquisition and carriage of Staphylococcus aureus in infancy.

Nasal carriage of Staphylococcus aureus is a major risk factor for invasive S. aureus disease. The aim of this study was to define factors associated with carriage. We conducted a prospective, longitudinal community-based study of infants and their mothers for a period of 6 months following delivery. The epidemiology of carriage was examined for 100 infant-mother pairs. Infant carriage varied significantly with age, falling from 40 to 50% during the first 8 weeks to 21% by 6 months. Determinants of infant S. aureus carriage included maternal carriage, breastfeeding, and number of siblings. Bacterial typing of S. aureus was performed by pulsed-field gel electrophoresis and multilocus sequence typing. The majority of individuals carried a single strain of S. aureus over time, and the mother was the usual source for colonizing isolates in infants. The effect of other components of the normal nasal flora on the development of S. aureus carriage was examined in 157 consecutive infants. Negative associations (putative bacterial interference) between S. aureus and other species occurred early in infancy but were not sustained. An increasing antistaphylococcal effect observed over time was not attributable to bacterial interference. S. aureus carriage in infants is likely to be determined by a combination of host, environmental, and bacterial factors, but bacterial interference does not appear to be an ultimate determinant of carrier status.

Comparison of multilocus sequence typing and pulsed-field gel electrophoresis as tools for typing Staphylococcus aureus isolates in a microepidemiological setting.

Multilocus sequence typing (MLST) of Staphylococcus aureus is well suited to the study of global or long-term epidemiology, but its role in local epidemiology has not been defined. The present study has compared MLST with pulsed-field gel electrophoresis (PFGE) by using S. aureus isolates associated with carriage and disease in a busy regional renal unit. One hundred forty-four patients were prospectively recruited, of whom 103 were receiving hemodialysis and 41 were on continuous ambulatory peritoneal dialysis. Three nasal swab specimens were obtained 1 month apart on entering the study. A nasal swab was positive for S. aureus on at least one occasion in 50 patients (35%). Typing of the 104 carriage isolates demonstrated 21 PFGE types and 21 sequence types (STs). Thirty-one carriers had two or more positive nasal swabs; of these, the isolates in all swabs from a given carrier had identical PFGE types for 29 carriers; the isolates in all of the same 29 swabs had identical STs. The carriage strain in two patients changed both PFGE type and STs during the period of swabbing. Eight patients (6%) had an episode of S. aureus bacteremia during the 12-month study period, and two of these were nasal carriers. One of these invasive isolates had the same PFGE type and ST as the carriage isolate. There were no differences between Simpson's index of diversity for PFGE and Simpson's index of diversity for MLST for both invasive and carriage isolates, suggesting that the two methods have very similar discriminatory abilities. We conclude that PFGE and MLST performed equally in this study.

The ica operon and biofilm production in coagulase-negative Staphylococci associated with carriage and disease in a neonatal intensive care unit.

Coagulase-negative staphylococci (CoNS) are a major cause of sepsis in the neonatal intensive care unit (NICU). We evaluated the hypothesis that the ica operon and biofilm production are associated with CoNS disease in this setting. CoNS associated with bacteremia or blood culture contamination and from the skin of infants with CoNS bacteremia or healthy controls were obtained during a prospective case-control study on a busy NICU. A total of 180 strains were identified, of which 122 (68%) were Staphylococcus epidermidis and the remainder were S. capitis (n = 29), S. haemolyticus (n = 11), S. hominis (n = 9), S. warneri (n = 8), and S. auricularis (n = 1). The presence of the genes icaA, icaB, icaC, and icaD was determined by PCR, and biofilm production was examined using qualitative (Congo red agar [CRA]) and quantitative (microtiter plate) techniques. There were no significant differences in the presence of the ica operon or CRA positivity among the four groups of strains. However, quantitative biofilm production was significantly greater in strains isolated from either the blood or the skin of neonates with S. epidermidis bacteremia. We conclude that the quantity of biofilm produced may be associated with the ability to cause CoNS infection. This conclusion suggests that the regulation of biofilm expression may play a central role in the disease process.

Genetic population structure of coagulase-negative staphylococci associated with carriage and disease in preterm infants.

Coagulase-negative staphylococci (CoNS) are a leading cause of sepsis in the neonatal intensive care unit (NICU) setting. To evaluate the hypothesis that isolates of CoNS associated with disease belong to hypervirulent clones, as opposed to being drawn randomly from the neonatal unit carriage flora, we conducted a prospective, case-controlled study in a busy NICU. Using pulsed-field gel electrophoresis (PFGE), we compared the population structures of CoNS isolates associated with bacteremia with isolates from the skin of healthy and infected neonates and with blood culture contaminants. Endemic clones of CoNS were identified, but there was no difference in the distribution of the 6 species or 73 PFGE types between the carriage and disease isolate groups; this suggests that hypervirulent clones with an enhanced ability to cause disease were not present in this NICU setting.

Obstetric performance, perinatal outcome and risk of infection to the newborn in spontaneous and artificial rupture of membranes during labour.

OBJECTIVE: To compare the obstetric performance, perinatal outcome and risk of neonatal infection in labour following spontaneous (SROM) and artificial (AROM) rupture of membranes. DESIGN: Prospective, non-randomised, comparative study during a one-month period in 1995. The study was approved by the ethics committee of the Faculty of Medicine, University of Colombo. SETTING: University Obstetrics Unit at De Soysa Hospital for Women, Colombo. PATIENTS: 324 women who were in early established labour after 37 weeks of gestation. 151 of these had SROM and 173 AROM. The AROM and SROM groups among primigravidae and multigravidae were considered separately. RESULTS: Oxytocin use in multigravidae was significantly higher in the AROM group than in the SROM group (p < 0.001). The emergency caesarean section (LSCS) rate in primigravidae was significantly higher in the AROM group than the SROM group (p < 0.001). A significantly larger number of primigravid AROM women had abnormal fetal heart rate changes on auscultation (p < 0.05) and cardiotopographic (CTG) patterns (p < 0.001) when compared with primigravid SROM women. Choreoamnionitis and funisitis were commoner in the AROM group although the difference was not statistically significant. CONCLUSIONS: AROM appears to be associated with a higher chance of fetal distress particularly in primigravidae. Both AROM and SROM are associated with a potential risk of infection at intrauterine sites.

PIP: Artificial rupture of the membranes during established labor is believed to augment labor progression, but this practice carries the risk of maternal and neonatal infection. A prospective study conducted at De Soysa Hospital for Women in Colombo, Ceylon, in 1995 compared the obstetric performance, perinatal outcome, and risk of neonatal infection in 151 women with spontaneous rupture of membranes (SROM) and 173 women with artificial rupture of membranes (AROM). The need for oxytocin was higher in both primi- and multigravidae in the AROM group (37.5% and 38.8%, respectively) than the SROM group (24.7% and 18.9%, respectively), but this association reached statistical significance only among multigravidae. Also higher in the AROM group than the SROM group, but not significantly, were the rates of instrumental delivery and emergency cesarean section. Compared with primigravid AROM women, a significantly larger number of primigravid AROM women had abnormal auscultated fetal heart rates and cardiotopographic patterns. The appearance of meconium in liquor and the occurrence of low Apgar scores were similar in both groups. There were no clinical maternal or neonatal infections, but the intrauterine sites showed evidence of inflammation soon after membrane rupture. 36.1% of women in the SROM group and 24.0% of those in the AROM group whose cord and membranes were evaluated had histologic evidence of inflammation. Choreoamnionitis and funisitis were slightly more common in the AROM group. The potential for infection at intrauterine sites had no linear relationship to the mean membrane rupture-delivery interval or the number of vaginal examinations.

Myocardial infarction in an infant due to anomalous origin of the left coronary artery.

Myocardial infarction in an infant due to anomalous origin of the left coronary artery from the pulmonary trunk is reported. The pathological features, haemodynamics related to morphology and differential diagnosis are discussed.

Is it Munchausen syndrome by proxy?

We describe two cases of children who were victims of illness fabricated by their mothers. Such clinical situations are identified as Munchausen syndrome by proxy (MSP). Although considered a form of child abuse, MSP often goes unrecognised in paediatric practice. The two children involved were unnecessarily investigated, and the underlying problems in the mothers were identified only after several hospital admissions. One mother had a major psychiatric disorder, and the other had serious marital problems. Maintaining a high degree of suspicion regarding inexplicable illness in a child with inappropriate or incongruous symptoms and signs, even when parents behave in an exemplary manner, would help in early diagnosis and management.