Randomly amplified polymorphic DNA analysis provides rapid differentiation of methicillin-resistant coagulase-negative staphylococcus bacteremia isolates in pediatric hospital

Influence of maternal bifidobacteria on the development of gut bifidobacteria in infants

Intestinal microbiota plays an important role in human health by influencing metabolic activities that result in the creation of energy and absorbable nutrients, a barrier to the colonization of pathogens, and stimulation of the immune system. The development of fecal microbiota in neonates is crucial because those bacteria are the first to colonize the sterile intestine of the neonates and, thus, have a significant effect on the host. Initial colonization is also relevant to the final composition of the permanent microbiota in adults. Bifidobacteria are predominant in the fecal microbiota of infants, and, therefore, they are important to an understanding of how commensal bifidobacteria is established in the intestine of infants. While the mother's bifidobacteria are considered to significantly influence the infant's bifidobacteria, it is not clear whether a specific bifidobacterial strain transmits vertically from mother to infant and what factors of the mother before delivery influence the establishment of intestinal bifidobacteria in infants. This review focuses on the impact of maternal bifidobacteria on the development of gut bifidobacteria in the infant and suggests that there is cumulative evidence regarding bifidobacterial transfer from the maternal gut or breast milk to the infant gut.

[Prospective analysis of central venous catheter colonization and related factors]

OBJECTIVE

To evaluate the incidence of central venous catheter (CVC) colonization in inpatient units of the Institut de Malalties Digestives i Metabòliques (IMDiM) of Hospital Clinic (Barcelona, Spain) with a view to reducing the risk of infection.

METHOD

A 4-month descriptive, prospective and longitudinal study was performed. A total of 230 patients admitted to the IMDiM with CVC were included during the study period. At catheter removal, the tip was cultured and, if the patient had fever, two blood cultures were also obtained. A database was created. Data were analyzed using SPSS v.11.0. Variables were compared with the Chi-square and Student's t-tests and a multivariate analysis was performed using Cox logistic regression. A value of P<0.05 was considered significant.

RESULTS

Catheter tip culture was positive in 45.2%. The rate of catheter-related bloodstream infections was 2.9 per thousand catheter-days, which was clinically significant. The probability of catheter tip contamination 10 days after placement was 25%. Multivariate analysis revealed that the independent variables associated with a higher risk of infection were catheter type, changes of dressing, and infected bacterial stopcocks.

CONCLUSIONS

These results suggest that: 1) the protocol for catheter insertion and care should be reviewed and updated, 2) catheter removal should be considered after the 10th day, 3) the appropriate type of catheter should be selected, the catheter with the lowest number of lumens should be used, and changes of catheter dressing should be reduced.

Typing of Neisseria gonorrhoeae Opa and NG-MAST gene of 12 pairs of sexual contact gonorrhea patients in China

To identify the genomic species of Neisseria gonorrhoeae, evaluate the difference between two molecular epidemiological methods and examine the relationship between sex partners and genotypes of bacteria, 24 strains of Neisseria gonorrhoeae isolated from the outpatients with gonorrhea were identified by using the Opa genotyping and NG-MAST genotyping and the relationship between genotypes and phenotypes was studied. Twenty-four strains of Neisseria gonorrhoeae fell into 10 ST genotypes by NG-MAST genotyping, whereas these strains were classified into 12 OT Opa genotypes by Opa genotyping. A new epidemic strain of ST genotype (217-86% homologisation 178) in China was identified. It is concluded that genotypes of each pair of strains from a pair of patient/ sex partner besides 45/46 are the same, indicating that contagious infection take place between patient and the sex partner. Opa genotyping was more effective than NG-MAST genotyping in identifying the genomic species of Neisseria gonorrhoeae. ST genotype could be further classified into different Opa-types.

A multicenter intervention to prevent catheter-associated bloodstream infections

BACKGROUND

Education-based interventions can reduce the incidence of catheter-associated bloodstream infection. The generalizability of findings from single-center studies is limited.

OBJECTIVE

To assess the effect of a multicenter intervention to prevent catheter-associated bloodstream infections.

DESIGN

An observational study with a planned intervention.

SETTING

Twelve intensive care units and 1 bone marrow transplantation unit at 6 academic medical centers.

PATIENTS

Patients admitted during the study period.

INTERVENTION

Updates of written policies, distribution of a 9-page self-study module with accompanying pretest and posttest, didactic lectures, and incorporation into practice of evidence-based guidelines regarding central venous catheter (CVC) insertion and care.

MEASUREMENTS

Standard data collection tools and definitions were used to measure the process of care (ie, the proportion of nontunneled catheters inserted into the femoral vein and the condition of the CVC insertion site dressing for both tunneled and nontunneled catheters) and the incidence of catheter-associated bloodstream infection.

RESULTS

Between the preintervention period and the postintervention period, the percentage of CVCs inserted into the femoral vein decreased from 12.9% to 9.4% (relative ratio, 0.73; 95% confidence interval [CI], 0.61-0.88); the total proportion of catheter insertion site dressings properly dated increased from 26.6% to 34.4% (relative ratio, 1.29; 95% CI, 1.17-1.42), and the overall rate of catheter-associated bloodstream infections decreased from 11.2 to 8.9 infections per 1,000 catheter-days (relative rate, 0.79; 95% CI, 0.67-0.93). The effect of the intervention varied among individual units.

CONCLUSIONS

An education-based intervention that uses evidence-based practices can be successfully implemented in a diverse group of medical and surgical units and reduce catheter-associated bloodstream infection rates.

Persistent bacteremia and severe thrombocytopenia caused by coagulase-negative Staphylococcus in a neonatal intensive care unit

OBJECTIVE

Coagulase-negative Staphylococcus (CoNS) is the most frequent cause of late-onset sepsis in NICUs, but mortality is rare and morbidity is unusual. We report a new syndrome of CoNS sepsis characterized by significant morbidity and persistent bacteremia despite aggressive antibiotic therapy and no identified focus of infection.

METHODS

We conducted a retrospective review of infants in the NICU with CoNS bacteremia between 2000 and 2002. Statistical analysis included an initial exploratory analysis followed by logistic regression. Microbiological identification of all isolates and molecular typing were performed.

RESULTS

Thirty-one neonates with persistent CoNS bacteremia were compared with 60 randomly selected neonates from a group of 140 with nonpersistent CoNS bacteremia. The clinical manifestations at presentation, gestational ages, and birth weights were similar in the 2 groups. Thrombocytopenia was present in 26 (84%) neonates with persistent CoNS bacteremia but only in 8 (13%) neonates in the nonpersistent group. Central venous catheterization increased the risk for persistent CoNS bacteremia, but 42% of the persistent group was never catheterized. Staphylococcus epidermidis was the most common isolate in both groups. Molecular typing failed to identify a predominant clone.

CONCLUSIONS

The syndrome of persistent CoNS septicemia is remarkable for thrombocytopenia and persistence in the absence of central venous catheterization. Clinical manifestations at presentation and demographic characteristics did not discriminate between the persistent and nonpersistent groups. We did not identify the emergence of a particularly virulent clone, but it is possible that some strains of CoNS have acquired the capacity to persist under different conditions.

RAPD for the typing of coagulase-negative staphylococci implicated in catheter-related bloodstream infection

OBJECTIVES

A rapid random amplification of polymorphic DNA (RAPD) technique was developed to distinguish between strains of coagulase-negative staphylococci (CoNS) involved in central venous catheter (CVC)-related bloodstream infection. Its performance was compared with that of pulsed-field gel electrophoresis (PFGE).

METHODS

Patients at the University Hospital Birmingham NHS Foundation Trust, U.K. who underwent stem cell transplantation and were diagnosed with CVC-related bloodstream infection due to CoNS whilst on the bone marrow transplant unit were studied. Isolates of CoNS were genotyped by PFGE and RAPD, the latter employing a single primer and a simple DNA extraction method.

RESULTS

Both RAPD and PFGE were highly discriminatory (Simpson's diversity index, 0.96 and 0.99, respectively). Within the 49 isolates obtained from blood cultures of 33 patients, 20 distinct strains were identified by PFGE and 25 by RAPD. Of the 25 strains identified by RAPD, nine clusters of CoNS contained isolates from multiple patients, suggesting limited nosocomial spread. However, there was no significant association between time of inpatient stay and infection due to any particular strain.

CONCLUSION

The RAPD technique presented allows CoNS strains to be genotyped with high discrimination within 4h, facilitating real-time epidemiological investigations. In this study, no single strain of CoNS was associated with a significant number of CVC-related bloodstream infections.

An educational intervention to prevent catheter-associated bloodstream infections in a nonteaching, community medical center

OBJECTIVE

To evaluate the effectiveness of an evidence-based intervention to prevent catheter-associated bloodstream infections among intensive care unit patients at a nonteaching, community hospital.

DESIGN

Nonrandomized pre/post observational trial.

SETTING

Two intensive care units at Missouri Baptist Medical Center, Saint Louis, MO.

PARTICIPANTS

Nurses and critical care physicians.

INTERVENTION

A ten-page, self-study module on the prevention of catheter-associated bloodstream infections, lectures, and posters given between July and September 1999.

MEASUREMENTS

The incidence of nosocomial catheter-associated bloodstream infection and patient demographics were measured for patients admitted between March 1998 and July 2000.

MAIN RESULTS

Thirty cases of catheter-associated bloodstream infections during 6110 catheter-days were noted in the preintervention period (4.9 cases/1000 catheter-days) vs. 11 cases during the 5210 catheter-days in the postintervention period (2.1 cases/1000 catheter-days). The relative risk for catheter-associated infection in the postintervention period was 0.43 (95% confidence interval, 0.22-0.84). Among catheterized patients, Acute Physiology and Chronic Health Evaluation II score (25.2 preintervention vs. 25.1 postintervention; p =.86), hemodialysis (91 of 647 [14%] patients vs. 69 of 541 [13%]; p =.70), and the mean number of catheter days per patient (9.1 vs. 9.6 days; p =.46) did not differ between the pre- and postintervention periods.

CONCLUSIONS

A focused, educational intervention among nurses and physicians in a nonteaching community hospital resulted in a significant, sustained reduction in the incidence of catheter-associated bloodstream infection.

Molecular epidemiology of coagulase-negative staphylococcal bacteraemia in a newborn intensive care unit

We isolated 55 coagulase-negative staphylococci (CoNS) over two separate 12-month periods (26 in 1993 and 29 in 1996) from the blood of neonates in a neonatal intensive case unit (NICU) in Melbourne, Australia and compared them by pulse-field gel electrophoresis profile (PFGE), random amplification of polymorphic DNA (RAPD) and antibiogram. The most common species were Staphylococcus epidermidis, S. haemolyticus and S. warneri. The majority of such isolates were resistant to penicillin and to either or both of methicillin and gentamicin. During 1993, there was an increase in the number of CoNS bloodstream infections compared with previous years. S. epidermidis was the most common isolate, with 88% assessed as clinically relevant. Using the three typing systems, we identified one likely epidemic clone of S. epidermidis, the isolates of which were resistant to penicillin, gentamicin and erythromycin and possessed the mecA gene. There was complete correlation between the detection of mecA and the phenotypic expression of resistance when zone diameters in the disc diffusion assay were interpreted according to the latest NCCLS guidelines (1999). Profiles of the remaining 1993 isolates were generally heterogeneous, suggesting independent acquisition with some evidence of cross-infection. The predominant bloodstream isolates in 1996 were heterogeneous multi-resistant strains of S. epidermidis, S. haemolyticus and S. warneri, about half of which were assessed as clinically relevant. These data support the view that CoNS are significant nosocomial pathogens in NICU and that resistant clones may be transmitted between babies. Molecular epidemiological tools are helpful for understanding transmission patterns and sources of infection, and are useful for measuring outcomes of intervention strategies implemented to reduce nosocomial CoNS sepsis. PFGE was found to be more discriminatory than RAPD, but the latter provides results in a more timely manner.

Prevalence of molecular types and mecA gene carriage of coagulase-negative Staphylococci in a neonatal intensive care unit: relation to nosocomial septicemia

Molecular typing of isolates revealed that neonatal coagulase-negative staphylococcal (CONS) septicemia is most frequently caused by predominant, antibiotic-resistant CONS types, which are widely distributed among both neonates and staff of the neonatal unit, suggesting cross-contamination. Therefore, infection control measures may be valuable in the prevention of this common nosocomial septicemia.

Molecular typing of coagulase-negative staphylococci from blood cultures does not correlate with clinical criteria for true bacteremia

PURPOSE

Determining whether a blood culture that contains coagulase-negative staphylococci represents bacteremia or contamination is a clinical dilemma. We compared molecular-typing results of coagulase-negative staphylococcal blood culture isolates with clinical criteria for true bacteremia.

SUBJECTS AND METHODS

Pulsed-field gel electrophoresis and arbitrary primed polymerase chain reaction (PCR) were used to determine whether patients with two or more blood cultures with coagulase-negative staphylococcal isolates had the same strain of organism in each culture (same strain bacteremia). We evaluated three different clinical criteria for bacteremia: whether the patient received more than 4 days of antibiotics, whether there was an explicit note in the medical chart in which the physician diagnosed a true bacteremia, and the Centers for Disease Control surveillance criteria for primary bloodstream infection. Agreement between same-strain bacteremia and each definition was examined, based on the assumption that most true infections should be the result of a single strain.

RESULTS

The study sample consisted of 42 patients and 106 isolates. Nineteen of the 42 bacteremias (45%) were the same strain. Classification of bacteremias as same-strain correlated poorly with all three clinical assessments (range of percent agreement, 50% to 57%; range of kappa statistic, 0.01 to 0.15). There were both false-positive and false-negative errors. Patients with three or more positive blood cultures were more likely to have same-strain bacteremia than those with only two positive cultures [11 of 15 (73%) vs 8 of 27 (30%), P = 0.006]. Pulsed-field gel electrophoresis was more discriminating than arbitrary primed PCR (percent agreement, 83%; kappa, 0.67).

CONCLUSION

Molecular typing correlated poorly with clinical criteria for true bacteremia, suggesting either that true bacteremias are frequently the result of multiple strains or that the commonly used clinical criteria are not accurate for distinguishing contamination from true bacteremia. Vancomycin treatment of clinically defined coagulase-negative staphylococcal bacteremia may frequently be unnecessary.

Molecular tracking of coagulase-negative staphylococcal isolates from catheter-related infections

Three molecular typing methods (pulsed-field electrophoresis, localization of the mecA gene, and probing the vicinity of mec) have been used for the characterization of 40 catheter-related isolates of coagulase-negative staphylococci (CNS) in 14 patients admitted to the same hospital. The 40 isolates yielded 14 different SmaI banding patterns and corresponding unique localizations of mecA, each associated with a unique ClaI mecA polymorph. In 6 of the 14 patients the contaminated skin at the catheter entry site was the source of 4 local infections and 2 cases of bacteremia. A contaminated hub was the origin of 2 local infections and 4 cases of bacteremia in 6 more patients. The remaining 2 patients had positive cultures from both skin and catheter hub. In each bacteremic patient, the CNS recovered from catheter-related sites (tip, skin, and/or hub) and the CNS recovered from blood were identical, but each of these matching isolates was unique to the particular patients, indicating a low rate of cross-infection from patient to patient. Although classical methods for typing CNS (e.g., biotype and antibiotype) are readily available for most hospital laboratories, they have limitations concerning reproducibility and discriminatory power. Molecular epidemiologic techniques can provide powerful support to traditional techniques in determining the etiologic role of CNS in the disease process.

Molecular epidemiology of antibiotic resistance

Molecular typing methods based on the analysis of the genetic structure of bacteria, are used to address many different problems such as the study of genomic organisation and evolution, the identification of patterns of infection, the identification of sources of transmission, the epidemiological surveillance of infectious diseases and for investigations into outbreaks. Of particular interest is the application of these techniques for acquiring information on the spread of micro-organisms that have become resistant to many clinically important antibiotics. The emergence of antibiotic resistance is one of the most dangerous phenomena of the last 20 years and knowledge of the mechanisms of resistant-gene exchange means fully understanding their spread into all environments. Studies on the molecular epidemiology of antibiotic-resistance in micro-organisms should make it easier to distinguish clonality with respect to horizontal transfer of the determinants of resistance.

Characterization of coagulase-negative staphylococci by primer-specific polymerase chain reaction and ribotyping

OBJECTIVE: To analyze, by primer-specific polymerase chain reaction (PCR) and ribotyping, coagulase-negative staphylococci (CNS). METHODS: Forty-five clinical isolates of CNS were identified by the API ID32 STAPH system and ribotyping. Additionally, primer-specific PCR was evaluated for identification of clinical strains of Staphylococcus epidermidis. RESULTS: Forty-five isolates of CNS from neonates with nosocomial bacteremia were studied. The results of the S. epidermidis-specific PCR were compared with those obtained using ribotyping and the API ID32 STAPH system. Excellent congruence was found between primer-specific PCR and ribotyping. Primer-specific PCR proved to be a fast and reliable method for the identification of S. epidermidis strains. According to the primer-specific PCR and ribotyping analysis, a few CNS isolates were found to be incorrectly identified by the API ID32 STAPH system. CONCLUSIONS: Primer-specific PCR is a fast and reliable method for the identification of S. epidermidis. Primer-specific PCR in combination with ribotyping is a promising approach for studying the epidemiology of S. epidermidis and other CNS species in hospital.

An epidemiological study of blood culture isolates of coagulase-negative staphylococci demonstrating hospital-acquired infection

We applied pulsed-field gel electrophoresis (PFGE) after SmaI digestion and random amplification of polymorphic DNA (RAPD) analysis with nine oligonucleotide primers to 146 blood culture isolates of Staphylococcus epidermidis and 25 blood culture isolates of Staphylococcus haemolyticus. These were obtained over a 12-month period from patients on the neonatal and hematology units of the Central Manchester Health Care Trust. PFGE demonstrated two clusters of isolates of S. epidermidis (type A and type B) on the neonatal ward and a single cluster (type C) on the hematology unit. Type A was represented by 10 indistinguishable isolates from nine patients, type B was represented by 20 isolates from 14 patients, and type C was represented by 26 isolates from 10 patients. Type A isolates were resistant to chloramphenicol and type C isolates were resistant to ciprofloxacin, mirroring current antibiotic usage. There was no evidence of cross infection due to S. haemolyticus. RAPD analysis, on the basis of a single band difference, produced 58 types of S. epidermidis and 12 types of S. haemolyticus with primer 8 (ATG TAA GCT CCT GGG GAT TCA C; 5' to 3') and 54 types of S. epidermidis and 10 types of S. haemolyticus with primer 9 (AAG TAA GTG ACT GGG GTG AGC G; 5' to 3'). Combining the results confirmed cross infection. Types A, B, and C were concurrently isolated from the hands of the staff of the appropriate unit. Partial control was achieved by withdrawing ciprofloxacin use in the case of the hematology unit and improving hand hygiene in both units.

Change in nasopharyngeal carriage of Streptococcus pneumoniae resulting from antibiotic therapy for acute otitis media in children

BACKGROUND

Acute otitis media is the leading reason for antibiotic prescriptions in childhood. The increase in antibiotic resistance of Streptococcus pneumoniae is generally attributed to the extensive use of antibiotics and the selective pressure on the bacterial strains of the nasopharyngeal flora.

OBJECTIVE

To evaluate the change in nasopharyngeal carriage of S. pneumoniae during antibiotic therapy prescribed for acute otitis media.

METHODS

Between October, 1993, and March, 1994, we conducted a clinical trial comparing cefpodoxime-proxetil and amoxicillin-clavulanate in acute otitis media. From 364 children, 4 months to 4.5 years old, a nasopharyngeal sample was obtained before and after treatment. Antibiotic susceptibility was established by determining minimal inhibitory concentrations by the agar dilution method. Serotype and randomly amplified polymorphic DNA analysis were used to compare pre- and posttreatment S. pneumoniae strains.

RESULTS

The risk for a child to carry penicillin-resistant S. pneumoniae (MIC > or = 0.125 mg/l) did not increase after antibiotic treatment: 84 of 364 (23.1%) before, 70 of 364 (19.2%) after. There was a significant decrease of penicillin-susceptible S. pneumoniae carriage, 117 of 364 (32.1%) before treatment compared with 24 of 364 (6.6%) (P = 0.0001) after treatment. However, among the children carrying S. pneumoniae at the end of the treatment there was an increase in the percentage of penicillin-resistant pneumococci: 84 of 201 (41.8%) before treatment and 70 of 94 (74.5%) after treatment. Among the 94 children carrying S. pneumoniae at the end of the treatment, 22 did not harbor pneumococcus before, 16 carried another genotypically different serotype and 56 harbored the same serotype. Among these 56 children 2 patients harbored strains that had increased MICs for the tested beta-lactam antibiotics. The randomly amplified polymorphic DNA analysis showed that in one case, the strains were genetically different.

CONCLUSIONS

These data illustrate that antibiotic therapy did not increase the rate at which children carried penicillin-resistant S. pneumoniae, but there was an increase in the rate of resistance among the children carrying pneumococci at the end of the treatment, mainly as a result of reduction of susceptible strains.

Current laboratory techniques in the diagnosis of catheter-related infections

The unspecificity of the clinical manifestations of catheter-related infections (CRIs) makes laboratory confirmation necessary, and many diagnostic techniques have been developed. Semiquantitative culture of catheter tips has been accepted by most laboratories for its simplicity and is currently the reference technique. It discriminates between catheters producing infection (when > or = 15 colony forming units grow on the culture) and insignificant colonization. Nonquantitative methods improve the sensitivity of diagnosis of CRI but are less specific. Quantitative methods improve the specificity and can identify and quantify colonization of both the internal and external surfaces of the catheter; however, these are time-consuming techniques. The high rate of unnecessary catheter removal has promoted interest in in situ staining methods such as gram staining of the skin entry site and hub. These methods are simple to perform and have shown a high negative predictive value. Quantitative blood culture methods allow the diagnosis of CRI, but their sensitivity decreases in the absence of associated bacteremia. Finally, the introduction of molecular techniques has helped to explain the pathogenesis of CRI and could help to improve the management of nosocomial CRI.

Molecular DNA analysis for differentiation of persistence or relapse from recurrence in treatment failure of Streptococcus pyogenes pharyngitis

In the evaluation of treatment failure in group A streptococcal pharyngitis, it is essential to distinguish persistence or relapse with homologous streptococcal strains from the acquisition of new, unrelated strains. Randomly amplified polymorphic DNA analysis and restriction fragment length polymorphism analysis of total DNA were used as epidemiological tools to compare 122 pre- and post-treatment Streptococcus pyogenes isolates obtained from 61 patients. The results obtained by molecular typing showed that bacteriological failures were due to the original strains in 43 cases (70%) and to new strains in 18 cases (30%). In the present study, restriction fragment length polymorphism analysis of total DNA appeared to be more discriminative than randomly amplified polymorphic DNA analysis. Thus, molecular analysis of DNA is an effective way to distinguish recurrence from persistence or relapse and will be useful in assessing the efficacy of new antibiotic treatments.

Nosocomial CDC group IV c-2 bacteremia: epidemiological investigation by randomly amplified polymorphic DNA analysis

The CDC group IV c-2 bacterium is a gram-negative bacillus rarely isolated from clinical specimens. This organism caused catheter-related bacteremia in five immunocompromised children hospitalized in two distinct wards of our institution between November 1993 and October 1994. Three patients recovered on empiric antibacterial chemotherapy combining ceftazidime and amikacin, and a fourth patient required imipenem instead of ceftazidime. The fifth patient recovered without treatment. Catheter removal was never necessary. The randomly amplified polymorphic DNA technique with three different primers was applied to nine isolates recovered by culturing blood from the five children and showed that all of the patients harbored isolates of the same genotype. The source of the outbreak could not be determined.

Staphylococcus pasteuri-specific oligonucleotide probes derived from a random amplified DNA fragment

A rapid polymerase chain reaction method was developed to differentiate Staphylococcus pasteuri from other staphylococcal species, especially the phenotypically similar S. warneri. The oligonucleotide probes used as primers were designed from the sequence of a S. pasteuri random amplified polymorphic DNA fragment.