Increase of Enterobacter in neonatal sepsis: a twenty-two-year study

Distribution and diversity of type VI secretion system clusters in Enterobacter bugandensis and Enterobacter cloacae

Gram-negative bacteria use type VI secretion systems (T6SSs) to antagonize neighbouring cells. Although primarily involved in bacterial competition, the T6SS is also implicated in pathogenesis, biofilm formation and ion scavenging. Enterobacter species belong to the ESKAPE pathogens, and while their antibiotic resistance has been well studied, less is known about their pathogenesis. Here, we investigated the distribution and diversity of T6SS components in isolates of two clinically relevant Enterobacter species, E. cloacae and E. bugandensis. T6SS clusters are grouped into four types (T6SSi-T6SSiv), of which type i can be further divided into six subtypes (i1, i2, i3, i4a, i4b, i5). Analysis of a curated dataset of 31 strains demonstrated that most of them encode T6SS clusters belonging to the T6SSi type. All T6SS-positive strains possessed a conserved i3 cluster, and many harboured one or two additional i2 clusters. These clusters were less conserved, and some strains displayed evidence of deletion. We focused on a pathogenic E. bugandensis clinical isolate for comprehensive in silico effector prediction, with comparative analyses across the 31 isolates. Several new effector candidates were identified, including an evolved VgrG with a metallopeptidase domain and a Tse6-like protein. Additional effectors included an anti-eukaryotic catalase (KatN), M23 peptidase, PAAR and VgrG proteins. Our findings highlight the diversity of Enterobacter T6SSs and reveal new putative effectors that may be important for the interaction of these species with neighbouring cells and their environment.

Principal Amalgamation Analysis for Microbiome Data

In recent years microbiome studies have become increasingly prevalent and large-scale. Through high-throughput sequencing technologies and well-established analytical pipelines, relative abundance data of operational taxonomic units and their associated taxonomic structures are routinely produced. Since such data can be extremely sparse and high dimensional, there is often a genuine need for dimension reduction to facilitate data visualization and downstream statistical analysis. We propose Principal Amalgamation Analysis (PAA), a novel amalgamation-based and taxonomy-guided dimension reduction paradigm for microbiome data. Our approach aims to aggregate the compositions into a smaller number of principal compositions, guided by the available taxonomic structure, by minimizing a properly measured loss of information. The choice of the loss function is flexible and can be based on familiar diversity indices for preserving either within-sample or between-sample diversity in the data. To enable scalable computation, we develop a hierarchical PAA algorithm to trace the entire trajectory of successive simple amalgamations. Visualization tools including dendrogram, scree plot, and ordination plot are developed. The effectiveness of PAA is demonstrated using gut microbiome data from a preterm infant study and an HIV infection study.

Fourier-Transform Infrared (FTIR) Spectroscopy for Typing of Clinical Enterobacter cloacae Complex Isolates

Members of the Enterobacter (E.) cloacae complex have emerged as important pathogens frequently encountered in nosocomial infections. Several outbreaks with E. cloacae complex have been reported in recent years, especially in neonatal units. Fast and reliable strain typing methods are crucial for real-time surveillance and outbreak analysis to detect pathogen reservoirs and transmission routes. The aim of this study was to evaluate the performance of Fourier-transform infrared (FTIR) spectroscopy as a fast method for typing of clinical E. cloacae complex isolates, when whole genome sequencing (WGS) analysis was used as reference. First, the technique was used retrospectively on 24 first isolates of E. cloacae complex strains from neonatal patients and showed good concordance with SNP-based clustering [adjusted rand index (ARI) = 0.818] and with the sequence type (ST) (ARI = 0.801). 29 consecutive isolates from the same patients were shown by WGS analysis to almost always belong to the same SNP cluster as the first isolates, which was only inconsistently recognized by FTIR spectroscopy. Training of an artificial neural network (ANN) with all FTIR spectra from sequenced strains markedly improved the recognition of related and unrelated isolate spectra. In a second step, FTIR spectroscopy was applied on 14 strains during an outbreak with E. cloacae complex and provided fast typing results that were confirmed by WGS analysis. In conclusion, FTIR spectroscopy is a promising tool for strain typing of clinical E. cloacae complex strains. Discriminatory power can be improved by implementing an ANN for spectrum analysis. Due to its low costs and fast turnaround times, the method presents a valuable tool for real-time surveillance as well as outbreak analysis.

Enterobacter bugandensis: a novel enterobacterial species associated with severe clinical infection

Nosocomial pathogens can cause life-threatening infections in neonates and immunocompromised patients. E. bugandensis (EB-247) is a recently described species of Enterobacter, associated with neonatal sepsis. Here we demonstrate that the extended spectrum ß-lactam (ESBL) producing isolate EB-247 is highly virulent in both Galleria mellonella and mouse models of infection. Infection studies in a streptomycin-treated mouse model showed that EB-247 is as efficient as Salmonella Typhimurium in inducing systemic infection and release of proinflammatory cytokines. Sequencing and analysis of the complete genome and plasmid revealed that virulence properties are associated with the chromosome, while antibiotic-resistance genes are exclusively present on a 299 kb IncHI plasmid. EB-247 grew in high concentrations of human serum indicating septicemic potential. Using whole genome-based transcriptome analysis we found 7% of the genome was mobilized for growth in serum. Upregulated genes include those involved in the iron uptake and storage as well as metabolism. The lasso peptide microcin J25 (MccJ25), an inhibitor of iron-uptake and RNA polymerase activity, inhibited EB-247 growth. Our studies indicate that Enterobacter bugandensis is a highly pathogenic species of the genus Enterobacter. Further studies on the colonization and virulence potential of E. bugandensis and its association with septicemic infection is now warranted.

Neonatal gram-negative bacillary late-onset sepsis: A case-control-control study on a prospectively collected database of 5,233 admissions

BACKGROUND

Gram-negative bacillary (GNB) bloodstream infections account for 20%-30% of neonatal late-onset sepsis (LOS). We aimed to identify the incidence, clinical characteristics, and risk factors for adverse outcomes in neonates with GNB LOS.

METHODS

All patients with GNB LOS admitted to the neonatal intensive care units (NICUs) of a university-affiliated teaching hospital in Taiwan from January 1, 2004-December 31, 2011, were enrolled. A case-control-control study was performed to evaluate risk factors for acquisition of neonatal GNB LOS.

RESULTS

Of the 5,010 neonates, 290 (5.8%) had a total of 346 episodes of GNB LOS (36.7% of total LOS), with an incidence rate of 13.6 per 10,000 neonate hospital days. The overall mortality rate was 17.6% (51/290), and the sepsis attributable mortality rate was 9.8% (34/346 episodes). After multivariate logistic regression analysis, neonates with prolonged use of total parenteral nutrition (adjusted odds ratio [OR] = 1.53; 95% confidence interval [CI], 1.02-2.29; P = .041) were independently associated with acquisition of GNB LOS. The independent predictors of in-hospital mortality were Pseudomonas aeruginosa etiology (OR = 11.45; 95% CI, 2.83-46.24) and underlying secondary pulmonary hypertension (OR = 18.02; 95% CI, 3.28-98.89), renal disease (OR = 17.16; 95% CI, 2.96-99.38), and neuromuscular comorbidities (OR = 2.72; 95% CI, 1.06-7.00).

CONCLUSION

Given the higher illness severity and sepsis-attributable mortality rate of neonatal GNB LOS in the NICU, strategies to reduce the incidence need to be addressed urgently.

Clinical analysis of Enterobacter bacteremia in pediatric patients: a 10-year study

BACKGROUND

Enterobacter species has emerged as an important pathogen of nosocomial bacteremia. The purpose of this study is to review the clinical characteristics of bacteremia in pediatric patients.

MATERIALS AND METHODS

We reviewed retrospectively the medical records of patients (under the age of 18 years) having Enterobacter bacteremia who were treated at Taipei the Veterans General Hospital from January 2001 to June 2011.

RESULTS

In total, 853 positive blood cultures were obtained from 620 patients during the study period. Among them, 96 episodes of Enterobacter bacteremia were found in 83 patients, accounting for 11.3% of all bacteremia. Eighty-two cases (98.8%) were nosocomial infections. Most of the cases were neonates (62 cases, 74.7%) and premature infants (51 cases, 61.5%). The common sources of bacteremia were the respiratory tract (53.0%), followed by intravascular catheter (10.8%), multiple sources (10.8%), and the gastrointestinal tract (8.4%). The overall case fatality rate was 18.1%, with the highest rate being reported among premature infants. The factors responsible for the deaths were leukocytosis and a higher median number of underlying diseases.

CONCLUSION

Based on the findings of the present study, it can be concluded that Enterobacter species are probably an important pathogen of nosocomial bacteremia in premature neonates. The number of underlying diseases should be considered a major factor influencing the prognosis.

Subtractive hybridization yields a silver resistance determinant unique to nosocomial pathogens in the Enterobacter cloacae complex

The heterogeneity and the increasing clinical importance of the Enterobacter cloacae complex have often been discussed. However, little is known about molecular factors causing pathogenicity within this nomenspecies. Here, we analyzed the genetic differences between an avirulent plant isolate and a pathogenic strain causing an outbreak with septicemia in three patients. We identified an IncHI-2 plasmid as a major difference between these two strains. Besides resistance to several antibiotics, this plasmid encoded a silver resistance determinant. We further showed that this sil determinant was present not only in the analyzed outbreak strain but also in the vast majority of clinical isolates of the E. cloacae complex, predominantly in (sub)species that frequently cause nosocomial infections. The identified sil determinant was highly conserved within the E. cloacae complex and mediated resistance to up to 600 μM silver nitrate. As silver is often used as a disinfectant and treatment for burn wounds, we present here an important fitness factor within the clinically most prevalent subspecies of the E. cloacae complex. This provides a possible explanation for their unequal involvement in nosocomial and especially burn wound infections.

High load of multi-drug resistant nosocomial neonatal pathogens carried by cockroaches in a neonatal intensive care unit at Tikur Anbessa specialized hospital, Addis Ababa, Ethiopia

BACKGROUND

Cockroaches have been described as potential vectors for various pathogens for decades; although studies from neonatal intensive care units are scarce. This study assessed the vector potential of cockroaches (identified as Blatella germanica) in a neonatal intensive care unit setup in Tikur Anbessa Hospital, Addis Ababa, Ethiopia.

METHODS

A total of 400 Blatella germanica roaches were aseptically collected for five consecutive months. Standard laboratory procedures were used to process the samples.

RESULTS

From the external and gut homogenates, Klebsiella oxytoca, Klebsiella pneumoniae, Citrobacter spp. Enterobacter cloacae, Citrobacter diversus, Pseudomonas aeruginosa, Providencia rettgeri, Klebsiella ozaenae, Enterobacter aeruginosa, Salmonella C1, Non Group A streptococcus, Staphylococcus aureus, Escherichia coli, Acinetobacter spp. and Shigella flexneri were isolated. Multi-drug resistance was seen in all organisms. Resistance to up to all the 12 antimicrobials tested was observed in different pathogens.

CONCLUSION

Cockroaches could play a vector role for nosocomial infections in a neonatal intensive care unit and environmental control measures of these vectors is required to reduce the risk of infection. A high level of drug resistance pattern of the isolated pathogens was demonstrated.

International perspective on early-onset neonatal sepsis

Infections are a major cause of neonatal death in developing countries. High-quality information on the burden of early-onset neonatal sepsis and sepsis-related deaths is limited in most of these settings. Simple preventive and treatment strategies have the potential to save many newborns from sepsis-related death. Implementation of public health programs targeting newborn health will assist attainment of Millennium Development Goals of reduction in child mortality.

Late-onset Enterobacter cloacae sepsis in very-low-birth-weight neonates: experience in a medical center

OBJECTIVE

The objective of this study was to review the early clinical profiles and outcomes of very-low-birth-weight (VLBW) neonates with late-onset sepsis caused by Enterobacter cloacae.

METHODS

We reviewed the medical records of VLBW neonates whose blood and/or cerebral spinal fluid yielded E. cloacae after 3 days of hospitalization in our neonatal intensive care unit.

RESULTS

From January 1997 to December 2006, a total of 29 episodes of E. cloacae infection occurred in 28 VLBW neonates. The onset of E. cloacae infection ranged from 4 to 70 days (27.4 +/- 9.6) days after birth. The most common symptoms and signs of sepsis were desaturation (58.6%), tachycardia (58.6%), apnea (55.2%), unstable body temperature (48.3%), and decreased activity (44.8%). The infected neonates had an average of four kinds of symptoms in each sepsis episode. The most common laboratory findings in VLBW neonates with E. cloacae sepsis were thrombocytopenia (65.5%), C-reactive protein > or = 1 mg/dL (55.2%), band-form neutrophils > or = 5% (41.4%), and leucopoenia (20.7%). Empirical intravenous antibiotic therapy comprising piperacillin (or piperacillin and tazobactam) and gentamicin (or amikacin) was successful in the early treatment of 24 episodes of E. cloacae sepsis in 25 patients. Three neonates (10.7%) died due to E. cloacae sepsis. Four neonates (14.3%) developed E. cloacae meningitis, and two of them developed brain abscesses.

CONCLUSIONS

E. cloacae infection in VLBW neonates usually presents with nonspecific symptoms and signs. Early recognition of sepsis and empirical combination of piperacillin (or piperacillin and tazobactam) and gentamicin (or amikacin) may be useful for treatment of sepsis caused by this highly virulent pathogen.

Characterization of an extended-spectrum beta-lactamase Enterobacter hormaechei nosocomial outbreak, and other Enterobacter hormaechei misidentified as Cronobacter (Enterobacter) sakazakii

Enterobacter hormaechei is a Gram-negative bacterium within the Enterobacter cloacae complex, and has been shown to be of clinical significance by causing nosocomial infections, including sepsis. Ent. hormaechei is spread via horizontal transfer and is often associated with extended-spectrum beta-lactamase production, which increases the challenges associated with treatment by limiting therapeutic options. This report considers 10 strains of Ent. hormaechei (identified by 16S rDNA sequencing) that had originally been identified by phenotyping as Cronobacter (Enterobacter) sakazakii. Seven strains were from different neonates during a nosocomial outbreak in a California hospital. PFGE analysis revealed a clonal relationship among six of the seven isolates and therefore a previously unrecognized Ent. hormaechei outbreak had occurred over a three-month period. Antibiotic-resistance profiles were determined and extended-spectrum beta-lactamase activity was detected. The association of the organism with powdered infant formula, neonatal hosts and Cr. sakazakii suggested that the virulence of these organisms may be similar. Virulence traits were tested and all strains were shown to invade both gut epithelial (Caco-2) and blood-brain barrier endothelial cells (rBCEC4), and to persist in macrophages (U937). Due to misidentification we suggest that Ent. hormaechei may be an under-reported cause of bacterial infection, especially in neonates. Also, its isolation from various sources, including powdered infant milk formula, makes it a cause for concern and merits further investigation.

Etiology of neonatal blood stream infections in Tbilisi, Republic of Georgia

BACKGROUND

Neonatal blood stream infections (BSI) are a major cause of morbidity and mortality in developing countries. It is crucial to continuously monitor the local epidemiology of neonatal BSI to detect any changes in patterns of infection and susceptibility to various antibiotics.

OBJECTIVES

To examine the etiology of BSI in two neonatal intensive care units (NICUs) in the Republic of Georgia, a resource-poor country, and to determine antibiotic susceptibility of the isolated organisms.

METHODS

A cross-sectional study of all septic infants was conducted in the NICUs of two pediatric hospitals in Tbilisi between September 2003 and September 2004.

RESULTS

A total of 200 infants with clinical signs of sepsis were admitted to two NICUs. Of these, 126 (63%) had confirmed bacteremia. The mortality rate was 34%. A total of 98 (78%) of 126 recovered isolates were Gram-negative organisms and 28 (22%) were Gram-positive. Klebsiella pneumoniae was the most common pathogen, accounting for 36 (29%) of 126 isolates, followed by Enterobacter cloacae accounting for 19 (15%) and Staphylococcus aureus accounting for 15 (12%). The Gram-negative organisms showed a high degree of resistance to commonly used antibiotics such as ampicillin and amoxicillin/clavulanate, and comparatively low resistance to amikacin, ciprofloxacin, carbapenems, and gentamicin; 40% of S. aureus isolates were methicillin-resistant (MRSA). In multivariate analysis only umbilical discharge was a significant risk factor for having a positive blood culture at admission to NICU (prevalence ratio = 2.25, 95% confidence interval 1.82-2.77).

CONCLUSIONS

Neonatal BSI was mainly caused by Gram-negative organisms, which are developing resistance to commonly used antibiotics. Understanding the local epidemiology of neonatal BSI can lead to the development of better medical practices, especially more appropriate choices for empiric antibiotic therapy, and may contribute to improvement of infection control practices.

Serious community-acquired neonatal infections in rural Southeast Asia (Bohol Island, Philippines)

OBJECTIVE

To determine the bacterial etiology, clinical presentation and risk factors for outcome of serious community-acquired infections in young infants.

STUDY DESIGN

Infants younger than 60 days, admitted for severe pneumonia or suspected sepsis/meningitis were prospectively evaluated using complete blood count, blood culture, chest radiograph, cerebrospinal fluid (CSF) culture in suspected meningitis. chi2 or Fisher's exact test and stepwise logistic regression were used for analysis.

RESULTS

Thirty-four of 767 enrolled infants had a positive blood or CSF culture. Gram-negative bacteria were more frequent than Gram positive: overall (P=0.004), in those below 7 days of age (P=0.002) and among home deliveries (P=0.012). Case fatality rates were higher among infants below 1 week old (OR 4.14, P<0.001), those with dense (OR 2.92, P<0.001) or diffuse radiographic infiltrates (OR 2.79, P=0.003).

CONCLUSIONS

Gram-negative enteric bacteria are the predominant causes of community-acquired infections in Filipino infants below 2 months old. Age below 7 days and radiographic pneumonia predicted death.

A comparison of neonatal Gram-negative rod and Gram-positive cocci meningitis

OBJECTIVE

Neonatal meningitis is an illness with potentially devastating consequences. Early identification of potential risk factors for Gram-negative rod (GNR) infections versus Gram-positive cocci (GPC) infection prior to obtaining final culture results is of value in order to appropriately guide expirical therapy. We sought to compare laboratory and clinical parameters of GNR and GPC meningitis in a cohort of term and premature infants.

STUDY DESIGN

We evaluated lumbar punctures from neonates cared for at 150 neonatal intensive care units managed by the Pediatrix Medical Group Inc. We compared cerebrospinal fluid (CSF) parameters (white blood cell count, red blood cell count, glucose, and protein), demographics, and outcomes between infants with GNR and GPC meningitis. CSF cultures positive with coagulase-negative staphylococci were excluded.

RESULTS

We identified 77 infants with GNR and 86 with GPC meningitis. There were no differences in gestational age, birth weight, infant sex, race, or rate of Caesarean section. GNR meningitis was more often diagnosed after the third postnatal day and was associated with higher white blood cell and red blood cell counts. GNR meningitis diagnosed in the first 3 days of life was associated with antepartum antibiotic exposure. No difference was noted in either CSF protein or glucose levels. After correcting for gestational age, there was no observed difference in mortality between infants infected with GNR or GPC.

CONCLUSION

Compared to GPC meningitis, GNR meningitis was associated with several aspects of the clinical history and laboratory findings including older age of presentation, antepartum exposure to antibiotics, and elevated CSF white blood cell and red blood cell counts.

Enterobacter sakazakii: a coliform of increased concern to infant health

The first cases of neonatal meningitis believed to have been caused by Enterobacter sakazakii were reported in 1961. Prompted by several subsequent outbreaks of E. sakazakii infections in neonates and an increasing number of neonates in intensive care units being fed rehydrated powdered infant formula, considered to be a source of the pathogen, public health authorities and researchers are exploring ways to eliminate the bacterium or control its growth in dry infant formula, processing environments and formula preparation areas in hospitals. Reviewed here are advances in taxonomy and classification of E. sakazakii, methods of detecting, isolating and typing the bacterium, antibiotic resistance, clinical etiology and pathogenicity. Outbreaks of E. sakazakii infections in neonates and adults are summarized. Reports on the presence of E. sakazakii in clinical settings, the environment and foods and food processing facilities are reviewed. Tolerance of the pathogen to environmental stresses, its behavior in powdered and rehydrated infant formulae and hazard analysis and risk management are discussed. Research needs are presented.

Early onset neonatal meningitis in Australia and New Zealand, 1992-2002

OBJECTIVES

To study the epidemiology of early onset neonatal bacterial meningitis (EONBM) in Australasia.

DESIGN

Prospective surveillance study, 1992-2002, in 20 neonatal units in Australia and New Zealand. EONBM was defined as meningitis occurring within 48 hours of delivery.

RESULTS

There were 852 babies with early onset sepsis, of whom 78 (9.2%) had EONBM. The incidence of early onset group B streptococcal meningitis fell significantly from a peak of 0.24/1000 live births in 1993 to 0.03/1000 in 2002 (p trend = 0.002). There was no significant change over time in the incidence of Escherichia coli meningitis. The rate of EONBM in very low birthweight babies was 1.09/1000 compared with the rate in all infants of 0.11/1000. The overall rate of EONBM was 0.41/1000 in 1992 and 0.06 in 2001, but this trend was not significant (p trend = 0.07). Case-fatality rates for EONBM did not change significantly with time. Birth weight <1500 g (odds ratio (OR) 7.2 (95% confidence interval (CI) 4.8 to 10.9)) and Gram negative bacillary meningitis (OR 3.3 (95% CI 2.2 to 4.9)) were significant risk factors for mortality. Sixty two percent of the 129 babies who died from early onset sepsis or suspected sepsis did not have a lumbar puncture performed.

CONCLUSION

The incidence of early onset group B streptococcal meningitis has fallen, probably because of maternal intrapartum antibiotic prophylaxis, without a corresponding change in E. coli meningitis. Gram negative bacillary meningitis still carries a worse prognosis than meningitis with a Gram positive organism.

Strategic use of antibiotics in the neonatal intensive care unit

Infection is one of the most common causes of infant morbidity and mortality in the neonatal intensive care unit, despite the availability of various therapeutic medical interventions, such as mechanical ventilation, that allow premature infants a better chance of survival. In fact, many of these therapeutic interventions violate the natural protective barriers for infection. Fortunately, maternal and neonatal risk factors have been identified for early- and late-onset sepsis and the prevalence of highly suspected pathogens for each type of infection influences the empiric selection of antibiotics. In many institutions, the common pathogens have developed resistance to antibiotics. In others, the predominance of pathogens has shifted. Both challenges may warrant modification of traditional antibiotic regimens. Continual monitoring of pathogen shifts within an individual neonatal intensive care unit and application of various antibiotic characteristics are key elements of strategic, safe, and effective use of antibiotics in this patient population. Development of a protocol incorporating infection control measures and guidelines for judicious use of antibiotics can minimize the threat of antibiotic resistance.

Antibiotic resistance: is the end of an era near?

Any attempt to shape the world and modify human personality in order to create a self-chosen pattern of life involves many unknown consequences. Human destiny is bound to remain a gamble, because at some unpredictable time and in some unforeseen manner, nature will strike back.

Identification of novel eubacteria from spent mushroom compost (SMC) waste by DNA sequence typing: ecological considerations of disposal on agricultural land

A small study was undertaken to examine the microbiological characteristics of spent mushroom compost (SMC), which is the major waste by-product of the mushroom industry and which is regularly disposed off by application to agricultural land. The primary aim of this study was to examine SMC for the presence of faecal bacterial pathogens, including Campylobacter spp., Salmonella spp. and Listeria monocytogenes. Secondly it was desirable to quantify bacterial and fungal populations within SMC, and also qualitatively identify the diversity of bacterial populations within SMC, through employment of rDNA PCR and direct sequencing techniques on the culturable microflora. Conventional microbiological analyses of SMC material (n=30) from six commercial operations in both Northern Ireland and the Republic of Ireland, failed to detect Salmonella spp, Listeria spp. or Campylobacter spp. in any of the SMC material examined. Total aerobic plate counts gave a mean count of log10 7.01 colony forming units (cfu) per gram SMC material (range: log10 6.53-7.52 cfu/g). Fungal counts gave a mean count of log(10) 4.57 cfu per gram SMC material (range: log10 3.93-4.98 cfu/g). From a total of greater than 50 colony picks, a total of 12 bacterial morphotypes were identified and were further examined by employment of partial 16S rRNA gene amplification and sequencing techniques, yielding several genera and species, including Bacillus licheniformis, Bacillus subtilis, Klebsiella/Enterobacter sp. Microbacterium sp. Paenibacillus lentimorbus, Pseudomonas mevalonii, Sphingobacterium multivorum and Stenotrophomonas sp. This is the first preliminary report on the microbial diversity of SMC waste and demonstrates the presence of several species that have not been previously described in SMC, in addition to two potentially novel species within the genera Microbacterium and Stenotrophomonas. It is thereby important to examine the ecological microbe-microbe and plant-microbe interactions that are occurring between the native bacterial soil flora and those added annually (theoretically estimated at approximately 10(18) cells) through the application of SMC. Such studies would be beneficial in helping to ascertain the ecological consequences involved in the disposal of SMC waste on agricultural land.

Neonatal meningitis

Twelve years ago an annotation was published in Archives of Disease in Childhood regarding the antibiotic treatment of suspected neonatal meningitis. The authors recommended the use of cephalosporins rather than chloramphenicol and advocated intraventricular aminoglycoside treatment in selected cases. They noted the absence of clinical trials with third generation cephalosporins that showed an improvement in mortality or neurological outcome.

Molecular typing strategies

Nosocomial infections among infants in neonatal intensive care units are an increasing cause of morbidity and mortality. Efforts to rapidly detect, contain and ultimately prevent cross-transmission of these pathogens require constant vigilance by members of the epidemiology team. A vital component of an epidemiological evaluation is the ability to assess the interrelatedness of clinical isolates. This review focuses on the basic principles, strengths and weaknesses of some of the most commonly used molecular-based procedures, which determine clonal identity of outbreak strains in neonatal settings. Published evidence for the cogent selection of the method best suited for studying a particular organism and technological advances that await the new science of Molecular Epidemiology are also presented. The appropriate use of molecular typing technologies should enable reliable tracking of epidemic clones and thereby enhance the effectiveness of infection control strategies.

Change in epidemiology of health care-associated infections in a neonatal intensive care unit

BACKGROUND

Gram-negative rods (GNR) and species are important causes of health care-associated infections in neonatal intensive care units (NICUs). In prior reports, Gram-positive cocci (GPC) have been identified as the most common pathogens causing nosocomial infections in NICUs.

OBJECTIVE

To describe the epidemiology of health care-associated infections in a Level III NICU at a free-standing children's hospital.

METHODS

All health care-associated infections in neonates from August 1996 to July 2001 were analyzed. Data were collected prospectively by standard surveillance protocols and nosocomial infection site definitions from the National Nosocomial Infection Surveillance system of the Centers for Disease Control and Prevention.

RESULTS

During the 5-year study period, 665 pathogens caused 640 infections in the NICU. GNR were the most common pathogens isolated. Of the 665 pathogens 284 (43%) were GNR, followed by 223 (33.5%) GPC, 106 (16%) fungi and 52 (8%) others. spp. were the most common GNR isolated. Ceftazidime resistance was present in 56 of 81 (69%) isolates. Bloodstream and lower respiratory tract infections were the most common sites of infection. More than one-half of the pathogens (388 of 665) were isolated from neonates weighing < or =1000 g.

CONCLUSIONS

There is a change in the epidemiology of health care-associated infections in our NICU with a predominance of GNR. This change can impact choice of antimicrobials for the empiric treatment of health care-associated infections in high risk neonates.

Outbreak of infections caused by Enterobacter cloacae producing the integron-associated beta-lactamase IBC-1 in a neonatal intensive care unit of a Greek hospital

Nineteen of 27 ceftazidime-resistant Enterobacter cloacae isolates from a neonatal intensive care unit in Thessaloniki, Greece, had genes coding for the novel extended-spectrum beta-lactamase IBC-1; 18 of those 19 harbored similar conjugative plasmids and belonged to two distinct genetic lineages. A synergy test with ceftazidime and imipenem enabled us to identify five unrelated bla(IBC-1)-carrying E. cloacae isolates from other wards of the hospital. It seems that this integron-associated gene is capable of dispersing both by clonal spread and by gene dissemination.

Molecular epidemiological typing of Enterobacter cloacae isolates from a neonatal intensive care unit: three-year prospective study

Since 1992, there has been an increase in the incidence of Enterobacter sepsis in the neonatal intensive care unit (NICU) of the authors' hospital. From 1995 to 1997, a prospective molecular epidemiological survey of the colonizing and infecting strains isolated from neonates was conducted. Enterobacter cloacae was the most frequent cause of neonatal sepsis, accounting for 19.2% of all neonatal infections, reaching a peak incidence of 2.2/1000 during 1996. Fifty isolates from the NICU and four epidemiologically unrelated strains were characterized by pulse-field gel electrophoresis (PFGE), ribotyping, enterobacterial repetitive intergenic consensus (ERIC)-PCR and plasmid profiling. PFGE was the most discriminatory technique and identified 13 types (two of them classified into two and three subtypes) compared with ERIC-PCR, plasmid profiling and ribotyping that identified 11, 11 and seven types, respectively. A good correlation was found between all techniques. Five different clones caused 15 cases of sepsis. Clones A and B were prevalent in 1995 and 1996, but they were not isolated in 1997. An outbreak caused by clone G in 1997 was controlled by cohort nursing and hygienic measures, without changing the antibiotic policy. Strains were characterized by their antibiotic resistance pattern and divided into three groups. Group I correlated with PFGE types A, B1 and B2, which hyperproduced Bush type 1 chromosomal beta-lactamase and expressed extended-spectrum ?-lactamases (ESBLs). Group II only hyperproduced Bush type 1 chromosomal beta-lactamase and correlated with PFGE-types D1, D2, D3 and I. Finally, Group III, with inducible beta-lactamases, correlated with the rest of PFGE types. The sudden disappearance of E. cloacae after reinforcement of hygienic measures confirms the importance of patient-to-patient transmission.

[Impact of bacterial resistance on severe infections]

Since many years, the antimicrobial resistance increases as well as for community-acquired as for nosocomial infections. Antibiotic-resistant pneumococci are neither more nor less virulent susceptible strains. Except for immunocompromised patients, the outcome of penicillin-resistant pneumococcal infections have been similar to those in patients who are infected by susceptible ones. Current levels of S. pneumoniae resistance to penicillin and cephalosporin are not associated to an increase in mortality in children with meningitis if adequate doses of antibiotics are given. Because empiric therapy has changed, antibiotic resistance has not been associated with increased mortality. This statement can be extended to Meningococcus, for which 32 to 50% of the strains have a decreased susceptibility to penicillin. For nosocomial infections, S. aureus is the main studied pathogen. Several studies report that in patients with severe diseases (bacteremia or pneumonia) methicillin resistance of S. aureus had no significant impact on patient outcome after adjustment for different confounders. The main risk factor for mortality is the severe underlying diseases rather than the resistance as well for methicillin--resistant S. aureus, as for vancomycin resistant enterococci, Klebsiella with extended spectrum beta lactamase and Enterobacters. Recommendations for controlling epidemiologic surveillance, using barrier precautions and limiting the use of antibiotics as well in the hospital as in the community must be undertaken.