ABSTRACT
After preliminary tests indicated an increased number of heterotrophic bacteria, we investigated possible sources of contamination in a neonatal intensive care unit (NICU) water distribution system. Scanning electron microscopic examination of flexible metallic hoses associated with the system revealed the presence of a biofilm; partial 16S rDNA sequencing revealed that the biofilm contained Blastomonas natatoria. Purgation of the water system three times a day, reinforced faucet cleaning, decreasing the cold water temperature to 12 degrees , and six repeated chlorinations at concentrations as high as 2 mg/L were not sufficient to eradicate the bacterial contamination. Replacing all of the rubber-interior flexible metallic hoses with teflon-lined hoses followed by heating the water to 70 degrees successfully controlled the bacteria.
Subject(s)
Biofilms/growth & development , Gram-Negative Bacteria/physiology , Intensive Care Units, Neonatal , Water Microbiology , Colony Count, Microbial , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Gram-Negative Bacteria/genetics , Gram-Negative Bacteria/isolation & purification , Gram-Negative Bacteria/ultrastructure , Humans , Infant, Newborn , Microscopy, Electron, Scanning , RNA, Ribosomal, 16S/chemistry , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNAABSTRACT
The excision of the staphylococcal chromosomal cassette mec (SCCmec) from methicillin-resistant Staphylococcus aureus (MRSA) strains results in methicillin-susceptible S. aureus (MSSA) strains. In order to determine the proportion and diversity of multidrug-resistant MSSA (MR-MSSA) strains derived from MRSA strains, 247 mecA-negative isolates recovered in 60 French hospitals between 2002 and 2004 were characterized. The spa types of all strains were determined, and a subset of the strains (n = 30) was further genotyped by multilocus sequence typing. The IDI-MRSA assay was used to test the isolates for the presence of the SCCmec element, which was detected in 68% of all isolates analyzed. Molecular analysis of the samples suggested that 92% of the MR-MSSA isolates were derived from MRSA clones of diverse genetic backgrounds, of which the clone of sequence type 8 and SCCmec type IV(A) accounted for most of the samples. High variations in incidence data and differences in the molecular characteristics of the isolates from one hospital to another indicate that the emergence of MR-MSSA resulted from independent SCCmec excisions from epidemic MRSA isolates, as well as the diffusion of methicillin-susceptible strains after the loss of SCCmec. MR-MSSA could constitute a useful model for the study of the respective genetic and environmental factors involved in the dissemination of S. aureus in hospitals.
Subject(s)
Methicillin/pharmacology , Staphylococcal Infections/drug therapy , Staphylococcus aureus/drug effects , Staphylococcus aureus/genetics , Bacterial Proteins/genetics , Bacterial Typing Techniques , Cross Infection/epidemiology , Cross Infection/microbiology , Drug Resistance, Multiple, Bacterial/genetics , Electrophoresis, Gel, Pulsed-Field , France/epidemiology , Genes, Bacterial/genetics , Geography , Humans , Microbial Sensitivity Tests , Models, Genetic , Molecular Epidemiology , Penicillin-Binding Proteins , Polymerase Chain Reaction , Staphylococcal Infections/epidemiology , Staphylococcal Infections/microbiology , Staphylococcus aureus/classificationABSTRACT
BACKGROUND: In this study, we investigated the relationship between changes in antibiotic resistance and distribution of staphylococcal cassette chromosome (SCC) types amongst methicillin-resistant Staphylococcus aureus (MRSA) isolates expressing the most frequently encountered profiles of antibiotic resistance over an 11 year period in the University Hospital of Rennes, France. METHODS: Antibiotic susceptibilities were determined by agar diffusion. SCC typing was performed using PCR. PFGE demonstrated that isolates were phylogenetically related. RESULTS: Fourteen profiles of antibiotic resistance were defined among MRSA isolates. For each resistance profile, only one SCC type was associated: four patterns corresponded to SCC type I or IA, nine to SCC type IV or IVA, and none to types II and III. One was not typed. PFGE indicated that isolates with SCC type I or IA belong to a single genetic lineage, which also includes most of the epidemic isolates, which carry SCC type IVA. In contrast to type I or IA, isolates with SCC type IV or IVA were found to be associated with several different PFGE clusters, although not all of these represent epidemic isolates. CONCLUSIONS: During the course of the study, the spectrum of antibiotic resistance in MRSA isolates decreased. This occurred due to the emergence of strains with SCC type IV or IVA, which are susceptible to more antibiotics than type I or IA strains. The greater prevalence of such isolates could not be linked conclusively to the presence of SCC type IV or IVA, or to one particular PFGE cluster.
