Terrence L. Stull

Person-to-person transmission of Pseudomonas cepacia between patients with cystic fibrosis

Ribotyping, a method of strain identification based on analysis of bacterial genomic restriction fragment length polymorphisms, was used to investigate the acquisition of Pseudomonas cepacia by a patient with cystic fibrosis. Analysis of isolates recovered from the index patient and his contacts showed person-to-person transmission of this opportunist organism. This documentation of the transmission of P cepacia from one cystic fibrosis patient to another suggests that measures to limit the acquisition of the pathogen by patients with cystic fibrosis may be worth while.

Inapparent transmission of Pseudomonas (Burkholderia) cepacia among patients with cystic fibrosis

Pseudomonas capacia is a significant pathogen in children and young adults with cystic fibrosis, and prevention of its acquisition has become an important goal in patient management. Although it is now clear that this bacterium can be transmitted from person to person, the frequency of this mode of acquisition and the measures required to prevent it are controversial. In this report we describe the use of a novel genotyping method to extend our previous investigation of person to person transmission of P. cepacia among patients with cystic fibrosis attending an educational program. Three (20%) of 15 individuals acquired P. cepacia after contact with a chronically colonized patient. Analysis revealed that the isolates recovered from the three newly colonized patients were the same as that from the index patient. We also demonstrated that pulmonary colonization with P. cepacia may not be detected by currently recommended culture methods for as long as 2 years after acquisition. These data indicate a need to develop more sensitive means of detecting P. cepacia colonization in order better to understand host-pathogen interaction and to optimize preventive strategies.

Epidemiology and Natural History of Urinary Tract Infections in Children

Recent retrospective surveys have supported previous investigations in demonstrating the incidence of UTI during infancy; 0.3% to 1.2% of infants develop symptomatic UTI during the first year of life. Boys are more commonly infected during the first 3 months of life. After the first year, symptomatic UTI is much more frequent among girls. Similarly, asymptomatic bacteriuria is more frequently detected in boys than in girls during the first 12 months of life. Thereafter, the incidence decreases markedly in boys but increases in girls. Recent investigations indicate that lack of circumcision is a risk factor for UTI among male infants. Recurrent UTI is common and frequently asymptomatic. The most important microbiologic factor that is associated with E. coli causing acute pyelonephritis is adherence mediated by P fimbriae. Other factors, such as capsule, lipopolysaccharide, aerobactin production, and serum resistance, also determine the invasiveness of E. coli. Vesicoureteral reflux appears to be an important host factor predisposing to UTI. Microbiologic and host factors that are determinants of renal scarring are under investigation.

A plasmid mediating production of a beta-lactamase by Stenotrophomonas maltophilia

Abstract To delineate the mechanisms that contribute to the high level of antimicrobial resistance often demonstrated by Stenotrophomonas maltophilia , DNA was purified from five clinical isolates and analyzed for the presence of plasmid DNA. Purified plasmid DNA from a single isolate contained a 6.5-kb plasmid, designated pXM222, and a 5.6-kb plasmid, designated pTHB. Transformation of pTHB into Escherichia coli K-12 HB101 resulted in the expression of resistance to the penicillins and to cefazolin.

Construction of an ori cassette for adapting shuttle vectors for use in Haemophilus influenzae

An ori (origin of DNA replication) cassette, pORC, containing the P15a ori and the kanamycin-resistance-encoding gene from Tn5, was constructed. The cassette was used to convert an Escherichia coli promoter selection vector, which gene from Tn5, was constructed. The cassette was used to convert an Escherichia coli promoter selection vector, which contains a promoterless chloramphenicol (Cm) acetyltransferase-encoding gene (cat) downstream from a multiple cloning site (MCS) [Brosius and Lupski, Methods Enzymol. 153 (1987) 54-68], to an E. coli-Haemophilus influenzae shuttle vector. The shuttle vector, pQL1, was shown to transform E. coli and H. influenzae efficiently. H. influenzae promoters were cloned into pQL1 by ligation of Sau3A-digested H. influenzae chromosomal fragments. Selection and semiquantitative analysis of promoter strength were performed on agar plates containing different concentrations of Cm. With the use of pQL1, H. influenzae gene regulation can now be studied in either H. influenzae or E. coli. In addition, elements of pORC can be used to convert other specialized E. coli vectors to E. coli-H. influenzae shuttle vectors.

Ribotyping—A new tool for molecular epidemiology: Pseudomonas cepacia as a model

Abstract Ribotyping is a method of determining the molecular epidemiology of bacterial pathogens by a Southern blot analysis of the RFLPs detected by using rRNA to probe chromosomal DNA. This genotyping method offers advantages over previously employed methods in that it does not rely on potentially unstable phenotypic markers and it is applicable to a wide variety of bacterial species. The utility of this method has been clearly demonstrated in our investigations of the epidemiology of P. cepacia among individuals with CF. These studies have provided evidence supporting the possibility of nosocomial acquisition of this pathogen, and have demonstrated that CF patients may remain colonized by the same P. cepacia strain for prolonged periods. Finally, by using ribotyping, we have demonstrated that person-to-person transmission of P. cepacia between CF patients can occur. Thus, our studies of P. cepacia serve as a model for the application of ribotyping to epidemiologic investigations. This method continues to gain acceptance as a powerful tool for epidemiologists and clinical microbiologists, and is currently being employed in studies of numerous bacterial pathogens.