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Four bromine- and phosphonium-terminated polystyrenes were analyzed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) using covalent cationization. Bromine-terminated polystyrenes were prepared by atom transfer radical polymerization (ATRP) giving narrow molar mass (MM) distributions with number-average molar mass ranging from 2 to 40 ku. The resultant bromine end group was converted to a phosphonium ion. Precharging the polymer by covalent cationization is an alternative approach to traditional metal cationization for MALDI−MS polymer analysis. MALDI−MS, gel permeation chromatography, and proton nuclear magnetic resonance analyses confirmed ATRP synthesis and end group modification of the polystyrenes. High performance liquid chromatography at the critical point of adsorption was used to determine a phosphonium salt conversion between 37% and 90%. Similar MMs and MM distributions determined by MALDI−MS analysis were observed for Br-terminated polystyrene ionized using traditional metal cationization and the covalently cationized (i.e., phosphonium-terminated) polystyrene. Covalently cationized samples yielded better data quality than the Br-terminated samples. Higher signal intensity and signal reproducibility were observed for the covalently cationized samples using milder laser conditions.

A derivatization reaction, guanidination, was recently reported that increases MALDI-TOF MS sensitivity toward lysine-terminated peptides. Its application conveys sequence information that can be used as a parameter in peptide mass mapping database searches. This paper presents a systematic study of the impact of guanidination on proteomic analysis of an entire bacterial organelle. Sixty-two 2-D gel isolated proteins from Caulobacter crescentus stalks were studied. A novel computer algorithm, Prodigies, was developed to analyze the data. Absolute confidence limits associated with protein assignments were established using Monte Carlo simulations of database searches. The advantages of guanidination are illustrated using both experimental and theoretical data. Keywords: proteomics • peptide mass mapping • database searching • MALDI-TOF • Caulobacter

Biotyping, slime production, bacteriophage typing, serotyping, antibiograms, and plasmid profiles were used to characterize 19 Staphylococcus epidermidis strains isolated from 12 patients with prosthetic valve endocarditis and from 7 patients with native valve endocarditis. With the API Staph battery, 12 different biocodes with, at the most, three differences were obtained. Slime production was found for 10 strains (53%). Agglutinogens investigated by agglutination with two specific sera were found for 12 strains (63.1%). Three strains were phage typable (15.2%). Against a panel of nine antimicrobial agents, 15 different profiles were found. Multiply antibiotic-resistant strains were isolated from patients with prosthetic valve endocarditis when disease onset occurred less than 18 months after heart surgery and from patients with native valve endocarditis who received antibiotics immediately prior to their illness. All of the strains were available for plasmid analysis, and all the DNA profiles were distinct. On gels run in Tris-borate buffer, 73.7% of the strains had large plasmids of more than 30 megadaltons. A small plasmid of 2.8 megadaltons was found in multiply resistant strains and in strains resistant only to tetracyclines. None of the isolates appeared to be the same strain, and the bacteriological differences between the strains were confirmed mainly by the antibiotic susceptibility profile and the plasmid pattern analysis. These bacteriological results were in agreement with the clinical data.

AbstractBetween June 1985 and March 1986, 14 cases of severe nosocomial methicillin-resistant Staphylococcus aureus(MRSA) infection, including septicemia, were observed in the intensive care unit (ICU) of a 400-bed cancer reference center. Simple control measures including contact isolation of colonized patients and reinforcement of handwashing practices among personnel were followed by a sharp decrease in the rate of infection and colonization. An epidemiological investigation showed that a single serophage variant MRSA strain was involved; peak incidence of infection was 17 per 100 ICU patient discharges; the index case was identified as a patient admitted from another hospital and the epidemic strain was then transmitted from patient-to-patient in the ICU; risk factors for acquiring infection were length of prior hospitalization, invasive procedures and number of antibiotic treatments; dissemination of the strain to other wards was only anecdotal. These results stress the effectiveness of simple measures to control outbreaks of MRSA nosocomial infections even in immunocompromised cancer patients.

We have endeavored to elaborate a suitable method for easy and rapid identification in clinical microbiology laboratories of the different species of infection-inducing, coagulase-negative staphylococci. Ten type strains described by Kloos and Schleifer and 269 strains isolated from 95 patients were tested; the classical tests were used for determination of Staphylococcus species. Strains were identified by using the Kloos-Schleifer reference method and the micromethod simultaneously. After preliminary tests on 77 substrates, 19 were retained, 15 for determination of species and 4 to reveal biotypes. The substrates were placed in wells in a rigid strip of inert plastic. Inoculation of wells was carried out with rich microbial suspensions in a special medium; reading of substrate reactions was done after incubation for 48 h at 35 degree C. The intrasystem reproducibility was excellent, from 91 to 100% for the 19 substrates. It was in excellent agreement with the reference method, 100% for type strains and 97.9% for hospital-isolated strains. Because it is simple and easy to reproduce, the micromethod will be most useful in clinical and ecological microbiology laboratories.

We compared the epidemiological markers of 13 Staphylococcus epidermidis strains isolated from an adult inpatient during a febrile episode and 23 S. epidermidis strains isolated during a presumptive outbreak of nosocomial infection in a neonatal ward. The total DNA restriction endonuclease analysis (REA) was processed along with the following conventional markers: biotyping, serotyping, phage typing, antibiotic susceptibility profiles, and plasmid profiles. The REA method was reproducible, giving stable results both in vitro and in vivo. For the hospitalized adult patient, the conventional markers of the 13 strains were concordant and the restriction profiles were identical. Five restriction groups were demonstrated during the course of the outbreak. Within two of the groups, the identities of all of the markers were used to verify whether all of the isolates belonged to the same cell clone. In a third group, combined analysis of the conventional markers and REA had to be used to demonstrate isolate similarity. On the other hand, in another group, none of the markers were similar; interpretation was not easy. An epidemiological study of S. epidermidis infections in hospitals must take into account all of the epidemiological markers: biotypes, serotypes, phage types, antibiograms, plasmid profiles, and REA.