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Biomedical subjects

M E Mulligan

Publications and source records attributed to M E Mulligan.

At least 19 recordsLinked to original sources
PubMed1992

Nucleotide sequence and expression of the gene for the 9 kDa FA/FB component of photosystem I from the cyanobacterium Anabaena sp. PCC7120.

The nucleotide sequence of an 813 bp Ssp I-Hinc II fragment containing the psaC gene from Anabaena sp. PCC 7120 is reported. The gene encodes a polypeptide of 81 amino acids, has a single transcript of size approximately 480 nucleotides and a single startpoint of transcription. It is flanked by a ribosome binding site on the 5' end and a potential transcription terminator on the 3' end. Comparison of the amino acid sequences of the psaC gene product from sixteen organisms shows that cyanobacteria group as a cluster distinct from monocotyledonous and dicotyledonous plants and that individual amino acids are diagnostic of each cluster.

Amino Acid Sequence↗
PubMed1992

Management and epidemiologic analyses of an outbreak due to methicillin-resistant Staphylococcus aureus.

PURPOSE: Following implementation of special measures to control a nosocomial outbreak of methicillin-resistant Staphylococcus aureus (MRSA), we used immunoblot typing in conjunction with antimicrobial susceptibility testing to investigate the epidemiology of this event and to determine whether this outbreak represented the failure of infection control measures to limit the spread of previously endemic MRSA strains or the introduction of a new strain of MRSA. MATERIALS AND METHODS: Isolates of MRSA recovered from hospitalized patients were initially categorized on the basis of antimicrobial susceptibility results. Organisms susceptible to ciprofloxacin and/or trimethoprim/sulfamethoxazole were recovered from patients at a relatively constant rate prior to December 1988 and were categorized as endemic isolates. Subsequently, there was an outbreak due to organisms resistant to both of these antibiotics; these were therefore categorized as outbreak isolates. Isolates were later characterized by immunoblot typing. Prior to this analysis, isolates were given code numbers so that clinical and epidemiologic data as well as resistance patterns were not known until this testing was complete. RESULTS: Between January 1986 and November 1988, an average of 3.9 patients per month acquired nosocomial MRSA in the Sepulveda Veterans Administration Medical Center. In contrast, from December 1988 to October 1989, 369 MRSA isolates were collected from 125 patients (an average of 11.4 patients per month). Prior to December 1988, all tested nosocomial isolates of MRSA were susceptible to ciprofloxacin and/or to trimethoprim/sulfamethoxazole. In contrast, the outbreak was due to spread of MRSA isolates resistant to these antibiotics. Immunoblot typing of 204 isolates from 98 individuals identified five distinct immunoblot types of which types B and C were by far the most common. Type B was highly associated with outbreak isolates, whereas type C was associated with endemic isolates (p less than 0.001). All sequential isolates from single patients that belonged to different susceptibility categories demonstrated discordant immunoblot types. In contrast, concordant immunoblot types were observed for 25 of 27 sequential isolates that displayed minor variations in antimicrobial resistance. The institution of more stringent infection control measures was followed by the return of nosocomial MRSA acquisition rates to pre-outbreak levels. Although novobiocin and trimethoprim/sulfamethoxazole were extensively used to treat patients harboring outbreak and endemic isolates, respectively, in no instance was the initial MRSA isolate from any patient resistant to novobiocin and only 6% of initial endemic isolates displayed trimethoprim/sulfamethoxazole resistance. A modest, significant increase in the resistance of endemic isolates to various other antimicrobial agents was noted however. CONCLUSION: Immunoblot analyses provided strong, corroborative evidence that at least two separate strains of MRSA were present during the outbreak and that a newly introduced strain with a distinctive antimicrobial resistance pattern was primarily responsible for the rapid spread of MRSA during the outbreak. The observation that previously effective infection control measures failed to prevent the nosocomial spread of a newly introduced community-acquired MRSA strain suggests that a single set of control measures may not be equally efficacious against all strains of MRSA. In this regard, previously reported variations in resistance to topical antimicrobials and/or antiseptics, and differences in virulence factors such as colonization potential, invasiveness, and survival on fomites, may warrant further study. Control of the outbreak strain of MRSA in our institution did occur after the implementation of more strenuous isolation procedures.(ABSTRACT TRUNCATED)

California↗
PubMed1992

Recurrent Staphylococcus aureus bacteremia.

Sequential blood isolates from eight patients with 10 episodes of recurrent Staphylococcus aureus bacteremia were typed by restriction endonuclease analysis of plasmid DNA (REAP DNA fingerprinting) and immunoblotting. There were six early recurrences (within 2 months of stopping antimicrobial therapy) and four late recurrences. All early recurrences isolates were identical to initial isolates. These recurrences were defined as possible relapses. Three of four late recurrence isolates were different from the preceding isolates recovered from four patients. This was considered indicative of new infections. There was complete concordance between REAP DNA fingerprinting and immunoblot typing results. However, four isolates lacked plasmid DNA and could be typed only by immunoblotting. All initial isolates from different patients were different types by immunoblotting and by REAP DNA fingerprinting (except for those lacking plasmid DNA). The bacterial traits detected by these methods appear to be stable in vivo for up to 3 months. Relapsing infections were associated with the presence of intravascular foreign bodies and vancomycin therapy of the preceding episodes.

Bacteremia↗
PubMed1991

Osteosarcoma with isolated metastases to the pleura.

Osteosarcoma is the most common primary skeletal malignancy of childhood, typically occurring between the ages of 10 and 20. The classic radiographic appearance is that of a mixed lytic and sclerotic lesion originating in the metaphysis of the long bones with cortical destruction, periostitis, and an associated soft tissue mass. Metastatic disease to the lungs is an important prognostic indicator and is found in the majority of patients dying of the disease. We present a child with osteosarcoma of the distal femur who developed extensive metastatic disease involving the chest pleura bilaterally with no other sites of involvement.

Child↗
PubMed1991

Epidemiologic and clinical utility of typing systems for differentiating among strains of methicillin-resistant Staphylococcus aureus.

Typing systems for differentiating among strains of methicillin-resistant Staphylococcus aureus (MRSA) can be valuable tools for the epidemiologist and the clinician. Specific criteria for evaluating such systems are typeability, reproducibility, and discriminatory power. An ideal typing system also would be rapid, inexpensive, technically simple, and readily available. Systems based on the detection of phenotypic variations include antimicrobial susceptibility testing, bacteriophage typing, multilocus enzyme electrophoresis, and electrophoretic methods such as protein electrophoresis and immunoblotting. Systems that directly detect genotypic variations include plasmid profile analysis, restriction enzyme analysis of plasmid DNA, restriction enzyme analysis of chromosomal DNA, Southern blot analysis of specific restriction fragment length polymorphisms, and pulse field gel electrophoresis. In general, the more widely available typing systems based on phenotypic assays and plasmid analysis have limitations in typeability and/or discriminatory power. The chromosomal DNA-based techniques, although promising, are unproven approaches still under active investigation.

Bacterial Typing Techniques↗
PubMed1991

Correlation of immunoblot type, enterotoxin production, and cytotoxin production with clinical manifestations of Clostridium difficile infection in a cohort of hospitalized patients.

To determine whether strain-specific differences in immunoblot type, enterotoxin production, or cytotoxin production correlated with clinical presentation of Clostridium difficile infection, we evaluated isolates obtained from 428 prospectively studied hospitalized patients. Of 99 isolates available for immunoblot typing, 61 were recovered from asymptomatic carriers and 38 were from patients with C. difficile-associated diarrhea. Of 17 immunoblot types, the seven types comprising the majority of isolates (82 of 99; 83%) were variably associated with disease. Neither the presence of cytotoxin in the stool nor the production of cytotoxin or enterotoxin by isolates in vitro was significantly different for symptomatic versus asymptomatic patients. Selected host factors were more predictive of symptomatic disease than was the specific infecting C. difficile strain. These results suggest that variations in the clinical severity of C. difficile infection in different patients are not solely strain-specific phenomena related to immunoblot type or to the production of cytotoxin or enterotoxin.

Antibodies, Bacterial↗
PubMed1990

Osteochondrosis dissecans of the glenoid.

Osteochondrosis dissecans of the glenoid is a rare condition that has been mentioned only once in the literature, by Lavner in 1947. Trauma is generally accepted as a cause of this disorder. Injury produces an ischemic insult to the subchondral bone and possible loose body formation if fragmentation of the articular surface occurs. Endocrine abnormalities, genetic influences, and the presence of anomalous centers of ossification may also contribute to the development of this condition. We present two patients whose clinical histories indicate a traumatic etiology of osteochondrosis dissecans of the glenoid. We also discuss the radiological, clinical, and etiological features of this entity.

Adult↗
PubMed1990

In vitro susceptibilities of oxacillin-resistant Staphylococcus aureus to dapsone and sulfamethoxazole alone and in combination with trimethoprim.

The in vitro activity of trimethoprim plus dapsone against oxacillin-resistant Staphylococcus aureus was comparable to that of trimethoprim plus sulfamethoxazole. Because of its different pharmacologic properties, dapsone may be a useful agent in combination with trimethoprim for the treatment of patients colonized with oxacillin-resistant S. aureus.

Dapsone↗
PubMed1989

Nitrogen fixation (nif) genes of the cyanobacterium Anabaena species strain PCC 7120. The nifB-fdxN-nifS-nifU operon.

A second nitrogen fixation (nif) operon in the cyanobacterium (blue-green alga) Anabaena (Nostoc) sp. strain PCC 7120 has been identified and sequenced. It is located just upstream of the nifHDK operon and consists of four genes in the order nifB, fdxN, nifS, and nifU. The three nif genes were identified on the basis of their similarity with the corresponding genes from other diazotrophs. The fourth gene, fdxN, codes for a bacterial type ferredoxin (Mulligan, M. E., Buikema, W. J., and Haselkorn, R. (1988) J. Bacteriol. 167, 4406-4410). The four genes are probably transcribed as a single operon, but are expressed at a lower level than the nifHDK operon, and only after a developmentally induced DNA rearrangement occurs that excises a 55-kilobase pair element from within the fdxN gene (Golden, J. W., Mulligan, M. E., and Haselkorn, R. (1987) Nature 327, 526-529; Golden, J. W., Carrasco, C. D., Mulligan, M. E., Schneider, G. J., and Haselkorn, R. (1988) J. Bacteriol. 170, 5034-5041). The promoter for the nifB operon was located by primer extension. Comparison of the nifB 5'-flanking sequence with the nifH 5'-flanking sequence did not reveal any consensus base pairs that would define a nif promoter for Anabaena. The operon contains two instances of 7-base pair directly repeated sequences: seven copies of the repeated sequence are found between the nifB and fdxN genes and six copies are found between the nifS and nifU genes. The function of these repeats is unknown.

Amino Acid Sequence↗
PubMed1989

Nosocomial acquisition of Clostridium difficile infection.

We studied the acquisition and transmission of Clostridium difficile infection prospectively on a general medical ward by serially culturing rectal-swab specimens from 428 patients admitted over an 11-month period. Immunoblot typing was used to differentiate individual strains of C. difficile. Seven percent of the patients (29) had positive cultures at admission. Eighty-three (21 percent) of the 399 patients with negative cultures acquired C. difficile during their hospitalizations. Of these patients, 52 (63 percent) remained asymptomatic and 31 (37 percent) had diarrhea; none had colitis. Patient-to-patient transmission of C. difficile was evidenced by time-space clustering of incident cases with identical immunoblot types and by significantly more frequent and earlier acquisition of C. difficile among patients exposed to roommates with positive cultures. Of the hospital personnel caring for patients with positive cultures, 59 percent (20) had positive cultures for C. difficile from their hands. The hospital rooms occupied by symptomatic patients (49 percent) as well as those occupied by asymptomatic patients (29 percent) were frequently contaminated. Eighty-two percent of the infected cohort still had positive cultures at hospital discharge, and such patients were significantly more likely to be discharged to a long-term care facility. We conclude that nosocomial C. difficile infection, which was associated with diarrhea in about one third of cases, is frequently transmitted among hospitalized patients and that the organism is often present on the hands of hospital personnel caring for such patients. Effective preventive measures are needed to reduce nosocomial acquisition of C. difficile.

Clostridium↗
PubMed1988

Deletion of a 55-kilobase-pair DNA element from the chromosome during heterocyst differentiation of Anabaena sp. strain PCC 7120.

The filamentous cyanobacterium Anabaena sp. strain PCC 7120 produces terminally differentiated heterocysts in response to a lack of combined nitrogen. Heterocysts are found approximately every 10th cell along the filament and are morphologically and biochemically specialized for nitrogen fixation. At least two DNA rearrangements occur during heterocyst differentiation in Anabaena sp. strain PCC 7120, both the result of developmentally regulated site-specific recombination. The first is an 11-kilobase-pair (kb) deletion from within the 3' end of the nifD gene. The second rearrangement occurs near the nifS gene but has not been completely characterized. The DNA sequences found at the recombination sites for each of the two rearrangements show no similarity to each other. To determine the topology of the rearrangement near the nifS gene, cosmid libraries of vegetative-cell genomic DNA were constructed and used to clone the region of the chromosome involved in the rearrangement. Cosmid clones which spanned the DNA separating the two recombination sites that define the ends of the element were obtained. The restriction map of this region of the chromosome showed that the rearrangement was the deletion of a 55-kb DNA element from the heterocyst chromosome. The excised DNA was neither degraded nor amplified, and its function, if any, is unknown. The 55-kb element was not detectably transcribed in either vegetative cells or heterocysts. The deletion resulted in placement of the rbcLS operon about 10 kb from the nifS gene on the chromosome. Although the nifD 11-kb and nifS 55-kb rearrangements both occurred under normal aerobic heterocyst-inducing conditions, only the 55-kb excision occurred in argon-bubbled cultures, indicating that the two DNA rearrangements can be regulated differently.

Chromosome Deletion↗
PubMed1988

Bacterial-type ferredoxin genes in the nitrogen fixation regions of the cyanobacterium Anabaena sp. strain PCC 7120 and Rhizobium meliloti.

The nucleotide sequence of a region located downstream of the nifB gene, both in the cyanobacterium Anabaena sp. strain PCC 7120 and in Rhizobium meliloti, has been determined. This region contains a gene (fdxN) whose predicted polypeptide product strongly resembles typical bacterial ferredoxins. Cyanobacteria have not previously been shown to contain bacterial-type ferredoxins. The presence of this gene suggests that nitrogen-fixing cyanobacteria have at least four distinct ferredoxins.

Amino Acid Sequence↗
PubMed1988

Immunoblots and plasmid fingerprints compared with serotyping and polyacrylamide gel electrophoresis for typing Clostridium difficile.

Two new methods for typing Clostridium difficile, immunoblotting and plasmid fingerprinting, were compared with serotyping and polyacrylamide gel electrophoresis (PAGE). Of these methods, immunoblotting was found to be the most valuable for use in a comprehensive typing system. More groups could be distinguished by immunoblotting than by serotyping or PAGE. Immunoblotting results were also more reproducible and distinctive than results by PAGE. Plasmid fingerprinting was an excellent marker for plasmid-bearing strains, but it had limited use because many isolates lacked plasmids. A unique plasmid profile observed for one group of isolates correlated with differences in phenotypic characteristics resolved by immunoblot analysis but not by serotyping or PAGE. Preliminary attempts to correlate typing results with pathogenicity of isolates were not successful but underscored the need for future studies to include careful assessment of the clinical significance of isolates.

Bacterial Proteins↗
PubMed1988

Immunoblots, antimicrobial resistance, and bacteriophage typing of oxacillin-resistant Staphylococcus aureus.

An immunoblotting system was developed for typing of oxacillin-resistant Staphylococcus aureus. Clinical isolates recovered during a 40-month period at a single institution were evaluated with this typing scheme. Results were compared with susceptibility patterns and with bacteriophage typing results for 100 clinical isolates and with plasmid fingerprints for 14 isolates. Immunoblotting was found to be a useful method with good reproducibility that distinguished seven major groups of patient isolates that were clinically and epidemiologically related. Susceptibility patterns showed specific correlations with other typing results but were inferior to immunoblotting and phage typing for differentiating major groups of organisms. Plasmid profiles failed to distinguish two major groups that were readily identified by immunoblots and phage typing. There was evidence of increasing antimicrobial resistance of endemic hospital strains. Immunoblotting correlated well with phage typing, offered an alternative method for typing isolates that could not be typed by phage typing, and was superior to susceptibility testing and plasmid profiles for distinguishing different groups of oxacillin-resistant S. aureus at our institution.

Bacteriophage Typing↗
PubMed1988

Radiologic evaluation of mass casualty victims: lessons from the Gander, Newfoundland, accident.

This study describes the use of radiologic methods in the identification of 256 bodies after the crash of an airliner in Gander, Newfoundland. Two hundred thirty-one (90%) of the victims were identified positively with dental and/or fingerprint comparisons. Radiologic data confirmed identification in 29 of these victims. Seventeen bodies without dental or fingerprint identification were presumptively identified with a variety of data, which included radiologic characteristics in four cases. Eight bodies were identified with an exclusion matrix. Radiologic input was critical in two of these. The procedures described provide practical information for radiologists in a mass casualty disaster investigation.

Accidents, Aviation↗
PubMed1987

Ciprofloxacin for eradication of methicillin-resistant Staphylococcus aureus colonization.

Ciprofloxacin (750 mg orally twice a day) was used to treat 22 episodes of methicillin-resistant Staphylococcus aureus (MRSA) colonization among 20 patients. Most patients had serious, progressive underlying medical diseases and had multiple sites of colonization. Eleven had previously received parenteral vancomycin therapy. Duration of ciprofloxacin therapy was from seven to 28 days. Therapy was discontinued in eight patients because of minor adverse reactions (two patients) or serious events attributed to underlying diseases (six patients). These serious events included seizures in two patients with known seizure disorders. Of the remaining 14 courses of therapy, 11 (79 percent) were associated with eradication of MRSA colonization. For the 18 patients who received at least two weeks of therapy, results of cultures from 47 of the 56 colonized sites became negative. Recolonization with MRSA occurred in four patients within one month. Increased resistance to ciprofloxacin was observed in seven of the 22 treatment episodes; this was associated with treatment failure in three patients and successful therapy in one patient; therapy was discontinued for other reasons in three patients. For comparison, medical records of 31 patients whose clinical specimens revealed MRSA but who did not receive ciprofloxacin were reviewed. MRSA colonization (as opposed to infection) was not eradicated in any patient who received only a single drug or no specific therapy directed against MRSA; four of seven patients given combination therapy had colonization eradicated. Although there is the potential for increased resistance, ciprofloxacin is an important new option that can be used as a single agent for eradication of MRSA colonization. Additional study is needed to define the optimum use of ciprofloxacin as a single agent and in combination therapy for MRSA colonization and infection.

Adult↗
PubMed1987

In vitro activity of novobiocin and rifampin alone and in combination against oxacillin-resistant Staphylococcus aureus.

Rifampin and novobiocin both have excellent activity against oxacillin-resistant Staphylococcus aureus, but their single use may be associated with the development of resistance. To help predict their clinical value in our institution, 60 recent clinical isolates of oxacillin-resistant S. aureus were studied for in vitro susceptibility to the two agents. Ten isolates with increased MICs to both agents or to rifampin alone were also studied by modified checkerboard and kill-curve methods. Indifference was consistently demonstrated by the checkerboard method and generally found in kill-curve studies. Prevention of development of resistance was demonstrated with the antimicrobial combinations for some isolates. Isolates with increased MICs for the two agents fell into two distinctive groups, with prevention of the development of rifampin resistance occurring in one group but not in the other, suggesting that different strains of oxacillin-resistant S. aureus may have different capacities for development of rifampin resistance.

Drug Synergism↗