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Biomedical subjects

J F John

Publications and source records attributed to J F John.

At least 19 recordsLinked to original sources
PubMed1992

Relatedness of strains of methicillin-resistant coagulase-negative Staphylococcus colonizing hospital personnel and producing bacteremias in a neonatal intensive care unit.

The emergence of methicillin-resistant coagulase-negative Staphylococcus as a major bacterial pathogen in neonatal intensive care units has stimulated interest in the epidemiology of spread of the organism. During a 12-month "epidemic" of bacteremias with methicillin-resistant coagulase-negative Staphylococcus we compared the characteristics of bacteremic and personnel nasally-carried strains by traditional and biomolecular methods. Sixty-two percent of neonatal intensive care unit nurses were colonized with methicillin-resistant coagulase-negative Staphylococcus with similar speciation to bacteremic strains. Inspection of plasmid profiles revealed a moderate degree of similarity between bacteremic and colonizing strains although genomic DNA restriction patterns showed diversity. Ribotype patterns were highly conserved (90%) in personnel strains. A 2.6-kilobase plasmid DNA probe hybridized to similarly sized plasmids and larger plasmids in one-half of the strains. We hypothesize that related methicillin-resistant strains may be transferred among personnel and neonates in the neonatal intensive care unit. Epidemiologic studies of coagulase-negative staphylococci should consider multiple molecular techniques to relate strains.

Bacteremia↗
PubMed1992

Activities of newer fluoroquinolones against Shigella sonnei.

The activities of six fluoroquinolones were determined for 117 separate strains of Shigella sonnei. The order of increasing activity (MICs for 90% of strains tested) was enoxacin (0.25 micrograms/ml), temafloxacin (0.032 micrograms/ml), sparfloxacin (0.016 micrograms/ml), CI-960 (0.008 micrograms/ml), ciprofloxacin (0.008 micrograms/ml), and PD-131628-2 (0.008 micrograms/ml). These data, along with results of killing and mutational rate studies, showed that all six fluoroquinolones were highly inhibitory against S. sonnei and five fluoroquinolones were rapidly and persistently bactericidal.

Anti-Infective Agents↗
PubMed1992

Molecular epidemiology of trimethoprim-resistant Shigella boydii serotype 2 strains from Bulgaria.

In 1990 an increased number of strains of Shigella boydii serotype 2 were isolated from different regions of Bulgaria. Strains were reported as sporadic, although they showed identical phenotypic characteristics, including resistance to ampicillin, carbenicillin, streptomycin, sulfonamide, tetracycline, ticarcillin, and trimethoprim. The objective of this study was to determine the genetic relatedness of the strains and the mechanism of their antimicrobial resistance. Plasmid fingerprinting showed an identical pattern for 23 of 25 of the selected strains. All 25 strains tested transferred their resistances en bloc to an Escherichia coli recipient. Transconjugants contained a 112-kb R plasmid which carried all the resistance genes, including that conferring type I dihydrofolate reductase-mediated trimethoprim resistance (MIC greater than 2,000 micrograms/ml). Riboprobe analysis showed identical restriction length fragment polymorphisms, suggesting a highly conserved genome. All findings indicate that strains of S. boydii serotype 2 isolated in 1990 from different regions of Bulgaria were highly related genetically and can be considered representatives of a single bacterial clone. The presence of an R plasmid and selection pressure because of the usage of antimicrobial agents, particularly trimethoprim, have likely facilitated the spread of the clone throughout the country.

Bulgaria↗
PubMed1991

Isomeric DNA ladder formation of a plasmid encoding tobramycin resistance from Escherichia coli.

During a 20-month survey of resistance to three aminoglycosides (gentamicin, tobramycin, and amikacin) in Escherichia coli at a university hospital, six tobramycin-, kanamycin-resistant isolates containing a 50 kilobase conjugative R-plasmid which encoded an aminoglycoside phosphotransferase (APH-(3')) were isolated. The APH-(3') conferred resistance to kanamycin (MIC = 100 mg/L) but not to tobramycin (MIC = 20 mg/L). In both the original isolates and transconjugants the six R-plasmids demonstrated an isomeric ladder in the range of 50-112 kb, which was enhanced by exposure of the bacterial cultures to tobramycin. pJFJ2522 is the prototype for this group of plasmids. Bacterial DNA gyrase reversed the isomeric DNA ladder in pJFJ25222 by increasing the supercoiling of the plasmid DNA. Regardless of the level of supercoiling, the plasmids produced indistinguishable restriction endonuclease fragment patterns. The clinical isolates containing these plasmids demonstrated different restriction fragment length polymorphism (RFLP) of their EcoRI digested genomic DNA using E. coli rRNA as a probe. Ladder formation was plasmid specific since other tobramycin R-plasmids did not form a ladder, but it was not host specific. pJFJ25222 formed a ladder in a recA- host and displayed the same restriction pattern in a recA- as in a recA+ environment. In conclusion, pJFJ2522 contains a new tobramycin resistance gene whose mechanism of resistance is not known and whose product probably influences the isomerization of the plasmid.

Conjugation, Genetic↗
PubMed1990

Methicillin-resistant Staphylococcus aureus outbreak at a Veterans' Affairs Medical Center: importance of carriage of the organism by hospital personnel.

The reported prevalence of nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) by hospital personnel averages 2.5%. From August 1985 to September 1987, 155 patients at our Veterans' Affairs Medical Center (VAMC) were colonized or infected with MRSA. In December 1986, only two (2.1%) of 94 healthcare workers were identified as nasal carriers. Prompted by a sharp increase in the number of patients with MRSA in early 1987, contact tracing identified 450 employees, of whom 36 (8%) were nasal carriers. Thirty-five percent of surgical residents (7 of 20) were nasal carriers. Prior to being identified as a nasal carrier, one surgical resident was associated with the inter-hospital spread of the VAMC MRSA strain to the burn unit of the affiliated university hospital. Three family members of two employee carriers were also found to harbor the epidemic strain. All 36 carriers were decolonized with various antimicrobial combinations. Vigorous infection control measures were effective in controlling the epidemic. The frequency of MRSA carriage by hospital personnel at our medical center during the epidemic proved higher than previously appreciated. Thus, healthcare workers may comprise a sizable MRSA reservoir. During an MRSA epidemic, infection control should attempt to identify and decolonize this hospital reservoir, as these individuals can disseminate MRSA both within the hospital as well as into the community.

Cross Infection↗
PubMed1979

Case report 89.

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Adult↗
PubMed1979

Nephelometric detection of soluble immune complexes: methodology and clinical applications.

We have developed a method for the detection of immune complexes by laser nephelometry which is simple, reproducible, suitable for automation, and generally adaptable for diagnostic testing. Light dispersion by antigen-antibody complexes in the test samples is measured after addition of polymeric buffer, which enhances the aggregation of complexes but does not significantly affect unbound immunoglobulins. The method was used to measure immune complexes formed in vitro by incubation of tetanus toxoid with serum from a rabbit previously hyperimmunized with the same antigen, and to compare the levels of immune complexes in human sera obtained from normal adults and from 37 patients with collagen vascular diseases or endocarditis. When precautions were taken to avoid interference produced by the presence of lipoproteins or by freezing of the samples, the results obtained with human sera were consistent with those expected for normal controls and for patients with conditions thought to be associated with the presence of soluble immune complexes.

Animals↗
PubMed1978

Species identification of coagulase-negative staphylococci from urinary tract isolates.

A new scheme for identification of coagulase-negative staphylococci was applied to 138 consecutive urinary isolates of coagulase-negative staphylococci. The most common species were Staphylococcus epidermidis (53%), S. hominis (12%), and S. haemolyticus (10%). S. saprophyticus comprised only 5%. The disk method for antibiotic susceptibility for all species grouped together disclosed resistance most commonly to penicillin (35%), tetracycline (33%), methicillin (27%), and sulfonamide (24%). This pattern was also seen specifically with S. epidermidis. Further studies are needed to determine the incidence of species-specific antibiotic resistance and species-specific infection by site. This may be of particular interest in those patients with nosocomial infections due to coagulase-negative staphylococci.

Anti-Bacterial Agents↗
PubMed1977

Nosocomial infection rates at a General Army Hospital.

An eighteen month study of the incidence of nosocomial infections was conducted at a 436 bed general army hospital. The overall rate of nosocomial infection was 1.48 per cent, with a monthly range of 0.42 to 2.30 per cent. Gynecology had the highest rate of 5.8 per cent. Escherichia coli, klebsiella, and Staphylococcus aureus were the major hospital pathogens. No emergence of unusual drug resistance was observed during the course of the study. Further studies should be conducted to establish guidelines of surveillance for nurse-epidemiologists in this type of hospital.

Adolescent↗
PubMed1977

Spinal syphilis: the problem of fluorescent treponemal antibody in the cerebrospinal fluid.

Spinal manifestations of syphilis are now uncommon. Three adults with presumptive nontabetic spinal syphilis are presented. This paper should serve as a reminder to physicians that cases of late syphilis continue to occur and may be manifested as obscure spinal syndromes and be misdiagnosed unless the possibility of syphilis is constantly kept in mind. Some of the clinical dilemmas associated with the reactivity of fluorescent treponemal antibody in the cerebrospinal fluid are discussed,

Absorption↗
PubMed1976

Trimethoprim-sulfamethoxazole therapy of pulmonary melioidosis.

A 21-year-old-airman stationed in the Philippines presented with cavitary pulmonary melioidosis. When treated with trimethoprim-sulfamethoxazole, there was prompt resolution of his symptoms and the left upper lobe abscess cavity. It is suggested that this antimicrobial combination is an effective alternative regimen for pulmonary melioidosis.

Adult↗
PubMedDate not supplied

Endocarditis associated with disseminated group B streptococcal infection.

Endocarditis due to group B streptococci occurred in two men associated with meningitis in one and septic arthritis in the other. Therapy with penicillin failed in the first patient necessitating aortic valve replacement. Clindamycin therapy was not curative in the second and the patient responded to a four-week course of vancomycin therapy.

Aged↗