Gail McHugh

Salmonella typhimurium resistant to silver nitrate, chloramphenicol, and ampicillin.

A strain of Salmonella typhimurium appeared sequentially in three patients in a burn unit, and epidemiological study suggested the occurrence of person-to-person spread. This organism was responsible for both colonisation and invasive infection in these patients whose burn surfaces were receiving topical treatment with 0.5% silver nitrate (AgNO3) solution. The antibiotic and metal ionsusceptibility pattern of this strain of S. typhimurium was unique and disturbing: resistant to silver nitrate, mercuric chloride, ampicillin, chloramphenicol, tetracycline, streptomycin, and sulphonamides. This pattern of multiple resistances could be transferred by invitro mating experiments to sensitive recipient strains of Escherichia coli and S. typhimurium. Further transfer of these resistances could be consumated between different strains of E. coli. A survey of other salmonella strains isolated from patients in this hospital without thermal burns did not reveal this pattern of resistance. Also, strains of S. typhimurium, isolated elsewhere and showing simultaneous resistance to both ampicillin and chloramphenicol, were not resistant to AgNO3 in vitro. The very real danger of this strain of S. typhimurium in burn units stems from its resistance to the two most effective antibiotics (ampicillin and chloramphenicol) available for systemic therapy; and this threat may be compounded through the selection effected by the widespread topical use of AgNO3 solutions and sulphonamide preparations on burned surfaces.

Persistence of Immunoglobulin M or Immunoglobulin G Antibody Responses to Borrelia burgdorferi 10–20 Years after Active Lyme Disease

The interpretation of serological results for patients who had Lyme disease many years ago is not well defined. We studied the serological status of 79 patients who had had Lyme disease 10-20 years ago and did not currently have signs or symptoms of active Lyme disease. Of the 40 patients who had had early Lyme disease alone, 4 (10%) currently had IgM responses to Borrelia burgdorferi, and 10 (25%) still had IgG reactivity to the spirochete, as determined by a 2-test approach (enzyme-linked immunosorbent assay and Western blot). Of the 39 patients who had had Lyme arthritis, 6 (15%) currently had IgM responses and 24 (62%) still had IgG reactivity to the spirochete. IgM or IgG antibody responses to B. burgdorferi may persist for 10-20 years, but these responses are not indicative of active infection.

Prospective Study of Serologic Tests for Lyme Disease

BACKGROUND Tests to determine serum antibody levels-the 2-tier sonicate immunoglobulin M (IgM) and immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) and Western blot method or the IgG of the variable major protein-like sequence-expressed (VlsE) sixth invariant region (C6) peptide ELISA method-are the major tests available for support of the diagnosis of Lyme disease. However, these tests have not been assessed prospectively. METHODS We used these tests prospectively to determine serologic responses in 134 patients with various manifestations of Lyme disease, 89 patients with other illnesses (with or without a history of Lyme disease), and 136 healthy subjects from areas of endemicity and areas in which the infection was not endemic. RESULTS With 2-tier tests and the C6 peptide ELISA, only approximately one-third of 76 patients with erythema migrans had results that were positive for IgM or IgG seroreactivity with Borrelia burgdorferi in acute-phase samples. During convalescence, 3-4 weeks later, almost two-thirds of patients had seroreactivity with the spirochete B. burgdorferi. The frequencies of seroreactivity were significantly greater among patients with spirochetal dissemination than they were among those who lacked evidence of disseminated disease. Of the 44 patients with Lyme disease who had neurologic, heart, or joint involvement, all had positive C6 peptide ELISA results, 42 had IgG responses with 2-tier tests, and 2 patients with facial palsy had only IgM responses. However, among the control groups, the IgG Western blot was slightly more specific than the C6 peptide ELISA. The differences between the 2 test systems (2-tier testing and C6 peptide ELISA) with respect to sensitivity and specificity were not statistically significant. CONCLUSIONS Except in patients with erythema migrans, both test systems were sensitive for support of the diagnosis of Lyme disease. However, with current methods, 2-tier testing was associated with slightly better specificity.

Genetic and biochemical characterization of norfloxacin resistance in Escherichia coli.

In Escherichia coli the frequency of spontaneous single-step mutation to high levels of resistance to the newer 4-quinolone agent norfloxacin was confirmed to be over 300-fold lower than that to the older agent nalidixic acid. Serial passage on incremental concentrations of drug was necessary to produce mutants highly resistant to norfloxacin. Genetic analysis of one such highly resistant strain identified two mutations conferring drug resistance. One mutation, nfxA, mapped around 48 min on the E. coli genetic map and was shown to be an allele of gyrA by studies demonstrating an increased drug resistance of DNA gyrase reconstituted with the gyrase A subunit isolated from the mutant strain. These findings also identified the DNA gyrase A subunit as a target of norfloxacin. The second mutation, nfxB, mapped between 20 and 22 min was associated with additional resistances to tetracycline, chloramphenicol, and cefoxitin and with decreases in outer membrane porin protein OmpF. The nfxA and nfxB mutations together accounted for most, but not all, of the norfloxacin resistance phenotype of this strain. Images

Mechanisms of quinolone resistance in Escherichia coli: characterization of nfxB and cfxB, two mutant resistance loci decreasing norfloxacin accumulation.

Two genetic loci selected for norfloxacin (nfxB) and ciprofloxacin (cfxB) resistance were characterized. Both mutations have previously been shown to confer pleiotropic resistance to quinolones, chloramphenicol, and tetracycline and to decrease expression of porin outer-membrane protein OmpF. nfxB was shown to map at about 19 min and thus to be genetically distinct from ompF (21 min), and cfxB was shown to be very closely linked to marA (34 min). cfxB was dominant over cfxB+ in merodiploids, in contrast to other quinolone resistance mutations. The two loci appear to interact functionally, because nfxB was not expressed in the presence of marA::Tn5. Both nfxB and cfxB decreased the expression of ompF up to 50-fold at the posttranscriptional level as determined in strains containing ompF-lacZ operon and protein fusions. Both mutations also decreased norfloxacin accumulation in intact cells. This decrease in accumulation was abolished by energy inhibitors and by removal of the outer membrane. These findings, in conjunction with those of Cohen et al. (S. P. Cohen, D. C. Hooper, J. S. Wolfson, K. S. Souza, L. M. McMurry, and S. B. Levy, Antimicrob. Agents Chemother. 32:1187-1191, 1988), suggest a model for quinolone resistance by decreased permeation in which decreased diffusion through porin channels in the outer membrane interacts with a saturable drug efflux system at the inner membrane.

Mutants of Escherichia coli K-12 exhibiting reduced killing by both quinolone and beta-lactam antimicrobial agents.

Norfloxacin, ofloxacin, and other new quinolones, which are antagonists of the enzyme DNA gyrase, rapidly kill bacteria by largely unknown mechanisms. Earlier, we isolated, after mutagenesis, Escherichia coli DS1, which exhibited reduced killing by quinolones. We evaluated the killing of DS1 and several other strains by quinolones and beta-lactams. In time-killing studies with norfloxacin, DS1 was killed 1 to 2 log10 units compared to 4 to 5 log10 units for the wild-type parent strain KL16, thus revealing that DS1 is a high-persistence (hip) mutant. DS1 exhibited a similar high-persistence pattern for the beta-lactam ampicillin and reduced killing by drugs that differed in their affinities for penicillin-binding proteins, including cefoxitin, cefsulodin, imipenem, mecillinam, and piperacillin. Conjugation and P1 transduction studies identified a novel mutant locus (termed hipQ) in the 2-min region of the DS1 chromosome necessary for reduced killing by norfloxacin and ampicillin. E. coli KL500, which was isolated for reduced killing by norfloxacin without mutagenesis, exhibited reduced killing by ampicillin. E. coli HM23, a hipA (34 min) mutant that was isolated earlier for reduced killing by ampicillin, also exhibited high persistence to norfloxacin. DS1 differed from HM23, however, in the map location of its hip mutation, lack of cold sensitivity, and reduced killing by coumermycin. Results of these studies with strains DS1, KL500, and HM23 demonstrate overlap in the pathways of killing of E. coli by quinolones and beta-lactams and identify hipQ, a new mutant locus that is involved in a high-persistence pattern of reduced killing by norfloxacin and ampicillin.

Prospective Study of Coinfection in Patients with Erythema Migrans

The frequency of coinfection with Borrelia burgdorferi and either Anaplasma phagocytophila or Babesia microti among patients with erythema migrans, the initial skin lesion of Lyme disease, was assessed in 2 mainland locations in Rhode Island and Connecticut in a 4-year prospective study. Of the 93 patients with culture-proven erythema migrans, 2 (2%) patients had coinfection with A. phagocytophila and 2 (2%) had coinfection with B. microti. We concluded that the frequency of coinfection with these agents was low among patients with erythema migrans in the study areas.

Elimination of Plasmids from Several Bacterial Species by Novobiocin

Certain plasmids can be eliminated by exposure to growth-inhibiting concentrations of novobiocin. Novobiocin cured 8 of 14 plasmids (13 R-plasmids and an F′ lac) among one or another of four different bacterial hosts. Images

Borrelia burgdorferi Genetic Markers and Disseminated Disease in Patients with Early Lyme Disease

ABSTRACT Three genetic markers of Borrelia burgdorferi have been associated with disseminated disease: the OspC type, the 16S-23S rRNA intergenic spacer type (RST), and vlsE. Here, we modified previous methods so as to identify the three markers by PCR and restriction fragment length polymorphism in parallel, analyzed B. burgdorferi isolates from erythema migrans (EM) skin lesions in 91 patients, and correlated the results with evidence of dissemination. OspC type A was found approximately twice as frequently in patients with disseminated disease, whereas type K was identified approximately twice as often in those without evidence of dissemination, but these trends were not statistically significant. The remaining seven types identified were found nearly equally in patients with or without evidence of dissemination. RST 1 strains were significantly associated with dissemination (P = 0.03), whereas RST 2 and RST 3 strains tended to have an inverse association with this outcome. The vlsE gene was identified in all 91 cases, using primer sets specific for an N-terminal sequence of B. burgdorferi strain B31 (vlsEB31) or strain 297 (vlsE297), but neither marker was associated with dissemination. Specific combinations of the three genetic markers usually occurred together. OspC type A was always found with RST 1 and vlsEB31, type K was always identified with RST 2 and more often with vlsE297, and types E and I were almost always found with RST 3 and equally often with vlsEB31 and vlsE297. We conclude that B. burgdorferi strains vary in their capacity to disseminate, but almost all strains isolated from EM lesions sometimes caused disseminated disease.

A novel human autoantigen, endothelial cell growth factor, is a target of T and B cell responses in patients with Lyme disease.

OBJECTIVE Autoantigen presentation by HLA-DR molecules is thought to be a central component of many autoimmune diseases, but identifying disease-relevant autoantigens has been a difficult challenge. In this study we aimed to identify autoantigens in patients with antibiotic-refractory Lyme arthritis, in which infection-induced autoimmunity is thought to play an important role. METHODS Using tandem mass spectrometry, naturally presented HLA-DR self peptides from a patients synovium were identified, synthesized, and reacted with his peripheral blood mononuclear cells (PBMCs). Immunoreactive peptides and their source proteins were then tested for T and B cell responses using large numbers of patient cells or sera. RESULTS Of 120 HLA-DR-presented self peptides identified from one patient, one peptide derived from endothelial cell growth factor (ECGF) caused his PBMCs to proliferate. T and B cell responses to ECGF occurred systemically in ∼10-30% of patients with early or late manifestations of Lyme disease, primarily in those with refractory arthritis-associated HLA-DR alleles, such as DRB1*0101 and 0401. Compared with patients with antibiotic-responsive arthritis, those with antibiotic-refractory arthritis had significantly higher concentrations of ECGF in synovial fluid (P<0.0001) and more often had ECGF antibody reactivity. Among non-antibiotic-treated historical patients who developed arthritis, 26% had ECGF reactivity, which often developed before the onset of arthritis and was associated with significantly longer courses of arthritis. CONCLUSION T and B cell responses to ECGF occur in a subset of patients with Lyme disease, particularly in those with antibiotic-refractory arthritis, providing the first direct evidence of autoimmune T and B cell responses in this illness.