Streptomycin-resistant Strains Research Articles

Characterization of Ohio Strains ofXanthomonas campestrispv.vesicatoria,Causal Agent of Bacterial Spot of Pepper

In 1993 and 1994, 105 samples from pepper (Capsicum annuum) plants exhibiting symptoms of bacterial spot were collected from commercial fields and home gardens throughout Ohio and neighboring states. Eighty-nine presumptive Xanthomonas campestris pv. vesicatoria strains were isolated on a semiselective medium and identified by a combination of biochemical tests and gas chromatographic analysis of fatty acid methyl esters (FAMEs). All 89 strains caused a hypersensitive response (HR) on tobacco (Nicotiana tabacum cv. Samsun), and 76 strains were virulent on the susceptible pepper cultivar Marengo. Most (89%) of these strains were also virulent on the susceptible processing tomato cultivar Ohio 8245. The majority of the strains (80%) were identified as pepper race 3. Among the remainder, 2.6, 12, and 4% were pepper races 0, 1, and 2, respectively. One strain was identified as pepper race 6. Of the 68 strains pathogenic on tomato, 96% (65 strains) were tomato race 1 and three strains were tomato race 2. Fifty-two of the 76 strains were nonamylolytic (Amy - ) and nonpectolytic (Per - ); the remaining 24 strains, including two pectolytic (Pec + ) and 22 Pec- strains, were amylolytic (Amy + ). Although the composition of fatty acids in amylolytic and nonamylolytic strains was similar, it differed between pathogenic X. campestris pv. vesicatoria strains and nonpathogenic X. campestris strains isolated from pepper. Six serogroups were identified among X. campestris pv. vesicatoria strains using monoclonal antibodies (MAbs) in an enzyme-linked immunosorbent assay. However, 39.5% of the strains did not react with any of the MAbs and could not be assigned to a serovar. Streptomycin-resistant strains (49%) were more prevalent than copper-resistant strains (13%).

Molecular Mechanisms of Multiple Drug Resistance in Clinical Isolates of Mycobacterium tuberculosis

The molecular mechanisms of resistance to streptomycin, rifampin, and isoniazid in 53 Mycobacterium tuberculosis clinical isolates were examined. Twenty-five of 44 streptomycin-resistant strains had mutations in the rpsL gene and 5 of these had rrs gene perturbations. The region of the rpoB gene that is associated with resistance to rifampin was altered in 28 of 29 rifampin-resistant strains. Mutations in known genetic markers of isoniazid resistance were detected in 25 of 42 isoniazid-resistant isolates: 20 strains had katG gene alterations and 5 had perturbations in the inhA operon. Of the 20 multiply resistant strains with reduced sensitivity to streptomycin, rifampin, and isoniazid, 11 had mutations in genetic markers associated with resistance to each of these three drugs. These studies suggest that the primary mechanism of multiple drug resistance in tuberculosis is the accumulation of mutations in individual drug target genes.

Comparative evaluation of fleroxacin, ampicillin, trimethoprimsulfamethoxazole, and gentamicin as treatments of catheter-associated urinary tract infection in a rabbit model

Fleroxacin, ampicillin, trimethoprim-sulfamethoxazole, and gentamicin were comparatively evaluated for effectiveness in treating experimentally induced catheter-associated urinary tract infection and bacteriuria in a rabbit model with a closed drainage system. Fleroxacin, ampicillin and gentamicin effectively eliminated a lactose-negative, streptomycin-resistant uropathogenic strain of Escherichia coli (WE6933) from bag urine and catheter port urine, while trimethoprim-sulfamethoxazole only marginally reduced urine bacterial counts when compared to rabbits that received no antibiotic therapy. Fleroxacin eliminated E. coli from the catheter surfaces and from tissues adjacent to the catheter. Ampicillin or gentamicin therapy also eliminated biofilm bacteria from the catheter surfaces, but did not eliminate th residual bacteria from tissue adjacent to the septic catheters despite achieving urine levels of antibiotics substantially higher than minimum bactericidal concentrations for this pathogen. Trimethoprim-sulfamethoxazole was ineffective in eliminating E. coli from the catheter surfaces and the adjacent tissues. The ability of fleroxacin to effectively eliminate biofilm bacteria from catheter surfaces and tissues adjacent to such medical devices in the urinary tract may prove useful in the treatment of catheter-associated urinary tract infection and bacteriuria in mammals and humans.

Implications of multidrug resistance for the future of short-course chemotherapy of tuberculosis: a molecular study

Summary Tuberculosis-control programmes are compromised by the increased frequency of multidrug-resistant strains of Mycobacterium tuberculosis. We used the polymerase chain reaction (PCR) and single-strand conformation polymorphism (SSCP) analysis techniques to establish the molecular basis of resistance in 37 drug-resistant isolates of M tuberculosis, and correlated these findings with clinical and antibiotic-sensitivity data. Resistance to isoniazid was found in 36 strains, 16 of which were also resistant to ethionamide. Of the 36 isoniazid- resistant strains, 23 had mutations in the katG gene, and 5 of these also had mutations in the inhA gene. A further 5 strains had alterations in the inhA locus without the katG gene being mutated. Rifampicin resistance was less frequent (13 strains) and usually associated with isoniazid resistance (11 of 13 strains). Mutations in the rpoB gene were detected for all these rifampicin-resistant isolates. Mutations in the rpsL and rrs genes, associated with streptomycin resistance, were found in 13 of 25 and 2 of 25 streptomycin-resistant strains, respectively. The same chromosomal mutations, or combinations of mutations, were found in strains displaying single or multidrug resistance, from cases of both primary and secondary resistance, and from patients infected with human immunodeficiency virus. Thus, multidrug resistance is not dur to a novel machanism and tuberculosis chemotherapy is not subject to a new threat. Lancet1994; 344: 293–98 See Editorial page 277

Expression of parasporal crystal protein (δ—endotoxin) gene(s) ofBacillus thuringiensis var.israelensis in sporogenic and asporogenic mutant strains ofBacillus cereus

The expression of parasporal crystal protein (δ-endotoxin) coding gene(s) ofBacillus thuringlensis var.israelensis and its association, if any, with sporulation was studied in sporogenicBacillus cereus and its asporogenic mutant strains. Five asporogenous mutants ofBacillus cereus blocked at different stages of sporulation, were isolated from a streptomycin-resistant strain, The transconjugants isolated from the plasmid transfer experiments betweenBacillus thuringiensis var.israelensis and streptomycin resistantBacillus cereus and its asporogenous mutants, showed larvicidal activity. The crystal protein gene(s) are, therefore, expressed both in sporulating and in non-sporulating mutant strains ofBacillus cereus suggesting that the expression of crystal protein gene(s), is independent of sporulation specific functions inBacillus cereus.

Epidemiology and Genetic Analysis of Streptomycin-ResistantErwinia amylovorafrom Michigan and Evaluation of Oxytetracycline for Control

Streptomycin-resistant strains of Erwinia amylovora were isolated from 14 of 63 Michigan apple orchards surveyed during 1991-1993. Orchards with resistant strains were located in three geographically distinct areas. The genes encoding streptomycin resistance, strA and strB, were usually located on DNA homologous to transposon Tn5393 and to the self-transmissible plasmid pEa34. Ten percent of the resistant strains from one orchard contained DNA homologous to Tn5393 on the chromosome or a resident plasmid, pEA29. Plasmids homologous to pEa34 but lacking Tn5393 were rare in streptomycin-sensitive isolates, appearing in only three adjacent orchards 127 km from the nearest orchard with resistant strains containing pEa34 [...]

Selective Enumeration of Bifidobacterium bifidum, Enterococcus faecium, and Streptomycin-Resistant Lactobacillus acidophilus from a Mixed Probiotic Product

Modified VF-Bouillon agar with 0.5 mg/ml lithium chloride, 20 μg/ml sodium lauryl sulfate, 5 mg/ml sodium propionate, and 10 μg/ml neomycin sulfate was used with a triple-layer diffusion technique to selectively enumerate Bifidobacterium bifidum. Modified Brigg's agar was used to enumerate Enterococcus faecium. Modified Brigg's agar with 1,200 μg/ml streptomycin sulfate was used in a double-layer diffusion technique to selectively enumerate a streptomycin-resistant strain of Lactobacillus acidophilus. Selective enumeration of the individual bacterial components was compared to the mixture with an average 99% recovery of each component.

The epidemiology of Neisseria gonorrhoeae isolates in Greenland 1979-1990: the emergence, spread and disappearance of non-PPNG strains carrying the conjugative 38.9 kb plasmid.

In 1990, Greenland was one of the few areas in the world in which endemic occurrence of PPNG had not been reported. However, between 1982 and 1988 an increase in the prevalence of strains with chromosomally mediated resistance to penicillin had been noticed. The standard treatment regimen was changed early in 1983. To determine the prevalence of the 38.9 kb plasmid in gonococcal strains isolated in Greenland 1979-1990. Retrospective (1979-1984) and prospective (1985-1990) studies of antimicrobial susceptibility and plasmid profile of consecutive N. gonorrhoeae isolates from patients attending the STD clinic in Nuuk, Greenland; selected strains from 1982-1984 were subjected to serotyping and auxotyping. Before 1982, N. gonorrhoeae strains harboring the 38.9 kb conjugative plasmid were rare; in 1982, a sudden increase in the prevalence of these strains was strongly associated with the emergence of streptomycin-resistant strains with high-level chromosomally mediated resistance to penicillin, 70% of which carried the 38.9 kb plasmid. Determination of antimicrobial susceptibility pattern, auxotype and serovar supported the assumption of an epidemic spread of a single clone. The predominance of this clone was transient, but the 38.9 kb plasmid spread to penicillin-susceptible as well as to other clones of penicillin-resistant strains. The emergence of the 38.9 kb plasmid in 1982 was linked to a single clone of strains, but the subsequent spread of the plasmid was independent of the presence of other plasmids, and its disappearance was not associated with a change in standard treatment regimen.

Inheritance of resistance to oedema disease in the pig: Experiments with an Escherichia coli strain expressing fimbriae 107

Inheritance of resistance to intestinal colonization with E. coli causing oedema disease is hypothetized to be under the control of one locus consisting of two alleles with susceptibility (S) dominating resistance (s). This mode of inheritance was investigated by matting pigs, resistant and susceptible to the disease, and examining the offspring. Weaned piglets were repeatedly inoculated orally with 5 × 10 5 CFU per pig per day of a streptomycin resistant strain of E. coli serotype O139:K12(B):H1:F(107) and susceptibility determined by daily semiquantitative cultural examination of rectal swabs. Using results obtained from offspring. 5 boars were retrospectively assigned the genotype ss, 1 was assigned Ss, and 2 were assigned SS. Nine sows were designated ss, 8 classified Ss and 4 SS. Ninety two pigs resulted from matings regarded as ss×ss; 89 (97%) of these were resistant to colonization and oedema disease. Of the 168 pigs from Ss×ss matings, 83 (49%) were resistant, while only 13 (9%) of 146 pigs from matings with at least one SS parent were classified resistant. The results are compatible with inheritance being controlled by one locus and with susceptibility dominating resistance to oedema disease.

Characterization of Salmonella california and S. typhimurium Strains with Reduced Ability to Colonize the Intestinal Tract of Broiler Chicks

This study determined the ability of eight strains of Salmonella and their agarsubcultured variants to colonize the intestinal tract of broiler chicks. Nalidixic-acid (NAL)-resistant and streptomycin-resistant subcultured strains (S. california 1989/A and S. typhimurium 3366/A) that persisted in the ceca of chicks in lower numbers than their NAL-resistant parent strains (1989/O and 3366/O) were selected for additional study S. typhimurium strain 3366/A was present in the ceca of chicks in lower numbers than the parent strain 3366/O when given concomitantly with the parent strain or when the two strains were given separately to different chicks. S. california 1989/A strain was present in the ceca in lower numbers than the parent strain after concomitant oral or intracloacal inoculation. Strains 3366/O and 3366/A of S. typhimurium differed in growth rates in BHI broth and cecal mucus. The lipopolysaccharide (LPS) profile indicated that LPS components present in S. california 1989/O were missing from strain 1989/A. A mutant of 1989/O--2095/R--was also LPS- and colonization-deficient.

New Suicide Vector for Gene Replacement in Yersiniae and Other Gram-Negative Bacteria

A suicide vector named pUK4134 was constructed to enlarge the repertoire of vectors available for allelic exchange of mutated sequences in gram-negative bacteria. This plasmid combines the properties of two previously described plasmid vectors, pJM703.1 and pRTP1. pUK4134 is a suicide vector, carrying the origin of replication of the plasmid R6K and thus requiring the product of the pir gene for its stable maintenance. The rpsL gene encoding Escherichia coli ribosomal protein S12 confers streptomycin sensitivity on streptomycin-resistant strains and provides a positive selection for bacteria that have lost the plasmid following allelic exchange. The bla gene provides for selection by Ap r. Other features are a unique Eco RV cloning site, oriT of plasmid RK2, and the bacteriophage λ cos sequence. This vector was successfully used several times to carry out allelic exchange in Yersinia pestis.

Streptomycin-Resistant Bacteria Associated with Fire Blight Infections

Streptomycin-resistant strains of Erwinia amylovora were not detected from samples of 357 fire blight-infected apple and pear tissues collected from 38 orchards in New York State. Streptomycin-resistant strains of other species were detected in the fire blight-infected tissues from four apple (cv. Crispin) orchards. These included strains of oxidase-positive and oxidase-negative Pseudomonas spp. and strains of Pantoea agglomerans (.)

Antibacterial and Antifungal Spectra of Antibiotics Produced by Different Strains of Erwinia herbicola (= Pantoea agglomerans)

AbstractNine antibiotic producer strains of Erwinia herbicola (=Pantoea agglomerans), belonging to different groups, strongly inhibited growth of 21 streptomycin sensitive strains and 6 streptomycin resistant strains of E. amylovora.The antibacterial spectra of antibiotics produced by the tested strains of E. herbicola were mainly limited to E. amylovora and related tested species. The tested strains of E. amylovora that are resistant to streptomycin did not show cross‐resistance to the different types of antibiotics produced by the tested strains of E. herbicola.The antibiotics produced by the different tested strains of E. herbicola did not exert any activity on tested fungi with the exception that strains Eh 153 and Eh 351 slightly inhibited the growth of Verticillium dahliae.

Enterococcal endocarditis.

Enterococci, most often Enterococcus faecalis, cause 5%-20% of cases of infective endocarditis (IE). Enterococcal IE is usually a disease of older men, and the most frequent source of infection is the genitourinary tract. In cases of enterococcal IE, both normal and previously damaged valves can be involved. The disease most commonly presents in a subacute fashion; clinical and laboratory features are similar to those observed with IE caused by other pathogens. Diagnosis is based on the presence of clinical criteria of IE in association with positive blood cultures. Optimal therapy entails the parenteral use of a cell wall-active agent (penicillin G, ampicillin, or vancomycin) in combination with streptomycin or gentamicin in cases caused by enterococcal strains with high-level resistance to streptomycin. A 4-week treatment course may be adequate in many cases. In patients with streptomycin-resistant strains, mitral valve disease, illness of greater than 3 months' duration, and/or relapse after previous therapy, a 6-week treatment course should probably be administered. With standard treatment and the appropriate use of valve replacement, a cure rate of approximately 85% can be expected.

Crevicular IgG antibodies and recovery of Streptococcus mutans implanted by mouthrinsing.

After challenge with a streptomycin-resistant strain of Streptococcus mutans (S. mutans), a tendency to higher recovery of S. mutans was found in gingival crevicular fluid (GCF) from surfaces with a low IgG antibody activity against S. mutans than in GCF from surfaces with a high antibody activity. This suggests that antibodies in GCF may interfere with the establishment of S. mutans on gingival tooth surfaces. In GCF collected from some sites, considerably higher IgG antibody activity was observed than in homologous serum, indicating that part of the IgG response to S. mutans was locally derived.

Exposure of silver carp, Hypophthalmichthys molitrix, to Salmonella typhimurium

An experiment was conducted to determine if silver carp infected with salmonella could be depurated following transfer to clean water. A total of 140 silver carp was acclimated in static water, plastic swimming pools (7.3 m 2 surface area) for 29 days. Pools were inoculated daily with a streptomycin-resistant strain of Salmonella typhimurium at a rale of 10 000 cells per liter of water. Thirty fish in lots of five fish each were examined for the presence of S. typhimurium in the kidney, mucous and intestine. Of these lots five contained salmonella in the intestine and one in the mucous and kidney. Infected fish were than transferred to clean static water, plastic pools for depuration. Thirty fish in lots of five each were sampled for salmonella in the mucous, kidney and intestine after being held for 4 and 14 days in clean water. Salmonella was isolated from the intestines of four lots. Silver carp were thus shown to be potential carriers of salmonella.

Prevalence of recombinational versus mutational events in damaged plasmid DNA containing regions of homology with the chromosome

Plasmid DNA modified by in vitro treatments was transformed in E. coli bacterial cells. A streptomycin-resistant strain, carrying the peculiar rpsL421 mutation, was used as a recipient for the cloning vector pNO1523, which carries the wild-type (streptomycin-sensitive) rpsL allele. Transformants were streptomycin-sensitive unless a change in plasmid sequence had occurred. The analysis of the MaeI restriction pattern of plasmids isolated from streptomycin-resistant transformants, together with the detection of the phenotype that they conferred to a streptomycin-dependent strain, allowed us to identify plasmids that had undergone recombination with the host chromosome. The number of these plasmids exceeded by far that of plasmids resulting from mutational events.

Detection of high-level aminoglycoside resistance in enterococci other than Enterococcus faecalis

The ability of six screening methods to detect high-level aminoglycoside resistance in enterococcal species other than Enterococcus faecalis was investigated. The 85 Enterococcus isolates, which included 55 E. faecium, 11 E. gallinarum, 9 E. casseliflavus, 5 E. raffinosus, 4 E. avium, and 1 E. mundtii, were tested by using aminoglycoside-supplemented brain heart infusion agar (BHI), Remel EF Synergy Quad plates, high-content aminoglycoside diffusion disks, standard (prepared in-house) microdilution panels, Pasco MIC Gram Positive microdilution panels, and Vitek GPS-TA cards. When tested on BHI, 32 and 35 strains showed resistance to gentamicin and streptomycin, respectively. Resistance profiles obtained with Remel EF Synergy Quad plates were in complete agreement with those obtained on BHI. However, growth on Mueller-Hinton agar-based plates was not as heavy. Some isolates showed only weak growth and required 48 h for resistance to become evident, especially with swab inoculation of quadrants containing 2,000 micrograms of gentamicin per ml. Profiles obtained by use of the agar-based screens were used as the basis for evaluating the other methods. Disk diffusion showed complete agreement. No false resistance occurred by either microdilution method, but 48 h of incubation was needed for detection of some gentamicin-resistant isolates, and 14% of the streptomycin-resistant strains were not detected by standard microdilution. The Vitek GPS-TA card detected 81 and 100% of the gentamicin- and streptomycin-resistant isolates, respectively. In general, most methods used to detect high-level aminoglycoside resistance in E. faecalis appear to be reliable for the testing of the other enterococcal species. However, further investigations with a greater number of resistant E. raffinosus, E. avium, and E. mundtii isolates, when they are available, will be useful for establishing the full range of enterococci that can reliably be tested by the various methods.

Relapsing Native‐Valve Enterococcal Endocarditis: A Unique Cure with Oral Ciprofloxacin Combination Drug Therapy

Enterococcal endocarditis is the third most common presentation in native valves, and it is the most refractory. Unique among the streptococci, enterococci are relatively resistant to beta-lactam antibiotics requiring a combination aminoglycoside regimen for cure. Relapse is common even after apparently adequate therapy and may be seen in up to 25% of cases that involve streptomycin-resistant strains. This problem is magnified by the recent appearance of beta-lactamase-producing strains of S. faecalis resistant to both ampicillin and gentamicin. Ciprofloxacin is being investigated with a number of antimicrobials in the attempt to identify superior protocols against troublesome pathogens. However, little published data is available concerning the clinical efficacy of this drug in enterococcal endocarditis. In vitro studies and preliminary trials with animal models have generally been disappointing with broth macrodilution time-kill or agar dilution proving the most reliable in vitro methods for predicting in vivo outcomes. The urgent need to identify new combination drug regimens is underscored not only by the development of new resistance patterns, but by the well-documented toxicities of conventional therapies. The authors present a case of relapsing enterococcal endocarditis caused by a non-beta-lactamase-producing strain of S. faecalis, which demonstrated high-level resistance to streptomycin but not to gentamicin. Relapses occurred despite favorable laboratory data and aggressive beta-lactam-gentamicin therapies. Cure was achieved using oral ciprofloxacin in a combination drug regimen, which is reported here for the first time.

Effects of clindamycin and gentamicin on an experimental model of enterococcal translocation

This study was undertaken to investigate whether treatment with gentamicin plus clindamycin administered subcutaneously could prevent or eradicate translocation of Enterococcus faecalis from the gastrointestinal (GI) tract of mice. The susceptibility of mice to enteric colonisation with an exogenous, streptomycin-resistant strain of E. faecalis was found to be greatly increased when the animals were fed 5 mg of streptomycin sulphate per millilitre in their drinking water. After orogastric challenge with approximately 10 6 viable organisms, the small intestine, caecum and large intestine of 100 per cent of the streptomycin-treated animals, but of none of the control animals, were colonised with enterococci. Similarly, translocation of E. faecalis to liver, spleen and heart occurred in all of the streptomycin-treated animals, but in none of the untreated controls. Subcutaneous administration of gentamicin plus clindamycin to streptomycin-treated mice concomitant with orogastric enterococcal challenge significantly reduced intestinal populations of these organisms, but not sufficiently to prevent their translocation to extraintestinal sites. When treatment with gentamicin plus clindamycin was delayed for 1 wk following orogastric challenge with E. faecalis , intestinal population sizes of the enterococcus increased significantly, yet the percentage of animals demonstrating translocation of the organism decreased. We conclude that treatment with gentamicin plus clindamycin is ineffective in either preventing enterococcal translocation or reducing established populations of E. faecalis in this experimental model. Keywords: Translocation; Enterococcus; Clindamycin; Bacterial resistance.