Emergence of fluoroquinolone resistance in Campylobacter jejuni and Campylobacter coli in subjects from Finland

The in vitro susceptibilities of 102 human campylobacter strains isolated between 1978 and 1980 and 100 strains isolated in 1990 to ciprofloxacin, norfloxacin, erythromycin, gentamicin, and doxycycline were examined. The biotypes and heat-stable serotypes of the strains as well as antimicrobial treatments and travel history of the campylobacter-positive patients were also studied. The results indicated that susceptibility to erythromycin, gentamicin, and doxycycline has remained the same during the past 10 years. No gentamicin-resistant strains were found. Resistance to erythromycin was 3% in both groups of strains. However, the number of norfloxacin-resistant strains increased from 4 to 11% in the follow-up period, and ciprofloxacin-resistant strains, which had not occurred 10 years ago, composed 9% of the strains isolated in 1990. Thus, the increase of fluoroquinolone resistance in Campylobacter jejuni and Campylobacter coli has been significant in Finland in the past 10 years.

Characterization of erythromycin resistance in Campylobacter jejuni and Campylobacter coli

The mechanism of resistance to erythromycin, the drug of choice in the treatment of campylobacter gastroenteritis, was investigated. Erythromycin resistance (MICs, greater than 1,024 micrograms/ml) in three clinical isolates of Campylobacter jejuni and one C. coli isolate was determined to be constitutive and chromosomally mediated. In vivo protein synthesis in erythromycin-susceptible C. jejuni and C. coli strains was completely inhibited by low levels of erythromycin (5 micrograms/ml), whereas a high concentration of the antibiotic (100 micrograms/ml) had no effect on protein synthesis in erythromycin-resistant strains. Biological assays showed that extracellular degradation of erythromycin was not responsible for erythromycin resistance in strains of Campylobacter species. The rates and amounts of uptake of [14C]erythromycin by resistant and susceptible campylobacter cells were determined to be similar. Binding assays with purified campylobacter 70S ribosomes as well as 50S ribosomal subunits showed that those from erythromycin-resistant strans bound much less [14C]erythromycin than did those from susceptible strains. Genomic DNA from C. coli UA585 was used to transform erythromycin resistance to C. coli UA417. The erythromycin resistance marker was associated with a 240-kb SmaI fragment of the C. coli UA585 genome. Our results rule out erythromycin inactivation or efflux and are not consistent with the production of an RNA methylase, although they are consistent with a mutational mechanism of resistance due to a change in a ribosomal protein gene. This study constitutes a detailed biochemical and genetic characterization of erythromycin resistance in Campylobacter species.

In vitro susceptibilities of Campylobacter jejuni and Campylobacter coli to azithromycin and erythromycin

MICs of azithromycin and erythromycin for 20 Campylobacter coli and 20 Campylobacter jejuni strains were determined. The results demonstrated that, for Campylobacter species, all high-level erythromycin-resistant strains were also resistant to azithromycin and that azithromycin did not exhibit increased potency in comparison with that of erythromycin.

Characterization of high-level quinolone resistance in Campylobacter jejuni

High-level resistance to quinolones has previously been shown to occur in Campylobacter spp. both in vitro and in patients treated with quinolones. We have selected isolates that are resistant to quinolones by plating cells from a susceptible C. jejuni strain, UA535, on medium containing nalidixic acid at 32 micrograms/ml. Fluctuation analysis indicated that resistance occurred by mutation at a frequency of 5 x 10(-8) per cell plated. Unlike what is observed with other gram-negative organisms, the nalidixic acid-resistant mutants demonstrated high-level cross-resistance (MIC, greater than or equal to 4 micrograms/ml) to newer quinolones, including ciprofloxacin, norfloxacin, and temafloxacin, yet remained susceptible to coumermycin A1 and several other unrelated antibiotics. Mutants with an identical resistance phenotype could also be selected from UA535 with ciprofloxacin and norfloxacin at a similar frequency. To study the mechanism of quinolone resistance, DNA gyrases were purified from C. jejuni UA535 and two resistant mutants by heparin-agarose and novobiocin-Sepharose chromatography. After the respective enzyme concentrations were adjusted to equivalent units of activity in the DNA supercoiling reaction, the DNA gyrases from the resistant mutants were found to be 100-fold less susceptible than the wild-type enzyme to inhibition by quinolones. Subunit switching experiments with purified A and B subunits from the wild type and one of the quinolone-resistant mutants indicated that an alteration in the A subunit was responsible for resistance. These results show that a single-step mutation can occur in vitro in the gene encoding DNA gyrase in C. jejuni, producing clinically relevant levels of resistance to the newer quinolones.

Role of the beta-lactamase of Campylobacter jejuni in resistance to beta-lactam agents

We studied the role of the beta-lactamase of Campylobacter jejuni in resistance to beta-lactam agents. beta-Lactamase-positive strains were more resistant than beta-lactamase-negative strains to amoxicillin, ampicillin, and ticarcillin (P less than 0.05). With penicillin G, piperacillin, imipenem, and six cephalosporins, the susceptibility levels were similar for both beta-lactamase-positive and -negative strains. By using spectrophotometric and microbiological assays, the beta-lactamase from three strains hydrolyzed ampicillin, amoxicillin, penicillin G, cloxacillin, and, partially, cephalothin. Ticarcillin and piperacillin were partially hydrolyzed in the microbiological assay. There was no activity against five other cephalosporins or imipenem. Isoelectric focusing of the enzyme showed a pI of 8.8. Tazobactam was the best inhibitor of the enzyme, followed by clavulanic acid, sulbactam, and cefoxitin, while EDTA and p-chloromercuribenzoate had no activity. All beta-lactamase-positive strains became susceptible to amoxicillin and ampicillin with 1 micrograms of clavulanic acid per ml. With the same inhibitor, there was a reduced but significant effect for ticarcillin but no effect for penicillin G or piperacillin. Sulbactam had no effect and tazobactam was effective only at 2 micrograms/ml on amoxicillin and ampicillin. The beta-lactamase of C. jejuni seems to be a penicillinase with a role in resistance for only amoxicillin, ampicillin, and ticarcillin.

Use of quinolones in the treatment of gastrointestinal infections

Bacterial enteropathogens are responsible for between 40% and 80% of diarrheal illness depending upon the age of the persons affected and geographic areas where illness occurs. Antibacterial agents will shorten the illness associated with enteric infection caused by enterotoxigenic Escherichia coli, Shigella spp. and Campylobacter jejuni. These drugs also are effective in the therapy of certain clinical conditions (presumably because they are due to the same agents) which are characterized by moderate to severe diarrhea with one or more of the following: high fever, dysentery (passage of bloody mucoid stools), or high leukocyte counts in stools. Antimicrobial agents are also effective in the therapy of travelers' diarrhea. The quinolone drugs have several advantages in the management of bacterial diarrhea where strains causing illness from nearly all regions of the world will show general susceptibility: high concentrations are achieved in the intestinal lumen following oral administration and resistance development is unusual. A quinolone probably represents the optimal agent for therapy of bacterial diarrhea in adults in areas where trimethoprim-resistant enteric pathogens are common.

Antimicrobial activity of Microgard against food spoilage and pathogenic microorganisms

Microgard, a commercially available fermented milk product containing antimicrobial metabolites, was a potent inhibitor for Gram-negative bacteria such as Pseudomonas, Salmonella, and Yersinia when 1% concentration was incorporated into agar media. Gram-positive Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes were insensitive to Microgard. Kluyveromyces marxianus, an unidentified black yeast, and Penicillium expansum were partially suppressed, whereas Aspergillus niger and a yogurt spoilage yeast were tolerant to 5% Microgard. Optimum activity of Microgard was at pH 5.3 and below; the concentration that gave complete inhibition depended upon the number of bacteria present as well as the genus tested. Blood agar base reversed the antagonistic activity of Microgard against Pseudomonas putida compared with plate count agar.

Effect of iron-dextran on lethality of Nigerian isolates of Campylobacter jejuni in mice

Mice were orally and intragastically challenged with standard suspensions containing 1 x 10(9-10) Colony Forming Units (C.F.Us) per ml of strains "2" and "5" of Campylobacter jejuni isolated in Lagos. Another group of mice received the same amount of C. jejuni and 1pc iron-dextran which was incorporated into the bacterial suspension ad Mueller-Hinton broth. Two sets of control mice were included in the study. One set received only 0.2 ml of phosphate buffered saline while the second set received a mixture of killed C. jejuni and 1pc iron-dextran. A standard control organism (C. jejuni) NCTC strain 11168 was included in the study. Results presented show that infection of mice with only C. jejuni did not result in clinical diarrhoea or death of the animals as was also observed in the two sets of control. However, when the mixture of 1pc iron-dextran and C. jejuni was given, 15 (75pc) and 13 (65pc) of twenty mice each given by infant mouse infection and intragastic challenge respectively died. All the surviving animals developed diarrhoea. The difference in this result when compared with controls and those that received only C. jejuni was statistically significant (P less than 0.05). Incorporation of iron-dextran into C. jejuni suspension in the Mueller-Hinton broth enhanced virulence of the organism.

The effect of lactic acid sprays on Campylobacter jejuni inoculated onto poultry carcasses

Spraying poultry carcasses with 1% lactic acid 10 min after inoculation with Campylobacter jejuni, resulted in a significant reduction in the number of the bacteria after 4 h at 4 degrees C. Some of the inoculated cells, however, survived for at least 144 h. Spraying 10 min after inoculation with 2% lactic acid, totally eliminated all inoculated C. jejuni within 24 h. On the other hand, spraying 24 h after inoculation, with either 1% or 2% lactic acid did not eliminate all the bacteria. Inoculated C. jejuni on poultry carcasses not sprayed with lactic acid, survived at 4 degrees C throughout the sampling period (up to 144 h) and showed little tendency to decrease in number even when the carcasses started to deteriorate. Resident campylobacters on poultry carcasses were significantly reduced by the lactic acid treatment. Frozen and thawed chickens appeared to show a graying of the skins immediately after spraying with lactic acid, slightly stronger with 2% lactic acid, but the colour reverted to normal after 24 h. We were not able to observe any colour change on the fresh broiler chickens after lactic acid treatment. Our results indicated that lactic acid had a significant bactericidal effect on C. jejuni on both naturally and artificially contaminated poultry carcasses. This effect, however, became manifest only several hours after acid treatment.

In vitro activity of tosufloxacin against bacterial enteric pathogens

The in vitro activity of tosufloxacin (A-61827), a new quinolone antibiotic, was compared with that of four other quinolones against 162 bacterial enteric pathogens. Susceptibility testing was performed by using an agar dilution method. The minimal inhibitory concentration (MIC) was defined as the lowest concentration of antibiotic without visible growth. Tosufloxacin was the most active agent against Campylobacter jejuni and C. coli, and ciprofloxacin was the most active agent against Salmonella, Shigella, and Vibrio. The frequency of spontaneous point mutational resistance to tosufloxacin for three C. jejuni ranged from 1.2 x 10(-9) to 5.1 x 10(-13). No significant differences in mutational frequency were seen among the quinolones.

[In vitro susceptibility of Campylobacter jejuni and Campylobacter coli to quinolone antibiotics]

In this study, in vitro susceptibilities of 24 campylobacter strains isolated from fecal samples were tested for quinolone antibiotics. 13 of the strains were identified as C. jejuni and 11 of them were C. coli. Antibiotics which were included in this study were ciprofloxacin, ofloxacin, pefloxacin and fleroxacin. Antibiotic susceptibility tests were performed on Mueller-Hinton agar (supplemented with 5% sheep blood) using the agar dilution method. Results showed that quinolone antibiotics are very active against Campylobacter species. There was not any marked difference between the susceptibility patterns of C. jejuni and C. coli.