Quinolone resistance among Salmonella enterica and Escherichia coli of animal origin

Escherichia coli and Salmonella enterica are major pathogens of worldwide importance in the animal industry. Antimicrobial therapy is an important tool in reducing the enormous losses caused by these infectious agents, however, resistance to existing antimicrobials especially quinolones and fluoroquinolones is widespread and of concern to veterinarians. Iranian isolates of E. coli and S. enterica from different species of animals were examined for resistance to quinolones and fluoroquinolones. Thirty-five S. enterica isolates were recovered from different animal origins. Twenty-five E. coli strains were also isolated from poultry with colibacillosis. Eleven strains of E. coli were isolated from cloacal swabs from healthy chicken. All of the E. coli strains were identified by biochemical tests. Gene invA was detected in all of the Salmonella isolates. Serogroups of Salmonella were determined by colored rapid latex test. There was no relationship among serogroups of Salmonella and resistance to quinolones. In vitro antibiotic activities of four antibiotic substances against the isolates were determined by disk diffusion test. Forty percent of S. enterica and 96% of E. coli were found to be resistant to nalidixic acid. Fifty-six percent, 72%, and 36% of E. coli strains were resistant to ciprofloxacin, enrofloxacin, and norfloxacin, respectively. However, 11.42%, 22.85%, and 5.71% of Salmonella strains were resistant to ciprofloxacin, enrofloxacin, and norfloxacin, respectively.     

Comparative analysis of antibiotic resistance and phylogenetic group patterns in human and porcine urinary tract infectious Escherichia coli

Urinary tract infections (UTIs) are one of the most common infectious diseases in humans and domestic animals such as pigs. The most frequent infectious agent in such infections is Escherichia coli. Virulence characteristics of E. coli UTI strains range from highly virulent pyelonephritis strains to relatively benign asymptomatic bacteriuria strains. Here we analyse a spectrum of porcine and human UTI E. coli strains with respect to their antibiotic resistance patterns and their phylogenetic groups, determined by multiplex PCR. The clonal profiles of the strains differed profoundly; whereas human strains predominantly belonged to clonal types B2 and D, these were not seen among the porcine strains, which all belonged to the E. coli clonal groups A and B1. Contrary to the human strains, the majority of the porcine strains were multidrug resistant. The distinct profiles of the porcine strains suggest selective pressure due to extensive antibiotic use.     

Recombinant interleukin-1 stimulates clearance of Escherichia coli K1 bacteraemia

Enhancement of non-specific resistance to neonatal Escherichia coli K1 infection by inter-leukin-1 (IL-1) was analysed. Recombinant human IL-1 administered prophylactically to newborn LPS-non-responsive C3H/HeJ mice induced rapid clearance of E. coli 018:K1 bacteraemia. The effect was dose-dependent and was observed with mice treated immediately to 1 day before bacterial challenge, whereas treatment 2 days before challenge was ineffective. Clearance of intravenously injected radiolabelled 018:K1 E. coli suggested that IL-1 triggered defence mechanisms that contribute to bacterial sequestration and killing in the spleen and liver. Comparable increase in bacterial clearance occurred in naturally resistant LPS-responsive mice that had been subjected to transient E. coli K1 bacteraemia and showed increased resistance to reinfection. In the course of E. coli K1 bacteraemia a strong synthesis of acute phase reactants was observed in both susceptible and resistant mouse strains, which indicated that these proteins alone cannot confer natural resistance to E. coli K1. IL-1 induced a very rapid synthesis of acute phase proteins. The clearance of K1 E. coli when still viable in IL-1-treated animals suggested that acute phase proteins are not likely to be major mediators of the IL-1-enhanced non-specific resistance.     

Lack of emergence of significant resistance in vitro and in vivo to the new azalide antibiotic azithromycin

In vitro experiments were performed in which 6 to 12 strains ofStaphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae andEnterobacteriaceae were passaged nine times in sub-lethal concentrations of azithromycin or control antibiotics.Streptococcus pyogenes andStaphylococcus aureus quickly became resistant to rifampin as the MIC90 increased from 0.1 to > 50 µg/ml for both species. The MIC90 of azithromycin, erythromycin, amoxicillin and cefaclor increased by three dilutions forStaphylococcus aureus. The MIC values of azithromycin forStreptococcus pyogenes, Haemophilus influenzae andEnterobacteriaceae strains did not change significantly. However, forHaemophilus influenzae and theEnterobacteriaceae strains, the MIC values of erythromycin and oral cephalosporins increased four-fold. In the in vivo experiments, mice infected withStaphylococcus aureus orEscherichia coli contaminated sutures were administered azithromycin for three days, and on day 6 viable bacterial cells were recovered from the infection site. The sustained tissue concentrations of azithromycin indicated that the organisms would have been continuously exposed to azithromycin at the site of infection. Colonies isolated from azithromycin-treated and non-treated mice were cultured and their susceptibility to azithromycin compared. The azithromycin MIC values forStaphylococcus aureus cultures from treated and non-treated animals were identical. The azithromycin MICs forEscherichia coli recovered from treated animals were on average, less than one dilution higher than for control cultures. Emergence of significant resistance to azithromycin in the laboratory was not observed with the pathogens tested.     

Prevalence and antibiotic resistance of 15 minor staphylococcal species colonizing orthopedic implants

Several species belonging to Staphylococcus genus (non Sau/ non Sep species) exhibit increasing abilities as opportunistic pathogens in colonisation of periprosthesis tissues. Here we report on antibiotic resistance of 193 strains, belonging to non Sau/ non Sep species, consecutively collected from orthopedic implant infections in a period of about 40 months. The 193 strains (representing 17% of all staphylococci isolated) were analysed for their antibiotic resistance to 16 different drugs. Five species turned out more prevalent, ranging from 1 to 5%: S. hominis (4.2%), S. haemolyticus (3.7%), S. capitis (2.7%), S. warneri (2.6%), and S. cohnii (1.6%). Among these, the prevalence of antibiotic resistance to penicillins was similar, ranging from 51% to 66%. Conversely, significant differences were observed for all the remaining antibiotics. For S. haemolyticus the resistances to oxacillin and imipenem, the four aminoglycosides and erythromycin were at least twice that of the other three species which were compared. S. warneri was on the contrary the species with the lowest occurrence of resistant strains. Ten species appeared only rarely at the infection sites: S. lugdunensis, S. caprae, S. equorum, S. intermedius, S. xylosus, S. simulans, S. saprophyticus, S. pasteuri, S. sciuri, and S. schleiferi. The behaviours of these species, often resistant to penicillins, were individually analysed. Differences in both the frequencies and the panels of antibiotic resistances observed among the non Sau/ non Sep species: i) suggest that horizontal spreading of resistance factors, if acting, was not sufficient per se to level their bio-diversities; ii) highlight and confirm the worrisome appearance within the Staphylococcus genus of emerging "new pathogens", not homogeneous for their virulence and antibiotic resistance prevalence, which deserve to be recognised and treated individually.     

Antibiotic and metal resistance among hospital and outdoor strains of Pseudomonas aeruginosa

Phenotypic analyses of antibiotic and metal resistance of a collection of 130 strains of Pseudomonas aeruginosa from various outdoor (i.e. soil, water, animals) and hospital (environment, patients, individuals with cystic fibrosis) settings were performed. Resistance was scored according to the origin of the strains and their likely exposure to antibiotics and chemicals. Most of the 76 outdoor strains showed a wild-type antibiotic resistance phenotype, i.e. resistance to minocycline and trimethoprim–sulfamethoxazole. Sixty percent of hospital strains showed a multiresistance phenotype (from 3 to 16 antibiotics) and confirmed that frequent exposure to antibiotics favored selection and maintenance of antibiotic resistance in P. aeruginosa. Twelve percent of outdoor strains naturally exposed to antiseptics and hydrocarbons showed significant resistance profiles, suggesting that chemical contaminants could contribute to selection of antibiotic resistance. For metal resistance, outdoor strains were more frequently resistant to zinc and cadmium, whereas hospital strains were more frequently resistant to mercury and copper. Differences in metal resistance between the 130 strains investigated were not related to previously characterized processes such as those implicating czcA, involved in cadmium, zinc, and cobalt resistance, or copA and copB, involved in copper resistance. Regulatory or new processes were likely to have contributed to the observed variations. Strains showing strong resistance to antibiotics were the least resistant to metals, and inversely. The lack of significant correlations between antibiotic and metal resistance suggests involvement of distinct processes that are rarely co-selected. The effects of the P. aeruginosa collection size and multi-factorial selective pressure on data sets are discussed.     

Biochemical aspects of the resistance to nourseothricin (streptothricin) of Escherichia coli strains

In most cases Escherichia coli strains phenotypically resistant against nourseothricin (streptothricin) harbour a plasmid which codes for an acetyltransferase. This enzyme transfers an acetyl group from acetyl-coenzyme A to an amino group of the β-lysine (peptide) chain of the antibiotic, thus inactivating it. Additionally, the penetrability for nourseothricin of the cell wall is drastically reduced in a high percentage of the resistant strains. Both resistance mechanisms seem to be independent of each other.     

Antibiotic Resistance Rates and Phenotypes Among Isolates of Enterobacteriaceae in French Extra-Hospital Practice

Antibiotic resistance among members of the family Enterobacteriaceae was prospectively surveyed by eight French private laboratories over a 5-month period in 1999. A total of 2,599 consecutive and nonduplicate strains were collected, mainly (60.9%) from patients in the community. Most strains (82.9%) derived from urine. Escherichia coli was the predominant (73.9%) organism isolated. The overall rates of antibiotic resistance were as follows: amoxicillin, 53.4%; amoxicillin-clavulanic acid, 27.3%; ticarcillin, 44.2%; piperacillin-tazobactam, 3.2%; cephalothin, 29.2%; cefuroxime, 14.7%; cefoxitin, 11.5%; ceftazidime, 3.6%; cefotaxime, 2.8%; cefepime, 0.3%; imipenem, 0.1%; gentamicin (G), 3.8%; tobramycin (T), 5.0%; netilmicin (Nt), 3.7%; amikacin (A), 0.7%; nalidixic acid, 14.3%; ofloxacin, 10.4%; cotrimoxazole, 21.1%; nitrofurantoin, 12.7%; fosfomycin, 5.2%; tetracycline, 50.1%; and colistin, 12.5%. Beta-lactam resistance phenotypes essentially comprised penicillinase production (33.9%), overexpression of chromosomal cephalosporinase (4.6%), and synthesis of inhibitor-resistant TEM/OXA enzymes (1.5%) or extended-spectrum -lactamases (1.5%). Aminoglycoside resistance phenotypes consisted of GTNt (93 strains), TNtA (68 strains), GTNtA (14 strains), T (4 strains), GT (3 strains), G (1 strain), and reduced uptake/permeability (3 strains). Most of the nalidixic acid-resistant strains were resistant to ofloxacin (72.8%). Antibiotic resistance rates and phenotypes varied widely according to the bacterial group and the source of the strains. Significantly higher rates were observed in private healthcare centers than in the community, due to a higher proportion of both resistant species and resistant strains. However, multidrug-resistant isolates, including five extended-spectrum -lactamase-producing strains, were also recovered from the community.     

Antimicrobial Susceptibility of Respiratory Isolates of Enterobacteriaceae and Staphylococcus aureus in Italy: Incidence and Trends Over the Period 1997–1999

The antibiotic susceptibility of members of the family Enterobacteriaceae and of Staphylococcus aureus strains isolated from the respiratory tract was assessed over the period 1997–1999 as part of the Italian Epidemiological Observatory survey sponsored by the SmithKline Foundation. A standardised method was used to determine the MICs of 22 antibiotics against isolates of Klebsiella pneumoniae (n=870), Escherichia coli (n=684), Enterobacter cloacae (n=342), Enterobacter aerogenes (n=187) and Serratia marcescens (n=135) as well as the MICs of 11 antibiotics against isolates of Staphylococcus aureus (n=1,606). Overall, the susceptibility rate of Enterobacteriaceae isolates was ≥90% to 5 agents (meropenem, imipenem, amikacin, cefepime and gentamicin); 89–80% to 2 agents (ciprofloxacin and tobramycin); and <80% to 11 agents (cefotaxime, piperacillin-tazobactam, trimethoprim-sulfamethoxazole, cefetamet, ceftriaxone, ceftazidime, aztreonam, ticarcillin-clavulanate, tetracycline, piperacillin, cefuroxime, chloramphenicol, ticarcillin, amoxicillin-clavulanate and amoxicillin). During the 3-year monitoring period, antibiotic susceptibility increased in Klebsiella pneumoniae against amoxicillin-clavulanate, in Escherichia coli against third-generation cephalosporins and aztreonam, in Enterobacter aerogenes against amoxicillin and piperacillin-tazobactam and in Serratia marcescens against most of the antibiotics. In contrast, Enterobacter cloacae showed a tendency to develop resistance to cefetamet, amikacin and ciprofloxacin. Of the total number of Staphylococcus aureus strains, 38% were methicillin resistant. Nearly 80% of the methicillin-resistant strains displayed a multiresistance pattern (additional resistance to 2 or more non-beta-lactam antibiotics). Rates of susceptibility of particular species (Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus) were compared using strains from different geographical areas of Italy (northern, central and southern) and from different nosocomial areas (outpatients, intensive care unit [ICU] inpatients, non-ICU inpatients). Susceptibility of Klebsiella pneumoniae to several antibiotics was lower in southern Italy, whereas the incidence of methicillin-resistant strains was higher in northern and central Italy. The susceptibility of Escherichia coli was similar in all three areas. No significant differences in susceptibility of Klebsiella pneumoniae or Escherichia coli were found between strains from inpatients and outpatients or from inpatients admitted to ICU and non-ICU units. The incidence of methicillin-resistant Staphylococcus aureus was higher in ICU inpatients (52%) than in non-ICU inpatients (38%) and lower in outpatients (19%) than in inpatients. Electronic Publication     

Detection of borderline oxacillin-resistantStaphylococcus aureus and differentiation from methicillin-resistant strains

Eighty-eightStaphylococcus aureus clinical isolates meeting criteria for borderline oxacillin resistance (intermediate susceptibility or resistance to oxacillin but susceptibility to amoxicillin/clavulanic acid upon disk diffusion testing) were studied to determine optimal test techniques and conditions for differentiating borderline oxacillin-resistantStaphylococcus aureus (BORSA) from methicillin-resistantStaphylococcus aureus (MRSA). Further testing revealed three distinct resistance patterns: 61 strains (69 %) consistently met BORSA criteria and had average beta-lactamase levels five- to six-fold higher than oxacillin-susceptible controls; 11 strains (13 %) were markedly heteroresistant MRSA with delayed appearance of resistant colonies leading to spurious susceptibility to amoxicillin/clavulanic acid; 16 strains (18 %) appeared to be oxacillin-susceptible on repetitive testing. Under conditions used to elicit intrinsic methicillin resistance inStaphylococcus aureus, a large percentage of BORSA appeared resistant to amoxicillin/clavulanic acid. This clearly shows that BORSA may be misidentified as MRSA while heteroresistant MRSA may appear to be BORSA. It is concluded that amoxicillin/clavulanic acid zone sizes should be measured after a full 24 hours of incubation, that susceptibility testing ofStaphylococcus aureus under certain environmental conditions should be interpreted with caution, and that MIC testing is the most reliable technique for differentiating these two resistance patterns inStaphylococcus aureus.     

Antibiotic sensitivity and resistance in Ornithobacterium rhinotracheale strains from Belgian broiler chickens

Establishing the antibiotic sensitivity of the avian respiratory pathogen Ornithobacterium rhinotracheale is difficult because of the organism's complex growth requirements and the unusually frequent occurrence of resistance. The minimal inhibitory concentrations of 10 antibiotics were determined for 45 strains of O. rhinotracheale from Belgian broiler chickens collected from 45 farms between 1995 and 1998. They were compared with the type strain, which was isolated from a turkey, and a strain isolated from a rook. All the broiler strains were resistant to lincomycin and to the β -lactams ampicillin and ceftiofur. Less than 10% of the strains were sensitive to the macrolides tylosin and spiramycin, tilmicosin and flumequine. A few strains were sensitive to enrofloxacin and doxycycline. All strains were sensitive to tiamulin.     

Antimicrobial resistance and serotype distribution among Salmonella spp. in pigs and poultry in Iceland, 2001-2005

Little information is available on antimicrobial resistance of bacteria isolated from animals and animal products in Iceland. The objective of this study was to analyze serotype distribution and antimicrobial resistance patterns of Salmonella spp. isolated from healthy chickens and pigs in Iceland during 2001-2005. A total of 163 Salmonella strains, isolated in the national Salmonella surveillance program, were available for study. Isolates were tested for antimicrobial susceptibility using a microbroth dilution method (VetMIC) and resistant strains were compared using pulsed-field gel electrophoresis (PFGE) and phage typing. The most commonly isolated serotypes were Salmonella Infantis (61%) and S. Typhimurium (33%); other serotypes were less prevalent. The overall prevalence of resistance was 13.6% in chickens and 12.8% in pigs. Twenty one isolates (12.8%) were resistant to one or more antimicrobials, 19 S. Typhimurium strains, one S. Infantis strain, and one S. Worthington strain. Sixteen out of the 19 resistant S. Typhimurium strains were multiresistant (to > or =3 antimicrobial agents), and, of these, 15 had identical or closely related PFGE patterns (previously phage typed as DT104). The prevalence of antimicrobial resistance in Salmonella spp. in pigs and poultry in Iceland is low; however, we found a multiresistant S. Typhimurium clone that causes concern. Continuous resistance surveillance is important, and further research on the source of resistant clones and possible transmission to humans is needed.     

Prevalence ofHelicobacter pylori resistance to several antimicrobial agents in a region of Germany

To evaluate the prevalence of resistance amongHelicobacter pylori in Germany, the minimum inhibitory concentrations of amoxicillin, tetracycline, clarithromycin, and metronidazole were determined by means of the E test, for 271Helicobacter pylori isolates cultured from biopsies taken during routine endoscopies in 1996 and 1997. The prevalence of metronidazole resistance was 32.1%, with resistance found more frequently in women (38.5%) than in men (24.4%). Clarithromycin resistance was rare (3.3%). Eight of nine strains resistant to clarithromycin were also resistant to metronidazole. Resistance to either metronidazole or clarithromycin was significantly (P=0.022) higher in patients with duodenal ulcer. No strain was found to be resistant to amoxicillin or tetracyline.     

Carriage of antibiotic-resistant Escherichia coli among healthy children and home-raised chickens: a household study in a resource-limited setting

We have previously observed high rates of acquired antibiotic resistance in commensal Escherichia coli from healthy children living in urban areas of Bolivia and Peru, including resistance to tetracycline and quinolones, which are not routinely used in childhood. In this work we investigated acquired resistance in commensal E. coli from healthy children and home-raised chickens in 12 households from one of the previously surveyed urban area in Bolivia, to ascertain the possibility of human-animal exchange of resistant strains in similar settings. The resistance rates to ampicillin, tetracycline, chloramphenicol, streptomycin, and trimethoprim-sulphametoxazole were overall high (≥50%) and comparable between children and chickens, whereas those to quinolones were significantly higher in chickens (81% vs. 29% for nalidixic acid; 43% vs. 10% for ciprofloxacin). Molecular characterization of tetracycline- and quinolone-resistant isolates (n?=?66) from children and chickens of three selected households revealed a remarkable clonal diversity and, in some cases, the presence of the same resistant strains among children or among chickens living in the same household, but not between children and chickens. Several resistance plasmids were characterized, but inter-clonal plasmid dissemination was not detected. Overall, the results from the present study suggested that cross-transmission between children and home-raised chickens could not represent a major spreading mechanism for resistant E. coli in households of resource-limited settings with high human-animal promiscuity.     

High level Multi-Resistant and Virulent Escherichia coli in Abeokuta,Nigeria

Multi-resistant Escherichia coli (E. coli) strains co-harboring virulence genes is a cause of high morbidity in Abeokuta, Nigeria. This study was designed to determine some virulent factors among enteropathogenic E. coli in Abeokuta, Nigeria. Approximately non-repetitive 102 isolates of E. coli were recovered from clinical samples from two health facilities in Abeokuta. Biotyping using API and antibiotic susceptibility was determined, and eae and flic genes were assayed by PCR. Antibiotic resistance relatedness was performed by DendroUPGMA. Results showed that 48.0% and 52.0 % were intestinal and extra-intestinal E. coli, ampicillin recorded 100% resistance, amoxycilli/clavulanic acid 64.7%, cotrimoxazole 57.8% and 56.8% resistance against cefotaxime, at MIC >16 ug/mL, 100%, 57.8%, and 50% have MIC50 to ampicillin, tetracycline, and ceftazidime, while 74.5% and 48.0% have MIC90 to ampicillin and ceftazidime. Significant rates of 4.9%, 7.8%, and 9.8% flic, eae, and flic/eae genes were found in intestinal isolates, while 2.9%, 2.0%, and 3.9% were found in extra-intestinal (P < 0.05). Two major clades of the resistant isolates reveal significant antibiotic relatedness among intestinal and extra-intestinal isolates, at 54% resistance similarities with very high multi-antibiotic resistance index of 1.0 (MARI). A high rate of undetected virulent E. coli pathotypes with high resistance could trigger unprecedented morbidity and mortality, mostly among children and the elderly.     

Virulence genes,antibiotic resistance and integrons in Escherichia coli strains isolated from synanthropic birds from Spain

The aim of this study was to determine the presence of virulence genes and antibiotic resistance profiles in 164 Escherichia coli strains isolated from birds (feral pigeons, hybrid ducks, house sparrows and spotless starlings) inhabiting urban and rural environments. A total of eight atypical enteropathogenic E. coli strains were identified: one in a house sparrow, four in feral pigeons and three in spotless starlings. Antibiotic resistance was present in 32.9% (54) of E. coli strains. The dominant type of resistance was to tetracycline (21.3%), ampicillin (19.5%) and sulfamethoxazole (18.9%). Five isolates had class 1 integrons containing gene cassettes encoding for dihydrofolate reductase A (dfrA) and aminoglycoside adenyltransferase A (aadA), one in a feral pigeon and four in spotless starlings. To our knowledge, the present study constitutes the first detection of virulence genes from E. coli in spotless starlings and house sparrows, and is also the first identification worldwide of integrons containing antibiotic resistance gene cassettes in E. coli strains from spotless starlings and pigeons.     

Isolation of fluoroquinolone-resistantEscherichia coli andKlebsiella pneumoniae from an infected hickman catheter

Escherichia coli andKlebsiella pneumoniae resistant to fluoroquinolones were isolated from an infected Hickman catheter in a 43-year-old diabetic patient who had previously been treated with a 24-day course of ciprofloxacin (200 mg/12 h i.v.). MICs and MBCs of nalidixic acid, norfloxacin, ciprofloxacin, ofloxacin, pefloxacin and fleroxacin were determined for the strains using the methodology recommended by the NCCLS. Both strains were resistant to all the quinolones tested. Since long-term treatment with quinolones might favour the emergence of quinolone resistance or colonization with quinolone-resistant organisms, it is important to monitor for the development of bacterial resistance during therapy with the new fluoroquinolones.     

Molecular Analysis of and Identification of Antibiotic Resistance Genes in Clinical Isolates of Salmonella typhi from India

A representative sample of 21 Salmonella typhi strains isolated from cultures of blood from patients at the Christian Medical College and Hospital, Vellore, India, were tested for their susceptibilities to various antimicrobial agents. Eleven of the S. typhi strains possessed resistance to chloramphenicol (256 mg/liter), trimethoprim (64 mg/liter), and amoxicillin (>128 mg/liter), while four of the isolates were resistant to each of these agents except for amoxicillin. Six of the isolates were completely sensitive to all of the antimicrobial agents tested. All the S. typhi isolates were susceptible to cephalosporin agents, gentamicin, amoxicillin plus clavulanic acid, and imipenem. The antibiotic resistance determinants in each S. typhi isolate were encoded by one of four plasmid types. Plasmid-mediated antibiotic resistance genes were identified with specific probes in hybridization experiments; the genes responsible for chloramphenicol, trimethoprim, and ampicillin resistance were chloramphenicol acetyltransferase type I, dihydrofolate reductase type VII, and TEM-1 β-lactamase, respectively. Pulsed-field gel electrophoresis analysis of XbaI-generated genomic restriction fragments identified a single distinct profile (18 DNA fragments) for all of the resistant isolates. In comparison, six profiles, different from each other and from the resistance profile, were recognized among the sensitive isolates. It appears that a single strain containing a plasmid conferring multidrug-resistance has emerged within the S. typhi bacterial population in Vellore and has been able to adapt to and survive the challenge of antibiotics as they are introduced into clinical medicine.     

Emergence of resistance to erythromycin and fluoroquinolones in thermotolerantCampylobacter strains isolated from feces 1987–1991

During the period 1987 to 1991 a retrospective study was performed to determine the resistance of thermotolerantCampylobacter species isolated from feces to erythromycin and fluoroquinolones. Of the 672 strains studied, 614 (91.3 %) were identified asCampylobacter jejuni and 58 (8.7 %) asCampylobacter coli. During the study period the rate of resistance ofCampylobacter jejuni to erythromycin remained relatively stable (0.9–3.5 %), while resistance ofCampylobacter coli to erythromycin emerged later (1989) with much higher rates (14.8–33 %). Overall, 11.8 % and 10.7 % ofCampylobacter jejuni strains isolated after 1987 were resistant to nalidixic acid and ciprofloxacin respectively, resistance increasing from 2.3 % in 1988 to 32 % in 1991. In 1991 the first strains ofCampylobacter coli with resistance to these fluoroquinolones were detected (rates 29 % and 26 % respectively). Of the strains resistant to nalidixic acid, only 10.9 % were susceptible to ciprofloxacin.     

Colonisation with Escherichia coli resistant to “critically important” antibiotics: a high risk for international travellers

Antimicrobial resistance among community-acquired isolates of Escherichia coli is increasing globally, with international travel emerging as a risk for colonisation and infection. The aim was to determine the rate and duration of colonisation with resistant E. coli following international travel. One hundred and two adult hospital staff and contacts from Canberra, Australia, submitted perianal/rectal swabs before and following international travel. Swabs were cultured selectively to identify E. coli resistant to gentamicin, ciprofloxacin and/or third-generation cephalosporins. Those with resistant E. coli post-travel were tested monthly for persistent colonisation. Colonisation with antibiotic-resistant E. coli increased significantly from 7.8% (95% confidence interval [CI] 3.8–14.9) pre-travel to 49% (95% CI 39.5–58.6) post-travel. Those colonised were more likely to have taken antibiotics whilst travelling; however, travel remained a risk independent of antibiotic use. Colonisation with resistant E. coli occurred most frequently following travel to Asia. While over half of those carrying resistant E. coli post-travel had no detectable resistant strains two months after their return, at least 18% remained colonised at six months. Colonisation with antibiotic-resistant E. coli occurs commonly after international travel, and can be persistent. Medical practitioners should be aware of this risk, particularly when managing patients with suspected Gram-negative sepsis.