Susceptibility patterns of enteroaggregative Escherichia coli associated with traveller's diarrhoea: emergence of quinolone resistance.

Enteroaggregative Escherichia coli (EAggEC) isolates were identified as a cause of traveller's diarrhoea in 50 (9%) of 517 patients and their antimicrobial susceptibility was determined. Molecular epidemiological characterisation and investigation of the mechanisms of acquisition of quinolone resistance among nalidixic acid-resistant EAggEC strains was performed. Seventeen (34%) of 50 patients needed antimicrobial therapy, because of persistence of symptoms in nine cases and the severity of symptoms in eight cases. Ampicillin and tetracycline resistance was high, whereas chloramphenicol and co-trimoxazole showed moderate activity and amoxicillin plus clavulanic acid, nalidixic acid and ciprofloxacin showed very good activity. Resistance to nalidixic acid was demonstrated in three isolates, two from patients who had travelled to India. In all three strains the resistance was linked to mutations in the gyrA gene alone or in both gyrA and parC genes. Although ciprofloxacin shows excellent in-vitro activity and could be useful in the treatment of traveller's diarrhoea in patients travelling abroad, it may not be useful in patients who have journeyed to India or to Mexico.     

Purulent pleurisy caused byCampylobacter lari

An 80-year-old debilitated patient developed purulent pleurisy caused by aCampylobacter lari isolate. The patient underwent surgical drainage and received antibiotic therapy with amoxicillin/clavulanic acid and ofloxacin. Antibiotic susceptibility data showed that the isolate was fully sensitive to clarithromycin, tetracycline, aminoglycosides, and ciprofloxacin. Imipenem and amoxicillin plus clavulanic acid were the most active -lactam agents.     

Fluoroquinolone and macrolide resistance in Campylobacter jejuni isolated from broiler slaughterhouses in southern Brazil

Campylobacter jejuni is recognized as a leading cause of acute bacterial gastroenteritis in humans. The over-use of antimicrobials in the human population and in animal husbandry has led to an increase in antimicrobial-resistant infections, particularly with fluoroquinolones and macrolides. The aim of the present study was to provide information of the current status of antimicrobial resistance patterns in Campylobacter jejuni from poultry sources. Fifty strains were recovered from broiler slaughterhouses in Rio Grande do Sul state, Brazil, 2012. The strains were investigated for antimicrobial susceptibility against three agents (ciprofloxacin, nalidixic acid and erythromycin) by minimal inhibitory concentrations. The strains were analysed by polymerase chain reaction-restriction fragment length polymorphism for detection of the Thr-86 mutation that confers resistance to ciprofloxacin. In addition, all the strains were tested for the presence of efflux systems (cmeB gene) conferring antimicrobial resistance. The minimum inhibitory concentrations results showed that 98% of isolates were sensitive to erythromycin and most isolates were resistant to ciprofloxacin (94%) and nalidixic acid (90%). A complete correlation was observed between the minimum inhibitory concentrations and PCR-RFLP assay. Finally, the cmeB gene that is responsible for multidrug resistance was detected in 16 isolates out the 50 strains (32%).     

A study on bacterial flora and antibacterial resistance of yolk sac infection in Japanese quail (Coturnix japonica)

In order to study Enterobacteriaceae contamination of dead-in-shell embryos in quails and the antibacterial resistance of isolated salmonellae, 335 quail eggs which did not have external piping during the hatching period were transferred to the microbiology laboratory. Swab samples were collected from the interior contents of individual eggs, and the swabs were inoculated into tryptic soy broths (TSB) and selenite-F broths in groups of five swabs in each media. All cultured media were incubated at 37 °C. After 24 h, the TSB cultures were streaked on MacConkey agars, but cultures in selenite-F were subcultured on Salmonella–Shigella agars. After 24–48 h incubation of the solid media, the plates were observed for colony formation. Identification of the isolated bacteria was performed using standard bacteriological and biochemical procedures. Final confirmation of Salmonella in the isolates was undertaken using the slide serum agglutination test. Disc diffusion test on Muller–Hinton agar was used to determine the sensitivity of salmonellae isolates to antibacterial agents. Bacterial cultures of unhatched quail eggs showed 15.8 % contamination with Enterobacteriaceae. The isolation rate of Salmonella spp. from the unhatched quail eggs was 2.98 %. With respect to resistance of antimicrobial agents to Salmonella spp., all of the 10 antibiotics used (ampicillin, colistin, cephalexin, ciprofloxacin, chloramphenicol, gentamycin, furazolidone, nalidixic acid, norfloxacin and tetracycline) showed 100 % susceptibility to gentamycin. Drug resistance to ampicillin, colistin, cephalexin, ciprofloxacin, chloramphenicol, nalidixic acid and tetracycline were 80, 10, 50, 10, 40, 80 and 80 %, respectively. There were no observed drug resistance among the salmonellae isolates to gentamycin, furazolidone and norfloxacin.     

Antimicrobial resistance patterns of Escherichia coli through the digestive tract of veal calves

The aim of the present study was to evaluate differences in resistance patterns of Escherichia coli in different parts of the digestive tract of veal calves. Therefore, after slaughter, the lower intestinal tract of 19 calves was sampled at five locations (duodenum, jejunum, cecum, colon, and rectum), and up to three E. coli isolates per sample underwent susceptibility testing for seven antimicrobial agents (gentamicin, amoxycillin + clavulanic acid, tetracycline, trimethoprim + sulfamethoxazole, ampicillin, nalidixic acid, and enrofloxacin), using the Kirby-Bauer disk diffusion method. Multiresistance (resistance to more than two compounds) was present in 93.5% of all isolates (n = 179). For gentamicin, nalidixic acid, and enrofloxacin, the percentage of resistant E. coli isolates was significantly lower in the duodenum and jejunum than in the cecum, colon, and rectum. For ampicillin, the percentage of resistance was significantly lower in the jejunum, compared to the other segments of the intestinal tract. For the other antimicrobials tested, no significant differences in the percentage of resistant isolates throughout the intestinal tract were detected. In conclusion, resistance among enteric E. coli from veal calves can reach high levels and prevalence depends on localization of sampling. These considerations should be taken into account when further fine-tuning sampling protocols for indicator bacteria.     

Effect of exposure to fluoroquinolones and beta-lactams on the in vitro activity of other groups of antibiotics in Salmonella spp

After designing in vitro models of repeated exposure of Salmonella spp. to various beta-lactams and fluoroquinolones we studied the decrease in susceptibility to other antibiotic families of the mutants generated. There was a decrease in the susceptibility of all the mutants to tetracycline, cotrimoxazole and chloramphenicol. Mutants generated following exposure to fluoroquinolones showed reduced susceptibility to amoxicillin, amoxicillin/clavulanic acid, cefoxitin and cefuroxime, whereas mutants generated following beta-lactam exposure showed reduced susceptibility to nalidixic acid and ciprofloxacin. We observed that the efflux pump systems are activated in the mutants generated and this may therefore be the cause of the decrease in susceptibility. In many cases the decrease is small and is not detected if the CLSI criteria are applied. Nevertheless, more detailed studies should be done to evaluate the importance of this phenomenon and rationalize the use of antibiotics in both humans and animals so as to control the increase in the number of multiresistant strains.     

Antimicrobial susceptibility trends among Escherichia coli and Shigella spp. isolated from rural Egyptian paediatric populations with diarrhoea between 1995 and 2000

Antimicrobial susceptibility testing was performed on 3,627 isolates of Escherichia coli and 180 isolates of Shigella spp. collected in rural locations from 875 Egyptian children with diarrhoea between 1995 and 2000. The cumulative rates of resistance for E. coli and Shigella spp. were high (respectively, 68.2% and 54.8% for ampicillin, 24.2% and 23.5% for ampicillin-sulbactam, 57.2% and 42.5% for trimethoprim-sulphamethoxazole, and 50.9% and 75.4% for tetracycline). Non-enterotoxigenic E. coli (NETEC) isolates had a consistently higher level of antimicrobial resistance than did enterotoxigenic E. coli (ETEC) isolates. Trend testing showed significant decreases in resistance to ampicillin, ampicillin-sulbactam and tetracycline among all E. coli isolates. Increasing rates of resistance were observed for trimethoprim-sulphamethoxazole in ETEC isolates and Shigella spp., but not in NETEC isolates. Low levels of resistance were observed for all other antimicrobial agents tested. Overall, high levels, but decreasing trends, of resistance to commonly used antimicrobial agents were detected among isolates of E. coli and Shigella spp. from children in rural Egypt.     

Drug resistance in Campylobacter jejuni, C coli, and C lari isolated from humans in north west England and Wales, 1997

AIMS: To test the sensitivity of strains of Campylobacter species isolated from humans in England and Wales against a range of antimicrobial agents for the purpose of monitoring therapeutic efficacy and as an epidemiological marker. METHODS: An agar dilution breakpoint technique was used to screen isolates against ampicillin, chloramphenicol, gentamicin, kanamycin, neomycin, tetracycline, nalidixic acid, ciprofloxacin, and erythromycin. Minimal inhibitory concentrations (MIC) were also determined for a sample of quinolone resistant strains. RESULTS: Approximately 50% of strains tested were resistant to at least one drug. Strains which were resistant to four or more of the drugs tested were classified as multiresistant; this occurred in 11.3% of C jejuni, 19.9% of C coli, and 63.6% of C lari. Resistance to erythromycin occurred in 1.0% of C jejuni and 12.8% of C coli. Resistance to quinolones occurred in 12% of strains, with a ciprofloxacin MIC of > 8 mg/l and a nalidixic acid MIC of > 256 mg/l; a further 4% of strains had intermediate resistance with a ciprofloxacin MIC of between 0.5 and 2 mg/l (fully sensitive strains, 0.25 mg/l or less) and a nalidixic acid MIC of between 32 and 64 mg/l (fully sensitive strains, 8 mg/l or less). CONCLUSIONS: Resistance to quinolones in campylobacters from human infection may relate to clinical overuse or use of fluoroquinolones in animal husbandry. Both veterinary and clinical use should be reconsidered and fluoroquinolone drugs used only as a treatment for serious infections requiring hospital admission. Erythromycin resistance is still rare in C jejuni but much more common in C coli.     

Antimicrobial resistance of Campylobacter spp. isolated from broiler flocks in Iceland 2001-2005

Minimum inhibitory concentrations of six antimicrobial agents were determined for one Campylobacter sp. isolate from each of the 362 Campylobacter-positive commercial chicken flocks in Iceland in the years 2001-2005. Of all isolates tested, 6.9% were resistant, although none were multiresistant. Resistance to ampicillin was most commonly observed (3.6%) followed by resistance to enrofloxacin (3%), nalidixic acid (1.9%), and oxytetracyclin (0.3%), with cross-resistance between enrofloxacin and nalidixic acid. All isolates were susceptible to erythromycin and gentamicin. Resistance rates among Campylobacter coli isolates (7/13 or 53.8%) were much higher than among Campylobacter jejuni isolates (18/349 or 5.2%), and resistance patterns differed. Resistant strains were compared using pulsed field gel electrophoresis. Macrorestriction with SmaI and KpnI restriction enzymes yielded 13 different pulsotypes, none of which indicated a predominant genotype. Specific pulsotypes with uniform resistance patterns arising on geographically separated farms indicate clonal dissemination. Although resistance levels were low and similar to that seen in the other Nordic countries, further research on this matter is needed as there is no antimicrobial selective pressure in chicken farming in Iceland.     

Antimicrobial resistance pattern of Escherichia coli causing urinary tract infections,and that of human fecal flora,in the southeast of Iran

Sensitivity of 500 Escherichia coli isolates from urinary tract infections (UTIs, 311 isolate) and fecal samples (189 isolates) was tested against 12 antimicrobial agents using the standard disk diffusion method. Although the rate of resistance to antimicrobial agents was higher in the UTIs, in comparison with the fecal samples, the only significant difference was found in cases of tetracycline (p = 0.008), nalidixic acid (p = 0.038), and trimethoprim-sulfamethoxazole (Sxt,p = 0.05). The pattern of sensitivity to antimicrobial agents with respect to statistically significant difference in the number of sensitive isolates (p < or = 0.01) was: ceftizoxime (99.4%) and ceftriaxone (99.2%) > gentamicin (97.8%), ciprofloxacin (93%) and nitrofurantoin (92%) > cefazoline (85.2%) and nalidixic acid (84.6%) > chloramphenicol (71.6%), cephradine (69.6%) and tetracycline (63.2%) > Sxt (41.6%) > ampicillin (23.2%). Sensitivity of the isolates in respect to sex and age was also determined and compared during this study. Resistance to three or more antimicrobial agents (multidrug resistance, MDR) was found in 209 (41.8%) of the isolates. The high rate of resistance to Sxt and the presence of a high rate of MDR isolates in this area suggest that a reevaluation of the first-line therapeutic may be necessary for the treatment of UTIs in this area.     

Antimicrobial resistance of Salmonella serotypes isolated from slaughter-age pigs and environmental samples

The aim of this study was to determine the antimicrobial resistance patterns of Salmonella strains isolated from slaughter-age pigs and environmental samples collected at modern swine raising facilities in Brazil. Seventeen isolates of six serotypes of Salmonella enterica subsp. enterica were isolated out of 1,026 collected samples: Salmonella Typhimurium (1), Salmonella Agona (5), Salmonella Sandiego (5), Salmonella Rissen (1), Salmonella Senftenberg (4), and Salmonella Javiana (1). Resistance patterns were determined to extended-spectrum penicillin (ampicillin), broad-spectrum cephalosporins (cefotaxime and ceftriaxone), aminoglycosides (streptomycin, neomycin, gentamicin, amikacin, and tobramycin), narrow-spectrum quinolone (nalidixic acid), broad-spectrum quinolone (ciprofloxacin and norfloxacin), tetracycline, trimethoprim, and chloramphenicol. Antimicrobial resistance patterns varied among serotypes, but isolates from a single serotype consistently showed the same resistance profile. All isolates were resistant to tetracycline, streptomycin, and nalidixic acid. One isolate, Salmonella Rissen, was also resistant to cefotaxime and tobramycin. All serotypes were susceptible to ceftriaxone, norfloxacin, ciprofloxacin, ampicillin, gentamicin, and chloramphenicol. The high resistance to tetracycline and streptomycin may be linked to their common use as therapeutic drugs on the tested farms. No relation was seen between nalidixic acid and fluoroquinolone resistance.     

Relationship between phylogenetic groups,antibiotic resistance and patient characteristics in terms of adhesin genes in cystitis and pyelonephritis isolates of Escherichia coli

Extraintestinal pathogenic Escherichia coli (E. coli) is considered as the main causative agent of urinary tract infections worldwide. The relationship between antimicrobial resistance, phylogenetic groups, patient characteristics and adhesin virulence genes are complex and not fully understood. In this study, among 146 urinary isolates of E. coli, phylogenetic groups and various adhesin virulence genes were examined with multiplex Polymerase Chain Reaction methods. Patient characteristics divided into sex, cystitis and pyelonephritis; community-acquired and hospital-acquired; complicated and uncomplicated infection. Antimicrobial resistance was also determined. The papAH gene was seen more often in pyelonephritis than cystitis and female than male patients. iha gene was more frequent in hospital-acquired infections than in community-acquired infections. sfa/focDE was more frequent in ampicillin, amikacin, gentamicin, nalidixic acid, norfloxacin, cefuroxime, ceftriaxone, cefazolin, cefotaxime, ciprofloxacin and trimethoprim/sulfamethoxazole susceptible and extended-spectrum β-lactamase (ESBL) and multi-drug resistance (MDR) negative isolates. focG was seen more often in nalidixic acid, norfloxacin, cefuroxime, ceftriaxone, ciprofloxacin susceptible and MDR negative isolates. fimH and papAH were more commonly observed in amoxicillin/clavulanic acid and cefotaxime susceptible isolates, respectively. iha and afa/draBC genes were more frequent in resistant isolates than the susceptible ones; for iha, in ampicillin, amoxicillin/clavulanic acid, nalidixic acid, cefuroxime, ceftriaxone resistant and ESBL and MDR positive isolates; for afa/draBC, in cefotaxime, cefuroxime, ciprofloxacin, trimethoprim/sulfamethoxazole resistant and ESBL and MDR positive isolates, this trend was observed. ST 131 E. coli virulence gene pattern has a direct effect on resistance profile. Isolates belong to that clonal group has MDR and commonly harbour afa/draBC and iha genes. Our findings may provide new insights into the relationships between pathogenesis, patient characteristics and resistance of E. coli UTI.     

Prevalence of resistant Helicobacter pylori isolates in Bulgarian children

The aim of this study was to assess the primary and combined resistances of Helicobacter pylori isolates obtained from paediatric patients in 2000-2001 to seven antimicrobial agents. Resistance rates of pre-treatment isolates from 115 children were investigated by the limited agar dilution method alone and by the E-test. The cut-off concentrations for resistance were: metronidazole >8 mg/L, clarithromycin and azithromycin >1 mg/L, clindamycin >4 mg/L, amoxicillin >0.5 mg/L, tetracycline >4 mg/L and ciprofloxacin >1 mg/L. Primary resistance rates were: metronidazole 15.8%, clarithromycin 12.4%, azithromycin 14.6%, clindamycin 20.0%, amoxicillin 0%, metronidazole + clarithromycin 4.5%, ciprofloxacin 6.0%, metronidazole + clarithromycin + ciprofloxacin 1.2%, tetracycline 3.1% and metronidazole + ciprofloxacin 1.2%. There were no significant age (1-9 years versus 10-18 years) or gender differences. Prevalence of both macrolide-resistant and intermediately susceptible strains was 21.9% for azithromycin and 15.9% for clarithromycin. Of 18 metronidazole-resistant isolates, 77.8% exhibited a metronidazole MIC > or = 32 mg/L. H. pylori resistance rates to metronidazole, clarithromycin and both agents were relatively low in Bulgarian children. However, resistance was found to all drugs tested except for amoxicillin. The consumption of newer macrolides and tetracyclines could be related to the prevalence of resistance to the corresponding agents. There were no significant differences in primary resistance rates of H. pylori to antimicrobial agents between children and adults except for metronidazole. Multi-drug resistance to newer macrolides, metronidazole and ciprofloxacin in association with a slightly elevated amoxicillin MIC (0.38 mg/L) was detected in one strain.     

Prevalence and antimicrobial resistance of Campylobacter jejuni and Campylobacter coli isolated from raw camel, beef, and water buffalo meat in Iran

This study was conducted to determine the prevalence and antimicrobial resistance of Campylobacter spp. isolated from retail raw meats in Iran. From August 2009 to August 2010, a total of 379 raw meat samples from camel (n?=?130), beef (n?=?207), and water buffalo (n?=?42) were purchased from randomly selected retail outlets in Chaharmahal va Bakhtiari and Khuzestan provinces in Iran. The samples were evaluated for the presence of Campylobacter using traditional bacteriological tests and a nested polymerase chain reaction. Overall, 31 of 379 meat samples (8.2%) were contaminated with Campylobacter. The highest prevalence of Campylobacter spp. was found in water buffalo meat (21.4%), followed by beef (9.2%), and camel (2.3%) meat. The most prevalent Campylobacter species isolated from meat samples was Campylobacter jejuni (77.4%); the remaining isolates were Campylobacter coli (22.6%). Susceptibilities of 31 Campylobacter isolates were determined for ten antimicrobial drugs using the disk diffusion assay. Of 31 Campylobacter isolates, 27 (87.1%) were resistant to one or more antimicrobial agents. Nine strains (29.0%) were resistant to one single antimicrobial agent, and eight strains (25.8%) showed resistance to two antimicrobial agents. Multidrug resistance was found in 32.3% of Campylobacter strains. Resistance to tetracycline was the most common finding (67.7%), followed by resistance to ciprofloxacin (32.7%), and nalidixic acid (32.7%). To the authors' knowledge, the present study is the first report of the isolation of Campylobacter spp. from raw water buffalo meat in Iran.     

Disk diffusion susceptibility testing ofHaemophilus influenzae using Haemophilus test medium

A three-center collaborative study was performed with the aim of determining the reproducibility of disk diffusion and broth microdilution susceptibility tests ofHaemophilus influenzae with 19 different antimicrobial agents using a newly described medium, Haemophilus Test Medium. The results of both methods were found to be highly reproducible. Using Haemophilus Test Medium, inhibitory zone diameters and MICs were then determined for 150 test strains ofHaemophilus influenzae, selected with an emphasis on known mechanisms of resistance. Regression analysis of zone diameter-MIC comparisons was used to define zone diameter interpretive criteria and MIC correlates for Haemophilus Test Medium disk diffusion tests performed withHaemophilus spp. for the following antimicrobial agents: ampicillin, amoxicillin/clavulanate, ampicillin/sulbactam, cefaclor, cefuroxime, cefamandole, ceftriaxone, cefotaxime, ceftizoxime, ceftazidime, cefixime, trimethoprim/sulfamethoxazole, rifampin, chloramphenicol, tetracycline, imipenem, aztreonam and ciprofloxacin.     

396株嗜麦芽窄食单胞菌的耐药特征研究

目的研究嗜麦芽窄食单胞菌的耐药特征。方法采用美国临床实验室标准化委员会（ＮＣＣＬＳ）推荐的纸片扩散法,测定了５年中初次分离的３９６株嗜麦芽窄食单胞菌对ＴＭＰ－ＳＭＺ,多西环素,替卡西林－克拉维酸等２０种抗生素的耐药特征,并对１０例嗜麦芽窄食单胞菌菌血症的治疗进行了分析。结果嗜麦芽窄食单胞菌对ＴＭＰ－ＳＭＺ,替卡西林－克拉维酸,多西环素,环丙沙星和头孢他啶的敏感率最高,分别为８１．０％,９１．０％,９６．０％,７０．７％和５３．８％,而对氨苄西林,氨苄西林－舒巴坦,阿莫西林－克拉维酸,头孢唑林,头孢克罗,头孢美唑,头孢呋辛,头孢噻肟,头孢曲松,氨曲南,亚胺培南高水平耐药,敏感率为（０．９～７．５）％。从替卡西林－克拉维酸,多西环素,ＴＭＰ－ＳＭＺ,环丙沙星和头孢他啶对嗜麦芽窄食单胞菌抑菌环直径分布累积百分率图看出：替卡西林－克拉维酸,多西环素,ＴＭＰ－ＳＭＺ和环丙沙星为活性最好的抗生素。结论替卡西林－克拉维酸,ＴＭＰ－ＳＭＺ和多西环素对所研究的嗜麦芽窄食单胞菌有较高的活性,系嗜麦芽窄食单胞菌菌血症严重感染治疗最有效的抗生素     

The status of antimicrobial resistance of Helicobacter pylori in eastern Europe

Objective   To evaluate the primary, secondary and combined resistance to five antimicrobial agents of 2340 Helicobacter pylori isolates from 19 centers in 10 countries in eastern Europe.
Methods   Data were available for centers in Bulgaria, Croatia, the Czech Republic, Estonia, Greece, Lithuania, Poland, Russia, Slovenia and Turkey. Susceptibility was tested by agar dilution (seven countries), E test (five countries) and disk diffusion (three countries) methods. Resistance breakpoints (mg/L) were: metronidazole 8, clarithromycin 1, amoxicillin 0.5, tetracycline 4, and ciprofloxacin 1 or 4 in most centers. Primary and post-treatment resistance was assessed in 2003 and 337 isolates respectively. Results for 282 children and 201 adults were compared.
Results   Primary resistance rates since 1998 were: metronidazole 37.9%, clarithromycin 9.5%, amoxicillin 0.9%, tetracycline 1.9%, ciprofloxacin 3.9%, and both metronidazole and clarithromycin 6.1%. Isolates from centers in Slovenia and Lithuania exhibited low resistance rates. Since 1998, amoxicillin resistance has been detected in the southeastern region. From 1996, metronidazole resistance increased significantly from 30.5% to 36.4%, while clarithromycin resistance increased slightly from 8.9% to 10.6%. In centers in Greece, Poland, and Bulgaria, the mean metronidazole resistance was slightly higher in adults than in children (39% versus 31.2%, P  > 0.05); this trend was not found for clarithromycin or amoxicillin ( P  > 0.20). Post-treatment resistance rates exhibited wide variations.
Conclusions   In eastern Europe, primary H. pylori resistance to metronidazole is considerable, and that to clarithromycin is similar to or slightly higher than that in western Europe. Resistance to amoxicillin, ciprofloxacin and tetracycline was detected in several centers. Primary and post-treatment resistance rates vary greatly between centers.     

Isolation and characterization of Campylobacter pyloridis from gastric biopsies

Gastric biopsy specimens were examined microbiologically and histologically for the presence of Campylobacter pyloridis. Of 51 randomly selected patients, 22 (43%) were found to harbor C. pyloridis in the gastric mucosa. The histologic demonstration of spiral organisms observed by staining with hematoxylin and eosin correlated well with microbiologic isolation of the organisms. There was a strong association (95.5%) between C. pyloridis in the gastric mucosa and histologically defined gastritis. However, there was no obvious association between C. pyloridis and ulcers. All C. pyloridis strains isolated exhibited uniform biochemical characteristics and had almost identical protein profiles, which indicated that they belong to a relatively homogeneous group distinct from other Campylobacter species. All C. pyloridis isolates were uniformly susceptible to ampicillin, amoxicillin, cephalothin, gentamicin, kanamycin, tetracycline, coumermycin, ciprofloxacin, novobiocin, clorobiocin, and nitrofurantoin. They were moderately resistant to nalidixic acid.     

Typing and Characterization of Mechanisms of Resistance of Shigella spp. Isolated from Feces of Children under 5 Years of Age from Ifakara, Tanzania

Eighty-six strains of Shigella spp. were isolated during the dry season from stool samples of children under 5 years of age in Ifakara, Tanzania. The epidemiological relationship as well as the antimicrobial susceptibility and mechanisms of resistance to ampicillin, chloramphenicol, and co-trimoxazole were investigated. Four different epidemiological tools, pulsed-field gel electrophoresis (PFGE), repetitive extragenic palindromic (REP)-PCR, plasmid analysis, and antibiogram, were compared for typing Shigella strains. Seventy-eight (90%) strains were Shigella flexneri and were distributed into four groups, by either PFGE or REP-PCR, with 51, 17, 7, and 3 strains. The four strains of Shigella dysenteriae belonged to the same group, and the four strains of Shigella sonnei were distributed in two groups with three and one strain each. Plasmid analysis showed a high level of heterogeneity among strains belonging to the same PFGE group, while the antibiogram was less discriminative. REP-PCR provided an alternative, rapid, powerful genotyping method for Shigella spp. Overall, antimicrobial susceptibility testing showed a high level of resistance to ampicillin (81.8%), chloramphenicol (72.7%), tetracycline (96.9%), and co-trimoxazole (87.9%). Ampicillin resistance was related to an integron-borne OXA-1-type beta-lactamase in 85.1% of the cases and to a TEM-1-type beta-lactamase in the remaining 14.8%. Resistance to co-trimoxazole was due to the presence of a dhfr Ia gene in all groups except one of S. flexneri, where a dhfr VII gene was found within an integron. Chloramphenicol resistance was associated in every case with positive chloramphenicol acetyltransferase activity. All strains were susceptible to nalidixic acid, ciprofloxacin, ceftazidime, cefotaxime, and cefoxitin. Therefore, these antimicrobial agents may be good alternatives for the treatment of diarrhea caused by Shigella in Tanzania.     

Antimicrobial resistance and prevalence of resistance genes in intestinal Bacteroidales strains

OBJECTIVE:

This study examined the antimicrobial resistance profile and the prevalence of resistance genes in Bacteroides spp. and Parabacteroides distasonis strains isolated from children''s intestinal microbiota.

METHODS:

The susceptibility of these bacteria to 10 antimicrobials was determined using an agar dilution method. β-lactamase activity was assessed by hydrolysis of the chromogenic cephalosporin of 114 Bacteriodales strains isolated from the fecal samples of 39 children, and the presence of resistance genes was tested using a PCR assay.

RESULTS:

All strains were susceptible to imipenem and metronidazole. The following resistance rates were observed: amoxicillin (93%), amoxicillin/clavulanic acid (47.3%), ampicillin (96.4%), cephalexin (99%), cefoxitin (23%), penicillin (99%), clindamycin (34.2%) and tetracycline (53.5%). β-lactamase production was verified in 92% of the evaluated strains. The presence of the cfiA, cepA, ermF, tetQ and nim genes was observed in 62.3%, 76.3%, 27%, 79.8% and 7.8% of the strains, respectively.

CONCLUSIONS:

Our results indicate an increase in the resistance to several antibiotics in intestinal Bacteroides spp. and Parabacteroides distasonis and demonstrate that these microorganisms harbor antimicrobial resistance genes that may be transferred to other susceptible intestinal strains.