Prevalence, distribution and characterisation of ceftiofur resistance in Salmonella enterica isolated from animals in the USA from 1999 to 2003

Third-generation cephalosporin (3GC) antimicrobials are the drugs of choice for treatment of salmonellosis in children. Salmonella isolated in the USA are assayed by the National Antimicrobial Resistance Monitoring System (NARMS) for resistance to antimicrobials including first-, second- and third-generation cephalosporins. From 1999 to 2003, 34,411 Salmonella were isolated from animals in the USA, of which 10.9% were found to be resistant to ceftiofur, a 3GC used in animals, whilst only 0.3% were resistant to ceftriaxone, a 3GC used in human medicine. Ceftiofur resistance rose from 4.0% in 1999 to 18.8% in 2003. Isolates from diagnostic laboratories had higher levels of resistance (18.5%), whereas levels in isolates from on-farm (3.4%) and slaughter (7.1%) sources were lower. Animals with a higher than average proportion of resistant Salmonella included cattle (17.6%), horses (19.2%) and dogs (20.8%). Levels in turkeys (6.8%), chickens (7.1%), eggs (3.6%) and swine (4.6%) were lower. Resistance varied between Salmonella serotypes. A few serotypes had significantly high levels, e.g. S. Newport was 70.4% ceftiofur resistant. Resistance was predominantly associated with bla(CMY-2)-encoding plasmids. These data suggest that the acquisition of resistance plasmids and the spread of specific serotypes harbouring these plasmids are driving the observed resistance to ceftiofur in Salmonella animal isolates.     

Antimicrobial resistance of Salmonella enterica group C strains isolated from humans in Turkey, 2000-2002

Fifty-three Salmonella enterica group C isolates obtained from various human samples (47 stool, 4 blood and 2 urine) in ten provinces of Turkey between 1 July 2000 and 30 June 2002 were serotyped and resistance to antimicrobials was investigated by agar dilution tests. The isolates were identified as S. Choleraesuis (11), S. Hadar (7), S. Irumu (4), S. Virchow (3), S. Tallahassee (3), S. Paratyphi C (2), S. Braenderup (2), S. Othmarschen (2), S. Menston (2), S. Concord (2), S. Infantis (2), S. Kottbus (2), S. Edinburg (1), S. Oranienburg (1), S. Muenchen (1) and S. Malmoe (1). Antimicrobial resistance rates of S. enterica groups C1 and C2 were high for ampicillin (26% and 60%, respectively), amoxicillin/clavulanic acid (11% and 40%), chloramphenicol (16% and 27%) and tetracycline (3% and 40%). The percentages of strains sensitive to all antimicrobials were 58% and 33%, respectively. Multiresistance was not observed in group C1 isolates, but the rate of multiresistant isolates was 13% in group C2. The rate of decreased ciprofloxacin susceptibility (CipL) was 61% in serogroup C1 and 20% in serogroup C2. These results indicated that S. enterica group C infections in humans were not infrequent in Turkey and that multiple antimicrobial resistance was common within these strains.     

Antibiotic resistance among enterococcal strains isolated from clinical specimens

The distribution and resistance patterns of clinical isolates of enterococci from hospital patients were compared with those obtained from outpatients. Of 235 enterococcal isolates 212 (90.2%) were identified as Enterococcus faecalis and 23 (9.8%) as E. faecium. E. faecium occurred more frequently in specimens from hospitalized patients than from outpatients (P < 0.001). Over 90% of all E. faecalis isolates were susceptible to ampicillin. Resistance to ampicillin occurred in 66.7% of hospital strains of E. faecium. High-level resistance to gentamicin (MIC > 500 mg/l) was seen in 37.03% of inpatients' and in 11.5% of outpatients' E. faecalis isolates and in 76.2% of hospital isolates of E. faecium. High-level streptomycin resistance (MIC > 2000 mg/l) occurred in 52.8% of E. faecalis and 76.2% of E. faecium hospital isolates. There were no isolates resistant to vancomycin. The community acquired strains isolated from outpatients were more susceptible than isolates from hospitalized patients to all antimicrobial agents tested.     

Primary resistance to clarithromycin in clinical strains of Helicobacter pylori isolated from children in Poland.

Helicobacter pylori resistance to clarithromycin is an important factor in the failure of eradication therapy. The resistance results from point mutations in the 23S rRNA gene of H. pylori. The prevalence of primary resistance of H. pylori to clarithromycin in children and mutations associated with resistance were studied and it was found that 23.5% (23/98) of H. pylori strains isolated in our hospital during 1998-2000 were resistant to clarithromycin. The primary resistance was mainly caused by an A2143G mutation, but the isolates with an A2142G mutation had higher MICs for clarithromycin compared with those with an A2143G mutation: median MIC 256 versus 16 mg/l. Comparison of our data with previous results showed that the prevalence of H. pylori resistance to clarithromycin in children has increased in Poland over the last three years, however the difference was not significant (23.5 vs. 17%, P=0.22).     

393例儿童感染铜绿假单胞菌耐药性分析

目的了解湖南省儿童医院临床分离的铜绿假单胞菌感染分布及耐药情况。方法回顾性分析该院2010年1月至2010年12月住院患儿的各类临床标本中分离出的铜绿假单胞菌分布情况及其对16种抗菌药物的耐药情况。结果共分离出铜绿假单胞菌393株,主要来源于痰及咽拭子、血液;集中在心血管内科、急诊综合科、新生儿科、感染科、重症监护科等;对氨苄西林、头孢唑啉、氨苄西林-舒巴坦、呋喃妥因等不敏感,敏感率均<10%,对头孢吡肟、哌拉西林-他唑巴坦、氨曲南、环丙沙星、左氧氟沙星、美罗培南等耐药率较低,耐药率均<10%。结论铜绿假单胞菌是医院感染的主要病原菌之一,耐药形势严峻;应高度重视重点病区感染流行的监测及消毒工作,结合药敏试验结果,合理使用抗菌药物。     

Trends in antimicrobial drug resistance in Salmonella enterica serotypes Typhi and Paratyphi A isolated in Europe, 1999-2001

Results of antimicrobial sensitivity tests for strains of Salmonella enterica serotypes Typhi and Paratyphi A isolated from patients in ten European countries between 1999 and 2001 have been transferred electronically to the Enter-net surveillance hub. For Typhi between 22 and 29% of isolates were multiresistant (to four drugs or more) with decreased susceptibility to ciprofloxacin (MIC 0.25-1.0 mg/l) increasing from 20% in 1999 to 26% in 2001. Nineteen of 169 (11%) strains with decreased ciprofloxacin susceptibility were sensitive to nalidixic acid. For Paratyphi A multiple resistance increased from 9% in 1999 to 25% in 2001 and decreased ciprofloxacin susceptibility from 6 to 17%. Clinicians should be aware of the possibility of treatment failures when fluoroquinolones are used as the first-line drug for infections with Typhi and Paratyphi A, particularly for patients recently returning from areas where drug-resistant strains are endemic.     

Drug resistance patterns in Salmonella enterica subspecies enterica serotype Typhi strains isolated over a period of two decades,with special reference to ciprofloxacin and ceftriaxone

Fluoroquinolone-resistant Salmonella enterica subspecies enterica serotype Typhi are being increasingly reported from the Asian subcontinent. This has been hypothesised to be due to a double mutation in the gyrA gene. A total of 113 S. Typhi strains isolated during 1987–2006 in a tertiary-level hospital of North India were monitored for their antibiotic susceptibility by the disk diffusion and minimum inhibitory concentration (MIC) methods. The study period was arbitrarily divided into four equal parts, each comprising 5 years. The antibiotics tested showed an extremely wide range of MICs during all four periods except for ceftriaxone, which showed no resistance during the study period. However, a gradual increase in the MIC of this drug was observed, i.e. 0.047 mg/L, 0.098 mg/L, 0.211 mg/L and 0.3652 mg/L during the four study periods. Ninety-one percent of the strains isolated in the final study period were observed to have MIC levels ≥0.125 mg/L to ciprofloxacin. Furthermore, gyrA restriction analysis showed no mutation at the two reported sites of the gene, suggesting that the double mutation theory in the development of ciprofloxacin resistance may not be the only mechanism responsible for fluoroquinolone resistance.     

Antibiotic resistance of bacterial strains isolated from children in Child Health Center, Warsaw

This study examines the antibiotic susceptibility of 1792 bacterial strains isolated from hospitalized children between January and December 1993. A total of 1015 Gram-negative rods represented by members of Enterobacteriaceae family (770) and nonfermenters (245) were isolated. The most resistant strains were noticed among Klebsiella pneumoniae and Enterobacter cloacae. From 38% to 46% of K. pneumoniae strains were resistant to third-generation cephalosporins, but all of them were sensitive to imipenem. From 60% to 80% of E. cloacae isolates were resistant to all beta-lactams, but sensitive to imipenem. Resistance of P. aeruginosa to aminoglycosides varied from 30% for gentamicin to 5% for amikacin. About 40% of P. aeruginosa strains were resistant to carbenicillin, and 25% to azlocillin and piperacillin, but only two strains were resistant to ceftazidime and imipenem. Among Gram-positive cocci the most frequently encountered were coagulase-negative staphylococci, followed by Staphylococcus aureus and Enterococcus faecalis. The methicillin-resistant strains of coagulase-negative staphylococci and S. aureus consisted 74.8% and 34%, respectively. All strains of methicillin-resistant coagulase-negative staphylococci and S. aureus were sensitive to vancomycin.     

Salmonella enterica isolated from infections in Australian livestock remain susceptible to critical antimicrobials

Salmonella enterica is a zoonotic pathogen causing a variety of diseases in humans and animals. Many countries are reporting an increase in the prevalence of multidrug-resistant (MDR) S. enterica in food animals. The aim of this study was to determine whether S. enterica isolated from livestock in New South Wales, Australia, have similar resistance traits to those reported internationally. Salmonella enterica (n = 165) from clinical infections in food animals between 2007 and 2011 were serotyped and tested for susceptibility to 18 antimicrobials. Also, 22 antimicrobial resistance genes (ARGs), 3 integrons and 18 plasmid replicon types were screened for using PCR. Most isolates (66.1%) remained susceptible to all antimicrobials; 8.5% of the isolates were resistant to four or more antimicrobials. Antimicrobials with the highest prevalence of resistance were sulfafurazole (28.5%), ampicillin (17.0%), tetracycline (15.8%) and trimethoprim (8.5%). There was no resistance to fluoroquinolones or third-generation cephalosporins. The most common ARGs were bla_TEM (15.2%), sul2 (10.3%), tetB (9.1%), tetA (5.5%), aphA1 (4.8%) and dhfrV (4.8%). Class 1 integrons (7.9%) and IncFIIA (69.7%) were the most commonly detected integron and plasmid replicon types, respectively. Class 1 integrons were positively associated with MDR phenotypes and ARG carriage (P ≤ 0.001). Internationally prominent MDR serovars associated with severe disease in humans (e.g. AmpC-positive Salmonella Newport) were not detected. Overall, the comparatively favourable resistance status of S. enterica in Australian livestock represents minimal public health risk associated with MDR strains and supports a conservative approach to the registration of antimicrobial drug classes in food-producing animals.     

上饶地区淋病奈瑟菌临床耐药性分析

目的了解上饶地区近年淋病奈瑟菌(NG)的耐药特点及产β-内酰胺酶淋病奈瑟菌(PPNG)的流行状况,为本地区淋病治疗合理选用抗生素提供指导。方法采用K-B琼脂扩散法,测定临床分离鉴定的NG对8种常用抗生素的敏感性;应用硝基噻吩显色法检测PPNG。结果 116株NG对8种抗生素的耐药率从高到低依次为:氧氟沙星(91.4%)、四环素(83.6%)、氨苄青霉素(55.2%)、头孢噻吩(18.9%)、头孢呋辛(12.0%)、头孢噻肟(7.8%)、头孢曲松(6.9%)和大观霉素(4.3%);检测出PPNG54株(46.6%)。结论氧氟沙星、四环素和氨苄青霉素不宜作为本地区淋病治疗药物,大观霉素和第三代头孢菌素可作为首选药物,但要加强耐药性检测。     

中国西部地区老年患者临床分离菌的耐药及分布特点

目的 了解中国西部地区10所医院2016—2017年老年患者临床分离菌的分布特点及其对抗菌药物的耐药性。方法 按统一方案,采用纸片扩散法或自动化仪器法进行细菌药敏试验,按照美国临床和实验室标准化协会(Clinical and Laboratory Standards Institute,CLSI)2017年标准判读结果。结果 共收集临床分离菌121374株,其中老年患者41448株,占34.1%。其中革 兰阳性菌9499株,占22.9%;革兰阴性菌31949株,占77.1%。耐甲氧西林金黄色葡萄球菌(MRSA)和耐甲氧西林凝固酶阴性葡萄 球菌(MRCNS)的检出率分别为37.1%和79.3%。未发现万古霉素、替考拉宁和利奈唑胺耐药葡萄球菌。除四环素、克林霉素和利 奈唑胺外,屎肠球菌对其他抗菌药物耐药率均高于粪肠球菌;两者中均有少数万古霉素、替考拉宁和利奈唑胺耐药株,耐药率 均＜3%。碳青霉烯类抗生素依然对肠杆菌科细菌保持良好的抗菌活性,耐药率均＜10%。肺炎克雷伯菌对亚胺培南、美罗培南 的耐药率分别为7.1%和9.9%,比2011年明显升高。铜绿假单胞菌对亚胺培南和美罗培南的耐药率分别为18.9%和17.8%。鲍曼不 动杆菌对亚胺培南和美罗培南的耐药率均＞60%,高于全国平均水平(60.0%,2016年)。结论 老年患者临床分离菌的耐药及分 布特点不同于全国平均水平。经验用药应参考老年人群耐药监测数据,根据药敏试验结果合理选用抗菌药物。     

Characterisation of antimicrobial resistance patterns and class 1 integrons among Escherichia coli and Salmonella enterica serovar Choleraesuis strains isolated from humans and swine in Taiwan

Escherichia coli isolates from humans (n=110) and swine (n=61) and Salmonella enterica serovar Choleraesuis isolates (n=95) from swine in southern Taiwan were characterised for antimicrobial resistance patterns and class 1 integrons. All E. coli isolates and S. Choleraesuis isolates were multidrug resistant and demonstrated high resistance to beta-lactams, aminoglycosides, tetracycline, sulfonamides, spectinomycin, chloramphenicol and nalidixic acid. By polymerase chain reaction and DNA sequencing, 104 (61%) E. coli isolates and 31 (33%) S. Choleraesuis isolates were found to carry class 1 integrons. The gene cassette array dfrA12-orfF-aadA2 was the most prevalent (24%) among the human and swine E. coli isolates, whilst the gene cassette array dfrA12-orfF-aadA2-sul1 was the most prevalent (24%) among S. Choleraesuis strains. For E. coil isolates, all class 1 integrons were located on conjugated plasmids. Meanwhile, human and swine E. coli isolates carrying identical gene cassettes were genetically unrelated. Our results revealed that multidrug resistance and class 1 integrons were widely present in E. coli and S. Choleraesuis isolates obtained in Taiwan and that class 1 integrons might play an important role in contributing to the horizontal transfer of antimicrobial resistance.     

Molecular analysis of multiresistant porcine Salmonella enterica subsp. enterica serovar Bredeney isolates from Southern Brazil: identification of resistance genes, integrons and a group II intron

The relationships of 83 porcine Salmonella enterica subsp. enterica serovar Bredeney isolates obtained at two slaughterhouses in Southern Brazil were analysed by XbaI and BlnI macrorestriction analysis, plasmid profiling and determination of antimicrobial resistance patterns. Twenty-nine XbaI and 30 BlnI macrorestriction patterns were identified. The 72 plasmid-bearing isolates exhibited 20 different plasmid profiles. Multiresistance was detected in 49 isolates (59%), of which 39 isolates showed at least resistance to sulfonamides, tetracyclines, chloramphenicol, streptomycin, kanamycin and/or ampicillin. A representative subset of 12 isolates was chosen for identification of resistance genes, their localisation and transferability. The sulfonamide resistance genes sul1, sul2 and sul3, the tetracycline resistance genes tet(A) and tet(B), the phenicol resistance genes catA1 and floR, the streptomycin resistance gene strA, the kanamycin resistance gene aphA1 and the ampicillin resistance gene bla_TEM were detected and found to be located most frequently on plasmids. In addition, class 1 and 2 integrons with the cassette arrangements dfrA21/bla_OXA-129/aadA1 and dfrA1/sat1/aadA1, respectively, were detected. A group II intron was found to be inserted into the 59-base element of an aadA1 gene cassette in a class 1 integron. This study revealed a wide genomic variety among the S. Bredeney isolates, and the high number of multiresistant isolates may point towards the risks that these S. Bredeney isolates can represent to human health.     

Antimicrobial susceptibility phenotypes, resistance determinants and DNA fingerprints of Salmonella enterica serotype Typhimurium isolated from bovine in Southern Japan

A longitudinal study was conducted in cattle to determine the antimicrobial resistance phenotypes, integron elements, resistance genes and pulsed-field gel electrophoresis fingerprints among Salmonella enterica serotype Typhimurium isolates. A total of 33 strains were isolated and categorised into Groups A, B and C during the period 1989-2004. Thirty-one strains (93.9%) showed resistance to ampicillin (A) encoded by bla(OXA-1), bla(TEM) and bla(PSE-1) genes; 84.8% showed resistance to chloramphenicol (C) encoded by floR and catA1; 97.0% were resistant both to streptomycin (S) and sulfamethoxazole (Su), the former encoded by aadA1 and aadA2; 100% were resistant to oxytetracycline (T) encoded by tetA, tetB and tetG; and 42.4% were resistant to kanamycin (Km) encoded by aphA1-Iab. Multidrug resistance types observed were ACSSuT-Km (n=13), ACSSuT (n=15), ASSuT (n=3) and SSuT (n=2). Class 1 integrons ranging from 1.0 kb to 1.9 kb were detected from 54.5% of isolates (18/33). Integrons were not detected initially (1989-1992), then during the 1993-1996 interval a high frequency of 1.0 kb and 1.2kb amplicons were detected and during 2000-2004 the amplicon size increased to 1.7 kb and 1.9 kb. We report evidence of additional integration of resistance gene cassettes as shown by integrons with increased size. Finally, group B strains showed banding patterns indistinguishable from S. Typhimurium DT104 reference strain, indicating that the DT104 lineage existed on the island since 1993.     

Antibiotic susceptibility of bacterial strains isolated from patients with community-acquired urinary tract infections.

Isolates from urine samples obtained during 1999 were identified and their susceptibility to antimicrobial agents studied along with any production of extended-spectrum beta-lactamases (ESBL) by Escherichia coli and Klebsiella pneumoniae. A total of 13774 samples were analysed using an automatic system for the detection of bacterial ATP (Coral, USA). Of these samples, 49% were reported to be positive and uncontaminated; bacteria most frequently isolated were E. coli (47%), Proteus mirabilis (7%), Enterococcus faecalis (6%) and K. pneumoniae (5%). The susceptibility studies showed 37% E. coli strains resistant to amoxycillin+clavulanate 33% to cotrimoxazole and 22% to ciprofloxacin. Seven strains of E. coli produced ESBL. Thirteen per cent of strains were resistant to cefuroxime but only (1%) to fosfomycin. Resistance to nitrofurantoin in K. pneumoniae was 38%. P. mirabilis showed 52% resistance to cotrimoxazole and 13% Staphylococcus aureus, were methicillin-resistant. E. faecalis did not show any special resistance to normal medication. Fosfomycin continued to show high activity against Gram-negative bacilli. However, enterococci, some species of staphylococci and yeasts were difficult to treat empirically. ESBL were detected in the isolates of E. coli and there were some methicillin-resistant strains of S. aureus.     

Emerging resistance in Salmonella enterica serotype Typhi in Hong Kong

A total of 182 Salmonella enterica serotype Typhi isolated from three hospitals in Hong Kong from 1986 to 1992 were tested for their susceptibility to 21 antimicrobial agents. Four percent or less were resistant to chloramphenicol, ampicillin, some of the cephalosporins, nalidixic acid, tetracycline and trimethoprim and 6% to 1024 mg/l sulfamethoxazole. All were susceptible to the aminoglycosides and the 4-quinolones. Nineteen isolates were resistant to at least 1, and up to 9, antibiotics. Of 8 chloramphenicolor multiply-resistant isolates studied, only 3 could transfer their resistances while resistance of one could only be mobilized. Four of 5 ampicillin-resistant strains produced a beta-lactamase of pI 5.5. Antibiotic resistances were mediated by plasmids of 106, 116 or 221 kb of incompatibility groups H, I1 and K. Three resistant isolates did not harbour any plasmid. A total of 43 (24%) S. Typhi harboured plasmids ranging in size from 4.3 to 221 kb. Plasmids of 106 kb and 8.5 kb were found in 17 and 10 isolates, respectively. Restriction enzyme digestion of these two plasmids showed that each could be differentiated into 3 types. Of 89 isolates that were phage typed, 38% were untypable, while 17% and 12% were of phage types E1 and A, respectively, and the rest belonged to 17 other types.