Infectivity and resistance to antibiotics of bacterial strains isolated from patients hospitalised in intensive care units

The aim of this study was to evaluate the frequency of isolation and antimicrobial resistance testing of bacterial strains isolated from clinical specimens from patients hospitalized in three Intensive Care Units in Wroc?aw. The susceptibility of bacteria (107 strains) to selected antibiotics was determined. The results clearly show that non-fermentative rods were identified as the main agents causing pneumonia (58% of isolates). The second commonest pathogens were Gram-positive cocci (29%). The P. aeruginosa and E. cloacae strains were resistant to ampicillin, amoxicillin/clavulanate, cefuroxime and cefotaxime. All isolates of A. baumanii were susceptible only to imipenem. The rods of K. pneumoniae and E. coli were resistant to ampicillin, about 55% strains of both bacteria were sensitive to other antibiotics, except piperacillin/tazobactam, imipenem and ciprofloxacin. About 90% of methicillin resistant S. epidermidis strains were resistant to all antibiotics, except vancomycin (100% isolates were sensitive). ESBL were detected among E. cloace, K. pneumoniae and E. coli. We found P. aeruginosa rods producing MBL.     

Antibiotic resistance of staphylococci isolated from outpatients

The aim of the study was to determine susceptibility of 587 strains of S. aureus and 85 strains of coagulase-negative staphylococci isolated from outpatients in Poznań to co-trimoxazole, amoxycillin/clavulanic acid, erythromycin, gentamycin, doxycycline, ampicillin, oxacillin, cephradine, clindamycin and neomycin. Also methicillin-resistant strains were determined as well as strains ability to produce beta-lactamases. Susceptibility testing and examination of methicillin-resistant strains were performed by the disc diffusion techniques according to recommendation of NCCLS. Methicillin-resistant strains were additionally examined to their sensitivity to vankomycin and teicoplanin. beta-lactamase production was detected using nitrocefin impregnated discs and iodometric method. Amoxacillin/clavulanic acid, gentamycin, co-trimoxazole, cephradin, oxacillin and clindamycin occurred to be very active against both, S. aureus and coagulase-negative staphylococci. 84.7% to 100% of examined strains were sensitive to these drugs. Doxycyclin, erythromycin and ampicillin were less effective. Nine strains (1.5%) of 587 strains of S. aureus as well as 7 strains (8.7%) of coagulase-negative staphylococci were methicillin-resistant. All of methicillin-resistant strains were sensitive to vancomycin and teicoplanin. More than 75% of S. aureus and close to 50% of coagulase-negative staphylococci were able to produce beta-lactamases.     

临床常见病原性细菌对抗生素的耐药性分析

目的了解长春地区部分医院临床分离的致病菌对抗菌药物的耐药情况。方法收集吉林大学中日联谊医院和长春中医药大学附属医院临床分离的致病菌,采用K—B法进行抗生素敏感性试验,参照CLSI2009年版的标准判断结果。结果从这两家医院共分离细菌447株,其中革兰阴性菌353株,占78．9％,革兰阳性菌94株,占21．1％。肠杆菌科细菌对氨苄西林的耐药率在70％以上,对庆大霉素的耐药率超过了50％,但对亚胺培南保持较高的敏感性（耐药率〈5％）。金黄色葡萄球菌和表皮葡萄球菌对红霉素耐药率分别为65．2％和82．1％,对万古霉素的耐药率较低,分别为4．5％和3．6％。非发酵革兰阴性杆菌对头孢他啶的耐药率超过50％,铜绿假单胞菌对氨曲南的耐药率达到了62．9％,对他唑巴坦复合制剂、亚胺培南、美罗培南和阿米卡星较为敏感,而鲍曼不动杆菌对各类抗生素的耐药率都较高。结论细菌对抗生素的耐药性仍表现出增长趋势,加强细菌耐药性的检测,对于指导临床正确、合理使用抗生素,减少耐药菌的产生和传播具有重要意义。     

Resistance to antibiotics and heavy metals of Pseudomonas aeruginosa isolated from natural waters

The resistance patterns of Pseudomonas aeruginosa strains isolated from freshwater and seawater to different antimicrobial agents and heavy metals were studied. It was found that resistance in these environments is linked to the level of faecal pollution. All strains were resistant to ampicillin and tetracycline but sensitive to carbenicillin, amikacin, tobramycin, and colistin, and to the assayed concentrations of silver, cadmium, lead, and molybdenum. Resistance to gentamicin, sulphadiazine, mercury, arsenic, and chromium was variable, so their use as epidemiological markers was considered. There was a close relationship between the degree of pollution and the frequency of heavy metal resistant strains of Ps. aeruginosa. The highest frequencies of resistance to mercury and arsenic were obtained from marine environments with little faecal pollution, where the highest incidence of multi-resistant strains was also observed.     

Resistance to antibiotics and heavy metals of Pseudontonas aeruginosa isolated from natural waters

The resistance patterns of Pseudomonas aeruginosa strains isolated from freshwater and seawater to different antimicrobial agents and heavy metals were studied. It was found that resistance in these environments is linked to the level of faecal pollution. All strains were resistant to ampicillin and tetracycline but sensitive to carbenicillin, amikacin, tobramycin, and colistin, and to the assayed concentrations of silver, cadmium, lead, and molybdenum. Resistance to gentamicin, sulphadiazine, mercury, arsenic, and chromium was variable, so their use as epidemiological markers was considered. There was a close relationship between the degree of pollution and the frequency of heavy metal resistant strains of Ps. aeruginosa. The highest frequencies of resistance to mercury and arsenic were obtained from marine environments with little faecal pollution, where the highest incidence of multi-resistant strains was also observed.     

Time-kill study and synergistic activity of cell-wall inhibitor antibiotics in combination with gentamicin against Enterococcus faecalis and Enterococcus faecium

The synergy between gentamicin and vancomycin, teicoplanin, ampicillin and linezolid was studied by time-kill method. Two clinical vancomycin resistant enterococci (VRE) and two vancomycin susceptible enterococci (VSE) isolates were used. Different concentrations of antibiotics were combined. Two VSE strains and the control strain exhibited synergism with the combination of gentamicin, vancomycin, teicoplanin, ampicillin and linezolid. Two VRE strains exhibited synergism with the combination of gentamicin and ampicillin. Synergy between gentamicin and vancomycin, teicoplanin and linezolid was not observed against these isolates. The VRE isolates were positive for vanA, aac (6')-Ie aph (2") and aph (3')-IIIa genes and their vancomycin, teicoplanin and gentamicin MICs were 512 μg/ml, 512 μg/ml and >4000 μg/ml, respectively. In order to treat serious enterococcal infections, further clinical evaluation is needed to examine the in vitro combined effects of gentamicin and vancomycin, teicoplanin and linezolid.     

The sensitivity to 12 antibiotics of 125 strains of Streptococcus group B isolated in a maternity home

Sensitivity of 125 strains of group B streptococci isolated from newborns, their mothers and personnel in a maternity home was studied with respect to 12 antibiotics: benzylpenicillin, ampicillin, methicillin, cephalotin, erythromycin, lincomycin, levomycetin (chloramphenicol), oxacillin, tetracycline, streptomycin, gentamicin and ristomycin. The method of serial dilutions in a solid medium was applied. All the strains were sensitive to ristomycin and erythromycin. The predominating number of the strains were sensitive to lincomycin, levomycetin and the beta-lactam antibiotics. Strains resistant or moderately resistant to benzylpenicillin, ampicillin, oxacillin, methicillin and cephalotin were detected. The majority of the strains were resistant to streptomycin, tetracycline and gentamicin. Multiple antibiotic resistance with 2-7 determinants was revealed in 11.2 per cent of the strains. The antibiotic sensitivity of the strains isolated from the newborns, their mothers and the personnel in the maternity home was on the whole similar or insignificantly differed.     

Comparative Inhibition of Methicillin-resistant Strains of Staphylococcus aureus by Lysostaphin and Otner Antibiotics

Sixteen methicillin-resistant strains of Staphylococcus aureus obtained from Europe were found to be sensitive to the lytic activity of lysotaphin. With only minor exceptions, the strains were found to be sensitive to novobiocin, erythromycin, fusidic acid, and lincomycin, and slightly less sensitive to vancomycin and chloramphenicol. All strains were resistant to tetracycline, penicillinase-sensitive penicillins (benzylpenicillin, ampicillin, and propicillin), penicillinase-resistant penicillins (methicillin, nafcillin, ancillin, oxacillin, cloxacillin, and dicloxacillin), and two cephalosporin antibiotics (cephalothin and cephaloridine).     

Sensitivity spectrum of Francisella tularensis to antibiotics and synthetic antibacterial drugs

Sensitivity of 6 F. tularensis strains to 57 antibiotics and synthetic antibacterial drugs was studied. It was shown that the strains were highly sensitive to aminoglycosides, tetracyclines, anzamycins, quinolones, chloramphenicol, nitrofurantoin, nitroxoline, novobiocin and fusidin and resistant to penicillins, cephalosporins, polypeptides, vancomycin and sulfanylamides. The interrace differences in F. tularensis could be detected only by sensitivity to erythromycin, oleandomycin and spiramycin. There was observed no cross resistance to streptomycin and other aminoglycosides in F. tularensis. Assay of F. tularensis sensitivity to antibacterial drugs of various groups with the rapid photometric procedure and the agar diffusion method revealed that the results were highly comparable.     

Sensitivity to antibiotics of Clostridium difficile toxigenic nosocomial strains

Clostridium difficile is the etiological agent of diarrhoea and colitis, especially in elderly patients. The incidence of these diseases has increased during the last 10 years. Emergence of so-called hypervirulent strains is considered as one of the main factors responsible for the more severe disease and changed profile of sensitivity to antimicrobial agents. The aim of this work was to determine the sensitivity profile of toxigenic strains of C. difficile in the Czech Republic in 2011–2012 to selected antibiotics. The antibiotics clindamycin, metronidazole, vancomycin and amoxicillin with clavulanic acid were used for this purpose. Isolates cultured on Brazier's C. difficile selective agar were analysed for the presence of toxin genes using Xpert detection system. Xpert analysis revealed that 33 strains carried the genes for toxins tcdB, cdt and tcdCΔ117, thus showing characteristics typical for the hypervirulent ribotype 027/PFGE type NAP1/REA type B1. The remaining 29 strains carried only the gene for toxin B (tcdB) and not cdt and tcdCΔ117. Our results indicate the higher susceptibility of C. difficile hypertoxigenic strains to three out of four tested antibiotics (except vancomycin) than it is for the other toxigenic strains. We found that only 10.34 % of other toxigenic strains were resistant to clindamycin, and no resistance was found in all other cases. All the isolates were sensitive to amoxicillin/clavulanic acid in vitro. However, its use is not recommended for therapy of infections caused by C. difficile.     

Sensitivity of the causative agent of tularemia to antibiotics

Sensitivity of the tularemia causative agent of different geographical races to antibiotics such as streptomycin, tetracycline, gentamicin, rifampicin (20 strains), ampicillin, polymyxin M, erythromycin, oleandomycin (361 strains) and lincomycin (294 strains) was studied. High sensitivity of the tularemi a microbe to streptomycin, tetracycline, rifampicin (MIC of 10 gamma/ml), gentamicin (MIC of 1 gamma/ml) and resistance to 50 gamma of ampicillin and 1000 gamma/ml of polymyxin M were found. Combined use of 50 gamma of ampicillin and 100 gamma/ml of polymyxin M added to the nutrient medium for growth inhibition of the foreign flora on isolation of the tularemia causative agent from the infected material including stable laboratory animal carcases was recommended. Marked differences in sensitivity of the strains of different geographical races to the macrolides and lincomycin were observed. The strains of the non-Arctic and Central Asiatic races were of low resistance to the above drugs (the MIC of erythromycin, oleandomycin and lincomycin were 10--50, 50--400 and 25--100 gamma/ml respectively. Within the holarctic race 40 per cent were low resistant and 60 per cent were highly resistant to these drugs. The above drugs should not be used for treatment of tularemia cases.     

Escherichia coli strains isolated from surface waters. Distribution by resistance to antibiotics and R-plasmid transfer

Samples were taken from surface waters in Csongrád county in the months March through December, 1980. Escherichia coli isolates selected at random were tested for resistance to 5 antibiotics and for R-plasmid carriership. Of the strains isolated from Tisza river at each of 8 sampling sites, 50-60% were sensitive to all the 5 antibiotics. The percentage of sensitivity was much lower if only the strains isolated during the summer months, when the water level was high, or those isolated from affluents and backwaters were taken into account. The frequency of resistance was the highest for tetracycline, followed in order by ampicillin, streptomycin, kanamycin and chloramphenicol. R-plasmid was carried by 43% of the resistant isolates tested, mainly by multiresistant ones.     

Susceptibility to selected chemotherapeutics of Staphylococcus aureus strains resistant to methycyline isolated from clinical materials in the years 1991-1992 and 1997

The susceptibility to selected chemotherapeutic agents was determined in 100 strains of Staphylococcus aureus methicillin-resistant (MRSA) isolated from clinical materials in 1991-1992 (50 strains) and in 1997 (50 strains). Two methods were used for the determination: disc method and antibiotic dilution in agar. The minimal inhibitory concentration (MIC) was determined for vancomycin, teicoplanin, furazolidone, nitrofurantoin, ofloxacin, gentamicin, netilmicin and trimethoprim. The concentrations of the chemotherapeutics in the substrate ranged from 0.125 to 512 mg/l. The obtained results served for drawing of the following conclusions: all studied MRSA strains isolated in 1991-1992 and in 1997 were sensitive to glycopeptide antibiotics: vancomycin and teicoplanin, to nitrofurans: nitrofurantoin and furazolidone, and to fusidic acid. MRSA strains isolated in 1991-1992 were sensitive to ofloxacin, but in 1997 about 80% of the strains were resistant to that antibiotic, and this resistance was noted in S. aureus strains with homogeneous resistance to methicillin. Increasing frequency of resistance to mupirocin was found, in 1991-1992 4% of the strains were resistant, and in 1997 the resistance of MRSA to that antibiotic was found in 12%. No changes occurred in the sensitivity of staphylococci to trimethoprim/sulfamethoxazole (cotrimoxazole). About 94% of strains in 1991-1992 and 1997 were sensitive to that drug. The sensitivity to cotrimoxazole is connected with one of its components (trimethoprim), with 94% of MRSA strains sensitive to it.     

Sensitivity of Shigella to antibiotics]

Three hundred and twenty two Shigella cultures isolated from dysentery patients within 1986-1989 were tested with the use of standard paper disks for their sensitivity to levomycetin, streptomycin, tetracycline, monomycin, neomycin, kanamycin, erythromycin, gentamicin, carbenicillin, ampicillin, oxacillin, methicillin and doxycycline. The number of the cultures belonging to Shigella sonnei amounted to 85.1 per cent of the total number of the strains studied. 91.9, 89.5, 87.3, 87.3, 80.1 and 80.1 per cent of the cultures were sensitive to gentamicin, kanamycin, carbenicillin, neomycin, levomycetin and ampicillin, respectively. 99.4 per cent of the isolates were resistant to streptomycin and 97.2 per cent were resistant to tetracycline. The sensitivity to erythromycin remained rather high (70.2 per cent). The overwhelming majority of the Shigella sonnei isolates had multiple resistance.     

Incidence of resistance to tetracycline,chloramphenicol and ampicillin amongSalmonella species isolated in The Netherlands in 1965 and 1966

In 1965 and 1966 respectively 9628 and 10467Salmonella strains were screened for resistance to tetracycline and chloramphenicol. In 1965 the major half of the strains were also tested for ampicillin resistance and in 1966 all strains passed this test. In 1965 20.9% and in 1966 21.7% were found resistant, mainly to tetracycline. The incidence of resistance to chloramphenicol remained low (less than 1%). By far the majority of the resistant strains belonged toS. typhi murium andS. panama. The rate of resistance in the former organism remained nearly equal to that observed in 1963 – 1964, whereas inS. panama it has diminished.Ampicillin-resistant strains were found in as many as 23 different types ofSalmonella. In 8 types in which ampicillin resistance was found, only animal strains were concerned. These findings may represent cases of primary ampicillin resistance. In the human strains ofSalmonella the incidence of ampicillin resistance increased from 11.6% in 1965 to 15.3% in 1966.     

Susceptibility to antibiotics of bacteria from genera Micrococcus,Kocuria, Nesterenkonia,Kytococcus and Dermacoccus

Two hundred and nineteen strains from genera Micrococcus, Kocuria, Nesterenkonia, Kytococcus and Dermacoccus isolated from different sources, such as saliva, skin of palm and forearm and from vestibule of nose were tested. The susceptibility to doxycycline, cetriaxone, cefuroxyme, amikacyne, amoksycillin with clavulanic acid, trimethoprim/sulfamethoxazole, ampicillin, ciprofloxacin, penicillin and erythromycin were estimated. In general, bacteria from these genera are sensitive to most of selected antibiotics. Most of the strains showed resistance to ampicillin and erythromycin. None of these strains produced beta-lactamases. In infectious caused by bacteria from genera Micrococcus, Kocuria, Nesterenkonia, Kytococcus and Dermacoccus in clinical treatment should be used amoksycillin with clavulanic acid, doxycycline, cetriaxone, cefuroxyme, or amikacine because, with one's own range of activity embrace highest percentage of investigated strains.     

142例儿童感染肺炎链球菌的耐药性分析

目的分析儿科病房的肺炎链球菌的主要分布情况以及耐药现状。方法收集宁波市妇女儿童医院儿科病房2010年1月1日至2012年12月31日临床分离的142株肺炎链球菌,采用法国生物梅里埃公司的VITEK-60型全自动微生物分析仪进行菌株鉴定。采用纸片扩散法（K—B法）做药敏试验,用参考菌株做质量控制。药敏试验结果按NCCL2002版判断标准,对照参考菌株判断敏感,中介和耐药。结果分离的142株肺炎链球菌的送检科室以呼吸科最多62株,其次是小儿监护病房21株,新生儿科送检标本中未培养出肺炎链球菌。分离的142株肺炎链球菌的标本以痰液标本最多103株。分离的142株肺炎链球菌对克林霉素,红霉素的耐药率分别为98．5％和95．07％且呈现逐年上升;对氨苄西林、氨苄西林舒巴坦钠、头孢呋辛、头孢曲松和万古霉素的敏感率分别为84．51％、89．44％、93．66％、97．89％和100％。结论本地区住院儿童的肺炎链球菌来源仍以呼吸道为主,对广谱半合成青霉素仍较敏感,对β-内酰胺酶抑制剂的广谱半合成青霉素敏感率更高,对头孢类敏感率更高,未发现对万古霉素耐药菌株。在门急诊可选用广谱半合成青霉素作为治疗肺炎链球菌的首选用药,在病房可选用敏感性更高的头孢呋新或头孢曲松治疗肺炎链球菌．但为了延缓耐药性的产生,应动态监测肺炎链球菌的耐药情况,合理选择抗生素,提高疗效。     

Beta-lactamase activity of bacteria of the genus Proteus]

beta-Lactamases of Proteus and their role in the mechanism of the microbe resistance to penicillins and ceporin were studied. It was found that the beta-lactamase of Proteus had low activity and were produced by both beta-lactamide resistant and sensitive clinical strains of Proteus. The resistant cultures of Proteus produced enzymes more frequently (3.4--5 times) than the sensitive ones. The synthesis of beta-lactamase in the clinical Proteus strains was inducable. The high induction coefficient was achieved only in the presence of high concentrations of the inductor. No significant dependence of the culture sensitivity level of ampicillin and ceporin on the induction level was observed. The most significant part of the constitutive enzyme in Proteus was intracellular, while that of the inducable enzyme was extracellular. No correlative dependence between the culture resistance levels to penicillins and ceporin and the enzyme activity was noted. The beta-lactamase activity was not found in the transconjugants with the in vitro acquired R-factor controlling the ampicillin and ceporin resistance, as well as in the resistant mutants selected on the media with increasing concentrations of the above antibiotics. Induction of beta-lactamase synthesis was not found in these strains either. The ability of Proteus to synthesize beta-lactamase can be lost on the strain storage under laboratory conditions which was not always accompanied by reduction of the culture sensitivity to ampicillin and ceporin. The enzymatic destruction of beta-lactamides was not the main mechanism of Proteus resistance to the above antibiotics.     

Typhoid fever: facing the challenge of resistant strains

The introduction of chloramphenicol in 1948 revolutionised the outcome of typhoid fever but chloramphenicol-resistant strains of Salmonella enterica serotype Typhi were reported just two years later. Resistance followed also the introduction of ampicillin and co-trimoxazole. During the second half of the 1980s, strains resistant to the three first-line antimicrobial agents, chloramphenicol, ampicillin and co-trimoxazole emerged and spread rapidly throughout the Indian subcontinent and South East Asia. During the 1990s when fluoroquinolones had become a first-line treatment for typhoid fever, these multi drug resistant (MDR) strains acquired an additional resistance to nalidixic acid with decreased susceptibilities to ciprofloxacin (CIPDS) (MIC range, 0.125-1 mg/l). Considerable data have now accumulated to suggest that infections due to CIPDS strains may not respond satisfactorily to therapy with ciprofloxacin or ofloxacin. Furthermore, identification of such CIPDS strains in clinical laboratories is not easy without determination of MIC of ciprofloxacin. Recently, several isolates highly resistant to ciprofloxacin or to extended-spectrum cephalosporins of Asian origin have been reported.     

Sensitivity of Yersinia enterocolitica to antibiotics]

Sensitivity of 33 foreign and 10 native strains of Y. enterocolitica to tetracycline, aminoglycosides, penicillins, levomycetin and polymyxin was studied. All the strains proved to be resistant to penicillin, oxacillin and ampicillin: they produced penicillinase. The level of resistance to penicillin did not always correlate with penicillin activity. The ability of the native strains to acquire R-factor in vitro from Coli bacteria was shown.