Antibiotic susceptibility of Bacteroides fragilis group strains in Hungary

Resistance rates to different antibiotics of 495 Bacteroides fragilis group strains were followed between 1987 and 1994 in Hungary. In 1992 the strains were collected in three different laboratories, whereas during the other periods strains were isolated in one centre. Metronidazole, chloramphenicol, imipenem and amoxicillin/clavulanic acid were the most active drugs. A high level of resistance was observed in 1987 for ampicillin (88% at > 4 mg/L), erythromycin (51% at > 4 mg/L), tetracyclin (53% at > 8 mg/L) and clindamycin (27% at > 4 mg/L). The same level of resistance was seen during the further years for clindamycin and ampicillin. Resistance to cefoxitin increased from 6% to 11% between 1987 and 1993/1994. No differences in resistance rates were observed between the strains collected in the three centers. For 100 strains, the results of the E test were compared with those of the micro-broth dilution test, both being used routinely for testing the antibiotic susceptibility of Bacteroides fragilis group strains in this period.     

Resistance to antibacterial drugs of Enterobacteriaceae isolated from healthy children and from those with Salmonella infections

A total of 2329 Enterobacteriaceae strains in bacterial associations isolated from healthy children and children with salmonellosis were tested for their resistance to antimicrobial drugs. It was shown that the aerobic microbial associations isolated from the healthy children contained higher numbers of strains sensitive or resistant to 1-3 antibiotics while the microbial associations from the children patients with salmonellosis treated with antibiotics contained higher numbers of strains resistant to 6-8 antibiotics. Resistance of the aerobic bacterial associations was mainly defined by resistance of E. coli and K. pneumoniae. The feces of the healthy children never treated with antimicrobial drugs contained strains resistant to them. The use of the antibiotics in the treatment led to increasing numbers of the resistant bacteria and changing species composition of the bacterial associations.     

A population-based study of first and second-line drug-resistant tuberculosis in a high-burden area of the Mexico/United States border

The resistance of 139 Mycobacterium tuberculosis (MTB) isolates from the city of Monterrey, Northeast Mexico, to first and second-line anti-TB drugs was analysed. A total of 73 isolates were susceptible and 66 were resistant to anti-TB drugs. Monoresistance to streptomycin, isoniazid (INH) and ethambutol was observed in 29 cases. Resistance to INH was found in 52 cases and in 29 cases INH resistance was combined with resistance to two or three drugs. A total of 24 isolates were multidrug-resistant (MDR) resistant to at least INH and rifampicin and 11 MDR cases were resistant to five drugs. The proportion of MDR-TB among new TB cases in our target population was 0.72% (1/139 cases). The proportion of MDR-TB among previously treated cases was 25.18% (35/139 cases). The 13 polyresistant and 24 MDR isolates were assayed against the following seven second-line drugs: amikacin (AMK), kanamycin (KAN), capreomycin (CAP), clofazimine (CLF), ethionamide (ETH), ofloxacin (OFL) and cycloserine (CLS). Resistance to CLF, OFL or CLS was not observed. Resistance was detected to ETH (10.80%) and to AMK (2.70%), KAN (2.70%) and CAP (2.70%). One isolate of MDR with primary resistance was also resistant to three second-line drugs. Monterrey has a high prevalence of MDR-TB among previously treated cases and extensively drug-resistant-MTB strains may soon appear.     

Drug resistance of opportunistic enterobacteria isolated from various sources]

Resistance of 159 strains of opportunistic enterobacteria to 9 antibacterial drugs was studied. The strains were isolated from man and cattle. It was shown that the overwhelming majority of the isolates (93 per cent) were polyresistant irrespective of the genus. There was a high frequency of the strains resistant to the widely used antibiotics such as chloramphenicol (73 per cent), ampicillin (73.6 per cent) and rifampicin (95.6 per cent) and sulfanilamides (99.3 per cent). Gentamicin and nalidixic acid proved to be the most active against the cultures: 11.9 and 10 per cent of the resistant strains, respectively. The strains of enterobacteria isolated from different sources had a sensitivity to the antibiotics. Multiple antibiotic resistance to at least 5 drugs, variability of the spectra and high resistance were more characteristic of the isolates from the animals. The necessity of a rational use of antibacterial drugs in veterinary is indicated.     

Assessment of susceptibility to metronidazole and vancomycin of Clostridium difficile strains isolated between 1998-2002

The drugs of choice used to treat C. diffcile associated diarrhoea (CDAD) are metronidazole and vancomycin. C. difficile strains isolated in most laboratories are susceptible to metronidazole and vancomycin. Communication about emergence of antimicrobial resistance among C. difficile strains in some countries to metronidazole and intermediate resistance to vancomycin are alarming. This study was performed to determine the susceptibility to metronidazole and vancomycin of 140 C. difficile strains isolated from patients with CDAD hospitalised in academic hospital between 1999-2002. Resistance to metronidazole and vancomycin was not observed.     

Antibiotic Susceptibility of Bacteroides fragilis Group Strains in Hungary

Resistance rates to different antibiotics of 495 Bacteroides fragilis group strains were followed between 1987 and 1994 in Hungary. In 1992 the strains were collected in three different laboratories, whereas during the other periods strains were isolated in one centre. Metronidazole, chloramphenicol, imipenem and amoxicillin/clavulanic acid were the most active drugs. A high level of resistance was observed in 1987 for ampicillin (88% at > 4 mg/L), erythromycin (51% at > 4 mg/L), tetracyclin (53% at > 8 mg/L) and clindamycin (27% at > 4 mg/L). The same level of resistance was seen during the further years for clindamycin and ampicillin. Resistance to cefoxitin increased from 6% to 11% between 1987 and 1993/1994. No differences in resistance rates were observed between the strains collected in the three centers. For 100 strains, the results of the E test were compared with those of the micro-broth dilution test, both being used routinely for testing the antibiotic susceptibility of Bacteroides fragilis group strains in this period.     

Dynamics of drug resistance in Proteus mirabilis cultures 1970-1985

Resistance of 669 clinical strains of Proteus mirabilis to 18 chemotherapeutic drugs was studied in dynamics within 1970-1985. An increase in the number of cultures resistant to ampicillin and carbenicillin was noted while the number of cultures resistant to cephalosporines did not change. Within the period from 1970 to 1975 there was observed a marked increase in the number of Proteus strains resistant to aminoglycoside antibiotics. After that period their number gradually lowered and in 1985 reached the level of 1970. Beginning from 1973 there were observed a decrease in the number of Proteus chloramphenicol resistant strains and simultaneous occurrence of cultures sensitive to this antibiotic. The predominating number of the tested strains preserved during the whole observation period their resistance to tetracycline, doxycycline, rifampicin, novobiocin, furazolidone and furagin. No increase in the number of Proteus strains with multiple drug resistance including those resistant to 5-7 drugs was noted in the observation periods of 1970-1975, 1980 and 1985. The most frequent were Proteus strains resistant to 2-4 drugs. Among them cultures resistant to chloramphenicol and aminoglycoside antibiotics of the first generation predominated. Grouping of the strains by the same resistance spectra provided dividing the rested cultures of Proteus mirabilis into 69 variants.     

Pyrethroid resistance and mechanisms of resistance in field strains of Helicoverpa armigera (Lepidoptera: Noctuidae)

Pyrethroid resistance was found in 54 field strains of Helicoverpa armigera collected between 1995 and 1999 from 23 districts in seven states of India. LD50 values of the field strains ranged from 0.06 to 72.2 microg/larva with slopes of 0.5-3.1. Resistance was highest in regions where pyrethroid use was frequent (four to eight applications per season). Resistance to deltamethrin was exceptionally high with resistance ratios of 13,570 and 27,160 in two strains collected during February 1998 in central India. Resistance to cypermethrin, fenvalerate and cyhalothrin also was high with resistance ratios of >1,000 in four strains collected from central and southern India. Resistance ratios were below 100 in >50% of the strains tested. Pyrethroid resistance was high in strains collected from the districts in Andhra Pradesh where a majority of the cotton farmer suicide cases in India were reported. Resistance to pyrethroids appeared to have increased over 1995-1998 in most of the areas surveyed. Studies carried out through estimation of detoxification enzyme activity and synergists indicated that enhanced cytochrome p450 and esterase activities were probably important mechanisms for pyrethroid resistance in field strains. Pyrethroid nerve insensitivity also was found to be a major mechanism in some parts of the country where the use of pyrethroids was high. The information presented illustrates the importance of proper insect management programs to avoid the consequences associated with improper insecticide use.     

Increase in drug resistance among Shigella dysenteriae,Sh flexneri,and Sh boydii.

Two thousand three hundred and seventy strains of Shigella dysenteriae, Sh flexneri, and Sh boydii isolated in England and Wales from 1974 to 1978 were tested for resistance to 12 antimicrobial drugs. Eighty per cent of strains were resistant to one or more drugs, with sulphonamide resistance occurring most frequently. Resistance to streptomycin, tetracycline, ampicillin, and chloramphenicol increased during the period, as did the incidence of multiple resistance. Most infections due to Sh dysenteriae, Sh flexneri, and Sh boydii are acquired abroad, and the increasing incidence of drug resistance among these organisms contrasts with the decreasing incidence of resistance among the indigenous Sh sonnei. These findings may indicate the need for better control of antibiotic use, particularly in developing countries.     

Survey of Infectious Multiple Drug Resistance Among Salmonella Isolated from Animals in the United States

Salmonella cultures were obtained from outbreaks of animal disease from 37 states and 1 territory. They were screened for resistance to 11 antimicrobial drugs. Of the 1,251 strains studied, 935 were resistant to one or more of these agents. The three most common resistance patterns were ampicillin, dihydrostreptomycin, sulfamethoxypyridazine, tetracycline; ampicillin, dihydrostreptomycin, sulfamethoxypyridazine; dihydrostreptomycin, sulfamethoxypyridazine, tetracycline. Resistance transfer was demonstrated on 267 multiply resistant cultures, of which 181 were able to transfer all or part of their resistance pattern to a drug-sensitive recipient.     

Monitoring for insecticide resistance in field-collected strains of the German cockroach (Dictyoptera: Blattellidae)

Forty-five field-collected strains of German cockroaches, Blattella germanica were tested for resistance to 12 different insecticides by the time-mortality response method in comparison with a known susceptible strain. Only low to moderate resistance to diazinon, chlorpyrifos, and acephate was detected. Resistance to malathion was widespread; about half of the strains tested showed high resistance. High resistance to the carbamates propoxur and bendiocarb also occurred. High resistance was uncommon with propoxur, but about 35 strains were highly resistant to bendiocarb. High resistance to pyrethrins was observed in about of the strains tested. Resistance to the pyrethroids allethrin, permethrin, phenothrin, fenvalerate, and cyfluthrin was detected in some of the strains examined. All of the strains tested were susceptible to one or more of the insecticides used. These results indicate that, although resistance is a serious problem in this species, satisfactory control should be possible by selection of an appropriate insecticide.     

Drug resistance of the causative agent of Grigo'rev-Shiga dysentery (Shigella dysenteriae 1)isolated in the USSR

Forty strains of S. dysenteriae 1 isolated in the USSR within 1986-1988 were tested for their resistance to 11 antibacterial drugs. It was shown that 92.5-97.5 per cent of the isolates were resistant to chloramphenicol (Cm) and tetracycline (Tc), 22.5 per cent to streptomycin (Sm), 17.5 per cent to nalidixic acid (Nal) and 10 per cent to ampicillin (Ap) and polymyxin (Pm). Resistance to Cm Tc (51.4 per cent) and Cm Tc Nal (13.5 per cent) represented the predominating phenotype. 35 per cent of the strains carried conjugative R plasmids. In the majority of the cases, the determinants of resistance to Cm and Tc were transferred, which must define the high frequency of the strains resistant to Cm and Tc. All the tested strains were sensitive to gentamicin, neomycin, rifampicin, cefamezin and ciprofloxacin. Since the strains of S. dysenteriae 1 proved to be highly sensitive to the tested drugs it appeared possible to consider them as the drugs of choice in etiotropic therapy of patients with dysentery caused by the pathogens of the Grigoryev-Shiga group.     

Antibiotic resistance among anaerobic Gram-negative bacilli: lessons from a French multicentric survey

Temporal changes of antibiotic susceptibilities among anaerobes in France are followed in our laboratory since 1992. For Bacteroides strains, resistance increased from 1992 to 1998 for amoxicillin-clavulanic acid, cefotetan and clindamycin. The present study evaluates the situation in 2000 for 434 Gram-negative anaerobic clinical isolates (obtained from 9 large university hospitals) by testing amoxicillin and ticarcillin alone or combined with clavulanic acid, cefoxitin, cefotetan, imipenem, clindamycin and metronidazole (using the NCCLS-approved method for MIC determination. The main genera tested included Bacteroides (359 strains of the fragilis group), Prevotella (40 strains), Fusobacterium (23 strains) and miscellaneous species (8 strains). Resistance rates within the B. fragilis group were: amoxicillin-clavulanic acid 5.6%, ticarcillin 33%, ticarcillin-clavulanic acid 2%, cefoxitin 13%, cefotetan 44%, clindamycin 33%, imipenem 1% and metronidazole <1%, respectively. Only one strain of B. fragilis was resistant to metronidazole (MIC=64 mg/L); due to the presence of the nimA gene on the chromosome. Resistance to imipenem or metronidazole was only found among the B. fragilis species. These two former drugs excepted, B. fragilis was less resistant to antibiotics than the other species. beta-lactamase production was detected for 357/359 strains of the fragilis group, 26/40 stains of Prevotella and 3/23 strains of Fusobacterium. Dynamic changes of antibacterial resistance are occurring within the B. fragilis group: decreased resistance to amoxicillin-clavulanic acid, ticarcillin-clavulanic acid, imipenem while resistance for cefoxitin, cefotetan, clindamycin continues to increase. Regular antibiotic surveys are needed as a source of information to guide the empirical therapy of anaerobic infections.     

Trimethoprim resistance in hospitals.

During November 1980 to April 1981, 1561 urinary tract pathogens were collected from Turku City Hospital, Turku University Central Hospital, and Kuopio University Central Hospital. Resistance of the strains was tested by agar-plate dilution against trimethoprim, sulphamethoxazole-trimethoprim, sulphamethoxazole, ampicillin, and nitrofurantoin. Resistance to trimethoprim (greater than 8 mg/l) occurred in 8.6-12.2% of strains from the university hospitals (Pseudomonas excluded) and 38.3% of strains from Turku City Hospital. Resistance of Escherichia coli occurred in 4.1-6.2% of strains from the university hospitals and 21% of strains from Turku City Hospital. Proteus mirabilis was the most resistant of the clinically important bacterial species with resistance to trimethoprim in 29-78%. Attention is called for in defining the type of hospital used for a particular study: bacterial resistance in different hospitals cannot be compared direct and one hospital is not necessarily representative for a whole country. After seven years'' use of plain trimethoprim the prevalence of resistance in the two university hospitals in Finland was similar to that in a London hospital just before plain trimethoprim was registered for use in Britain.     

Antibiotic resistance in Staphylococci isolated from the vaginas of captive female Leontopithecus (Callitrichidae-Primates)

The purpose of this study was to provide current data on Staphylococcus species from the vaginas of clinically normal captive lion tamarins and to determine the antimicrobial susceptibility of these isolates. Samples were collected from 25 adult lion tamarins, processed to isolate Staphylococcus species, and tested for susceptibility to penicillin G, gentamicin, chloramphenicol, tetracycline, trimethoprim-sulfamethoxazole, streptomycin, ampicillin, and rifampicin. Isolates with the typical characteristics of the genus Staphylococcus were recovered from all 25 samples. Coagulase-negative species were the most common (68% of the isolates), and the most frequently isolated species (10 samples) was S. simulans. Other coagulase-negative species, including S. saprophyticus (n=5), S. epidermidis (n=1), and S. arlettae (n=1), were also recovered. Coagulase-positive Staphylococci were obtained from eight animals (six of from the S. aureus species and two from S. intermedius). Resistance to antibiotics was frequently observed, and 88% of the isolates (23 samples) showed resistance to at least one drug. Resistance to penicillin G was a common finding, and the most active antimicrobial agents were chloramphenicol and gentamicin. Coagulase-positive strains were more frequently resistant to antibiotics (79.7%, average=6.4 drugs) than coagulase-negative strains (38.2%, average=3.0 drugs). The high frequency of resistance observed in those isolates is surprising and very alarming. A detailed history of the use of antimicrobial drugs in these subjects did not reveal any previous exposure to any of the tested antibiotics that could justify the observed resistance rate.     

Resistance to drugs and heavy metals, colicin production, and biochemical characteristics of selected bovine and porcine Escherichia coli strains.

A study was made of resistance to heavy metals and antibiotics, biochemical characteristics, and colicinogeny in selected strains of Escherichia coli of O serogroups 8, 9, 20, 64, 101, and X46. Of 42 strains that were investigated, 26 were porcine enterotoxigenic E. coli (ETEC), 8 were porcine non-enterotoxigenic E. coli (NETEC), and 8 were bovine ETEC. Multiple resistance to antimicrobial agents was common among the strains, and resistance to chloramphenicol and kanamycin was less common than resistance to other drugs, possibly reflecting the lower frequency of use of these agents in pigs and calves. Colicin production was a more common property of porcine ETEC (80.8%) than of porcine NETEC (25%), and all porcine ETEC of O serogroups 101 and 64 were colicinogenic. Equal numbers of bovine ETEC strains were colicinogenic as were non-colicinogenic. Resistance of bovine and porcine strains to sodium arsenate, mercury, and tellerium was 90, 16, and 5%, respectively. There was a close relationship between serogroup and biochemical reactions among the E. coli strains tested.     

Carbamate and organophosphate resistance in cotton pests in India, 1995 to 1999

Monitoring for organophosphate and carbamate resistance was carried out on five major insect pests of cotton collected from 22 cotton-growing districts across India. Resistance was monitored in Helicoverpa armigera (Hübner) and Pectinophora gossypiella (Saunders) for the period 1995-1999 and for Spodoptera litura (Fabricius), Earias vittella (Fabricius) and Bemisia tabaci (Gennadius) in a survey conducted during the 1997-98 cropping season. Of the 53 field strains of H. armigera, only four were found to exhibit resistance to quinalphos, the highest 15-fold, whereas all 16 field strains tested were found to be resistant to monocrotophos. Similarly, out of 40 field strains tested, only eight were found to express appreciable resistance to methomyl. Resistance in P. gossypiella to quinalphos was high in the majority of the strains tested. Of the seven strains of E. vittella tested, two strains from northern India exhibited > 70-fold resistance to monocrotophos. Of the 11 S. litura strains tested, only four were found to exhibit resistance factors of 10 to 30-fold to quinalphos and monocrotophos. All of the B. tabaci field strains exhibited resistance to methomyl and monocrotophos and susceptibility to triazophos. Practical implications for pest control resulting from the observed patterns of cross-resistance between quinalphos, monocrotophos and methomyl are discussed.     

The Prevalence in Canada of Drug-Resistant Tubercle Bacilli in Newly Discovered Untreated Patients with Tuberculosis

During the period February 1963 to September 1964, the incidence of strains of tubercle bacilli excreted by newly diagnosed, previously untreated patients with tuberculosis in Canada that were resistant to the major antituberculosis drugs, viz. streptomycin, para-aminosalicylic acid and isoniazid, was 4.8%. Resistance to a single drug (3.8%) was observed more commonly than was resistance to two drugs (0.9%) or to all three drugs (0.3%), and the drug most frequently involved in this regard was streptomycin (1.8%). Data for the province of Ontario were almost the same as those for Canada. These data are compared with results of surveys in other countries and it is concluded that while drug-resistant tubercle bacilli do not constitute a major problem in Canada at present, awareness of this potential hazard should be maintained.     

Antimicrobial susceptibility of staphylococci isolated from otitis externa in dogs

Samples were obtained from 65 unmedicated adult dogs, processed for isolation of Staphylococcus species and tested for susceptibility to penicillin G, gentamicin, oxacillin, tetracycline, trimethoprim-sulphamethoxazole, streptomycin, ampicillin and rifampin. Forty-four isolates were obtained, which represents 67.7% of samples. Coagulase-negative species were most commonly found, and the most frequently isolated staphylococcus species were Staph. epidermidis and Staph. aureus. Other species, such as Staph. simulans, Staph. haemolyticus, Staph. saprophyticus and Staph. intermedius were also isolated. Resistance to antibiotics was frequently observed, with 90.9% of the isolates showing resistance to at least one drug. The most active antimicrobial agents against staphylococci isolated from otitis externa of dogs were rifampin and oxacillin. Multidrug resistance was a common finding, and one strain of Staph. haemolyticus species, was resistant to all tested antimicrobial agents. Resistance to three or more different drugs was a common finding, observed in 16 strains (36.4%) of both coagulase-positive and coagulase-negative staphylococci. This study highlights the emergence of cases of otitis externa determined by coagulase-negative staphylococcus strains and once more emphasizes the need for bacterial culture with species identification and susceptibility testing of swab specimens from the ear canal in order to choose appropriate antimicrobial agents.     

2010年广州地区淋球菌耐药监测结果分析

目的了解广州地区淋球菌对抗生素耐药性的变化及PPNG和TRNG的流行趋势。方法用琼脂稀释法测定头孢曲松、大观霉素、环丙沙星、阿奇霉素和四环素的最低抑菌浓度（MIC）;用纸片碘量法检测β-内酰胺酶。结果83株淋球菌检出PPNG24株（28．9％）、TRNG50株（60．2％）、环丙沙星耐药率高达98．8％,高度耐药株（MIC≥16mg／L）43株（51．8％）,而76株淋球菌中阿奇霉素耐药株11株（14．5％）,均未出现对头孢曲松、大观霉素耐药的菌株,抗菌活性强。结论合理规范使用抗生素及动态监测淋球菌耐药性变迁是临床减少淋球菌耐药菌株出现的有效办法。