Drug sensitivity of bacterial strains isolated from clinical specimens during the years 1987-1988

Sensitivity to selected chemotherapeutics of various bacterial strains was analysed. Bacteria were isolated from the different material collected from patients within 1987-1988, and included: 690 strains of staphylococci, 465 strains of streptococci, 1224 strains of aerobic gram-negative bacilli, and 163 strains of anaerobic micro-organisms. Out of isolated staphylococci, the highest percentage was sensitive to vancomycin, pristinamycin, and fusidic acid. Vancomycin proved the most effective against streptococci followed by chloramphenicol and netilmicin . However, streptococci were highly sensitive to vancomycin within two years whereas their sensitivity to chloramphenicol and netilmicin .     

Analysis of the etiological structure and dynamics of antibiotic resistance in the causative agents of suppurative inflammatory diseases in the patients at a large general hospital

The structure of the causative agents isolated from patients with pyoinflammatory infections in 1980-1983 was analysed. It was shown that the surgical and urological infections were mainly caused by gram-negative bacteria. The other pyoinflammatory infections were mainly due to gram-positive cocci. A relatively high frequency of the strains of gram-negative bacteria, especially among Pseudomonas spp. and Enterobacter spp., resistant to aminoglycoside antibiotics, such as gentamicin, sisomycin and tobramycin with preserved sensitivity to amikacin and netilmicin in the majority of the strains was shown. Among the beta-lactam antibiotics cephotaxim and cephalotin were most active against gram-negative bacteria and staphylococci, respectively. The majority of the antibiotic resistant strains of gram-negative bacteria had analogous structures and levels of resistance to 7-12 antibiotics which might indicate the occurrence of 1-2 resistance plasmids among the clinical strains.     

Sensitivity of bacteria of the genus Acinetobacter to antibiotics and ofloxacin

Between 1989-1989 276 strains of Acinetobacter genus were isolated which contained: Acinetobacter calcoaceticus subsp. anitratus (n = 167), Acinetobacter calcoaceticus subsp. Iwoffi (n- = 83), Acinetobacter haemolyticus (n = 26). Their sensitivity to aminoglycoside antibiotics, beta-lactams, tetracyclines, chloramphenicol, colistin, and ofloxacin was tested. More than 90% of strains were sensitive to colistin and ofloxacin. The sensitivity to remaining antibiotics differentiated depending on species. Acinetobacter anitratus were highly resistant to Ist and IInd generation of cephalosporins, and moreover to penicillins, tetracyclines, and chloramphenicol. Cephalosporins of IIIrd generation were active against 70% of strains with exception of cefoperazone what was also the case for representatives of aminoglycosides as netilmicin and amikacin. Strains of Acinetobacter Iwoffi were in majority sensitive to all antibiotics with exception of cephalothin, cephradine and cefoperazone. More than 90% of Acinetobacter haemolyticus strains were sensitive to gentamicin, carbenicillin, azlocillin, ceftriaxone, cefotaxime and tetracyclines.     

In vitro antibacterial activity of a new 1-oxa cephalosporin compound

The in vitro activity of a unique new 1-oxa cephalosporin beta-lactam antibiotic (LY 127935) was tested against clinical isolates of gram-positive and gram-negative bacteria and compared with the activities of cefoxitin, cefamandole, cephalothin, clindamycin, amikacin, tobramycin, gentamicin, ticarcillin, and carbenicillin. The new compound was observed to have a broad spectrum of antibacterial activity which far exceeded the activity of older cephalosporins against aerobic gram-negative enteric bacilli. This new compound was the most active drug tested against Klebsiella, Serratia, Enterobacter, indole-negative and positive Proteus species, and E. coli. Against clinical isolates of Pseudomonas species the new compound was more active than cefoxitin, cefamandole, cephalothin, and clindamycin, comparable to ticarcillin and carbenicillin, and less active than gentamicin, tobramycin, and amikacin. Yet, most of the Pseudomonas isolates were inhibited by 16 micrograms/ml of the new compound. Against both beta-lactamase and non beta-lactamase producing Staphylococcus aureus isolates, the new 1-oxa compound was less active than the older cephalosporins of which cephalothin and cefamandole were the most effective. The 1-oxa compound had no appreciable activity against isolates of Streptococcus faecalis. Activity of all four cephalosporins studied was decreased in the presence of an increased inoculum of Enterobacteriaceae in trypticase soy and Mueller-Hinton broth. The activity of the new compound against Pseudomonas species was also decreased by an increased inoculum in Mueller-Hinton but not in trypticase soy broth. These results indicate that this new 1-oxa compound may have great promise as a broad spectrum antibiotic and may warrant controlled clinical trials in man.     

The Activity of Pipemidic Acid and Piromidic Acid against Escherichia coli In Static Culture and in Conditions Simulating the Treatment of Bacterial Cystitis

The activity of the new pyridopyrimidine compounds, pipemidic and piromidic acids, against Escherichia coli was compared with that of nalidixic acid in vitro . In a static turbidimetric system nalidixic and pipemidic acids were found to be more active than piromidic acid when tested against sensitive E. coli strains, but pipemidic acid was the most active of the three compounds against nalidixic acid-resistant clinical isolates. When tested in an in vitro model designed to mimic the conditions in which bacteria and drug interact in the treatment of bacterial cystitis, all three drugs were found to be able to suppress bacterial growth for long periods, but a high, sustained drug level was necessary in order to prevent the emergence of resistant variants.     

Susceptibility of various purple and green sulfur bacteria to different antimicrobial agents

Abstract Several purple and green sulfur bacteria (genera Chromatium, Thiocapsa and Chlorobium ) were tested for their sensitivity to different antimicrobial agents by a disc diffusion assay, using thioacetamide as a source of hydrogen sulfide for plate growth. Chlorobium limicola strains were more sensitive to amoxicillin, erythromycin and nalidixic acid, whereas gentamicin and netilmicin were more active against the purple bacteria tested. None of the organisms were sensitive to oxacillin and trimethoprim + sulfamethoxazole. The critical concentrations at the edge of the inhibition zone were also calculated for three organisms and the antimicrobials colistin, mitomycin C, penicillin G, rifampicin, and streptomycin. The results obtained suggest that colistin, mitomycin C, penicillin G would provide selective conditions against the growth of Chlorobium limicola strains, while streptomycin and other aminoglycoside antibiotics would select against purple bacteria.     

Sensitivity to antibacterial preparations of the pseudotuberculosis bacteria isolated on the territory of the Ukraine]

Sensitivity of 92 strains of the causative agent of pseudotuberculosis isolated in the Ukraine was studied with respect to 26 antibacterial drugs. It was found that the strains of the pseudotuberculous bacteria were sensitive to 17 drugs, i.e. benzylpenicillin, ampicillin, carbenicillin, cephaloridin, chloramphenicol, tetracycline, streptomycin, neomycin, monomycin, kanamycin, gentamicin, polymyxin, colistin, furadontin, nalidixic acid, sulfisoxazol and septrin. No differences in the sensitivity of the strains isolated in various districts of the Ukraine and from various sources were found. By their antibiotic sensitivity the strains isolated in the Ukraine did not differ from the cultures isolated in other districts of the USSR and abroad.     

Susceptibility to selected antibiotics of Yersinia enterocolitica 03 strains, carrying and not carrying plasmid pYV

A total of 199 clinical strains of Yersinia enterocolitica serotype O3, biotype 4 were tested for their susceptibility to antibiotics (158 strains carried the virulence plasmid pYV and 41 strains did not). 114 isolates were tested by standard disk diffusion method for 21 antibiotics. Almost all tested strains were resistant to ampicillin and cefazolin and susceptible to amoxycillin/clavulanate, cefaclor, cefamandole, cefuroxime, cefotaxime, ceftriaxone, aztreonam, imipenem, gentamicin, amikacin, netilmicin, tetracycline, doxycycline, chloramphenicol, ciprofloxacin, sulphamethoxazole, co-trimoxazole, trimethoprim and furazolidone. In addition minimal inhibitory concentrations (MICs) of 15 antibiotics were determined by agar dilution method for all 199 strains (158 plasmid positive and 41 strains plasmid negative). Third-generation cephalosporins such as cefotaxime and ceftriaxone and a fluoroquinolone (ciprofloxacin) were the most active antimicrobial agents, tested followed by aztreonam, imipenem, trimethoprim, tetracycline, gentamicin, chloramphenicol, amoxycillin/clavulanate, cefaclor, cefuroxime, amikacin, furazolidone and sulphamethoxazole. The present study demonstrated a high susceptibility of clinical strains of Y. enterocolitica to most of the tested antibiotics. In general, there was no significant difference between susceptibility of virulence plasmid pYV positive and virulence plasmid negative strains to antibacterial agents.     

Tobramycin,amikacin, sissomicin,and gentamicin resistant Gram-negative rods.

Sensitivities to gentamicin, sissomicin, tobramycin, and amikacin were compared in 196 gentamicin-resistant Gram-negative rods and in 212 similar organisms sensitive to gentamicin, mainly isolated from clinical specimens. Amikacin was the aminoglycoside most active against gentamicin-resistant organisms, Pseudomonas aeruginosa, klebsiella spp, Escherichia coli, Proteus spp, Providencia spp, and Citrobacter spp being particularly susceptible. Most of the gentamicin-resistant organisms were isolated from the urine of patients undergoing surgery. Gentamicin was the most active antibiotic against gentamicin-sensitive E coli, Proteus mirabilis, and Serratia spp. Pseudomonas aeruginosa and other Pseudomonas spp were most susceptible to tobramycin.     

Monitoring of uropathogens and their susceptibility to antibiotics]

Samples of urine collected from patients with complicated urology infection and hospitalized to the Moscow Region Research Clinical Institute in 1986, 1991, 1995 and 1999 were analysed. Of 11,444 samples examined, bacteriuria was estimated in 7143 samples. 9786 strains (29 genus) of bacteria were isolated--56.9 per cent as mono culture and 43.1 per cent as associations. Susceptibility to 21 antibiotic was determined by disk diffusion method for 1607 strains; beta-lactamase production was determined in 198 strains, MIC was determined for 41 antibiotics. Gram-negative rods relative amount among pathogens decreased substantially (84.7 per cent in 1986 against 61.6 per cent in 1999), particularly Enterobacteriaceae (74.7 per cent in 1986 against 41.4 per cent in 1999). Nonfermenting Gram-negative rods (NFGNR) relative amount increased (10.8 per cent against 19.2 per cent), along with Gram-positive cocci (19.8 per cent against 64.2 per cent), particularly coagulasenegative staphylococci (CNS) (10.8 per cent against 35.9 per cent) and enterococci (5 per cent against 16.5 per cent) and candida and fungi (0.5 per cent in 1986 against 15.9 per cent in 1999). At the period 1986-1999 the main pathogens in urology infection were E. coli, Enterobacter spp., NFGNR (including P. aeruginosa), Staphylococcus, CNS, Enterococcus spp. The problem pathogens for urological department were the following: E. coli, Klebsiella spp., Enterobacter spp., Proteus spp., NFGNR including P. aeruginosa, CNS, Enterococcus spp., candida and fungi. At the period 1991-1997 Gram-negative pathogens susceptibility to amikacin, ofloxacin, ciprofloxacin, imipenem, ceftazidime, cefotaxime was not changed in general, Gram-positive cocci (staphylococci and enterococci) retained the same susceptibility to vancomicin, cefamandol and amoxyclave. Staphylococci were also susceptible to amikacin, imipenem, rifampicin, oxacillin, ciprofloxacin, and ofloxacin. Production of beta-lactamase was registered for 38.7 per cent of CNS, 26.5 per cent of E. coli, 38.5 per cent of K. pneumoniae, 25 per cent of P. mirabilis and 55.6 per cent of P. aeruginosa strains.     

Bacterial multiresistance to antibiotics. Study of types of bacterial resistance to antibiotics in the environment and in clinical material of a resuscitation ward

Types of resistance were studied in clinical material and in the environment a resuscitation ward in the period from September 1973 to February 1974. Identical strains with the same types of resistance were isolated in both groups. They were verified by qualitative and quantitative tests of sensitivity to selected antibacterial substances. A high degeee of resistance to streptomycin, chloramphenicol, tetracycline and ampicillin was found in all gram-negative bacilli. High effectivity of colimycin, gentamicin and co-trimoxazole was confirmed in vitro. The strains of Staphylococcus aureus were fully sensitive only to oxacillin, lincomycin, spiramycin, vancomycin, gentamicin and co-trimoxazole. The strains of Streptococcus faecalis were found sensitive only to ampicillin and vancomycin.     

Correlation between antibiotic sensitivity testing by conventional and conductivity measurements

A high correlation in the susceptibilities of 44 strains isolated from clinical material to a variety of antimicrobial agents was found between the minimum inhibitory concentration and conductivity measurements. Some discrepancy was found for vancomycin and teicoplanin when tested against 21 strains of staphylococci. Similarly, discrepancies were seen with azlocillin, chloramphenicol and gentamicin when tested against strains of aerobic and facultatively anaerobic Gram-negative bacilli. In the majority of cases in which discrepancies were noted, this reflected differences in relative, and not absolute, susceptibility. With five strains of Pseudomonas, however, there was a poor correlation with three of four antibiotics studied. The advantage of this technique is that sensitivities are available within 4-6 h.     

Correlation between antibiotic sensitivity testing by conventional and conductivity measurements

A high correlation in the susceptibilities of 44 strains isolated from clinical material to a variety of antimicrobial agents was found between the minimum inhibitory concentration and conductivity measurements. Some discrepancy was found for vancomycin and teicoplanin when tested against 21 strains of staphylococci. Similarly, discrepancies were seen with azlocillin, chloramphenicol and gentamicin when tested against strains of aerobic and facultatively anaerobic Gram-negative bacilli. In the majority of cases in which discrepancies were noted, this reflected differences in relative, and not absolute, susceptibility. With five strains of Pseudomonas however, there was a poor correlation with three of four antibiotics studied. The advantage of this technique is that sensitivities are available within 4–6 h.     

Resistance to aminoglycoside antibiotics of gram-negative bacilli isolated in Canadian hospitals.

A survey was made of the frequency of resistance to amikacin, gentamicin and tobramycin among aerobic gram-negative bacilli isolated over a 4-week period in 1979 at six large, geographically separated Canadian hospitals. In the entire series of 4407 isolates the frequency of resistance was 2.5% to amikacin, 8.1% to gentamicin, 5.9% to tobramycin and 1.7% to all three. Most (81%) of the resistant bacteria were acquired by the patients after admission to hospital. The frequency of resistance to the three aminoglycoside antibiotics in each hospital largely reflected the local rate of cross-infection by endemic strains of resistant bacteria.     

Evaluation of media for monitoring fecal streptococci in seawater

The selectivity of KF streptococcus agar (KF) for monitoring fecal streptococci (FS) in seawater was examined in 234 samples of Mediterranean water and compared with the selectivity of M-Enterococcus agar (M-Ent) for 124 samples and with bile-esculin-azide agar (BEA) for 17 samples. KF was found to be unsuitable for marine water because Vibrio alginolyticus and other gram-negative bacilli indigenous to this environment grew well on it and produced red colonies identical to those of FS. In 26% of samples, some with high counts of red colonies on the membrane filters (MF), there were no streptococci, only gram-negative bacilli and staphylococci, and in an additional 23.1% the streptococci constituted less than 50% of the "typical" red colonies on the MF. V. alginolyticus also produced FS-like colonies on MF incubated on BEA but was not isolated from MF incubated on M-Ent. Although staphylococci grew and produced FS-like colonies on all three media, M-Ent was the most selective since no gram-negative bacilli were isolated from MF incubated on it.     

Evaluation of media for monitoring fecal streptococci in seawater.

The selectivity of KF streptococcus agar (KF) for monitoring fecal streptococci (FS) in seawater was examined in 234 samples of Mediterranean water and compared with the selectivity of M-Enterococcus agar (M-Ent) for 124 samples and with bile-esculin-azide agar (BEA) for 17 samples. KF was found to be unsuitable for marine water because Vibrio alginolyticus and other gram-negative bacilli indigenous to this environment grew well on it and produced red colonies identical to those of FS. In 26% of samples, some with high counts of red colonies on the membrane filters (MF), there were no streptococci, only gram-negative bacilli and staphylococci, and in an additional 23.1% the streptococci constituted less than 50% of the "typical" red colonies on the MF. V. alginolyticus also produced FS-like colonies on MF incubated on BEA but was not isolated from MF incubated on M-Ent. Although staphylococci grew and produced FS-like colonies on all three media, M-Ent was the most selective since no gram-negative bacilli were isolated from MF incubated on it.     

Antimicrobial Susceptibility of Clostridium difficile from Different Sources

A total of 79 Clostridium difficile strains from healthy young and elderly adults, elderly patients without gastrointestinal disease, elderly patients receiving antibiotics without gastrointestinal complications, and elderly patients with antibiotic-associated diarrhea or pseudomembranous colitis were tested for their susceptibilities to 24 antimicrobial agents. All of the 79 strains were inhibited by low concentrations of rifampicin, metronidazole, fusidic acid, vancomycin, ampicillin, and penicillin G. The strains were highly resistant to aminoglycosides, trimethoprim, sulfamethoxazole, nalidixic acid, and cycloserine and often resistant to neomycin, cefoxitin, and cefalexin. Wide variations in the susceptibility of C. difficile strains to erythromycin, clindamycin, lincomycin, chloramphenicol, and tetracycline were found. Strains resistant to erythromycin, clindamycin, and lincomycin were more frequently found among strains isolated from elderly adults than those isolated from young adults, with particularly high frequency among strains isolated from elderly patients receiving antibiotics. None of the 23 strains isolated from healthy young adults was resistant to chloramphenicol. All of the 14 strains resistant to erythromycin, clindamycin, lincomycin, and chloramphenicol were sensitive to tetracycline and all of the 15 strains resistant to erythromycin, clindamycin, lincomycin, and tetracycline were sensitive to chloramphenicol. Only one out of 19 tetracycline-resistant strains was highly toxigenic, whereas 42 (70%) of 60 sensitive strains were highly toxigenic.     

Rifampicin in the treatment of infections of non-tuberculous etiology

Clinical efficacy of rifampicin, a semisynthetic broad spectrum antibiotic was estimated in 247 patients with purulent inflammations. It was shown advisable to use rifampicin intravenously in treatment of severe bronchopulmonary pathology, disorders of the bile excretion system, osteomyelitis, severe wound infections and in prophylaxis of postoperative purulent complications in cardiovascular surgery and other cases. High rifampicin sensitivity of staphylococci and streptococci belonging to various species was revealed. Rifampicin was found to be less active against gramnegative pathogens. The isolation frequency of rifampicin sensitive strains of E. coli, Proteus spp., Klebsiella spp. and P. aeruginosa amounted to 88.4, 52.1, 58.8 and 49.3 per cent respectively.     

An in vitro time-kill assessment of linezolid and anaerobic bacteria

Linezolid is a novel oxazolidinone antibacterial agent active against staphylococci (including methicillin-resistant strains), enterococci (including vancomycin-resistant strains), streptococci (including penicillin-intermediate and -resistant Streptococcus pneumoniae), and other aerobic and facultative bacteria. The agent has also demonstrated activity against a broad spectrum of Gram-positive and Gram-negative anaerobic bacteria. Previous time-kill assessments have shown linezolid to be generally bacteriostatic against staphylococci and enterococci, and bactericidal against streptococci. In this study, an anaerobic glovebox technique was employed to conduct time-kill assessments for four strains of anaerobic Gram-positive, and seven strains of anaerobic Gram-negative bacteria. The time-kill experiment was performed using Anaerobe Broth medium. The drugs were tested at four-fold the minimum inhibitory concentration (MIC), or at the higher concentration of 8mg/L for linezolid, 2mg/L for clindamycin, and 8mg/L for metronidazole. Samples for viable count were taken at 0, 6, and 24h, and plated using the Bioscience International Autospiral DW. Exposure of samples to the aerobic environment during plating was held to less than 30min. Plates were counted after a 48h anaerobic incubation (37 degrees C). The species tested included Bacteroides fragilis (2), B. distasonis, B. thetaiotaomicron, Fusobacterium nucleatum, F. varium, Prevotella melaninogenica, Clostridium perfringens, Eubacterium lentum and Peptostreptococcus anaerobius (2). The activity of linezolid was compared to that of metronidazole and clindamycin, two standard anti-anaerobe agents. As expected, the control agents were very active in these assays. Metronidazole yielded log(10)CFU/mL reductions of 3.0 or greater for nine of ten strains; clindamycin yielded log(10)CFU/mL reductions of 2.0 or greater for six of 11 strains, and 3.0 or greater for three strains. Linezolid also produced significant in vitro killing in this model achieving log(10)CFU/mL reductions of 2.0 or greater for six of 11 strains, and 3.0 or greater for four strains. The profile of activity was similar to that of clindamycin indicating that additional developmental studies of linezolid with anaerobic bacteria are warranted.     

A Three-Year Survey of the Antibacterial Spectra of the More Commonly Used Chemotherapeutic Agents

Eight major bacterial groups (25,000 strains) of gram-positive and gram-negative organisms which were isolated from a variety of clinical specimens were tested by the disc-plate and tube dilution procedure. The in vitro antibacterial spectra of 17 commonly used chemotherapeutic agents were recorded and evaluated statistically during a three-year period. Penicillin G, erythromycin and chloramphenicol were very effective against members of the diplococci and streptococci genera. The synthetic penicillins inhibited 99% of Staph. aureus whereas penicillin G was effective against only 45% of these strains. There was a significant increase in the number of tetracycline-resistant strains of both D. pneumoniae and the Lancefield Group A streptococci. A yearly increase in gram-negative pathogens was noted. These organisms (i.e. Escherichia, Aerobacter, Proteus, Pseudomonas) showed greater resistance to the majority of chemotherapeutic agents than did the gram-positive organisms. The percentage of susceptible strains for each bacterial group appears in the text.