Two hundred strains of Klebsiella species isolated from clinical specimens over a four-month period were biotyped as Klebsiella aerogenes (173 strains), Klebsiella ozaenae (15 strains), Klebsiella edwardsii (5 strains), Klebsiella atlantae (2 strains) and Klebsiella oxytoca (1 strain). Klebsiella aerogenes and Klebsiella ozaenae were more resistant towards antibiotics when compared with other species. Colonial morphology on eosin methylene blue agar (Oxoid) was not found useful for differentiations of Klebsiella biotypes.
Six independent isolates of Klebsiella from hospital environmental sources in Malaysia were found to be resistant to at least ampicillin, carbenicillin, cefoperazone, chloramphenicol, gentamicin and tetracycline. On the basis of their antibiograms, they were divided into four antibiogroups. They transferred all or part of their multiple antibiotic resistance traits to E. coli by conjugation. The results suggest that these Klebsiella strains harbour self-transmissible R plasmids. The significance of these findings are discussed.
Fifteen independent E. coli strains of avian, bovine and porcine origin in Peninsular Malaysia were tested for antibiotic resistance and conjugative R plasmids. Eight (53%) isolates were found to be antibiotic resistant. Among them, 37.5% were mono-resistant and 62.5% were resistant to three or more antibiotics, i.e., multi-resistant. All of them were resistant to Tc and sensitive to Gm and Nx. Three of the eight antibiotic resistant strains were able to transfer all or part of their resistance to an E. coli K12 recipient by conjugation. The transfer frequencies of Km, Sm and Tc resistance of the three donors varied between 4.5 X 10(-8) to 6.8 X 10(-7). Analysis of the plasmid profiles of all the three donors and their respective transconjugants after agarose gel electrophoresis provided conclusive evidence that the transferable resistance traits were plasmid-mediated.
Four of the five veterinary E. coli strains, which were unable to transfer their antibiotic resistance by conjugation, were found to harbour plasmids. Evidence from transformation, agarose gel electrophoresis and curing experiments showed that in strains KE-3, KE-4 and KE-14 a nonconjugative R plasmid carried the gene for resistance to tetracycline. The plasmids in KE-9 were cryptic.
A clinical isolate of Proteus sp., resistant to ampicillin, carbenicillin, cephaloridine, chloramphenicol, cotrimoxazole, gentamicin,
kanamycin and tetracycline, was examined for the presence of conjugative R plasmids. Results from conjugation, agarose gel
electrophoresis and transformation experiments showed that it harboured a large self-transmissible R plasmid which coded for all
the resistance traits.
170 clinical isolates of Pseudomonas aeruginosa were tested for in vitro susceptibility to gentamicin, amikacin, tobramycin, netilmicin, kanamycin, streptomycin, cefotaxime, ceftriaxone, cefoperazone, ceftazidime, moxalactam, azlocillin, piperacillin and ticarcillin. Against 93 gentamicin-sensitive strains, the most active antibiotics were in descending order, ceftazidime, tobramycin, gentamicin, amikacin, and the ureidopenicillins. Against 77 gentamicin-resistant strains, only ceftazidime, amikacin and moxalactam had mode minimum inhibitory concentrations within achievable peak serum levels after standard therapeutic dosage. There was no correlation between cephalosporin resistance and aminoglycoside resistance except for cefoperazone, which, together with the ureidopenicillins and ticarcillin, showed marked decrease in activity against gentamicin-resistant strains.
55% of a sample of patients in a rural
community, and 76% of a sample of patients and
staff in the local district hospital were found to
be nasal carriers for Staphylococcus aureus. The
in vitro antibiotic susceptibility patterns of 46
strains of S. aureus isolated in nasal carriers as
well as of 43 strains in community-acquired skin
infections were characterised. High levels of
resistance were expressed to penicillin (73%),
cephalexin (64%) and tetracycline (46%).
Resistance to erythromycin (18%) was moderate.
A few strains showed resistance to methicillin
(5 isolates), vancomycin (4), [usidic acid (3),
cotrimoxazole (1), and none to gentamicin.
Penicillin can no longer be recommended for
treating community-acquired S. aureus infections.
Twenty-five strains of enterobacteria, isolated from man in Peninsular Malaysia and consisting of seven Enterobacter spp., five Escherichia coli, five Salmonella spp., four Klebsiella spp., two Shigella spp., one Proteus sp. and and one Providencia sp., were tested for antibiotic resistance and conjugative R plasmids. They were all sensitive to nalidixic acid and resistant to at least three antibiotics. The number of resistances ranged from 3 to 11 antibiotics, including cefoperazone and sisomicin (two) newly released antibiotics), in addition to common drugs of current use. Of the 25 isolates, 19 (76%) conjugally transferred, at varied frequencies, at least two resistance determinants. Results from equilibrium density gradient centrifugation, agarose gel electrophoresis and transformation experiments provided proof that the transferable resistances were plasmid-mediated. Restriction endonuclease cleavage patterns showed that the plasmids from Proteus strain K005 and Providencia strain K001 may be identical.
One hundred and thirty eight penicillinase producing Neisseria gonorrhoeae (PPNG) and 239 non-PPNG strains were characterised serologically using a panel of seven monoclonal antibodies directed against protein 1A and seven against protein 1B. An association between serovar and susceptibility to antimicrobial agents, auxotype, and plasmid content was observed. Serogroup WI strains were more sensitive to penicillin, ampicillin, tetracycline, erythromycin, cefoxitin, and cefuroxime. Sixty five (82%) of the 79 WI strains were typed as being serovar Aedgkih, and 47 (72%) of these strains required arginine, uracil, and hypoxanthine for growth (AUH-). Seventy one (44%) of 160 WII/WIII strains were serovar Bacejk, and 42 (59%) of these required proline, citrulline, and uracil for growth (PCU-) and were plasmid free. Serovars Bcgk, Beghjk, Bacjk, and Bajk were associated with resistance to antimicrobial agents. Analysis of PPNG isolates showed a new serovar, Af, which was associated with strains imported from Malaysia and Singapore that required proline and ornithine for growth (Pro-Orn-) and carried the 24.5 megadalton transfer plasmid, the 2.6 megadalton cryptic plasmid, and the 4.5 megadalton penicillinase producing plasmid. Other associations between serovar and geographical location were noted.
Fifty seven strains of Pseudomonas pseudomallei were tested for in vitro susceptibility to 15 antimicrobial agents. Amongst the generally recommended antibiotics for therapy of melioidosis, only 86%, 84% and 58% of the strains were found to be sensitive to trimethoprim-sulphamethoxazole, chloramphenicol and tetracycline respectively. Of the newer B-Iactams, in descending order of activity were, ceftazidime, ceftriaxone, cefotaxime, cefoperazone and cefuroxime. But on a weight for weight basis, ceftazidime was the most active agent and as such, may be considered in the therapy of acute septicaemic melioidosis."
Antibiotic resistance in Gram-negative bacteria, particularly Salmonella and Shigella, requires surveillance worldwide. This study describes results of surveys in Hong Kong, Bangkok and Kuala Lumpur. All strains were isolated in hospitals which have large community catchment areas in addition to specialised hospital units. The prevalence of resistant strains was high in all areas. Gram-negative bacteria such as Enterobacter associated with hospital infections were resistant to penicillins and cephalosporins, with gentamicin resistance ranging from about 20% in Kuala Lumpur and Hong Kong, to 35% in Bangkok. Ninety-seven percent of Shigella isolated in Thailand were resistant to ampicillin. About 10% of Salmonella were resistant to chloramphenicol in all three centres.
Four hundred and ninety-eight predominantly pyocin-type 10 clinical strains of Pseudomonas aeruginosa were analyzed for resistance to carbenicillin, cefoperazone, cefotaxime, ceftazidime, gentamicin, amikacin and netilmicin. Based on NCCLS-recommended MIC breakpoints, 245 strains were found to be resistant, of which 41.6% were resistant to carbenicillin, 38% to gentamicin, 37.8% to netilmicin, 26.3% to cefoperazone, 17.9% to cefotaxime, 0.6% to amikacin and none to ceftazidime. Quadruple resistance to carbenicillin, cefoperazone, gentamicin and netilmicin was the most frequent pattern observed. Resistance to older antibiotics (kanamycin, streptomycin and tetracycline) and to mercuric chloride were also common. Conjugation experiments suggested that self-transmissible and non-transmissible plasmids occurred in at least 66 strains.