Some effect of subinbilitory concentrations of penicillin on the structure and division of staphylococci.

A strain of Staphylococcus aureus was planted on filter membranes placed on Trypticase soy agar (BBL). After incubation, the membranes with growing staphylococci were transferred to Trypticase soy agar containing a subinhibitory concentration of penicillin (one-third minimal inhibitory concentration) and again incubated. The membranes were then returned to drug-free agar and incubated once more. Counts of the colony-forming units and electron microscopy were carried out at several time intervals. When grown on agar containing penicillin, the staphylococci formed what appeared to be abnormally large cells with multiple and unusually thick septa. Examination of a number of sections showed that these large cells were in reality clusters of staphylococci that had divided but failed to separate. When these large cells were subsequently grown on drug-free agar, smaller cells and normal staphylococci emerged. Subinhibitory concentrations of penicillin do not kill staphylococci; they seem to inhibit lysis of cross walls, preventing the separation of otherwise divided cells.     

Moxifloxacin and biofilm production by coagulase-negative staphylococci

The in vitro activity of moxifloxacin against 41 strains of coagulase-negative staphylococci was determined. A relationship between the activity of moxifloxacin and biofilm formation was detected. Biofilm-producing strains were more resistant to moxifloxacin than biofilm-negative strains. Our global results obtained with six strains of Staphylococcus epidermidis showed that subinhibitory concentrations of moxifloxacin did not significantly modify biofilm formation. On the other hand, moxifloxacin concentrations of 2, 10, 50 and 100 x MIC produced a log decrease in viable count (included in a biofilm) of 0.20, 0.37, 1.10 and 1.69, respectively.     

Facilitation of penicillin haptenation to serum proteins.

Traditionally, penicillin binding to serum proteins was believed to be a passive chemical process; however, it appears to be facilitated by serum factors. The objectives of this in vitro investigation were to examine facilitated penicillin haptenation, to study the kinetics of haptenation, and to determine the nature of haptenation-facilitating factors. The model involved addition of [3H]benzylpenicillin to serum or albumin solutions (at pH 7.3 to 7.4) and incubation at 37 degrees C for up to 72 h. The extent of penicillin binding to proteins in serum was found to be four- to fivefold higher than with solutions having comparable concentrations of purified albumin, total protein, or total immunoglobulin. Ultrafiltration of serum reduced penicillin binding to serum proteins substantially. An ultrafiltrable haptenation-facilitating factor(s) was found to be less than 0.5 kDa but was not calcium or magnesium. Finally, the extent of penicillin binding was related to albumin purity, as binding substantially increased with albumin purity. These findings suggest that there is a factor(s) in serum that facilitates covalent binding of penicillin to serum proteins. The factor(s) can be removed and then restored to increase penicillin binding to albumin. It appears that at least one component of the facilitation factor is less than 0.5 kDa, which suggests that it is not a peptide and that it is some simple serum component other than calcium or magnesium.     

Genes involved in the regulation of beta-lactamase production in enterococci and staphylococci.

In enterococci, the structural gene for beta-lactamase (blaZ) is identical to blaZ from Staphylococcus aureus. However, in the enterococci studied to date, beta-lactamase is produced constitutively, whereas in staphylococci it is often inducible. Recent reports have revealed the presence of two adjacent genes upstream of the staphylococcal blaZ thought to be the antirepressor (blaR1) and repressor (blaI) genes. In the present study, beta-lactamase expression mutants of the staphylococcal beta-lactamase plasmid pI524 were generated by transposon mutagenesis with the transposon Tn917. Tn917 insertions upstream of blaZ in either blaR1 or blaI resulted in constitutive beta-lactamase production, indicating that the repressor function is lost with insertion of Tn917 into either gene. This finding supports the concept that the staphylococcal beta-lactamase regulatory genes are encoded on a polycistronic mRNA. The corresponding region upstream of the enterococcal blaZ from Enterococcus faecalis HH22 was sequenced and compared with the staphylococcal blaR1 sequence. The two sequences were identical for 893 nucleotides, and then the sequences diverged completely. Therefore, in strain HH22, only 51% of the putative antirepressor gene is present and the repressor gene is also absent. In conclusion, constitutive beta-lactamase production in HH22 appears to be due to a lack of the regulatory genes blaR1 and blaI which regulate expression of blaZ in staphylococci.     

甲氧西林耐药溶血性葡萄球菌的基因多态性研究

目的应用随机扩增多态性DNA（RAPD）技术,对甲氧西林耐药溶血性葡萄球菌（MRSH）进行基因多态性研究。方法对81株MRSH通过RAPD技术进行扩增,电泳条带采用SPSS13.0软件分析,根据树状图分型。结果81株MRSH通过RAPD技术可产生相对固定的6条电泳带,经遗传相关系数分析后可分为8型,其中A型占70.37%,而10株血培养阳性的MRSH中有9株为A型。结论通过RAPD分型研究,可以了解MRSH基因流行型的特性,为该菌的感染控制提供分子流行病学依据。     

The effect of cultural conditions on the activity of LY146032 against staphylococci and streptococci

The antibacterial activity of LY146032 was greatly potentiated in the presence of calcium ions. In the presence of a physiological concentration of calcium (ca 100 mg/l: 2.5 mM) the new compound was more active than vancomycin or teicoplanin against a selection of clinical isolates of staphylococci and streptococci. The requirement for calcium could not be satisfied by magnesium. The activity of LY146032 varied when tested in different culture media, including batches of Mueller-Hinton agar from different manufacturers. The highest minimum inhibitory concentrations of LY146032 were observed in tests on Iso-Sensitest agar, which contains little calcium. Supplementation of Iso-Sensitest agar with increasing concentrations of calcium caused a proportionate fall in the MIC of LY146032. Saponin-lysed horse blood; incubation in a CO2-rich atmosphere; and an increase in the bacterial inoculum from 10(3) to 10(6) cfu/spot had little effect on the activity of LY146032 in the presence or absence of calcium.     

The binding of penicillin in relation to its cytotoxic action. II. The reactivity with penicillin of resistant variants of streptococci,pneumococci, and staphylococci

1. In a previous study, the differing sensitivity of bacterial strains as they occur in nature appeared to be correlated with their correspondingly differing reactivity with penicillin. Presumably, the over-all reactivity of the cell with penicillin paralleled that of the vulnerable cell component(s). However, when penicillin-resistant variants of these strains (Streptococcus pyogenes, Micrococcus pyogenes, Diplococcus pneumoniae, and Streptococcus faecalis) were produced by serial passage through increasing concentrations of antibiotic, this correlation between resistance and the ability of the cell to bind penicillin was no longer apparent. Some resistant variants bound more penicillin than the parent, sensitive cell (Streptococcus faecalis, Micrococcus pyogenes), some were unchanged in their reactivity (Diplococcus pneumoniae, Micrococcus pyogenes), and some bound less (Streptococcus pyogenes, Micrococcus pyogenes). One resistant variant of Micrococcus pyogenes at first showed enhanced reactivity with penicillin; on continued passage through antibiotic, there was a further increase in resistance, but now associated with a significantly decreased reactivity. In the case of Diplococcus pneumoniae, a resistant variant at first reacted normally with penicillin; on continued passage in antibiotic, its binding affinity for penicillin gradually decreased, but with no associated further increase in resistance. 2. The reactivity with penicillin of cell-free sonic extracts of the resistant variants paralleled that of the intact organisms. Permeability considerations therefore did not seem involved in the increased resistance produced by serial passage in antibiotic. 3. The penicillin-resistant variants did not have an enhanced capacity to degrade the free intracellular antibiotic. 4. Possible alternative explanations are discussed in the text.     

新生儿微量血血清胆红素测定的影响因素分析

目的探讨影响新生儿微量血血清胆红素测定结果的因素。方法对38例黄疽患儿同时采集微量血3份,即刻离心测定微量血清胆红素后,甲份置于室温下不避光,乙份置于室温下避光,丙份置于4℃左右的冰箱保存,待1h、2h、24h及48h再次测定微量血胆红素。结果置于室温下不避光组24h、48h与采血即刻所测微量血清胆红素结果的下降率分别为31．9％和44．5％;室温下避光组24h、48h与采血即刻所测微量血清胆红素结果的下降率分别为：7．6％、12．7％;冰箱组24h、48h与采血即刻所测微量血清胆红素结果的下降率分别为2．6％和3．6％。结论自然光线照射后各时相所测微量血清胆红素值水平明显降低．而在冰箱内低温避光保存后各时相所测微量血清胆红素值水平下降不明显。因此,如当天不能及时测定的标本应该放冰箱避光保存．     

婴幼儿青霉素皮试液量的探讨

目的探讨最适宜的婴幼儿做青霉素皮试的液量。方法对住院的204例小于3岁患儿按入院先后顺序随机分为实验组和对照组。用科室每天配制的青霉素皮试液,配制液为生理盐水500μ/mL,实验组皮试液量为0.05mL,对照组皮试液量为0.1mL,操作方法及结果判断标准按《高等护理学基础教材》。结果两组数据经SPSS13.0统计学软件包进行处理,两样本率的χ2检验结果 :χ2=5.058,两组样本相比较差异有统计学意义(P0.05)。结论 3岁以内的患儿临床上可考虑用含青霉素25U/0.05mL做皮试,以减少假阳性发生。     

Effects of subinhibitory concentrations of vancomycin or cefamandole on biofilm production by coagulase-negative staphylococci.

The density of the biofilm layer produced on a plastic surface by 23 clinical isolates and 1 reference strain of slime-positive, coagulase-negative staphylococci was measured following growth in subinhibitory concentrations (sub-MICs) of cefamandole or vancomycin ranging from 2 to 0.008 micrograms/ml. All strains were susceptible to less than or equal to 2 micrograms of each agent per ml. The mean biofilm density produced by each strain was calculated from a total of eight determinations at each sub-MIC and was compared with the mean biofilm density of a drug-free control after correcting for differences in growth. The results showed that the density of the biofilm layer produced by 10 (42%) of 24 strains and 13 (54%) of 24 strains was significantly increased (P less than 0.006) at one or more sub-MICs of cefamandole or vancomycin, respectively. In contrast, the density of the biofilm produced by 9 (38%) of 24 and 2 (8%) of 24 strains was significantly reduced at one or more sub-MICs of cefamandole and vancomycin, respectively, and the biofilm density of 7 of these strains was decreased only when the sub-MIC was one-half the MIC. The biofilm density of six strains (five versus cefamandole and one versus vancomycin) was both enhanced and reduced by different sub-MICs of the same agent. None of the strains produced a detectable biofilm at or above the MIC for the strain. These data indicate that antimicrobial agents such as cefamandole or vancomycin could potentially enhance the biofilm matrix produced by certain slime-positive, coagulase-negative staphylococci on the surface of a biomedical implant if concentrations of these agents fall below the MIC for the infecting strain.