Cloning and expression of the penicillinase from a borderline methicillin-susceptible Staphylococcus aureus strain in Escherichia coli

The blaZ gene contained in a single 17.2-kb beta-lactamase plasmid from a borderline methicillin-susceptible Staphylococcus aureus strain (a53) has been cloned in Escherichia coli. A Bluescript II derivative in which the ampicillin resistance gene has been replaced with the chloramphenicol resistance gene was used as a multi-copy vector. One ampicillin-resistant colony was detected among 31 chloramphenicol-resistant transformants selected. This E. coli clone harbored a recombinant plasmid (pAH12) containing two different staphylococcal HindIII inserts (7.0 and 5.3 kb), of which only the former hybridized with a blaZ probe. The clone showed an ampicillin MIC of > 1024 micrograms ml-1, independently of the inoculum size used, and produced large amounts of beta-lactamase, which hydrolyzed nitrocefin and penicillin G but not methicillin of the beta-lactamase substrate, padac. In contrast, S. aureus a53 hydrolyzed all four substrates. The fact that high levels of staphylococcal penicillinase are unable to cause methicillin hydrolysis confirms that penicillinase hyperproduction is unlikely to be the true mechanism responsible for the borderline phenotype. These results also suggest that the two different beta-lactamases (penicillinase and methicillinase) associated with borderline S. aureus strains have a different genetic origin.

Dynamics of molecular parameters of human immunodeficiency virus type 1 activity in vivo

The dynamics of viral activity during different phases of human immunodeficiency virus type 1 (HIV-1) infection were investigated by competitive PCR methods. In particular, we studied the time course of three quantitative molecular parameters of viral activity (genomic RNA copy number in plasma and provirus and late HIV-1 transcript molecule copy numbers in peripheral blood CD4+ T lymphocytes) in untreated patients and patients treated with specific anti-HIV-1 compounds. The results shown here indicate that direct RNA parameters are quantitative molecular indices sensitive enough to be used for a more accurate evaluation of the natural history of this infection and that an indirect parameter, the mean transcriptional activity for each provirus in CD4+ T lymphocytes, may be important in studying this infection in vivo at the molecular level. A dramatic decrease of the indices was evident at seroconversion, but the quantitative values were virtually stable throughout the time the untreated patients were studied during the clinical latency phase. Furthermore, the results indicate that an early response to antiretroviral compounds is detected in most subjects as a decrease in the viral activity level.

Micrococci demonstrate a phosphatase activity which is repressed by phosphates and which can be differentiated from that of staphylococci

The phosphatase activities of 114 micrococcal strains belonging to seven different species and of an additional 150 unspeciated micrococcal strains were evaluated on solid media at various pHs containing or not containing phosphates. In the presence of phosphates, only nine strains (five unspeciated strains, one Micrococcus luteus strain, and three Micrococcus varians strains) yielded a positive reaction on plates at pH 8. In media (at pH 8) deprived of phosphates, in contrast, all but 15 strains demonstrated clear-cut phosphatase activity. Acid phosphatase could not be evaluated on solid media since none of the strains grew satisfactorily on plates at pH 5. The phosphatase activities of seven (one or two for each species, which included phosphatase-negative strains) of the strains whose colonies proved phosphatase negative at pH 8 and of 18 (two or three strains per species) of those with phosphatase-positive colonies were evaluated at pH 5 and 8.5 in toluene-treated cells which had been grown in liquid media at pH 7 containing or not containing phosphates. All strains demonstrated distinct phosphatase activity at both pHs when grown in media not containing phosphates. In contrast, when strains were grown in the presence of such substances, virtually no activity was observed at pH 8.5, and, generally, a much reduced activity was observed at pH 5. The phosphatase activity of micrococci of the various species (three to eight strains per species) was also compared with that of staphylococci of different species (5 to 10 strains per species) by the methyl green-phenolphthalein diphosphate method, the sensitivity of which can be varied by using different enzyme substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Survey of clinical isolates of Staphylococcus aureus for borderline susceptibility to antistaphylococcal penicillins

On the basis of the MICs of methicillin and oxacillin, 975 clinical isolates of Staphylococcus aureus were categorized as having resistance, borderline susceptibility or full susceptibility to penicillinase-resistant penicillins (PRPs). The borderline phenotype accounted for 122 isolates (12.5%), whereas 562 isolates were fully susceptible and 290 resistant; one remaining isolate had resistance to methicillin and borderline susceptibility to oxacillin. Reductions in the MICs of methicillin and oxacillin in the presence of sulbactam were greater in strains with borderline PRP susceptibility than in fully susceptible or resistant isolates. Over 99% of fully PRP-susceptible strains, 93% with borderline susceptibility and 71% of resistant strains were susceptible to ampicillin/sulbactam. The production of beta-lactamase, assayed in all strains using nitrocefin as substrate, could be detected without prior induction in 729 strains and after induction only in another 156 strains. With only two exceptions, the beta-lactamase negative strains were part of the fully PRP-susceptible group of organisms (88 of 562 isolates). Among the borderline isolates, strong beta-lactamase reactions were encountered with particular frequency, but not in all strains and not exclusively in borderline strains. Although associated with the majority of borderline strains, beta-lactamase hyperproduction thus did not appear to be an essential feature of the borderline phenotype. The results obtained may have implications for laboratory and clinical medicine, also in the light of recent findings suggesting that other mechanisms besides beta-lactamase hyperproduction may account for borderline susceptibility to PRPs.

Genetic basis of tetracycline resistance in food-borne isolates of Listeria innocua

Eleven of 12 tetracycline-resistant Listeria innocua strains, isolated from chicken or turkey frankfurters and mozzarella cheese, were shown to carry DNA sequences which hybridized with the Tet M probe; of these, two strains also hybridized with Tet K. The remaining strain hybridized with the Tet K probe only. The Tet M determinant appeared to be located on the chromosome; in one case, it was transferable by conjugation to recipients Listeria monocytogenes, Listeria ivanovii, and Enterococcus faecalis.

Molecular profile of human immunodeficiency virus type 1 infection in symptomless patients and in patients with AIDS

Recent molecular evidence indicates that active human immunodeficiency virus type 1 (HIV-1) infection is detectable in both symptomless and symptomatic infected patients. For this main reason, it has been pointed out that precise quantitative analysis of viral activity in vivo is necessary, firstly, for the pathogenetic investigation of the steps relevant to infection progression and, secondly, for better clinical management of HIV-1-infected patients. In this study, the presence of HIV-1 genomic RNA in plasma samples, specific HIV-1 transcripts in peripheral blood mononuclear cells, and proviral DNA sequences were assayed for 33 HIV-1-infected patients (including symptomless and symptomatic subjects) by using a competitive polymerase chain reaction method that allows quantitation of the RNA/DNA target sequences. The quantitative results obtained confirm that transcription of HIV-1 structural genes and complete viral replication occur in all the HIV-1-infected patients independently of the clinical stage. However, although sharp individual differences were detected, a high degree of correlation of the molecular parameters studied with both disease progression and a decrease in the number of CD4+ T lymphocytes was documented. Interestingly, despite the increasing viremia level associated with infection progression, the mean transcriptional activity of individual infected cells was found to be only moderately greater in AIDS patients than in asymptomatic infected subjects. In addition, it was noted that quantitation of HIV-1 genomic RNA in plasma samples and quantitation of specific HIV-1 transcripts in peripheral blood mononuclear cells appear to be more reliable and sensitive markers of viral activity than quantitative analysis of proviral HIV-1 sequences in peripheral lymphocytes.

Absolute quantitation of viremia in human immunodeficiency virus infection by competitive reverse transcription and polymerase chain reaction

A competitive polymerase chain reaction (PCR)-based assay for the quantitative detection of human immunodeficiency virus type 1 (HIV-1) viremia was developed and optimized. This method consists of the reverse transcription and subsequent amplification in the same tube of two similar RNA templates, the wild-type template to be quantified and a known amount of the internally deleted synthetic template, both with identical primer recognition sites. The same strategy also proved to be useful in the quantitative assay of HIV-1-specific cellular transcripts and proviral DNA sequences from peripheral blood mononuclear cells by using competitor DNA. The method might be of interest in the study of the precise level of HIV-1 activity during the different clinical phases of the infection and in the simple, fast, and methodologically correct molecular investigation of patients treated with specific antiviral compounds.

Sequence analysis of the hepatitis B virus pre-C region in hepatocellular carcinoma [HCC] and nontumoral liver tissues from HCC patients

We investigated whether replication-competent pre-C/C defective mutants of hepatitis B virus (HBV) are detectable in primary human hepatocellular carcinoma (HCC) tissues from patients of a geographic area endemic for such mutants. DNAs extracted from formalin-fixed paraffin-embedded HCC samples were checked for the presence of specific HBV DNA sequences using the polymerase chain reaction (PCR). Amplified pre-C regions from nine HCC samples were directly sequenced as were samples of nontumoral liver tissues from five of these patients. The data show that hypervariable distal pre-C sequences were present in all nine HCC samples; this high variability was dependent on point mutations, which led to amino acid substitutions in nearly all cases. Interestingly, seven of the nine HBV DNA-positive samples from HCC tissues (but not samples from peritumoral liver tissue) showed mutations leading to amino acid substitution at the level of a distal cysteine residue. No mutation generating a translationally defective pre-C/C region was detectable in the tumor samples. Otherwise, in four of the six nontumoral liver tissues available from the same patients, a pre-C sequence with an in-frame TAG stop codon was detectable, although in three cases as a component of mixed population.

Evidence for a methicillin-hydrolysing beta-lactamase in Staphylococcus aureus strains with borderline susceptibility to this drug

A new beta-lactamase that hydrolyses methicillin was found in the membrane fraction of two clinical isolates of Staphylococcus aureus with borderline susceptibility to this drug. 'Methicillinase' activity was detected in renatured sodium dodecyl sulfate polyacrylamide gel electrophoretograms of staphylococcal membrane proteins. The enzyme activity appeared to be inducible and was more easily detected using penicillin G (or methicillin) rather than nitrocefin as substrate. Similar activity was not detected in the membrane fraction of a methicillin-susceptible strain. These results suggest that, in the two borderline susceptible strains, rather than a hyperproduction of the penicillinase a specific methicillin-hydrolysing activity is responsible for the borderline susceptible phenotype.

Human immunodeficiency virus type 1 and hepatitis B virus transcription in peripheral blood lymphocytes from co-infected subjects

The molecular characteristics of peripheral blood lymphocyte (PBL) infection by hepatitis B virus (HBV) were studied in human immunodeficiency virus type 1 (HIV-1) infected subjects using highly sensitive polymerase chain reaction (PCR) based techniques. DNA and RNA samples were purified from PBLs of HIV-1 infected individuals, regardless of their HBV serological status and assayed using PCR and reverse-transcription (RT) PCR, respectively. The data shown here are an extension of previous reports documenting HBV and HIV-1 co-infection of PBLs and indicate that transcriptionally active HBV infection of PBLs is detectable in a significant proportion of asymptomatic HIV-1 infected patients.

Lack of detectable human T-cell lymphotropic virus type I sequences in samples from multiple sclerosis patients

Recently, inconclusive results have followed the early data on the possible association between multiple sclerosis (MS) and human T-cell lymphotropic virus type I (HTLV-I) infection. For this reason, we examined this hypothesis using the polymerase chain reaction (PCR) to study samples of differing origin from Italian MS patients. In particular, we developed a systematic analysis of paraffin-embedded brain white matter from histologically defined lesions of 14 MS patients using PCR and primer sets specific for HTLV-I sequences; additionally, cerebrospinal fluids (CSFs) from 12 patients and peripheral blood mononuclear cells (PBMCs) from subjects at the early and late phase of the disease were investigated for free HTLV-I virions and specific proviral sequences, respectively. In agreement with some groups who reported lack of HTLV-I sequences in PBMCs of MS patients but in clear contrast with others, we failed to detect specific viral sequences using this broad approach.

In vitro activities of three semisynthetic amide derivatives of teicoplanin, MDL 62208, MDL 62211, and MDL 62873

MDL 62208, MDL 62211, and MDL 62873 are three semisynthetic amide derivatives of teicoplanin (MDL 62208 is an amide of teicoplanin aglycone, MDL 62211 is an amide of the teicoplanin A2 complex, and MDL 62873 is the corresponding derivative of peak A2-2 of the complex). The three semisynthetic glycopeptides were evaluated for in vitro antibacterial activity in comparison with the parent drug (teicoplanin) and vancomycin. A variety of gram-positive bacteria of clinical origin, whose species were carefully determined and that included 428 staphylococci (207 methicillin susceptible and 221 methicillin resistant), 41 streptococci, 82 enterococci, 43 strains of Listeria monocytogenes, 10 JK coryneform bacteria, and 67 anaerobes belonging to the genera Clostridium, Propionibacterium, Peptostreptococcus, and Eubacterium, were tested. The only resistances to MDL 62208, MDL 62211, and MDL 62873 were encountered with vancomycin- and teicoplanin-resistant enterococci. All of the other test strains, including some teicoplanin-resistant coagulase-negative staphylococci of the species Staphylococcus haemolyticus and Staphylococcus epidermidis, were highly susceptible to the three teicoplanin amides. Only minor differences in activity were observed among MDL 62208, MDL 62211, and MDL 62873, whereas the three experimental compounds were usually found to be more potent than teicoplanin or vancomycin (especially against staphylococci, with differences mostly ranging from 2- to 16-fold). The MBC-to-MIC ratios varied depending on the organisms, with the highest ratios usually observed for enterococci and listeriae. Overall, the MBC-to-MIC ratios yielded by the teicoplanin analogs were slightly greater than those yielded by teicoplanin or vancomycin.

Haemophilus parainfluenzae causing sexually transmitted urethritis. Report of a case and evidence for a beta-lactamase plasmid mobilizable to Escherichia coli by an Inc-W plasmid

A multiple antibiotic resistance, beta-lactamase-producing strain of Haemophilus parainfluenzae was isolated from a patient with sexually transmitted urethritis that was contracted in Northwest Africa. The strain was found to harbor a small (3.2 megadaltons) plasmid encoding for beta-lactamase production, which was successfully mobilized to Escherichia coli in triparental mating experiments by means of a broad host-range Inc-W conjugative plasmid. Since H. parainfluenzae is believed to be a source and reservoir for the spread of beta-lactamase plasmids to other bacterial species, such a plasmid mobilization may suggest a new possible means for resistance plasmid dissemination.

Staphylococcal endo-beta-N-acetylglucosaminidase inhibits response of human lymphocytes to mitogens and interferes with production of antibodies in mice

The effect of a bacteriolytic enzyme, the endo-beta-N-acetylglucosaminidase excreted by Staphylococcus aureus (SaG) on the response of human lymphocytes to mitogens and on the immune response in mice has been studied. SaG inhibited incorporation of [3H]thymidine into TCA-precipitable material by human peripheral lymphocytes stimulated either by phytohemagglutinin or by concanavalin A, as well as formation of cytoplasmic immunoglobulin-containing cells by B lymphocytes treated with pokeweed mitogen. In all cases the level of inhibition first increased with the SaG concentrations reaching values of over 80% at an enzyme concentration of 100 micrograms/ml, and then decreased. Heat-inactivated SaG as well as SaG treated with both polyclonal and monoclonal specific antibodies or enzyme inhibitors such as chitotriose or hydrolyzed peptidoglycan had no effect on lymphocyte response to mitogens. In mice, SaG at a dose of 300 micrograms per mouse was found to cause a fourfold decrease in the anti-BSA antibody titer and an approximately 70-75% reduction in the immunoglobulin-containing cells in the spleens of mice injected with sheep red blood cells. SaG also completely abolished the enhancing effect of adjuvants such as muramyldipeptide, Freund's complete adjuvant, and Escherichia coli lipopolysaccharide. When SaG was injected into mice together with S. aureus peptidoglycan hydrolyzed either by SaG or by human lysozyme, the inhibitory effect on both production of anti-BSA circulating antibodies and appearance of Igc cells in the spleens of mice injected with sheep red blood cells was enhanced. As we know that (a) human tissues contain endo-beta-N-acetylglucosaminidases; (b) other human hexosaminidases (lysozymes) have previously been shown to interfere with the functions of immunocompetent cells; and (c) products of hexosaminidase hydrolysis of peptidoglycan (muropeptides) known to modulate immune response are ordinarily found in the urine of healthy persons, the possibility that hexosaminidases play a major role in the regulation of the immune response is raised and discussed.

Detection of human immunodeficiency virus type 1 genomic RNA in plasma samples by reverse-transcription polymerase chain reaction

An application of the polymerase chain reaction (PCR) to the direct detection of human immunodeficiency virus type 1 (HIV-1) viremia is described. The amplification of specific HIV-1 sequences of gag and env viral genes was carried out after the reverse-transcription of plasma samples (plasma RT-PCR) from seropositive subjects. The assay is faster and cheaper than detection of specific HIV-1 transcripts from peripheral blood mononuclear cells by RT-PCR. The data suggest that HIV-1 viremia is detectable by plasma RT-PCR in a large proportion of seropositive individuals.

Serological follow-up of patients involved in a localized outbreak of leptospirosis

Eighteen patients involved in a localized outbreak of leptospirosis were subjected to a serological follow-up study over a 5-year period. Four distinct sets of sera from all patients and a fifth sample obtained from 10 of them were examined by the microscopic agglutination test (MAT) for demonstration of leptospiral antibodies. The test was carried out by using live leptospires from reference strains of 17 Leptospira interrogans serovars known to occur in Italy. In all cases, the highest titers of agglutinins were recorded against one or more of the three Australis group serovars tested (australis, bratislava, and lora). The highest antibody levels were reached soon after the acute phase of infection in some patients but only after some months in others. Titers then tended to recede with varying rapidity, but titers against the Australis group serovars were still detectable in some patients after 5 years. Coagglutinins against serovars of other serogroups were detected, generally at low levels, in the early sets of sera of most patients, but tended to disappear in the late-set sera. Specific immunoglobulin M (IgM) and IgG against the three Australis group serovars were determined in most serum samples from 16 patients by solid-phase enzyme immunoassay (EIA). In general, EIA titers were considerably lower than MAT titers, but there was a certain patient-to-patient variability in both the IgM/IgG ratio and the evolution and persistence of the two immunoglobulin classes. Since all the evidence indicated that the initial outbreak from a single source, the observed patient-to-patient variability in the progress of both MAT and EIA titers appeared to be attributable to factors inherent in the individual patients. Cross agglutination absorption tests, aimed at retrospectively determining to which of the Australis group serovars the outbreak-specific infecting strain belonged, were performed with six serum samples from different patients. Most absorbed sera seemed to originate from an australis or lora infection, but it was not possible to discriminate conclusively between the two serovars.

Detection of human immunodeficiency virus type 1 transcripts in peripheral blood lymphocytes by the polymerase chain reaction

A simplified application of the polymerase chain reaction (PCR) to the routine detection of human immunodeficiency virus type 1 (HIV-1) transcripts from peripheral lymphocytes of infected subjects is described. This technique is simpler than previously described assays and was shown to be highly sensitive after ethidium bromide staining of polyacrylamide gel electrophoresis of amplified material. The method can be used for the virologic evaluation of HIV-1-infected subjects, thus allowing early identification of seropositive patients with signs of active infection.

Selection of resistance to glycopeptide antibiotics in staphylococci

Clinical strains belonging to ten Staphylococcus species were investigated for their abilities to develop single-step resistance in vitro to vancomycin and teicoplanin. Surviving clones were only recovered from strains of three species, namely S. aureus, S. epidermidis, and S. haemolyticus. A similar ratio of grown to plated cells (approximately 1 x 10(-8)) was mostly obtained from strains of S. aureus and S. epidermidis. Higher ratios (1 x 10(-6) to 1 x 10(-7)) were obtained from strains of S. haemolyticus, especially when exposed to teicoplanin. When tested for susceptibility, many survivors exhibited vancomycin and teicoplanin minimum inhibitory concentrations (MICs) below the drug concentration used for in vitro selection, probably due to an inoculum effect in the plating procedure. However, MICs were particularly high in many clones of S. haemolyticus (up to 12.8 microg/ml for vancomycin, and > or = 102.4 microg/ml for teicoplanin).

Activity of roxithromycin against respiratory pathogens

The usefulness of macrolides in treating respiratory infections has been established for over thirty years. Currently, a great deal of interest is being focused on roxithromycin, a new semisynthetic derivative of erythromycin which is more stable than erythromycin under acidic conditions and exhibits improved pharmacokinetic properties. In this study, special attention is paid to the results of recent multicenter studies in Italy aimed at evaluating the in vitro activity of roxithromycin versus erythromycin against a wide range of respiratory pathogens. Considering that a high degree of overlap was observed between the roxithromycin-susceptible and the erythromycin-susceptible strains, whereas a significant proportion of erythromycin-resistant strains shifted to the intermediate category with roxithromycin, there appeared to be cross-susceptibility rather than cross-resistance between the two macrolides.

Development of in-vitro resistance to glycopeptide antibiotics: assessment in staphylococci of different species

Forty-two clinical isolates belonging to ten species of staphylococci were studied for their ability to develop single-step resistance, in vitro, to glycopeptide antibiotics. Selection was attempted through separate exposure to four glycopeptides (vancomycin, teicoplanin, and two investigational semisynthetic derivatives of the latter, TD-A3 and CTA-A1) on agar containing 10 mg/l of the test drug. No survivors from any test strain were recovered after exposure to TD-A3 or CTA-A1. After exposure to vancomycin or teicoplanin, surviving clones were only recovered from strains of three species, Staphylococcus aureus, S. epidermidis, and S. haemolyticus. Emergence of resistant clones was easier to observe from strains of S. haemolyticus exposed to teicoplanin. When tested for susceptibility, many survivors exhibited vancomycin and teicoplanin MICs below the drug concentration used for in-vitro selection, probably due to an inoculum effect in the plating procedure. In particular, the vancomycin MICs did not exceed 8 mg/l for S. aureus and S. epidermidis clones, and reached 16 mg/l for some clones from a S. haemolyticus strain. Teicoplanin MICs did not exceed 8 mg/l for S. aureus clones, but reached 64 mg/l for some clones of S. epidermidis, and were particularly high (64 to greater than or equal to 128 mg/l) for most clones of S. haemolyticus. In contrast, against all clones selected from all three species, the MICs of TD-A3 and CTA-A1 did not exceed 2 and 4 mg/l, respectively. Morphological investigations indicated that the colonies of a highly resistant S. haemolyticus clone were smaller and more butyraceous in consistency than those of the parent strain. In transmission and scanning electron microscopy studies, this same S. haemolyticus clone showed a more irregular cell wall than the parent strain.

In vitro activities of ramoplanin and four glycopeptide antibiotics against clinical isolates of Clostridium difficile

Seventy strains of Clostridium difficile, all isolated from symptomatic patients, were found to be uniformly susceptible to ramoplanin, a new glycolipodepsipeptide antibiotic, and to four glycopeptides (vancomycin, teicoplanin, and two semisynthetic teicoplanin derivatives). Ramoplanin is recommended for further evaluation in the treatment of C. difficile-associated disease.

Phosphatase activity of staphylococci is constitutive in some species and repressed by phosphates in others

The phosphatase activities of colonies of staphylococcal strains belonging to the 10 species most frequently isolated from specimens of human origin were evaluated on media with undetermined inorganic phosphate contents and on media supplemented with known amounts of phosphates. All strains of all species tested were phosphatase positive on plates that were not supplemented with inorganic phosphates when the pH of the medium was high. In media supplemented with 0.3% phosphates at low and high pH, all strains of Staphylococcus aureus, almost all strains of S. epidermidis and S. xylosus, and none of the other species tested were phosphatase positive. Thirty S. simulans strains were grown in broths at pH 7 with and without phosphates, and the phosphatase activities of the cells were assayed at pH 5.5 and 8 in the absence of phosphates. At pH 8, all strains gave a strong positive reaction when grown in the absence of phosphates and a negative reaction when grown in the presence of these salts at 0.3%. It was concluded that all the species of staphylococci tested possess phosphatase activity and that the staphylococcal phosphatases are constitutive in some species and repressed in others.

Antimicrobial properties of N-carboxybutyl chitosan

N-Carboxybutyl chitosan, a modified chitin of crustacean origin, displayed inhibitory, bactericidal, and candidacidal activities when tested against 298 cultures of various pathogens. Examination by electron microscopy showed that microbial cells exposed to N-carboxybutyl chitosan underwent marked morphological alterations. The data are of importance in defining the suitability of N-carboxybutyl chitosan as a wound dressing.

Circulation in Italy of beta-lactamase-producing strains within the major groups of bacterial pathogens

A multicenter study was undertaken in Italy to assess the circulation of beta-lactamase-producing organisms and their current incidence within the major groups of bacterial pathogens. Almost four thousand strains, all freshly isolated from clinical material, were examined at four centers serving different areas of Italy. Despite some significant center-to-center differences, this survey documented the occurrence of a large overall circulation of beta-lactamase-producing organisms among clinical bacterial isolates. In particular, ampicillin resistance was recorded in one third to one half of the isolates of some Enterobacteriaceae, including Escherichia coli, Proteus, and Citrobacter species, and 80-90% of these resistant strains proved to be beta-lactamase producers. Both ampicillin resistance and beta-lactamase production were almost the rule in other Enterobacteriaceae, including Klebsiella, Enterobacter, and Serratia species. beta-lactamase was also produced by about 80% of glucose-non-fermenting gram-negative bacteria and Aeromonas hydrophila strains, by all of the isolates of Branhamella catarrhalis manifesting ampicillin resistance (i.e. more than half the total number of isolates), and by about two thirds of the ampicillin-resistant Haemophilus strains (which accounted for 20-25% of all Haemophilus isolates examined). In contrast, no beta-lactamase producers were observed among Neisseria gonorrhoeae isolates.

Further characterization of borderline methicillin-resistant Staphylococcus aureus and analysis of penicillin-binding proteins

Eighty-nine Staphylococcus aureus strains were grouped according to their susceptibility or resistance to methicillin and oxacillin. The role of beta-lactamase in borderline methicillin resistance was confirmed by tests with beta-lactamase inhibitors, particularly when salt-supplemented medium was used. A penicillin-binding protein assay indicated that borderline methicillin-resistant S. aureus strains do not produce PBP 2a.

Preliminary study of breastfeeding and bacterial adhesion to uroepithelial cells

The oligosaccharide content of breast-milk and urine from ten nursing mothers and their babies, collected 30 days after delivery, was analysed by thin-layer and high-performance liquid chromatography. Each woman's milk and urinary oligosaccharide profiles were very similar, and the pattern of oligosaccharides excreted by her infant was also strongly correlated with that of her milk. The babies excreted 300-500 mg/day oligosaccharides and the mothers 500-800 mg/day. The effect of oligosaccharide fractions from a 500 ml pool of colostrum on bacterial adhesion to uroepithelial cells was tested on a strain of Escherichia coli isolated from an infant with urinary tract infection. The high-molecular-weight sialylated oligosaccharides had no effect but neutral oligosaccharides caused inhibition of bacterial adhesion which rose as the size of the oligosaccharides decreased. These findings suggest that breastfeeding may have a preventive effect on urinary tract infection in both mother and infant.

Use of DNA fingerprinting in an epidemiologic study of outbreak-specific and non-specific strains of group C Neisseria meningitidis

DNA fingerprints of nine group C isolates of Neisseria meningitidis were obtained by digestion with three restriction endonucleases, BamHI, EcoRI, and HindIII. Identical restriction profiles were displayed by five strains isolated from two patients and three contacts during a localized outbreak of meningococcal disease in the area served by our laboratory. A slight difference, appreciable only in the fingerprints obtained with EcoRI, was observed between these isolates and a sixth one isolated from a clinical case occurring in the same area one year later. In contrast, three additional strains, recently isolated from patients in separate areas in Italy, gave restriction profiles differing strikingly from one another and from those produced by the strains isolated in our area.

In vitro activity of sulbactam/ampicillin against ampicillin-resistant, beta-lactamase-producing bacteria isolated in Italian hospitals

A multicenter study aimed at assessing the in vitro activity of sulbactam/ampicillin against a wide range of bacterial pathogens was performed using 2,209 clinical strains, all recently collected from inpatients in seven Italian centers and preliminarily screened as being ampicillin-resistant and beta-lactamase producers. In comparative disk diffusion trials using 8 large-spectrum antimicrobials, the percentage of resistance to sulbactam/ampicillin in staphylococci was similar to the percentage of resistance to netilmicin and lower than to the other antibiotics; with gram-negative bacteria, only netilmicin, ofloxacin, and, less consistently, cefotetan showed lower incidences of resistance. The minimal inhibitory concentrations (MICs) of ampicillin alone and sulbactam/ampicillin together were determined using the agar dilution method. The Enterobacteriaceae strains which shifted to ampicillin susceptibility in the presence of sulbactam averaged 68%, but values significantly above or below average were observed in some genera of this family. The percentage of strains which the presence of sulbactam rendered ampicillin-susceptible in vitro reached 97% in Haemophilus strains and 100% in branhamellae and gonococci. High percentages were also recorded in staphylococci, with a peak of 100% in oxacillin-susceptible Staphylococcus aureus strains. In general, center-to-center differences were relatively limited.

Detection of hepatitis B virus DNA in serum using synthetic non-radioactive oligonucleotides

A rapid and simplified technique for detecting hepatitis B virus (HBV) DNA by spot hybridisation in the sera of patients with different clinical forms of HBV infection was investigated using enzyme conjugated synthetic oligodeoxyribonucleotides as probes. These are able to hybridize to the S and C regions of the HBV L(-) DNA strand. When compared with a complete 32P-labelled HBV DNA probe, the synthetic oligonucleotides provided a sensitive and quick method for the routine survey of HBV infection. Moreover, the DNA extraction procedure used allowed the spot hybridisation technique to be applied and read easily and the results obtained within a few hours. It is concluded that synthetic cold probes can be used in hybridisation assays HBV DNA detection as part of current clinical laboratory procedures.

Lysozyme-induced inhibition of the lymphocyte response to mitogenic lectins

Both human lysozyme (HL) and hen egg white lysozyme (HEWL) inhibited the proliferative response of peripheral blood lymphocytes to T cell mitogens such as the lectins phytohemagglutinin and concanavalin A. This inhibition was observed both when HL or HEWL was added to the lymphocyte cultures in combination with phytohemagglutinin or concanavalin A and when lymphocytes were pretreated with either lysozyme and extensively washed prior to culture with mitogens. Under both conditions, the effects were strictly dose dependent; the lysozyme concentrations yielding maximal inhibitory effect were 5 micrograms/ml for HL and 1 microgram/ml for HEWL, while both lower and higher concentrations were less effective. Specific antilysozyme rabbit sera completely prevented the inhibitory effects of both HL and HEWL on the proliferative response of lymphocytes to phytohemagglutin or concanavalin A. Chitotriose (a lysozyme inhibitor) caused a strong reduction in the inhibitory effects of the two lysozymes on the lymphocyte response to either lectin. HL and HEWL also were found to markedly inhibit the polyclonal B cell proliferation and differentiation induced by pokeweed mitogen and T cells. A less marked inhibition was also obtained when T cells, but not B cells, were pretreated with HL or HEWL. Again, as in the experiments with T cell mitogens, the effects were dose dependent and 5 micrograms/ml HL and 1 microgram/ml HEWL proved to be the most effective concentrations. The possible mechanisms by which lysozyme inhibits the lymphocyte response to mitogenic lectins are considered and discussed. The enzymatic activity seemed to perform an essential function, as shown by the loss of effect when the heat- or trypsin-inactivated lysozymes were used and by the fact that only the enzymatically active compound, among certain semisynthetic derivatives of HEWL, inhibited the lymphocyte response to the mitogens. However, the cationic properties of the lysozyme molecule appeared to be essential too, since enzymes with a similar specificity of action showed effects similar to those observed with HL or HEWL only when they carried a strong positive charge. It is suggested that lysozyme, which is naturally secreted by monocytes and macrophages, might interact with lymphocyte surface receptor sites and participate in the complex mononuclear phagocyte-lymphocyte interactions and in the modulation of lymphocyte activation.

Immunity assessment in the early stages of amyotrophic lateral sclerosis: a study of virus antibodies and lymphocyte subsets

Serum and CSF from 32 patients with idiopathic ALS, 30 age-matched controls and 30 MS patients were investigated regarding immunoglobulin concentration and virus-specific antibodies, the lymphocytes in the peripheral blood and lymphocyte subsets were also investigated. ALS patients' results were compared with findings in MS and controls. The ALS patients had significantly higher IgG concentration in serum than the controls, marked lymphopenia, reduction of CD2, CD8 and Leu 7 positive cells and increase of the CD4/CD8 ratio and of SIg-positive lymphocytes. Compared with the MS patients, the ALS patients showed similarity in T-subset distribution with a lower standard deviation. No HTLV-I and HIV antibodies were found in any group and no significant differences in antibody distribution to Toxoplasma G, herpes simplex, cytomegalovirus, measles and mumps viruses were evident. All ALS patients were investigated at an early disease stage, therefore, our findings seem to support the conclusion that the immune alterations are related to the mechanisms of the disease and not to complications of its evolution.

Distribution and antibiotic susceptibility of extraintestinal clinical isolates of Klebsiella, Enterobacter and Serratia species

A total of 451 extraintestinal, clinically relevant strains of the Klebsiella, Enterobacter and Serratia spp. isolated over a nine-month period from hospitalized patients at four different centers in Italy were investigated. Identification using the API 20E system showed that isolates belonged to 12 different species. Overall, strains of Klebsiella, Enterobacter and Serratia were in a ratio of approximately 3.4:2:1. Fifty-nine per cent of all strains were from urinary specimens, 12% from respiratory secretions, 10% from wounds and abscesses, and lower percentages from other sources. All strains were tested for their susceptibility to ten antibiotics. The rate of resistance to most drugs was generally greater in Enterobacter and Serratia than in Klebsiella. The overall incidence of strains of the intermediate category (i.e. between full sensitivity and resistance) was unexpectedly high. Both the relative frequency and the antibiotic susceptibility of strains of the various species varied from center to center; possible reasons for such differences are examined.