Haemophilus aphrophilus discitis and vertebral osteomyelitis

An unusual case of discitis and vertebral osteomyelitis due to Haemophilus aphrophilus is described. Infections due to this organism have usually responded to treatment with beta-lactam antibiotics. However, our isolate was resistant to third-generation cephalosporins which has not been reported previously in the world literature. The patient made a good clinical response to ciprofloxacin treatment.

The pathogenicity of enterococci

In order to produce infection, enterococci must be able to colonize host tissues, resist the host's non-specific and immune defence mechanisms and produce pathological changes. With regard to colonization of host tissues, adherence assays have shown that enterococci can attach to intestinal and urinary tract epithelial cells and heart cells by means of adhesins expressed on the bacterial surface. The expression of these adhesins by enterococci has further been shown to be affected by bacterial growth conditions. In addition, the adherence of Enterococcus faecalis to renal tubular cells in vitro is enhanced if the organisms produce aggregation substance, a proteinaceous surface material that aggregates donor and recipient bacteria to facilitate plasmid transfer. Bacterial growth conditions also affect the interaction of enterococci with polymorphonuclear leucocytes (PMNLs), with serum-grown organisms showing less association with PMNLs than organisms grown in broth. Efficient killing of enterococci by PMNLs in vitro requires the presence of serum complement proteins and is enhanced by anti-enterococcal antibodies. Enterococci produce a number of factors that may be associated with pathological changes in the host. Both sex pheromones and plasmid-encoded pheromone inhibitors produced by E. faecalis are chemotactic for PMNLs in vitro, and may mediate, at least in part, the inflammatory response often associated with enterococcal infection. E. faecalis may also produce a plasmid-encoded haemolysin, which is associated with increased severity of infection. In addition, enterococci are capable of inducing platelet aggregation and tissue factor-dependent fibrin production, which may be relevant to the pathogenesis of enterococcal endocarditis.(ABSTRACT TRUNCATED AT 250 WORDS)

Speech restoration following total laryngo-pharyngectomy with free jejunal repair

Nine patients who have undergone total laryngo-pharyngectomy with free jejunal reconstruction between 1984 and 1993, have had Blom-Singer valves inserted. All patients had little or no voice prior to valve insertion, compared with a good but gravelly voice after valve insertion. Tracheo-oesophageal puncture and valve insertion provides a safe and reliable means of restoring voice after laryngo-pharyngectomy with free jejunal repair.

Vertebro-carotid anastomosis as a cause of uncontrollable epistaxis

Uncontrolled epistaxis may require a long hospital stay, multiple blood transfusions and multiple arterial ligations. This case report highlights vertebro-carotid anastomosis as a rare cause of uncontrolled epistaxis. The importance of angiography in the identification of rare arterial anastomoses is stressed.

Gentamicin resistance in clinical isolates of Escherichia coli encoded by genes of veterinary origin

Seven (27%) of 26 gentamicin-resistant human clinical isolates of Escherichia coli were resistant to the veterinary aminoglycoside antibiotic apramycin. A gentamicin-resistant Klebsiella pneumoniae isolate from a patient infected with gentamicin/apramycin-resistant E. coli was also resistant to apramycin. DNA hybridisation studies showed that all gentamicin/apramycin-resistant isolates contained a gene encoding the enzyme 3-N-aminoglycoside acetyltransferase type IV (AAC[3]IV) that mediates resistance to gentamicin and apramycin in bacteria isolated from animals. Seven of the eight gentamicin/apramycin-resistant isolates were also resistant to the veterinary antihelminthic agent hygromycin B, a phenomenon observed previously in gentamicin/apramycin-resistant Enterobacteriaceae isolated from animals. Resistance to gentamicin/apramycin and hygromycin B was co-transferable in six of the isolates. Restriction enzyme analysis of plasmids in apramycin-resistant transconjugants derived from E. coli and K. pneumoniae isolates from the same patient were virtually identical, suggesting that inter-generic transfer of plasmids encoding apramycin resistance had occurred in vivo. These findings support the view that resistance to gentamicin and apramycin in clinical isolates of E. coli results from the spread of resistant organisms from animals to man, with subsequent inter-strain or inter-species spread, or both, of resistance genes on transferable plasmids.

Genetics of oxacillin resistance in clinical isolates of Streptococcus pneumoniae that are oxacillin resistant and penicillin susceptible

It has recently been reported that penicillin-sensitive pneumococci may exhibit reduced susceptibility to oxacillin, resulting in their misclassification as being penicillin resistant by oxacillin disk testing. Intermediate oxacillin resistance (MIC, 1.0 microgram/ml) in three of these apparently unrelated penicillin-susceptible clinical isolates of Streptococcus pneumoniae isolated in the United Kingdom and in four Spanish isolates was shown to be solely due to the acquisition of a gene encoding an altered penicillin-binding protein (PBP), PBP2X. PBP2X genes cloned from typical penicillin-resistant isolates of S. pneumoniae that possessed high-level oxacillin resistance were shown to be able to transform susceptible isolates of S. pneumoniae to intermediate oxacillin resistance. In all instances, the intermediately oxacillin-resistant PBP2X transformants retained susceptibility to penicillin (MIC, 0.06 microgram/ml). Under appropriate selective pressure, the acquisition of a low-affinity PBP2X by penicillin-susceptible pneumococci could result in an increasing number of false positives for penicillin resistance among isolates of S. pneumoniae screened with oxacillin. Additionally, these intermediately oxacillin-resistant isolates showed reduced susceptibility to cefotaxime, an agent likely to be prescribed in place of penicillin for the treatment of serious infections due to these apparently penicillin-resistant organisms.

SPROUT: recent developments in the de novo design of molecules

SPROUT is a computer program for constrained structure generation. It is designed to generate molecules for a range of applications in molecular recognition. The program uses a number of approximations that enable a wide variety of diverse structures to be generated. Practical use of the program is demonstrated in two examples. The first demonstrates the ability of the program to generate candidate inhibitors for a receptor site of known 3D structure, specifically the GDP binding site of p21. In the second example, structures are generated to fit a pharmacophore hypothesis that models morphine agonists.

Nosocomial spread of Staphylococcus aureus showing intermediate resistance to methicillin

A nosocomial outbreak of infection and colonization involving six patients and caused by a strain of Staphylococcus aureus showing intermediate resistance to methicillin (MIC = 4-8 mg l-1) is described. The outbreak was associated with skin-carriage of the epidemic strain by a nurse suffering from severe eczema. The reduced susceptibility of the outbreak strain to methicillin was associated with beta-lactamase production. Elimination or inhibition of beta-lactamase activity produced a two-fold decrease in methicillin MIC. There was no evidence for the presence of either penicillin-binding protein 2a or the corresponding mec gene, which mediate resistance in fully methicillin-resistant strains.

Microbial colonization of Blom-Singer prostheses in postlaryngectomy patients

The microbial colonization of 44 Blom-Singer valves obtained from 16 patients over an 11-month period was investigated both by standard microbial culture methods and scanning electron microscopy (SEM). The valves were all removed from the patients after failure to function correctly. The microbiology cultures revealed that Candida species and Staphylococcus aureus were present either individually or in combination on 43 valves. SEM showed yeast hyphae attached to and penetrating the surfaces of the 5 valves examined. Colonies of staphylococci were also seen on 2 of these 5 valves. Unlike similar investigations on other voice prostheses, S aureus colonization was associated with Candida colonization and valve failure.

In-vitro characteristics of glycopeptide resistant strains of Staphylococcus epidermidis isolated from patients on CAPD

The low-level resistance of three clinical isolates of Staphylococcus epidermidis to glycopeptide antibiotics was found to be constitutive, not inducible, and was not increased by passage in the presence of either vancomycin or teicoplanin. There was no loss of resistance on repeated passage in antibiotic-free broth. In contrast, the susceptibility to these antibiotics declined for S. epidermidis NCTC 6513 that been sequentially passaged in either vancomycin or teicoplanin whereas the variants reverted to being susceptible on further passage in antibiotic-free broth. Antibiotic activity was almost completely abolished when cultures of the resistant S. epidermidis strains were exposed overnight to sub-MIC concentrations. No evidence of drug-modifying activity was obtained. Experiments of antibiotic-binding activity indicated that the resistant strains exhibited an increased ability to sequester antibiotics which was particularly rapid in stationary phase cultures when most of the antibiotic activity disappeared from the growth medium within 30 min of exposure to the drugs. Teicoplanin was sequestered more efficiently than vancomycin and some loss of activity was also observed when stationary phase cultures of S. epidermidis NCTC 6513 were exposed to glycopeptides. These results suggest that glycopeptide-resistant isolates of S. epidermidis are able to bind large amounts of these antibiotics, possibly at sites unassociated with the D-alanyl-D-alanine target, and that teicoplanin is bound more avidly than vancomycin.

The emergence of vancomycin resistance in renal dialysis

Intraperitoneal vancomycin is used in the treatment of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). We describe the emergence of low-level glycopeptide-resistance in five Gram-positive species over a one-year period. Isolation of these organisms was associated with vancomycin treatment failure in four patients who had had numerous episodes of peritonitis. Clinicians and microbiologists should be aware that repeated administration of glycopeptides to such patients might lead to the emergence of organisms resistant to these antibiotics.

Prevalence of the type I and type II DHFR genes in trimethoprim-resistant urinary isolates of Escherichia coli from Greece

Trimethoprim resistance in 64 Escherichia coli urinary isolates from five hospitals in Greece was studied. Of the 40 isolates exhibiting transferable high-level resistance (MIC > 1024 mg/L), 21 hybridized with a specific probe for dihydrofolate reductase (DHFR) I, 13 with a probe for DHFR II, and one with a probe for DHFR V. Eleven isolates hybridized with a probe for transposon Tn7. Among the 17 isolates with non-transferable high-level resistance, seven hybridized with the probe for DHFR I, three with the probe for DHFR II, and eight were Tn7-positive. None of the seven isolates with low-level resistance (MIC 4-1024 mg/L) reacted with the probes used. Of the 28 isolates positive for DHFR I, 12 (43%) failed to hybridize with the Tn7 probe. Conversely, three isolates hybridized with the Tn7 probe, but not with the probe for DHFR I. Colony hybridization experiments showed that all but three transconjugants reacted similarly to their respective parent strains. The plasmids coding for trimethoprim-resistant DHFRs were found to differ on the basis of restriction enzyme analysis. These findings suggest that trimethoprim resistance among E. coli urinary isolates in Greece is mediated predominantly by heterogeneous transferable plasmids encoding either DHFR I or DHFR II. The dissociation between DHFR I and Tn7, together with the high incidence of trimethoprim-resistant isolates which did not hybridize with the probes for the common DHFR I or II types, indicates the continued evolution of trimethoprim resistance determinants.

SPROUT: a program for structure generation

SPROUT is a new computer program for constrained structure generation that is designed to generate molecules for a range of applications in molecular recognition. It uses artificial intelligence techniques to moderate the combinatorial explosion that is inherent in structure generation. The program is presented here for the design of enzyme inhibitors. Structure generation is divided into two phases: (i) primary structure generation to produce molecular graphs to fit the steric constraints; and (ii) secondary structure generation which is the process of introducing appropriate functionality to the graphs to produce molecules that satisfy the secondary constraints, e.g., electrostatics and hydrophobicity. Primary structure generation has been tested on two enzyme receptor sites; the p-amidino-phenyl-pyruvate binding site of trypsin and the acetyl pepstatin binding site of HIV-1 protease. The program successfully generates structures that resemble known substrates and, more importantly, the predictive power of the program has been demonstrated by its ability to suggest novel structures.

Multiresistant Klebsiella pneumoniae in a neonatal nursery: the importance of maintenance of infection control policies and procedures in the prevention of outbreaks

During a 3-week period, nine babies in the neonatal unit of a large teaching hospital in Durban were infected or colonized with Klebsiella pneumoniae resistant to a range of antimicrobial agents including amikacin and cefotaxime. Resistance to cefotaxime was reduced by clavulanic acid in vitro suggesting production of extended-spectrum beta-lactamase activity. All the isolates had the same antibiotic resistance profile, belonged to the same serotype (K17), were non-typable with bacteriophages, and had identical plasmid profiles indicating that they belonged to the same strain. During a 1-day microbiological survey of the ward, the outbreak strain was isolated from the nose and hands of a doctor based in the nursery and from the hands of a nurse and the mother of an infected baby. The strain was also isolated from nine of 67 environmental samples. Investigation revealed that infection control practices which had been instituted following a previous outbreak in the nursery with multi-resistant methicillin-resistant Staphylococcus aureus (MRSA) were not being adhered to. The re-introduction and strict enforcement of these procedures under the supervision of an Infection Control Nurse resulted in the abrupt end of the outbreak.

Application of DNA probes for rRNA and vanA genes to investigation of a nosocomial cluster of vancomycin-resistant enterococci

DNA probes specific for genes encoding rRNA and the glycopeptide resistance gene vanA were used to investigate a cluster of vancomycin-resistant (MICs, > 512 mg/liter) Enterococcus faecalis and Enterococcus faecium isolated from separate patients in a renal unit in a London hospital. When digested with BamHI, 12 of 13 vancomycin-resistant E. faecalis isolates exhibited a common restriction fragment length polymorphism pattern of rRNA genes (ribotype). A vanA probe hybridized with chromosomal DNA in these 12 isolates. The other isolate of vancomycin-resistant E. faecalis had a different ribotype and the vanA gene was located on plasmid DNA. These data suggest that cross-infection with a single strain of vancomycin-resistant E. faecalis occurred in most instances. In contrast, 23 vancomycin-resistant E. faecium isolates showed greater heterogeneity, comprising 8 ribotypes, suggesting that multiple strains were present in the unit. Twenty-one of these 23 isolates harbored a 24-MDa plasmid which hybridized with the vanA probe, implying that interstrain dissemination of a vancomycin resistance plasmid may have occurred among E. faecium isolates in the renal unit.

Suction polypectomy forceps

A new instrument is described which relies on suction for the precise removal of polyps and abnormal mucosa during nasal surgery

Pathophysiological concept of Haemophilus ducreyi infection (chancroid)

Our knowledge concerning the pathogenesis of infection due to Haemophilus ducreyi is incomplete. In order to produce disease, H. ducreyi must presumably penetrate the skin of the external genitalia, colonize subcutaneous tissues, then produce tissue damage which results in ulcer formation. Penetration of the normal skin most likely occurs via minor abrasions. Adherence of H. ducreyi to different cell lines in vitro has been described, and might be mediated by adhesions such as pili or haemagglutinins. In addition, binding to extracellular matrix proteins has also been reported. Extracellular tissue-degrading enzymes were absent from broth culture supernatants of H. ducreyi. Such supernatants also failed to produce cytopathic effects with established or primary cell lines. Both live and heat-killed H. ducreyi organisms were able to produce lesions in a rabbit or a mouse model, although ulcer formation was dependent on viable H. ducreyi organisms in a recently introduced temperature-dependent rabbit model. With an excessive supply of iron, a more prolonged localized inflammatory disease effect was observed. Results derived from a subcutaneous chamber model demonstrated considerable changes in the expression of outer membrane proteins combined with antibody modulation during in vivo growth of H. ducreyi. These might be important factors for maintenance of infection in the human host particularly as these changes also occur in humans. Despite an increased knowledge of the pathogenesis of chancroid, important questions such as growth requirements, bubo-formation, role of cell-mediated immunity and ulcer formation are still unanswered. The application of molecular biological techniques in order to study these problems will be helpful.

Multiple components are involved in the efficient joining of double stranded DNA breaks in human cell extracts

We describe a rapid and efficient in vitro system for the rejoining of double stranded breaks in DNA based on extracts of human 293 cells. Using this system as an assay, we have separated the nuclear extract into several components involved in break rejoining. The unfractionated system can convert approx. 100% of the input DNA, linearized with a restriction enzyme, to high molecular weight material at low temperature (17 degrees C), and at the physiological temperature of 37 degrees C we have shown that competing activities in the extract can also act on the DNA template. We present the fractionation of the extract and the partial purification of a novel factor which will stimulate a crude rejoin activity and in addition increases the activity of purified DNA ligase I. We have also partially purified the break joining activity and show that the chromatographic properties do not directly correspond with the three DNA ligases previously described, indicating that the activity observed may not be due to a single enzyme species. By studying the rejoining of double stranded DNA breaks as a biochemical process, we have demonstrated that the efficient joining of such breaks requires factors in addition to DNA ligases.

Binding of Haemophilus ducreyi to extracellular matrix proteins

A collection of Haemophilus ducreyi isolates were screened for the ability to bind to fibrinogen, fibronectin, collagen, gelatin and laminin by a particle agglutination test using latex beads coated with the individual proteins. Thirteen of 21 isolates reacted with all five extracellular matrix proteins. Binding of organisms to protein-coated latex beads was inhibited by pretreatment of the bacteria with detergent, trypsin or boiling. Two isolates did not bind to collagen and gelatin with one of these not reacting with laminin either. Seven strains which failed to react with laminin did not express pili when examined by electron microscopy. This observation suggests a specific interaction with the pili of H. ducreyi.

Lack of immunoglobulin A1 protease production by Haemophilus ducreyi

A collection of 20 strains of Haemophilus ducreyi including freshly isolated, low-passage and multi-passage reference strains was examined for immunoglobulin A1 protease production by SDS-PAGE and immunoblotting. None of the strains demonstrated IgA1 protease activity despite the fact that different culture media were used. By direct immunofluorescence testing, binding of IgA to Haemophilus ducreyi organisms could be demonstrated.

Milk nasendoscopy in the assessment of dysphagia

The bedside assessment of dysphagia may be difficult, due to the inability to witness the act of swallowing directly. The milk test described in this paper gives a good assessment of swallowing, is cheap and easily portable and allows an instant decision to be made without recourse to special investigations.

Outbreak of infection in two UK hospitals caused by a strain of Klebsiella pneumoniae resistant to cefotaxime and ceftazidime

During an 8-month period, Klebsiella pneumoniae resistant to cefotaxime and ceftazidime were isolated from 18 elderly patients in two closely-situated UK hospitals. Amongst these 18 patients, the organisms were isolated from urine samples of 17, from blood cultures of two and from a wound swab of one. The infected patients were located in nine different wards and several of the patients had been transferred between wards, within and between the two hospitals. All the bacterial isolates belonged to serotype K62, were non-typable or reacted only weakly with bacteriophage, showed similar plasmid profiles and were resistant to tetracycline and trimethoprim, thus indicating they were the same strain. Resistance to cefotaxime and ceftazidime was inhibited by clavulanic acid suggesting the involvement of extended-spectrum beta-lactamase (ESBL) enzyme activity. This was confirmed by analytical isoelectric focusing, which showed that isolates each produced two beta-lactamases with isoelectric points of 7.0(SHV-3) and 7.6 (SHV-1/2) respectively.

Prevalence of a plasmid-mediated type II dihydrofolate reductase gene among trimethoprim-resistant urinary pathogens in Greek hospitals

The genetic basis of trimethoprim resistance was examined in 24 Klebsiella pneumoniae, 27 Enterobacter cloacae, five Enterobacter aerogenes and nine Serratia marcescens urinary isolates from five hospitals in Greece. Analysis of the 65 isolates by serotyping and phage-typing identified 53 distinct strains. Thirty-eight isolates (15 K. pneumoniae, 19 E. cloacae, two E. aerogenes and two S. marcescens) hybridized with a probe specific for a gene encoding type II dihydrofolate reductase (DHFR). Three of the K. pneumoniae and four of the E. cloacae isolates which reacted with this probe also hybridized with probes specific for type I DHFR and transposon Tn7. Two E. cloacae isolates hybridized only with the probe for type I DHFR, while a further three isolates hybridized only with the type I DHFR and Tn7 probes. None of the isolates hybridized with a probe for type V DHFR. The plasmids in transconjugants derived from 40 isolates were analysed by digestion with restriction enzymes and Southern blotting. Eighteen (45%) of the donors (12 K. pneumoniae and 6 E. cloacae) produced transconjugants containing plasmids of about 95 kb in size, while transconjugants from the other donors had plasmids in the range 100-185 kb. Of the 18 transconjugants containing a 95 kb plasmid, 15 had similar restriction endonuclease digest patterns, although they varied in terms of the range of antimicrobial resistances which they encoded. When EcoRI digests of these 15 plasmids were hybridized with the type II DHFR probe, a 23 kb common band reacted with the probe.(ABSTRACT TRUNCATED AT 250 WORDS)

Absence of extracellular enzyme activity and cytotoxicity in cell-free culture filtrates of Haemophilus ducreyi

Ten isolates of Haemophilus ducreyi, including seven clinical isolates and three laboratory reference strains, were assessed for their ability to produce extracellular enzymes which might contribute to their pathogenicity. Protease, elastase, lecithinase, lipase or collagenase enzyme activity were not detected in culture filtrates from any of the isolates tested using either plate or spectrophotometrical assays. Furthermore, cell-free culture filtrates did not exhibit cytotoxic activity in vitro when tested using either an established tissue culture cell line (Vero) or a primary cell culture of human keratinocytes. These results suggest that extracellular products do not play a role in host invasion or production of tissue damage by H. ducreyi.

Distribution and transferability of plasmids encoding trimethoprim resistance in urinary pathogens from Greece

Of 505 strains of Enterobacteriaceae responsible for significant bacteriuria and isolated from hospital patients in two Greek cities in 1989, 151 strains (30%) were resistant to trimethoprim (MIC greater than or equal to 4 mg/L) and 220 (44%) were resistant to sulphamethoxazole (MIC greater than or equal to 64 mg/L); 127 (84%) of the trimethoprim-resistant strains exhibited high-level resistance (MIC greater than 1024 mg/L) and 121 (80%) were additionally resistant to four or more other antibiotics. Plasmids were detected in 141 (93%) of the trimethoprim-resistant strains. Trimethoprim resistance was encoded on self-transmissible plasmids in 79 (52%) of the resistant strains, and in a further seven strains (5%), plasmids coding for trimethoprim resistance could be mobilised by X+ factor. Co-transfer of various other antimicrobial resistances with trimethoprim resistance was observed, tetracycline resistance being the most common. The low degree of linkage observed between trimethoprim resistance and resistance to streptomycin and spectinomycin suggests that Tn7 is relatively uncommon in Greece. Classification of trimethoprim-resistance plasmids on the basis of their antimicrobial-resistance patterns and molecular mass revealed 39 different profiles. Overall, these findings differ from those from other European countries where the prevalence of transferable high-level trimethoprim resistance is low and where chromosomal Tn7-encoded trimethoprim resistance is common.

Patterns of epithelial migration in the unaffected ear in patients with a history of unilateral cholesteatoma

Epithelial migration in a centrifugal manner is an established phenomenon in the normal human tympanic membrane. This pattern of migration is symmetrical in both ears of any one individual. We present a prospective study on the pattern of tympanic ink dot migration on the normal drum, in patients with a history of cholesteatoma in one ear. It was demonstrated that patients who develop cholesteatoma have a normal migratory pattern and rate in the unaffected ear. The conclusion from this study is that defective migration is not the initiating factor in the development of acquired cholesteatoma.

Videofluoroscopy in motor neurone disease prior to cricopharyngeal myotomy

Cricopharyngeal myotomy is a recognised treatment for the dysphagia in motor neurone disease, although the results are sometimes disappointing. In this study, 27 patients with motor neurone disease causing significant dysphagia have been investigated by the technique of videofluoroscopy, in order to determine the nature of their swallowing disability; those patients found suitable have been offered cricopharyngeal myotomy. Of the 27 patients, only seven were found to have cricopharyngeal dysfunction as the predominant disability and, of these, six underwent myotomy, resulting in relief of dysphagia in five, three of whom returned to a near normal diet. Previous studies showed poor overall benefit from cricopharyngeal myotomy. Videofluoroscopy allows accurate patient selection, and a much improved outcome in the selected group.

Penicillin-resistant viridans streptococci have obtained altered penicillin-binding protein genes from penicillin-resistant strains of Streptococcus pneumoniae

Penicillin-resistant strains of Streptococcus pneumoniae possess altered forms of penicillin-binding proteins (PBPs) with decreased affinity for penicillin. The PBP2B genes of these strains have a mosaic structure, consisting of regions that are very similar to those in penicillin-sensitive strains, alternating with regions that are highly diverged. Penicillin-resistant strains of viridans groups streptococci (e.g., S. sanguis and S. oralis) that produce altered PBPs have also been reported. The PBP2B genes of two penicillin-resistant clinical isolates of S. sanguis were identical in sequence to the mosaic class B PBP2B genes found in penicillin-resistant serotype 23 strains of S. pneumoniae. Emergence of penicillin resistance appears to have occurred by the horizontal transfer of an altered PBP2B gene from penicillin-resistant S. pneumoniae into S. sanguis. The PBP2B genes of three penicillin-resistant S. oralis strains were similar to the mosaic class B PBP2B gene of penicillin-resistant strains of S. pneumoniae but possessed an additional block of diverged sequence. Penicillin resistance in S. oralis has also probably arisen by horizontal transfer of this variant form of the class B mosaic PBP2B gene from a penicillin-resistant strain of S. pneumoniae.

The evolutionary watershed of susceptibility to gonococcal infection

Gonococci do not cause genital infection in any convenient experimental animal, but all too easily cause genital infection in humans. To determine the 'evolutionary watershed' of gonococcal infections (the point on the evolutionary tree at which susceptibility to gonococcal infection begins) we extended previous studies of the interaction of gonococci with animal oviduct mucosa to include chimpanzees and baboons. Gonococci attached to, damaged, and invaded the oviduct (fallopian tube) mucosa of chimpanzees (which are apes) but not the oviduct mucosa of baboons (which are monkeys). Thus, the pattern of gonococcal infection in chimpanzees was identical to that in humans, whereas the pattern in baboons was like that in other animals. These studies indicate that the point in evolution at which susceptibility to gonococcal infection commences is between baboons and chimpanzees (or between monkeys and apes). Susceptibility to gonococcal disease appears to require the presence on genital epithelial cells of receptors for gonococcal ligands such as pili, receptors for gonococcal lipopolysaccharide, or both. The physiological role of these receptors may be to interact with more useful, as yet unidentified molecules.

Resistance to vancomycin and teicoplanin: an emerging clinical problem

Vancomycin and teicoplanin are glycopeptides active against a wide range of gram-positive bacteria. For 30 years following the discovery of vancomycin in 1956, vancomycin resistance was not detected among normally susceptible bacteria recovered from human specimens. Since 1986, however, bacteria resistant to vancomycin or teicoplanin or both have been described. Strains of the genera Leuconostoc, Lactobacillus, Pediococcus, and Erysipelothrix seem inherently resistant to glycopeptides. Species and strains of enterococci and coagulase-negative staphylococci appear to have acquired or developed resistance. There are at least two categories of glycopeptide resistance among enterococci, characterized by either high-level resistance to vancomycin (MIC, greater than or equal to 64 mg/liter) and teicoplanin (MIC, greater than or equal to 8 mg/liter) or lower-level vancomycin resistance (MIC, 32 to 64 mg/liter) and teicoplanin susceptibility (MIC, less than or equal to 1 mg/liter). The two categories appear to have similar resistance mechanisms, although genetic and biochemical studies indicate that they have arisen independently. Among coagulase-negative staphylococci, strains for which vancomycin MICs are up to 20 mg/liter or teicoplanin MICs are 16 to 32 mg/liter have been reported, but cross-resistance between these glycopeptides varies. The selective advantage accorded to glycopeptide-resistant bacteria and the observation that high-level resistance in enterococci is transferable suggest that such resistance may be expected to increase in incidence. Clinicians and microbiologists need to be aware of this emerging problem.

The importance of early fixation in preservation of human cochlear and vestibular sensory hair bundles

Human labyrinths were fixed with glutaraldehyde as soon as possible and certainly within 15 min of clinically confirmed death. By following this protocol, we have obtained excellent preservation of human material comparable to the best that we were able to obtain with animal tissues. Structural features that are indicative of good fixation in animal hair bundles, namely well-defined lateral cross-links, upward pointing tip links and the 'granular' appearance of the surface membrane of stereocilia are confirmed for human hair cells. Our results show that excellent preservation of human hair bundles is critically dependent upon early fixation.

The mechanism of healing of tympanic membrane perforations. A two-dimensional histological study in guinea pigs

The healing of small perforations, made in 60 tympanic membranes (30 guinea pigs) with either a thermal myringotome or a needle was observed over a 10-day period using an operating microscope. Thirty-six of these were sectioned either parallel with the handle of the malleus, or at right angles to it, and the closing perforations studied by light microscopy. The epidermis closed the perforations first, in the direction of surface migration. This process began within 48 hours and was complete within 9 days. A fibrous reaction occurred, starting at 3 days, and this was seen on the side of the perforation adjacent to the malleus or bony tympanic annulus. There was no response visible in the middle ear mucosa. The conclusion of this study is that the epidermis is the first layer to close a perforation because of its migratory function, and the direction of closure is the direction of migration. Healing of the fibrous layer occurs secondarily, and the site of the response in this layer is related to the vascular distribution in the tympanic membrane.

Effect of iron limitation on protein composition and ultrastructure of Haemophilus ducreyi

Protein profiles of whole cells of Haemophilus ducreyi grown in the presence or absence of the iron chelator desferal, were compared by polyacrylamide gel electrophoresis. Each of four strains produced novel proteins in the range 43-160 kDa when cultured under conditions of reduced iron availability. At some sub-inhibitory concentrations, desferal produced enhanced growth, possibly due to it functioning as an exogenous siderophore. Organisms grown under conditions of reduced iron availability ultrastructurally showed also large periplasmic spaces between cytoplasm and outer membrane.

Fine needle aspiration cytology of salivary gland lesions

Eighty-eight fine needle aspirates from 79 salivary gland lesions in 77 patients were examined. The overall diagnostic sensitivity was 84% and the specificity 98.41%. When the 14 unsatisfactory specimens were excluded the sensitivity rose to 95.45%. Correct identification of the disease process was possible in nearly 80% of cases with a final benign diagnosis. The histological tumour type was correctly predicted in 75% of the malignancies. In the others the cytological diagnosis was anaplastic malignant neoplasm.

A laboratory-confirmed outbreak of rifampicin-methicillin resistant Staphylococcus aureus (RMRSA) in a newborn nursery

The routine laboratory monitoring of methicillin-resistant strains of Staphylococcus aureus (MRSA) at a large teaching hospital led to the detection of a new, multiply-resistant strain of MRSA, which was resistant not only to penicillin, oxacillin, methicillin, cephamandole, erythromycin, tetracycline, kanamycin and gentamicin but also to rifampicin and sulphamethoxazole-trimethoprim. The rifampicin-methicillin resistant strain of S. aureus (RMRSA) was first detected in blood cultures of babies from the newborn nursery. A bacteriological investigation of the nursery revealed the source to be a paediatric medical officer who was colonised with the resistant strain, and who at the time was receiving rifampicin for pulmonary tuberculosis. The rifampicin resistance was presumably acquired during rifampicin therapy. The outbreak in the nursery was brought to an abrupt end by treatment of the colonised medical officer with mupirocin, applied nasally twice a day for a week, and by the introduction of standard infection-control measures. Reference laboratory assistance was needed to confirm the initial assumption that the outbreak was caused by a single strain.

Nontraditional opportunities for dairy practitioners

Many opportunities exist for dairy practitioners in addition to the conventional fields of disease and sterility treatment. Consultation with dairymen and agribusinesses, professional speaking and writing, service as expert witnesses, and product testing and endorsement are available options.

Regulation of growth hormone secretion and messenger ribonucleic acid accumulation in human somatotropinoma cells in vitro

GH secretion and mRNA levels were measured in cultured cells obtained from six human pituitary somatotroph tumors to investigate their hormonal and intracellular regulation. The responses were variable between tumors, but, in general, mRNA levels were less responsive than GH release to in vitro manipulation. GH-releasing factor [GRF-(1-29) amide; 10 nM] increased GH release and mRNA levels in three of four tumors tested to 30-97% above control values, but the fourth tumor was unresponsive. Somatostatin (1 microM) inhibited GH release significantly in four of the six cases, to 35-79% of control levels, but had no inhibitory effect on GH mRNA accumulation, in contrast to earlier studies on rat pituitary tissue. Bromocriptine (100 nM) likewise inhibited GH release (50-75% of control), but not GH mRNA levels, in the four tumors tested. Forskolin (10 microM; used to activate adenylate cyclase) stimulated GH release and mRNA levels in the two cases that responded most clearly to GRF, but had no significant effect in the other tumors; however, the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (100 nM) had no consistent effect on mRNA levels despite stimulating secretion in four of six cases. Thus, there was considerable variation in responses among the tumors tested; however, the responsiveness to GRF was approximately paralleled by that to forskolin, consistent with the suggestion that adenylate cyclase activity and responsiveness are variable among these tumors. Furthermore, the divergent effects of somatostatin on GH release and mRNA suggest uncoupling between its receptor and transcriptional regulatory mechanisms.