The catalytic mechanism of cyclic GMP-AMP synthase (cGAS) and implications for innate immunity and inhibition

Cyclic GMP-AMP synthase (cGAS) is activated by ds-DNA binding to produce the secondary messenger 2',3'-cGAMP. cGAS is an important control point in the innate immune response; dysregulation of the cGAS pathway is linked to autoimmune diseases while targeted stimulation may be of benefit in immunoncology. We report here the structure of cGAS with dinucleotides and small molecule inhibitors, and kinetic studies of the cGAS mechanism. Our structural work supports the understanding of how ds-DNA activates cGAS, suggesting a site for small molecule binders that may cause cGAS activation at physiological ATP concentrations, and an apparent hotspot for inhibitor binding. Mechanistic studies of cGAS provide the first kinetic constants for 2',3'-cGAMP formation, and interestingly, describe a catalytic mechanism where 2',3'-cGAMP may be a minor product of cGAS compared with linear nucleotides.

Discovery of PF-06928215 as a high affinity inhibitor of cGAS enabled by a novel fluorescence polarization assay

Cyclic GMP-AMP synthase (cGAS) initiates the innate immune system in response to cytosolic dsDNA. After binding and activation from dsDNA, cGAS uses ATP and GTP to synthesize 2', 3' -cGAMP (cGAMP), a cyclic dinucleotide second messenger with mixed 2'-5' and 3'-5' phosphodiester bonds. Inappropriate stimulation of cGAS has been implicated in autoimmune disease such as systemic lupus erythematosus, thus inhibition of cGAS may be of therapeutic benefit in some diseases; however, the size and polarity of the cGAS active site makes it a challenging target for the development of conventional substrate-competitive inhibitors. We report here the development of a high affinity (KD = 200 nM) inhibitor from a low affinity fragment hit with supporting biochemical and structural data showing these molecules bind to the cGAS active site. We also report a new high throughput cGAS fluorescence polarization (FP)-based assay to enable the rapid identification and optimization of cGAS inhibitors. This FP assay uses Cy5-labelled cGAMP in combination with a novel high affinity monoclonal antibody that specifically recognizes cGAMP with no cross reactivity to cAMP, cGMP, ATP, or GTP. Given its role in the innate immune response, cGAS is a promising therapeutic target for autoinflammatory disease. Our results demonstrate its druggability, provide a high affinity tool compound, and establish a high throughput assay for the identification of next generation cGAS inhibitors.

Inhibiting complex IL-17A and IL-17RA interactions with a linear peptide

IL-17A is a pro-inflammatory cytokine that has been implicated in autoimmune and inflammatory diseases. Monoclonal antibodies inhibiting IL-17A signaling have demonstrated remarkable efficacy, but an oral therapy is still lacking. A high affinity IL-17A peptide antagonist (HAP) of 15 residues was identified through phage-display screening followed by saturation mutagenesis optimization and amino acid substitutions. HAP binds specifically to IL-17A and inhibits the interaction of the cytokine with its receptor, IL-17RA. Tested in primary human cells, HAP blocked the production of multiple inflammatory cytokines. Crystal structure studies revealed that two HAP molecules bind to one IL-17A dimer symmetrically. The N-terminal portions of HAP form a β-strand that inserts between two IL-17A monomers while the C-terminal section forms an α helix that directly blocks IL-17RA from binding to the same region of IL-17A. This mode of inhibition suggests opportunities for developing peptide antagonists against this challenging target.

Binding screen for cystic fibrosis transmembrane conductance regulator correctors finds new chemical matter and yields insights into cystic fibrosis therapeutic strategy

The most common mutation in cystic fibrosis (CF) patients is deletion of F508 (ΔF508) in the first nucleotide binding domain (NBD1) of the CF transmembrane conductance regulator (CFTR). ΔF508 causes a decrease in the trafficking of CFTR to the cell surface and reduces the thermal stability of isolated NBD1; it is well established that both of these effects can be rescued by additional revertant mutations in NBD1. The current paradigm in CF small molecule drug discovery is that, like revertant mutations, a path may exist to ΔF508 CFTR correction through a small molecule chaperone binding to NBD1. We, therefore, set out to find small molecule binders of NBD1 and test whether it is possible to develop these molecules into potent binders that increase CFTR trafficking in CF-patient-derived human bronchial epithelial cells. Several fragments were identified that bind NBD1 at either the CFFT-001 site or the BIA site. However, repeated attempts to improve the affinity of these fragments resulted in only modest gains. Although these results cannot prove that there is no possibility of finding a high-affinity small molecule binder of NBD1, they are discouraging and lead us to hypothesize that the nature of these two binding sites, and isolated NBD1 itself, may not contain the features needed to build high-affinity interactions. Future work in this area may, therefore, require constructs including other domains of CFTR in addition to NBD1, if high-affinity small molecule binding is to be achieved.

Growth characteristics underlying the lack of a chin in pigs: a histomorphometric study

OBJECTIVES

Despite similar mandibular growth to that of humans, pigs lack a chin projection as shown in most humans. To understand whether this divergence is contributed to differences in local symphyseal growth, this project characterized bone modeling activities at the symphyseal surfaces of juvenile pigs.

MATERIAL AND METHODS

Symphyseal specimens from two age groups (4- and 6-month-old, n = 10) were processed into histological sections with and without decalcification, which were assessed for surface mineral apposition and bone resorption, respectively. In a blinded fashion, measurements of four parameters (MAR: mineral apposition rate, MAZ: mineral apposition zone, ES/BS: eroded surface and OC.N/BS: osteoclast number) were obtained and tested by a multivariate two-way mixed-model analyses of variance (manova) for the differences between symphyseal regions and ages.

RESULTS

Qualitatively, pig symphyseal labial and lingual surfaces were horizontally oriented and characterized by mineral apposition and bone resorption, respectively. Quantitatively, labial mineral apposition tended to be greater rostrally than caudally at 4 months, which became greater caudally than rostrally at 6 months (region/age interactions: p = 0.127 for MAR, p = 0.012 for MAZ). Lingual bone resorption tended to be greater caudally than rostrally, but only ES/BS measurements were significant (p = 0.039) regardless of age, while OC.N/BS measurements varied with ages and regions (age/region interaction, p = 0.087).

CONCLUSIONS

Insufficient differential in symphyseal surface modeling between the labial-caudal and labial-rostral regions contributes to the lack of chin projection in the pig.

Discovery of cytotoxic dolastatin 10 analogues with N-terminal modifications

Auristatins, synthetic analogues of the antineoplastic natural product Dolastatin 10, are ultrapotent cytotoxic microtubule inhibitors that are clinically used as payloads in antibody-drug conjugates (ADCs). The design and synthesis of several new auristatin analogues with N-terminal modifications that include amino acids with α,α-disubstituted carbon atoms are described, including the discovery of our lead auristatin, PF-06380101. This modification of the peptide structure is unprecedented and led to analogues with excellent potencies in tumor cell proliferation assays and differential ADME properties when compared to other synthetic auristatin analogues that are used in the preparation of ADCs. In addition, auristatin cocrystal structures with tubulin are being presented that allow for the detailed examination of their binding modes. A surprising finding is that all analyzed analogues have a cis-configuration at the Val-Dil amide bond in their functionally relevant tubulin bound state, whereas in solution this bond is exclusively in the trans-configuration. This remarkable observation shines light onto the preferred binding mode of auristatins and serves as a valuable tool for structure-based drug design.

Characterizing cognitive deficits and dementia in an aging urban population in India

Rapid rise in the population of older adults in India will lead to the need for increased health care services related to diagnosis, management, and long-term care for those with dementia and cognitive impairment. A direct approach for service provision through memory clinics can be an effective, successful, and sustaining means of delivering specialized health care services. We have established a memory clinic in Mumbai, India by employing the diverse clinical skills available in Indian academic institutions, diagnostic and research expertise of clinicians and psychologists, and the support of the U.S. National Institutes of Health. Our project involved recruitment of patients, clinical and neuropsychological assessment, and standardized diagnostic procedures, demonstrating the feasibility of using research methods to develop a memory clinic. In this paper, we describe the development of a community-based memory clinic in urban India, including linguistic and cultural factors and present detailed results, including diagnostic characterization, on 194 subjects with various stages of cognitive deficits. Our findings support the feasibility of developing a memory clinic in a public hospital and successful use of research diagnostic criteria to categorize cognitive deficits observed in this population, which may be used to inform the development of other such clinics.

Epigenetic regulation and downstream targets of the Rhox5 homeobox gene

The discovery of the Rhox homeobox gene cluster on the X chromosome opens up new vistas in the regulation of reproductive processes in mammals. In mice, this cluster comprises more than 30 genes that are selectively expressed in reproductive tissues. A subset of Rhox genes are androgen and AR regulated in postnatal and adult Sertoli cells, making them candidates to mediate androgen-dependent steps during spermatogenesis. The best characterized of these androgen/AR-regulated genes is Rhox5 (Pem), the founding member of the Rhox gene cluster. Targeted deletion of Rhox5 in mice causes male subfertility marked by increased germ-cell apoptosis and decreased sperm count and motility. Microarray analyses identified a wide variety of genes regulated by Rhox5 in Sertoli cells. One of them is the tumour suppressor UNC5C, a pro-apoptotic molecule previously only known to be involved in brain development. Targeted deletion of Unc5c causes decreased germ-cell apoptosis in postnatal and adult testes, indicating that it also has a role in spermatogenesis and supporting a model in which Rhox5 promotes germ-cell survival by downregulating Unc5c. Rhox5 has two independently regulated promoters that have distinct expression patterns. The unique tissue-specific and developmentally regulated transcription pattern of these two promoters appear to be controlled by DNA methylation. Both promoters are methylated in tissues in which they are not expressed, suggesting that DNA methylation serves to repress Rhox5 expression in inappropriate cell types and tissues. In summary, the Rhox gene cluster is an epigenetically regulated set of genes encoding a large number of transcription factors that are strong candidates to regulate gametogenesis and other aspects of reproduction.

Characterization of the antiapoptotic (p35) gene homologue of Spodoptera litura nucleopolyhedrosis virus (SlNPV)

Antiapoptotic genes of baculoviruses have been shown to prevent virus induced apoptosis in insect cells. Dot blot and Southern hybridizations of EcoRI genomic library and genomic digests of Spodoptera litura nucleopolyhedrosis virus (SlNPV) respectively give strong hybridization signals with antiapoptotic DNA (p35 gene) probe of the prototype Autographa californica nucleopolyhedrosis virus (AcNPV). Both the hybridizations indicate the presence of a homologous gene in the 1.8 kb EcoRI-Y fragment of SlNPV. The sequence of 1.244 kb region of this fragment encompasses an open reading frame coding for a polypeptide of 296 amino acids under sequential early (TATA) and late (TAAG) promoter motifs like that in other baculovirus p35 genes. The putative SlNPV p35 ORF expresses abundantly as a 35 kDa protein in Spodopterafrugiperda (Sf9) cells when allowed to express under the polyhedrin promoter of AcNPV.

Identification of a cDNA clone encoding for a galactose-binding lectin from peanut (Arachis hypogaea) seedling roots

A cDNA clone obtained from developing peanut (Arachis hypogaea) seedling roots, when expressed in Escherichia coli and insect cells (Sf9) gave a 29 kDa subunit protein. The native recombinant protein agglutinates neuraminidase treated human erythrocytes and the agglutination is inhibited by galactose. Nucleotide sequence and predicted amino acid sequence analyses indicate that it is different from peanut seed (PNA and SGL) and nodule (NGLa and NGLb) galactose-binding lectins.

Sequences of Citrus tristeza virus separated in time and space are essentially identical

The first Citrus tristeza virus (CTV) genomes completely sequenced (19.3-kb positive-sense RNA), from four biologically distinct isolates, are unexpectedly divergent in nucleotide sequence (up to 60% divergence). Understanding of whether these large sequence differences resulted from recent evolution is important for the design of disease management strategies, particularly the use of genetically engineered mild (essentially symptomless)-strain cross protection and RNA-mediated transgenic resistance. The complete sequence of a mild isolate (T30) which has been endemic in Florida for about a century was found to be nearly identical to the genomic sequence of a mild isolate (T385) from Spain. Moreover, samples of sequences of other isolates from distinct geographic locations, maintained in different citrus hosts and also separated in time (B252 from Taiwan, B272 from Colombia, and B354 from California), were nearly identical to the T30 sequence. The sequence differences between these isolates were within or near the range of variability of the T30 population. A possible explanation for these results is that the parents of isolates T30, T385, B252, B272, and B354 have a common origin, probably Asia, and have changed little since they were dispersed throughout the world by the movement of citrus. Considering that the nucleotide divergence among the other known CTV genomes is much greater than those expected for strains of the same virus, the remarkable similarity of these five isolates indicates a high degree of evolutionary stasis in some CTV populations.

A point mutation at the Miniature1 seed locus reduces levels of the encoded protein, but not its mRNA, in maize

We report here on the molecular nature of an EMS-induced mutant, mn1-89, a leaky semidominant allele of the Miniature1 (Mn1) seed locus that encodes a seed-specific cell wall invertase, INCW2. The mn1-89 locus specifies normal levels of the Incw2 transcript but extremely low levels (about 6% of normal) of the protein and enzyme activity are expressed. Sequence analysis of Incw2 clones derived from the parental Mn1 and the mutant genotypes shows a C to T transition in the mn1-89 allele, leading to a single amino acid alteration (proline to leucine) near the C-terminus of the mutant INCW2 protein. Although this change is not in the catalytic domain, putative N-glycosylation sites, or the beta-fructosidase motif, it does lie in a motif that is well conserved among all plant invertases and related fructosyltransferases. On the basis of these genetic in planta data, we believe we have identified a proline residue in a hitherto unknown GPFG motif as critical for the stability of such proteins. The single base change (C to T) also leads to the elimination of a BglI restriction site in the mutant allele. Indeed, BglI restriction digests of genomic DNAs from mn1-89 and Mn1 genotypes show one and two fragments, respectively. Sequence analysis of RT-PCR-derived endosperm Incw clones from mn1-1 (the reference allele) seeds predict five amino acid substitutions relative to Mn1. Whether or not these sequences are encoded by the mn1-1 locus or another non-allelic Incw gene in the maize genome remains to be elucidated.

Dentofacial morphology and upper respiratory function in 8-10-year-old children

OBJECTIVES

The aim of this preliminary study was to assess the nature of associations between selected dentofacial morphological variables and respiratory mode as measured by percent nasality (%N) as part of an ongoing longitudinal study.

DESIGN

Cross-sectional cohort study.

SETTING AND SAMPLE POPULATION

The Pediatric Clinical Study Center, Children's Hospital, Columbus, OH. Ninety-eight normal children were tested.

EXPERIMENTAL VARIABLE

Normal variation in %N.

OUTCOME MEASURE

Selected dentofacial morphological variables including total and lower anterior face heights, face width, and palatal arch width and %N were estimated.

RESULTS

Small associations between morphologic features and respiratory mode were found, but none were statistically significant.

CONCLUSION

No evidence exists for the classic association between 'mouth breathing' and the stereotype of the 'adenoid facies'.

Cephalometric A point changes during and after maxillary protraction and expansion

The purpose of this study was to analyze the treatment and posttreatment maxillary changes achieved with maxillary protraction therapy. The cephalometric records of 25 consecutively treated Chinese children with Class III malocclusions (mean age 8.4 years) were analyzed for cephalometric A point changes, which were then compared with an untreated, age and sex matched Class III control sample. A cephalometric maxillary superimposition technique was used to differentiate between the skeletal and the local contributions to the total A point change. Results showed that 6 months of maxillary protraction therapy produced a mean A point advancement of 2.4 mm compared with 0.2 mm in the control group. Of this advancement, 75% was found to be due to skeletal maxillary advancement and 25% was attributed to local remodeling. Significantly less downward movement of A point was found with treatment compared with the controls, which could be related to the direction of force application. No significant differences were found in the horizontal and the vertical movements of A point between the treatment and the control groups during the 12-month posttreatment period, indicating stability of early maxillary protraction in patients with Class III malocclusions.

Three-year experience with neonatal ventilation from a tertiary care hospital in Delhi

Ninety neonates were ventilated over a period of 33 months of whom 50 (55.5%) survived. Fifty seven babies received IPPV while 33 CPAP. IPPV mode was being used more frequently recently and survival rates have steadily improved over past 3 years. Survival was cent per cent in babies above 1.5 kg on CPAP mode while 16/26 (57.7%) survived on IPPV mode. Of 22 extremely VLBW (< 1 kg) babies, six survived. HMD was the commonest indication of ventilation (50%), of which 53% (24/45) survived. The other important indications of ventilation were apnea in 13 and transient tachypnea in 11 babies. All babies requiring ventilation for transient tachypnea survived. Nosocomial infections were common in association with ventilation 34/90 (37.7%), out of which in 14 was responsible for about a third of deaths. Pulmonary air leaks developed in 12 babies of which 6 died. Two babies developed BPD and one ROP. Neonatal ventilation should be ventured in centres where basic facilities for level II care already exist. It may not be cost effective to ventilate extremely low birth weight neonates.

Course of bipolar disorder in eastern India

The life course of affective episodes was determined for 95 consecutively admitted patients from eastern India fulfilling RDC criteria for definite mania during the current episode, using SADS-L interviews. There was a significantly greater frequency of manic compared to depressive relapses. Presentation as recurrent mania was very common. The total numbers of affective and manic episodes were significantly higher among those with recurrent mania and in cases where the first illness episode was manic.

Horizontal transmission of Campylobacter jejuni amongst broiler chicks: experimental studies

Horizontal transmission of Campylobacter jejuni was investigated in campylobacter-free broiler chicks. One hundred and twenty chicks housed individually, were provided with water containing 10(2)-10(9) c.f.u./ml C. jejuni. Colonization was rapid [47 of 73 (64%) positive cloacal cultures within 3 days and 65 of 73 (89%) within 7 days], dependent on C. jejuni strain and inoculum size but independent of chick age. Groups of 5-24 chicks in isolators were exposed to C. jejuni-contaminated water or colonized seeder chicks. Transmission occurred in 2-7 days concurrent with a gradual increase of C. jejuni in litter, water and feed. Environmental samples were culture-negative within 3 days following removal of colonized chicks. Treatment of 1-day-old chicks with adult caecal microbiota did not affect colonization. Treated and control chicks were all C. jejuni-positive within 3 days of seeder challenge.

Experimental colonization of broiler chicks with Campylobacter jejuni

Minimal colonization inocula for two broiler strains of Campylobacter jejuni were determined in broiler chicks aged 2-3 days and 2 weeks. Individually housed chicks were exposed to a single oral or cloacal challenge. Diarrhoeal symptoms were absent in all 380 chicks included in the study. Chick susceptibility to the two C. jejuni strains varied. Colonization was effected by less than 10(2)-10(4) colony forming units (c.f.u.) via cloacal challenge and 10(4)-10(6) c.f.u. via the oral route. Colonization inocula for 2- to 3-day and 2-week-old chicks were similar. Treatment of 1-day-old chicks with fresh adult caecal flora or an anaerobic broth culture of adult caecal flora did not inhibit colonization after challenge with low-dose C. jejuni. Susceptible chicks were colonized rapidly. C. jejuni was detected in 167 of 189 (88%) colonized chicks within 3 days of challenge and persisted during the 2-week monitoring period. Our data suggest that colonization of broiler chicks with C. jejuni is effected more easily by the cloacal than the oral route and is independent of age.

Campylobacter jejuni in broilers: the role of vertical transmission

The role of broiler eggs in the transmission of Campylobacter jejuni to broiler grow-out flocks was investigated. Six breeder flocks supplying broiler eggs to hatcheries were examined for cloacal carriage of C. jejuni. Of 240 birds tested, 178 (74%) were C. jejuni-positive. Eggs from these birds examined for C. jejuni penetration of the egg shell indicated that 185 of 187 were campylobacter-free. Eggs from breeder flocks of unknown C. jejuni status were also examined for C. jejuni shell penetration. C. jejuni was not isolated from 142 eggs examined. A further 193 hatchery eggs incubated and hatched in the laboratory were campylobacter-free. Six farms containing the progeny of C. jejuni-positive breeder flocks were monitored. Eight hundred and forty birds from 14 flocks in these grow-out farms were campylobacter-free during their 6-week grow-out period. Experimental egg-penetration studies indicated that C. jejuni transmission via the egg is not easily effected. Of 257 eggs surface-challenged with C. jejuni, 162 hatched; all were campylobacter-free. Of 167 eggs injected with C. jejuni, 12 hatched; 2 of these were colonized with C. jejuni. Our data do not support a role for vertical transmission of C. jejuni in commercial broiler production.

In vitro antibacterial activity of enoxacin (CI-919)

Antibacterial activity of enoxacin was evaluated against more than 3,700 clinical isolates using the agar-dilution method and an inoculum of 10(4)-10(5) cells per site. For comparison other antibiotics appropriate for each species were also included. For most enterobacteria and for Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa, the MIC90 of enoxacin was below 2 mg/l. Serratia marcescens was more resistant; the MIC90 being 4 mg/ml. Enoxacin also showed high activity against Campylobacter jejuni and Neisseria gonorrhoeae. Streptococci were comparatively resistant, 32 mg/l to 64 mg/l of the compound being required to inhibit 90% of strains.

In-vitro effects of vancomycin, rifampicin, and fusidic acid, alone and in combination, against methicillin-resistant Staphylococcus aureus

Minimal inhibitory and minimal bactericidal concentrations were determined for eighteen methicillin-resistant Staphylococcus aureus isolates, the majority also resistant to gentamicin, obtained from the blood of bacteraemic patients. Fifty per cent of organisms had a greater than four-fold difference in M.I.C. and M.B.C. for vancomycin, 83% for rifampicin, and 89% for fusidic acid. In-vitro effects of two-drug combinations of vancomycin, rifampicin, and fusidic acid demonstrated neither synergy nor antagonism when measured by a checkerboard dilution technique. The relevance of these findings to choice of therapy of serious infection due to methicillin-gentamicin resistant Staph. aureus is yet to be determined.

Susceptibility of Campylobacter jejuni to twenty-three antimicrobial agents

Twenty-three antimicrobial agents, including 4 new broadspectrum beta-lactam antibiotics were tested against 50 clinical isolates of Campylobacter jejuni. The activity of metabolites of metronidazole and tinidazole was also tested. Minimum inhibitory concentrations (MIC) were determined by agar dilution. beta-lactamase production was detected by a chromogenic cephalosporin method. All strains were susceptible to erythromycin, clindamycin, chloramphenicol, furazolidone, aminoglycosides (including gentamicin), cefotaxime and NF-thienamycin. All isolates were resistant to penicillin, cephalothin, cefoperazone, vancomycin, rifampicin and trimethoprim; beta-lactamase was detected in 2% of isolates. Some strains were resistant and others sensitive to the other drugs tested, which included ampicillin, moxalactum tetracycline, metronidazole and tinidazole. The 'hydroxy' metabolites of metronidazole and tinidazole were more active than the parent compounds.

In vitro activity of seventeen antimicrobial agents against Gardnerella vaginalis

The in vitro activity of 17 antimicrobial agents was tested against 25 clinical isolates of Gardnerella vaginalis. Minimum inhibitory concentrations were determined by agar dilution. The isolates were sensitive to penicillin, ampicillin, ticarcillin, piperacillin, cephalothin, cefoxitin, cefotaxime, cefoperazone, N-formimidoyl-thienamycin, chloramphenicol, clindamycin and erythromycin. MIC90 for the beta-lactam antibiotics ranged from 0.12 mg/l for penicillin to 2 mg/l for ticarcillin. Cefoperazone was the most active cephalosporin, inhibiting all isolates at 1.0 mg/l. N-formimidoylthienamycin was the most active of the newer beta-lactam compounds inhibiting all isolates with a concentration of 0.5 mg/l. Clindamycin and erythromycin were highly active, inhibiting all isolates at 0.6 mg/l. Susceptibility to tetracycline, gentamicin, metronidazole and tinidazole varied between strains. All isolates were resistant to rosoxacin. The hydroxy-metabolites of metronidazole and tinidazole were more active than the parent compounds, inhibiting all isolates.

Vancomycin therapy for methicillin-resistant Staphylococcus aureus

Ten patients with bacteremia due to methicillin-resistant Staphylococcus aureus were treated with vancomycin. These patients were compared with matched controls, nine bacteremic patients with methicillin-sensitive S. aureus, and one patient with penicillin-sensitive S. aureus. Controls were treated with a penicillin. There were no significant differences in time to defervescence, metastatic infections, relapse, mortality, need for surgical drainage, or duration of therapy. Fifteen of 19 episodes of serious methicillin-resistant S. aureus infection responded to vancomycin. Severe toxic effects included tinnitus, neutropenia, rash, and possible nephrotoxicity. Tolerance (a minimal bactericidal concentration to minimal inhibitory concentration ratio of at least 32), but not a minimal bactericidal concentration of at least 32 mg/L, correlated with therapeutic failure (respectively, p = 0.04 and p = 0.11, Fisher's exact test). Bacteremic infections due to methicillin-resistant and methicillin-sensitive S. aureus cause similar morbidity and mortality. Vancomycin is effective but potentially toxic therapy for most serious infections due to methicillin-resistant S. aureus. In-vitro tests may not predict therapeutic efficacy.

Campylobacter jejuni: incidence in processed broilers and biotype distribution in human and broiler isolates

Campylobacter jejuni was isolated from 18 of 40 processed broiler carcasses and 134 of 327 cloacal swabs obtained at four processing plants in Sydney, Australia. Three of four flocks examined carried C. jejuni. Eighty-two percent of chicken and 98% of human isolates from the area were of identical biotypes.

A rapid slid coagglutination test-an alternative to the fluorescent antibody test for the identification of Neisseria gonorrhoeae

The Phadebact(R) Gonococcus Test, a slide coagglutination test, was compared with the Difco fluorescent antibody test for the identification of Neisseria gonorrhoeae isolated from 18- to 24-hour primary plates. A total of 316 morphologically characteristic, oxidase-positive, Gram-negative diplococci were tested. Altogether 298 isolates were identified definitively as N. gonorrhoeae by a rapid carbohydrate utilisation test; 287 of the 298 isolates of N. gonorrhoeae were identified by the coagglutination test, a sensitivity of 96%. The sensitivity of the fluorescent antibody test was 85% (254 of 298 isolates). False-positive results due to cross-reactions with non-gonococcal Neisseria were uncommon (1 of 18 non-gonococcal isolates in the coagglutination test, a specificity of 94%; 2 of 18 in the fluorescent antibody test, a specificity of 88%). None of the 14 other contaminant organisms seen frequently on primary isolation media gave positive reactions. Interpretation of the coagglutination test proved to be difficult initially. Thirty-two (10%) coagglutination tests had to be repeated; 3 of the 32 (1% of the total isolates tested) remained uninterpretable.