Perfluorodecalin and bone regeneration.

Perfluorodecalin (PFD) is a chemically and biologically inert biomaterial and, as many perfluorocarbons, is also hydrophobic, radiopaque and has a high solute capacity for gases such as oxygen. In this article we have demonstrated, both in vitro and in vivo, that PFD may significantly enhance bone regeneration. Firstly, the potential benefit of PFD was demonstrated by prolonging the survival of bone marrow cells cultured in anaerobic conditions. These findings translated in vivo, where PFD incorporated into bone-marrow-loaded 3D-printed scaffolds substantially improved their capacity to regenerate bone. Secondly, in addition to biological applications, we have also shown that PFD improves the radiopacity of bone regeneration biomaterials, a key feature required for the visualisation of biomaterials during and after surgical implantation. Finally, we have shown how the extreme hydrophobicity of PFD enables the fabrication of highly cohesive self-setting injectable biomaterials for bone regeneration. In conclusion, perfluorocarbons would appear to be highly beneficial additives to a number of regenerative biomaterials, especially those for bone regeneration.

Cortical bone screw fixation in ionically modified apatite cements.

Hydroxyapatite cements are used in reconstruction of the face; usually in well-defined cavities where the cement can be stabilized without the need for internal fixation. A hydroxyapatite cement that could enable screw fixation and some loading therefore has considerable potential in maxillofacial reconstruction. It has been demonstrated recently that water demand of calcium phosphate cements can be reduced by ionically modifying the liquid component. This study investigated the capacity of an ionically modified precompacted apatite cement to retain self-tapping cortical bone screws. Screw pullout forces were determined in the direction of the screw long axis and perpendicular to it, using cortical bone and polymethylmethacrylate cement as a control. In bending pullout tests, measured forces to remove screws from ionically modified precompacted cement were insignificantly different from cortical bone. However, pullout forces of bone screws from hydroxyapatite cement decreased with aging time in vitro.

In-depth morphological changes and embrittlement near the wear surface of UHMWPE inserts from uncemented hip systems.

Polyethylene hip cups were examined with optical and electron microscopy after permanganic etching, a technique that allows in-depth examination from the articulating surface downward. In addition to wear features present on the surface, novel defects were revealed in implants after retrieval from the body but not in as-manufactured controls. They were incipient cracks that indicated the existence of an embrittled layer extending 10 microm or more into the implant from the wear surface after exposure to the body environment. The lengths of the cracks, which were perpendicular to the tensile stresses responsible for their formation, were mostly more or less parallel to the wear surface. The embrittlement and cracking revealed are probably major contributors to the wear of polyethylene implants in the body. Poor particle consolidation may be a contributory factor, but it was not observed to be the primary cause of implant wear within the body.

On morphology of consolidated UHMWPE resin in hip cups.

The microstructure of replacement hip cups made from ultra-high molecular weight polyethylene (UHMWPE) has been revealed by permanganic etching to bring out the fine details. Specimens are examined by optical microscopy according to the Nomarski technique, and by scanning and transmission electron microscopy. In all cups the original reactor particles are visible. Optical microscopy is most productive in revealing variations not only in the texture of different individual particles, but also in the degree of consolidation of a particle with its neighbours. Both these factors differ according to the material and process. Electron microscopy reveals the existence of pockets of lower molecular weight material which has been expelled from the particles by the original sintering process.

Respiratory Chlamydial infections in a Hong Kong teaching hospital and association with coronary heart disease.

The microimmunofluorescence antibody technique was used to determine the seroprevalence of antibodies to Chlamydia pneumoniae and Chlamydia psittaci from hospitalized patients in Hong Kong. Antibodies to C. pneumoniae were found in 54.8% of 157 patients hospitalized with respiratory disease, in 71.1% of 83 patients with cardiac disease and in 31.2% of 93 patients without either respiratory or cardiac disease. Antibodies to C. psittaci were found in 0.9% of the combined study groups. There was serological evidence of C. pneumoniae being the responsible agent in 24.8% of the severe respiratory cases. A significant correlation between antibody prevalence and coronary heart disease was identified during the study.

Fatal rickettsial meningitis in Hong Kong: a need for rapid laboratory diagnosis.

A 22-year-old Chinese male, investigated elsewhere for fever and myalgia, was transferred to our hospital drowsy, unresponsive to commands and with a petechial rash. Partially treated meningococcal meningitis was suspected and high-dose antibiotics were immediately started. Rising Weil-Felix titres occurred too late for anti-rickettsial therapy to prevent a fatal outcome. Subsequent specific serology showed rising titres against Rickettsia conori. The desirability of more rapid and reliable methods of laboratory diagnosis of rickettsial infection is evident.

Viral, mycoplasmal and chlamydial lower respiratory tract infections in Hong Kong: cost and diagnostic value of serology.

A hospital virology laboratory in Hong Kong tested 10,852 sera by complement fixation (CF) for antibodies against agents of respiratory disease between 1 July 1986 and 31 December 1991. Ten commercially supplied antigens were used: influenza virus types A and B, parainfluenza virus types 1, 2 and 3, adenovirus, respiratory syncytial virus (RSV), Mycoplasma pneumoniae, Chlamydia species and Coxiella burnetii. Single sera comprised 69% of the total, including sera from 7488 patients investigated for LRTI with paired acute and convalescent samples. A total of 167 pairs (21.6%) showed rising CF titres, 82 of them against M. pneumoniae. Of the 809 patients, 365 were children under 11 years of age: 115 (31.5%) showed rising titres, including 51 with antibodies against M. pneumoniae, 21 against RSV, 17 against adenovirus and 10 against parainfluenza type 3. Viral antigen detection by immunofluorescence and virus isolation were also used: these methods yielded more positive findings than did CF test serology for the corresponding agents. The cost of the tests performed is discussed in relation to their contribution to the aetiological diagnosis of LRTI, and changes in the service to be offered are outlined.

Increasing prevalence of antimicrobial resistance among organisms isolated from blood culture in a Singapore hospital.

The blood culture isolates obtained over the period 1985-1990 in a general teaching hospital were reviewed to determine trends in the prevalence of resistance to antimicrobial drugs. The percentages of Staphylococcus aureus isolates resistant to methicillin increased each year. Resistance among coagulase negative staphylococci also increased in prevalence: by 1990 approximately 50% of such isolates were resistant to methicillin, erythromycin, co-trimoxazole and gentamicin, 24% were resistant to clindamycin, 20% to fucidic acid but only 0.5% to vancomycin. Isolates of Enterobacteriaceae, excluding community-acquired salmonellae, showed increasing prevalence of resistance to beta-lactams, as did Acinetobacter spp isolates to gentamicin, co-trimoxazole and ceftriaxone. The isolates of Pseudomonas aeruginosa were exceptional, having no evident increase in the prevalence of resistance during the period. The rapid increases observed in relation to the other pathogens indicate the need for an antibiotic policy based on continuous surveillance of susceptibility patterns in the hospital.

The laboratory diagnosis of rickettsial diseases in Hong Kong.

Indirect immunoperoxidase (IP) tests against antigens of Rickettsia typhi, R. sibirica and R. tsutsugamushi were carried out on serum samples from 10 patients known to have high titres against one or more Proteus OX antigens in the Weil-Felix (WF) test. The IP test confirmed rickettsial infection in nine of the 10 patients, giving unequivocal indications of the grouping of the infecting Rickettsia species and, in one instance, showing a diagnostic IgM titre in a specimen taken on day 3 of the patient's illness. IP tests confirmed four cases of spotted fever group rickettsial infection, three cases of urban or murine typhus and two of scrub typhus.

A study of 245 infected surgical wounds in Singapore.

The aims of the study were to correlate the laboratory detection rate of wound infections with the actual wound infection rate, and to analyse the bacteriology of these wounds to provide a rationale for antibiotic usage in prophylaxis and treatment of surgical wound infections. The wound infection rate in a general surgical unit was determined using the most comprehensive surveillance available to us and was correlated with the laboratory detection rate. A correlation coefficient of 0.8 was obtained, allowing a reasonable estimation of the actual wound infection rate from laboratory data. Review of the bacteriology of consecutive infected surgical wounds over a 4 year period in a university hospital, revealed that the commonest organisms cultured were Staphylococcus aureus, Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, enterococci and beta-haemolytic streptococci. Methicillin-resistant S. aureus (MRSA) caused 50% of all staphylococcal wound infections. All MRSA isolates were sensitive to fusidic acid and vancomycin. All the non-MRSA isolates of S. aureus were sensitive to cephalexin. Some 89% of E. coli were sensitive to gentamicin, with 93% and 100% sensitive to cefuroxime and ceftriaxone respectively. Klebsiella isolates have shown an increased resistance to aminoglycosides, with a new strain from one patient, isolated in 1990, resistant to penicillins, aminoglycosides and third generation cephalosporins. Pseudomonas spp., enterococci and beta-haemolytic streptococci did not show a change in resistance patterns over the same time period.

Prevalence of bacterial agents of diarrhoeal disease at the National University Hospital, Singapore and their resistance to antimicrobial agents.

Over a 50-month period, 4,508 stool specimens from patients with diarrhoea were bacteriologically examined at the National University Hospital, Singapore. Salmonella serotypes other than the typhoid and paratyphoid bacilli were the most common finding, being isolated in 10.8% of cases. Campylobacter jejuni was unexpectedly infrequent (1.9%); Aeromonas hydrophila was found in 1.8%. No other aerobic pathogen occurred in more than 1% of cases. Clostridium difficile was sought only when requested, and was isolated from 9.6% of cases tested. Testing for enteropathogenic Escherichia coli was limited to children under 1 year old. Gentamicin was active against the greatest number of aerobic isolates, followed by chloramphenicol and cotrimoxazole. The C. difficile isolates were all sensitive to metronidazole.

A comparison of costs and effectiveness of the BACTEC NR-730 system and a conventional method of blood culture.

Results and costs of the first six months experience with BACTEC NR-730 were compared with a series of blood cultures performed by the conventional method previously used. The newer technology detected the growth of 14.1% of significant isolates on the day of receipt of the specimens. The previous method lacked blind subcultures on the day of receipt and therefore detected growth only after overnight incubation. No direct comparison of the sensitivities of the methods was possible, but the percentages of cultures yielding significant isolates were similar for the two methods. With the new method, technicians needed less time for daily screening of blood cultures, fewer subcultures were required and less contamination was observed. The method used to calculate the directly-related variable costs of the two methods is set out. In the particular situation reported, workload and labor costs were such that introduction of BACTEC NR-730 resulted in a saving on variable costs.

Streptococcal serotypes newly associated with epidemic post-streptococcal acute glomerulonephritis.

The increasing incidence of reported scabies in Trinidad, from 24.2/100,000 population in 1984 to 59.5/100,000 in 1985, led to a careful monitoring in 1986 of all patients with post-streptococcal acute glomerulonephritis (PSAGN). There were 181 cases of PSAGN; 84 beta-haemolytic streptococcal isolates from 72 patients were sent to the Central Public Health Laboratory, Colindale, for grouping and serotyping. The PSAGN epidemic of 1986 was bimodal. Streptococci of M-type 73 appeared to be associated with the first phase (March-May) and comprised 20% of the isolates serotyped. New to Trinidad, streptococci of M-type 48 (4% of the isolates serotyped) preceded the first phase of the epidemic and were isolated from two patients with PSAGN. Provisional type (PT) 5757, also new to Trinidad, had been previously identified only among serotypes from the United Kingdom and the Federal Republic of Germany. This type was isolated from seven patients, in six from skin lesions and in one from the throat. PT 5757 occurred during the first wave of the epidemic and comprised 14% of the strains serotyped. Thus, the first wave of the bimodal epidemic involved serotypes M73, M48 and PT 5757. The more intense second phase (July-October) was associated with the previously documented nephritogenic M-type 55.

Epidemiology of AIDS and HIV infection in the Caribbean.

A review of surveillance data on AIDS and HIV infection in the 18 English-speaking Caribbean countries and Suriname suggests that the epidemiologic pattern of AIDS in the Caribbean is evolving from an epidemic that began in 1983 among homosexual and bisexual males to one in which cases are increasingly resulting from heterosexual contact, with different countries at various stages of transition. Overall, there has been a decline in the male to female case ratio. Perinatal transmission is already a major problem in many countries--19% of cases in the Bahamas are among children under 15 years of age. Serosurveys conducted in Trinidad and Tobago, Jamaica, Antigua, St. Vincent and the Grenadines, and other countries show high HIV seroprevalence among homosexuals (15-40%), prisoners (4-10%), prostitutes (up to 13%), and cocaine users (2%); at present, prevalence in the general population continues to be low.