Does blue-violet filtering in contact lenses improve contrast sensitivity?

PURPOSE: The work is aimed at (i) comparing photopic contrast sensitivity (CS) of healthy subjects in an indoor environment with either blue-violet filtering (BVF) or clear contact lenses (CLs) and (ii) investigating a possible dependence of the CS variation on the subjects' intrinsic CS, measured with clear CLs. METHODS: Optical transmittance of BVF and clear CLs was measured by a spectrophotometer. Photopic CS was measured monocularly on forty-one subjects (nineteen in the age range 20-36 years and twenty-two in the age range 44-66 years) by a digital optotype system at spatial frequencies from 1.5 to 18 cpd, wearing either clear or BVF CLs. The results are indicated as CSclear and CSBVF, respectively. RESULTS: Transmittance curves in the visible range of the two CLs are very similar, despite an absorption band in the BVF CL spectrum with the minimum of transmittance at 428 ± 4 nm equal to about 79%. For both CSclear and CSBVF, no significant CS difference was found between younger and older adults. The difference [log(CSBVF) - log(CSclear)] showed a decreasing trend and changed sign from positive to negative as a function of log(CSclear) with correlation Spearman's Rho coefficients ranging from 0.80 to 0.88 (p < 0.01 at all spatial frequencies). CONCLUSION: In the choice of a BVF CL, practitioners should take into consideration that it can influence photopic CS, improving it for subjects who have a relatively low CS with clear CLs, and worsening it for subjects who have a relatively high CS with clear CLs. BVF can affect positively the CS by reducing intraocular scattering. However, it can also cause a reduction in light intensity, which contributes to the formation of the retinal image. The positive or negative influence of BVF CLs compared to clear ones on CS is attributed to a balance among these effects.

A position statement and practical guide to the use of particulate filtering facepiece respirators (N95, FFP2, or equivalent) for South African health workers exposed to respiratory pathogens including Mycobacterium tuberculosis and SARS-CoV-2.

SUMMARY: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is transmitted mainly by aerosol in particles <10 µm that can remain suspended for hours before being inhaled. Because particulate filtering facepiece respirators ('respirators'; e.g. N95 masks) are more effective than surgical masks against bio-aerosols, many international organisations now recommend that health workers (HWs) wear a respirator when caring for individuals who may have COVID-19. In South Africa (SA), however, surgical masks are still recommended for the routine care of individuals with possible or confirmed COVID-19, with respirators reserved for so-called aerosol-generating procedures. In contrast, SA guidelines do recommend respirators for routine care of individuals with possible or confirmed tuberculosis (TB), which is also transmitted via aerosol. In health facilities in SA, distinguishing between TB and COVID-19 is challenging without examination and investigation, both of which may expose HWs to potentially infectious individuals. Symptom-based triage has limited utility in defining risk. Indeed, significant proportions of individuals with COVID-19 and/or pulmonary TB may not have symptoms and/or test negative. The prevalence of undiagnosed respiratory disease is therefore likely significant in many general clinical areas (e.g. waiting areas). Moreover, a proportion of HWs are HIV-positive and are at increased risk of severe COVID-19 and death. RECOMMENDATIONS: Sustained improvements in infection prevention and control (IPC) require reorganisation of systems to prioritise HW and patient safety. While this will take time, it is unacceptable to leave HWs exposed until such changes are made. We propose that the SA health system adopts a target of 'zero harm', aiming to eliminate transmission of respiratory pathogens to all individuals in every healthcare setting. Accordingly, we recommend: the use of respirators by all staff (clinical and non-clinical) during activities that involve contact or sharing air in indoor spaces with individuals who: (i) have not yet been clinically evaluated; or (ii) are thought or known to have TB and/or COVID-19 or other potentially harmful respiratory infections;the use of respirators that meet national and international manufacturing standards;evaluation of all respirators, at the least, by qualitative fit testing; andthe use of respirators as part of a 'package of care' in line with international IPC recommendations. We recognise that this will be challenging, not least due to global and national shortages of personal protective equipment (PPE). SA national policy around respiratory protective equipment enables a robust framework for manufacture and quality control and has been supported by local manufacturers and the Department of Trade, Industry and Competition. Respirator manufacturers should explore adaptations to improve comfort and reduce barriers to communication. Structural changes are needed urgently to improve the safety of health facilities: persistent advocacy and research around potential systems change remain essential.

National Neonatal Sepsis Task Force launch: Supporting infection prevention and surveillance, outbreak investigation and antimicrobial stewardship in neonatal units in South Africa.

Despite a substantial decline in childhood mortality rates in South Africa (SA), progress in neonatal mortality reduction has been much slower. Severe bacterial infections remain a leading cause of neonatal morbidity and a direct cause of 13.1% of neonatal deaths among babies >1 kg. The incidence of hospital-acquired infections, antimicrobial resistance and outbreaks of infections in SA neonatal units is substantial, and is possibly higher than the currently available estimates. The SA Neonatal Sepsis Task Force was launched in Port Elizabeth, SA, on 13 September 2019 to provide technical advice and guidance on surveillance for neonatal sepsis, infection prevention, case management, antimicrobial stewardship and containment of neonatal unit outbreaks.

Veterinary treatment strategies for clinical mastitis in dairy cows in Sweden.

To evaluate if Swedish veterinary guidelines on use of antimicrobials in cases of clinical mastitis in dairy cows have been adopted by veterinary practitioners, their treatment strategies were evaluated in a cross-sectional study using a web-based questionnaire. Another aim was to study if the strategies differed among veterinarians due to year and country of exam, sex, region, numbers of mastitis cases per month, and postgraduate training in herd health using multivariable logistic regression models. In total, 267 of 741 (36 per cent) veterinarians contacted answered the questionnaire satisfactorily. Most considered bacteriological diagnostics important, but many veterinarians made treatment decisions without collecting information on antimicrobial susceptibility. Moreover, few veterinarians used measuring tape to assess bodyweight before dosing parenteral antimicrobials. Year of exam and postgraduate training were the veterinary demographic factors associated with most treatment routines. The questions associated with most demographic factors were if antimicrobial treatment is affected by knowledge on earlier udder pathogens in the herd, and how often NSAID and follow-up of treatment using milk somatic cell count are used. Overall, the veterinarians followed the Swedish guidelines rather well, but discrepancies in need for improvement were found.

Molecular typing of drug-susceptible and -resistant Mycobacterium tuberculosis in Johannesburg, South Africa.

SETTING: Knowledge about spoligotyping families of drug-susceptible and drug-resistant Mycobacterium tuberculosis circulating in the Johannesburg area, South Africa, is lacking. OBJECTIVE: To determine the genetic diversity of M. tuberculosis isolates circulating in the Johannesburg area and to compare the results with both national and international databanks. DESIGN: Five hundred cultured M. tuberculosis isolates from within the greater Johannesburg metropolitan area collected from January 2009 to December 2010 were obtained from the National Health Laboratory Services (NHLS) Mycobacteriology Referral Laboratory, Johannesburg, in MGIT vials. The isolates were specimens from individuals with tuberculosis (TB) symptoms and known TB patients submitted to the NHLS for routine mycobacterial culture and drug susceptibility testing. The isolates were genotyped using spoligotyping. RESULTS: Spoligotyping generated 62 shared types, with 92% (458/500) of the sample size matching pre-existing shared types. Of the 62 shared types, eight families were predominant (clustering from 16 to 132), representing 64% (340/500) of the sample. The Beijing family (135/500) predominated (P < 0.001). CONCLUSION: TB incidence in Johannesburg does not appear to be due to clonality, but is rather due to diverse circulating strains, namely the Beijing family, followed by the S, Latin American-Mediterranean and T families.

Treatment outcomes of multidrug-resistant tuberculosis patients in Gauteng, South Africa.

PURPOSE: Multidrug-resistant tuberculosis (MDR-TB) is associated with lengthy treatment, expensive and potentially toxic regimens, and high rates of treatment failure and death. This study describes the outcomes of 351 MDR-TB patients who started treatment between 2004 and 2007 at the provincial MDR-TB referral hospital in Johannesburg, South Africa, and investigates risk factors associated with death. METHODS: The study involved the assessment of factors associated with treatment outcomes using a retrospective review of patient records, drug-susceptibility data and spoligotyping of isolates. RESULTS: Treatment success (completion/cure) was recorded in 158 (48.8 %) patients, while 65 (20 %) died, 93 (28.7 %) defaulted, 8 (2.5 %) failed treatment, 11(3.1 %) were transferred out to other health facilities and 16 (4.6 %) had no recorded final outcome. The proportion of successful treatment increased significantly over time. Univariable and multivariable analysis (P = 0.05) identified the year of MDR-TB diagnosis and spoligotype-defined families as factors associated with treatment outcome. No associations were found between treatment outcome and human immunodeficiency virus (HIV) status, previous TB and additional MDR resistance to streptomycin or ethambutol. Molecular typing of the strains revealed a diverse group of spoligotypes, with Beijing, LAM4 and H3 making up the largest groups. CONCLUSIONS: This is the first published study to investigate treatment outcomes at this facility and to find a link between genotype and treatment outcome, suggesting that genotype determination could potentially serve as a prognostic factor.

Prevalence survey of healthcare-associated infections in Argentina; comparison with England, Wales, Northern Ireland and South Africa.

BACKGROUND: Prevalence surveillance methodology is the systematic observation of the occurrence and distribution of healthcare-associated infections (HCAIs) so that appropriate actions can be taken. AIM: The objectives of a prevalence survey with an international validated methodology were to determine the prevalence of HCAIs for the first time in Argentina, and to provide data which could be used for international benchmarking. METHODS: In 2008, an HCAI prevalence survey was carried out in 39 hospitals in seven of 23 provinces in Argentina, with methodology identical to that employed by the Hospital Infection Society in the third prevalence survey of HCAIs in acute hospitals in the British Isles. Data collected were processed and analysed at the Northern Ireland Healthcare-Associated Infection Surveillance Centre at Belfast. FINDINGS: A total of 4249 patients were surveyed; 480 of these had at least one HCAI, resulting in a prevalence of 11.3% of patients. Male prevalence was 13.6% and female 9.0%. The most common HCAIs were pneumonia (3.3%), urinary tract infection (3.1%), surgical site infection (2.9%), primary bloodstream infection (1.5%), and soft tissue infections (1.2%). Among the 1027 patients who underwent surgery, the prevalence of surgical site infection was 10.2%. The prevalence of meticillin-resistant Staphylococcus aureus was 1.1%, accounting for 10.0% of all HCAI isolates. The results for Argentina show higher HCAI rates compared with corresponding findings for England, Wales, Northern Ireland and South Africa. CONCLUSION: This survey will contribute to the prioritization of resources and help to inform Departments of Health and hospitals in the continuing effort to reduce HCAIs.

Clinically significant anaerobic bacteria isolated from patients in a South African academic hospital: antimicrobial susceptibility testing.

BACKGROUND. Increasing resistance to some antimicrobial agents among anaerobic bacteria has made susceptibility patterns less predictable. METHOD. This was a prospective study of the susceptibility data of anaerobic organisms isolated from clinical specimens from patients with suspected anaerobic infections from June 2005 until February 2007. Specimens were submitted to the microbiology laboratory at Charlotte Maxeke Johannesburg Academic Hospital, where microscopy, culture and susceptibility testing were performed the using E test® strip minimum inhibitory concentration method. Results were interpreted with reference to Clinical and Laboratory Standards Institute guidelines for amoxicillin-clavulanate, clindamycin, metronidazole, penicillin, ertapenem, cefoxitin, ceftriaxone, chloramphenicol and piperacillin-tazobactam. RESULTS. One hundred and eighty anaerobic isolates were submitted from 165 patients. The most active antimicrobial agents were chloramphenicol (100% susceptible), ertapenem (97.2%), piperacillin-tazobactam (99.4%) and amoxicillin-clavulanic acid (96.7%). Less active were metronidazole (89.4%), cefoxitin (85%), clindamycin (81.7%), ceftriaxone (68.3%) and penicillin (33.3%). CONCLUSION. Susceptibility testing should be performed periodically to identify emerging trends in resistance and to modify empirical treatment of anaerobic infections.

NDM-1 has arrived: first report of a carbapenem resistance mechanism in South Africa.

The New Delhi Metallo-ß-lactamase (NDM) resistance mechanism in Enterobacteriaceae threatens to render serious Gram-negative infections untreatable. The NDM-1 enzyme hydrolyses all available penicillin, cephalosporin and carbapenem antibiotics, and is commonly accompanied by additional resistance mechanisms to multiple antibiotic classes. Initially identified as a significant healthcare risk on the Indian sub-continent, it has rapidly become a global problem, posing significant diagnostic and management challenges. Here we report the first laboratory-confirmed case of NDM-1 in South Africa.

Molecular characterization of clinical methicillin-resistant Staphylococcus aureus isolates in South Africa.

Eighty-two percent of 320 clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates from various infection sites collected throughout South Africa were separated into five major globally prevalent clusters by SmaI pulsed-field gel electrophoresis, spa, and SCCmec typing. Only one Panton-Valentine leukocidin-positive isolate was detected. This is the first detailed MRSA epidemiology study for the whole country.

Antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus isolates from South Africa.

OBJECTIVE: Trends in the antibiotic susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) are regularly investigated in many countries, but minimal countrywide data are available for South Africa. The aim of this study was to describe the antibiotic susceptibility patterns of MRSA isolates collected in South Africa. DESIGN: Susceptibility testing of 248 MRSA isolates collected from 15 National Health Laboratory Services (NHLS) and 8 private laboratories against 17 antibiotics was performed using the disc diffusion method. Demographic data were collected and correlated with antibiotic resistance patterns. RESULTS: Antibiotic resistance of MRSA to erythromycin, tetracycline, trimethoprim/sulfamethoxazole, gentamicin and ciprofloxacin ranged between 55% and 78%, while all isolates were susceptible to teicoplanin, linezolid, vancomycin and quinopristin/dalfopristin. A significant difference in the resistance pattern of the isolates towards certain antimicrobial agents was identified among adults and children, as well as between isolates collected from the private and NHLS laboratories. CONCLUSION: This is the first extensive report on the antimicrobial susceptibilities of South African MRSA isolates. These data can assist treatment decisions and form a baseline for further surveillance.

Antimicrobial Susceptibility Patterns of Selected Invasive Pathogens from Public Sector Hospitals in South Africa; 2007

Retrospective antibiotic surveillance data of selected invasive pathogens isolated from blood and cerebrospinal fluid at public sector hospitals in South Africa in 2007 are presented. Antimicrobial susceptibilities were determined according to the 2007 Clinical and Laboratory Standards Institute criteria. Klebsiella pneumoniae remains a highly resistant pathogen; with approximately half of all strains producing extended-spectrum beta-lactamases. All laboratories reported considerable resistance among Acinetobacter spp. Approximately 50-60of Staphylococcus aureus isolates from blood were resistant to cloxacillin. Among Streptococcus pneumoniae isolates from blood and cerebrospinal intermediate resistance to penicillin. Resistance to ceftriaxone in S. pneumoniae was rare

Pseudomonas aeruginosa bacteraemia in an academic hospital in South Africa.

OBJECTIVES: The aim of the study was to determine the clinical manifestations, outcome of and prognostic factors associated with Pseudomonas aeruginosa bacteraemia at Chris Hani Baragwanath Hospital, Johannesburg, during the period 1998 - 1999, to describe and quantify resistance to antipseudomonal drugs, to characterise bacteraemic isolates, and to investigate the clustering and genotype distribution of drug-susceptible and multiply-resistant strains in the hospital. METHODS: Clinical and laboratory investigations, culture and antimicrobial susceptibility testing were performed. Bacteraemic isolates were typed by endonuclease macrorestriction. Those with > or = 97% band pattern similarity were assigned genotype status. RESULTS: Of 91 P. aeruginosa blood isolates, 52 (57.1%) were nosocomially acquired. Underlying conditions associated with episodes were burns in 24 (28%) and HIV infection in 21 (24%). Multidrug resistance was present in 14 (15.4%) of isolates from 91 episodes. In 79 episodes where the outcome was known, 37 (46.8%) of the patients died. Case fatality rates were 75% in adults and 25% in children. Being a child, receiving appropriate antimicrobial treatment and admission to a specialised care unit were significantly associated with improved prognosis. CONCLUSION: P. aeruginosa bacteraemia was associated with outbreaks caused by two multiply-resistant genotypes. Eighteen antimicrobial-susceptible isolates from bacteraemic episodes in paediatric wards, 9 in HIV-seropositive children, could be linked to small outbreaks in both hospitalised and community-based children.

Genotypic diversity of extensively drug-resistant tuberculosis (XDR-TB) in South Africa.

SETTING: The epidemiology of extensively drug-resistant tuberculosis (XDR-TB), an emerging threat to TB control, is not well understood. OBJECTIVE: To gain insight into the genotypic population structure of XDR Mycobacterium tuberculosis strains in South Africa using a molecular approach and thereby determine whether XDR-TB is mainly acquired or transmitted. DESIGN: Sputum isolates from patients with multidrug-resistant tuberculosis (MDR-TB) were submitted to the National Referral Laboratory for second-line drug susceptibility testing. The XDR-TB isolates were spoligotyped and these data were compared to the geographic origin of the isolate. RESULTS: Of the 699 MDR-TB isolates submitted for testing between June 2005 and December 2006, 101 (17%) patients had a culture that was resistant to either ofloxacin or kanamycin, and 41 (6%) were resistant to both drugs (XDR-TB). Spoligotyping of the XDR-TB isolates identified 17 genotypes. As a result of the high genotypic diversity and geographical distribution, we estimate that between 63% and 75% of cases developed XDR-TB through acquisition. CONCLUSION: Acquisition of extensive drug resistance appears to be the primary mechanism driving the XDR-TB epidemic in South Africa. This urgent TB control issue has to be addressed to prevent the spread of this potentially incurable disease.

Efflux pump activity in fluoroquinolone and tetracycline resistant Salmonella and E. coli implicated in reduced susceptibility to household antimicrobial cleaning agents.

It has been shown that the inappropriate use of antimicrobial household agents selects for organisms with resistance mechanisms (e.g. efflux pumps), which could lead to the development of antibiotic resistance. The reverse hypothesis, that antibiotic-resistant organisms become tolerant to other antibacterial agents (e.g. disinfectants) due to the action of efflux pumps, has however not been extensively examined. The objective of this study was to establish whether there is a link between antibiotic resistance in potential gastrointestinal pathogens and reduced sensitivity of these organisms to commonly used household antimicrobial agents. In this study, tetracycline and ofloxacin sensitive and resistant Escherichia coli (9 strains) and Salmonella spp. (8 strains) were isolated from poultry and clinical samples. In order to assess whether these bacteria had active efflux pumps, ethidium bromide accumulation assays were performed. Extrusion of the active components of three commercial household agents (triclosan, sodium salicylate, and ortho-phenylphenol) by efflux pumps was tested using spectrophotometric accumulation assays. In order to simulate the kitchen environment, in-use disinfectant testing using the commercial household agents was performed to determine changes in their efficacy due to antibiotic resistance. Active efflux pump activity and extrusion of all three active ingredients was observed only in the antibiotic resistant organisms. The antibiotic sensitive bacteria were also more susceptible than the resistant isolates to the household antimicrobial agents at concentrations below that recommended by the manufacturer. These resistant bacteria could potentially be selected for and result in hard to treat infections.

Contamination of chicken carcasses in Gauteng, South Africa, by Salmonella, Listeria monocytogenes and Campylobacter.

The presence of the foodborne pathogens, Salmonella spp., Listeria monocytogenes and Campylobacter spp., on 99 fresh and frozen chicken carcasses sourced from various retailers in Gauteng, South Africa, was investigated. Using culture methods, 60.6% of the carcasses were found to be contaminated with one or more pathogens, with 19.2%, 19.2% and 32.3% of the carcasses being found to harbour Salmonella, L. monocytogenes and Campylobacter, respectively. The extent of contamination with one or more pathogens was not significantly different (p>0.1) between fresh or frozen samples or between samples from butcheries, supermarkets or street vendors. Significantly more (p<0.1) fresh carcasses from butcheries than from other outlets were contaminated with Salmonella, while more fresh carcasses from supermarkets were contaminated with Campylobacter. The proportion of carcasses with L. monocytogenes from all sources were similar. Polymerase chain reaction (PCR) results indicate an even higher extent of pathogen contamination, but the PCR techniques need to be further refined before they can be used routinely.