Panton-Valentine leukocidin-producing Staphylococcus aureus

Analysis of poor prognostic factors for septic arthritis of the hip in children: a case series of 76 patients

The clinical characteristics, treatment and outcomes of children with septic arthritis of the hip in our hospital were analyzed to identify the risk factors for a poor prognosis. The clinical data of 76 children with septic arthritis of the hip who were treated at our hospital from January 2010 to December 2020 were retrospectively analyzed. According to the most recent follow-up data, the patients were classified as good prognosis or poor prognosis. The differences between the two groups were analyzed. From January 2010 to December 2020, a total of 76 children with septic arthritis of the hip were admitted to our hospital, comprising 52 (68.4%) with a good prognosis and 24 (31.6%) with a poor prognosis. The risk of a poor prognosis was significantly higher in the group with time from onset to surgery >22 days than in the group with time from onset to surgery <11 days. The risk of poor prognosis in the group with C-reactive protein (CRP) > 100 mg/L was significantly higher than that in the group with CRP < 20 mg/L. Time from onset to surgery >14 days and CRP > 93 mg/L were the cutoff values for a poor prognosis. Significant elevation of CRP and prolonged time from onset to surgery in children with septic arthritis of the hip are risk factors for a poor prognosis. Early diagnosis and effective treatment are very important because delays in these factors can lead to a poor prognosis. Level of Evidence: Level II, retrospective study.

Microbiology of Severe Community-Acquired Pneumonia and the Role of Rapid Molecular Techniques

The microbiology of severe community acquired pneumonia (SCAP) has implications on management, clinical outcomes and public health policy. Therefore, knowledge of the etiologies of SCAP and methods to identify these microorganisms is key. Bacteria including Streptococcus pneumoniae, Staphylococcus aureus and Enterobacteriaceae continue to be important causes of SCAP. Viruses remain the most commonly identified etiology of SCAP. Atypical organisms are also important etiologies of SCAP and are critical to identify for public health. With the increased number of immunocompromised individuals, less common pathogens may also be found as the causative agent of SCAP. Traditional diagnostic tests, including semi-quantitative respiratory cultures, blood cultures and urinary antigens continue to hold an important role in the evaluation of patients with SCAP. Many of the limitations of the aforementioned tests are addressed by rapid, molecular diagnostic tests. Molecular diagnostics utilize culture-independent technology to identify species-specific genetic sequences. These tests are often semi-automated and provide results within hours, which provides an opportunity for expedient antibiotic stewardship. The existing literature suggests molecular diagnostic techniques may improve antibiotic stewardship in CAP, and future research should investigate optimal methods for implementation of these assays into clinical practice.

Antistaphylococcal discovery pipeline; where are we now?

The serious spread of antibiotic-resistant Staphylococcal aureus strains is alarming. This is reflected by the measures governments and health-related bodies are offering to ease antibiotic drug development. Finding new active agents, preferably with novel mechanism of action, or even finding new targets for drug development are essential. In this review, we summarize the current status of novel antistaphylococcal agents undergoing clinical trials. We mainly discuss antistaphylococcal small molecules and peptides in the text with a special focus on their chemistry, while antistaphylococcal immunotherapy (antibodies) are mentioned in a summative table. This review shall serve as a summary that influences future synthetic efforts in the antistaphyloccocals development field.

Overwhelming orbital cellulitis in a neonate

This article discusses a rare ophthalmic manifestation of neonatal bacterial infection and its management, including surgical drainage. The case discussed is that of a neonate who presented with rapidly progressing ophthalmic symptoms suggestive of orbital cellulitis. The neonate also had extensive intracranial involvement and had spread to contiguous structures causing a temporal lobe abscess. As there was no local injury, a haematogenous spread was strongly considered. With blood culture and pus culture yielding the growth of Staphylococcus aureus, systemic antibiotics and surgical interventions were required to successfully manage the neonate. Through this case report, we emphasise that orbital infections are grave in neonates and may culminate into devastating intracranial complications; hence, it necessitates appropriate medical and surgical interventions right from hospital admission.

The Epidemiology of Animal-Associated Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) remains an important etiological factor of human and animal infectious diseases, causing significant economic losses not only in human healthcare but also in the large-scale farming sector. The constantly changing epidemiology of MRSA observed globally affects animal welfare and raises concerns for public health. High MRSA colonization rates in livestock raise questions about the meaning of reservoirs and possible transmission pathways, while the prevalence of MRSA colonization and infection rates among companion animals vary and might affect human health in multiple ways. We present the main findings concerning the circulation of animal-associated MRSA (AA-MRSA) in the environment and factors influencing the direction, mechanisms, and routes of its transmission. Studies have shown it that S. aureus is a multi-host bacterial pathogen; however, its adaptation mechanisms enabling it to colonize and infect both animal and human hosts are still rarely discussed. Finally, we elaborate on the most successful strategies and programs applied limiting the circulation of AA-MRSA among animals and humans. Although MRSA strains colonizing animals rarely infect humans, they undergo host-adaptive evolution enabling them to spread and persist in human populations.

Exploring the Role of Staphylococcus aureus in Inflammatory Diseases

Staphylococcus aureus is a very common Gram-positive bacterium, and S. aureus infections play an extremely important role in a variety of diseases. This paper describes the types of virulence factors involved, the inflammatory cells activated, the process of host cell death, and the associated diseases caused by S. aureus. S. aureus can secrete a variety of enterotoxins and other toxins to trigger inflammatory responses and activate inflammatory cells, such as keratinocytes, helper T cells, innate lymphoid cells, macrophages, dendritic cells, mast cells, neutrophils, eosinophils, and basophils. Activated inflammatory cells can express various cytokines and induce an inflammatory response. S. aureus can also induce host cell death through pyroptosis, apoptosis, necroptosis, autophagy, etc. This article discusses S. aureus and MRSA (methicillin-resistant S. aureus) in atopic dermatitis, psoriasis, pulmonary cystic fibrosis, allergic asthma, food poisoning, sarcoidosis, multiple sclerosis, and osteomyelitis. Summarizing the pathogenic mechanism of Staphylococcus aureus provides a basis for the targeted treatment of Staphylococcus aureus infection.

A case report: septic shock due to (tropical) pyomyositis and multiple metastatic embolisms caused by Panton Valentine Leukocidin-positive methicillin-sensitive staphylococcus aureus in a 12-year-old boy

CASE REPORT

A 12-year-old boy, of Congolese roots and without medical history, first presented to our Emergency Department 3 days after blunt trauma of the left ankle. The boy represented on two more occasions in the next 3 days due to ongoing pain. On the last occasion he presented with severe hypoglycaemia. He was diagnosed with severe septic shock, secondary to subperiosteal abscess formation / osteomyelitis of the ankle. The patient was transferred to the paediatric intensive care unit where appropriate medical care was provided, including broad-spectrum antibiotic therapy, high dose vasopressor / inotropic support, surgical debridement of abscesses and below-knee amputation.

PANTON VALENTINE LEUKOCIDIN TOXIN AND PYOMYOSITIS TROPICALIS

The causative organism was a methicillin-susceptible S. aureus, which upon further identification was a carrier of the PVL (Panton Valentine leukocidin) toxin. This pathogen is responsible for severe musculoskeletal infections. In children these infections are often associated with more severe clinical course requiring a higher need for surgical intervention and longer hospital stay.Tropical pyomyositis is a disease caused by Staphylococcus aureus, often seen in tropical countries, and classically presented with muscle abscesses. Young males between the ages of 10-40 years old are the most susceptible, and often present with a history of blunt trauma. Treatment generally requires a combination of an anti-staphylococcal agent, and an anti-toxic agent blocking bacterial protein-synthesis of PVL. Source control by surgical debridement also plays a major role in the treatment of PVL-infection. Despite agressive treatment, mortality still varies from 0.5% to 2%.

Fulminant methicillin-sensitive Staphylococcus aureus infection: from pinprick to multiorgan failure

A woman in her 60s with diabetes presented to our institution with altered mental status. Preceding symptoms included headaches, nausea and vomiting. One month prior to presentation, she cut her left thumb and developed a pustule, which she occasionally manipulated with a non-sterile needle. On arrival, the patient was in shock, with a Glasgow Coma Scale of 3, requiring emergent intubation and intensive care unit admission. Her initial imaging studies revealed a large pericardial effusion and cerebral subcortical hypodensities. She suffered from a cardiopulmonary arrest with return of spontaneous circulation, with bedside echocardiogram revealing cardiac tamponade. She underwent emergent pericardiocentesis which revealed purulent drainage. Blood, pericardial fluid, cerebrospinal fluid, sputum and urine cultures returned positive for methicillin-sensitive Staphylococcus aureus The hospital course was further complicated by refractory septic shock and fulminant multiorgan failure, ultimately leading to her demise.

Septic Arthritis of the Hip in Children: A Critical Analysis Review

Septic arthritis of the hip is a common and potentially devastating condition in children. Septic arthritis is most commonly caused by Staphylococcus aureus, but other pathogens should be considered on the basis of patient age and presence of risk factors. Diagnosis of septic arthritis is based on history and physical examination, laboratory tests, radiographs, ultrasound, and arthrocentesis. Treatment comprises empiric antibiotics and joint debridement, and antibiotics are subsequently tailored on the basis of culture data, local resistance patterns, and clinical response. Late sequelae of septic arthritis include osteonecrosis, chondrolysis, growth disturbance, subluxation or dislocation, and progressive ankylosis. Surgical treatments to address these issues have been described.

Isolation and Molecular Identification of Virulence, Antimicrobial and Heavy Metal Resistance Genes in Livestock-Associated Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is one of the most important pathogens of humans and animals. Livestock production contributes a significant proportion to the South African Gross Domestic Product. Consequently, the aim of this study was to determine for the first time the prevalence, virulence, antibiotic and heavy metal resistance in livestock-associated S. aureus isolated from South African livestock production systems. Microbial phenotypic methods were used to detect the presence of antibiotic and heavy metal resistance. Furthermore, molecular DNA based methods were used to genetically determine virulence as well as antibiotic and heavy metal resistance determinants. Polymerase chain reaction (PCR) confirmed 217 out of 403 (53.8%) isolates to be S. aureus. Kirby-Bauer disc diffusion method was conducted to evaluate antibiotic resistance and 90.8% of S. aureus isolates were found to be resistant to at least three antibiotics, and therefore, classified as multidrug resistant. Of the antibiotics tested, 98% of the isolates demonstrated resistance towards penicillin G. High resistance was shown against different heavy metals, with 90% (196/217), 88% (192/217), 86% (188/217) and 84% (183/217) of the isolates resistant to 1500 µg/mL concentration of Cadmium (Cd), Zinc (Zn), Lead (Pb) and Copper (Cu) respectively. A total of 10 antimicrobial resistance and virulence genetic determinants were screened for all livestock associated S. aureus isolates. Methicillin-resistant S. aureus (MRSA) isolates were identified, by the presence of mecC, in 27% of the isolates with a significant relationship (p < 0.001)) with the host animal. This is the first report of mecC positive LA-MRSA in South Africa and the African continent. The gene for tetracycline resistance (tetK) was the most frequently detected of the screened genes with an overall prevalence of 35% and the highest prevalence percentage was observed for goats (56.76%) followed by avian species (chicken, duck and wild birds) (42.5%). Virulence-associated genes were observed across all animal host species. The study reports the presence of luks/pv, a gene encoding the PVL toxin previously described to be a marker for community acquired-MRSA, suggesting the crossing of species between human and livestock. The high prevalence of S. aureus from the livestock indicates a major food security and healthcare threat. This threat is further compounded by the virulence of the pathogen, which causes numerous clinical manifestations. The phenomenon of co-selection is observed in this study as isolates exhibited resistance to both antibiotics and heavy metals. Further, all the screened antibiotic and heavy metal resistance genes did not correspond with the phenotypic resistance.

The Continuing Threat of Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus has been an exceptionally successful pathogen, which is still relevant in modern age-medicine due to its adaptability and tenacity. This bacterium may be a causative agent in a plethora of infections, owing to its abundance (in the environment and in the normal flora) and the variety of virulence factors that it possesses. Methicillin-resistant S. aureus (MRSA) strains—first described in 1961—are characterized by an altered penicillin-binding protein (PBP2a/c) and resistance to all penicillins, cephalosporins, and carbapenems, which makes the β-lactam armamentarium clinically ineffective. The acquisition of additional resistance determinants further complicates their eradication; therefore, MRSA can be considered as the first representative of multidrug-resistant bacteria. Based on 230 references, the aim of this review is to recap the history, the emergence, and clinical features of various MRSA infections (hospital-, community-, and livestock-associated), and to summarize the current advances regarding MRSA screening, typing, and therapeutic options (including lipoglycopeptides, oxazolidinones, anti-MRSA cephalosporins, novel pleuromutilin-, tetracycline- and quinolone-derivatives, daptomycin, fusidic acid, in addition to drug candidates in the development phase), both for an audience of clinical microbiologists and infectious disease specialists.

Methicillin-resistant Staphylococcus aureus: livestock-associated, antimicrobial, and heavy metal resistance

Staphylococcus aureus is an opportunistic pathogen of human and other mammals that is of increasing clinical and veterinary importance due to its ability to rapidly develop antimicrobial resistance. The injudicious use of antibiotics has given rise to the emergence of antibiotic resistant S. aureus strains, most importantly methicillin-resistant Staphylococcus aureus (MRSA). The emergence of livestock-associated MRSA (LA-MRSA) has highlighted the importance of directed research toward its prevention, as well as the need for the discovery and development of more efficient treatment than is currently available. Furthermore, the treatment of MRSA is complicated by the co-selection of heavy metal and antibiotic resistance genes by microorganisms. Livestock and livestock production systems are large reservoirs of heavy metals due to their use in feed as well as environmental contaminant, which has allowed for the selection of LA-MRSA isolates with heavy metal resistance. The World Health Organization reported that Africa has the largest gaps in data on the prevalence of antimicrobial resistance, with no reports on rates for LA-MRSA harboring heavy metal resistance in South Africa. This review aimed to report the emergence of LA-MRSA in South Africa, specifically the most frequent sequence type ST398, globally. Furthermore, we aimed to highlight the importance of LA-MRSA in clinical and food security, as well as this research gap in South Africa. This review sheds light on the prevalence of heavy metals in livestock farms and abattoirs, and focuses on the phenomenon of the co-selection of heavy metal and antibiotic resistance genes in MRSA, emphasizing the importance of a focused direction for research in humans, animals as well as environment using one-health approach.

Detection and Molecular Characterization of Methicillin-Resistant Staphylococcus aureus from Table Eggs in Haripur, Pakistan

Table eggs are nutritionally important food consumed globally. Despite being protected inside the hard shell and a semipermeable membrane, the egg contents may be contaminated with microbes and thus become a possible carrier of infectious agents to humans. A number of medically significant bacterial species such as Salmonella enterica, Listeria monocytogenes, and Yersinia enterocolitica have already been reported from table eggs. More important is the presence of antimicrobial-resistant bacterial strains in this food source. The present study was aimed at detection and characterization of Staphylococcus aureus from table eggs collected from different retail shops in Haripur city of Pakistan. Staphylococci were isolated from 300 eggs collected from December 2015 to May 2016. S. aureus isolates were tested for antimicrobial susceptibility using broth microdilution and characterized using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing, and spa typing. The presence of Panton-Valentine leukocidin and antimicrobial resistance genes were detected using PCR. Staphylococci were isolated from 21.3% (64/300) of the table eggs tested. Of those, 59% (38/64) were identified as S. aureus, of which 33 (86.8%) were positive for mecA (MRSA, methicillin-resistant S. aureus). All MRSA were multidrug resistant (resistant to two or more antimicrobial classes), contained aac-aph (encoding aminoglycosides), and were pvl⁺. Using MLST, spa typing, and SCCmec typing, three genotypic patterns were assigned: ST8-t8645-MRSA-IV, associated with USA300; and ST772-t657-MRSA-IV and ST772-t8645-MRSA-IV, both characteristic of the Bengal Bay community-associated MRSA clone. Molecular typing by PFGE revealed that the bacterial population was highly homogenous with only two patterns observed. This study is the first report of detection of human-associated pvl⁺ MRSA from table eggs. The genetic similarities of MRSA present in the eggs to that of humans may suggest human to poultry transmission of MRSA via contamination.

Dalbavancin for outpatient parenteral antimicrobial therapy of skin and soft tissue infections in a returning traveller : Proposal for novel treatment indications

Skin and soft tissue infections (SSTIs) are among the most common health problems in travellers returning from tropical and subtropical countries. Importantly, the prevalence of Staphylococcus aureus, the most common pathogen for purulent SSTIs, with specific drug resistance, such as methicillin resistant Staphylococcus aureus (MRSA) and those expressing virulence genes, such as Panton-Valentine-leukocidin is higher in tropical regions than in most high resource settings. This poses challenges for the empirical antimicrobial treatment of SSTIs in returning travellers. This short report describes a patient with a recent travel history to Hong Kong, Singapore and the Philippines who presented with multiple mosquito bites on both upper extremities and secondary bacterial superinfection. He had previously been prescribed oral beta-lactam antimicrobial therapy but lacked adherence to this treatment. Based on the risk for MRSA infection and problems with treatment adherence to oral therapy an outpatient parenteral antimicrobial therapy with dalbavancin was administered on days 0 and 7. Microbiological culture confirmed presence of MRSA and clinical follow-up demonstrated complete remission of the SSTI within 2 weeks. Dalbavancin is a promising treatment option for empirical parenteral treatment of SSTIs in returning travellers, a population at high risk for beta-lactam resistant S. aureus skin infections.

Molecular epidemiology of Panton-Valentine Leukocidin-positive community-acquired methicillin resistant Staphylococcus aureus isolates in pastoral communities of rural south western Uganda

Background

The emergence of multidrug resistant Staphylococcus aureus strains, including methicillin resistant (MRSA), is a global concern. Treatment of bacterial infections in Uganda’s health care settings is largely empirical, rarely accompanied by laboratory confirmation. Here we show the burden, characteristics of MRSA and epidemiology of Panton-Valentine Leukocidin (PVL) positive strains in asymptomatic carriers in pastoral households of south-west Uganda.

Methods

Nasal swabs from 253 participants were cultured following standard methodology. MRSA strains were identified by detection of the mecA gene and SCCmec typing, and PVL genes detected by PCR. Pulsed Field Gel Electrophoresis (PFGE) was done to evaluate possible transmission patterns. Spa typing of PVL positive isolates was done to study the epidemiology of virulent strains in this setting.

Results

S. aureus was isolated in 29% (n = 73) of the participants, of which 48 were MRSA by mecA typing. PVL-encoding genes were found in 49.3% (n = 36) of the 73 isolates, of which 25 were also mecA positive. Among the PVL negative strains (n = 37), 62.2% (n = 23) carried the mecA gene. The most common SCCmec type was V, detected in 39 (18 PVL positive and 21 PVL negative) isolates. PFGE clustered 21/36 (58.3%) PVL positive isolates divided in four pulsotypes and 18/37 (48.6%) PVL negative isolates divided in eight pulsotypes. The most prevalent Spa types were t318 (26.5%, n = 9) and t645 (20.6%, n = 7); while other common Spa types were t11656 (n = 3), t127 (n = 3) and t355 (n = 3).

Conclusion

The study shows a high prevalence of community acquired (CA)-MRSA, and PVL-positive isolates with two predominant spa types in rural Uganda, further complicating infection control strategies in these underprivileged communities.

Seasonal variation of respiratory pathogen colonization in asymptomatic health care professionals: A single-center, cross-sectional, 2-season observational study

BACKGROUND

The purpose of this study was to determine the seasonal variance of potentially pathogenic bacterial and viral organisms in nasopharyngeal specimens obtained from asymptomatic health care professionals (HCPs) during the 2014 winter and summer months.

METHODS

Nasopharyngeal specimens from 100 HCPs were collected from Huntsville Hospital (Huntsville, AL) during the winter and from 100 HCPs during the summer. All subjects were tested for 22 viruses and 19 bacteria using Target Enriched Multiplex Polymerase Chain Reaction. Both seasonal cohorts were composed of students, nurses, physicians, and residents.

RESULTS

Of the 100 HCPs tested during the winter, 34 subjects were colonized with at least 1 bacterium, and 11 tested positive for at least 1 virus. Methicillin-resistant Staphylococcus aureus (MRSA), Moraxella catarrhalis, and coronavirus were the most frequently detected potentially infectious agents. Of the 100 HCPs tested during the summer, 37 tested positive for at least 1 bacterium, and 4 tested positive for a viral agent. The most prevalent bacteria were MRSA and Klebsiella pneumonia.

CONCLUSION

Nasopharyngeal carriage among asymptomatic HCPs was common, but the frequency and presence of potential pathogens varied with each season. Understanding the colonization and infection potential of upper respiratory organisms is important, particularly for viruses. Although asymptomatic HCPs certainly harbor a number of different potentially infectious agents, future studies are needed to determine whether colonized pathogens are transmitted or initiate infection in at-risk patient populations.

Heavy chain-only antibodies and tetravalent bispecific antibody neutralizing Staphylococcus aureus leukotoxins

Panton-Valentine leukocidin (PVL) is a pore-forming toxin associated with current outbreaks of community-associated methicillin-resistant strains and implicated directly in the pathophysiology of Staphylococcus aureus-related diseases. Humanized heavy chain-only antibodies (HCAb) were generated against S. aureus PVL from immunized transgenic mice to neutralize toxin activity. The active form of PVL consists of the two components, LukS-PV and LukF-PV, which induce osmotic lysis following pore formation in host defense cells. One anti-LukS-PV HCAb, three anti-LukF-PV HCAbs with affinities in the nanomolar range, and one engineered tetravalent bispecific HCAb were tested in vitro and in vivo, and all prevented toxin binding and pore formation. Anti-LukS-PV HCAb also binds to γ-hemolysin C (HlgC) and inhibits HlgC/HlgB pore formation. Experiments in vivo in a toxin-induced rabbit endophthalmitis model showed that these HCAbs inhibit inflammatory reactions and tissue destruction, with the tetravalent bispecific HCAb performing best. Our findings show the therapeutic potential of HCAbs, and in particular, bispecific antibodies.

Community-associated methicillin-resistant Staphylococcus aureus (MRSA): an overview for nurses

Upon completion of this activity, the learner will be able to:1. Differentiate between the two types of Methicillin-resistant Staphylococcus aureus (MRSA)--HA-MRSA and CA-MRSA. 2. Describe evidence-based management of MRSA infections. 3. Describe the epidemiology and clinical manifestations of MRSA infections.

Epidemiology of methicillin-susceptible Staphylococcus aureus in a university medical center day care facility

BACKGROUND

Few data are available on methicillin-susceptible Staphylococcus aureus (MSSA) colonization in day care. We performed a study in a child care center on a medical university campus to study the epidemiology of MSSA in this population.

METHODS

A cross-sectional study was done on 104 day care attendees and 32 adult employees of the child care center. Swab samples were taken from the nose, oropharynx, axilla, groin, and perirectal area of children, from the nose and oropharynx of employees, and from the environment. Parents and employees completed questionnaires. Swabs were placed in broth, then plated on agar and identified as MSSA by routine methods. Molecular typing was performed.

RESULTS

The prevalence of MSSA was 21.15% in children and 28.13% in employees. MSSA was found in 8.72% of environmental samples. Univariate analysis identified 3 risk factors and 5 protective factors for MSSA colonization. In multivariable analysis, only 2 variables remained significantly related to MSSA colonization, with older age remaining as a risk factor and receipt of beta-lactams approaching significance as being protective. Many of the isolates were indistinguishable by molecular typing.

CONCLUSIONS

The prevalence of MSSA colonization in children and care providers in a university medical center child care center is similar to that of the general population. Children colonized with MSSA tended to be older and to have received fewer courses of antibiotics than children who did not have MSSA. The relatedness of many of the isolates indicates that transmission of MSSA occurred at this child care center.

Familial furunculosis associated with community-acquired leukocidin-positive methicillin-susceptible Staphylococcus aureus ST152

Panton-Valentine leukocidin (PVL) is associated with staphylococcal skin and pulmonary infections. Community dissemination of PVL-producing Staphylococcus aureus strains constitutes a public health concern. Family transmission and spread of community-acquired leukocidin-positive methicillin-susceptible S. aureus ST152 isolates associated with severe clinical symptoms are herein described. Remarkably, ST152 isolates usually are methicillin resistant.