Panton-Valentine Leukocidin Positive Isolates Research Articles

Pediatric Community-Acquired Bone and Joint Staphylococcus Aureus Infections In Europe: Severe Infections are Associated to Panton-Valentine Leucocidin Presence.

To analyze host and pathogen factors related to disease severity of community-acquired bone and joint infections in children, a cohort of pediatric patients was prospectively recruited from 13 centers in 7 European countries. A total of 85 children were included, 11 (13%) had a severe infection. Panton-Valentine leukocidin-positive isolates were 17%, and 6% of the isolates were methicillin-resistant Staphylococcus aureus. Multivariate analysis identified Panton-Valentine leukocidin presence (adjusted odds ratio, 12.6; P = 0.01) as the only factor independently associated with severe outcome, regardless of methicillin resistance.

Molecular Epidemiology of Panton-Valentine Leukocidin Harboring Hospital-Associated Methicillin-Resistant Staphylococcus aureus in Septicemic Children, Northeastern Iran, Bojnurd

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for an increasing number of serious hospital- and community-acquired infections in adults and children. Sepsis caused by S. aureus is one of the major health problems associated with treatment failure in adults; however, its clinical outcomes, the rate of treatment failure, and its molecular epidemiology are poorly understood. Objectives: The objective of this study was to evaluate the molecular epidemiology of Panton-Valentine Leukocidin (PVL) harboring MRSA strains isolated from children's blood culture in Bojnurd. Methods: Totally, 58 S. aureus strains were isolated from blood cultures in the major teaching hospital in Bojnurd. After the primary verification of Methicillin resistance by agar screening method, the isolated MRSA strains were confirmed with the detection of the mecA gene. MecA-positive strains evaluated for SCCmec, agr, and toxin profiles. Panton-valentine leucocidin-positive isolates were subjected to be evaluated for spa and sequence type (ST). Results: Our data indicated 53.4% (31) of isolates were MRSA. Twelve (38.7%) of these isolates had PVL gene that 25% (3) of them had tsst-1 gene and 58.3% (7) had etb gene. One (3.2%), 64.5% (20), and 32.2% (10) of these isolates belonged to SCCmec I, III, and IV, respectively. Predominant ST and spa types among PVL positive isolates were ST6 and t304, respectively. Conclusions: We had an uncommon finding because PVL was routinely found in community-acquired MRSA, but in this study we found PVL harboring hospital-associated MRSAs. A notable point about these isolates is that most of them belonged to Asian endemic clones.

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

BackgroundThe 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.MethodsNasal 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.ResultsS. 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).ConclusionThe 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.

Detection of Panton-valentine Leukocidin Gene Isoforms of Staphylococcus aureus Isolates in Al-Zahra Hospital, Isfahan-Iran.

Background:Panton-Valentine leukocidin (PVL) is a gamma-toxin produced by Staphylococcus aureus encoded by genes lukS/lukF-PV with several single-nucleotide polymorphisms. A mutation at nucleotide position 527 results in substitution of histidine (H) to arginine (R) at amino acid 176. The groups defined based on the amino acid change, the “R isoform” group and the “H isoform” group. The purpose of this study was to determine the frequency of PVL gene isoforms in S. aureus strains isolated from patients at Al-Zahra Hospital Isfahan and molecular characterization of PVL-positive methicillin-resistant S. aureus (MRSA) strains including the detection of mecA gene and staphylococcal chromosomal cassette mec (SCCmec) typing.Materials and Methods:In this study, 130 isolates of S. aureus were collected from Al-Zahra Hospital. The PVL gene identified using polymerase chain reaction (PCR); PCR products were sequenced to identify the type of isoform. The molecular characterization of isolates of PVL-positive MRSA including detection of mecA gene by PCR and also SCCmec typing was performed by multiplex PCR.Results:Out of 130 isolates, 23% were positive for the presence of PVL genes. The PVL positive isolates were comprised 37% (11/30) of methicillin-resistant isolates and 63% (19/30) of methicillin-susceptible S. aureus (MSSA) isolates. The results showed that 17 isolated carrying isoform H and 13 isolated carrying the R isoform.Conclusion:The PVL gene was predominantly found in MSSA isolates. There was no relation between PVL isoforms and the presence of mecA and SCCmec types.

Molecular Characterization and Antimicrobial Susceptibility of Staphylococcus aureus Isolates from Clinical Infection and Asymptomatic Carriers in Southwest Nigeria.

Few reports from Africa suggest that resistance pattern, virulence factors and genotypes differ between Staphylococcus aureus from nasal carriage and clinical infection. We therefore compared antimicrobial resistance, selected virulence factors and genotypes of S. aureus from nasal carriage and clinical infection in Southwest Nigeria. Non-duplicate S. aureus isolates were obtained from infection (n = 217) and asymptomatic carriers (n = 73) during a cross sectional study in Lagos and Ogun States, Nigeria from 2010–2011. Susceptibility testing was performed using Vitek automated systems. Selected virulence factors were detected by PCR. The population structure was assessed using spa typing. The spa clonal complexes (spa-CC) were deduced using the Based Upon Repeat Pattern algorithm (BURP). Resistance was higher for aminoglycosides in clinical isolates while resistances to quinolones and tetracycline were more prevalent in carrier isolates. The Panton-Valentine leukocidin (PVL) was more frequently detected in isolates from infection compared to carriage (80.2 vs 53.4%; p<0.001, chi2-test). Seven methicillin resistant S. aureus isolates were associated with spa types t002, t008, t064, t194, t8439, t8440 and t8441. The predominant spa types among the methicillin-susceptible S. aureus isolates were t084 (65.5%), t2304 (4.4%) and t8435 (4.1%). spa-CC 084 was predominant among isolates from infection (80.3%, n = 167) and was significantly associated with PVL (OR = 7.1, 95%CI: 3.9–13.2, p<0.001, chi2- test). In conclusion, PVL positive isolates were more frequently detected among isolates from infection compared to carriage and are associated with spa-CC 084.

Co-detection of Panton-Valentine leukocidin encoding genes and cotrimoxazole resistance in Staphylococcus aureus in Gabon: implications for HIV-patients' care.

Patients infected with the human immunodeficiency virus (HIV) are frequently exposed to antimicrobial agents. This might have an impact on the resistance profile, genetic background and virulence factors of colonizing Staphylococcus aureus. Sub-Saharan Africa is considered to be endemic for Panton-Valentine leukocidin (PVL) positive S. aureus which can be associated with skin and soft tissue infections (SSTI). We compared S. aureus from nasal and pharyngeal swabs from HIV patients (n = 141) and healthy controls (n = 206) in Gabon in 2013, and analyzed determinants of colonization with PVL positive isolates in a cross-sectional study. S. aureus isolates were screened for the presence of selected virulence factors (incl. PVL) and were subjected to antimicrobial susceptibility testing and genotyping. In HIV patients, S. aureus was more frequently detected (36.9 vs. 31.6%) and the isolates were more frequently PVL positive than in healthy controls (42.1 vs. 23.2%). The presence of PVL was associated with cotrimoxazole resistance (OR = 25.1, p < 0.001) and the use of cotrimoxazole was a risk factor for colonization with PVL positive isolates (OR = 2.5, p = 0.06). PVL positive isolates were associated with the multilocus sequence types ST15 (OR = 5.6, p < 0.001) and ST152 (OR = 62.1, p < 0.001). Participants colonized with PVL positive isolates reported more frequently SSTI in the past compared to carriers of PVL negative isolates (OR = 2.7, p = 0.01). In conclusion, the novelty of our study is that cotrimoxazole might increase the risk of SSTI in regions where cotrimoxazole resistance is high and associated with PVL. This finding needs to be confirmed in prospective studies.

Antimicrobial susceptibility and molecular typing of MRSA in cystic fibrosis

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in cystic fibrosis (CF) patients in the United States is approximately 25%. Little is known about the relative proportion of hospital- versus community-associated strains or the antimicrobial susceptibility of MRSA in different CF centers. We hypothesized that the majority of MRSA isolates obtained from children with CF are those endemic in the hospital and that those associated with community acquisition (SCCmec IV) would be more resistant than typically seen in non-CF MRSA isolates. We studied MRSA strains from seven pediatric CF centers to determine the clonal distribution based on DNA sequencing of the staphylococcal protein A gene (spa typing), the type of staphylococcal chromosomal cassette mec (SCCmec), and the proportion of strains with Panton-Valentine leukocidin (PVL). Antimicrobial susceptibility to systemic and topical antibiotics was compared between different MRSA types. We analyzed 277 MRSA isolates from unique patients (mean age 11.15 ± 4.77 years, 55% male). Seventy % of isolates were SCCmec II PVL negative and the remainder SCCmec IV. Overall 17% MRSA strains were PVL positive (all SCCmec IV). Spa typing of 118 isolates showed most of the SCCmec II strains being t002, while SCCmec IV PVL positive isolates were t008, and SCCmec IV PVL negative isolates represented a variety of spa-types. The proportions of SCCmec II strains and spa-types were similar among centers. Overall rates of resistance to trimethoprim-sulfamethoxazole (4%), tetracycline (7%), tigecycline (0.4%), linezolid (0.4%) as well as fosfomycin (0.4%), fusidic acid (3%), and mupirocin (1%) were low. No strains were resistant to vancomycin. SCCmec II strains had higher rates of resistance to ciprofloxacin and clindamycin (P < 0.001) than SCCmec IV strains. In this U.S. study, most MRSA isolates in the pediatric CF population were SCCmec II PVL negative. Rates of resistance were low, including to older and orally available antibiotics such as trimethoprim-sulfamethoxazole.

Investigation of Panton-Valentine leukocidin expressing Staphylococcus aureus colonization among children in a child care center

The presence of Panton-Valentine leukocidin expressing Staphylococcus aureus colonization was investigated with a qualitative nucleic acid hybridization assay among 122 children and 19 staff in a child care center. Genotyping of 5 Panton-Valentine leukocidin-positive isolates by pulsed-field gel electrophoresis revealed that one child and a teacher from the same class were colonized with the clonally related strains. This finding allowed us to suggest that close contact with colonized people is a risk factor for being colonized.

Molecular typing of methicillin-susceptible Staphylococcus aureus isolates collected in the Yogyakarta area in Indonesia, 2006

The characterization of 62 community-associated methicillin-sensitive Staphylococcus aureus (MSSA) isolates from 440 individuals in the Yogyakarta area of Indonesia in 2006 showed that: (i) almost half of the isolates were associated with methicillin-resistant S. aureus lineages [clonal complex (CC)1, CC8 and CC45] and (ii) ten Panton–Valentine leukocidin-positive isolates were associated with CC1 (n = 7), CC30 (n = 1) and CC51 (n = 2). The high Panton–Valentine leukocidin prevalence (16%) among S. aureus is of concern because these strains can cause severe infections and the introduction of staphylococcal cassette chromosome mec into virulent and epidemic MSSA could pose a serious public health threat.

Panton-Valentine Leukocidin Positive Methicillin Resistant S. Aureus Infections in Children with Cancer

Background: Staphylococcus aureus is one of the most prevalent organisms isolated from children and adults with cancer. Strains of methicillin resistant S. aureus (MRSA) have emerged in the past decade, that often cause serious infections, in young, otherwise healthy people. Suppurative skin infections and necrotizing pneumonias are some of the diseases most characteristically associated with these new strains. Such MRSA isolates often harbor the Panton-Valentine Leukocidin (PVL) gene, belong to pulsed-field type USA 300, carry the staphylococcal cassette chromosome (SCC) mec IV, and are susceptible to clindamycin. The presence of the PVL gene has been associated with increased virulence and morbidity in these patients. However, the role of these new MRSA strains in causing infections in children and adults with cancer is presently unknown. Studies are needed to determine if the increase in incidence of MRSA infections in the community is paralleled by an increase in MRSA infections in pediatric cancer patients and if infections with these new strains are more virulent in this population.Methods: The present work represents a retrospective study of all children with cancer diagnosed with MRSA infection over an eight year period from January 2000 to December 2007. Medical record review included patient demographics, underlying disease, and antimicrobial susceptibility patterns of MRSA isolates. Genotyping of isolates was performed using PCR for detection of the PVL gene. SCC mec and spa typing was performed on all PVL positive isolates. Logistic regression models were used to study the trend in the increase of MRSA infection over time. Statistical analysis was performed on frequency data between the different categorical variables among the PVL positive and PVL negative MRSA isolates by the Exact Pearson Chi-square test.Results: A total of 98 clinical MRSA isolates were collected from 88 children with cancer from Jan 2000 to Dec 2007. The number of MRSA isolates increased sevenfold from 3 in 2000 to 21 in 2006 (p<0.0001). During the same period there was a significant decrease in the incidence of methicillin-sensitive S. aureus (MSSA) isolates (p<0.0001). Ten of the children had recurrent infection. The increase in MRSA infections was predominantly due to an increase in skin and soft tissue infections (p=0.0004). Children with African American ancestry and inpatients were significantly overrepresented in having MRSA infection as compared to other children with cancer (p<0.0001). Outcome was generally favorable; 33% had fever and only 10 patients (10%) had complications. Resistance to ciprofloxacin, clindamycin, erythromycin, gentamicin and mupirocin was 23%, 20%, 80%, 5%, and 2% respectively. All the isolates were sensitive to trimethoprim-sulfamethoxazole and vancomycin. PVL positive isolates bearing the SCC mec IV element comprised 35 of 98 (36%) of MRSA isolates. 32 of the 35 isolates belonged to the USA 300 type. No child had a recurrent infection with a PVL positive strain. Children infected with PVL positive strains had a significantly higher incidence of skin and soft tissue infections (SSTI, p=0.045), and bacteremia (p=0.045), as compared to children with PVL negative strains. A significantly higher number of the PVL positive isolates were susceptible to clindamycin (p=0.0158) and ciprofloxacin (p=0.0045).Conclusion: This report represents the first description of the changing epidemiology of MRSA infections in children with cancer. The association between PVL positive MRSA infections and bacteremia is a novel finding in this population. PVL positive MRSA infections caused low morbidity and mortality in these immune-suppressed patients. Future studies may determine if patients with colonization from these virulent strains may benefit from preemptive therapy with mupirocin, to eradicate colonization. This approach may reduce the risk of bacteremia in high risk groups such as patients undergoing hematopoietic stem cell transplantation prior to engraftment.

Community-acquired methicillin-resistant Staphylococcus aureus in Madrid, Spain: transcontinental importation and polyclonal emergence of Panton–Valentine leukocidin-positive isolates

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates producing the Panton–Valentine leukocidin (PVL) have been reported worldwide. We describe the molecular characteristics of PVL-positive CA-MRSA strains isolated in Madrid, Spain, and analyze the clinical features of patients infected with these isolates. From 2004 to 2007, we collected 13 PVL-positive MRSA isolates from patients attending to the emergency department. The isolates were genotyped by pulsed-field gel electrophoresis, SCC mec typing, agr polymorphism, and multilocus sequence typing. Susceptibility to 29 antimicrobials was determined by the broth microdilution and by the E-test methods. The isolates belonged to 3 genotypes: ST8-SCC mec IVc ( n = 11), ST5-SCC mec IVa ( n = 1), and ST80-SCC mec IVc ( n = 1). The corresponding agr types were I, II, and III, respectively. Five isolates were resistant to tetracycline and doxycycline, and 1 was resistant to fusidic acid (ST80). The isolates were from children ( n = 9) and adults ( n = 4), and were associated with skin and soft tissue infections ( n = 9), otitis ( n = 1), and bacteremia ( n = 1). Nine patients were from South America. Our results indicate the transcontinental importation and recent emergence in Spain of PVL-positive CA-MRSA strains belonging to 3 distinct lineages, including 1 predominant (ST8-SCC mec IVc).

Multiple Abszesse bei immunkompetenten Patienten durch Panton-Valentin-Leukozidin-positiven Staphylococcus aureus

We report cases of immunocompetent patients showing multiple abscesses by a Panton-Valentine leukocidin (PVL) positive Staphylococcus aureus. PVL is considered to be an important virulence factor. The most common manifestations by this pathogen are recurrent or multiple abscesses of the skin. Seldom necrotizing pneumonia with high mortality occurs. Even methicillin-resistant PVL positive isolates have been identified in Germany. Only appropriate infection control measures in combination with antimicrobial therapy resulted in successful eradication of this pathogen. Dermatologists should be informed about this specific type of infection and about the appropriate infection control measures.

Establishment of ST30 as the Predominant Clonal Type among Community-Associated Methicillin-Resistant Staphylococcus aureus Isolates in Singapore

The number of infections attributable to community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Singapore is progressively increasing. Most cases in the past 2 years were caused by Panton-Valentine leukocidin-positive isolates belonging to sequence type 30, according to multilocus sequence typing. This has clearly become the predominant sequence type among CA-MRSA isolates in Singapore.