Characterisation of virulence genes in methicillin susceptible and resistant Staphylococcus aureus isolates from a paediatric population in a university hospital of Medellín, Colombia

Virulence and antibiotic resistance are significant determinants of the types of infections caused by Staphylococcus aureus and paediatric groups remain among the most commonly affected populations. The goal of this study was to characterise virulence genes of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains isolated from a paediatric population of a Colombian University Hospital during 2009. Sixty MSSA and MRSA isolates were obtained from paediatric patients between zero-14 years. We identified the genes encoding virulence factors, which included Panton-Valentine leucocidine (PVL), staphylococcal enterotoxins A-E, exfoliative toxins A and B and toxic shock syndrome toxin 1. Typing of the staphylococcal chromosome cassette mec (SCCmec) was performed in MRSA strains. The virulence genes were more diverse and frequent in MSSA than in MRSA isolates (83% vs. 73%). MRSA strains harboured SCCmec types IVc (60%), I (30%), IVa (7%) and V (3%). SCCmec type IVc isolates frequently carried the PVL encoding genes and harboured virulence determinants resembling susceptible strains while SCCmec type I isolates were often negative. PVL was not exclusive to skin and soft tissue infections. As previously suggested, these differences in the distribution of virulence factor genes may be due to the fitness cost associated with methicillin resistance.     

Occurrence of virulence factors among human intestinal enterococcal isolates

AIMS: The aim of this study was to investigate the frequency of enterococcal virulence factors among human intestinal Enterococcus faecalis strains and to find out whether the pattern differs from that seen in published reports on food and clinical isolates. METHODS AND RESULTS: The E. faecalis isolates were cultured from human faecal samples obtained from five ulcerative colitis patients in remission phase. The species identification was based on API120 strips and species-specific PCR primers. The isolates were further characterized using the pulsed-field gel electrophoresis. The presence of seven different known enterococcal virulence factors among the confirmed E. faecalis isolates were screened using PCR techniques and published primers. CONCLUSIONS: Among the 35 isolates representing nine different pulsotypes the most frequent virulence factors were cpd (33 isolates), agg (25 isolates), gelE (22 isolates) and esp (15 isolates). No complete sets of genes associated for the production of functional cytolysin were encountered indicating that intestinal enterococci may differ in this respect from clinical strains. SIGNIFICANCE AND IMPACT OF THE STUDY: According to the results, the commensal enterococcal strains appear to differ from clinical isolates in their complement of presumed virulence factors.     

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, chi^2- test). In conclusion, PVL positive isolates were more frequently detected among isolates from infection compared to carriage and are associated with spa-CC 084.     

Panton-Valentine leukocidin is not the primary determinant of outcome for Staphylococcus aureus skin infections: evaluation from the CANVAS studies

The impact of Panton-Valentine leukocidin (PVL) on the severity of complicated skin and skin structure infections (cSSSI) caused by Staphylococcus aureus is controversial. We evaluated potential associations between clinical outcome and PVL presence in both methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) isolates from patients enrolled in two large, multinational phase three clinical trials assessing ceftaroline fosamil for the treatment of cSSSI (the CANVAS 1 and 2 programs). Isolates from all microbiologically evaluable patients with monomicrobial MRSA or MSSA infections (n?=?473) were genotyped by PCR for pvl and underwent pulsed-field gel electrophoresis (PFGE). Genes encoding pvl were present in 266/473 (56.2%) isolates. Infections caused by pvl-positive S. aureus were associated with younger patient age, North American acquisition, and presence of major abscesses (P<0.001 for each). Cure rates of patients infected with pvl-positive and pvl-negative S. aureus were similar overall (93.6% versus 92.8%; P?=?0.72), and within MRSA-infected (94.5% vs. 93.1%; P?=?0.67) and MSSA-infected patients (92.2% vs. 92.7%; P?=?1.00). This finding persisted after adjustment for multiple patient characteristics. Outcomes were also similar when USA300 PVL+ and non-USA300 PVL+ infections were compared. The results of this contemporary, international study suggest that pvl presence was not the primary determinant of outcome in patients with cSSSI due to either MRSA or MSSA.     

Capsular serotype of Staphylococcus aureus in the era of community-acquired MRSA

Capsular polysaccharide (CP) plays an important role in the pathogenicity and immunogenicity of Staphylococcus aureus, yet the common serotypes of S. aureus isolated from US pediatric patients have not been reported. We investigated capsular serotype as well as methicillin susceptibility, presence of Panton-Valentine leukocidin (PVL), and clonal relatedness of pediatric S. aureus isolates. Clinical isolates were tested for methicillin susceptibility, presence of mecA, lukS-PV and lukF-PV, cap5 and cap8 genes by PCR, and for capsular or surface polysaccharide expression (CP5, CP8, or 336 polysaccharide) by agglutination. Genetic relatedness was determined by pulsed-field gel electrophoresis. All S. aureus isolates encoded cap5 or cap8. Sixty-nine percent of 2004-2005 isolates were methicillin-susceptible (MSSA) and most expressed a detectable capsule. The majority of MRSA isolates (82%) were unencapsulated, exposing an expressed cell wall techoic acid antigen 336. Pulsed-field type USA300 were MRSA, PVL-positive, unencapsulated strains that were associated with deep skin infections and recurrent disease. Over half (58%) of all isolates from invasive pediatric dermatologic infections were USA300. All pediatric isolates contained either capsule type 5 or capsule type 8 genes, and roughly half of the S. aureus clinical disease isolates from our population were diverse MSSA-encapsulated strains. The majority of the remaining pediatric clinical disease isolates were unencapsulated serotype 336 strains of the PVL(+) USA300 community-associated-MRSA clone.     

Differential pathogenesis of primary CCR5-using human immunodeficiency virus type 1 isolates in ex vivo human lymphoid tissue

In the course of human immunodeficiency virus (HIV) disease, CCR5-utilizing HIV type 1 (HIV-1) variants (R5), which typically transmit infection and dominate its early stages, persist in approximately half of the infected individuals (nonswitch virus patients), while in the other half (switch virus patients), viruses using CXCR4 (X4 or R5X4) emerge, leading to rapid disease progression. Here, we used a system of ex vivo tonsillar tissue to compare the pathogeneses of sequential primary R5 HIV-1 isolates from patients in these two categories. The absolute replicative capacities of HIV-1 isolates seemed to be controlled by tissue factors. In contrast, the replication level hierarchy among sequential isolates and the levels of CCR5(+) CD4(+) T-cell depletion caused by the R5 isolates seemed to be controlled by viral factors. R5 viruses isolated from nonswitch virus patients depleted more target cells than R5 viruses isolated from switch virus patients. The high depletion of CCR5(+) cells by HIV-1 isolates from nonswitch virus patients may explain the steady decline of CD4(+) T cells in patients with continuous dominance of R5 HIV-1. The level of R5 pathogenicity, as measured in ex vivo lymphoid tissue, may have a predictive value reflecting whether, in an infected individual, X4 HIV-1 will eventually dominate.     

Application of optical coherence tomography enhances reproducibility of arthroscopic evaluation of equine joints

Background

Staphylococcus aureus is an important cause of clinical mastitis in dairy cows worldwide. The cure rate after antimicrobial treatment of clinical S. aureus mastitis is very variable due to both cow and bacterial factors. Studies have shown that bacterial genotype might affect short-term bacteriological and clinical cure, but the long-term outcome has been less studied. The objectives of this study were to investigate associations between bacterial genotype and long-term outcome of veterinary-treated clinical mastitis (VTCM) caused by S. aureus during a follow-up period of 120 days and to study genotype variation among Swedish S. aureus isolates. S. aureus isolates from cases of VTCM were genotyped by pulsed-field gel electrophoresis. Long-term outcome measurements used were somatic cell count (SCC), additional diagnoses of VTCM, milk yield and culling. Isolates were classified into clusters (>80% similarity) and pulsotypes (100% similarity). Clusters and pulsotypes were grouped according to occurrence. Multivariable mixed-effect linear regression models including cow and bacterial factors with possible influence on SCC or milk yield were used to calculate differences in SCC or milk yield between groups. Additional outcome measures were calculated using a test of proportions.

Results

The isolates (n?=?185) were divided into 18 clusters and 29 pulsotypes. Two pulsotypes were classified as common, and were found in 64% of the cases of VTCM. Remaining isolates were classified as less common or rare pulsotypes. The distribution was similar at cluster level. Outcome was calculated from follow-up data on 111 cows. Significantly lower SCC during the follow-up period was found in cows infected with common clusters compared to in cows infected with less common/rare clusters. The proportion of cows with SCC <200 000 cells/ml during the whole follow-up period was significantly higher in the group common clusters than in the group less common/rare clusters. Bacterial genotype did not influence the other outcome parameters.

Conclusions

In Sweden, two S. aureus pulsotypes, identified in about 64% of clinical S. aureus cases, were widespread. Cows infected with the common genotypes had significantly lower SCC during 120 days after treatment compared to cows infected with less common or rare genotypes.     

Human immunodeficiency virus type 1 induces apoptosis in CD4(+) but not in CD8(+) T cells in ex vivo-infected human lymphoid tissue

Progression of human immunodeficiency virus (HIV) disease is associated with massive death of CD4(+) T cells along with death and/or dysfunction of CD8(+) T cells. In vivo, both HIV infection per se and host factors may contribute to the death and/or dysfunction of CD4(+) and CD8(+) T cells. Progression of HIV disease is often characterized by a switch from R5 to X4 HIV type 1 (HIV-1) variants. In human lymphoid tissues ex vivo, it was shown that HIV infection is sufficient for CD4(+) T-cell depletion. Here we address the question of whether infection of human lymphoid tissue ex vivo with prototypic R5 or X4 HIV variants also depletes or impairs CD8(+) T cells. We report that whereas productive infection of lymphoid tissue ex vivo with R5 and X4 HIV-1 isolates induced apoptosis in CD4(+) T cells, neither viral isolate induced apoptosis in CD8(+) T cells. Moreover, in both infected and control tissues we found similar numbers of CD8(+) T cells and similar production of cytokines by these cells in response to phorbol myristate acetate or anti-CD3-anti-CD28 stimulation. Thus, whereas HIV-1 infection per se in human lymphoid tissue is sufficient to trigger apoptosis in CD4(+) T cells, the death of CD8(+) T cells apparently requires additional factors.     

Virulence properties of uropathogenic <Emphasis Type="Italic">Escherichia coli</Emphasis> isolated from children with urinary tract infection in Korea

Urinary tract infections (UTIs) are one of the most common types of bacterial infection in humans in various parts of the world and are caused mainly by uropathogenic Escherichia coli (UPEC). A total of 58 UPEC isolates from urine were characterized by serotyping and pulsed-field gel electrophoresis (PFGE). The majority of the UPEC strains belonged to serogroups O2 and O6. The UPEC strains were grouped under different pulsotypes and majority of them belonged to serogroups O2 and O6. Among the 14 virulence factors considered, 13 were present in various serogroups. The virulence genes fimH and sfa were present in all the isolates while none of the isolates carried lt-1. The strains exhibited 36 different virulence patterns, of which 11, referred to as UP (UPEC pattern) 1 to UP 11 were most common. Antibiotic resistance profiling of the UPEC isolates revealed that the serogroups O2 and O6 contain the highest number of resistant strains. The data from the current study depicting the distribution of UPEC strains among various serogroups and pulsotypes, and the occurrence of virulence genes and antibiotics resistance offer useful information on the epidemiological features of UPEC in Korea for the enhanced surveillance of potential emergence of UPEC.     

Molecular analysis and antimicrobial susceptibility of methicillin resistant Staphylococcus aureus in one of the hospitals of Tehran University of Medical Sciences: high prevalence of sequence type 239 (ST239) clone

Methicillin-resistant Staphylococcus aureus (MRSA), particularly the multidrug-resistant clones, is an increasing worldwide problem. The average incidence rate of MRSA in Tehran was found to be over 40%. A total of 140 MRSA isolates obtained from patients attending a teaching hospital in Tehran, from May 2009 to December 2009, were included in this study. The antimicrobial susceptibility profile of MRSA isolates was determined by the agar disk diffusion method. Molecular analysis of MRSA strains was accomplished by Pulsed-Field Gel Electrophoresis (PFGE) and Multi-locus sequence typing (MLST). Detection of mecA gene was used to confirm resistance to methicillin among the MRSA isolates. All the MRSA isolates were susceptible to chloramphenicol, teicoplanin, tigecycline and vancomycin. All MRSAisolates were resistant to oxacillin, whilst 139 strains showed resistance against ciprofloxacin, erythromycin, gentamicin, tetracycline and trimethoprim-sulfamethoxazole. PFGE analysis of all the 140 MRSA isolates produced five distinct pulsotypes designated as pulsotypes A-E. Most of the isolates (n=132) were clustered into pulsotype A. The most prevalent sequence type (ST) was ST 239 (pulsotype A) found in 82% (37/45) of the tested isolates. The second most prevalent type was ST 1238 (pulsotypes B, C and D) found in 15% (7/45) of the isolates. The remaining type, ST 8 (pulsotype E) was found in a single isolate. The results of this study indicated that the MRSA clone ST 239 was a major clone in the selected university hospital of Tehran and that it was widely spread among the different wards as well as all the age groups of patients.     

Isolation of CD4-independent primary human immunodeficiency virus type 1 isolates that are syncytium inducing and acutely cytopathic for CD8+ lymphocytes

Previous studies have established the existence of CD4-independent simian immunodeficiency virus, human immunodeficiency virus type 2 (HIV-2), and laboratory strains of HIV-1. However, whether CD4-independent viruses may also exist in HIV-1-infected patients has remained unclear. We have recently reported the isolation of viruses from an AIDS patient that were able to infect CD8(+) cells independent of CD4, using CD8 as a receptor. Using a similar approach, here we examined viruses from 12 randomly selected patients (obtained from the AIDS Research and Reference Program, National Institutes of Health) for the presence of CD4-independent HIV-1. CD4-independent variants were isolated from infected CD8(+) cells from the viral quasispecies of 7 of 12 patients. The CD4-independent isolates were able to infect primary CD8(+) cells as well as a CD4(-) CD8(+) T-cell line. Soluble CD4 and blocking anti-CD4 or -CD8 antibody had no effect on infection of CD8(+) cells. Remarkably, two of the seven CD4-independent isolates, but not their parental bulk viruses, induced syncytia and caused acute death of infected CD8(+) cells. Some of the CD4-independent variants were also able to infect U87 cells that were negative for CD4, CD8, and common HIV coreceptors, suggesting a novel entry mechanism for these isolates. The CD4-independent isolates were derived from adults and children infected with subtypes A, B, and D. Although no common motif for CD4 independence was found, novel sequence changes were observed in critical areas of the envelopes of the CD4-independent viruses. These results demonstrate that HIV-1-infected patients can frequently harbor viruses that are able to mediate CD4-independent infection of CD8(+) cells. In addition, this study also provides evidence of primary HIV-1 variants that are syncytium inducing and acutely cytopathic for CD8(+) lymphocytes.     

Risk factors for male to female transmission of HIV. European Study Group.

OBJECTIVE--To identify risk factors for sexual transmission of HIV from infected men to their female sexual partners. DESIGN--Cross sectional analysis as part of a continuing study. Data were obtained by interviewing heterosexual couples in which the man was infected with HIV. Risks were assessed by comparing couples in which transmission had occurred (woman infected with HIV) with those in which it had not (woman not infected) and estimated by independent odds ratios and their 95% confidence intervals. SETTING--Infectious disease and public health departments from nine centres in six European countries. PARTICIPANTS--153 Male index patients (mean age 30.4 years) and their 155 female partners (mean age 27.8 years). INTERVENTIONS--Women were tested to determine their HIV antibody state. Women with a risk of infection with HIV other than sexual contact with their infected partner were excluded. END POINT--Three risk factors for male to female transmission of HIV. MEASUREMENTS AND MAIN RESULTS--Three risk factors were identified: a history of sexually transmitted disease in the previous five years for the female partner (odds ratio 3.1, 95% confidence interval 1.1 to 8.6); index patient with full blown AIDS (5.4, 1.2 to 25.2); and practice of anal intercourse (5.8, 2.3 to 14.8). The proportion of women positive for HIV antibody was 27% (42/155), ranging from 7% (1 to 13%) (4/60) for couples with none of the three risk factors to 67% (45 to 89%) (12/18) for those with two or three of the risk factors. Duration of the relationship (median three years), frequency of sexual contacts, sexual practices other than anal intercourse, and contraceptive behaviour were not associated with infection of the partner. CONCLUSIONS--The risk of sexual transmission of HIV from an infected man to his female partner varies considerably according to the characteristics of the couple. The differences in rates of transmission in high risk groups may be considerably reduced if the risk factors are taken into account during individual and public health counselling.     

Characterization of Virulence Factors and Genetic Background of Staphylococcus aureus Isolated from Peking University People’s Hospital Between 2005 and 2009

The aim of this study was to investigate both the genetic features of MRSA strains and the occurrence of virulence factors produced by Staphylococcus aureus strains isolated from Peking University People’s Hospital in Beijing, China, between 2005 and 2009. A total of 179 S. aureus strains were isolated, 139 of which were MRSA. The MRSA strains were characterized epidemiologically by SCCmec typing, spa typing and agr typing, then were classified into different genetic groups. The prevalence of genes coding for 14 exotoxins and eight adhesion factors among the S. aureus samples was assessed via polymerase chain reaction. Cluster analysis based on virulence factors-encoding gene content was performed to divide the MRSA isolates into valid clusters. Correspondence analysis was done to analyze the correlation between virulence factors clusters and genetic groups. JCSC1716-agrI-t030 (67.6%), SCCmec-IIIA-agrI-t030 (14.4%), SCCmec-IIIA-agrI-t037 (8.6%) and SCCmecII-agrII-t002 (2.2%) were four predominant MRSA clones. PVL was positive only in MSSA strains, there were at least three superantigenic toxins in our HA-MRSA clones, the prevalence of 16 virulence factors genes (sea, seb, sec, sed, seg, sei, sej, pvl, lukE-lukD, eta, bbp, can, ebp, clfA, fib, fnbB) in MRSA and MSSA was found to be significantly different from MSSA (P < 0.05). Results of correspondence analysis among clusters based on virulence factors genes and groups based on genetic typing illustrated not only the correspondence relationship between groups and clusters overall (P < 0.001), but also the genetic diversity of MRSA strains with respect to virulence factors genes.     

Relatedness of Listeria monocytogenes Isolates recovered from selected ready-to-eat foods and listeriosis patients in the United States

Pulsed-field gel electrophoresis and serotyping were performed for 544 isolates of Listeria monocytogenes, including 502 isolates recovered from contaminated samples from 31,705 retail ready-to-eat (RTE) food products and 42 isolates recovered from human cases of listeriosis. The isolates were from Maryland (294 isolates) and California (250 isolates) and were collected in 2000 and 2001. The isolates were placed into 16 AscI pulsogroups (level of relatedness within each group, > or =66%), 139 AscI pulsotypes (levels of relatedness, > or =25% to 100%), and eight serotypes (serotypes 1/2a, 1/2b, 1/2c, 3a, 3b, 4b, 4c, and 4d). The most frequently found pulsotypes belonged to either pulsogroup A (150 food isolates plus 4 clinical isolates) or pulsogroup B (104 food isolates plus 5 clinical isolates). The majority of the 502 food isolates were either serotype 1/2a (298 isolates) or serotype 1/2b (133 isolates), whereas the majority of the 42 clinical isolates were either serotype 1/2a (19 isolates) or serotype 4b (15 isolates). Additionally, 13 clinical isolates displayed pulsotypes also found in food isolates, whereas the remaining 29 clinical isolates displayed 24 unique pulsotypes. These data indicate that most (86%) of the L. monocytogenes subtypes found in the RTE foods sampled belonged to only two serotypes and that 90% of the isolates displayed 73 pulsotypes, with 107 isolates displaying pulsotype 1. These data should help define the distribution and relatedness of isolates found in RTE foods in comparison with isolates that cause listeriosis.     

Relatedness of Listeria monocytogenes Isolates Recovered from Selected Ready-To-Eat Foods and Listeriosis Patients in the United States

Pulsed-field gel electrophoresis and serotyping were performed for 544 isolates of Listeria monocytogenes, including 502 isolates recovered from contaminated samples from 31,705 retail ready-to-eat (RTE) food products and 42 isolates recovered from human cases of listeriosis. The isolates were from Maryland (294 isolates) and California (250 isolates) and were collected in 2000 and 2001. The isolates were placed into 16 AscI pulsogroups (level of relatedness within each group, ≥66%), 139 AscI pulsotypes (levels of relatedness, ≥25% to 100%), and eight serotypes (serotypes 1/2a, 1/2b, 1/2c, 3a, 3b, 4b, 4c, and 4d). The most frequently found pulsotypes belonged to either pulsogroup A (150 food isolates plus 4 clinical isolates) or pulsogroup B (104 food isolates plus 5 clinical isolates). The majority of the 502 food isolates were either serotype 1/2a (298 isolates) or serotype 1/2b (133 isolates), whereas the majority of the 42 clinical isolates were either serotype 1/2a (19 isolates) or serotype 4b (15 isolates). Additionally, 13 clinical isolates displayed pulsotypes also found in food isolates, whereas the remaining 29 clinical isolates displayed 24 unique pulsotypes. These data indicate that most (86%) of the L. monocytogenes subtypes found in the RTE foods sampled belonged to only two serotypes and that 90% of the isolates displayed 73 pulsotypes, with 107 isolates displaying pulsotype 1. These data should help define the distribution and relatedness of isolates found in RTE foods in comparison with isolates that cause listeriosis.     

Virulence profile of different phylogenetic groups of locally isolated community acquired uropathogenic E. coli from Faisalabad region of Pakistan

ABSTRACT: BACKGROUND: Uropathogenic E.coli (UPEC) are among major pathogens causing urinary tract infections. Virulence factors are mainly responsible for the severity of these emerging infections. This study was planned to investigate the distribution of virulence genes and cytotoxic effects of UPEC isolates with reference to phylogenetic groups (B2, B1, D and A) to understand the presence and impact of virulence factors in the severity of infection in Faisalabad region of Pakistan. METHODS: In this study phylogenetic analysis, virulence gene identification and cytotoxicity of 59 uropathogenic E.coli isolates obtained from non-hospitalized patients was studied. RESULTS: Among 59 isolates, phylogenetic group B2 (50%) was most dominant followed by groups A, B1 (19% each) and D (12 %). Isolates present in group D showed highest presence of virulence genes. The prevalence hlyA (37%) was highest followed by sfaDE (27%), papC (24%), cnf1 (20%), eaeA (19%) and afaBC3 (14%). Highly hemolytic and highly verotoxic isolates mainly belonged to group D and B2. We also found two isolates with simultaneous presence of three fimbrial adhesin genes present on pap, afa, and sfa operons. This has not been reported before and underlines the dynamic nature of these UPEC isolates. CONCLUSIONS: It was concluded that in local UPEC isolates from non-hospitalized patients, group B2 was more prevalent. However, group D isolates were most versatile as all were equipped with virulence genes and showed highest level of cytotoxicity.     

Distribution of virulence-associated genes in Streptococcus uberis isolated from bovine mastitis

Streptococcus uberis is an important pathogen that has been implicated in bovine mastitis but the virulence factors associated with pathogenesis are not well understood. The aim of this work was to examine 11 putative and known virulence-associated genes by PCR in 78 S. uberis strains isolated from infected animals in Argentina. Additionally, the distribution of virulence patterns over various herds was determined. Not all genes were present in the strains but all of the detected virulence-associated genes were present in combination. Forty-seven (60.3%) isolates carried seven to 10 virulence-associated genes. Further analysis revealed 58 virulence patterns. Different patterns were found within the same herd and among herds, demonstrating that strains with different virulence patterns were able to cause mastitis. Despite the large number of strains with different virulence patterns, strains with identical patterns was found. Detection of virulence-associated genes in individual S. uberis strains isolated from infected animals revealed one to 10 virulence genes. This may indicate that other virulence factors could be involved. The present study reveals the occurrence and distribution of 11 virulence-associated genes among S. uberis isolates from bovine mastitis in various herds and contributes to a better understanding of the pathogenicity of this bacterium.     

Characterization of Listeria monocytogenes recovered from 41 cases of sporadic listeriosis in Austria by serotyping and pulsed-field gel electrophoresis

41 clinical Listeria monocytogenes strains recovered from seven feto-maternal and 34 non-pregnancy associated cases of human listeriosis documented between 1997 and 2000 underwent serotyping and typing by pulsed-field gel electrophoresis (PFGE) applying the enzymes AscI, ApaI and SmaI. The pulsotypes of the clinical strains were compared to the pulsotypes of three L. monocytogenes strains isolated from healthy fecal carriers and nine reference strains isolated from seven outbreaks in Europe and the USA. The 41 clinical strains of Austrian provenance showed 37 pulsotypes. Five sets of two Austrian strains each were indistinguishable by PFGE typing. Epidemiological links were absent between these indistinguishable isolates. One unique pulsotype (AB) was found in three fecal isolates. Five pulsotypes (A, Q, R, AC and AD) were distinguished among the strains associated with outbreaks. Clusters consisting of two, five and six Austrian strains each were indistinguishable from the outbreak-associated pulsotypes A, Q and R, respectively, after PFGE analysis with AscI. Three strains of AscI pulsotype Q and five strains of AscI pulsotype R could be further differentiated by restriction with ApaI and SmaI. One strain each from sporadic cases shared a combined pulsotype with the outbreak strains of pulsotypes A and R, respectively. These PFGE data suggest that a similar genetic background can be found in strains which have been contributing to outbreaks world-wide and in isolates associated with sporadic listeriosis in Austria.     

Treatment outcome and mortality at one and half year follow-up of HIV infected TB patients under TB control programme in a district of South India

BACKGROUND: There is paucity of data from India on the impact of HIV related immunosuppression in response to TB treatment and mortality among HIV infected TB patients. We assessed the TB treatment outcome and mortality in a cohort of HIV infected TB patients treated with intermittent short course chemotherapy under TB control programme in a high HIV prevalent district of south India. METHODOLOGY/ FINDINGS: Among 3798 TB patients registered for treatment in Mysore district from July 2007 to June 2008, 281 HIV infected patients formed the study group. The socio-demographic and treatment related data of these patients was obtained from TB and HIV programme records and patient interviews 19 months after TB treatment initiation by field investigators. Treatment success rate of 281 patients was 75% while in smear positive pulmonary tuberculosis cases it was 62%, attributable to defaults (16%) and deaths (19%). Only 2 patients had treatment failure. Overall, 83 (30%) patients were reported dead; 26 while on treatment and 57 after TB treatment. Association of treatment related factors with treatment outcome and survival status was studied through logistic regression analysis. Factors significantly associated with 'unfavourable outcome' were disease classification as Pulmonary [aOR-1.96, CI (1.02-3.77)], type of patient as retreatment [aOR-4.78, CI (2.12-10.76)], and non initiation of ART [aOR-4.90, CI (1.85-12.96)]. Factors associated with 'Death' were non initiation of ART [aOR-2.80, CI (1.15-6.81)] and CPT [aOR-3.46, CI (1.47-8.14)]. CONCLUSION: Despite the treatment success of 75% the high mortality (30%) in the study group is a matter of concern and needs immediate intervention. Non initiation of ART has emerged as a high risk factor for unfavourable treatment outcome and mortality. These findings underscore the importance of expanding and improving delivery of ART services as a priority and reconsideration of the programme guidelines for ART initiation in HIV infected TB patients.