Arshnee Moodley

spa type distribution in Staphylococcus aureus originating from pigs, cattle and poultry

Methicillin-resistant S. aureus (MRSA) of clonal complex 398 (CC398) is emerging globally among production animals such as cattle, pigs and poultry as well as among humans. However, little is known about the prevalence of CC398 among methicillin sensitive S. aureus (MSSA) or the relative clonal distribution of S. aureus isolated from these three animal reservoirs. To study this, we have analyzed a random sample of S. aureus consisting of 296 epidemiologically unrelated isolates from infections and colonisation of pigs, cattle and poultry. These were examined and compared by spa and multi-locus sequence typing (MLST) and the result was compared to the most common spa types found among human blood isolates. Little overlap in spa types was seen between isolates from the three animal reservoirs or between animals and humans. Most of the porcine isolates had the spa types t034 (CC398), t1333 (CC30) and t337 (CC9), while the bovine isolates mainly had spa types t518 (CC50), t524 (CC97) and t529 (CC151). None of these spa types are common among human blood isolates in Denmark. Surprisingly, almost all of the poultry isolates (96%) belonged to CC5 (spa types t002 and t306), which is also known to be commonly found among human blood isolates and subsequent pulsed-field gel electrophoresis (PFGE) analysis identified indistinguishable PFGE patterns among a poultry isolate and selected human isolates. In conclusion, strains of MSSA CC398 were commonly present in pigs but not present at all in the other reservoirs tested.

Transmission of IncN plasmids carrying blaCTX-M-1 between commensal Escherichia coli in pigs and farm workers.

ABSTRACT CTX-M-1-producing Escherichia coli were isolated from 56 pigs, three farm personnel, two manure samples, and two air samples from two Danish pig farms where an association between prophylactic ceftiofur use and the occurrence of cephalosporin resistance was previously demonstrated. Human, animal, and environmental strains displayed high genetic diversity but harbored indistinguishable or closely related IncN plasmids carrying blaCTX-M-1, indicating that IncN plasmids mediating cephalosporin resistance were transmitted between pigs and farm workers across multiple E. coli lineages.

Carriage of Methicillin-Resistant Staphylococcus pseudintermedius in Small Animal Veterinarians: Indirect Evidence of Zoonotic Transmission

Methicillin‐resistant Staphylococcus pseudintermedius (MRSP) is increasingly reported in small animals and cases of human infections have already been described despite its recent emergence in veterinary practice. We investigated the prevalence of MRSP and methicillin‐resistant Staphylococcus aureus (MRSA) among small animal dermatologists attending a national veterinary conference in Italy. Nasal swabs were obtained from 128 veterinarians, seven of which harboured MRSP (n = 5; 3.9%) or MRSA (n = 2; 1.6%). A follow‐up study of two carriers revealed that MRSP persisted for at least 1 month in the nasal cavity. Methicillin‐susceptible S. aureus (MSSA) was isolated from 32 (25%) conference participants, whereas methicillin‐susceptible S. pseudintermedius (MSSP) was not detected, suggesting that MRSP may have a particular ability to colonize humans compared to MSSP. All isolates were characterized by spa typing. Methicillin‐resistant isolates were further typed by antimicrobial susceptibility testing, SCCmec and multi‐locus sequence typing. Two lineages previously associated with pets were identified among the five MRSP isolates; the European epidemic clone ST71‐SCCmec II‐III and ST106‐SCCmec IV. One of the two MRSA isolates displayed a genotype (ST22‐ SCCmecIV) frequently reported in dogs and cats. MRSP isolates were resistant to more antimicrobial agents compared with MRSA isolates and displayed the typical multidrug resistance patterns of MRSP in pets. The 32 MSSA isolates belonged to 20 spa types and the most frequent types (t12, t15 and t166) were associated with common S. aureus lineages in humans (CC30 and CC45). Although low, the 3.9% MRSP carriage rate found among small animal dermatologists was surprising in consideration of the rare occurrence of S. pseudintermedius in humans, the lack of MSSP detection and the recent appearance of MRSP in Europe. As cases of human MRSP infection have been linked with pets, veterinarians should be aware of this zoonotic risk and proper preventative measures should be taken to avoid MRSP transmission from animal patients.

Tandem repeat sequence analysis of staphylococcal protein A (spa) gene in methicillin-resistant Staphylococcus pseudintermedius.

A putative staphylococcal protein A (spa) gene was discovered in the genome of Staphylococcus pseudintermedius and used for developing a species-specific spa typing protocol. Thirty-one clinical methicillin-resistant S. pseudintermedius (MRSP) isolates from dogs and cats in four countries were characterized by spa typing, pulsed-field gel electrophoresis (PFGE) and staphylococcal cassette chromosome (SCCmec) typing. The results indicated the occurrence of two MRSP clones that acquired distinct SCCmec elements in Europe (t02, PFGE type A, SCCmec type III,) and California (t06, PFGE type B, SCCmec type V). Sequence analysis of mecA revealed the occurrence of four alleles (mecA1 to mecA4), which correlated with the geographical origin of the isolates and enabled discrimination of two distinct subtypes within the European clone. The newly developed spa typing method appeared to be a promising tool for easy and rapid typing of MRSP, either alone or in combination with SCCmec and mecA typing for fine-structure epidemiological analysis.

Rapid PCR detection of Staphylococcus aureus clonal complex 398 by targeting the restriction-modification system carrying sau1-hsdS1.

ABSTRACT A PCR targeting sau1-hsdS1 was developed for rapid detection of Staphylococcus aureus clonal complex 398 (CC398). High sensitivity (100%) and specificity (100%) were shown by evaluating the test on a large strain collection (n = 1,307). We recommend this test for accurate, rapid, and inexpensive diagnosis of methicillin-resistant S. aureus (MRSA) CC398 in hospitals and on farms.

The Distribution of Mobile Genetic Elements (MGEs) in MRSA CC398 Is Associated with Both Host and Country

Methicillin-resistant Staphylococcus aureus clonal complex (CC) 398 has emerged from pigs to cause human infections in Europe and North America. We used a new 62-strain S. aureus microarray (SAM-62) to compare genomes of isolates from three geographical areas (Belgium, Denmark, and Netherlands) to understand how CC398 colonizes different mammalian hosts. The core genomes of 44 pig isolates and 32 isolates from humans did not vary. However, mobile genetic element (MGE) distribution was variable including SCCmec. φ3 bacteriophage and human specificity genes (chp, sak, scn) were found in invasive human but not pig isolates. SaPI5 and putative ruminant specificity gene variants (vwb and scn) were common but not pig specific. Virulence and resistance gene carriage was host associated but country specific. We conclude MGE exchange is frequent in CC398 and greatest among populations in close contact. This feature may help determine epidemiological associations among isolates of the same lineage.

Multilocus sequence typing of IncN plasmids

OBJECTIVES Incompatibility group N (IncN) plasmids have been associated with the dissemination of antimicrobial resistance and are a major vehicle for the spread of bla(VIM-1) in humans and bla(CTX-M-1) in animals. A plasmid multilocus sequence typing (pMLST) scheme was developed for rapid categorization of IncN plasmids. METHODS Twelve fully sequenced IncN plasmids available at GenBank were analysed in silico for selecting the loci for the IncN-specific pMLST. A total of 58 plasmids originating from different reservoirs (human, pig, poultry, cattle and horses) and geographic regions (Italy, Greece, Denmark, UK and The Netherlands) were classified by DNA sequencing of the amplicons obtained for the repA, traJ and korA loci. RESULTS Eleven sequence types (STs) were defined on the basis of allele sequences of the three selected loci. Most plasmids carrying bla(CTX-M-1) (24/27) isolated in different countries from both animals and humans belonged to ST1, suggesting dissemination of an epidemic plasmid through the food chain. Fifteen of 17 plasmids carrying bla(VIM-1) from Klebsiella pneumoniae and Escherichia coli, isolated during a 5 year period in Greece were assigned to ST10, suggesting that spread and persistence of this particular IncN-carrying bla(VIM-1) lineage in Greece. CONCLUSIONS This study proposes the use of pMLST as a suitable and rapid method for identification of IncN epidemic plasmid lineages. The recent spread of bla(CTX-M-1) among humans and animals seems to be associated with the dissemination of an epidemic IncN plasmid lineage.

Effects of tetracycline and zinc on selection of methicillin-resistant Staphylococcus aureus (MRSA) sequence type 398 in pigs.

An in vivo experiment was conducted to evaluate the effects of tetracycline and zinc on pig colonization and transmission of methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST) 398. Eight piglets naturally colonized with MRSA ST398 and 8 MRSA-negative piglets of the same age and breed were assigned to three groups treated with tetracycline and zinc (Group 1), zinc (Group 2) or tetracycline alone (Group 3) and one non-treated group (Group 4), each containing two MRSA-positive and two MRSA-negative animals. Two additional non-treated control groups composed of only MRSA-positive (Group 5) and MRSA-negative (Group 6) animals were used to check for stability of MRSA carriage status. Nasal swabs and environmental wipes were collected on Days 0, 7, 14, and 21, and the occurrence of MRSA in each sample was quantified by bacteriological counts on Brilliance™ MRSA agar. Significantly higher nasal MRSA counts were observed in the zinc-treated (p=0.015) and tetracycline-treated (p=0.008) animals compared to the non-treated animals. Environmental MRSA counts appeared to increase over time in Groups 1 and 2 but such an increase was not statistically significant. MRSA-negative animals housed with MRSA-positive animals became positive in all groups, whereas the carriage status of the animals in Groups 5 and 6 did not change. This study demonstrates that feed supplemented with tetracycline or zinc increases the numbers of MRSA ST398 in the nasal cavity of pigs. Transmission of MRSA from positive to negative animals housed within the same pen was not influenced by exposure to these agents.

Antimicrobial resistance in methicillin susceptible and methicillin resistant Staphylococcus pseudintermedius of canine origin: literature review from 1980 to 2013.

Staphylococcus pseudintermedius is a commensal and a common opportunistic pathogen causing mainly infections of the integumentary system in dogs. The recent emergence of multidrug-resistant S. pseudintermedius isolates, in particular methicillin-resistant strains (MRSP) is a threat to small animal health and highlights the need for antimicrobial resistance surveillance to detect trends and potentially perform timeous interventions. We systematically reviewed 202 published articles to investigate temporal changes in antimicrobial resistance in clinical and commensal S. pseudintermedius isolated from dogs in 27 countries between 1980 and 2013. Resistance to the most common antimicrobials tested for in published studies and important for the treatment of staphylococcal infections in dogs were assessed separately for methicillin resistant (MRSP) and methicillin susceptible (MSSP) isolates. Stratified by MSSP and MRSP, no significant increases in antimicrobial resistance were observed over time, except for the penicillinase-labile penicillins (penicillin and ampicillin) among MSSP. However, in recent years, a few studies have reported higher-level of resistance to amikacin, gentamicin and enrofloxacin amongst MSSP. The review highlights inconsistencies between studies as a result of several factors, for example the use of different antimicrobial susceptibility testing methods and interpretation criteria. We recommend that data on susceptibility in important companion animal pathogens are collected and presented in a more harmonized way to allow more precise comparison of susceptibility patterns between studies. One way to accomplish this would be through systematic surveillance either at the country-level or at a larger scale across countries e.g. EU level.

Molecular Characterization of Clinical Methicillin-Resistant Staphylococcus aureus Isolates in South Africa

ABSTRACT 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.