Staphylococcus aureus Isolates Carrying Panton-Valentine Leucocidin Genes: Their Frequency, Antimicrobial Patterns, and Association With Infectious Disease in Shahrekord City, Southwest Iran

Prevalence of mecA and Panton-Valentine Leukocidin Genes in Staphylococcus aureus Clinical Isolates from Gaza Strip Hospitals

Methicillin-resistant Staphylococcus aureus (MRSA) are spreading worldwide in hospital and community settings, thus posing a serious public health problem. Panton-Valentine Leukocidin (PVL), an important virulence factor of S. aureus, is a marker of community-acquired MRSA. Here we determined the prevalence of pvl genes among S. aureus isolates from different hospitals in the Gaza Strip, Palestine. A total of 285 S. aureus isolates were collected from five different hospitals in the Gaza Strip. All isolates were characterized for their susceptibility patterns to available antimicrobial agents and by using multiplex PCR for the detection of mecA and pvl genes. The overall prevalence of MRSA in Gaza hospitals was 70.2% (range: 76.3% to 65.5%) and that of pvl among S. aureus isolates was 29.8% (range: 32.9% to 26.2%). The pvl gene was equally prevalent among MRSA isolates (30.5%) and MSSA isolates (28.2%). The most effective antibiotics were rifampicin, vancomycin, and clindamycin, with susceptibility rates of 91.2%, 88.7%, and 84.6%, respectively. The highest percentage of strains were observed to be resistant to penicillin and amoxicillin with clavulanic acid-96.1% and 73.6%, respectively. Our results showed a high prevalence of MRSA and pvl-positive isolates in Gaza Strip hospitals, which likely reflects the situation in the community. It is mandatory to implement systematic surveillance of both hospital and community isolates, together with interventions (such as increased hand hygiene, use of hydroalcoholic solutions, and isolation of carriers) to limit their spread.

Detection of Panton-Valentine leukocidin and MecA Genes in Staphylococcus aureus isolated from Iraqi Patients

A gram-positive bacterium, Staphylococcus aureus, which is widely distributed is considered as a bacterial infection that commonly infects the skin and mucous membranes. Such infections can be the cause of death and illness. In the present study by using reverse transcription-polymerase chain reaction (rt-PCR) the Panton-Valentine leukocidin (PVL) and MecA genes of S. aureus which were isolated from skin and soft tissue infections (SSTIs) in Baghdad, Iraq were investigated. This study included 96 S. aureus isolated from SSTIs and identified by Vitek. The results showed that 61 (63.5%) and 48 (50%) of the isolates were positive for PVL and MecA genes, respectively. This work presented an effective real-time PCR technique for detecting PVL genes alone or in conjunction with MecA. The rt-PCR allows for easier reaction monitoring and eliminates the need for post-PCR processing, saving both resources and time. Moreover, it is ideal for diagnostic applications because of its high sensitivity, simplicity, and specificity. Besides, the rt-PCR has an option to do all the procedures in an automated mode of action.

Molecular characteristics of antimicrobial resistance and virulence determinants of Staphylococcus aureus isolates derived from clinical infection and food

BACKGROUND

Staphylococcus aureus (S. aureus) is an important human etiologic agent. An investigation of the characteristics of common genotypes of S. aureus relating to pathogenicity and antibiotic resistance may provide a foundation to prevent infection.

METHODS

This study collected 275 S. aureus isolates from Zhengzhou city in China, including 148 isolates from patient samples and 127 isolates from ready-to-eat food samples. Antimicrobial susceptibility testing was performed using the broth dilution method. Molecular characteristics of antimicrobial resistance, virulence, and genotypes were identified by polymerase chain reaction (PCR).

RESULTS

In total, 34.18% (94/275) of S. aureus isolates were MRSA. Compared with food isolates, clinical isolates had significantly higher antibiotic resistance rates, carrying resistance genes such as acc(6')/aph(2'), aph(3')-III, ermA, and ermB and virulence genes such as tetM, sea, seb, pvl, and etb. MRSA-t030-agrI-SCCmecIII and MSSA-t002-agrII were the most common strain types among clinical strains, and MRSA-t002-agrII-SCCmecIII and MSSA-t002-agrII were the most common strain types among food strains. Additionally, some strains in the agr group were also spa type-specific, suggesting that there may be phenotypic consistency.

CONCLUSION

Clinical isolates contained higher numbers of resistance genes and demonstrated higher antibiotic resistance, while 2 source strains exhibited high toxicity. These results indicate that bacteria with different origins may have undergone different evolutionary processes. As resistance and virulence factors in food bacteria can be transmitted to humans, food handlers should strictly follow hygienic measures during food production to ensure the safety of human consumers.

Staphylococcus aureus Isolates from Bovine Mastitis in Eight Countries: Genotypes, Detection of Genes Encoding Different Toxins and Other Virulence Genes

Staphylococcus aureus is recognized worldwide as one of the major agents of dairy cow intra-mammary infections. This microorganism can express a wide spectrum of pathogenic factors used to attach, colonize, invade and infect the host. The present study evaluated 120 isolates from eight different countries that were genotyped by RS-PCR and investigated for 26 different virulence factors to increase the knowledge on the circulating genetic lineages among the cow population with mastitis. New genotypes were observed for South African strains while for all the other countries new variants of existing genotypes were detected. For each country, a specific genotypic pattern was found. Among the virulence factors, fmtB, cna, clfA and leucocidins genes were the most frequent. The sea and sei genes were present in seven out of eight countries; seh showed high frequency in South American countries (Brazil, Colombia, Argentina), while sel was harboured especially in one Mediterranean country (Tunisia). The etb, seb and see genes were not detected in any of the isolates, while only two isolates were MRSA (Germany and Italy) confirming the low diffusion of methicillin resistance microorganism among bovine mastitis isolates. This work demonstrated the wide variety of S. aureus genotypes found in dairy cattle worldwide. This condition suggests that considering the region of interest might help to formulate strategies for reducing the infection spreading.

Relationships among superantigen toxin gene profiles, genotypes, and pathogenic characteristics of Staphylococcus aureus isolates from bovine mastitis

Staphylococcus aureus is one of the major etiological agents of bovine mastitis, harboring a wide variety of staphylococcal superantigen (SAg) toxin genes. The SAg toxin genes are reported to be closely associated with the pathogenicity of the Staph. aureus causing the bovine mastitis. This study was conducted to investigate SAg toxin gene profiles and to assess the relationships among SAg toxin genes, genotypes of Staph. aureus, and their pathogenic properties. A total of 327 quarter milk samples were collected from bovine mastitis cases for isolation and identification of pathogens. In total, 35 isolates were identified as Staph. aureus, and the prevalence of Staph. aureus in milk samples was 13.6% (35/256). Polymerase chain reaction (PCR) and randomly amplified polymorphic DNA (RAPD) assays were used to detect the SAg toxin genes and to genotype Staph. aureus strains isolated from milk samples of bovine mastitis in 10 dairy herds located in Ningxia, China, respectively. The results showed that among the Staph. aureus isolates (n = 35), 71.4% (n = 25) of isolates carried at least one SAg toxin gene. In total, 18 SAg genes and 21 different gene combination patterns were detected among these isolates. The most common SAg genes in Staph. aureus isolates were sei, sen, and seu (44.0% each), followed by seo, tst, and etB (28.0% each), etA (24.0%), sem and sep (16.0% each), seb, sec, sed, and sek (12.0% each), and sea and seh genes (8.0% each); the seg, sej, and ser genes were present in 4.0% of the isolates. Three gene combinations were found to be related to mobile genetic elements that carried 2 or more genes. The egc-cluster of the seg-sei-sem-sen-seo genes, located on the pathogenicity island Type I υSaβ, was detected in 16% of isolates. Interestingly, we observed 6 RAPD genotypes (I to VI) in Staph. aureus isolates, and 2 of these genotypes were strongly associated with the severity of bovine mastitis; there was a close relationship between the RAPD genotypes and SAg genes. Isolates of RAPD type III were more frequently associated with clinical and subclinical mastitis, whereas strains of type VI were mostly related to subclinical mastitis. In addition, SAg genes were related to severity of bovine mastitis. We conclude that an obvious relationship exists among RAPD genotypes, SAg toxin genes, and severity of bovine mastitis.