Low-Level Antibiotic Resistance among Staphylococcus aureus and Gram-Negative Pathogens from Infected Skin and Soft Tissues in Rural Kenya

Introduction: Bacterial skin and soft tissue infections (SSTIs) are a cause of frequent inpatient and outpatient care visits whose causative agents are associated with a high antimicrobial resistance burden. For insights on antimicrobial susceptibilities in a rural setting, we examined specimens from suspected SSTIs from two public health facilities in Kenya. We additionally assessed antibiotic use, appropriateness of empiric therapy and risk factors for SSTI. Methodology: Between 2021 and 2023, 265 patients at Kisii and Nyamira County Referral hospitals were enrolled. Wound swabs/aspirates were collected and processed following standard microbiological procedures. Identification and antimicrobial susceptibility were performed using the VITEK 2 Compact platform. Demographic, clinical, and microbiological data were analyzed with R Statistical software. Results: S. aureus was isolated in 16.2% (43/265) of patients with a methicillin resistance (MRSA) proportion of 14% (6/43). While 13/15 drugs elicited susceptibilities ranging from 84% - 100%, penicillin (16%) and trimethoprim-sulfamethoxazole [TMP-SXT] (23%) yielded the lowest susceptibilities. Escherichia coli (n = 33), Klebsiella pneumoniae (n = 8), Pseudomonas aeruginosa (n = 8), and Citrobacter species (n = 4) were the most commonly isolated gram-negative species. Gram-negative strains showed high susceptibilities to most of the tested drugs (71% - 100%) with the exception of ampicillin (18%), TMP-SXT (33%), and first and second generation cephalosporins. Conclusions: The low MRSA prevalence and generally high antibiotic susceptibilities for S. aureus and gram-negative bacteria present opportunities for antibiotic stewardship in the study setting. Diminished susceptibilities against penicillin/ampicillin and TMP-SXT accord with prevailing local data and add a layer of evidence for their cautious empiric use.

Electrochemical Biosensor for Detection of Staphylococcus aureus Based on Nucleic Acid Aptamers

Staphylococcus aureus is a gram-staining positive cocci bacillus baterium and also one of the foodborne pathogens, which is a serious potential hazard to human health and food safety. We constructed an electrochemical biosensor for the detection of S. aureus based on nucleic acid aptamers to achieve highly specific detection of S. aureus. The detection of S. aureus was realized by using Aptamer (Apt) to capture S. aureus, which resulted in a change in the spatial conformation of Apt and a decrease in the electrochemical signal. Under the optimized experimental conditions, the detected electrochemical signals were positively correlated with the concentration of S. aureus with a linear range of 1 × 101 - 1 × 105 CFU/mL, a detection limit of 4.76 CFU/mL, and an experimental recovery of 97.43% - 99.37%. Therefore, we successfully constructed an electrochemical biosensor for the specific detection of S. aureus, which has the advantages of high specificity, sensitive detection and convenient operation.

The Prevalence of Methicillin-Resistant Staphylococcus aureus Colonization in Patients with Complicated Skin and Skin Structure Infections after Treatment with Linezolid or Vancomycin

Background: Complicated skin and skin structure infections (cSSSIs) due to Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), are associated with significant morbidity. Re-ducing MRSA carriage has been a focus of infection control interventions. The prevalence of MRSA colonization after successful treatment of a MRSA cSSSI is unknown. Methods: Secondary analysis of a randomized controlled trial comparing linezolid and vancomycin for the treatment of MRSA cSSSI. Adult patients that had a colonization culture, confirmed MRSA cSSSI, received at least one dose of study treatment, and had an outcome recorded at end of study. Patient, clinical characteristics and prevalence of colonization were compared by treatment regimens. A multivariate regression model identified predictors of MRSA colonization at EOS. Results: There were 456 patients evaluated. The prevalence of MRSA colonization was higher for vancomycin treated patients compared to linezolid treated patients at end of treatment (EOT) (28% vs. 5%, p < 0.001) and EOS (34% vs. 22%, p < 0.01). Independent predictors of colonization at EOS after treatment for a MRSA cSSSI included diagnosis, primarily driven by abscess, black race, treatment with vancomycin, MRSA mixed infection and male gender. Conclusion: Patients treated with linezolid for a cSSSI had less MRSA colonization at EOT and EOS compared to those treated with vancomycin. Multiple independent predictors of MRSA colonization were identified. Additional studies evaluating the relationship of MRSA colonization after treatment of cSSSI are needed.

Evaluation of the Antibacterial and Antifungal Capacity of Nanoemulsions Loaded with Synthetic Chalcone Derivatives Di-Benzyl Cinnamaldehyde and Benzyl 4-Aminochalcone

With the increase in antimicrobial resistance,it has become necessary to explore alternative approaches for combating and preventing diseases.DB-cinnamaldehyde(CNM)and Benzyl4-amino(B4AM)are bioactive compounds derived from chalcones but with restricted solubility in aqueous media.Nanoemulsions can enhance the solubility of compounds and can be a promising alternative in the development of novel antimicrobials,with reduced side effects and prolonged release.The objective of this study was to evaluate the stability of oil-in-water nanoemulsions loaded with two distinct types of chalcones at two different dosages,to propose a stable formulation with antimicrobial properties.Results showed that nanoemulsions presented high encapsulation efficiency,low polydispersity index(PDI)and particle size below 200 nm,indicating that emulsification was a suitable method for nanoemulsion preparation.Nanoemulsions with higher dosages exhibited significant antimicrobial effects when compared to free chalcones and positive controls.Notably,B4AM nanoemulsions at higher dosages showed expressive activity against Salmonella minnesota,with a 420%greater inhibitory response compared to the free form and showing equivalence to the positive control.CNM nanoemulsions showed excellent inhibitory activity at the highest dosage,equivalent to the positive control against S.minnesota and Staphylococcus aureus.The greater number of conjugated bonds in CNM increased the antimicrobial activity in comparison with B4AM,and the formation of nanometric domains enhanced the bioavailability,being a promising alternative for antimicrobial applications.

Community-acquired pneumonia:The importance of the early detection of drug-resistant organisms

Pneumonia is a disease associated with significant healthcare burden with over 1.5 million hospitalizations annually and is the eighth leading cause of death in the United States.While community-acquired pneumonia(CAP)is generally considered an acute time-limited illness,it is associated with high long-term mortality,with nearly one-third of patients requiring hospitalization dying within one year.An increasing trend of detecting multidrug-resistant(MDR)organisms causing CAP has been observed,especially in the Western world.In this editorial,we discuss about a publication by Jatteppanavar et al which reported that a case of a MDR organism was the culprit in developing pneumonia,bacteremia,and infective endocarditis that led to the patient’s death.The early detection of these resistant organisms helps improve patient outcomes.Significant advances have been made in the biotechnological and research space,but preventive measures,diagnostic techniques,and treatment strategies need to be developed.

原料奶贮存和运输过程中S.aureus的暴露评估

以哈尔滨市地区为例,运用概率评估方法研究原料奶中金黄色葡萄球菌(S.aureus)的暴露程度,进而推断其肠毒素产生的可能性。整个暴露评估模型的建模方法采用概率评估法。模型采用Monte Carlo模拟技术,通过风险分析软件@RISK4.5对榨乳后不同冷却方式、贮存方式、运输方式等可能对乳中S.aureus造成生物性危害的可能性进行了评估。结果表明,个体奶户采用冷水降温方式贮存的牛乳中S.aureus可能引发的安全性风险最大,需严格控制贮存温度和时间,防止S.aureus在原料乳中的迅速生长繁殖及产毒,进而从源头上为乳及其制品的安全生产提供保障。

CpG-ODN对S.aureus诱导的山羊实验性乳腺炎乳腺的保护作用研究

选择同处于泌乳初期的睢宁白山羊6头,于右乳区经过乳导管灌注10μg/kgCpG-ODN,左乳区则灌入等体积的灭菌100μL0.01mol/LpH7.2磷酸盐缓冲液(PBS)作为对照,灌注后第3d按同等剂量进行二次灌注,二次灌注后第2d,分别于左右乳区经乳导管灌注3mL(2×109CFU/mL)金黄色葡萄球菌(S.aureus),于灌注细菌前(0h),灌注后8h,16h,24h,48h和72h分别收集左右乳区乳汁进行检测。临床症状观察显示,乳腺内灌注3mL(2×109CFU/mL)的S.aureus能迅速诱导山羊典型的急性乳腺炎症状。组织学观察显示感染S.aureus后72h乳腺腺泡内仍有嗜中性粒细胞(PMN)浸润,但实验乳区明显减少。乳汁S.aureus数同在感染后24h上升至最高,CpG-ODN能显著降低各个时间点乳汁细菌数。乳汁白细胞介素-6(IL-6)水平同在感染后24h上升至最高,CpG-ODN能显著提高感染后24h乳汁IL-6水平。对照和CpG-ODN处理乳区乳汁肿瘤坏死因子-α(TNF-α)水平分别在感染后24h和16h上升至最高,其中在感染后24h实验乳区比对照下降40.63%(P<0.05)。乳汁N-乙酰-β-D-氨基葡萄糖苷酶(NAGase)水平同在感染后16h达最高(P<0.01),CpG-ODN能显著提高感染后8h乳汁NAGase水平。上述结果表明CpG-ODN可通过提高乳汁IL-6水平、加速并促进乳汁TNF-α的释放,从而减少了乳汁中S.aureus数量,减轻了炎症介质对细胞的损伤,对缩短炎症过程也有一定的作用,实验结果证实了CpG-ODN对S.aureus感染诱发的山羊乳腺炎的乳腺有保护作用。

低温等离子体杀灭橙汁S.aureus的研究

非热杀菌能更好地提供产品质量,保留较好的营养成分,比传统杀菌技术更能节省能源,为开拓新的市场创造更大机遇。利用自行设计的介质阻挡放电反应器(DBDR),以鲜榨果汁为杀菌介质,研究DBDR所产生的低温等离子体(LTP)对鲜榨果汁的金黄色葡萄球菌(S.aureus)的杀菌规律。选取循环次数、pH、温度和电压4个因素进行中心组合设计,利用响应面对其杀菌规律进行研究,建立了低温等离子体(LTP)杀灭橙汁中S.aureus的二次多项数学模型,验证了模型的有效性,利用DesignExpert软件对其进行分析表明:循环7次,pH2.5,温度50℃,电压25kV时,杀菌率log(N0/N)最大,其预测值为5.19,与实测值相符。

Development of a Multiplex PCR for Diagnosis of Staphylococcus aureus, Escherichia coli and Bacillus cereus from Cows with Endometritis

Staphylococcus aureus, Escherichia coli and Bacillus cereus are the major agents of cow endometritis in dairy cows. A multiplex PCR （SEB-mPCR） was established based on the conserved genes of S. aureus, E. coli and B. cereus, and the detection limits were 103, 102 and 103 CFU mL-1, respectively. SEB-mPCR could not amplify genomic DNA of pathogenic bacteria of other common bovine diseases. A total of 309 vaginal discharge samples from cows with endometritis were tested by SEB-mPCR. Of the samples, 23.95% had the three kinds of bacteria detected, 17.15% had S. aureu and E. coli, 9.39% had E. coli and B. cereus, and 9.71% had S. aureus and B. cereus. The rates of infections with S. aureus, E. coli and B. cereus were 11.35, 16.18 and 9.06%, respectively. Therefore, SEB-mPCR has a potential as a diagnosis tool for endometritis in dairy cows.

Effect of Nano - Titanium Dioxide with Different Antibiotics against Methicillin-Resistant Staphylococcus Aureus

The different investigation has been carried out on the biological activities of titanium dioxide nanoparticle but the effect of this nano product on the antibacterial activity of different antibiotics has not been yet demonstrated. In this study the nano size TiO2 is synthesized using citric acid and alpha dextrose and the enhancement effect of TiO2 nanoparticle on the antibacterial activity of different antibiotics was evaluated against Methicillin-resistant Staphylococcus aureus (MRSA). During the present study, different concentrations of nano-scale TiO2 were tested to find out the best concentration that can have the most effective antibacterial property against the MRSA culture. Disk diffusion method was used to determine the antibacterial activity of these antibiotics in the absence and presence of sub inhibitory concentration of TiO2 nano particle. A clinical isolate of MRSA, isolated from Intensive Care Unit (ICU) was used as test strain. In the presence of sub-inhibitory concentration of TiO2 nanoparticle (20 μg/disc) the antibacterial activities of all antibiotics have been increased against test strain with minimum 2 mm to maximum 10mm. The highest increase in inhibitory zone for MRSA was observed against pencillin G and amikacin (each 10 mm). Conversely, in case of nalidixic acid, TiO2 nanoparticle showed a Synergic effect on the antibacterial activity of this antibiotic against test strain. These results signify that the TiO2 nanoparticle potentate the antimicrobial action of beta lactums, cephalosporins, aminoglycosides, glycopeptides, macrolids and lincosamides, tetracycline a possible utilization of nano compound in combination effect against MRSA.

Studies on Enterotoxins and Antimicrobial Resistance in Staphylococcus aureus Isolated from Various Sources

Staphylococcus aureus represents a public health challenge all over the world. Therefore, this study aims to analyze the prevalence of five genes (sea, seb, sec, see and seg) encoding the staphylococcal enterotoxins in S. aureus isolated from different sources and to evaluate the association of these toxins in comparison to susceptibility towards 12 antimicrobials;antimicrobial susceptibility was conducted by disc diffusion method. Detection of staphylococcal enterotoxins was performed by PCR and the ability to express these genes was assessed among isolates by RT-PCR. The most common enterotoxin gene was sea gene (66%), followed by seb, sec, see and seg (38%, 23%, 19% and 5%) respectively. Expression of sea, seb and seg genes was variable. However, sec and see genes were not expressed by any of the tested isolates. No statistically significant association exists between (seb, sec and see) and isolation sources, while the sea was significantly associated with clinical isolates. High significant correlation was found between elevated sea expression and multidrug-resistance. Our findings indicate that the pathogenic potential of S. aureus may be greater than previously thought. This emphasizes the utmost need to implement proactive measures and more emphasis will be placed on the application of hygiene practices in hospitals to control S. aureus infection and enterotoxins production.

Menaquinone (Vitamin K2) Enhancement of <i>Staphylococcus aureus</i>Biofilm Formation

During infection, Staphylococcus aureus is exposed to exogenous menaquinone which is essential for the human blood clotting cascade. The effect of exogenous menaquinone on S. aureus phenotypic expression is not known. To test whether menaquinone affects expression of virulence-associated phenotypes, methicillin-sensitive (MSSA) and -resistant (MRSA) S. aureus strains (n = 8) were grown in the presence of menaquinone (0.001 - 12 μg/ml). Capsule production, biofilm formation (plastic and fibronectin-coated microtiter plates) and carotenoid levels were determined spectrophotometrically after growth in Mueller Hinton broth (MH;24-hr, 37°C). All experiments were, at minimum, done in triplicate and repeated twice. Menaquinone at physiologic levels (0.01 μg/ml MH) significantly increased (p 0.05) biofilm formation on plastic in a manner that was bacterial population size dependent. In addition, menaquinone (0.05 - 4 μg/ml) significantly increased (p 0.05) biofilm formation on fibronectin-coated surfaces for four MSSA strains and one MRSA strain by two to six-fold as compared to medium controls. However, menaquinone had no effect on capsule production or cell-associated carotenoid levels. Menaquinone’s effect on biofilm formation on fibronectin-coated surfaces appears to be regulated by sarA. These findings are the first to demonstrate that a vitamin at concentrations reported in humans affects S. aureus virulence-associated phenotypes.

Effect of Ciprofloxacin on S.aureus and E.coli Growth in Presence of Vitamin C Using Cup Cut Diffusion Method

Ciprofloxacin is a second-generation of fluoroquinolone,broad-spectrum antibiotic with bactericidal activity against Gram-positive and Gram-negative organisms.It is one of the most widely used antibiotics,because of its efficacy,safety,and relatively low cost.Ascorbic acid(vitamin C)is water-soluble monosaccharide antioxidant;it is essentially required by the body for its various biochemical and physiological processes.S.aureus is Gram-positive cocci;widely distributed in the environment,it is a member of the normal flora of the body.S.aureus is not always pathogenic;it is a common cause of skin infections including abscesses,respiratory infections such as sinusitis,and food poisoning.E.coli is Gram-negative bacteria,found in the environment,foods,and intestines.Most E.coli strains are harmless;it is part of the normal microbiota of the gut.However,some serotypes of E.coli cause serious food poisoning in their hosts;it can cause diarrhea,while others cause urinary tract infections,respiratory illness and pneumonia,and other illnesses.Method:Cup cut diffusion method was applied.Experiment I:is carried out to choose the concentration of vitamin C to be used in experiment II.The negative control is normal saline,added in cup in each plate,vitamin C(100 mg/mL,200 mg/mL,400 mg/mL)was added,the volume in each cup was 100μL.Experiment II:Eight groups of treatments were applied.The first is the negative control(1%normal saline),the second group is the positive control of vitamin C(200 mg/mL).The third,fourth and fifth groups are ciprofloxacin with different concentrations(10 mg/mL,20 mg/mL,40 mg/mL);the sixth,seventh and eighth are the combination of vitamin C with each concentration of ciprofloxacin(10 mg/mL,20 mg/mL,40 mg/mL).Each group includes six petri dishes.Bacterial plates were incubated at 37 oC for 24 h and 48 h.Zone of inhibition is measured in mm.Results and conclusion:Ciprofloxacin produces dose dependent increase in zone of inhibition of S.aureus and E.coli growth,after 24 and 48 hours incubation.While vitamin C in the concentration used produced inhibitory effect on the growth of S.aureus and E.coli,after 24 hours incubation,vitamin C effect was not changed after 48 hours incubation.After 24 hours incubation,vitamin C potentiated the effect of ciprofloxacin at low concentration(10 mg/mL);while vitamin C antagonized the effect of ciprofloxacin at higher concentrations(20 and 40 mg/mL)on S.aureus growth.In the same time,ciprofloxacin antagonized the inhibitory effect of vitamin C on S.aureus growth.After 48 hours incubation,S.aureus produced resistance against ciprofloxacin alone,and that combined with vitamin C compared to zone of inhibition after 24 hours.Ciprofloxacin produced dose dependent inhibition of E.coli growth after incubation for 24 and 48 hours.Vitamin C potentiated the inhibitory effect induced by ciprofloxacin(additive effect).The inhibitory effect of ciprofloxacin,vitamin C and the combination was not changed after 48 hours compared to 24 hours.

Cross Sectional Study of Skin Carriage and Enterotoxigenicity of Staphylococcus aureus among Food Handlers

The prevalence of enterotoxigenic Staphylococcus aureus was investigated among 200 participants working in three different food processing plants in Egypt. Using skin swabs, 75 (38%) of the 200 tested persons were positive for the presence of S. aureus. Of the S. aureus positive persons, 28 (14%) harboured S. aureus produced staphylococcal enterotoxins. The serotypes of these enterotoxins were enterotoxin A (68%), enterotoxin B (36%), enterotoxin C (46%) and enterotoxin D (18%). Some of these isolates produced more than one type of enterotoxins namely AB, AC, BC, BD, ABC and ACD. Analysis of risk factors implicated in skin carriage of S. aureus as age, gender, marital status, education, duration in employment, frequency and method of hand wash and incidence of chronic skin infection revealed insignificant association with staphylococcal skin carriage. The obtained results put forth the risk of food contracting contamination with enterotoxigenic strains of S. aureus owing to skin colonization of S. aureus among food handlers.

A Review of <i>Staphylococcus aureus</i>and the Emergence of Drug-Resistant Problem

There are various bacteria living in this world. The most common one is Staphylococcus aureus. Almost everyone has heard of it. It is easy to find their habitats, such as hospitals, homes, parks, schools etc. Some of them are difficult to be eliminated because of drug-resistant mutations. Hence, lots of researchers devoted their efforts to eliminate them. This review illustrates the characteristics of the Staphylococcus aureus and the main threat of their drug-resistant strains, especially methicillin-resistant S. aureus. What’s more, the article also highlights the plight in the drug development.

Quantitative Adhesion of <i>Staphylococcus aureus</i>on Stainless Steel Coated with Milk

The surface energy characteristics of uncoated (clean) and coated stainless steel with UHT milk at various contact time (5 min, 30 min, 1 hours, 3 hours, 6 hours, 24 hours) were determined using contact angle measurement. Whatever the contact time, the clean stainless steel coupons became more hydrophobic and more electron acceptor when they are coated by milk. Inversely, the electron donor character seems to decreasing in this condition. The calculated surface energy component of coated stainless steel was found to vary with contact time. Its hydrophobicity and its electron acceptor were minimal after 3 hours of contact, but its electron donor was minimal after 1 hours of contact. Adhesion experiments of Staphylococcus aureus were carried out on uncoated and coated stainless steels at various contact times. For all contact times, the adhesion results show that milk reduce S. aureus adhesion, and the level of this reduction depend on contact time. This reduction was lower and higher after 1 hours, 5 min and 30 min of contact respectively.

Comparative Study of Three β Lactamase Test Methods in <i>Staphylococcus</i>aureus Isolated from Two Nepalese Hospitals

Background: β lactamase is a plasmid-encoded enzyme that hydrolyzes β lactam ring of β lactam antibiotics rendering them ineffective. These enzymes, produced by Staphylococcus aureus along with many other organisms, have hindered the use of many useful and once life-saving β lactam antibiotics from clinical practice. Methods: This study was aimed to compare three test methods-chromogenic, acidimetric and iodometric-for the detection of β lactamase enzyme produced by 404 nosocomial induced S. aureus isolated from two Nepali hospitals, Kathmandu based hospital (KBH) and Lalitpur based Hospital (LBH). The study was carried out following standard methodology during November 2007 to June 2009 in the Department of Microbiology, Institute of Medicine, Kathmandu, Nepal. Sensitivity, specificity, efficiency, positive predictive value, and negative predictive values of the tests were calculated taking penicillin resistance and sensitivity as the standard. Results: Chromogenic method was found to be the most sensitive (98.93%) and efficient (98.51%) test and had a high positive predictive value (99.46%). Sensitivity (98.4%) and efficiency (98.27%) of iodometric method was found to be comparable to chromogenic test;its specificity (96.55 %) and positive predictive value (99.73%) were the highest among the 3 tests. Acidimetric test was the least sensitive (97.33%) and efficient (96.78%). Of note, the sensitivity and specificity of these test methods have been compromised due to the negativity of few penicillin resistant isolates and positivity of some penicillin sensitive isolates, respectively. Conclusion: Chromogenic method was found comparatively to be the best test method for the detection of β lactamase production. However, in contrast to the other two test methods whose reagents can be locally and economically prepared, chromogenic test’s use has been impeded by its cost and unavailability in the local Nepali market.

Crohn's disease complicated by intestinal infection with methicillin-resistant Staphylococcus aureus

We report on a 24-year-old male patient with history of bloody diarrhea, abdominal pain and vomiting. Endoscopy revealed massive ulcerative discontinuous proctosigmoiditis with deep, sharply demarcated epithelial denudations and enterotoxigenic methicillin-resistant Staphylococcus aureus (MRSA) was detected in mucosal biopsies. After treatment with linezolide and steroids, a significant amelioration of colitis was detected and testing for MRSA became negative. In face of the case presented here, we suggest that in patients with refractory inflammatory bowel disease (IBD), microbiological assessment should be performed to detect a possible Staphylococcus aureus infection in order to initiate an antimicrobial treatment in addition to IBDspecific treatment.

Development of a Duplex Real-Time PCR Method for the Pharmaceutical Rapid Microbial Detection of <i>Staphylococcus aureus</i>and <i>Pseudomonas aeruginosa</i>

Objective: To develop a duplex real-time PCR assay for pharmaceutical rapid microbial detection of Staphylococcus aureus and Pseudomonas aeruginosa. Methods: The specific primers and probes were designed to amplify the femB gene of S. aureus and the DNA gyrase subunit B gene of P. aeruginosa. The sensitivity of the system was detected by a multiple proportional dilution method. In order to examine the specificity of the system, other twenty-one bacteria strains were assayed simultaneously. Results: A highly sensitive and specific duplex real-time PCR assay for the detection of S. aureus and P. aeruginosa was established. The sensitivity was 50 copies/μL. The specificity was 100%. The whole detection procedure can be finished within 2.5 h. Conclusion: The duplex real-time PCR method is efficient in detecting with good sensitivity and specificity. There is a good prospect of this method applying in disease prevention and pharmaceutical industry due to the simultaneous detection of two pathogens.

Prevalence of Panton Valentine Leukocidin in Carriage and Infective Strains of <i>Staphylococcus aureus</i>at a Referral Hospital in Kenya

Panton valentine leukocidin (PVL) is a pore forming exotoxin that is expressed by some Staphylococcus aureus (S. aureus) strains and is thought to add to its virulence. The prevalence of PVL in carriage and disease causing strains varies considerably from region to region. This study compared the prevalence of the PVL gene in S. aureus isolates obtained from healthcare workers and from patients seen at the Aga Khan University Hospital Nairobi (AKUHN). S. aureus isolates obtained from healthcare workers and patients attended to at AKUHN between July 2010 and March 2011 were used for this study. Forty five S. aureus isolates from healthcare workers and 63 from clinical specimens obtained from 59 patients were analysed for the PVL gene. The prevalence of PVL in isolates from healthcare workers was 24.4% compared to 39.7% in the isolates causing infection (P = 0.098). PVL prevalence was 58.8% in S. aureus isolates obtained from skin and soft tissue infections (SSIs) compared to 25.0% in carriage isolates (P = 0.002, OR 4.29). Prevalence in isolates from invasive infections was 11.1%. Patients with PVL positive S. aureus were younger than those with PVL negative isolates (P = 0.082). The high prevalence of PVL is comparable with that reported in other African countries. The significance of the high prevalence of PVL in S.aureus isolates carried by health care workers at AKUHN is unclear at the moment. PVL prevalence is significantly higher in S. aureus isolates causing SSIs compared to carriage and invasive isolates.