BackgroundThe ideal identification of Staphylococcus aureus clinical isolates requires a battery of tests and this is costly in resource limited settings. In many developing countries, the tube coagulase test is usually confirmatory for S. aureus and is routinely done using either human or sheep plasma. This study evaluated Mannitol salt agar and the deoxyribonuclease (DNase) test for improving the efficiency of the tube coagulase test in resource limited settings. The efficiency of human and sheep plasma with tube coagulase tests was also evaluated.MethodsOne hundred and eighty Gram positive, Catalase positive cocci occurring in pairs, short chains or clusters were subjected to growth on Mannitol salt agar, deoxyribonuclease and tube coagulase tests. Of these, isolates that were positive for at least two of the three tests (n = 60) were used to evaluate the performance of the tube coagulase test for identification of S. aureus, using PCR-amplification of the nuc gene as a gold standard.ResultsHuman plasma was more sensitive than sheep plasma for the tube coagulase test (sensitivity of 91% vs. 81% respectively), but both plasmas had very low specificity (11% and 7% respectively). The sensitivity and specificity of the tube coagulase test (human plasma) was markedly improved when Mannitol salt agar and DNase were introduced as a tri-combination test for routine identification of Staphylococcus aureus (100% specificity and 75% sensitivity). The specificity and sensitivity of Mannitol salt agar/DNase/tube coagulase (sheep plasma) combination was 100% and 67%, respectively.ConclusionThe efficiency of the tube coagulase test can be markedly improved by sequel testing of the isolates with Mannitol salt agar, DNase and Tube coagulase. There is no single phenotypic test (including tube coagulase) that can guarantee reliable results in the identification of Staphylococcus aureus.

BackgroundIdentification of pathogens associated with bovine mastitis is helpful in treatment and management decisions. However, such data from sub-Saharan Africa is scarce. Here we describe the distribution and antimicrobial susceptibility patterns of bacteria from cows with clinical mastitis in Kampala, Uganda. Due to high concern of zoonotic infections, isolates from milkmen are also described.Methodology/Principal FindingsNinety seven milk samples from cows with clinical mastitis and 31 nasal swabs from milkmen were collected (one sample per cow/human). Fifty eight (60%) Gram-positive isolates namely Staphylococci (21), Enterococci (16), Streptococci (13), Lactococci (5), Micrococci (2) and Arcanobacteria (1) were detected in cows; only one grew Staphylococcus aureus. Furthermore, 24 (25%) coliforms namely Escherichia coli (12), Klebsiella oxytoca (5), Proteus vulgaris (2), Serratia (2), Citrobacter (1), Cedecea (1) and Leclercia (1) were identified. From humans, 24 Gram-positive bacteria grew, of which 11 were Staphylococci (35%) including four Staphylococcus aureus. Upon susceptibility testing, methicillin-resistant coagulase-negative staphylococci (CoNS) were prevalent; 57%, 12/21 in cows and 64%, 7/11 in humans. However, methicillin-resistant Staphylococcus aureus was not detected. Furthermore, methicillin and vancomycin resistant CoNS were detected in cows (Staphylococcus hominis, Staphylococcus lugdunensis) and humans (Staphylococcus scuiri). Also, vancomycin and daptomycin resistant Enterococci (Enterococcus faecalis and Enterococcus faecium, respectively) were detected in cows. Coliforms were less resistant with three pan-susceptible isolates. However, multidrug resistant Klebsiella, Proteus, Serratia, Cedecea, and Citrobacter were detected. Lastly, similar species grew from human and bovine samples but on genotyping, the isolates were found to be different. Interestingly, human and bovine Staphylococcus aureus were genetically similar (spa-CC435, spa-type t645 corresponding to ST121) but with different susceptibility patterns.Conclusions/SignificanceCoNS, Enterococci, Streptococci, and Escherichia coli are the predominant pathogens associated with clinical bovine-mastitis in Kampala, Uganda. Multidrug resistant bacteria are also prevalent. While similar species occurred in humans and cows, transmission was not detected.

BackgroundThe prevalence of Methicillin resistant Staphylococcus aureus (MRSA) is progressively increasing globally with significant regional variation. Understanding the Staphylococcus aureus lineages is crucial in controlling nosocomial infections. Recent studies on S. aureus in Uganda have revealed an escalating burden of MRSA. However, the S. aureus genotypes circulating among patients are not known. Here, we report S. aureus lineages circulating in patients with surgical site infections (SSI) at Mulago National hospital, Kampala, Uganda.MethodsA cross-sectional study involving 314 patients with SSI at Mulago National Hospital was conducted from September 2011 to April 2012. Pus swabs from the patients’ SSI were processed using standard microbiological procedures. Methicillin sensitive Staphylococcus aureus (MSSA) and MRSA were identified using phenotypic tests and confirmed by PCR-detection of the nuc and mecA genes, respectively. SCCmec genotypes were determined among MRSA isolates using multiplex PCR. Furthermore, to determine lineages, spa sequence based-genotyping was performed on all S. aureus isolates.ResultsOf the 314 patients with SSI, S. aureus accounted for 20.4% (64/314), of which 37.5% (24/64) were MRSA. The predominant SCCmec types were type V (33.3%, 8/24) and type I (16.7%, 4/24). The predominant spa lineages were t645 (17.2%, 11/64) and t4353 (15.6%, 10/64), and these were found to be clonally circulating in all the surgical wards. On the other hand, lineages t064, t355, and t4609 were confined to the obstetrics and gynecology wards. A new spa type (t10277) was identified from MSSA isolate. On multivariate logistic regression analysis, cancer and inducible clindamycin resistance remained as independent predictors of MRSA-SSI.ConclusionSCCmec types I and V are the most prevalent MRSA mecA types from the patients’ SSI. The predominant spa lineages (t645 and t4353) are clonally circulating in all the surgical wards, calling for strengthening of infection control practices at Mulago National Hospital.

BackgroundThere is limited data on Methicillin resistant Staphylococcus aureus (MRSA) in Uganda where, as in most low income countries, the routine use of chromogenic agar for MRSA detection is not affordable. We aimed to determine MRSA prevalence among patients, healthcare workers (HCW) and the environment in the burns units at Mulago hospital, and compare the performance of CHROMagar with oxacillin for detection of MRSA.ResultsOne hundred samples (from 25 patients; 36 HCW; and 39 from the environment, one sample per person/item) were cultured for the isolation of Staphylococcus aureus. Forty one S. aureus isolates were recovered from 13 patients, 13 HCW and 15 from the environment, all of which were oxacillin resistant and mecA/femA/nuc-positive. MRSA prevalence was 46% (41/89) among patients, HCW and the environment, and 100% (41/41) among the isolates. For CHROMagar, MRSA prevalence was 29% (26/89) among patients, HCW and the environment, and 63% (26/41) among the isolates. There was high prevalence of multidrug resistant isolates, which concomitantly possessed virulence and antimicrobial resistance determinants, notably biofilms, hemolysins, toxin and ica genes. One isolate positive for all determinants possessed the bhp homologue which encodes the biofilm associated protein (BAP), a rare finding in human isolates. SCCmec type I was the most common at 54% prevalence (22/41), followed by SCCmec type V (15%, 6/41) and SCCmec type IV (7%, 3/41). SCCmec types II and III were not detected and 10 isolates (24%) were non-typeable.ConclusionsHyper-virulent methicillin resistant Staphylococcus aureus is prevalent in the burns unit of Mulago hospital.

BackgroundMultidrug resistant Pseudomonas aeruginosa and Acinetobacter species are common causes of nosocomial infections worldwide. Recently we reported the occurrence of carbapenem resistant Enterobacteriaceae, P. aeruginosa and Acinetobacter species at Mulago National Referral Hospital in Kampala, Uganda, but the isolates were not analyzed for genetic relatedness. Herein we report the intra-species genotypic diversity among P. aeruginosa and Acinetobacter baumannii isolated from hospitalized patients and the environment at Mulago Hospital, using repetitive elements-based PCR (Rep-PCR) genotyping.ResultsA total of 736 specimens from hospitalized patients were processed for culture and sensitivity testing yielding 9 (1.2%) P. aeruginosa and 7 (0.95%) A. baumannii. Similarly, 100 samples from the hospital environment were processed yielding 33 (33%) P. aeruginosa and 13 (13%) A. baumannii. Altogether, 62 non-repetitive isolates were studied (42 P. aeruginosa and 20 A. baumannii), of which 38% (16/42) P. aeruginosa and 40% (8/20) A. baumannii were multidrug resistant (isolates resistant to three or more classes of antimicrobials). Carbapenem resistance prevalence was 33 and 21% for P. aeruginosa from patients and the environment, respectively, while it was 14 and 86% for A. baumannii from patients and environment, respectively. Cluster analysis of the Rep-PCR fingerprints revealed a high level of genetic diversity among the isolates within each species as few isolates were clustered (at 100% level of similarity). More to this, the clustered isolates revealed a complex nature of multidrug resistant P. aeruginosa and A. baumannii clones circulating at Mulago Hospital. Importantly, certain isolates from the environment and patients were clustered, implying that hospitalized patients at Mulago were probably infected with strains from the environment.ConclusionsThe prevalence of multidrug resistant P. aeruginosa and A. baumannii is high at Mulago Hospital but carbapenem resistance prevalence remains relatively low in isolates from hospitalized patients. Importantly, the prevalence of carbapenem resistance in isolates from the environment is high implying the infection control practices at the hospital might be inadequate.Electronic supplementary materialThe online version of this article (doi:10.1186/s13104-017-2612-y) contains supplementary material, which is available to authorized users.