Prevalence of extended-spectrum ß-lactamase-producing Enterobacterales in retail sheep meat from Zagazig city, Egypt.

BACKGROUND: The goal of this study was to investigate the prevalence of extended-spectrum ß-lactamase production in Enterobacterales isolated from retail sheep meat in Zagazig, Egypt. METHODS: One hundred random samples of sheep meat were collected from different retail butcher shops (n = 5) in the city of Zagazig, Egypt. Bacterial isolates were identified by MALDI-TOF MS and screened for antibiotic susceptibility by disk diffusion; further genotypic characterization of ß-lactamase-encoding genes was performed with Real-Time PCR. E. coli strains were phylotyped with the Clermont triplex PCR method. RESULTS: Of the total of 101 bacterial isolates recovered from retail sheep meat samples, 93 were E. coli, six were Enterobacter cloacae and two were Proteus mirabilis. As many as 17% of these 100 samples showed ESBL phenotypes, all were E. coli. The blaCTX-M genes were detected in seven isolates (six were blaCTX-M-15 and one was blaCTX-M-14), three isolates harboured blaTEM (all were blaTEM-one), and two carried genes of the blaSHV family (both were blaSHV-12). Eight E. coli isolates expressed ESBL phenotype but no blaTEM, blaSHV or blaCTX-M genes were detected by PCR. ESBL- positive E. coli isolates were nearly equally distributed over the commensal groups A/B1 and the virulent group D. CONCLUSION: Nearly one in five sheep meat samples was contaminated with ESBL-E. coli. This further corroborates the potential role played by contaminated meat in the increasing resistance rates that have been reported worldwide.

Prevalence and risk factors for carriage of ESBL-producing Enterobacteriaceae in Amsterdam.

OBJECTIVES: The objectives of this study were to determine the prevalence of carriage of ESBL-producing Enterobacteriaceae (ESBL-E) in a representative sample of the general adult Dutch community, to identify risk factors and to gain understanding of the epidemiology of these resistant strains. METHODS: Adults enrolled in five general practices in Amsterdam were approached by postal mail and asked to fill in a questionnaire and to collect a faecal sample. Samples were analysed for the presence of ESBL-E. ESBL genes were characterized by PCR and sequencing. Strains were typed using MLST and amplified fragment length polymorphism (AFLP) and plasmids were identified by PCR-based replicon typing. Risk factors for carriage were investigated by multivariate analysis. RESULTS: ESBL-E were found in 145/1695 (8.6%) samples; 91% were Escherichia coli. Most ESBL genes were of the CTX-M group (blaCTX-M-1 and blaCTX-M-15). MLST ST131 was predominant and mainly associated with CTX-M-15-producing E. coli. One isolate with reduced susceptibility to ertapenem produced OXA-48. In multivariate analyses, use of antimicrobial agents, use of antacids and travel to Africa, Asia and Northern America were associated with carriage of ESBL-E, in particular strains with blaCTX-M-14/15. CONCLUSIONS: This study showed a high prevalence of ESBL-E carriage in the general Dutch community. Also, outside hospitals, the use of antibiotics was a risk factor; interestingly, use of antacids increased the risk of carriage. A major risk factor in the general population was travel to countries outside Europe, in particular to Asia, Africa and Northern America.

Diagnostic yield of repeat sampling with immunoassay, real-time PCR, and toxigenic culture for the detection of toxigenic Clostridium difficile in an epidemic and a non-epidemic setting.

Current international guidelines lack definite conclusions regarding repeat stool sampling for the detection of toxigenic Clostridium difficile. We assessed the value of repeat sampling and compared the diagnostic yield in an epidemic to a non-epidemic setting. Consecutive fecal samples obtained during two time frames were analyzed using direct stool immunoassay toxin testing (enzyme immunoassay [EIA]), direct stool real-time PCR toxin gene testing, and toxigenic culture. Samples collected within 7 days of the initial sample were considered repeat tests. In the epidemic setting 989 patients were analyzed, and in the non-epidemic setting 1,015. In the epidemic setting 204 patients had two or more specimens included for analysis and in the non-epidemic setting 287 patients. In the epidemic setting 136 samples yielded a positive results, either by EIA or toxigenic culture; of these, 108 were positive according to EIA and 123 according to toxigenic culture. In the first test round 98 (90.7%, 95% CI 85.3 to 96.2), 114 (92.7%, 88.1 to 97.3), and 126 (92.6%, 88.3 to 97.0) positives were detected. Subsequent test rounds yielded 10 (9.3%, 3.8 to 14.7), 9 (7.3%, 2.7 to 11.9), and 10 (7.4%, 3.0 to 11.7) extra positives. In the non-epidemic setting EIA, toxigenic culture and PCR detected 33, 66, and 83 positives. The three tests combined 93 detected positives. In the first test round 30 (90.9%, 81.1 to 100.7), 63 (95.5%, 90.4 to 110.5), 76 (91.6%, 85.6 to 97.5), and 87 (93.5%, 88.6 to 98.5) positives were detected. Subsequent test rounds yielded 3 (9.1%, -0.7 to 18.9), 3 (4.5%, -0.5 to 9.6), 7 (8.4%, 2.5 to 14.4), and 6 (6.5%, 1.5 to 11.4) extra positives. In conclusion, repeat testing resulted in 4.5% to 9.3% extra positives. No significant difference between the settings studied could be demonstrated. Repeat sampling and multimodality testing may be chosen in an outbreak situation to detect all cases, effectively controlling nosocomial spread.

Prevalence of ESBL-producing Enterobacteriaceae in raw vegetables.

To determine whether extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E) are present in retail raw vegetables in Amsterdam, the Netherlands, we collected 119 samples of 15 different types of vegetables from various sources. After culture, strain identification and susceptibility testing, ESBL-encoding genes were characterised by a microarray. Four of the 15 vegetable types were contaminated with ESBL-E. Seven samples (6 %) yielded ESBL-E. Three bla CTX-M-15, one bla CTX-M-1, two genes of the CTX-M-9 group and one SHV ESBL-encoding gene were found. The ESBL genes were similar to what is found in enterobacterial strains from human origin. Therefore, raw vegetables might be a source of resistance genes for the enterobacterial strains found in humans.

Dutch guideline on the laboratory detection of methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) has rapidly emerged worldwide, affecting both healthcare and community settings, and intensive livestock industry. The efficient control of MRSA strongly depends on its adequate laboratory detection. This guideline provides recommendations on the appropriate use of currently available diagnostic laboratory methods for the timely and accurate detection of MRSA in patients and healthcare workers. Herewith, it aims to standardise and improve the diagnostic laboratory procedures that are used for the detection of MRSA in Dutch medical microbiology laboratories.

Strategies to improve the implementation of infection control link nurse programmes in acute-care hospitals.

BACKGROUND: Infection control practitioners face several challenges when implementing infection control link nurse (ICLN) programmes. Identification of strategies to address these can improve the impact of current ICLN programmes and guide their future implementation. AIM: We aimed to identify implementation strategies for ICLN programmes in acute-care hospitals with the Consolidated Framework for Implementation Research (CFIR)-Expert Recommendations for Implementing Change (ERIC) Implementation Strategy Matching tool. METHODS: An expert panel matched 19 implementation and sustainment barriers, identified in our previous studies, to the most fitting CFIR constructs. Subsequently, we applied the CFIR-ERIC Matching Tool and generated a list of implementation strategies to address these barriers. FINDINGS: Barriers were predominantly found within the CFIR domains 'inner setting' (characteristics of the implementing organization) and 'process' (stages of implementation). With the ERIC Matching Tool, we identified the 10 most important strategies to address barriers of implementation of ICLN programmes: identify and prepare champions, conduct local consensus discussions, assess for readiness and identify barriers and facilitators, inform local opinion leaders, use facilitation, create a learning collaborative, conduct local needs assessments, develop a formal implementation blueprint, build a coalition, and identify early adopters. CONCLUSION: The CFIR domains 'inner setting' and 'process' appeared to be the most important to impede implementation of ICLN programmes in acute-care hospitals. Application of the CFIR-ERIC tool highlighted the identification and preparation of champions as the leading strategy for the successful implementation of these programmes. With this tool, strategies can be specifically tailored towards local implementation and sustainment barriers.

Indwelling time of peripherally inserted central catheters and incidence of bloodstream infections in haematology patients: a cohort study.

BACKGROUND: We aimed to assess whether longer indwelling time of peripherally inserted central catheters (PICC) increases risk of central line associated bloodstream infections (CLABSI) in haematology patients. METHODS: Multicentre retrospective cohort study among haematology patients receiving PICCs between 2013 and 2015. Occurrence of CLABSI based on CDC definitions was assessed. We calculated incidence rates, determined risk factors for CLABSI and used Poisson regression models to assess the risk of developing CLABSI as a function of PICC dwell time. We compared diagnoses and treatment characteristics between 2013-2015 and 2015-2020. RESULTS: 455 PICCs placed in 370 patients were included, comprising 19,063 catheter days. Median indwelling time was 26 days (range 0-385) and CLABSI incidence was 4.0 per 1000 catheter days, with a median time to CLABSI of 33 days (range 18-158). Aplastic anaemia (AA) was associated with an increased risk of CLABSI; patients undergoing autologous stem cell transplantation (SCT) were less likely to develop CLABSI. In the unadjusted analysis, PICCs with an indwelling time of 15-28 days, 29-42 days, 43-56 days and > 56 days each had an increased CLABSI incidence rate ratio of 2.4 (1.2-4.8), 2.2 (0.95-5.0), 3.4 (1.6-7.5) and 1.7 (0.9-3.5), respectively, compared to PICCs in place for < 15 days. However, after adjusting for AA and SCT, there was no significant difference in incidence rates between dwell times (p 0.067). CONCLUSIONS: Our study shows that risk of CLABSI does not appear to increase with longer PICC indwelling time. Routine replacement of PICCs therefore is unlikely to prevent CLABSI in this population.

IS-pro: high-throughput molecular fingerprinting of the intestinal microbiota.

The human intestinal microbiota is known to play an important role in human health and disease, and with the advent of novel molecular techniques, disease-specific variations in its composition have been found. However, analysis of the intestinal microbiota has not yet been applicable in large-scale clinical research or routine diagnostics because of the complex and expensive nature of the techniques needed. Here, we describe a new PCR-based profiling technique for high-throughput analysis of the human intestinal microbiota, which we have termed IS-pro. This technique combines bacterial species differentiation by the length of the 16S-23S rDNA interspace region with instant taxonomic classification by phylum-specific fluorescent labeling of PCR primers. We validated IS-pro in silico, in vitro, and in vivo, on human colonic biopsies and feces, and introduced a standardized protocol for data analysis. IS-pro is easy to implement in general clinical microbiological laboratories with access to capillary gel electrophoresis, and the high-throughput nature of the test makes analysis of large numbers of samples feasible. This combination renders IS-pro ideally suited for use in clinical research and routine diagnostics.

Medical-grade honey enriched with antimicrobial peptides has enhanced activity against antibiotic-resistant pathogens.

Honey has potent activity against both antibiotic-sensitive and -resistant bacteria, and is an interesting agent for topical antimicrobial application to wounds. As honey is diluted by wound exudate, rapid bactericidal activity up to high dilution is a prerequisite for its successful application. We investigated the kinetics of the killing of antibiotic-resistant bacteria by RS honey, the source for the production of Revamil® medical-grade honey, and we aimed to enhance the rapid bactericidal activity of RS honey by enrichment with its endogenous compounds or the addition of antimicrobial peptides (AMPs). RS honey killed antibiotic-resistant isolates of Pseudomonas aeruginosa, Staphylococcus epidermidis, Enterococcus faecium, and Burkholderia cepacia within 2 h, but lacked such rapid activity against methicillin-resistant S. aureus (MRSA) and extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli. It was not feasible to enhance the rapid activity of RS honey by enrichment with endogenous compounds, but RS honey enriched with 75 µM of the synthetic peptide Bactericidal Peptide 2 (BP2) showed rapid bactericidal activity against all species tested, including MRSA and ESBL E. coli, at up to 10-20-fold dilution. RS honey enriched with BP2 rapidly killed all bacteria tested and had a broader spectrum of bactericidal activity than either BP2 or honey alone.

Microscopic detection of viable Staphylococcus epidermidis in peri-implant tissue in experimental biomaterial-associated infection, identified by bromodeoxyuridine incorporation.

Infection of biomedical devices is characterized by biofilm formation and colonization of surrounding tissue by the causative pathogens. To investigate whether bacteria detected microscopically in tissue surrounding infected devices were viable, we used bromodeoxyuridine (BrdU), a nucleotide analogue that is incorporated into bacterial DNA and can be detected with antibodies. Infected human tissue was obtained postmortem from patients with intravascular devices, and mouse biopsy specimens were obtained from mice with experimental biomaterial infection. In vitro experiments showed that Staphylococcus epidermidis incorporated BrdU, as judged from staining of the bacteria with anti-BrdU antibodies. After incubation of bacteria with BrdU and subsequent staining of microscopic sections with anti-BrdU antibodies, bacteria could be clearly visualized in the tissue surrounding intravascular devices of deceased patients. With this staining technique, relapse of infection could be visualized in mice challenged with a low dose of S. epidermidis and treated with dexamethasone between 14 and 21 days after challenge to suppress immunity. This confirms and extends our previous findings that pericatheter tissue is a reservoir for bacteria in biomaterial-associated infection. The pathogenesis of the infection and temporo-spatial distribution of viable, dividing bacteria can now be studied at the microscopic level by immunolabeling with BrdU and BrdU antibodies.

The mannose cap of mycobacterial lipoarabinomannan does not dominate the Mycobacterium-host interaction.

Pathogenic mycobacteria have the ability to persist in phagocytic cells and to suppress the immune system. The glycolipid lipoarabinomannan (LAM), in particular its mannose cap, has been shown to inhibit phagolysosome fusion and to induce immunosuppressive IL-10 production via interaction with the mannose receptor or DC-SIGN. Hence, the current paradigm is that the mannose cap of LAM is a crucial factor in mycobacterial virulence. However, the above studies were performed with purified LAM, never with live bacteria. Here we evaluate the biological properties of capless mutants of Mycobacterium marinum and M. bovis BCG, made by inactivating homologues of Rv1635c. We show that its gene product is an undecaprenyl phosphomannose-dependent mannosyltransferase. Compared with parent strain, capless M. marinum induced slightly less uptake by and slightly more phagolysosome fusion in infected macrophages but this did not lead to decreased survival of the bacteria in vitro, nor in vivo in zebra fish. Loss of caps in M. bovis BCG resulted in a sometimes decreased binding to human dendritic cells or DC-SIGN-transfected Raji cells, but no differences in IL-10 induction were observed. In mice, capless M. bovis BCG did not survive less well in lung, spleen or liver and induced a similar cytokine profile. Our data contradict the current paradigm and demonstrate that mannose-capped LAM does not dominate the Mycobacterium-host interaction.

Mannose-binding lectin (MBL) genotype in relation to risk of nosocomial infection in pre-term neonates in the neonatal intensive care unit.

Mannose-binding lectin (MBL) plays an important role in the innate immune response. Three alleles in the MBL gene, and one allele of the promoter, independently cause low serum MBL levels as compared with the wild-type. This study investigated the relationship between MBL genotype and the occurrence of nosocomial infection among neonates in a neonatal intensive care unit (NICU). Prospectively gathered information concerning nosocomial infection was available for 742 neonates from a recently performed surveillance study in an NICU. DNA was isolated from Guthriecards for a subgroup of 204 neonates who stayed in the NICU for > or =4 days. After a pre-PCR for the MBL gene in blood spots on Guthriecards, mutations were analysed by real-time PCR to detect six mutations in the MBL gene. An MBL genotype could be determined for 186 neonates. As compared to term neonates, genotypes encoding MBL-deficient haplotypes were significantly more prevalent among pre-term neonates. Forty-one of these neonates developed sepsis, with blood cultures yielding coagulase-negative staphylococci in 25 cases. Pneumonia occurred in 30 cases, with various causative organisms. No relationship was found between MBL genotype and the risk of nosocomial sepsis or pneumonia, even after correction for birth-weight, perhaps because of an insufficient correlation between genotype and the concentration of functional MBL. In addition, most bloodstream infections in the NICU were caused by coagulase-negative staphylococci, to which MBL binds poorly.

[Optimisation of the antibiotic policy in the Netherlands. XII. The SWAB guideline for antimicrobial eradication of MRSA in carriers]. / Optimaliseren van het antibioticabeleid in Nederland. XII. SWAB-richtlijn voor de behandeling van MRSA-dragerschap.

The 'Stichting Werkgroep Antibioticabeleid' (SWAB; Dutch Working Party on Antibiotics Policy) has developed evidence-based guidelines for the antimicrobial treatment of methicillin-resistant Staphylococcus aureus (MRSA) carriers for the eradication of MRSA. A distinction was made between uncomplicated and complicated carriage depending on the presence or absence of an active MRSA infection, skin lesions, foreign body material, mupirocin resistance and/or extranasal carriage. The indication for treatment is determined by the consequences of carriage for the carrier and his/her environment, the adverse events of treatment, and the likelihood of a successful treatment. The first choice of treatment in uncomplicated carriers is a combination of mupirocin nasal ointment and disinfectant soap for 5 days, along with hygiene advice. If treatment fails, sources in the vicinity of the patient must be sought. Complicated carriers receive a combination of 2 oral antibiotics, in addition to mupirocin nasal ointment and disinfectant soap, for at least 7 days.

[Bacteriophages in the battle against multidrug resistant bacteria]. / Bacteriofagen in de strijd tegen multiresistente bacteriën.

Bacteriophages are viruses that infect bacteria. They are highly specific for a bacterial species. The so-called 'lytic phages' can lyse bacteria when they infect them; these phages can be used to treat bacterial infections. Despite a century of experience with phage therapy, the evidence for clinical efficacy is limited. Side effects are generally considered to be mild. The selection, preparation and administration of phages for therapy is laborious, and investigations into the clinical benefits are not easy. More research is needed, also in the face of the increasing antimicrobial resistance.

Host factors are more important in predicting recurrent Clostridium difficile infection than ribotype and use of antibiotics.

OBJECTIVE: A frequent complication of Clostridium difficile infection (CDI) is recurrent disease. The aim of this study was to determine whether early recurrence risk was higher after infection with ribotype 027 (outbreak strain) compared with infection with endemic strain types of C. difficile. METHODS: Consecutive patients diagnosed with CDI between May 2013 and March 2014 were included (outbreak strain, and non-outbreak strains). Patients who developed recurrent CDI within 30 days after completion of CDI treatment, were compared with patients without a recurrence. Medical charts were reviewed for demographic and clinical characteristics. General practitioners were contacted to complete data about the occurrence of recurrent CDI, and the use of medication after hospital discharge. RESULTS: In total, 135 patients were at risk for the development of recurrent CDI; 74 patients were infected by ribotype 027, and 61 patients by other ribotypes. Thirty-nine patients (29%) developed recurrent CDI within 30 days after completion of CDI treatment. In multivariable analysis, age ≥70 years (HR 3.05, 95% CI 1.54-6.03), and a duration of CDI treatment ≥11 days (HR 1.92, 95% CI 1.00-3.69) were clearly associated with recurrence; infection with ribotype 027 showed a HR of 1.72 (95% CI 0.88-3.33). CONCLUSION: During this outbreak of C. difficile in a tertiary care centre, age and a prolonged duration of CDI therapy (which is most likely a marker of underlying disease severity) were the main risk factors for recurrent CDI. This points to host factors as more important predictors for recurrent CDI than strain type or antibiotic use.

Nudging to improve hand hygiene.

BACKGROUND: Hand hygiene is paramount to prevent healthcare-associated infections, but improving compliance is challenging. When healthcare workers seldom encounter healthcare-associated infections, they will consider the odds of causing infections through poor hand hygiene negligible. Cognitive biases such as these may induce non-compliance. Nudging, 'a friendly push to encourage desired behaviour', could provide an easily implemented, inexpensive measure to address cognitive biases and thus support hand hygiene interventions. AIM: To investigate whether behavioural nudges, displayed as posters, can increase the use of alcohol-based hand rub. METHODS: We developed nudges based on a systematic review of previously described cognitive biases, and tested these through a cross-sectional survey among the target audience. We then conducted a controlled before-after trial on two hospital wards, to assess the effect of these nudges on the use of alcohol-based hand rub, measured with electronic dispensers. FINDINGS: Poisson regression analyses adjusted for workload showed that nudges displayed next to dispensers increased their overall use on one ward [poster 1: relative risk: 1.6 (95% confidence interval: 1.2-2.2); poster 2: 1.7 (1.2-2.5)] and during doctor's rounds on both wards [poster 1: ward A: 1.7 (1.1-2.6); ward B: 2.2 (1.3-3.8)]. Use of dispensers without adjacent nudges did not increase. CONCLUSION: Nudges based on cognitive biases that play a role in hand hygiene, and displayed as posters, could provide an easy, inexpensive measure to increase use of alcohol-based hand rub. When applying nudges to change behaviour, it is important to identify the right nudge for the right audience.

Levofloxacin vs. ciprofloxacin plus phenethicillin for the prevention of bacterial infections in patients with haematological malignancies.

An open-label randomised clinical trial was designed to compare the efficacy and tolerance of levofloxacin and ciprofloxacin plus phenethicillin for the prevention of bacterial infections in patients with high-risk neutropenia, and to monitor the emergence of antimicrobial resistance. Adult patients (n = 242) scheduled to receive intensive treatment for haematological malignancies were assigned randomly to receive oral prophylaxis with either levofloxacin 500 mg once-daily (n = 122), or ciprofloxacin 500 mg twice-daily plus phenethicillin 250 mg four-times-daily (n = 120). The primary endpoint was failure of prophylaxis, defined as the first occurrence of either the need to change the prophylactic regimen or the initiation of intravenous broad-spectrum antibiotics. This endpoint was observed in 89 (73.0%) of 122 levofloxacin recipients and in 85 (70.8%) of 120 ciprofloxacin plus phenethicillin recipients (RR 1.03, 95% CI 0.88-1.21, p 0.71). No differences were noted between the two groups with respect to secondary outcome measures, including time to endpoint, occurrence of fever, type and number of microbiologically documented infections, and administration of intravenous antibiotics. A questionnaire revealed that levofloxacin was tolerated significantly better than ciprofloxacin plus phenethicillin. Surveillance cultures indicated the emergence of viridans group (VG) streptococci resistant to levofloxacin in 17 (14%) of 122 levofloxacin recipients; in these cases, the prophylactic regimen was adjusted. No bacteraemia with VG streptococci occurred. It was concluded that levofloxacin and ciprofloxacin plus phenethicillin are equally effective in the prevention of bacterial infections in neutropenic patients, but that levofloxacin is tolerated better. Emergence of levofloxacin-resistant VG streptococci is of concern, but appears to be a manageable problem.

How many infection control staff do we need in hospitals?

During a one-day workshop experienced infection control practitioners (ICPs) and medical microbiologists debated how much time was needed for the delivery of infection control activities in a model hospital. They agreed a standard of one full-time equivalent (FTE) ICP per 178 hospital beds and one FTE medical microbiologist per 806 hospital beds. This is 40% and 24% more than the usual standard, respectively. Now that official numbers of hospital beds have become an inadequate parameter for work delivered by hospitals, a new standard is proposed, with the number of admissions as the denominator. This is one FTE ICP per 5000 admissions and one medical microbiologist or epidemiologist per 25000 admissions.

[Methicillin-resistant Staphylococcus aureus (MRSA) in the community]. / Meticillineresistente Staphylococcus aureus (MRSA) in de gemeenschap.

Methicillin-resistant Staphylococcus aureus (MRSA) infections have been confined to healthcare centres for decades. However, MRSA infections are increasingly seen in young healthy individuals with no exposure to healthcare centres. These community-acquired MRSA (CA-MRSA) strains differ from healthcare-associated MRSA (HA-MRSA) strains in various ways. For example, CA-MRSA is strongly associated with the staphylococcal cassette chromosome mec (SCCmec) type IV and the toxin Panton-Valentine leukocidin. CA-MRSA spreads relatively easily but often remains susceptible to non-3-lactam antibiotics. Given the epidemic potential of CA-MRSA strains, there is a high probability that the number of CA-MRSA infections will increase in The Netherlands. In order to prevent and control CA-MRSA outbreaks in the community successfully, the restrictive Dutch antibiotic policy must be followed with strict infection prevention measures.

[Horizontal transfer of bacterial genes and its significance for antibiotic resistance and pathogenicity]. / Horizontale overdracht van bacteriële genen en de betekenis voor antibioticaresistentie en pathogeniteit.

* Sexual reproduction does not occur in bacteria. The point of departure in bacterial reproduction is always that one individual divides itself into two identical descendants. * In the bacterial world, however, there is certainly exchange of hereditary characteristics (DNA). This type of exchange is called horizontal gene transfer. * There are 3 basic ways for the exchange of DNA between bacteria: conjugation, transduction and natural transformation. Each of these has its specific impact on the species. * During conjugation, a piece of DNA is copied in one bacterium and transferred to another via a temporary connection, a conjugative pilus. In this way, for example, a particular gene that codes for resistance against antibiotics can be transmitted. * In transduction, the transfer of DNA takes place with the aid of bacteriophages. The gene that codes for the toxin produced by Vibrio cholerae is spread by transduction. * In transformation, DNA that is located outside the cell is fragmented and imported into the cell, after which, via recombination, the DNA replaces a piece of original DNA in the chromosome of the host. Transformation is responsible for, among other things, antigen variation in the pneumococcal capsule. Antigen variation helps the pneumococci to resist the immune response leading to the forming of antibodies and adequate opsonisation.