Emergence of multidrug-resistant gram-negative organisms in a neonatal unit and the therapeutic implications

Neonatal mortality during the war in Tigray: a cross-sectional community-based study

BACKGROUND

Neonatal mortality is among the key national and international indicators of health services. The global Sustainable Development Goal target for neonatal mortality is fewer than 12 deaths per 1000 livebirths, by 2030. Neonatal mortality estimates in the 2019 Ethiopian Demographic Health Survey found 25·7 deaths per 1000 livebirths. Subnational surveys specific to Tigray, Ethiopia, reported a neonatal mortality lifetime prevalence of 7·13 deaths. Another government report from the Tigray region estimated a neonatal mortality rate of ten deaths per 1000 livebirths in 2020. Despite the numerous interventions in Ethiopia's Tigray region to achieve the Sustainable Development Goals, the war has disrupted most health services, but the effect on neonatal mortality is unknown. Thus, this study aimed to investigate the magnitude and causes of neonatal mortality during the war in Tigray.

METHODS

A cross-sectional community-based study was conducted in Tigray to evaluate neonatal mortality that occurred from Nov 4, 2020, to May 30, 2022. Among the 31 districts, 121 tabias were selected using computer-generated random sampling, and 189 087 households were visited. We adopted a validated WHO 2022 verbal autopsy tool, and data were collected using an interviewer-administrated Open Data Kit. In the absence of the mother, other respondents to the verbal autopsy interview were household members aged 18 years and older who provided care during the final illness that led to death.

FINDINGS

29 761 livebirths were recorded during the screening of 189 087 households. Verbal autopsy was administered for 1158 households with neonatal deaths. 317 neonates were stillborn, and 841 neonatal deaths were recorded with the WHO 2022 verbal autopsy tool from Nov 4, 2020, to May 30, 2022, in 31 districts. The neonatal mortality rate was 28·2 deaths per 1000 livebirths. 476 (57%) of the 841 neonatal deaths occurred at home and 296 (35%) in health facilities. A high rate of neonatal deaths was reported in rural districts (80% [673 of 841]) compared with urban districts (20% [168 of 841]), and 663 (79%) deaths occurred during the early neonatal period, in the first week of life (0-6 days). The leading causes of neonatal death were asphyxia (35% [291 of 834]), prematurity (30% [247 of 834]), and infection (12% [104 of 834]). Asphyxia (37% [246 of 663]) and infection (28% [50 of 178]) were the leading causes of death for early and late neonatal period deaths, respectively.

INTERPRETATION

Neonatal mortality in Tigray is high due to preventable causes. An urgent response is needed to prevent the high number of neonatal deaths associated with the depleted health resources and services resulting from the war, and to achieve the Sustainable Development Goal on neonatal mortality.

FUNDING

UNICEF and United Nations Fund for Population Activities.

TRANSLATION

For the Tigrigna translation of the abstract see Supplementary Materials section.

Bacterial Aetiology of Neonatal Sepsis and Antimicrobial Resistance Pattern at the Regional Referral Hospital, Dar es Salam, Tanzania; A Call to Strengthening Antibiotic Stewardship Program

The diagnosis of neonatal sepsis in lower-income countries is mainly based on clinical presentation. The practice necessitates empirical treatment with limited aetiology and antibiotic susceptibility profile knowledge, prompting the emergence and spread of antimicrobial resistance. We conducted a cross-sectional study to determine the aetiology of neonatal sepsis and antimicrobial resistance patterns. We recruited 658 neonates admitted to the neonatal ward with signs and symptoms of sepsis and performed 639 automated blood cultures and antimicrobial susceptibility testing. Around 72% of the samples were culture positive; Gram-positive bacteria were predominantly isolated, contributing to 81%. Coagulase-negative Staphylococci were the most isolates, followed by Streptococcus agalactiae. Overall, antibiotic resistance among Gram-positive pathogens ranged from 23% (Chloramphenicol) to 93% (Penicillin) and from 24.7% (amikacin) to 91% (ampicillin) for Gram-negative bacteria. Moreover, about 69% of Gram-positive and 75% of Gram-negative bacteria were multidrug-resistant (MDR). We observed about 70% overall proportion of MDR strains, non-significantly more in Gram-negative than Gram-positive pathogens (p = 0.334). In conclusion, the pathogen causing neonatal sepsis in our setting exhibited a high resistance rate to commonly used antibiotics. The high rate of MDR pathogens calls for strengthening antibiotic stewardship programs.

Healthcare-associated Infections in Very Low Birth-weight Infants in a South African Neonatal Unit: Disease Burden, Associated Factors and Short-term Outcomes

BACKGROUND

Infection is a leading cause of death among very low birth-weight (VLBW) infants in resource-limited settings.

METHODS

We performed a retrospective review of healthcare-associated infection (HAI) episodes among VLBW infants from January 1, 2016, to December 31, 2017. The epidemiology, causative organisms and short-term outcomes were analyzed. Logistic regression was used to investigate for factors associated with development of HAI.

RESULTS

During the study period, 715 VLBW infants with suspected HAI were investigated, including 162/715 (22.7%) proven and 158/715 (22.1%) presumed HAI. Of the proven infections, 99/162 (61.1%) contained at least one Gram-negative organism per blood culture; 84/162 (51.9%) single Gram-negative organisms and 15/162 (9.3%) polymicrobial growth. Independent factors associated with development of any HAI included low gestational age, small for gestational age, indwelling central venous catheter and invasive ventilation. Compared with infants in whom HAI had been excluded, infants with HAI were more likely to be diagnosed with necrotizing enterocolitis (5.6% vs. 23.1%; P < 0.001) and bronchopulmonary dysplasia (1.0% vs. 4.4%; P = 0.007). Infants with any HAI also had a longer hospital stay [44 (25-65) vs. 38 (26-53) days; P < 0.001] and increased mortality [90/320 (28.1%) vs. 21/395 (5.3%); P < 0.001] compared with infants who did not develop HAI episodes.

CONCLUSIONS

Proven and presumed HAI are a major contributor to neonatal morbidity and mortality; further research is urgently needed to better understand potential targets for prevention and treatment of HAI in resource-limited neonatal units.

Antibiotic regimens for early-onset neonatal sepsis

BACKGROUND

Neonatal sepsis is a major cause of morbidity and mortality. It is the third leading cause of neonatal mortality globally constituting 13% of overall neonatal mortality. Despite the high burden of neonatal sepsis, high-quality evidence in diagnosis and treatment is scarce. Possibly due to the diagnostic challenges of sepsis and the relative immunosuppression of the newborn, many neonates receive antibiotics for suspected sepsis. Antibiotics have become the most used therapeutics in neonatal intensive care units. The last Cochrane Review was updated in 2004. Given the clinical importance, an updated systematic review assessing the effects of different antibiotic regimens for early-onset neonatal sepsis is needed.

OBJECTIVES

To assess the beneficial and harmful effects of different antibiotic regimens for early-onset neonatal sepsis.

SEARCH METHODS

We searched the following electronic databases: CENTRAL (2020, Issue 8); Ovid MEDLINE; Embase Ovid; CINAHL; LILACS; Science Citation Index EXPANDED and Conference Proceedings Citation Index - Science on 12 March 2021. We searched clinical trials databases and the reference lists of retrieved articles for randomised controlled trials (RCTs) and quasi-RCTs.

SELECTION CRITERIA

We included RCTs comparing different antibiotic regimens for early-onset neonatal sepsis. We included participants from birth to 72 hours of life at randomisation.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed studies for inclusion, extracted data, and assessed risk of bias. We used the GRADE approach to assess the certainty of evidence. Our primary outcome was all-cause mortality, and our secondary outcomes were: serious adverse events, respiratory support, circulatory support, nephrotoxicity, neurological developmental impairment, necrotising enterocolitis, and ototoxicity. Our primary time point of interest was at maximum follow-up.

MAIN RESULTS

We included five RCTs (865 participants). All trials were at high risk of bias. The certainty of the evidence according to GRADE was very low. The included trials assessed five different comparisons of antibiotics. We did not conduct any meta-analyses due to lack of relevant data. Of the five included trials one trial compared ampicillin plus gentamicin with benzylpenicillin plus gentamicin; one trial compared piperacillin plus tazobactam with amikacin; one trial compared ticarcillin plus clavulanic acid with piperacillin plus gentamicin; one trial compared piperacillin with ampicillin plus amikacin; and one trial compared ceftazidime with benzylpenicillin plus gentamicin. None of the five comparisons found any evidence of a difference when assessing all-cause mortality, serious adverse events, circulatory support, nephrotoxicity, neurological developmental impairment, or necrotising enterocolitis; however, none of the trials were near an information size that could contribute significantly to the evidence of the comparative benefits and risks of any particular antibiotic regimen. None of the trials assessed respiratory support or ototoxicity. The benefits and harms of different antibiotic regimens remain unclear due to the lack of well-powered trials and the high risk of systematic errors.

AUTHORS' CONCLUSIONS

Current evidence is insufficient to support any antibiotic regimen being superior to another. Large RCTs assessing different antibiotic regimens in early-onset neonatal sepsis with low risk of bias are warranted.

CRP/albumin ratio: A promising marker of gram-negative bacteremia in late-onset neonatal sepsis

Objective

Neonatal sepsis is a clinical condition that results in serious morbidity and mortality unless urgently diagnosed and treated. Obtaining the results of blood cultures to determine the causative agent in sepsis is a time-consuming process. The CRP/albumin ratio is an inflammatory marker that has started to be used in recent years. The aim of our study was to investigate the relationship between CRP/albumin and Gram-negative bacterial sepsis in neonates.

Material and Methods

This study was conducted on 112 premature neonates with sepsis. The patients were divided into two groups according to culture results as Gram-negative and Gram-positive bacterial sepsis. The laboratory and demographic features of the patients were obtained from the hospital records. A receiver operating characteristic curve was plotted to evaluate the predictive value of the CRP/albumin ratio for Gram-negative sepsis.

Results

CRP/albumin was significantly higher in the Gram-negative group (p<0.001). According to the receiver operating characteristic curve, the optimal cut-off value of CRP/albumin for the prediction of Gram-negative sepsis was >35.17, which had a specificity of 97% and sensitivity of 56% (AUC=0.839; 95% CI: 0.743-0.944; p<0.001). A multivariate logistic regression analysis revealed that CRP/albumin (OR=1.082, 95% CI: 1.033-1.134, p=0.001) and absolute neutrophil count (OR=1.145, 95% CI: 1.000-1.312, p=0.049) were still associated with Gram-negative sepsis after adjustment for variables found to be statistically significant in univariate analysis and correlated with Gram-negative sepsis.

Conclusion

The CRP/albumin ratio is independently related to Gram-negative sepsis in neonatal sepsis and may be useful in predicting Gram-negative bacteremia.

Neonatal sepsis at Mulago national referral hospital in Uganda: Etiology, antimicrobial resistance, associated factors and case fatality risk

Background

Sepsis is the third most common cause of death among neonates, with about 225,000 newborns dying every year globally. Data concerning the microbial etiology of neonatal sepsis and antimicrobial resistance profiles of its causative agents are necessary to inform targeted and effective treatment and prevention strategies.

Objective

To determine the proportion of newborns with symptoms and signs of sepsis who had a positive blood culture, its bacterial etiology, the antimicrobial resistance patterns as well as the factors associated with culture-positivity and case fatality at Mulago national referral hospital in Uganda.

Methods

We conducted a cross-sectional study among 359 neonates with symptoms and signs of sepsis who presented to the pediatric emergency care unit of Mulago national referral hospital from mid-January to end of December 2018. We performed blood culture and antimicrobial susceptibility testing, and conducted polymerase chain reaction to identify methicillin-resistant Staphylococcus aureus (MRSA) isolates. We used multivariable logistic regression to estimate the association between potential risk factors and culture-positive neonatal sepsis.

Findings

Of the 359 neonates recruited, 46 (12.8%; 95% CI 9.5%, 16.7%) had a positive blood culture. The predominant isolated bacteria were Staphylococcus aureus in 29 (63.0%), Escherichia coli in seven (15.2%), and Klebsiella pneumoniae in five (10.9%). Of the 46 pathogens, 73.9% were resistant to ampicillin, 23.9% to gentamicin and 8.7% to ceftriaxone. We isolated MRSA from the blood specimens of 19 (5.3%) of the 359 neonates, while 3 (0.8%) grew extended spectrum beta lactamase producers. The case fatality risk among neonates with neonatal sepsis was 9.5% (95% CI: 6.6%, 13.0%). Cesarean section delivery was strongly associated with culture-positive sepsis (adjusted odds ratio 3.45, 95% CI: 1.2, 10.1).

Conclusion

One in eight neonates with clinical signs of sepsis grew a likely causative bacterial pathogen. S. aureus was the main pathogen isolated and a third of these isolates were MRSA. A significant proportion of the isolated bacterial pathogens were resistant to the first and second line antibiotics used for the treatment of neonatal sepsis. There is need to revisit the current treatment guidelines for neonatal sepsis.

Audit of Antibiotic Prescribing Practices for Neonatal Sepsis and Measurement of Outcome in New Born Unit at Kenyatta National Hospital

Background

Neonatal sepsis is a leading cause of morbidity and mortality globally. A high index of suspicion is required since features of sepsis are nonspecific. Auditing of antibiotic use is necessary to reduce misuse and minimise development of antibiotic resistance.

Objectives

To assess the antibiotic prescribing practices in NBU at KNH against recommended Kenyan guidelines for neonatal sepsis. In addition, outcome within 7 days was described.

Methods

This was a prospective audit of 320 neonates over a 2-month period at NBU of KNH. Data were collected using a structured questionnaire, stored in MS-EXCEL, and analysed using STATA.

Results

Documentation of perinatal risk factors and clinical features at admission and at the time of change of antibiotics was very poor. The rate of investigations to confirm infection was very low. Blood cultures were done only in 13 (4%) neonates on admission, while complete blood count and C reactive protein were done in 224 (70%) and 198 (62%), respectively. Appropriate antibiotics as per the Kenyan guidelines were prescribed in 313 (97.8%) of neonates on admission. However, these were not stopped at 48-72 hours for the 148 (53.62%) who had improved. Overall mortality was high in neonates at 80 (25%). Majority (55%) died within 48 hours. Mortality was high among preterm neonates; 70 (43.8%) died out of 160.

Conclusion

Overall documentation and investigations to confirm infection was poor. The continuation of antibiotics was inappropriate. Overall mortality was high especially in the first 48 hours of admission. To improve documentation, availability of a checklist on admission is recommended.

The pathogenic microbial flora and its antibiotic susceptibility pattern in odontogenic infections

Suppurative head and neck infections of odontogenic origin are the most frequent type of head and neck infections. According to the literature, 7-10% of all antibiotics are currently prescribed for their treatment. Since penicillin was invented, the overall antibiotic sensitivity and resistance pattern of the isolated pathogenic microflora has continuously changed. The response of microorganisms to antibiotics and the development of resistance to their action is a purely evolutive process characterized by genetic mutations, acquisition of genetic material or alteration of gene expression and metabolic adaptations. All this makes challenging and difficult the correct choice of empirical antibiotic treatment for head and neck space infections even today. The aim of this paper was to evaluate the literature and to evidence the most frequent locations of odontogenic head and neck infections, the dominant pathogenic microbial flora, the genetic mutations and metabolic changes necessary for bacteria in order to aquire antibiotic resistance and as well its susceptibility and resistance to common antibiotics. We also aimed to highlight the possible changes in bacterial resistance to antibiotics over time, and to assess whether or not there is a need for fundamental changes in the empirical antibiotic treatment of these infections and show which these would be.

Hand hygiene practices among healthcare workers in a newborn unit of a tertiary referral hospital in Kenya

Background:

Health care-associated infection (HCAI) is a significant cause of morbidity and mortality among hospitalised patients, particularly neonates. Compliance with hand hygiene (HH) recommendations is the simplest and most effective measure in preventing this infection.

Objectives:

To determine the HH practices among healthcare workers (HCWs) in the newborn unit of a tertiary referral hospital in Kenya, their knowledge and perceptions regarding HCAI and importance of HH, and barriers to the recommended HH practices.

Methods:

A descriptive cross-sectional study was conducted to evaluate the HCWs’ compliance with the World Health Organization (WHO) ‘5 Moments for Hand Hygiene’ and a structured self-administered questionnaire adopted from the WHO knowledge and perception of HCW questionnaires was used to answer the secondary objectives.

Results:

The overall HH compliance rate was 15%. HCWs were twice more likely to take a HH action ‘after’ than ‘before’ a patient care procedure (odds ratio [OR] = 2.05; 95% confidence interval [CI] = 1.02–4.19; P = 0.03). Nurses and nursing students had statistically significant lower compliance (OR 0.41; 95% CI = 0.18-0.91; p=0.016) and (OR 0.21; 95% CI = 0.06-0.70; p = 0.004) respectively, compared to the doctors. More than half (52%) of the HCWs were unaware of the five moments/indication for HH. Lack of supplies, forgetfulness and use of gloves were the commonly cited barriers to HH compliance.

Discussion:

HH compliance rate among HCWs in the newborn unit of the tertiary referral hospital was very low. The observed and reported barriers to optimal HH compliance demonstrate a necessity for the adoption of the WHO recommended multimodal HH improvement strategy in this unit.

Molecular epidemiology of Klebsiella pneumoniae invasive infections over a decade at Kilifi County Hospital in Kenya

Multidrug resistant (MDR) Klebsiella pneumoniae is a common cause of nosocomial infections worldwide. Recent years have seen an explosion of resistance to extended-spectrum β-lactamases (ESBLs) and emergence of carbapenem resistance. Here, we examine 198 invasive K. pneumoniae isolates collected from over a decade in Kilifi County Hospital (KCH) in Kenya. We observe a significant increase in MDR K. pneumoniae isolates, particularly to third generation cephalosporins conferred by ESBLs. Using whole-genome sequences, we describe the population structure and the distribution of antimicrobial resistance genes within it. More than half of the isolates examined in this study were ESBL-positive, encoding CTX-M-15, SHV-2, SHV-12 and SHV-27, and 79% were MDR conferring resistance to at least three antimicrobial classes. Although no isolates in our dataset were found to be resistant to carbapenems we did find a plasmid with the genetic architecture of a known New Delhi metallo-β-lactamase-1 (NDM)-carrying plasmid in 25 isolates. In the absence of carbapenem use in KCH and because of the instability of the NDM-1 gene in the plasmid, the NDM-1 gene has been lost in these isolates. Our data suggests that isolates that encode NDM-1 could be present in the population; should carbapenems be introduced as treatment in public hospitals in Kenya, resistance is likely to ensue rapidly.

Etiology, Antibiotic Resistance and Risk Factors for Neonatal Sepsis in a Large Referral Center in Zambia

BACKGROUND

In sub-Saharan Africa, there is scanty data on the causes of neonatal sepsis and antimicrobial resistance among common invasive pathogens that might guide policy and practice.

METHODS

A cross-sectional observational prevalence and etiology study of neonates with suspected sepsis admitted to the neonatal intensive care unit, University Teaching Hospital, Lusaka, Zambia, between October 2013 and May 2014. Data from blood cultures and phenotypic antibiotic susceptibility testing were compared with multivariate analysis of risk factors for neonatal sepsis.

RESULTS

Of 313 neonates with suspected sepsis, 54% (170/313) were male; 20% (62/313) were born to HIV-positive mothers; 33% (103/313) had positive blood cultures, of which 85% (88/103) were early-onset sepsis. Klebsiella species was the most prevalent isolate, accounting for 75% (77/103) of cases, followed by coagulase-negative staphylococci [6% (7/103)], Staphylococcus aureus [6% (6/103)], Escherichia coli [5% (5/103)] and Candida species [5% (5/103)]. For Klebsiella species, antibiotic resistance ranged from 96%-99% for World Health Organization-recommended first-line therapy (gentamicin and ampicillin/penicillin) to 94%-97% for third-generation cephalosporins. The prevalence of culture-confirmed sepsis increased from 0 to 39% during the period December 2013 to March 2014, during which time mortality increased 29%-47%; 93% (14/15) of late-onset sepsis and 82% (37/45) of early-onset sepsis aged 4-7 days were admitted >2 days before the onset of symptoms. Culture results for only 25% (26/103) of cases were available before discharge or death. Maternal HIV infection was associated with a reduced risk of neonatal sepsis [odds ratio, 0.46 (0.23-0.93); P = 0.029].

CONCLUSIONS

Outbreaks of nosocomial multiantibiotic-resistant infections are an important cause of neonatal sepsis and associated mortality. Reduced risk of neonatal sepsis associated with maternal HIV infection is counterintuitive and requires further investigation.

Phenotypic expression and prevalence of ESBL-producing Enterobacteriaceae in samples collected from patients in various wards of Mulago Hospital, Uganda

Background

Resistance to extended-spectrum cephalosporins among Enterobacteriaceae has been reported yet they serve as the last line treatment for severe infections in Uganda and other countries. This resistance often leads to nosocomial infection outbreaks and therapeutic failures from multidrug resistant bacteria. The main objective of this study was to determine the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in clinical samples of patients in various wards of Mulago Hospital; Uganda’s main national referral and teaching hospital.

Methods

This cross-sectional study was conducted between January-April, 2014. Purposive consecutive sampling was used to collect pus swab, urine, blood and CSF samples from patients in the various wards. A total of 245 consecutive, non-repetitive, clinical samples were obtained and tested for phenotypic ESBL production using the Double Disc Synergy Test using cefotaxime, ceftazidime, cefotaxime-clavulanic acid and ceftazidime-clavulanic acid.

Results

Results show that 47 % of the 245 samples had Enterobacteriaceae isolates. Of these isolates 62 % were ESBL producers while 38 % were of non-ESBL phenotype. E. coli was the most isolated organism (53.9 %), followed by K. pneumoniae (28.7 %). Majority of Enterobacteriaceae organisms were isolated from urine samples, followed by pus samples and of these 64.9 % and 47.4 % were ESBL-producers respectively. Klebsiella pneumoniae had the highest percentage of ESBL producers (72.7 %). There was a higher percentage of isolates showing resistance to ceftazidime (73 %) compared to cefotaxime (57.5 %). All Enterobacter cloacae isolates showed resistance to ceftazidime. There were no statistically significant association between phenotype (ESBL/non-ESBL) and patients’ age or gender or Enterobacteriaceae spp.

Conclusions

This study reveals a high prevalence of ESBL producing organisms in Mulago Hospital and high levels of resistance to third generation cephalosporins. In addition to undertaking appropriate infection control measures, there is urgent need for formulation of an antibiotic policy in Uganda to prevent spread of these organisms. This also calls for continuous monitoring and reporting of the presence of such organisms in order to ensure rational and judicious use of antibiotics by clinicians.

Management of neonatal sepsis at Muhimbili National Hospital in Dar es Salaam: diagnostic accuracy of C-reactive protein and newborn scale of sepsis and antimicrobial resistance pattern of etiological bacteria

Background

We determined the accuracy of Rubarth’s newborn scale of sepsis and C- reactive protein in diagnosing neonatal sepsis and assessed antimicrobial susceptibility pattern of etiological bacteria.

Methods

This cross sectional study was conducted at Muhimbili National Hospital in Dar es Salaam, Tanzania between July 2012 and March 2013. Neonates suspected to have sepsis underwent physical examination using Rubarth’s newborn scale of sepsis (RNSOS). Blood was taken for culture and antimicrobial sensitivity testing, full blood picture and C – reactive protein (CRP) performed 12 hours apart. The efficacy of RNSOS and serial CRP was assessed by calculating sensitivity, specificity, negative and positive predictive values, receiver operating characteristics (ROC) analysis as well as likelihood ratios (LHR) with blood culture result used as a gold standard.

Results

Out of 208 blood samples, 19.2% had a positive blood culture. Single CRP had sensitivity and specificity of 87.5% and 70.9% respectively, while RNSOS had sensitivity of 65% and specificity of 79.7%. Serial CRP had sensitivity of 69.0% and specificity of 92.9%. Combination of CRP and RNSOS increased sensitivity to 95.6% and specificity of 56.4%. Combination of two CRP and RNSOS decreased sensitivity to 89.1% but increased specificity to 74%. ROC for CRP was 0.86; and for RNSOS was 0.81.

For CRP the LHR for positive test was 3 while for negative test was 0.18, while for RNSOS the corresponding values were 3.24 and for negative test was 0.43.

Isolated bacteria were Klebsiella spp 14 (35%), Escherichia coli 12 (22.5%), Coagulase negative staphlococci 9 (30%), Staphylococcus aureus 4 (10%), and Pseudomonas spp 1 (2.5%). The overall resistance to the WHO recommended first line antibiotics was 100%, 92% and 42% for cloxacillin, ampicillin and gentamicin, respectively. For the second line drugs resistance was 45%, 40%, and 7% for ceftriaxone, vancomycin and amikacin respectively.

Conclusions

Single CRP in combination with RNSOS can be used for rapid identification of neonates with sepsis due to high sensitivity (95.6%) but cannot exclude those without sepsis due to low specificity (56.4%). Serial CRP done 12hrs apart can be used to exclude non-cases. This study demonstrated very high levels of resistance to the first-line antibiotics.

Measuring antibiotic prescribing in hospitalised children in resource-poor countries: a systematic review

Antibiotic resistance represents a significant threat to global health. Widespread exposure to antibiotics drives the development of antibiotic resistance. Little is known about the exposure to antibiotics of hospitalised children, particularly in resource-poor countries where the burden of infectious disease is highest. The review sought to identify original research quantifying antibiotic use in hospitalised children in resource countries. The methods used were: A systematic search of the MEDLINE, CINAHL, EMBASE, LILACS and African Index Medicus databases. Eighteen papers were identified and the methodology varied considerably. Only seven used a recognised defined daily dose (DDD) methodology. The studies reveal a high exposure of hospitalised children to antibiotics. With the exception of data from China, the studies were limited by their design. Limited evidence of the variation in drug, dose and total exposure to antibiotic use in hospitalised children in resource-poor countries exists. An international network of surveillance of both antimicrobial prescribing and resistance using a simple standardised methodology in this context remains an important goal. A simplified paediatric version of the adult DDD methodology is required to allow international comparison between populations.

Neonatal sepsis at Muhimbili National Hospital, Dar es Salaam, Tanzania; aetiology, antimicrobial sensitivity pattern and clinical outcome

Background

Neonatal sepsis contributes significantly to morbidity and mortality among young infants. The aetiological agents as well as their susceptibility to antimicrobial agents are dynamic. This study determined aetiology, antimicrobial susceptibility and clinical outcome of neonatal sepsis at Muhimbili National Hospital.

Methods

Three hundred and thirty neonates admitted at the Muhimbili National Hospital neonatal ward between October, 2009 and January, 2010 were recruited. Standardized questionnaires were used to obtain demographic and clinical information. Blood and pus samples were cultured on MacConkey, blood and chocolate agars and bacteria were identified based on characteristic morphology, gram stain appearance and standard commercially prepared biochemical tests. Antimicrobial sensitivity testing was performed for ampicillin, cloxacillin, gentamicin, amikacin, cefuroxime and ceftriaxone on Mueller Hinton agar using the Kirby Bauer diffusion method.

Results

Culture proven sepsis was noted in 24% (74/330) of the study participants. Isolated bacterial pathogens were predominantly Staphylococcus aureus, Klebsiella spp and Escherichia coli. Klebsiella spp 32.7% (17/52) was the predominant blood culture isolate in neonates aged below seven days while Staphylococcus aureus 54.5% (12/22) was commonest among those aged above seven days. Staphylococcus aureus was the predominant pus swabs isolate for both neonates aged 0–6 days 42.2% (98/232) and 7–28 days 52.3% (34/65). Resistance of blood culture isolates was high to ampicillin 81.1% (60/74) and cloxacillin 78.4% (58/74), moderate to ceftriaxone 14.9% (11/74) and cefuroxime 18.9% (14/74), and low to amikacin 1.3% (1/74). Isolates from swabs had high resistance to ampicillin 89.9% (267/297) and cloxacillin 85.2 (253/297), moderate resistance to ceftriaxone 38.0% (113/297) and cefuroxime 36.0% (107/297), and low resistance to amikacin 4.7% (14/297). Sepsis was higher in neonates with fever and hypothermia (p=0.02), skin pustules (p<0.001), umbilical pus discharge and abdominal wall hyperemia (p=0.04). Presence of skin pustules was an independent predictor of sepsis OR 0.26, 95% CI (0.10-0.66) p=0.004. The overall death rate was 13.9% (46/330), being higher in neonates with sepsis 24.3% (18/74) than those without 10.9% (28/256), p=0.003.

Conclusions

Staphylococcus aureus was predominant isolate followed by Klebsiella and Escherichia coli. There was high resistance to ampicillin and cloxacillin. Mortality rate due to neonatal sepsis was high in our setting. Routine antimicrobial surveillance should guide the choice of antibiotics for empirical treatment of neonatal sepsis.

Risk factors and prognosis for neonatal sepsis in southeastern Mexico: analysis of a four-year historic cohort follow-up

BACKGROUND

Neonatal sepsis is a worldwide public health issue in which, depending on the studied population, marked variations concerning its risk and prognostic factors have been reported. The aim of this study was to assess risk and prognostic factors for neonatal sepsis prevailing at a medical unit in southeastern Mexico. Thus, we used a historic cohort design to assess the association between a series of neonates and their mothers, in addition to hospital evolution features and the risk and prognosis of neonatal sepsis (defined by Pediatric Sepsis Consensus [PSC] criteria) in 11,790 newborns consecutively admitted to a Neonatology Service in Mérida, Mexico, between 2004 and 2007.

RESULTS

Sepsis was found in 514 of 11,790 (4.3 %) newborns; 387 of these cases were categorized as early-onset (<72 h) (75.3 %) and 127, as late-onset (>72 h) (24.7 %). After logistic regression, risk factors for sepsis included the following: low birth weight; prematurity; abnormal amniotic fluid; premature membrane rupture (PMR) at >24 h; respiratory complications, and the requirement of assisted ventilation, O(2) Inspiration fraction (IF) >60 %, or a surgical procedure. Some of these factors were differentially associated with early- or late-onset neonatal sepsis. The overall mortality rate of sepsis was 9.5 %. A marked difference in the mortality rate was found between early- and late-onset sepsis (p >0.0001). After Cox analysis, factors associated with mortality in newborns with sepsis comprised the following: prematurity; low birth weight; low Apgar score; perinatal asphyxia, and the requirement of any invasive medical or surgical procedure.

CONCLUSIONS

The incidence of neonatal sepsis in southeastern Mexico was 4.3 %. A different risk and prognostic profile between early- and late-onset neonatal sepsis was found.

Bacterial infections in Lilongwe, Malawi: aetiology and antibiotic resistance

Background

Life-threatening infections present major challenges for health systems in Malawi and the developing world because routine microbiologic culture and sensitivity testing are not performed due to lack of capacity. Use of empirical antimicrobial therapy without regular microbiologic surveillance is unable to provide adequate treatment in the face of emerging antimicrobial resistance. This study was conducted to determine antimicrobial susceptibility patterns in order to inform treatment choices and generate hospital-wide baseline data.

Methods

Culture and susceptibility testing was performed on various specimens from patients presenting with possible infectious diseases at Kamuzu Central Hospital, Lilongwe, Malawi.

Results

Between July 2006 and December 2007 3104 specimens from 2458 patients were evaluated, with 60.1% from the adult medical service. Common presentations were sepsis, meningitis, pneumonia and abscess. An etiologic agent was detected in 13% of patients. The most common organisms detected from blood cultures were Staphylococcus aureus, Escherichia coli, Salmonella species and Streptococcus pneumoniae, whereas Streptococcus pneumoniae and Cryptococcus neoformans were most frequently detected from cerebrospinal fluid. Haemophilus influenzae was rarely isolated. Resistance to commonly used antibiotics was observed in up to 80% of the isolates while antibiotics that were not commonly in use maintained susceptibility.

Conclusions

There is widespread resistance to almost all of the antibiotics that are empirically used in Malawi. Antibiotics that have not been widely introduced in Malawi show better laboratory performance. Choices for empirical therapy in Malawi should be revised accordingly. A microbiologic surveillance system should be established and prudent use of antimicrobials promoted to improve patient care.

High frequency of multidrug-resistant gram-negative rods in 2 neonatal intensive care units in the Philippines

BACKGROUND

Although hospital-acquired infections appear to be a growing threat to the survival of newborns in the developing world, the epidemiology of this problem remains poorly characterized.

METHODS

During a 10-month period, we conducted prospective longitudinal surveillance for colonization and bloodstream infection caused by gram-negative rods among all infants hospitalized in the 2 largest neonatal intensive care units in Manila, the Philippines. We determined antibiotic susceptibilities and calculated adjusted odds ratios for risk factors for bacteremia by means of multivariate logistic regression.

RESULTS

Of 1,831 neonates enrolled during a 10-month period, 1,017 (55.5%) became newly colonized and 358 (19.6%) became bacteremic with a drug-resistant gram-negative rod, most commonly Klebsiella species, Enterobacter species, Acinetobacter species, and Pseudomonas aeruginosa. Of the invasive isolates, 20% were resistant to imipenem, 41% to trimethoprim-sulfamethoxazole, 52% to amikacin, 63% to ampicillin-sulbactam, 67% to ceftazidime, and 80% to tobramycin. The factors significantly associated with an increased risk of bacteremia were mechanical ventilation and prematurity. Additionally, colonization with a drug-resistant gram-negative rod was an independent risk factor for bacteremia (odds ratio, 1.4 [95% confidence interval, 1.0-1.9]).

CONCLUSIONS

Colonization with a drug-resistant gram-negative rod was an independent risk factor for sepsis. If our data are typical, the unusually high intensity of colonization pressure and disease caused by multidrug-resistant gram-negative rods at these 2 neonatal intensive care units indicates an emerging healthcare crisis in the developing world. Improved infection control methods are therefore critically needed in developing countries.

Management of neonatal sepsis by Gram-negative pathogens

For the pediatrician and neonatologist who care for term and preterm infants, the challenge remains to keep these infants free of infection after delivery in special-care nurseries and neonatal intensive care units. Studies of complications associated with term infants at risk due to maternal factors, as well as preterm infants after early delivery, have demonstrated that sepsis is a major cause of neonatal mortality and morbidity. Infections due to Gram-negative organisms are increasingly being reported from neonatal units. Moreover, Gram-negative organisms that are multidrug resistant are on the increase and pose a formidable clinical challenge. In this article, we review current epidemiology, risk factors, clinical features, diagnosis, therapy and preventive measures related to Gram-negative infections in neonates.

Congenital and neonatal pneumonia

The greatest risk of death from pneumonia in childhood is in the neonatal period. It is estimated that pneumonia contributes to between 750000-1.2 million neonatal deaths annually, accounting for 10% of global child mortality. Congenital and neonatal pneumonias are often a difficult disease to identify and treat, with clinical manifestations often being non-specific. Many of the normal lung defences are compromised in the fetus and neonate, leading to an increased susceptibility to infection. The aetiology and epidemiology of congenital and neonatal pneumonias will depend on the clinical setting and population that the baby belongs to, the stage in the perinatal period, the gestational age of the baby and the definition of pneumonia. Diagnosis, treatment and prevention strategies are therefore also dependent on these factors, and will differ depending on the clinical setting. This review summarizes the current knowledge concerning congenital and neonatal pneumonia worldwide and discusses future directions in the prevention of the disease.

Young infant sepsis: aetiology, antibiotic susceptibility and clinical signs

Globally, young infant mortality comprises 40% of the estimated 10.8 million child deaths annually. Almost all (99%) of these deaths arise in low- and middle-income countries (LMICs). Achievement of the Millennium Development Goal for child survival, however, requires a significant improvement in the management of infections in young infants. We have reviewed current evidence from LMICs on one major cause of young infant mortality, severe infection, and have described the range of pathogens, reported antibiotic susceptibility and value of clinical signs in identifying severe bacterial illness. Evidence from the reviewed studies appears to show that common pathogens in young infant infections change over time and vary within and across settings. However, there are few good, large studies outside major urban settings and many reports describe infections of babies born in hospital when most young infant infections probably occur in the majority born at home. Yet what knowledge there is can aid in instituting prompt and appropriate therapy, and perhaps thus minimize the emergence of multidrug-resistant bacteraemia, a major threat at least in hospital settings. Improved country level data on pattern of microorganisms, resistance and antibiotic use are required to help reduce mortality through development of local, evidence-based clinical guidelines.

Extended-spectrum beta-lactamases: a clinical update

Extended-spectrum beta-lactamases (ESBLs) are a rapidly evolving group of beta-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. Typically, they derive from genes for TEM-1, TEM-2, or SHV-1 by mutations that alter the amino acid configuration around the active site of these beta-lactamases. This extends the spectrum of beta-lactam antibiotics susceptible to hydrolysis by these enzymes. An increasing number of ESBLs not of TEM or SHV lineage have recently been described. The presence of ESBLs carries tremendous clinical significance. The ESBLs are frequently plasmid encoded. Plasmids responsible for ESBL production frequently carry genes encoding resistance to other drug classes (for example, aminoglycosides). Therefore, antibiotic options in the treatment of ESBL-producing organisms are extremely limited. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBL-producing organisms may appear susceptible to some extended-spectrum cephalosporins. However, treatment with such antibiotics has been associated with high failure rates. There is substantial debate as to the optimal method to prevent this occurrence. It has been proposed that cephalosporin breakpoints for the Enterobacteriaceae should be altered so that the need for ESBL detection would be obviated. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in klebsiellae and Escherichia coli. In common to all ESBL detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic resistance mechanisms in the face of the introduction of new antimicrobial agents.

Invasive Gram-negative bacilli are frequently resistant to standard antibiotics for children admitted to hospital in Kilifi, Kenya

OBJECTIVES

To determine the pattern of resistance among Gram-negative bacilli causing invasive bacterial disease for the antibiotics that are already in common use in Kilifi, Kenya and for two potential alternatives, ciprofloxacin and cefotaxime. Also, to determine whether prevalence and severity of resistance was increasing over time, to identify patients who are particularly at risk of resistant infections, and to explore which factors are associated with the development of resistance in our setting.

METHODS

We used Etest to study antibiotic susceptibility patterns of 90 Gram-negative bacilli cultured in blood or CSF from paediatric inpatients over 8 years.

RESULTS

Susceptibility to amoxicillin 28%, cefotaxime 95% and ciprofloxacin 99% did not vary significantly with age. Susceptibilities for isolates from children aged less than 14 days were: chloramphenicol, 81%; trimethoprim/sulfamethoxazole, 71%; and gentamicin, 91%. From older children, susceptibilities were: chloramphenicol, 62%; trimethoprim/sulfamethoxazole, 39%; and gentamicin, 73%. Chloramphenicol susceptibility was significantly more common among non-typhi salmonellae than other species (79% versus 53%, P < 0.0005). The combination of gentamicin and chloramphenicol covered 91% of all isolates. The prevalence of resistance did not increase over time and was not more common in patients with HIV or malnutrition. Age was the only clinical feature that predicted resistance.

CONCLUSIONS

Gentamicin or chloramphenicol alone was suboptimal therapy for Gram-negative sepsis, although in this retrospective study, there was no association between resistance and mortality.

Neonatal pneumonia in developing countries

Pneumonia contributes to between 750,000 and 1.2 million neonatal deaths and an unknown number of stillbirths each year world wide. The aetiology depends on time of onset. Gram negative bacilli predominate in the first week of life, and Gram positive bacteria after that. Streptococcus pneumoniae probably causes about 25% of neonatal pneumonia. Interventions that would reduce mortality from this condition would have a large range of beneficial effects: improved maternal health, better management of other common neonatal conditions, and reduced long term childhood and adult morbidity.

Neonatal sepsis: an international perspective

Neonatal infections currently cause about 1.6 million deaths annually in developing countries. Sepsis and meningitis are responsible for most of these deaths. Resistance to commonly used antibiotics is emerging and constitutes an important problem world wide. To reduce global neonatal mortality, strategies of proven efficacy, such as hand washing, barrier nursing, restriction of antibiotic use, and rationalisation of admission to neonatal units, need to be implemented. Different approaches require further research.

Hospital-acquired neonatal infections in developing countries

Hospital-born babies in developing countries are at increased risk of neonatal infections because of poor intrapartum and postnatal infection-control practices. We reviewed data from developing countries on rates of neonatal infections among hospital-born babies, range of pathogens, antimicrobial resistance, and infection-control interventions. Reported rates of neonatal infections were 3-20 times higher than those reported for hospital-born babies in industrialised countries. Klebsiella pneumoniae, other gram-negative rods (Escherichia coli, Pseudomonas spp, Acinetobacter spp), and Staphylococcus aureus were the major pathogens among 11,471 bloodstream isolates reported. These infections can often present soon after birth. About 70% would not be covered by an empiric regimen of ampicillin and gentamicin, and many might be untreatable in resource-constrained environments. The associated morbidity, mortality, costs, and adverse effect on future health-seeking behaviour by communities pose barriers to improvement of neonatal outcomes in developing countries. Low-cost, "bundled" interventions using systems quality improvement approaches for improved infection control are possible, but should be supported by evidence in developing country settings.

Clinical microbiology of bacterial and fungal sepsis in very-low-birth-weight infants

Twenty percent of very-low-birth-weight (<1500 g) preterm infants experience a serious systemic infection, and despite advances in neonatal intensive care and antimicrobials, mortality is as much as threefold higher for these infants who develop sepsis than their counterparts without sepsis during their hospitalization. Outcomes may be improved by preventative strategies, earlier and accurate diagnosis, and adjunct therapies to combat infection and protect the vulnerable preterm infant during an infection. Earlier diagnosis on the basis of factors such as abnormal heart rate characteristics may offer the ability to initiate treatment prior to the onset of clinical symptoms. Molecular and adjunctive diagnostics may also aid in diagnosing invasive infection when clinical symptoms indicate infection but no organisms are isolated in culture. Due to the high morbidity and mortality, preventative and adjunctive therapies are needed. Prophylaxis has been effective in preventing early-onset group B streptococcal sepsis and late-onset Candida sepsis. Future research in prophylaxis using active and passive immunization strategies offers prevention without the risk of resistance to antimicrobials. Identification of the differences in neonatal intensive care units with low and high infection rates and implementation of infection control measures remain paramount in each neonatal intensive care unit caring for preterm infants.

Serious bacterial infections in newborn infants in developing countries

PURPOSE OF REVIEW

The overwhelming majority of the world's annual 4 million neonatal deaths occur in developing countries. This review therefore briefly addresses the burden, aetiology, prevention and management of serious neonatal bacterial infections in low-income settings.

RECENT FINDINGS

Bacterial infection is the biggest cause of neonatal admissions to hospitals, and probably the biggest cause of morbidity in the community, but its burden is unclear. The commonest serious infections involve bacteraemia, meningitis and respiratory infection, and case fatality rates may be as high as 45%. Key pathogens are Escherichia coli, Klebsiella species, Staphylococcus aureus and Streptococcus pyogenes. The incidence of neonatal infections with group B streptococcus is highly variable, as is the spectrum of antimicrobial resistance.

SUMMARY

Current areas of research include the rectification of micronutrient deficiencies, neonatal skin care, appropriate breastfeeding recommendations, cleansing of the birth canal, and simplified methods of diagnosis of infection. Operational activities include the control of neonatal tetanus, the diagnosis and treatment of sexually transmitted infections, integrated strategies for improving pregnancy, childbirth and neonatal survival, community-based management of acute respiratory infections, and community-based management of neonatal sepsis.

Combating antibiotic resistance

BACKGROUND

The ADA Council on Scientific Affairs developed this report to provide dental professionals with current information on antibiotic resistance and related considerations about the clinical use of antibiotics that are unique to the practice of dentistry.

OVERVIEW

This report addresses the association between the overuse of antibiotics and the development of resistant bacteria. The Council also presents a set of clinical guidelines that urges dentists to consider using narrow-spectrum antibacterial drugs in simple infections to minimize disturbance of the normal microflora, and to preserve the use of broad-spectrum drugs for more complex infections.

CONCLUSIONS AND PRACTICE IMPLICATIONS

The Council recommends the prudent and appropriate use of antibacterial drugs to prolong their efficacy and promotes reserving their use for the management of active infectious disease and the prevention of hematogenously spread infection, such as infective endocarditis or total joint infection, in high-risk patients.

Clinical predictors of bloodstream infections and mortality in hospitalized Malawian children

BACKGROUND

In sub-Saharan Africa, bloodstream infections (BSI) are a major cause of pediatric mortality. Because of limited resources and facilities in these developing countries, treatment often must be based solely on clinical observations and patient history and includes the use of broad spectrum antimicrobials, a factor in the emergence of antibiotic resistance.

METHODS

During July 28 through August 18, 1998 we analyzed clinical, epidemiologic and microbiologic data from a cohort of 225 hospitalized children in Malawi, Africa, to determine clinical indices associated with the presence/absence of BSI and/or mortality for use in settings with minimal microbiologic laboratory and intensive care facilities.

RESULTS

BSI (n = 35 children) were associated with malnutrition, chronic cough, lethargy by history, lethargy on examination and oral thrush; 92% of children without these symptoms were BSI-negative. Mortality (21 of 173 children with known mortality status) was associated with malnutrition, lethargy on examination, prior receipt of antimalarials and acute decreased feeding. Of those with > or =2 of these indices 69% died; of those with <2 of the indices 94% survived. Infection with human immunodeficiency virus was not significantly related to either BSI or mortality status.

CONCLUSIONS

Malnutrition, but not HIV, was strongly related to both BSI and mortality. Assessment of these BSI and mortality indices at hospital admission provides rapid, cost-free indication of which children are most/least in need of empiric antimicrobial therapy or intensive observation, thereby maximizing appropriate use of antimicrobials and limited facilities while minimizing inappropriate antimicrobial usage.

Molecular epidemiology of antibiotic-resistant gram-negative bacilli in a neonatal intensive care unit during a nonoutbreak period

OBJECTIVE

Gram-negative organisms that are resistant to parenteral antibiotics are a growing threat to hospitalized patients. This study was conducted to define the epidemiologic characteristics of these organisms during a nonoutbreak period in a neonatal intensive care unit (NICU).

METHODS

Nasopharyngeal and rectal swab specimens were obtained 3 times a week from every infant in a tertiary care NICU during a 12-month period. Specimens were processed to identify aerobic Gram-negative species resistant to gentamicin, piperacillin-tazobactam, or ceftazidime. Selected clinical parameters were tested for their association with colonization with a resistant organism. Restriction endonuclease digests of genomic DNA were derived from isolates of the most frequently occurring species. The fragments were analyzed by pulsed-field gel electrophoresis (PFGE) to determine the genetic relatedness of the various isolates and thereby determine the length of colonization, the frequency of horizontal transmission, and the size and duration of clusters.

RESULTS

A total of 101 infants (8.6%) of 1180 admissions were colonized with at least 1 antibiotic-resistant bacillus before NICU discharge. Multiple parameters indicating a prolonged, complicated NICU course were associated with resistant colonization, including gestational age, length of stay, and exposure to several classes of antibiotics. Colonization with resistant bacilli occurred as early as the first NICU day, but acquisition continued throughout the infants' stay. A total of 436 isolates were analyzed by PFGE. On the basis of this molecular analysis, it was determined that duration of colonization was usually very short; the median for all species tested was <1 week. In addition, cross-colonization occurred in only 12% of all PFGE-analyzed isolates. Most clusters of cross-colonized infants were small, with the majority involving only 2 patients.

CONCLUSIONS

During endemic periods, acquisition of antibiotic-resistant Gram-negative bacilli in the NICU may occur very soon after admission, but colonization continues over many weeks of NICU stay. The duration of colonization with resistant bacilli is short, and horizontal transmission is unusual. These characteristics suggest a gradual but temporary incorporation of these organisms from the NICU environment into the nascent newborn microflora over time with little cross-colonization. These observations may aid the rational development of infection-control strategies to contain the reservoir of resistant Gram-negative organisms in the NICU.antibiotic resistance, Gram-negative bacilli, neonatal intensive care, antibiotic utilization, colonization, pulsed-field gel electrophoresis.

Molecular characterization of a novel plasmid-encoded cefotaximase (CTX-M-12) found in clinical Klebsiella pneumoniae isolates from Kenya

Nine Klebsiella pneumoniae isolates, six from blood and three from cerebrospinal fluid of newborn babies at Kenyatta National Hospital, Nairobi, Kenya, were analyzed for the mechanism of cephalosporin resistance. By using pulsed-field gel electrophoresis of XbaI-digested chromosomal DNA, all the nine isolates were found to be clonal. PCR and direct sequencing revealed a novel extended-spectrum beta-lactamase, which we designated CTX-M-12. It has a more potent hydrolytic activity against cefotaxime than against ceftazidime and a pI of 9.0 and is encoded on a large self-transferable ca. 160-kbp plasmid.