High Prevalence of Vaccine-Type Infections Among Children with Pneumococcal Pneumonia and Effusion After 13-Valent Pneumococcal Conjugate Vaccine Introduction in the Dominican Republic.

BACKGROUND: In 2013, the Dominican Republic introduced 13-valent pneumococcal conjugate vaccine (PCV13) using a 3-dose schedule (at 2, 4 and 12 months of age). We evaluated the impact of PCV13 on serotypes causing pneumococcal pneumonia with pleural effusion. METHODS: Surveillance data after PCV13 introduction (July 2014 to June 2016) were compared with data before PCV13 introduction (July 2009 to June 2011). Cases were defined as radiologic evidence of pneumonia with pleural effusion in a child aged <15 years. Pneumococcus was detected in pleural fluid by either culture or polymerase chain reaction, and serotyping was performed. The Ministry of Health's PCV13 uptake data for 2014-2016 were obtained. RESULTS: The prevalence of pneumococcus among cases was similar before and after PCV13 introduction (56.4% and 52.8%, respectively). The proportion of pneumococcal cases caused by vaccine serotypes was 86% for children <2 years old both before and PCV13 introduction. Compared with before PCV13, serotype 14 accounted for a smaller (28% vs 13%, respectively; P = .02) and serotype 1 for a larger (23% vs 37%; P = .09) proportion of pneumococcal cases after PCV13 introduction. National uptake for the first, second, and third PCV13 doses was 94%, 81%, and 28%, respectively, in 2014 and 75%, 61%, and 26% in 2015. DISCUSSION: While the decrease in pneumococcal pneumonia with pleural effusion caused by serotype 14 may reflect an early effect of PCV13 implementation, other vaccine serotypes, including serotype 1, are not well controlled. Better PCV13 coverage for all 3 doses is needed.

Effectiveness of the Pfizer-BioNTech COVID-19 Vaccine Among Residents of Two Skilled Nursing Facilities Experiencing COVID-19 Outbreaks - Connecticut, December 2020-February 2021.

Residents of long-term care facilities (LTCFs), particularly those in skilled nursing facilities (SNFs), have experienced disproportionately high levels of COVID-19-associated morbidity and mortality and were prioritized for early COVID-19 vaccination (1,2). However, this group was not included in COVID-19 vaccine clinical trials, and limited postauthorization vaccine effectiveness (VE) data are available for this critical population (3). It is not known how well COVID-19 vaccines protect SNF residents, who typically are more medically frail, are older, and have more underlying medical conditions than the general population (1). In addition, immunogenicity of the Pfizer-BioNTech vaccine was found to be lower in adults aged 65-85 years than in younger adults (4). Through the CDC Pharmacy Partnership for Long-Term Care Program, SNF residents and staff members in Connecticut began receiving the Pfizer-BioNTech COVID-19 vaccine on December 18, 2020 (5). Administration of the vaccine was conducted during several on-site pharmacy clinics. In late January 2021, the Connecticut Department of Public Health (CT DPH) identified two SNFs experiencing COVID-19 outbreaks among residents and staff members that occurred after each facility's first vaccination clinic. CT DPH, in partnership with CDC, performed electronic chart review in these facilities to obtain information on resident vaccination status and infection with SARS-CoV-2, the virus that causes COVID-19. Partial vaccination, defined as the period from >14 days after the first dose through 7 days after the second dose, had an estimated effectiveness of 63% (95% confidence interval [CI] = 33%-79%) against SARS-CoV-2 infection (regardless of symptoms) among residents within these SNFs. This is similar to estimated effectiveness for a single dose of the Pfizer-BioNTech COVID-19 vaccine in adults across a range of age groups in noncongregate settings (6) and suggests that to optimize vaccine impact among this population, high coverage with the complete 2-dose series should be recommended for SNF residents and staff members.

Regional Emergence of Candida auris in Chicago and Lessons Learned From Intensive Follow-up at 1 Ventilator-Capable Skilled Nursing Facility.

BACKGROUND: Since the identification of the first 2 Candida auris cases in Chicago, Illinois, in 2016, ongoing spread has been documented in the Chicago area. We describe C. auris emergence in high-acuity, long-term healthcare facilities and present a case study of public health response to C. auris and carbapenemase-producing organisms (CPOs) at one ventilator-capable skilled nursing facility (vSNF-A). METHODS: We performed point prevalence surveys (PPSs) to identify patients colonized with C. auris and infection-control (IC) assessments and provided ongoing support for IC improvements in Illinois acute- and long-term care facilities during August 2016-December 2018. During 2018, we initiated a focused effort at vSNF-A and conducted 7 C. auris PPSs; during 4 PPSs, we also performed CPO screening and environmental sampling. RESULTS: During August 2016-December 2018 in Illinois, 490 individuals were found to be colonized or infected with C. auris. PPSs identified the highest prevalence of C. auris colonization in vSNF settings (prevalence, 23-71%). IC assessments in multiple vSNFs identified common challenges in core IC practices. Repeat PPSs at vSNF-A in 2018 identified increasing C. auris prevalence from 43% to 71%. Most residents screened during multiple PPSs remained persistently colonized with C. auris. Among 191 environmental samples collected, 39% were positive for C. auris, including samples from bedrails, windowsills, and shared patient-care items. CONCLUSIONS: High burden in vSNFs along with persistent colonization of residents and environmental contamination point to the need for prioritizing IC interventions to control the spread of C. auris and CPOs.

Declines in Pneumonia and Meningitis Hospitalizations in Children Under 5 Years of Age After Introduction of 10-Valent Pneumococcal Conjugate Vaccine in Zambia, 2010-2016.

BACKGROUND: Pneumococcus is a leading cause of pneumonia and meningitis. Zambia introduced a 10-valent pneumococcal conjugate vaccine (PCV10) in July 2013 using a 3-dose primary series at ages 6, 10, and 14 weeks with no booster. We evaluated the impact of PCV10 on meningitis and pneumonia hospitalizations. METHODS: Using hospitalization data from first-level care hospitals, available at the Ministry of Health, and from the largest pediatric referral hospital in Lusaka, we identified children aged <5 years who were hospitalized with pneumonia or meningitis from January 2010-December 2016. We used time-series analyses to measure the effect of PCV10 on monthly case counts by outcome and age group (<1 year, 1-4 years), accounting for seasonality. We defined the pre- and post-PCV10 periods as January 2010-June 2013 and July 2014-December 2016, respectively. RESULTS: At first-level care hospitals, pneumonia and meningitis hospitalizations among children aged <5 years accounted for 108 884 and 1742 admissions in the 42 months pre-PCV10, respectively, and 44 715 and 646 admissions in the 30 months post-PCV10, respectively. Pneumonia hospitalizations declined by 37.8% (95% confidence interval [CI] 21.4-50.3%) and 28.8% (95% CI 17.7-38.7%) among children aged <1 year and 1-4 years, respectively, while meningitis hospitalizations declined by 72.1% (95% CI 63.2-79.0%) and 61.6% (95% CI 50.4-70.8%), respectively, in these age groups. In contrast, at the referral hospital, pneumonia hospitalizations remained stable and a smaller but significant decline in meningitis was observed among children aged 1-4 years (39.3%, 95% CI 16.2-57.5%). CONCLUSIONS: PCV10 introduction was associated with declines in meningitis and pneumonia hospitalizations in Zambia, especially in first-level care hospitals.

Pediatric Bacterial Meningitis Surveillance in the World Health Organization African Region Using the Invasive Bacterial Vaccine-Preventable Disease Surveillance Network, 2011-2016.

BACKGROUND: Bacterial meningitis is a major cause of morbidity and mortality in sub-Saharan Africa. We analyzed data from the World Health Organization's (WHO) Invasive Bacterial Vaccine-preventable Diseases Surveillance Network (2011-2016) to describe the epidemiology of laboratory-confirmed Streptococcus pneumoniae (Spn), Neisseria meningitidis, and Haemophilus influenzae meningitis within the WHO African Region. We also evaluated declines in vaccine-type pneumococcal meningitis following pneumococcal conjugate vaccine (PCV) introduction. METHODS: Reports of meningitis in children <5 years old from sentinel surveillance hospitals in 26 countries were classified as suspected, probable, or confirmed. Confirmed meningitis cases were analyzed by age group and subregion (South-East and West-Central). We described case fatality ratios (CFRs), pathogen distribution, and annual changes in serotype and serogroup, including changes in vaccine-type Spn meningitis following PCV introduction. RESULTS: Among 49 844 reported meningitis cases, 1670 (3.3%) were laboratory-confirmed. Spn (1007/1670 [60.3%]) was the most commonly detected pathogen; vaccine-type Spn meningitis cases declined over time. CFR was the highest for Spn meningitis: 12.9% (46/357) in the South-East subregion and 30.9% (89/288) in the West-Central subregion. Meningitis caused by N. meningitidis was more common in West-Central than South-East Africa (321/954 [33.6%] vs 110/716 [15.4%]; P < .0001). Haemophilus influenzae (232/1670 [13.9%]) was the least prevalent organism. CONCLUSIONS: Spn was the most common cause of pediatric bacterial meningitis in the African region even after reported cases declined following PCV introduction. Sustaining robust surveillance is essential to monitor changes in pathogen distribution and to inform and guide vaccination policies.

Multicenter Outbreak of Gram-Negative Bloodstream Infections in Hemodialysis Patients.

RATIONALE & OBJECTIVE: Contaminated water and other fluids are increasingly recognized to be associated with health care-associated infections. We investigated an outbreak of Gram-negative bloodstream infections at 3 outpatient hemodialysis facilities. STUDY DESIGN: Matched case-control investigations. SETTING & PARTICIPANTS: Patients who received hemodialysis at Facility A, B, or C from July 2015 to November 2016. EXPOSURES: Infection control practices, sources of water, dialyzer reuse, injection medication handling, dialysis circuit priming, water and dialysate test findings, environmental reservoirs such as wall boxes, vascular access care practices, pulsed-field gel electrophoresis, and whole-genome sequencing of bacterial isolates. OUTCOMES: Cases were defined by a positive blood culture for any Gram-negative bacteria drawn July 1, 2015 to November 30, 2016 from a patient who had received hemodialysis at Facility A, B, or C. ANALYTICAL APPROACH: Exposures in cases and controls were compared using matched univariate conditional logistic regression. RESULTS: 58 cases of Gram-negative bloodstream infection occurred; 48 (83%) required hospitalization. The predominant organisms were Serratia marcescens (n=21) and Pseudomonas aeruginosa (n=12). Compared with controls, cases had higher odds of using a central venous catheter for dialysis (matched odds ratio, 54.32; lower bound of the 95% CI, 12.19). Facility staff reported pooling and regurgitation of waste fluid at recessed wall boxes that house connections for dialysate components and the effluent drain within dialysis treatment stations. Environmental samples yielded S marcescens and P aeruginosa from wall boxes. S marcescens isolated from wall boxes and case-patients from the same facilities were closely related by pulsed-field gel electrophoresis and whole-genome sequencing. We identified opportunities for health care workers' hands to contaminate central venous catheters with contaminated fluid from the wall boxes. LIMITATIONS: Limited patient isolates for testing, on-site investigation occurred after peak of infections. CONCLUSIONS: This large outbreak was linked to wall boxes, a previously undescribed source of contaminated fluid and biofilms in the immediate patient care environment.

Vital Signs: Health Care-Associated Legionnaires' Disease Surveillance Data from 20 States and a Large Metropolitan Area - United States, 2015.

BACKGROUND: Legionnaires' disease, a severe pneumonia, is typically acquired through inhalation of aerosolized water containing Legionella bacteria. Legionella can grow in the complex water systems of buildings, including health care facilities. Effective water management programs could prevent the growth of Legionella in building water systems. METHODS: Using national surveillance data, Legionnaires' disease cases were characterized from the 21 jurisdictions (20 U.S. states and one large metropolitan area) that reported exposure information for ≥90% of 2015 Legionella infections. An assessment of whether cases were health care-associated was completed; definite health care association was defined as hospitalization or long-term care facility residence for the entire 10 days preceding symptom onset, and possible association was defined as any exposure to a health care facility for a portion of the 10 days preceding symptom onset. All other Legionnaires' disease cases were considered unrelated to health care. RESULTS: A total of 2,809 confirmed Legionnaires' disease cases were reported from the 21 jurisdictions, including 85 (3%) definite and 468 (17%) possible health care-associated cases. Among the 21 jurisdictions, 16 (76%) reported 1-21 definite health care-associated cases per jurisdiction. Among definite health care-associated cases, the majority (75, 88%) occurred in persons aged ≥60 years, and exposures occurred at 72 facilities (15 hospitals and 57 long-term care facilities). The case fatality rate was 25% for definite and 10% for possible health care-associated Legionnaires' disease. CONCLUSIONS AND IMPLICATIONS FOR PUBLIC HEALTH PRACTICE: Exposure to Legionella from health care facility water systems can result in Legionnaires' disease. The high case fatality rate of health care-associated Legionnaires' disease highlights the importance of case prevention and response activities, including implementation of effective water management programs and timely case identification.

Rare and emerging viral infections in transplant recipients.

Emerging viral pathogens include newly discovered viruses as well as previously known viruses that are either increasing, or threatening to increase in incidence. While often first identified in the general population, they may affect transplant recipients, in whom their manifestations may be atypical or more severe. Enhanced molecular methods have increased the rate of viral discovery but have not overcome the problem of demonstrating pathogenicity. At the same time, improved clinical diagnostic methods have increased the detection of reemerging viruses in immunocompromised patients. In this review, we first discuss viral diagnostics and the developing field of viral discovery and then focus on rare and emerging viruses in the transplant population: human T-cell leukemia virus type 1; hepatitis E virus; bocavirus; KI and WU polyomaviruses; coronaviruses HKU1 and NL63; influenza, H1N1; measles; dengue; rabies; and lymphocytic choriomeningitis virus. Detection and reporting of such rare pathogens in transplant recipients is critical to patient care and improving our understanding of posttransplant infections.

Distinctive Features of Ertapenem-Mono-Resistant Carbapenem-Resistant Enterobacterales in the United States: A Cohort Study.

BACKGROUND: Carbapenem-resistant Enterobacterales (CRE) are highly antibiotic-resistant bacteria. Whether CRE resistant only to ertapenem among carbapenems (ertapenem "mono-resistant") represent a unique CRE subset with regards to risk factors, carbapenemase genes, and outcomes is unknown. METHODS: We analyzed surveillance data from 9 CDC Emerging Infections Program (EIP) sites. A case was the first isolation of a carbapenem-resistant Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, K. oxytoca, K. pneumoniae, or K. variicola from a normally sterile site or urine in an EIP catchment area resident in 2016-2017. We compared risk factors, carbapenemase genes, antibiotic susceptibility, and mortality of ertapenem "mono-resistant" cases to "other" CRE cases (resistant to ≥1 carbapenem other than ertapenem) and analyzed risk factors for mortality. RESULTS: Of 2009 cases, 1249 (62.2%) were ertapenem-mono-resistant and 760 (37.8%) were other CRE. Ertapenem-mono-resistant CRE cases were more frequently ≥80 years old (29.1% vs 19.5%; P < .0001) and female (67.9% vs 59.0%; P < .0001). Ertapenem-mono-resistant isolates were more likely to be Enterobacter cloacae complex (48.4% vs 15.4%; P < .0001) but less likely to be isolated from a normally sterile site (7.1% vs 11.7%; P < .01) or to have a carbapenemase gene (2.4% vs 47.4%; P < .0001). Ertapenem-mono-resistance was not associated with 90-day mortality in logistic regression models. Carbapenemase-positive isolates were associated with mortality (odds ratio, 1.93; 95% CI, 1.30-2.86). CONCLUSIONS: Ertapenem-mono-resistant CRE rarely have carbapenemase genes and have distinct clinical and microbiologic characteristics from other CRE. These findings may inform antibiotic choice and infection prevention practices, particularly when carbapenemase testing is not available.

Safety and tolerability of antiretrovirals during pregnancy.

Combination antiretroviral therapy (CART) dramatically decreases mother-to-child HIV-1 transmission (MTCT), but maternal adverse events are not infrequent. A review of 117 locally followed pregnancies revealed 7 grade ≥ 3 AEs possibly related to antiretrovirals, including 2 hematologic, 3 hepatic, and 2 obstetric cholestasis cases. A fetal demise was attributed to obstetric cholestasis, but no maternal deaths occurred. The drugs possibly associated with these AE were zidovudine, nelfinavir, lopinavir/ritonavir, and indinavir. AE or intolerability required discontinuation/substitution of nevirapine in 16% of the users, zidovudine in 10%, nelfinavir in 9%, lopinavir/ritonavir in 1%, but epivir and stavudine in none. In conclusion, nevirapine, zidovudine, and nelfinavir had the highest frequency of AE and/or the lowest tolerability during pregnancy. Although nevirapine and nelfinavir are infrequently used in pregnancy at present, zidovudine is included in most MTCT preventative regimens. Our data emphasize the need to revise the treatment recommendations for pregnant women to include safer and better-tolerated drugs.

Gaps in infection prevention practices for catheter-associated urinary tract infections and central line-associated bloodstream infections as identified by the Targeted Assessment for Prevention Strategy.

BACKGROUND: Catheter-associated urinary tract infections (CAUTI) and central line-associated bloodstream infections (CLABSI) represent a substantial portion of health care-associated infections (HAIs) reported in the United States. The Targeted Assessment for Prevention Strategy is a quality improvement framework to reduce health care-associated infections. Data from the Targeted Assessment for Prevention Facility Assessments were used to determine common infection prevention gaps for CAUTI and CLABSI. METHODS: Data from 2,044 CAUTI and 1,680 CLABSI assessments were included in the analysis. Items were defined as potential gaps if ≥33% respondents answered Unknown, ≥33% No, or ≥50% No or Unknown or Never, Rarely, Sometimes, or Unknown to questions pertaining to those areas. Review of response frequencies and stratification by respondent role were performed to highlight opportunities for improvement. RESULTS: Across CAUTI and CLABSI assessments, lack of physician champions (<35% Yes) and nurse champions (<55% Yes), along with lack of awareness of competency assessments, audits, and feedback were reported. Lack of practices to facilitate timely removal of urinary catheters were identified for CAUTI and issues with select device insertion practices, such as maintaining aseptic technique, were perceived as areas for improvement for CLABSI. CONCLUSIONS: These data suggest common gaps in critical components of infection prevention and control programs. The identification of these gaps has the potential to inform targeted CAUTI and CLABSI prevention efforts.

Clinical Course of SARS-CoV-2 Infection in Adults with ESKD Receiving Outpatient Hemodialysis.

Background: Patients with ESKD on maintenance dialysis receive dialysis in common spaces with other patients and have a higher risk of severe SARS-CoV-2 infections. They may have persistently or intermittently positive SARS-CoV-2 RT-PCR tests after infection. We describe the clinical course of SARS-CoV-2 infection and the serologic response in a convenience sample of patients with ESKD to understand the duration of infectivity. Methods: From August to November 2020, we enrolled patients on maintenance dialysis with SARS-CoV-2 infections from outpatient dialysis facilities in Atlanta, Georgia. We followed participants for approximately 42 days. We assessed COVID-19 symptoms and collected specimens. Oropharyngeal (OP), anterior nasal (AN), and saliva (SA) specimens were tested for the presence of SARS-CoV-2 RNA, using RT-PCR, and sent for viral culture. Serology, including neutralizing antibodies, was measured in blood specimens. Results: Fifteen participants, with a median age of 58 (range, 37‒77) years, were enrolled. Median duration of RT-PCR positivity from diagnosis was 18 days (interquartile range [IQR], 8‒24 days). Ten participants had at least one, for a total of 41, positive RT-PCR specimens ≥10 days after symptoms onset. Of these 41 specimens, 21 underwent viral culture; one (5%) was positive 14 days after symptom onset. Thirteen participants developed SARS-CoV-2-specific antibodies, 11 of which included neutralizing antibodies. RT-PCRs remained positive after seroconversion in eight participants and after detection of neutralizing antibodies in four participants; however, all of these samples were culture negative. Conclusions: Patients with ESKD on maintenance dialysis remained persistently and intermittently SARS-CoV-2-RT-PCR positive. However, of the 15 participants, only one had infectious virus, on day 14 after symptom onset. Most participants mounted an antibody response, including neutralizing antibodies. Participants continued having RT-PCR-positive results in the presence of SARS-CoV-2-specific antibodies, but without replication-competent virus detected.

Pneumonia Hospitalization Coding Changes Associated With Transition From the 9th to 10th Revision of International Classification of Diseases.

OBJECTIVES: To evaluate the impact of International Classification of Disease, 10th revision, Clinical Modification (ICD-10-CM) implementation on pneumonia hospitalizations rates, which had declined following pneumococcal conjugate vaccine introduction for infants in 2000. METHODS: We randomly selected records from a single hospital 1 year before (n = 500) and after (n = 500) October 2015 implementation of ICD-10-CM coding. We used a validated ICD-9-CM algorithm and translation of that algorithm to ICD-10-CM to identify pneumonia hospitalizations pre- and post-implementation, respectively. We recoded ICD-10-CM records to ICD-9-CM and vice versa. We calculated sensitivity and positive predictive value (PPV) of the ICD-10-CM algorithm using ICD-9-CM coding as the reference. We used sensitivity and PPV values to calculate an adjustment factor to apply to ICD-10 era rates to enable comparison with ICD-9-CM rates. We reviewed primary diagnoses of charts not meeting the pneumonia definition when recoded. RESULTS: Sensitivity and PPV of the ICD-10-CM algorithm were 94% and 92%, respectively, for young children and 74% and 79% for older adults. The estimated adjustment factor for ICD-10-CM period rates was -2.09% (95% credible region [CR], -7.71% to +3.0%) for children and +6.76% (95% CR, -3.06% to +16.7%) for older adults. We identified a change in coding adult charts that met the ICD-9-CM pneumonia definition that led to recoding in ICD-10-CM as chronic obstructive pulmonary disease (COPD) exacerbation. CONCLUSIONS: The ICD-10-CM algorithm derived from a validated ICD-9-CM algorithm should not introduce substantial bias for evaluating pneumonia trends in children. However, changes in coding of pneumonia associated with COPD in adults warrant further study.

Kinetics and determining factors of the virologic response to antiretrovirals during pregnancy.

HIV-infected pregnant women with undetectable plasma HIV RNA concentrations at delivery pose a minimal risk of vertical transmission. We studied the kinetics and the determinants of the virologic response to antiretroviral therapy in 117 consecutive pregnancies. Patients who initiated therapy during pregnancy had a VL decrease of 2 and 2.5 log(10) after 4 and 24 weeks, respectively. Therapeutic drug monitoring (TDM) of the protease inhibitors administered in doses recommended for nonpregnant adults resulted in below-target concentrations in 29%, 35%, and 44% of 1st, 2nd, and 3rd trimester measurements, respectively, but low drug concentrations did not correlate with virologic failure. Demographic characteristics, antiretroviral experience prior to pregnancy, baseline VL, or use of specific antiretrovirals did not affect the virologic response. Adherence to >/=95% of prescribed doses and utilization of psychosocial services were associated with undetectable plasma HIV RNA at delivery. In conclusion, the virologic responses of pregnant and nonpregnant adults share similar characteristics.

Molecular Detection of Leptospira in Two Returned Travelers: Higher Bacterial Load in Cerebrospinal Fluid Versus Serum or Plasma.

Leptospirosis is a potentially severe illness in returned travelers. Patients often present with fever, headache, and neck pain, which may lead to a workup for meningitis including the acquisition of cerebrospinal fluid (CSF). Although Leptospira DNA has been detected in CSF by polymerase chain reaction (PCR), little data exist regarding the utility of testing CSF in addition to serum or plasma obtained on presentation. In this report, we present two cases of leptospirosis in returned travelers presenting with fever and headache. Our first patient had neutrophilic meningitis, and Leptospira was detectable only in CSF obtained on admission. The second patient had a normal CSF profile, but Leptospira was detected in CSF at a bacterial load 5- to 10-fold higher than that in plasma. CSF is an important specimen for the diagnosis of Leptospira by molecular methods and may yield an actionable diagnosis in the absence of leptospiremia.

Resistance to antiretrovirals in HIV-infected pregnant women.

BACKGROUND: Antiretrovirals suppress HIV replication and prevent mother-to-child-transmission of HIV (PMTCT). Resistance to antiretrovirals may reduce the efficacy of PMTCT and/or complicate treatment of maternal or infant infection. OBJECTIVES: To assess resistance to antiretrovirals during pregnancy. DESIGN: Retrospective chart review of 44 pregnancies. RESULTS: Twenty-two patients were antiretroviral treatment-naïve, 8 were on therapy, and 14 had prior therapy, but were off medication when the genotyping was performed. Major mutations were found in 10 antiretroviral-experienced women, including 5 women with major mutations to 2 classes of drugs (none to 3 classes). Major mutations were most common for lamivudine, nevirapine, zidovudine, stavudine, and abacavir. Three women had significant resistance to zidovudine/lamivudine, a combination recommended in PMTCT guidelines. Despite significant antiretroviral resistance, 6 of 8 women with plasma HIV RNA measured within 4 weeks of delivery achieved <50 copies/mL. All neonates were uninfected. Among 6 women who received antiretrovirals exclusively for PMTCT, there were no remarkable changes of the HIV genotype before and after pregnancy. CONCLUSIONS: Resistance to antiretrovirals was common in antiretroviral-experienced pregnant women, but not in naïve women. The 14% prevalence of resistance to zidovudine and lamivudine in antiretroviral-experienced women suggests that alternative NRTI are desirable for this group of patients.